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Rocket engine

2024-08-17T16:48:30Z

88.163.124.35: /* Combustion instabilities */

{{Short description|Non-air breathing jet engine used to propel a missile or vehicle}}
{{Use British English|date=February 2019}}
[[File:RS-68 rocket engine test.jpg|thumb|right|[[RS-68]] being tested at NASA's [[Stennis Space Center]]]]
[[File:Viking 5C rocketengine.jpg|thumb|right|[[Viking (rocket engine)|Viking 5C rocket engine]] used on [[Ariane 1]] through [[Ariane 4]]]]

A '''rocket engine''' uses stored [[rocket propellant]]s as the [[reaction mass]] for forming a high-speed propulsive [[Jet (fluid)|jet]] of fluid, usually high-temperature gas. [[Rocket]] engines are [[reaction engine]]s, producing thrust by ejecting mass rearward, in accordance with [[Newton's third law]]. Most rocket engines use the [[combustion]] of reactive chemicals to supply the necessary energy, but non-combusting forms such as [[cold gas thruster]]s and [[nuclear thermal rocket]]s also exist. Vehicles propelled by rocket engines are commonly used by [[ballistic missiles]] (they normally use [[solid fuel]]) and [[rocket]]s. Rocket vehicles carry their own [[oxidiser]], unlike most combustion engines, so rocket engines can be used in a [[vacuum]] to propel [[spacecraft]] and [[ballistic missile]]s.

Compared to other types of jet engine, rocket engines are the lightest and have the highest thrust, but are the least propellant-efficient (they have the lowest [[specific impulse]]). The ideal exhaust is [[hydrogen]], the lightest of all elements, but chemical rockets produce a mix of heavier species, reducing the exhaust velocity.

Rocket engines become more efficient at high speeds, due to the [[Oberth effect]].<ref name=ways>{{cite web|url=https://archive.org/details/nasa_techdoc_19720008133|title=Ways to spaceflight|volume=NASA TT F-622|others=Translation of the German language original "Wege zur Raumschiffahrt," (1920)|location=Tunis, Tunisia|year=1970|author=Hermann Oberth|publisher=Agence Tunisienne de Public-Relations}}</ref>

==Terminology==
Here, "rocket" is used as an abbreviation for "rocket engine".

'''[[Thermal rocket]]s''' use an inert propellant, heated by electricity ([[electrothermal propulsion]]) or a nuclear reactor ([[nuclear thermal rocket]]).

'''Chemical rockets''' are powered by [[exothermic]] [[redox chemistry|reduction-oxidation]] chemical reactions of the propellant:

*'''[[Solid-fuel rocket]]s''' (or '''solid-propellant rockets''' or '''motors''') are chemical rockets which use propellant in a [[solid|solid state]].
*'''[[Liquid-propellant rocket]]s''' use one or more propellants in a [[liquid state]] fed from tanks.
*'''[[Hybrid rocket]]s''' use a solid propellant in the combustion chamber, to which a second liquid or gas [[oxidizing agent|oxidiser]] or propellant is added to permit combustion.
*'''[[Monopropellant rocket]]s''' use a single propellant decomposed by a [[catalyst]]. The most common monopropellants are [[hydrazine]] and [[hydrogen peroxide]].

==Principle of operation==
[[File:Liquid-Fuel Rocket Diagram.svg|thumb|upright=1.25|Simplified diagram of a liquid-fuel rocket: {{olist |
|[[Liquid rocket propellant|Liquid fuel]] tank
|[[Oxidizing agent|Liquid oxidiser]] tank
|Pumps feed fuel and oxidiser under high pressure.
|[[Combustion chamber]] mixes and burns the propellants.
|[[Propelling nozzle|Exhaust nozzle]] expands and accelerates the gas jet to produce thrust.
|Exhaust exits nozzle.
}}]]

[[File:Solid-Fuel Rocket Diagram.svg|thumb|upright=1.25|Simplified diagram of a solid-fuel rocket: {{olist
|Solid [[Rocket propellant#Solid chemical propellants|fuel–oxidiser mixture]] (propellant) packed into casing
|[[Pyrotechnic initiator|Igniter]] initiates propellant combustion.
|Central hole in propellant acts as the [[combustion chamber]].
|[[Propelling nozzle|Exhaust nozzle]] expands and accelerates the gas jet to produce thrust.
|Exhaust exits nozzle.
}}]]
Rocket engines produce thrust by the expulsion of an exhaust [[fluid]] that has been accelerated to high speed through a [[propelling nozzle]]. The fluid is usually a gas created by high pressure ({{convert|10|to|300|bar|psi|order=flip|adj=on}}) combustion of solid or liquid [[Rocket propellant|propellants]], consisting of [[fuel]] and [[oxidizing agent|oxidiser]] components, within a [[combustion chamber]]. As the gases expand through the nozzle, they are accelerated to very high ([[supersonic]]) speed, and the reaction to this pushes the engine in the opposite direction. Combustion is most frequently used for practical rockets, as the laws of [[thermodynamics]] (specifically [[Carnot's theorem (thermodynamics)|Carnot's theorem]]) dictate that high temperatures and pressures are desirable for the best [[thermal efficiency]]. [[Nuclear thermal rocket]]s are capable of higher efficiencies, but currently have [[Nuclear thermal rocket#Risks|environmental problems]] which preclude their routine use in the Earth's atmosphere and [[cislunar space]].

For [[model rocket]]ry, an available alternative to combustion is the [[water rocket]] pressurized by compressed air, [[carbon dioxide]], [[nitrogen]], or any other readily available, inert gas.

===Propellant===
Rocket propellant is mass that is stored, usually in some form of tank, or within the combustion chamber itself, prior to being ejected from a rocket engine in the form of a fluid jet to produce thrust.

Chemical rocket propellants are the most commonly used. These undergo exothermic chemical reactions producing a hot gas jet for propulsion. Alternatively, a chemically inert [[reaction mass]] can be heated by a high-energy power source through a heat exchanger in lieu of a combustion chamber.

[[Solid rocket]] propellants are prepared in a mixture of fuel and oxidising components called ''grain'', and the propellant storage casing effectively becomes the combustion chamber.

===Injection===
[[Liquid-propellant rocket|Liquid-fuelled rockets]] force separate fuel and oxidiser components into the combustion chamber, where they mix and burn. [[Hybrid rocket]] engines use a combination of solid and liquid or gaseous propellants. Both liquid and hybrid rockets use ''[[Liquid-fuel rocket#Injectors|injectors]]'' to introduce the propellant into the chamber. These are often an array of simple [[jet (nozzle)|jet]]s – holes through which the propellant escapes under pressure; but sometimes may be more complex spray nozzles. When two or more propellants are injected, the jets usually deliberately cause the propellants to collide as this breaks up the flow into smaller droplets that burn more easily.

===Combustion chamber===
For chemical rockets the combustion chamber is typically cylindrical, and [[flame holder]]s, used to hold a part of the combustion in a slower-flowing portion of the combustion chamber, are not needed. The dimensions of the cylinder are such that the propellant is able to combust thoroughly; different [[rocket propellant]]s require different combustion chamber sizes for this to occur.

This leads to a number called <math>L^*</math>, the [[characteristic length]]:
:<math>L^* = \frac {V_c} {A_t}</math>
where:
*<math>V_c</math> is the volume of the chamber
*<math>A_t</math> is the area of the throat of the nozzle.
L* is typically in the range of {{convert|64|-|152|cm|in}}.

The temperatures and pressures typically reached in a rocket combustion chamber in order to achieve practical [[thermal efficiency]] are extreme compared to a [[afterburner|non-afterburning]] [[airbreathing jet engine]]. No atmospheric nitrogen is present to dilute and cool the combustion, so the propellant mixture can reach true [[stoichiometric]] ratios. This, in combination with the high pressures, means that the rate of heat conduction through the walls is very high.

In order for fuel and oxidiser to flow into the chamber, the pressure of the propellants entering the combustion chamber must exceed the pressure inside the combustion chamber itself. This may be accomplished by a variety of design approaches including [[turbopump]]s or, in simpler engines, via [[Pressure-fed cycle (rocket)|sufficient tank pressure]] to advance fluid flow. Tank pressure may be maintained by several means, including a high-pressure [[helium]] pressurization system common to many large rocket engines or, in some newer rocket systems, by a bleed-off of high-pressure gas from the engine cycle to [[autogenous pressurization|autogenously pressurize]] the propellant tanks<ref name=nsf20160927>
{{cite news |last=Bergin|first=Chris |url=https://www.nasaspaceflight.com/2016/09/spacex-reveals-mars-game-changer-colonization-plan/ |title=SpaceX reveals ITS Mars game changer via colonization plan |work=[[NASASpaceFlight.com]] |date=2016-09-27 |access-date=2016-09-27 }}</ref><ref name=sfi20160927/> For example, the self-pressurization gas system of the [[SpaceX Starship]] is a critical part of SpaceX strategy to reduce launch vehicle fluids from five in their legacy Falcon 9 vehicle family to just two in Starship, eliminating not only the helium tank pressurant but all [[hypergolic propellant]]s as well as [[nitrogen]] for cold-gas [[reaction control system|reaction-control thrusters]].<ref name=nsf20161003/>

===Nozzle===
{{Main|Rocket engine nozzle}}
[[File:Rocket thrust.svg|thumb|right|Rocket thrust is caused by pressures acting in the combustion chamber and nozzle. From Newton's third law, equal and opposite pressures act on the exhaust, and this accelerates it to high speeds.]]
The hot gas produced in the combustion chamber is permitted to escape through an opening (the "throat"), and then through a diverging expansion section. When sufficient pressure is provided to the nozzle (about 2.5–3 times ambient pressure), the nozzle ''[[choked flow|choke]]s'' and a supersonic jet is formed, dramatically accelerating the gas, converting most of the thermal energy into kinetic energy. Exhaust speeds vary, depending on the [[expansion ratio]] the nozzle is designed for, but exhaust speeds as high as ten times the [[speed of sound]] in air at sea level are not uncommon. About half of the rocket engine's thrust comes from the unbalanced pressures inside the combustion chamber, and the rest comes from the pressures acting against the inside of the nozzle (see diagram). As the gas expands ([[Adiabatic process|adiabatically]]) the pressure against the nozzle's walls forces the rocket engine in one direction while accelerating the gas in the other.

{{Anchor|opt_expansion}} 
[[File:Rocket nozzle expansion.svg|thumb|right|upright|The four expansion regimes of a de Laval nozzle:
• under-expanded
• perfectly expanded
• over-expanded
• grossly over-expanded]]
The most commonly used nozzle is the [[de Laval nozzle]], a fixed geometry nozzle with a high expansion-ratio. The large bell- or cone-shaped nozzle extension beyond the throat gives the rocket engine its characteristic shape.

The exit [[static pressure#Static pressure in fluid dynamics|static pressure]] of the exhaust jet depends on the chamber pressure and the ratio of exit to throat area of the nozzle. As exit pressure varies from the ambient (atmospheric) pressure, a choked nozzle is said to be
* '''under-expanded''' (exit pressure greater than ambient),
* '''perfectly expanded''' (exit pressure equals ambient),
* '''over-expanded''' (exit pressure less than ambient; [[shock diamond]]s form outside the nozzle), or
* '''grossly over-expanded''' (a [[shock wave]] forms inside the nozzle extension).

In practice, perfect expansion is only achievable with a variable–exit-area nozzle (since ambient pressure decreases as altitude increases), and is not possible above a certain altitude as ambient pressure approaches zero. If the nozzle is not perfectly expanded, then loss of efficiency occurs. Grossly over-expanded nozzles lose less efficiency, but can cause mechanical problems with the nozzle. Fixed-area nozzles become progressively more under-expanded as they gain altitude. Almost all de Laval nozzles will be momentarily grossly over-expanded during startup in an atmosphere.<ref name="HuzelAndHuang">{{cite book
|last = Huzel
|first = Dexter K.
|last2 = Huang
|first2 = David H.
|date = 1 January 1971
|title = NASA SP-125, Design of Liquid Propellant Rocket Engines, Second Edition
|url = https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710019929_1971019929.pdf
|publisher = NASA
|page = 
|archive-url = https://web.archive.org/web/20170324150551/https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710019929_1971019929.pdf/
|archive-date = 24 March 2017
|url-status = dead
|access-date = 7 July 2017
}}</ref>

Nozzle efficiency is affected by operation in the atmosphere because atmospheric pressure changes with altitude; but due to the supersonic speeds of the gas exiting from a rocket engine, the pressure of the jet may be either below or above ambient, and equilibrium between the two is not reached at all altitudes (see diagram).

====Back pressure and optimal expansion====
For optimal performance, the pressure of the gas at the end of the nozzle should just equal the ambient pressure: if the exhaust's pressure is lower than the ambient pressure, then the vehicle will be slowed by the difference in pressure between the top of the engine and the exit; on the other hand, if the exhaust's pressure is higher, then exhaust pressure that could have been converted into thrust is not converted, and energy is wasted.

To maintain this ideal of equality between the exhaust's exit pressure and the ambient pressure, the diameter of the nozzle would need to increase with altitude, giving the pressure a longer nozzle to act on (and reducing the exit pressure and temperature). This increase is difficult to arrange in a lightweight fashion, although is routinely done with other forms of jet engines. In rocketry a lightweight compromise nozzle is generally used and some reduction in atmospheric performance occurs when used at other than the 'design altitude' or when throttled. To improve on this, various exotic nozzle designs such as the [[plug nozzle]], [[stepped nozzles]], the [[expanding nozzle]] and the [[aerospike engine|aerospike]] have been proposed, each providing some way to adapt to changing ambient air pressure and each allowing the gas to expand further against the nozzle, giving extra thrust at higher altitudes.

When exhausting into a sufficiently low ambient pressure (vacuum) several issues arise. One is the sheer weight of the nozzle—beyond a certain point, for a particular vehicle, the extra weight of the nozzle outweighs any performance gained. Secondly, as the exhaust gases adiabatically expand within the nozzle they cool, and eventually some of the chemicals can freeze, producing 'snow' within the jet. This causes instabilities in the jet and must be avoided.

On a [[de Laval nozzle]], exhaust gas flow detachment will occur in a grossly over-expanded nozzle. As the detachment point will not be uniform around the axis of the engine, a side force may be imparted to the engine. This side force may change over time and result in control problems with the launch vehicle.

Advanced [[altitude compensating nozzle|altitude-compensating]] designs, such as the [[aerospike engine|aerospike]] or [[plug nozzle]], attempt to minimize performance losses by adjusting to varying expansion ratio caused by changing altitude.

===Propellant efficiency===
{{See also|Specific impulse}}
[[Image:Nozzle de Laval diagram.svg|thumb|right|upright|Typical temperature (T), pressure (p), and velocity (v) profiles in a de Laval Nozzle]]
For a rocket engine to be propellant efficient, it is important that the maximum pressures possible be created on the walls of the chamber and nozzle by a specific amount of propellant; as this is the source of the thrust. This can be achieved by all of:

* heating the propellant to as high a temperature as possible (using a high energy fuel, containing hydrogen and carbon and sometimes metals such as [[aluminium]], or even using nuclear energy)
* using a low specific density gas (as hydrogen rich as possible)
* using propellants which are, or decompose to, simple molecules with few degrees of freedom to maximise translational velocity

Since all of these things minimise the mass of the propellant used, and since pressure is proportional to the mass of propellant present to be accelerated as it pushes on the engine, and since from [[Newton's third law]] the pressure that acts on the engine also reciprocally acts on the propellant, it turns out that for any given engine, the speed that the propellant leaves the chamber is unaffected by the chamber pressure (although the thrust is proportional). However, speed is significantly affected by all three of the above factors and the exhaust speed is an excellent measure of the engine propellant efficiency. This is termed ''exhaust velocity'', and after allowance is made for factors that can reduce it, the '''[[effective exhaust velocity]]''' is one of the most important parameters of a rocket engine (although weight, cost, ease of manufacture etc. are usually also very important).

For aerodynamic reasons the flow goes sonic ("[[Choked flow|chokes]]") at the narrowest part of the nozzle, the 'throat'. Since the [[speed of sound]] in gases increases with the square root of temperature, the use of hot exhaust gas greatly improves performance. By comparison, at room temperature the speed of sound in air is about 340 m/s while the speed of sound in the hot gas of a rocket engine can be over 1700 m/s; much of this performance is due to the higher temperature, but additionally rocket propellants are chosen to be of low molecular mass, and this also gives a higher velocity compared to air.

Expansion in the rocket nozzle then further multiplies the speed, typically between 1.5 and 2 times, giving a highly [[collimated]] hypersonic exhaust jet. The speed increase of a rocket nozzle is mostly determined by its area expansion ratio—the ratio of the area of the exit to the area of the throat, but detailed properties of the gas are also important. Larger ratio nozzles are more massive but are able to extract more heat from the combustion gases, increasing the exhaust velocity.

===Thrust vectoring===
{{Main|Thrust vectoring}}
Vehicles typically require the overall thrust to change direction over the length of the burn. A number of different ways to achieve this have been flown:

* The entire engine is mounted on a [[hinge]] or [[gimbal]] and any propellant feeds reach the engine via low pressure flexible pipes or rotary couplings.
* Just the combustion chamber and nozzle is gimballed, the pumps are fixed, and high pressure feeds attach to the engine.
* Multiple engines (often canted at slight angles) are deployed but throttled to give the overall vector that is required, giving only a very small penalty.
* High-temperature vanes protrude into the exhaust and can be tilted to deflect the jet.

==Overall performance==
Rocket technology can combine very high thrust ([[meganewton]]s), very high exhaust speeds (around 10 times the speed of sound in air at sea level) and very high thrust/weight ratios (>100) ''simultaneously'' as well as being able to operate outside the atmosphere, and while permitting the use of low pressure and hence lightweight tanks and structure.

Rockets can be further optimised to even more extreme performance along one or more of these axes at the expense of the others.

===Specific impulse===
{{Specific impulse|align=right}}
{{Main|Specific impulse}}

The most important metric for the efficiency of a rocket engine is [[impulse (physics)|impulse]] per unit of [[propellant]], this is called [[specific impulse]] (usually written <math>I_{sp}</math>). This is either measured as a speed (the ''effective exhaust velocity'' <math>v_{e}</math> in metres/second or ft/s) or as a time (seconds). For example, if an engine producing 100 pounds of thrust runs for 320 seconds and burns 100 pounds of propellant, then the specific impulse is 320 seconds. The higher the specific impulse, the less propellant is required to provide the desired impulse.

The specific impulse that can be achieved is primarily a function of the propellant mix (and ultimately would limit the specific impulse), but practical limits on chamber pressures and the nozzle expansion ratios reduce the performance that can be achieved.

===Net thrust===
{{Main|Thrust}}
Below is an approximate equation for calculating the net thrust of a rocket engine:<ref>{{cite book|author=George P. Sutton|author2=Oscar Biblarz|name-list-style=amp|title=Rocket Propulsion Elements|edition=8th|publisher=Wiley Interscience|date=2010|isbn=9780470080245|url=https://archive.org/details/Rocket_Propulsion_Elements_8th_Edition_by_Oscar_Biblarz_George_P._Sutton/page/34/mode/2up}} See Equation 2-14.</ref>

{{block indent|<math>F_n = \dot{m}\;v_{e} = \dot{m}\;v_{e-opt} + A_{e}(p_{e} - p_{amb})</math>}}

{| border="0" cellpadding="2" style="margin-left:1em"
|-
|align=right|where:
| 
|-
!align=right|<math>\dot{m}</math>
|align=left|=  exhaust gas mass flow
|-
!align=right|<math>v_{e}</math>
|align=left|=  effective exhaust velocity (sometimes otherwise denoted as ''c'' in publications)
|-
!align=right|<math>v_{e-opt}</math>
|align=left|=  effective jet velocity when Pamb = Pe
|-
!align=right|<math>A_{e}</math>
|align=left|=  flow area at nozzle exit plane (or the plane where the jet leaves the nozzle if separated flow)
|-
!align=right|<math>p_{e}</math>
|align=left|=  static pressure at nozzle exit plane
|-
!align=right|<math>p_{amb}</math>
|align=left|=  ambient (or atmospheric) pressure
|}

Since, unlike a jet engine, a conventional rocket motor lacks an air intake, there is no 'ram drag' to deduct from the gross thrust. Consequently, the net thrust of a rocket motor is equal to the gross thrust (apart from static back pressure).

The <math>\dot{m}\;v_{e-opt}\,</math> term represents the momentum thrust, which remains constant at a given throttle setting, whereas the <math>A_{e}(p_{e} - p_{amb})\,</math> term represents the pressure thrust term. At full throttle, the net thrust of a rocket motor improves slightly with increasing altitude, because as atmospheric pressure decreases with altitude, the pressure thrust term increases. At the surface of the Earth the pressure thrust may be reduced by up to 30%, depending on the engine design. This reduction drops roughly exponentially to zero with increasing altitude.

Maximum efficiency for a rocket engine is achieved by maximising the momentum contribution of the equation without incurring penalties from over expanding the exhaust. This occurs when <math>p_{e} = p_{amb}</math>. Since ambient pressure changes with altitude, most rocket engines spend very little time operating at peak efficiency.

Since specific impulse is force divided by the rate of mass flow, this equation means that the specific impulse varies with altitude.

===Vacuum specific impulse, Isp===

Due to the specific impulse varying with pressure, a quantity that is easy to compare and calculate with is useful. Because rockets [[choked flow|choke]] at the throat, and because the supersonic exhaust prevents external pressure influences travelling upstream, it turns out that the pressure at the exit is ideally exactly proportional to the propellant flow <math> \dot{m}</math>, provided the mixture ratios and combustion efficiencies are maintained. It is thus quite usual to rearrange the above equation slightly:<ref>{{cite book|author=George P. Sutton|author2=Oscar Biblarz|name-list-style=amp|title=Rocket Propulsion Elements|edition=8th|publisher=Wiley Interscience|date=2010|isbn=9780470080245|url=https://archive.org/details/Rocket_Propulsion_Elements_8th_Edition_by_Oscar_Biblarz_George_P._Sutton/page/34/mode/2up}} See Equation 3-33.</ref>

{{block indent|<math> F_{vac} = C_f\, \dot{m}\, c^*</math>}}

and so define the ''vacuum Isp'' to be:

{{block indent|<math>v_{evac} = C_f\, c^* \,</math>}}

where:

{{block indent|1=<math>c^*</math>  =  the [[characteristic velocity]] of the combustion chamber (dependent on propellants and combustion efficiency)}}
{{block indent|1=<math>C_f</math>  =  the thrust coefficient constant of the nozzle (dependent on nozzle geometry, typically about 2)}}

And hence:
{{block indent|<math> F_n = \dot{m}\, v_{evac} - A_{e}\, p_{amb}</math>}}

===Throttling===

Rockets can be throttled by controlling the propellant combustion rate <math> \dot{m}</math> (usually measured in kg/s or lb/s). In liquid and hybrid rockets, the propellant flow entering the chamber is controlled using valves, in [[solid rocket]]s it is controlled by changing the area of propellant that is burning and this can be designed into the propellant grain (and hence cannot be controlled in real-time).

Rockets can usually be throttled down to an exit pressure of about one-third of ambient pressure<ref name=Sutton/> (often limited by flow separation in nozzles) and up to a maximum limit determined only by the mechanical strength of the engine.

In practice, the degree to which rockets can be throttled varies greatly, but most rockets can be throttled by a factor of 2 without great difficulty;<ref name=Sutton/> the typical limitation is combustion stability, as for example, injectors need a minimum pressure to avoid triggering damaging oscillations (chugging or combustion instabilities); but injectors can be optimised and tested for wider ranges.

For example, some more recent liquid-propellant engine designs that have been optimised for greater throttling capability ([[BE-3]], [[Raptor (rocket engine)|Raptor]]) can be throttled to as low as 18–20 per cent of rated thrust.<ref name="sn20150407">
{{cite news |last1=Foust|first=Jeff |title=Blue Origin Completes BE-3 Engine as BE-4 Work Continues |url=http://spacenews.com/blue-origin-completes-be-3-engine-as-be-4-work-continues/ |access-date=2016-10-20 |work=Space News |date=2015-04-07 }}</ref><ref name="sfi20160927">{{cite news |url= http://www.spaceflightinsider.com/organizations/space-exploration-technologies/elon-musk-shows-off-interplanetary-transport-system/ |title= Elon Musk Shows Off Interplanetary Transport System |publisher= Spaceflight Insider |last= Richardson |first= Derek |date= 2016-09-27 |access-date= 2016-10-20 |archive-date= 2016-10-01 |archive-url= https://web.archive.org/web/20161001225649/http://www.spaceflightinsider.com/organizations/space-exploration-technologies/elon-musk-shows-off-interplanetary-transport-system/ |url-status= dead }}</ref>

Solid rockets can be throttled by using shaped grains that will vary their surface area over the course of the burn.<ref name="Sutton" />

===Energy efficiency===
{{Further|Rocket#Energy efficiency}}
[[File:Rocket propulsion efficiency.svg|thumb|Rocket vehicle mechanical efficiency as a function of vehicle instantaneous speed divided by effective exhaust speed. These percentages need to be multiplied by internal engine efficiency to get overall efficiency.]]
Rocket engine nozzles are surprisingly efficient [[heat engines]] for generating a high speed jet, as a consequence of the high combustion temperature and high [[compression ratio]]. Rocket nozzles give an excellent approximation to [[adiabatic expansion]] which is a reversible process, and hence they give efficiencies which are very close to that of the [[Carnot cycle]]. Given the temperatures reached, over 60% efficiency can be achieved with chemical rockets.

For a ''vehicle'' employing a rocket engine the energetic efficiency is very good if the vehicle speed approaches or somewhat exceeds the exhaust velocity (relative to launch); but at low speeds the [[Propulsive efficiency|energy efficiency]] goes to 0% at zero speed (as with all [[jet propulsion]]). See [[Rocket#Energy efficiency|Rocket energy efficiency]] for more details.

{{clear}}

===Thrust-to-weight ratio===
{{Main|thrust-to-weight ratio}}
Rockets, of all the jet engines, indeed of essentially all engines, have the highest thrust-to-weight ratio. This is especially true for liquid-fuelled rocket engines.

This high performance is due to the small volume of [[pressure vessel]]s that make up the engine—the pumps, pipes and combustion chambers involved. The lack of inlet duct and the use of dense liquid propellant allows the pressurisation system to be small and lightweight, whereas duct engines have to deal with air which has around three orders of magnitude lower density.

{{Engine thrust to weight table}}

Of the liquid fuels used, density is lowest for [[liquid hydrogen]]. Although hydrogen/oxygen burning has the highest [[specific impulse]] of any in-use chemical rocket, hydrogen's very low density (about one-fourteenth that of water) requires larger and heavier turbopumps and pipework, which decreases the engine's thrust-to-weight ratio (for example the RS-25) compared to those that do not use hydrogen (NK-33).

==Mechanical issues==
Rocket combustion chambers are normally operated at fairly high pressure, typically 10–200{{nbsp}}bar (1–20{{nbsp}}MPa, 150–3,000{{nbsp}}psi). When operated within significant atmospheric pressure, higher combustion chamber pressures give better performance by permitting a larger and more efficient nozzle to be fitted without it being grossly overexpanded.

However, these high pressures cause the outermost part of the chamber to be under very large [[hoop stress]]es – rocket engines are [[pressure vessel]]s.

Worse, due to the high temperatures created in rocket engines the materials used tend to have a significantly lowered working tensile strength.

In addition, significant temperature gradients are set up in the walls of the chamber and nozzle, these cause differential expansion of the inner liner that create [[internal stresses]].

=== Hard starts ===
A '''hard start''' refers to an over-pressure condition during start of a rocket engine at ignition. In the worst cases, this takes the form of an unconfined explosion, resulting in the damage or destruction of the engine.

Rocket fuels, [[hypergolic]] or otherwise, must be introduced into the combustion chamber at the correct rate in order to have a controlled rate of production of hot gas.<ref>{{Cite web |title=Introducing Propellant into a Combustion Chamber |url=https://www.idc-online.com/technical_references/pdfs/mechanical_engineering/Introducing_Propellant_into_a_Combustion_Chamber.pdf |access-date=February 16, 2024 |website=IDC Online}}</ref> A "hard start" indicates that the quantity of combustible propellant that entered the combustion chamber prior to ignition was too large. The result is an excessive spike of pressure, possibly leading to structural failure or explosion.

Avoiding hard starts involves careful timing of the ignition relative to valve timing or varying the mixture ratio so as to limit the maximum pressure that can occur or simply ensuring an adequate ignition source is present well prior to propellant entering the chamber.

Explosions from hard starts usually cannot happen with purely gaseous propellants, since the amount of the gas present in the chamber is limited by the injector area relative to the throat area, and for practical designs, propellant mass escapes too quickly to be an issue.

A famous example of a hard start was the explosion of [[Wernher von Braun]]'s "1W" engine during a demonstration to General [[Walter Dornberger]] on December 21, 1932. Delayed ignition allowed the chamber to fill with alcohol and liquid oxygen, which exploded violently. Shrapnel was embedded in the walls, but nobody was hit.

==Acoustic issues==
The extreme vibration and acoustic environment inside a rocket motor commonly result in peak stresses well above mean values, especially in the presence of [[organ pipe]]-like resonances and gas turbulence.<ref>{{Cite news|url=https://www.technologyreview.com/s/414364/whats-the-deal-with-rocket-vibrations/|title=What's the Deal with Rocket Vibrations?|last=Sauser|first=Brittany|work=MIT Technology Review|access-date=2018-04-27|language=en}}</ref>

===Combustion instabilities===
The combustion may display undesired instabilities, of sudden or periodic nature. The pressure in the injection chamber may increase until the propellant flow through the injector plate decreases; a moment later the pressure drops and the flow increases, injecting more propellant in the combustion chamber which burns a moment later, and again increases the chamber pressure, repeating the cycle. This may lead to high-amplitude pressure oscillations, often in ultrasonic range, which may damage the motor. Oscillations of ±200 psi at 25 kHz were the cause of failures of early versions of the [[LGM-25C Titan II|Titan II]] missile second stage engines. The other failure mode is a [[deflagration to detonation transition]]; the supersonic [[Longitudinal wave|pressure wave]] formed in the combustion chamber may destroy the engine.<ref name="titan2">{{cite book|author=David K. Stumpf|title=Titian II: A History of a Cold War Missile Program|publisher=University of Arkansas Press|date=2000|isbn=1-55728-601-9}}</ref>

Combustion instability was also a problem during [[SM-65 Atlas|Atlas]] development. The Rocketdyne engines used in the Atlas family were found to suffer from this effect in several static firing tests, and three missile launches exploded on the pad due to rough combustion in the booster engines. In most cases, it occurred while attempting to start the engines with a "dry start" method whereby the igniter mechanism would be activated prior to propellant injection. During the process of man-rating Atlas for [[Project Mercury]], solving combustion instability was a high priority, and the final two Mercury flights sported an upgraded propulsion system with baffled injectors and a hypergolic igniter.

The problem affecting Atlas vehicles was mainly the so-called "racetrack" phenomenon, where burning propellant would swirl around in a circle at faster and faster speeds, eventually producing vibration strong enough to rupture the engine, leading to complete destruction of the rocket. It was eventually solved by adding several baffles around the injector face to break up swirling propellant.

More significantly, combustion instability was a problem with the Saturn [[F-1 (rocket engine)|F-1 engines]]. Some of the early units tested exploded during static firing, which led to the addition of injector baffles.

In the Soviet space program, combustion instability also proved a problem on some rocket engines, including the RD-107 engine used in the R-7 family and the RD-216 used in the R-14 family, and several failures of these vehicles occurred before the problem was solved. Soviet engineering and manufacturing processes never satisfactorily resolved combustion instability in larger RP-1/LOX engines, so the RD-171 engine used to power the Zenit family still used four smaller thrust chambers fed by a common engine mechanism.

The combustion instabilities can be provoked by remains of cleaning solvents in the engine (e.g. the first attempted launch of a Titan II in 1962), reflected shock wave, initial instability after ignition, explosion near the nozzle that reflects into the combustion chamber, and many more factors. In stable engine designs the oscillations are quickly suppressed; in unstable designs they persist for prolonged periods. Oscillation suppressors are commonly used.

Three different types of combustion instabilities occur:

====Chugging====
A low frequency oscillation in chamber pressure below 200 [[Hertz]]. Usually it is caused by pressure variations in feed lines due to variations in acceleration of the vehicle, when rocket engines are building up thrust, are shut down or are being throttled.<ref name=sutton1975/>{{rp|261}}<ref name="HuzelAndHuang"/>{{rp|146}}

Chugging can cause a worsening feedback loop, as cyclic variation in thrust causes longitudinal vibrations to travel up the rocket, causing the fuel lines to vibrate, which in turn do not deliver propellant smoothly into the engines. This phenomenon is known as "[[pogo oscillation]]s" or "pogo", named after the [[pogo stick]].<ref name="sutton1975" />{{rp|258}}

In the worst case, this may result in damage to the payload or vehicle. Chugging can be minimised by using several methods, such as installing energy-absorbing devices on feed lines.<ref name=sutton1975/>{{rp|259}} Chugging may cause Screeching.<ref name="HuzelAndHuang"/>{{rp|146}}

====Buzzing====
An intermediate frequency oscillation in chamber pressure between 200 and 1000 [[Hertz]]. Usually caused due to insufficient pressure drop across the injectors.<ref name=sutton1975/>{{rp|261}} It generally is mostly annoying, rather than being damaging.

Buzzing is known to have adverse effects on engine performance and reliability, primarily as it causes [[material fatigue]].<ref name="HuzelAndHuang" />{{rp|147}} In extreme cases combustion can end up being forced backwards through the injectors – this can cause explosions with monopropellants.{{citation needed|date=April 2018}} Buzzing may cause Screeching.<ref name="sutton1975" />{{rp|261}}

====Screeching====
A high frequency oscillation in chamber pressure above 1000 [[Hertz]], sometimes called screaming or squealing. The most immediately damaging, and the hardest to control. It is due to acoustics within the combustion chamber that often couples to the chemical combustion processes that are the primary drivers of the energy release, and can lead to unstable resonant "screeching" that commonly leads to catastrophic failure due to thinning of the insulating thermal boundary layer. Acoustic oscillations can be excited by thermal processes, such as the flow of hot air through a pipe or combustion in a chamber. Specifically, standing acoustic waves inside a chamber can be intensified if combustion occurs more intensely in regions where the pressure of the acoustic wave is maximal.<ref name=strutt1896>
{{cite book|author=John W. Strutt|title=The Theory of Sound – Volume 2|edition=2nd|publisher=Macmillan (reprinted by Dover Publications in 1945)|date=1896|page=226}} According to Lord Rayleigh's criterion for thermoacoustic processes, "If heat be given to the air at the moment of greatest condensation, or be taken from it at the moment of greatest rarefaction, the vibration is encouraged. On the other hand, if heat be given at the moment of greatest rarefaction, or abstracted at the moment of greatest condensation, the vibration is discouraged."</ref><ref>Lord Rayleigh (1878) "The explanation of certain acoustical phenomena" (namely, the [[Rijke tube]]) ''Nature'', vol. 18, pages 319–321.</ref><ref>E. C. Fernandes and M. V. Heitor, "Unsteady flames and the Rayleigh criterion" in {{cite book|editor=F. Culick|editor2=M. V. Heitor|editor3=J. H. Whitelaw|title=Unsteady Combustion|edition=1st|publisher=Kluwer Academic Publishers|date=1996|page=4|isbn=0-7923-3888-X|url=https://books.google.com/books?id=Je_hG6UfnogC&pg=PA1}}</ref><ref name=sutton1975>
{{cite book |author=G.P. Sutton |author2=D.M. Ross |name-list-style=amp |title=Rocket Propulsion Elements: An Introduction to the Engineering of Rockets |edition=4th |url=https://archive.org/details/rocketpropulsion0000sutt/page/258/mode/2up |publisher=Wiley Interscience |date=1975 |isbn=0-471-83836-5 }} See Chapter 8, Section 6 and especially Section 7, re combustion instability.</ref>

Such effects are very difficult to predict analytically during the design process, and have usually been addressed by expensive, time-consuming and extensive testing, combined with trial and error remedial correction measures.

Screeching is often dealt with by detailed changes to injectors, changes in the propellant chemistry, vaporising the propellant before injection or use of [[Helmholtz damper]]s within the combustion chambers to change the resonant modes of the chamber.{{citation needed|date=April 2018}}

Testing for the possibility of screeching is sometimes done by exploding small explosive charges outside the combustion chamber with a tube set tangentially to the combustion chamber near the injectors to determine the engine's [[impulse response]] and then evaluating the time response of the chamber pressure- a fast recovery indicates a stable system.

===Exhaust noise===
{{Main|acoustic signature}}
For all but the very smallest sizes, rocket exhaust compared to other engines is generally very noisy. As the [[hypersonic]] exhaust mixes with the ambient air, [[shock wave]]s are formed. The [[Space Shuttle]] generated over 200 [[dB(A)]] of noise around its base. To reduce this, and the risk of payload damage or injury to the crew atop the stack, the [[mobile launcher platform]] was fitted with a [[Sound Suppression System]] that sprayed {{convert|1.1|e6L|USgal}} of water around the base of the rocket in 41 seconds at launch time. Using this system kept sound levels within the payload bay to 142 dB.<ref>{{Cite web
|title=Sound Suppression System
|publisher=NASA
|url=https://www.nasa.gov/mission_pages/shuttle/launch/sound-suppression-system.html
|access-date=2017-02-09
|archive-date=2020-08-10
|archive-url=https://web.archive.org/web/20200810203904/https://www.nasa.gov/mission_pages/shuttle/launch/sound-suppression-system.html
|url-status=dead
}}</ref>

The [[sound intensity]] from the shock waves generated depends on the size of the rocket and on the exhaust velocity. Such shock waves seem to account for the characteristic crackling and popping sounds produced by large rocket engines when heard live. These noise peaks typically overload microphones and audio electronics, and so are generally weakened or entirely absent in recorded or broadcast audio reproductions. For large rockets at close range, the acoustic effects could actually kill.<ref name="CR566">R.C. Potter and M.J. Crocker (1966). [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660030602_1966030602.pdf NASA CR-566, Acoustic Prediction Methods For Rocket Engines, Including The Effects Of Clustered Engines And Deflected Flow] From website of the National Aeronautics and Space Administration Langley (NASA Langley)</ref>

More worryingly for space agencies, such sound levels can also damage the launch structure, or worse, be reflected back at the comparatively delicate rocket above. This is why so much water is typically used at launches. The water spray changes the acoustic qualities of the air and reduces or deflects the sound energy away from the rocket.

Generally speaking, noise is most intense when a rocket is close to the ground, since the noise from the engines radiates up away from the jet, as well as reflecting off the ground. Also, when the vehicle is moving slowly, little of the chemical energy input to the engine can go into increasing the kinetic energy of the rocket (since useful power ''P'' transmitted to the vehicle is <math>P = F*V</math> for thrust ''F'' and speed ''V''). Then the largest portion of the energy is dissipated in the exhaust's interaction with the ambient air, producing noise. This noise can be reduced somewhat by flame trenches with roofs, by water injection around the jet and by deflecting the jet at an angle.

== Rocket engine development ==
=== United States ===
The development of the US rocket engine industry has been shaped by a complex web of relationships between government agencies, private companies, research institutions, and other stakeholders.

Since the establishment of the first [[liquid-propellant rocket]] engine company ([[Reaction Motors|Reaction Motors, Inc.]]) in 1941 and the first government laboratory ([[Guggenheim Aeronautical Laboratory|GALCIT]]) devoted to the subject, the US liquid-propellant rocket engine (LPRE) industry has undergone significant changes. At least 14 US companies have been involved in the design, development, manufacture, testing, and flight support operations of various types of rocket engines from 1940 to 2000. In contrast to other countries like Russia, China, or India, where only government or pseudogovernment organisations engage in this business, the US government relies heavily on private industry. These commercial companies are essential to the continued viability of the United States and its form of governance, as they compete with one another to provide cutting-edge rocket engines that meet the needs of the government, the military, and the private sector. In the United States the company that develops the LPRE usually is awarded the production contract.

Generally, the need or demand for a new rocket engine comes from government agencies such as [[NASA]] or the [[United States Department of Defense|Department of Defense]]. Once the need is identified, government agencies may issue [[Request for proposal|requests for proposals]] (RFPs) to solicit proposals from private companies and research institutions. Private companies and research institutions, in turn, may invest in research and development (R&D) activities to develop new rocket engine technologies that meet the needs and specifications outlined in the RFPs.

Alongside private companies, universities, independent research institutes and government laboratories also play a critical role in the research and development of rocket engines.

Universities provide graduate and undergraduate education to train qualified technical personnel, and their research programs often contribute to the advancement of rocket engine technologies. More than 25 universities in the US have taught or are currently teaching courses related to Liquid Propellant Rocket Engines (LPREs), and their graduate and undergraduate education programs are considered one of their most important contributions. Universities such as Princeton University, Cornell University, Purdue University, Pennsylvania State University, University of Alabama, the Navy's Post-Graduate School, or the California Institute of Technology have conducted excellent R&D work on topics related to the rocket engine industry.<ref name=":0" /> One of the earliest examples of the contribution of universities to the rocket engine industry is the work of the GALCIT in 1941. They demonstrated the first jet-assisted takeoff (JATO) rockets to the Army, leading to the establishment of the Jet Propulsion Laboratory.

However the transfer of knowledge from research professors and their projects to the rocket engine industry has been a mixed experience. While some notable professors and relevant research projects have positively influenced industry practices and understanding of LPREs, the connection between university research and commercial companies has been inconsistent and weak.<ref name=":0" /> Universities were not always aware of the industry's specific needs, and engineers and designers in the industry had limited knowledge of university research. As a result, many university research programs remained relatively unknown to industry decision-makers. Furthermore, in the last few decades, certain university research projects, while interesting to professors, were not useful to the industry due to a lack of communication or relevance to industry needs.<ref name=":0" />

Government laboratories, including the Rocket Propulsion Laboratory (now part of Air Force Research Laboratory), Arnold Engineering Test Center, NASA Marshall Space Flight Center, Jet Propulsion Laboratory, Stennis Space Center, White Sands Proving Grounds, and NASA John H. Glenn Research Center, have played crucial roles in the development of liquid rocket propulsion engines (LPREs).<ref name=":0" /> They have conducted unbiased testing, guided work at US and some non-US contractors, performed research and development, and provided essential testing facilities including hover test facilities and simulated altitude test facilities and resources. Initially, private companies or foundations financed smaller test facilities, but since the 1950s, the U.S. government has funded larger test facilities at government laboratories. This approach reduced costs for the government by not building similar facilities at contractors' plants but increased complexity and expenses for contractors. Nonetheless, government laboratories have solidified their significance and contributed to LPRE advancements.

LPRE programs have been subject to several cancellations in the United States, even after spending millions of dollars on their development. For example, the M-l LOX/LH2 LPRE, Titan I, and the RS-2200 aerospike, as well as several JATO units and large uncooled thrust chambers were cancelled. The cancellations of these programs were not related to the specific LPRE's performance or any issues with it. Instead, they were due to the cancellation of the vehicle programs the engine was intended for or budget cuts imposed by the government.

=== USSR ===
Russia and the former Soviet Union was and still is the world's foremost nation in developing and building rocket engines. From 1950 to 1998, their organisations developed, built, and put into operation a larger number and a larger variety of liquid propellant rocket engine (LPRE) designs than any other country. Approximately 500 different LPREs have been developed before 2003. For comparison the United States has developed slightly more than 300 (before 2003). The Soviets also had the most rocket-propelled flight vehicles. They had more liquid propellant [[ballistic missile]]s and more [[Launch vehicle|space launch vehicles]] derived or converted from these decommissioned ballistic missiles than any other nation. As of the end of 1998, the Russians (or earlier the Soviet Union) had successfully launched 2573 [[satellite]]s with LPREs or almost 65% of the world total of 3973. All of these vehicle flights were made possible by the timely development of suitable high-performance reliable LPREs.<ref name=":0">{{Cite book |last=Sutton |first=George |title=History of Liquid Propellant Rocket Engines |publisher=AIAA |year=2006 |isbn=978-1-56347-649-5}}</ref>

==== Institutions and actors ====
Unlike many other countries where the development and production of rocket engines were consolidated within a single organisation, the Soviet Union took a different approach, they established numerous specialised [[OKB|design bureaus]] (DB) which would compete for development contracts. These design bureaus, or "konstruktorskoye buro" (KB) in Russian were state run organisations which were primarily responsible for carrying out [[Research and development|research, development]] and [[Prototype|prototyping]] of advanced technologies usually related to [[Military technology|military hardware]], such as [[turbojet]] [[engine]]s, aircraft components, [[missile]]s, or [[Launch vehicle|space launch vehicles]].

[[OKB|Design Bureaus]] which specialised in rocket engines often possessed the necessary personnel, facilities, and equipment to conduct l[[Launch vehicle system tests|aboratory tests, flow tests, and ground testing of experimental rocket engines]]. Some even had specialised facilities for testing very large engines, conducting [[Launch vehicle system tests|static firings]] of engines installed in vehicle stages, or simulating altitude conditions during engine tests. In certain cases, engine testing, certification and [[quality control]] were outsourced to other organisations and locations with more suitable test facilities. Many DBs also had housing complexes, gymnasiums, and medical facilities intended to support the needs of their employees and their families.

The Soviet Union's LPRE development effort saw significant growth during the 1960s and reached its peak in the 1970s. This era coincided with the [[Cold War]] between the Soviet Union and the United States, characterised by intense competition in spaceflight achievements. Between 14 and 17 Design Bureaus and research institutes were actively involved in developing LPREs during this period. These organisations received relatively steady support and funding due to high military and [[Soviet space program|spaceflight priorities]], which facilitated the continuous development of new engine concepts and manufacturing methods.

Once a mission with a new vehicle (missile or spacecraft) was established it was passed on to a design bureau whose role was to oversee the development of the entire rocket. If none of the previously developed rocket engines met the needs of the mission, a new rocket engine with specific requirements would be contracted to another DB specialised in LPRE development (oftentimes each DB had expertise in specific types of LPREs with different applications, propellants, or engine sizes). This meant that the development or design study of a rocket engine was always aimed at a specific application which entailed set requirements.

When it comes to which DBs were awarded contracts for the development of new rocket engines either a single design bureau would be chosen or several design bureaus would be given the same contract which sometimes led to fierce competition between DBs.

When only one DB was picked for the development, it was often the result of the relationship between a vehicle or system's chief designer and the chief designer of a rocket engine specialised DB. If the vehicle's chief designer was happy with previous work done by a certain design bureau it was not unusual to see continued reliance on that LPRE bureau for that class of engines. For example, all but one of the LPREs for submarine-launched missiles were developed by the same design bureau for the same vehicle development prime contractor.

However, when two parallel engine development programs were supported in order to select the superior one for a specific application, several qualified rocket engine models were never used. This luxury of choice was not commonly available in other nations. However, the use of design bureaus also led to certain issues, including program cancellations and duplication. Some major programs were cancelled, resulting in the disposal or storage of previously developed engines.

One notable example of duplication and cancellation was the development of engines for the R-9A ballistic missile. Two sets of engines were supported, but ultimately only one set was selected, leaving several perfectly functional engines unused. Similarly, for the ambitious heavy N-l space launch vehicle intended for lunar and planetary missions, the Soviet Union developed and put into production at least two engines for each of the six stages. Additionally, they developed alternate engines for a more advanced N-l vehicle. However, the program faced multiple flight failures, and with the United States' successful [[Moon landing]], the program was ultimately cancelled, leaving the Soviet Union with a surplus of newly qualified engines without a clear purpose.

These examples demonstrate the complex dynamics and challenges faced by the Soviet Union in managing the development and production of rocket engines through Design Bureaus.

==== Accidents ====
The development of rocket engines in the Soviet Union was marked by significant achievements, but it also carried ethical considerations due to numerous accidents and fatalities. From a [[Science and technology studies|Science and Technology Studies]] point of view, the ethical implications of these incidents shed light on the complex relationship between technology, human factors, and the prioritisation of scientific advancement over safety.

The Soviet Union encountered a series of tragic accidents and mishaps in the development and operation of rocket engines. Notably, the USSR holds the unfortunate distinction of having experienced more injuries and deaths resulting from liquid propellant rocket engine (LPRE) accidents than any other country. These incidents brought into question the ethical considerations surrounding the development, testing, and operational use of rocket engines.

One of the most notable disasters occurred in 1960 when the [[R-16 (missile)|R-16]] ballistic missile suffered a catastrophic accident on the launchpad at the [[Töretam|Tyuratam]] launch facility. This incident resulted in the deaths of 124 engineers and military personnel, including Marshal M.I. Nedelin, a former deputy [[Minister of Defence (Soviet Union)|minister of defence]]. The explosion occurred after the second-stage rocket engine suddenly ignited, causing the fully loaded missile to disintegrate. The explosion resulted from the ignition and explosion of the mixed [[hypergolic propellant]]s, consisting of [[nitric acid]] with additives and [[Unsymmetrical dimethylhydrazine|UDMH]] (unsymmetrical dimethylhydrazine).

While the immediate cause of the 1960 accident was attributed to a lack of protective circuits in the missile control unit, the ethical considerations surrounding LPRE accidents in the USSR extend beyond specific technical failures. The secrecy surrounding these accidents, which remained undisclosed for approximately three decades, raises concerns about transparency, accountability, and the protection of human life.

The decision to keep fatal LPRE accidents hidden from the public eye reflects a broader ethical dilemma. The Soviet government, driven by the pursuit of scientific and technological superiority during the Cold War, sought to maintain an image of invincibility and conceal the failures that accompanied their advancements. This prioritisation of national prestige over the well-being and safety of workers raises questions about the ethical responsibility of the state and the organisations involved.

==Testing==

Rocket engines are usually statically tested at a [[rocket engine test facility|test facility]] before being put into production. For high altitude engines, either a shorter nozzle must be used, or the rocket must be tested in a large vacuum chamber.

==Safety==
[[Rocket]] vehicles have a reputation for unreliability and danger; especially catastrophic failures. Contrary to this reputation, carefully designed rockets can be made arbitrarily reliable.{{Citation needed|date=January 2017}} In military use, rockets are not unreliable. However, one of the main non-military uses of rockets is for orbital launch. In this application, the premium has typically been placed on minimum weight, and it is difficult to achieve high reliability and low weight simultaneously. In addition, if the number of flights launched is low, there is a very high chance of a design, operations or manufacturing error causing destruction of the vehicle.{{Citation needed|date=January 2017}}

===Saturn family (1961–1975)===
The [[Rocketdyne H-1]] engine, used in a cluster of eight in the first stage of the [[Saturn I]] and [[Saturn IB]] [[launch vehicle]]s, had no catastrophic failures in 152 engine-flights. The [[Pratt and Whitney]] [[RL10]] engine, used in a cluster of six in the Saturn I second stage, had no catastrophic failures in 36 engine-flights.{{refn|group=notes|name=RL10|The RL10 ''has'', however, experienced occasional failures (some of them catastrophic) in its other use cases, as the engine for the much-flown [[Centaur (rocket stage)|Centaur]] and [[Delta Cryogenic Second Stage|DCSS]] upper stages.}} The [[Rocketdyne F-1]] engine, used in a cluster of five in the first stage of the [[Saturn V]], had no failures in 65 engine-flights. The [[Rocketdyne J-2]] engine, used in a cluster of five in the Saturn V second stage, and singly in the Saturn IB second stage and Saturn V third stage, had no catastrophic failures in 86 engine-flights.{{refn|group=notes|name=J2fail|The J-2 had three premature in-flight shutdowns (two second-stage engine failures on [[Apollo 6]] and one on [[Apollo 13]]), and one failure to restart in orbit (the third-stage engine of Apollo 6). But these failures did not result in vehicle loss or mission abort (although the failure of Apollo 6's third-stage engine to restart ''would'' have forced a mission abort had it occurred on a crewed lunar mission).}}

===Space Shuttle (1981–2011)===
The [[Space Shuttle Solid Rocket Booster]], used in pairs, caused [[Space Shuttle Challenger disaster|one notable catastrophic failure]] in 270 engine-flights.

The [[RS-25]], used in a cluster of three, flew in 46 refurbished engine units. These made a total of 405 engine-flights with no catastrophic in-flight failures. A single in-flight [[RS-25]] engine failure occurred during {{OV|99}}'s [[STS-51-F]] mission.<ref name="P&WFS">{{cite web|url=http://www.pw.utc.com/products/pwr/assets/pwr_SSME.pdf |title=Space Shuttle Main Engine |publisher=Pratt & Whitney Rocketdyne |access-date=November 23, 2011 |year=2005 |url-status=dead |archive-url=https://web.archive.org/web/20120208191620/http://www.pw.utc.com/products/pwr/assets/pwr_SSME.pdf |archive-date=February 8, 2012 }}</ref> This failure had no effect on mission objectives or duration.<ref name="Hale">{{cite web|author=[[Wayne Hale]] & various|title=An SSME-related request|publisher=NASASpaceflight.com|access-date=January 17, 2012|date=January 17, 2012|url=http://forum.nasaspaceflight.com/index.php?topic=27783}}</ref>

==Cooling==
For efficiency reasons, higher temperatures are desirable, but materials lose their strength if the temperature becomes too high. Rockets run with combustion temperatures that can reach {{cvt|6,000|F|C K|-2}}.<ref name="HuzelAndHuang" />{{rp|98}}

Most other jet engines have gas turbines in the hot exhaust. Due to their larger surface area, they are harder to cool and hence there is a need to run the combustion processes at much lower temperatures, losing efficiency. In addition, [[wiktionary:duct engine|duct engines]] use air as an oxidant, which contains 78% largely unreactive nitrogen, which dilutes the reaction and lowers the temperatures.<ref name="Sutton" /> Rockets have none of these inherent combustion temperature limiters.

The temperatures reached by combustion in rocket engines often substantially exceed the melting points of the nozzle and combustion chamber materials (about 1,200 K for [[copper]]). Most construction materials will also combust if exposed to high temperature oxidiser, which leads to a number of design challenges. The nozzle and combustion chamber walls must not be allowed to combust, melt, or vaporize (sometimes facetiously termed an "engine-rich exhaust").

Rockets that use common construction materials such as aluminium, steel, nickel or copper alloys must employ cooling systems to limit the temperatures that engine structures experience. [[Regenerative cooling (rocket)|Regenerative cooling]], where the propellant is passed through tubes around the combustion chamber or nozzle, and other techniques, such as film cooling, are employed to give longer nozzle and chamber life. These techniques ensure that a gaseous thermal [[boundary layer]] touching the material is kept below the temperature which would cause the material to catastrophically fail.

Material exceptions that can sustain rocket combustion temperatures to a certain degree are [[Reinforced carbon–carbon|carbon–carbon materials]] and [[rhenium]], although both are subject to oxidation under certain conditions. Other [[refractory]] alloys, such as alumina, [[molybdenum]], [[tantalum]] or [[tungsten]] have been tried, but were given up on due to various issues.<ref name="RocketProp8">{{cite book |author=George P. Sutton |url=https://archive.org/details/Rocket_Propulsion_Elements_8th_Edition_by_Oscar_Biblarz_George_P._Sutton/page/308/mode/2up |title=Rocket Propulsion Elements |author2=Oscar Biblarz |date=2010 |publisher=Wiley Interscience |isbn=9780470080245 |edition=8th |page=308 |name-list-style=amp}}</ref>

Materials technology, combined with the engine design, is a limiting factor in chemical rockets.

In rockets, the [[heat flux]]es that can pass through the wall are among the highest in engineering; fluxes are generally in the range of 0.8–80 MW/m{{sup|2}} (0.5-50 [[BTU]]/in{{sup|2}}-sec).<ref name="HuzelAndHuang" />{{rp|98}} The strongest heat fluxes are found at the throat, which often sees twice that found in the associated chamber and nozzle. This is due to the combination of high speeds (which gives a very thin boundary layer), and although lower than the chamber, the high temperatures seen there. (See {{section link||Nozzle}} above for temperatures in nozzle).

In rockets the coolant methods include:<ref name="HuzelAndHuang" />{{rp|98–99}}

#[[ablation|Ablative]]: The combustion chamber inside walls are lined with a material that traps heat and carries it away with the exhaust as it vaporizes.
#[[Radiative cooling]]: The engine is made of one or several [[refractory]] materials, which take heat flux until its outer thrust chamber wall glows red- or white-hot, radiating the heat away.
#Dump cooling: A cryogenic propellant, usually [[hydrogen]], is passed around the nozzle and dumped. This cooling method has various issues, such as wasting propellant. It is only used rarely.
#[[regenerative cooling (rocket)|Regenerative cooling]]: The fuel (and possibly, the oxidiser) of a [[liquid rocket engine]] is routed around the nozzle before being injected into the combustion chamber or preburner. This is the most widely applied method of rocket engine cooling.
#Film cooling: The engine is designed with rows of multiple orifices lining the inside wall through which additional propellant is injected, cooling the chamber wall as it evaporates. This method is often used in cases where the heat fluxes are especially high, likely in combination with [[regenerative cooling (rocket)|regenerative cooling]]. A more efficient subtype of film cooling is [[transpiration cooling]], in which propellant passes through a [[porous]] inner combustion chamber wall and transpirates. So far, this method has not seen usage due to various issues with this concept.

Rocket engines may also use several cooling methods. Examples:

* Regeneratively and film cooled combustion chamber and nozzle: [[V-2 rocket|V-2]] Rocket Engine<ref>{{cite web |title=Raketenmotor der A4 (V2)-Rakete |url=https://www.deutsches-museum.de/flugwerft-schleissheim/ausstellung/flugantriebe-und-raketen/raketenmotor-a-4 |access-date=19 September 2022 |language=de |quote=An additional coolant line takes alcohol to fine holes in the inner chamber wall. The alcohol flows alongside the wall, creating a thin, evaporating film for additional cooling.}}</ref>
* Regeneratively cooled combustion chamber with a film cooled nozzle extension: [[Rocketdyne F-1|Rocketdyne F-1 Engine]]<ref>{{cite web |author=McCutcheon, Kimble D. |date=3 August 2022 |title=U.S. Manned Rocket Propulsion Evolution Part 8.12: Rocketdyne F-1 Engine Description |url=https://www.enginehistory.org/Rockets/RPE08.11/RPE08.12.shtml |access-date=19 September 2022}}</ref>
* Regeneratively cooled combustion chamber with an ablatively cooled nozzle extension: The [[LR-91]] rocket engine<ref>{{cite web |author=McCutcheon, Kimble D. |date=3 August 2022 |title=U.S. Manned Rocket Propulsion Evolution Part 6: The Titan Missile |url=https://www.enginehistory.org/Rockets/RPE06/RPE06.shtml |access-date=19 September 2022}}</ref>
* Ablatively and film cooled combustion chamber with a radiatively cooled nozzle extension: [[Lunar module descent engine]] (LMDE), [[Apollo command and service module#Service propulsion system|Service propulsion system engine]] (SPS)<ref>{{cite book |last=Bartlett |first=W. |url=https://ntrs.nasa.gov/api/citations/19700026405/downloads/19700026405.pdf |title=Apollo spacecraft liquid primary propulsion systems |last2=Kirkland |first2=Z. D. |last3=Polifka |first3=R. W. |last4=Smithson |first4=J. C. |last5=Spencer |first5=G. L. |date=7 February 1966 |publisher=NASA, Lyndon B. Johnson Space Center |location=Houston, TX |pages=8 |archive-url=https://web.archive.org/web/20220823092501/https://ntrs.nasa.gov/api/citations/19700026405/downloads/19700026405.pdf |archive-date=23 August 2022 |access-date=10 September 2022 |url-status=bot: unknown }}</ref>
* Radiatively and film cooled combustion chamber with a radiatively cooled nozzle extension: [[Deep Space Industries|Deep space]] storable propellant thrusters<ref name="RocketProp8" />

In all cases, another effect that aids in cooling the rocket engine chamber wall is a thin layer of combustion gases (a [[boundary layer]]) that is notably cooler than the combustion temperature. Disruption of the boundary layer may occur during cooling failures or combustion instabilities, and wall failure typically occurs soon after.

With regenerative cooling a second boundary layer is found in the coolant channels around the chamber. This boundary layer thickness needs to be as small as possible, since the boundary layer acts as an insulator between the wall and the coolant. This may be achieved by making the coolant [[velocity]] in the channels as high as possible.<ref name="HuzelAndHuang" />{{rp|105–106}}

Liquid-fuelled engines are often run [[Air-fuel ratio|fuel-rich]], which lowers combustion temperatures. This reduces heat loads on the engine and allows lower cost materials and a simplified cooling system. This can also ''increase'' performance by lowering the average molecular weight of the exhaust and increasing the efficiency with which combustion heat is converted to kinetic exhaust energy.

==Chemistry==
[[Rocket propellant]]s require a high energy per unit mass ([[specific energy]]), which must be balanced against the tendency of highly energetic propellants to spontaneously explode. Assuming that the chemical potential energy of the propellants can be safely stored, the combustion process results in a great deal of heat being released. A significant fraction of this heat is transferred to kinetic energy in the engine nozzle, propelling the rocket forward in combination with the mass of combustion products released.

Ideally all the reaction energy appears as kinetic energy of the exhaust gases, as exhaust velocity is the single most important performance parameter of an engine. However, real exhaust species are [[molecule]]s, which typically have translation, vibrational, and [[rotational modes]] with which to dissipate energy. Of these, only translation can do useful work to the vehicle, and while energy does transfer between modes this process occurs on a timescale far in excess of the time required for the exhaust to leave the nozzle.

The more [[chemical bond]]s an exhaust molecule has, the more rotational and vibrational modes it will have. Consequently, it is generally desirable for the exhaust species to be as simple as possible, with a diatomic molecule composed of light, abundant atoms such as H2 being ideal in practical terms. However, in the case of a chemical rocket, hydrogen is a reactant and [[reducing agent]], not a product. An [[oxidizing agent]], most typically oxygen or an oxygen-rich species, must be introduced into the combustion process, adding mass and chemical bonds to the exhaust species.

An additional advantage of light molecules is that they may be accelerated to high velocity at temperatures that can be contained by currently available materials - the high gas temperatures in rocket engines pose serious problems for the engineering of survivable motors.

Liquid [[hydrogen]] (LH2) and [[oxygen]] (LOX, or LO2), are the most effective propellants in terms of exhaust velocity that have been widely used to date, though a few exotic combinations involving boron or liquid ozone are potentially somewhat better in theory if various practical problems could be solved.<ref>[http://yarchive.net/space/rocket/fuels/fuel_ratio.html Newsgroup correspondence], 1998–99</ref>

When computing the specific reaction energy of a given propellant combination, the entire mass of the propellants (both fuel and oxidiser) must be included. The exception is in the case of air-breathing engines, which use atmospheric oxygen and consequently have to carry less mass for a given energy output. Fuels for car or [[turbojet engine]]s have a much better effective energy output per unit mass of propellant that must be carried, but are similar per unit mass of fuel.

Computer programs that predict the performance of propellants in rocket engines are available.<ref>[http://rocketworkbench.sourceforge.net/equil.phtml Complex chemical equilibrium and rocket performance calculations], Cpropep-Web</ref><ref>[http://propulsion-analysis.com/ Tool for Rocket Propulsion Analysis], RPA</ref><ref>[https://web.archive.org/web/20000901045039/http://www.grc.nasa.gov/WWW/CEAWeb/ NASA Computer program Chemical Equilibrium with Applications], CEA</ref>

==Ignition==
{{Further|Combustion}}
With liquid and hybrid rockets, immediate ignition of the propellants as they first enter the combustion chamber is essential.

With liquid propellants (but not gaseous), failure to ignite within milliseconds usually causes too much liquid propellant to be inside the chamber, and if/when ignition occurs the amount of hot gas created can exceed the maximum design pressure of the chamber, causing a catastrophic failure of the pressure vessel. This is sometimes called a ''[[hard start]]'' or a ''rapid unscheduled disassembly'' (RUD).<ref name=aw20121126>
{{cite news |last=Svitak|first=Amy |title=Falcon 9 RUD? |url=http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385Post:c973f72f-55d3-4374-b722-df31a8d333e6 |archive-url=https://web.archive.org/web/20140321053215/http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385Post:c973f72f-55d3-4374-b722-df31a8d333e6 |url-status=dead |archive-date=2014-03-21 |access-date=2014-03-21 |newspaper=Aviation Week |date=2012-11-26 }}</ref>

Ignition can be achieved by a number of different methods; a pyrotechnic charge can be used, a plasma torch can be used,{{citation needed|date=October 2016}} or electric spark ignition<ref name=nsf20161003>
{{cite news |last=Belluscio|first=Alejandro G. |title=ITS Propulsion – The evolution of the SpaceX Raptor engine |work=[[NASASpaceFlight.com]] |date=2016-10-03 |url=https://www.nasaspaceflight.com/2016/10/its-propulsion-evolution-raptor-engine/ |access-date=2016-10-03 }}</ref> may be employed. Some fuel/oxidiser combinations ignite on contact ([[hypergolic]]), and non-hypergolic fuels can be "chemically ignited" by priming the fuel lines with hypergolic propellants (popular in Russian engines).

Gaseous propellants generally will not cause [[hard start]]s, with rockets the total injector area is less than the throat thus the chamber pressure tends to ambient prior to ignition and high pressures cannot form even if the entire chamber is full of flammable gas at ignition.

Solid propellants are usually ignited with one-shot pyrotechnic devices and combustion usually proceeds through total consumption of the propellants.<ref name=Sutton/>

Once ignited, rocket chambers are self-sustaining and igniters are not needed and combustion usually proceeds through total consumption of the propellants. Indeed, chambers often spontaneously reignite if they are restarted after being shut down for a few seconds. Unless designed for re-ignition, when cooled, many rockets cannot be restarted without at least minor maintenance, such as replacement of the pyrotechnic igniter or even refueling of the propellants.<ref name=Sutton/>

==Jet physics==
[[File:Armadillo Aerospace Pixel Hover.jpg|thumb|right|[[Quad (rocket)|Armadillo Aerospace's quad vehicle]] showing visible banding (shock diamonds) in the exhaust jet]]
Rocket jets vary depending on the rocket engine, design altitude, altitude, thrust and other factors.

Carbon-rich exhausts from kerosene-based fuels such as [[RP-1]] are often orange in colour due to the [[black-body radiation]] of the unburnt particles, in addition to the blue [[Swan band]]s. [[high test peroxide|Peroxide]] oxidiser-based rockets and hydrogen rocket jets contain largely [[steam]] and are nearly invisible to the naked eye but shine brightly in the [[ultraviolet]] and [[infrared]] ranges. Jets from [[solid-propellant rocket]]s can be highly visible, as the propellant frequently contains metals such as elemental aluminium which burns with an orange-white flame and adds energy to the combustion process. Rocket engines which burn liquid hydrogen and oxygen will exhibit a nearly transparent exhaust, due to it being mostly [[superheated steam]] (water vapour), plus some unburned hydrogen.

The nozzle is usually over-expanded at sea level, and the exhaust can exhibit visible [[shock diamonds]] through a [[schlieren#Schlieren flow visualization|schlieren effect]] caused by the [[incandescence]] of the exhaust gas.

The shape of the jet varies for a fixed-area nozzle as the expansion ratio varies with altitude: at high altitude all rockets are grossly under-expanded, and a quite small percentage of exhaust gases actually end up expanding forwards.

==Types of rocket engines==

===Physically powered===
{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Water rocket]]
| Partially filled pressurised carbonated drinks container with tail and nose weighting
| Very simple to build
| Altitude typically limited to a few hundred feet or so (world record is 830 meters, or 2,723 feet)
|-
! [[Cold gas thruster]]
| A non-combusting form, used for [[vernier thruster]]s
| Non-contaminating exhaust
| Extremely low performance
|}

===Chemically powered===
{{See also|Liquid rocket propellant}}

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Solid-propellant rocket]]
| Ignitable, self-sustaining solid fuel/oxidiser mixture ("grain") with central hole and nozzle
| Simple, often no [[moving parts]], reasonably good mass fraction, reasonable [[Specific Impulse|''I''sp]]. A thrust schedule can be designed into the grain.
| Throttling, burn termination, and reignition require special designs. Handling issues from ignitable mixture. Lower performance than liquid rockets. If grain cracks it can block nozzle with disastrous results. Grain cracks burn and widen during burn. Refueling harder than simply filling tanks. Cannot be turned off after ignition; will fire until all solid fuel is depleted.
|-
! [[Hybrid-propellant rocket]]
| Separate oxidiser/fuel; typically the oxidiser is liquid and kept in a tank and the fuel is solid.
| Quite simple, solid fuel is essentially inert without oxidiser, safer; cracks do not escalate, throttleable and easy to switch off.
| Some oxidisers are monopropellants, can explode in own right; mechanical failure of solid propellant can block nozzle (very rare with rubberised propellant), central hole widens over burn and negatively affects mixture ratio.
|-
! [[Monopropellant rocket]]
| Propellant (such as hydrazine, hydrogen peroxide or nitrous oxide) flows over a catalyst and exothermically decomposes; hot gases are emitted through nozzle.
| Simple in concept, throttleable, low temperatures in combustion chamber
| Catalysts can be easily contaminated, monopropellants can detonate if contaminated or provoked, [[Specific Impulse|''I''sp]] is perhaps 1/3 of best liquids
|-
! [[Liquid bipropellant rocket engine|Bipropellant rocket]]
| Two fluid (typically liquid) propellants are introduced through injectors into combustion chamber and burnt.
| Up to ~99% efficient combustion with excellent mixture control, throttleable, can be used with turbopumps which permits incredibly lightweight tanks, can be safe with extreme care
| Pumps needed for high performance are expensive to design, huge thermal fluxes across combustion chamber wall can impact reuse, failure modes include major explosions, a lot of plumbing is needed.
|-
! [[Methane-oxygen gaseous thruster|Gas-gas rocket]]
| A bipropellant thruster using gas propellant for both the oxidiser and fuel
| Higher-performance than cold gas thrusters
| Lower performance than liquid-based engines
|-
! [[Dual mode propulsion rocket]]
| Rocket takes off as a bipropellant rocket, then turns to using just one propellant as a monopropellant.
| Simplicity and ease of control
| Lower performance than bipropellants
|-
! [[Tripropellant rocket]]
| Three different propellants (usually hydrogen, hydrocarbon, and liquid oxygen) are introduced into a combustion chamber in variable mixture ratios, or multiple engines are used with fixed propellant mixture ratios and throttled or shut down
| Reduces take-off weight, since hydrogen is lighter; combines good thrust to weight with high average [[specific impulse|''I''sp]], improves payload for launching from Earth by a sizeable percentage
| Similar issues to bipropellant, but with more plumbing, more research and development
|-
! [[Air-augmented rocket]]
| Essentially a ramjet where intake air is compressed and burnt with the exhaust from a rocket
| Mach 0 to Mach 4.5+ (can also run exoatmospheric), good efficiency at Mach 2 to 4
| Similar efficiency to rockets at low speed or exoatmospheric, inlet difficulties, a relatively undeveloped and unexplored type, cooling difficulties, very noisy, thrust/weight ratio is similar to ramjets.
|-
! [[Turborocket]]
| A combined cycle turbojet/rocket where an additional oxidiser such as oxygen is added to the airstream to increase maximum altitude
| Very close to existing designs, operates in very high altitude, wide range of altitude and airspeed
| Atmospheric airspeed limited to same range as turbojet engine, carrying oxidiser like [[LOX]] can be dangerous. Much heavier than simple rockets.
|-
! [[Precooled jet engine]] / [[liquid air cycle engine|LACE]] (combined cycle with rocket)
| Intake air is chilled to very low temperatures at inlet before passing through a ramjet or turbojet engine. Can be combined with a rocket engine for orbital insertion.
| Easily tested on ground. High thrust/weight ratios are possible (~14) together with good fuel efficiency over a wide range of airspeeds, mach 0–5.5+; this combination of efficiencies may permit launching to orbit, single stage, or very rapid intercontinental travel.
| Exists only at the lab prototyping stage. Examples include [[RB545]], [[Reaction Engines SABRE|SABRE]], [[ATREX]]
|}

===Electrically powered===
{{Main|Electrically powered spacecraft propulsion}}
{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Resistojet rocket]] (electric heating)
| Energy is imparted to a usually inert fluid serving as reaction mass via [[Joule heating]] of a heating element. May also be used to impart extra energy to a monopropellant.
| Efficient where electrical power is at a lower premium than mass. Higher [[specific impulse|''I''sp]] than monopropellant alone, about 40% higher.
| Requires a lot of power, hence typically yields low thrust.
|-
! [[Arcjet rocket]] (chemical burning aided by electrical discharge)
| Identical to resistojet except the heating element is replaced with an electrical arc, eliminating the physical requirements of the heating element.
| 1,600 seconds [[specific impulse|''I''sp]]
| Very low thrust and high power, performance is similar to [[ion drive]].
|-
![[Variable specific impulse magnetoplasma rocket]]
| Microwave heated plasma with magnetic throat/nozzle
| Variable ''I''sp from 1,000 seconds to 10,000 seconds
| Similar thrust/weight ratio with ion drives (worse), thermal issues, as with ion drives very high power requirements for significant thrust, really needs advanced nuclear reactors, never flown, requires low temperatures for superconductors to work
|-
! [[Pulsed plasma thruster]] (electric arc heating; emits plasma)
| Plasma is used to erode a solid propellant
| High ''I''sp, can be pulsed on and off for attitude control
| Low energetic efficiency
|-
! [[Ion thruster|Ion propulsion system]]
| High voltages at ground and plus sides
| Powered by battery
| Low thrust, needs high voltage
|}

===Thermal===

====Preheated====
{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Hot water rocket]]
| Hot water is stored in a tank at high temperature / pressure and turns to steam in nozzle
| Simple, fairly safe
| Low overall performance due to heavy tank; [[specific impulse|''I''sp]] under 200 seconds
|}

====Solar thermal====

The [[solar thermal rocket]] would make use of solar power to directly heat [[reaction mass]], and therefore does not require an electrical generator as most other forms of solar-powered propulsion do. A solar thermal rocket only has to carry the means of capturing solar energy, such as [[Concentrating solar power|concentrator]]s and [[mirror]]s. The heated propellant is fed through a conventional rocket nozzle to produce thrust. The engine thrust is directly related to the surface area of the solar collector and to the local intensity of the solar radiation and inversely proportional to the ''I''sp.

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Solar thermal rocket]]
| Propellant is heated by solar collector
| Simple design. Using hydrogen propellant, 900 seconds of [[specific impulse|''I''sp]] is comparable to nuclear thermal rocket, without the problems and complexity of controlling a fission reaction.{{citation needed|date=January 2011}} Ability to [[Solar thermal rocket#Proposed solar-thermal space systems|productively use]] waste gaseous [[hydrogen]]—an inevitable byproduct of long-term [[liquid hydrogen]] storage in the [[Radiative heat transfer|radiative heat]] environment of space—for both [[orbital stationkeeping]] and [[Spacecraft attitude control|attitude control]].<ref name=aiaa20100902>{{cite web|last=Zegler|first=Frank |title=Evolving to a Depot-Based Space Transportation Architecture |url=http://www.ulalaunch.com/site/docs/publications/DepotBasedTransportationArchitecture2010.pdf |archive-url=https://web.archive.org/web/20110717150155/http://www.ulalaunch.com/site/docs/publications/DepotBasedTransportationArchitecture2010.pdf |url-status=dead |archive-date=2011-07-17 |work=AIAA SPACE 2010 Conference & Exposition |publisher=AIAA |access-date=2011-01-25 |author2=Bernard Kutter |date=2010-09-02 }} See page 3.</ref>
| Only useful in space, as thrust is fairly low, but hydrogen has not been traditionally thought to be easily stored in space,<ref name=aiaa20100902/> otherwise moderate/low [[Specific impulse|''I''sp]] if higher–molecular-mass propellants are used.
|}

====Beamed thermal====

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Laser propulsion|Light-beam-powered rocket]]
| Propellant is heated by light beam (often laser) aimed at vehicle from a distance, either directly or indirectly via heat exchanger
| Simple in principle, in principle very high exhaust speeds can be achieved
| ~1 MW of power per kg of payload is needed to achieve orbit, relatively high accelerations, lasers are blocked by clouds, fog, reflected laser light may be dangerous, pretty much needs hydrogen monopropellant for good performance which needs heavy tankage, some designs are limited to ~600 seconds due to reemission of light since propellant/heat exchanger gets white hot
|-
! [[Beam-powered propulsion|Microwave-beam-powered rocket]]
| Propellant is heated by microwave beam aimed at vehicle from a distance
| [[Specific impulse|''I''sp]] is comparable to Nuclear Thermal rocket combined with T/W comparable to conventional rocket. While LH2 propellant offers the highest Isp and rocket payload fraction, ammonia or methane are economically superior for earth-to-orbit rockets due to their particular combination of high density and Isp. [[Single-stage-to-orbit|SSTO]] operation is possible with these propellants even for small rockets, so there are no location, trajectory and shock constraints added by the rocket staging process. Microwaves are 10-100× cheaper in $/watt than lasers and have all-weather operation at frequencies below 10 GHz.
| 0.3–3{{nbsp}}MW of power per kg of payload is needed to achieve orbit depending on the propellant,<ref>{{cite web|url=http://parkinresearch.com/microwave-thermal-rockets/|title=Microwave Thermal Rockets|last=Parkin|first=Kevin|access-date=8 December 2016}}</ref> and this incurs infrastructure cost for the beam director plus related R&D costs. Concepts operating in the millimeter-wave region have to contend with weather availability and high altitude beam director sites as well as effective transmitter diameters measuring 30–300 meters to propel a vehicle to LEO. Concepts operating in X-band or below must have effective transmitter diameters measured in kilometers to achieve a fine enough beam to follow a vehicle to LEO. The transmitters are too large to fit on mobile platforms and so microwave-powered rockets are constrained to launch near fixed beam director sites.
|}

====Nuclear thermal====

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Radioisotope rocket|Radioisotope rocket/"Poodle thruster"]] (radioactive decay energy)
| Heat from radioactive decay is used to heat hydrogen
| About 700–800 seconds, almost no moving parts
| Low thrust/weight ratio.
|-
! [[Nuclear thermal rocket]] (nuclear fission energy)
| Propellant (typically, hydrogen) is passed through a nuclear reactor to heat to high temperature
| [[Specific impulse|''I''sp]] can be high, perhaps 900 seconds or more, above unity thrust/weight ratio with some designs
| Maximum temperature is limited by materials technology, some radioactive particles can be present in exhaust in some designs, nuclear reactor shielding is heavy, unlikely to be permitted from surface of the Earth, thrust/weight ratio is not high.
|}

===Nuclear===
[[Nuclear propulsion]] includes a wide variety of [[spacecraft propulsion|propulsion]] methods that use some form of [[nuclear reaction]] as their primary power source. Various types of nuclear propulsion have been proposed, and some of them tested, for spacecraft applications:

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Gas core reactor rocket]] (nuclear fission energy)
| Nuclear reaction using a gaseous state fission reactor in intimate contact with propellant
| Very hot propellant, not limited by keeping reactor solid, [[Specific Impulse|''I''sp]] between 1,500 and 3,000 seconds but with very high thrust
| Difficulties in heating propellant without losing fissionables in exhaust, massive thermal issues particularly for nozzle/throat region, exhaust almost inherently highly radioactive. Nuclear lightbulb variants can contain fissionables, but cut [[Specific Impulse|''I''sp]] in half.
|-
! [[Fission-fragment rocket]] (nuclear fission energy)
| Fission products are directly exhausted to give thrust.
|
| Theoretical only at this point.
|-
! [[Fission sail]] (nuclear fission energy)
| A sail material is coated with fissionable material on one side.
| No moving parts, works in deep space
| Theoretical only at this point.
|-
! [[Nuclear salt-water rocket]] (nuclear fission energy)
| Nuclear salts are held in solution, caused to react at nozzle
| Very high [[Specific Impulse|''I''sp]], very high thrust
| Thermal issues in nozzle, propellant could be unstable, highly radioactive exhaust. Theoretical only at this point.
|-
! [[Nuclear pulse propulsion]] (exploding fission/fusion bombs)
| Shaped nuclear bombs are detonated behind vehicle and blast is caught by a 'pusher plate'
| Very high [[Specific Impulse|''I''sp]], very high thrust/weight ratio, no show stoppers are known for this technology.
| Never been tested, pusher plate may [[spall|throw off fragments]] due to shock, minimum size for nuclear bombs is still pretty big, expensive at small scales, nuclear treaty issues, fallout when used below Earth's magnetosphere.
|-
! [[Antimatter catalyzed nuclear pulse propulsion]] (fission and/or fusion energy)
| Nuclear pulse propulsion with antimatter assist for smaller bombs
| Smaller sized vehicle might be possible
| Containment of antimatter, production of antimatter in macroscopic quantities is not currently feasible. Theoretical only at this point.
|-
! [[Fusion rocket]] (nuclear fusion energy)
| Fusion is used to heat propellant
| Very high exhaust velocity
| Largely beyond current state of the art.
|-
! [[Antimatter rocket]] (annihilation energy)
| Antimatter annihilation heats propellant
| Extremely energetic, very high theoretical exhaust velocity
| Problems with antimatter production and handling; energy losses in [[neutrino]]s, [[gamma ray]]s, [[muon]]s; thermal issues. Theoretical only at this point.
|}

==History of rocket engines==
{{main|History of rockets}}
According to the writings of the Roman [[Aulus Gellius]], the earliest known example of [[jet propulsion]] was in c. 400 BC, when a [[Greek people|Greek]] [[Pythagoreanism|Pythagorean]] named [[Archytas]], propelled a wooden bird along wires using steam.<ref>{{cite book |author=Leofranc Holford-Strevens|title=Aulus Gellius: An Antonine Author and his Achievement|publisher=Oxford University Press|edition=Revised paperback |date=2005 |isbn=0-19-928980-8 }}
</ref><ref>{{cite EB1911 |wstitle=Archytas |volume=2 |page=446}}</ref> However, it was not powerful enough to take off under its own thrust.

The ''[[aeolipile]]'' described in the first century BC, often known as ''[[Hero's engine]]'', consisted of a pair of [[steam rocket]] nozzles mounted on a [[Bearing (mechanical)|bearing]]. It was created almost two millennia before the [[Industrial Revolution]] but the principles behind it were not well understood, and it was not developed into a practical power source.

The availability of [[black powder]] to propel projectiles was a precursor to the development of the first solid rocket. Ninth Century [[Chinese people|Chinese]] [[Taoist]] [[Alchemy|alchemists]] discovered black powder in a search for the [[elixir of life]]; this accidental discovery led to [[fire arrow]]s which were the first rocket engines to leave the ground.

It is stated{{By whom|date=May 2022}} that "the reactive forces of incendiaries were probably not applied to the propulsion of projectiles prior to the 13th century".{{Citation needed|date=May 2024}} A turning point in rocket technology emerged with a short manuscript entitled ''Liber Ignium ad Comburendos Hostes'' (abbreviated as ''The Book of Fires''). The manuscript is composed of recipes for creating incendiary weapons from the mid-eighth to the end of the thirteenth centuries—two of which are rockets. The first recipe calls for one part of colophonium and sulfur added to six parts of saltpeter (potassium nitrate) dissolved in [[Lauraceae|laurel]] oil, then inserted into hollow wood and lit to "fly away suddenly to whatever place you wish and burn up everything". The second recipe combines one pound of sulfur, two pounds of charcoal, and six pounds of saltpeter—all finely powdered on a marble slab. This powder mixture is packed firmly into a long and narrow case. The introduction of saltpeter into pyrotechnic mixtures connected the shift from hurled [[Greek fire]] into self-propelled rocketry.<ref>{{cite book|last1=Von Braun|last2= Ordway III|first1=Wernher |first2= Frederick I.|title=The Rockets' Red Glare|url=https://archive.org/details/rocketsredglare0000vonb|url-access=registration|date=1976|publisher=Anchor Press/ Doubleday|location=Garden City, New York|isbn=978-0-385-07847-4|page=[https://archive.org/details/rocketsredglare0000vonb/page/5 5]}}</ref>

Articles and books on the subject of rocketry appeared increasingly from the fifteenth through seventeenth centuries. In the sixteenth century, German military engineer Conrad Haas (1509–1576) wrote a manuscript which introduced the construction of multi-staged rockets.<ref>{{cite book|last1=Von Braun|last2= Ordway III|first1=Wernher |first2= Frederick I.|title=The Rockets' Red Glare|url=https://archive.org/details/rocketsredglare0000vonb|url-access=registration|date=1976|publisher=Anchor Press/ Doubleday|location=Garden City, New York|isbn=978-0-385-07847-4|page=[https://archive.org/details/rocketsredglare0000vonb/page/11 11]}}</ref>

Rocket engines were also put in use by [[Tippu Sultan]], the king of [[Mysore]]. These usually consisted of a tube of soft hammered iron about {{convert|8|in|cm|abbr=on}} long and {{convert|1+1/2|-|3|in|cm|abbr=on}} diameter, closed at one end, packed with black powder propellant and strapped to a shaft of bamboo about {{convert|4|ft|cm|abbr=on}} long. A rocket carrying about one pound of powder could travel almost {{convert|1000|yd|m}}. These 'rockets', fitted with swords, would travel several meters in the air before coming down with sword edges facing the enemy. These were used very effectively against the British empire.

===Modern rocketry===
Slow development of this technology continued up to the later 19th century, when Russian [[Konstantin Tsiolkovsky]] first wrote about [[liquid-propellant rocket|liquid-fuelled rocket engines]]. He was the first to develop the [[Tsiolkovsky rocket equation]], though it was not published widely for some years.

The modern solid- and liquid-fuelled engines became realities early in the 20th century, thanks to the American physicist [[Robert Goddard (scientist)|Robert Goddard]]. Goddard was the first to use a [[De Laval nozzle]] on a solid-propellant (gunpowder) rocket engine, doubling the thrust and increasing the efficiency by a factor of about twenty-five. This was the birth of the modern rocket engine. He calculated from his independently derived rocket equation that a reasonably sized rocket, using solid fuel, could place a one-pound payload on the Moon.

===The era of liquid-fuel rocket engines===
Goddard began to use liquid propellants in 1921, and in 1926 became the first to launch a liquid-fuelled rocket. Goddard pioneered the use of the De Laval nozzle, lightweight propellant tanks, small light turbopumps, thrust vectoring, the smoothly-throttled liquid fuel engine, regenerative cooling, and curtain cooling.<ref name=Sutton/>{{rp|247–266}}

During the late 1930s, German scientists, such as [[Wernher von Braun]] and [[Hellmuth Walter]], investigated installing liquid-fuelled rockets in military aircraft ([[Heinkel He 112]], [[Heinkel He 111|He 111]], [[Heinkel He 176|He 176]] and [[Messerschmitt Me 163]]).<ref>{{cite book|author=Lutz Warsitz|title=The First Jet Pilot – The Story of German Test Pilot Erich Warsitz|publisher=Pen and Sword Ltd.|date=2009|isbn=978-1-84415-818-8}} Includes von Braun's and Hellmuth Walter's experiments with rocket aircraft. [http://www.pen-and-sword.co.uk/?product_id=1762 English edition.]</ref>

The turbopump was employed by German scientists in World War II. Until then cooling the nozzle had been problematic, and the [[V-2 rocket|A4]] ballistic missile used dilute alcohol for the fuel, which reduced the combustion temperature sufficiently.

[[Staged combustion cycle (rocket)|Staged combustion]] (''Замкнутая схема'') was first proposed by [[Aleksei Mihailovich Isaev|Alexey Isaev]] in 1949. The first staged combustion engine was the S1.5400 used in the Soviet planetary rocket, designed by Melnikov, a former assistant to Isaev.<ref name=Sutton>{{cite book|last=Sutton|first=George P.|title=History of Liquid Propellant Rocket Engines|date=2005|publisher=American Institute of Aeronautics and Astronautics|location=Reston, Virginia}}</ref> About the same time (1959), [[Nikolai Dmitriyevich Kuznetsov|Nikolai Kuznetsov]] began work on the closed cycle engine [[NK-9]] for Korolev's orbital ICBM, GR-1. Kuznetsov later evolved that design into the [[NK-15]] and [[NK-33]] engines for the unsuccessful Lunar [[N1 rocket]].

In the West, the first laboratory staged-combustion test engine was built in Germany in 1963, by [[Ludwig Boelkow]].

Liquid hydrogen engines were first successfully developed in America: the [[RL-10]] engine first flew in 1962. Its successor, the [[Rocketdyne J-2]], was used in the [[Apollo program]]'s [[Saturn V]] rocket to send humans to the Moon. The high specific impulse and low density of liquid hydrogen lowered the upper stage mass and the overall size and cost of the vehicle.

The record for most engines on one rocket flight is 44, set by NASA in 2016 on a [[Black Brant (rocket)|Black Brant]].<ref>{{Cite web | url=https://www.space.com/33810-nasa-world-record-most-rocket-engines.html |title = NASA and Navy Set World Record for Most Engines in One Rocket Flight|website = [[Space.com]]|date = 19 August 2016}}</ref>

==See also==
* [[Comparison of orbital rocket engines]]
* [[Rotating detonation engine]]
* [[Jet damping]], an effect of the exhaust jet of a rocket that tends to slow a vehicle's rotation speed
* [[Model rocket motor classification]] lettered engines
* [[NERVA]] (Nuclear Energy for Rocket Vehicle Applications), a US nuclear thermal rocket programme
* [[Photon rocket]]
* [[Project Prometheus]], NASA development of nuclear propulsion for long-duration spaceflight, begun in 2003
* [[Rocket propulsion technologies (disambiguation)]]

==Notes==
{{reflist|group =notes}}

==References==
{{reflist}}

==External links==
{{commons category|Rocket engines}}
{{Wiktionary}}
*[https://web.archive.org/web/20071009153749/http://www.pwrengineering.com/articles/longterm.htm Designing for rocket engine life expectancy]
*[https://web.archive.org/web/20071007070232/http://www.pwrengineering.com/articles/plume.htm Rocket Engine performance analysis with Plume Spectrometry]
*[https://web.archive.org/web/20071009151907/http://www.pwrengineering.com/articles/heart.htm Rocket Engine Thrust Chamber technical article]
*[http://www.fxsolver.com/browse/formulas/Net+Thrust+of+a+Rocket+Engine Net Thrust of a Rocket Engine calculator]
*[http://www.lpre.de/resources/software/RPA_en.htm Design Tool for Liquid Rocket Engine Thermodynamic Analysis]
*[http://www.braeunig.us/space/propuls.htm Rocket & Space Technology - Rocket Propulsion]
*[http://www.erichwarsitz.com/ The official website of test pilot Erich Warsitz (world's first jet pilot) which includes videos of the Heinkel He 112 fitted with von Braun's and Hellmuth Walter's rocket engines (as well as the He 111 with ATO Units)]

{{Rocket engines}}
{{Aircraft gas turbine engine components}}
{{Heat engines|state=uncollapsed}}

{{Authority control}}

{{DEFAULTSORT:Rocket Engine}}
[[Category:Aerospace technologies]]
[[Category:Rocket engines| ]]

Rocket engine

2024-08-17T16:45:31Z

88.163.124.35: /* Combustion instabilities */ to F-1 engines

{{Short description|Non-air breathing jet engine used to propel a missile or vehicle}}
{{Use British English|date=February 2019}}
[[File:RS-68 rocket engine test.jpg|thumb|right|[[RS-68]] being tested at NASA's [[Stennis Space Center]]]]
[[File:Viking 5C rocketengine.jpg|thumb|right|[[Viking (rocket engine)|Viking 5C rocket engine]] used on [[Ariane 1]] through [[Ariane 4]]]]

A '''rocket engine''' uses stored [[rocket propellant]]s as the [[reaction mass]] for forming a high-speed propulsive [[Jet (fluid)|jet]] of fluid, usually high-temperature gas. [[Rocket]] engines are [[reaction engine]]s, producing thrust by ejecting mass rearward, in accordance with [[Newton's third law]]. Most rocket engines use the [[combustion]] of reactive chemicals to supply the necessary energy, but non-combusting forms such as [[cold gas thruster]]s and [[nuclear thermal rocket]]s also exist. Vehicles propelled by rocket engines are commonly used by [[ballistic missiles]] (they normally use [[solid fuel]]) and [[rocket]]s. Rocket vehicles carry their own [[oxidiser]], unlike most combustion engines, so rocket engines can be used in a [[vacuum]] to propel [[spacecraft]] and [[ballistic missile]]s.

Compared to other types of jet engine, rocket engines are the lightest and have the highest thrust, but are the least propellant-efficient (they have the lowest [[specific impulse]]). The ideal exhaust is [[hydrogen]], the lightest of all elements, but chemical rockets produce a mix of heavier species, reducing the exhaust velocity.

Rocket engines become more efficient at high speeds, due to the [[Oberth effect]].<ref name=ways>{{cite web|url=https://archive.org/details/nasa_techdoc_19720008133|title=Ways to spaceflight|volume=NASA TT F-622|others=Translation of the German language original "Wege zur Raumschiffahrt," (1920)|location=Tunis, Tunisia|year=1970|author=Hermann Oberth|publisher=Agence Tunisienne de Public-Relations}}</ref>

==Terminology==
Here, "rocket" is used as an abbreviation for "rocket engine".

'''[[Thermal rocket]]s''' use an inert propellant, heated by electricity ([[electrothermal propulsion]]) or a nuclear reactor ([[nuclear thermal rocket]]).

'''Chemical rockets''' are powered by [[exothermic]] [[redox chemistry|reduction-oxidation]] chemical reactions of the propellant:

*'''[[Solid-fuel rocket]]s''' (or '''solid-propellant rockets''' or '''motors''') are chemical rockets which use propellant in a [[solid|solid state]].
*'''[[Liquid-propellant rocket]]s''' use one or more propellants in a [[liquid state]] fed from tanks.
*'''[[Hybrid rocket]]s''' use a solid propellant in the combustion chamber, to which a second liquid or gas [[oxidizing agent|oxidiser]] or propellant is added to permit combustion.
*'''[[Monopropellant rocket]]s''' use a single propellant decomposed by a [[catalyst]]. The most common monopropellants are [[hydrazine]] and [[hydrogen peroxide]].

==Principle of operation==
[[File:Liquid-Fuel Rocket Diagram.svg|thumb|upright=1.25|Simplified diagram of a liquid-fuel rocket: {{olist |
|[[Liquid rocket propellant|Liquid fuel]] tank
|[[Oxidizing agent|Liquid oxidiser]] tank
|Pumps feed fuel and oxidiser under high pressure.
|[[Combustion chamber]] mixes and burns the propellants.
|[[Propelling nozzle|Exhaust nozzle]] expands and accelerates the gas jet to produce thrust.
|Exhaust exits nozzle.
}}]]

[[File:Solid-Fuel Rocket Diagram.svg|thumb|upright=1.25|Simplified diagram of a solid-fuel rocket: {{olist
|Solid [[Rocket propellant#Solid chemical propellants|fuel–oxidiser mixture]] (propellant) packed into casing
|[[Pyrotechnic initiator|Igniter]] initiates propellant combustion.
|Central hole in propellant acts as the [[combustion chamber]].
|[[Propelling nozzle|Exhaust nozzle]] expands and accelerates the gas jet to produce thrust.
|Exhaust exits nozzle.
}}]]
Rocket engines produce thrust by the expulsion of an exhaust [[fluid]] that has been accelerated to high speed through a [[propelling nozzle]]. The fluid is usually a gas created by high pressure ({{convert|10|to|300|bar|psi|order=flip|adj=on}}) combustion of solid or liquid [[Rocket propellant|propellants]], consisting of [[fuel]] and [[oxidizing agent|oxidiser]] components, within a [[combustion chamber]]. As the gases expand through the nozzle, they are accelerated to very high ([[supersonic]]) speed, and the reaction to this pushes the engine in the opposite direction. Combustion is most frequently used for practical rockets, as the laws of [[thermodynamics]] (specifically [[Carnot's theorem (thermodynamics)|Carnot's theorem]]) dictate that high temperatures and pressures are desirable for the best [[thermal efficiency]]. [[Nuclear thermal rocket]]s are capable of higher efficiencies, but currently have [[Nuclear thermal rocket#Risks|environmental problems]] which preclude their routine use in the Earth's atmosphere and [[cislunar space]].

For [[model rocket]]ry, an available alternative to combustion is the [[water rocket]] pressurized by compressed air, [[carbon dioxide]], [[nitrogen]], or any other readily available, inert gas.

===Propellant===
Rocket propellant is mass that is stored, usually in some form of tank, or within the combustion chamber itself, prior to being ejected from a rocket engine in the form of a fluid jet to produce thrust.

Chemical rocket propellants are the most commonly used. These undergo exothermic chemical reactions producing a hot gas jet for propulsion. Alternatively, a chemically inert [[reaction mass]] can be heated by a high-energy power source through a heat exchanger in lieu of a combustion chamber.

[[Solid rocket]] propellants are prepared in a mixture of fuel and oxidising components called ''grain'', and the propellant storage casing effectively becomes the combustion chamber.

===Injection===
[[Liquid-propellant rocket|Liquid-fuelled rockets]] force separate fuel and oxidiser components into the combustion chamber, where they mix and burn. [[Hybrid rocket]] engines use a combination of solid and liquid or gaseous propellants. Both liquid and hybrid rockets use ''[[Liquid-fuel rocket#Injectors|injectors]]'' to introduce the propellant into the chamber. These are often an array of simple [[jet (nozzle)|jet]]s – holes through which the propellant escapes under pressure; but sometimes may be more complex spray nozzles. When two or more propellants are injected, the jets usually deliberately cause the propellants to collide as this breaks up the flow into smaller droplets that burn more easily.

===Combustion chamber===
For chemical rockets the combustion chamber is typically cylindrical, and [[flame holder]]s, used to hold a part of the combustion in a slower-flowing portion of the combustion chamber, are not needed. The dimensions of the cylinder are such that the propellant is able to combust thoroughly; different [[rocket propellant]]s require different combustion chamber sizes for this to occur.

This leads to a number called <math>L^*</math>, the [[characteristic length]]:
:<math>L^* = \frac {V_c} {A_t}</math>
where:
*<math>V_c</math> is the volume of the chamber
*<math>A_t</math> is the area of the throat of the nozzle.
L* is typically in the range of {{convert|64|-|152|cm|in}}.

The temperatures and pressures typically reached in a rocket combustion chamber in order to achieve practical [[thermal efficiency]] are extreme compared to a [[afterburner|non-afterburning]] [[airbreathing jet engine]]. No atmospheric nitrogen is present to dilute and cool the combustion, so the propellant mixture can reach true [[stoichiometric]] ratios. This, in combination with the high pressures, means that the rate of heat conduction through the walls is very high.

In order for fuel and oxidiser to flow into the chamber, the pressure of the propellants entering the combustion chamber must exceed the pressure inside the combustion chamber itself. This may be accomplished by a variety of design approaches including [[turbopump]]s or, in simpler engines, via [[Pressure-fed cycle (rocket)|sufficient tank pressure]] to advance fluid flow. Tank pressure may be maintained by several means, including a high-pressure [[helium]] pressurization system common to many large rocket engines or, in some newer rocket systems, by a bleed-off of high-pressure gas from the engine cycle to [[autogenous pressurization|autogenously pressurize]] the propellant tanks<ref name=nsf20160927>
{{cite news |last=Bergin|first=Chris |url=https://www.nasaspaceflight.com/2016/09/spacex-reveals-mars-game-changer-colonization-plan/ |title=SpaceX reveals ITS Mars game changer via colonization plan |work=[[NASASpaceFlight.com]] |date=2016-09-27 |access-date=2016-09-27 }}</ref><ref name=sfi20160927/> For example, the self-pressurization gas system of the [[SpaceX Starship]] is a critical part of SpaceX strategy to reduce launch vehicle fluids from five in their legacy Falcon 9 vehicle family to just two in Starship, eliminating not only the helium tank pressurant but all [[hypergolic propellant]]s as well as [[nitrogen]] for cold-gas [[reaction control system|reaction-control thrusters]].<ref name=nsf20161003/>

===Nozzle===
{{Main|Rocket engine nozzle}}
[[File:Rocket thrust.svg|thumb|right|Rocket thrust is caused by pressures acting in the combustion chamber and nozzle. From Newton's third law, equal and opposite pressures act on the exhaust, and this accelerates it to high speeds.]]
The hot gas produced in the combustion chamber is permitted to escape through an opening (the "throat"), and then through a diverging expansion section. When sufficient pressure is provided to the nozzle (about 2.5–3 times ambient pressure), the nozzle ''[[choked flow|choke]]s'' and a supersonic jet is formed, dramatically accelerating the gas, converting most of the thermal energy into kinetic energy. Exhaust speeds vary, depending on the [[expansion ratio]] the nozzle is designed for, but exhaust speeds as high as ten times the [[speed of sound]] in air at sea level are not uncommon. About half of the rocket engine's thrust comes from the unbalanced pressures inside the combustion chamber, and the rest comes from the pressures acting against the inside of the nozzle (see diagram). As the gas expands ([[Adiabatic process|adiabatically]]) the pressure against the nozzle's walls forces the rocket engine in one direction while accelerating the gas in the other.

{{Anchor|opt_expansion}} 
[[File:Rocket nozzle expansion.svg|thumb|right|upright|The four expansion regimes of a de Laval nozzle:
• under-expanded
• perfectly expanded
• over-expanded
• grossly over-expanded]]
The most commonly used nozzle is the [[de Laval nozzle]], a fixed geometry nozzle with a high expansion-ratio. The large bell- or cone-shaped nozzle extension beyond the throat gives the rocket engine its characteristic shape.

The exit [[static pressure#Static pressure in fluid dynamics|static pressure]] of the exhaust jet depends on the chamber pressure and the ratio of exit to throat area of the nozzle. As exit pressure varies from the ambient (atmospheric) pressure, a choked nozzle is said to be
* '''under-expanded''' (exit pressure greater than ambient),
* '''perfectly expanded''' (exit pressure equals ambient),
* '''over-expanded''' (exit pressure less than ambient; [[shock diamond]]s form outside the nozzle), or
* '''grossly over-expanded''' (a [[shock wave]] forms inside the nozzle extension).

In practice, perfect expansion is only achievable with a variable–exit-area nozzle (since ambient pressure decreases as altitude increases), and is not possible above a certain altitude as ambient pressure approaches zero. If the nozzle is not perfectly expanded, then loss of efficiency occurs. Grossly over-expanded nozzles lose less efficiency, but can cause mechanical problems with the nozzle. Fixed-area nozzles become progressively more under-expanded as they gain altitude. Almost all de Laval nozzles will be momentarily grossly over-expanded during startup in an atmosphere.<ref name="HuzelAndHuang">{{cite book
|last = Huzel
|first = Dexter K.
|last2 = Huang
|first2 = David H.
|date = 1 January 1971
|title = NASA SP-125, Design of Liquid Propellant Rocket Engines, Second Edition
|url = https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710019929_1971019929.pdf
|publisher = NASA
|page = 
|archive-url = https://web.archive.org/web/20170324150551/https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710019929_1971019929.pdf/
|archive-date = 24 March 2017
|url-status = dead
|access-date = 7 July 2017
}}</ref>

Nozzle efficiency is affected by operation in the atmosphere because atmospheric pressure changes with altitude; but due to the supersonic speeds of the gas exiting from a rocket engine, the pressure of the jet may be either below or above ambient, and equilibrium between the two is not reached at all altitudes (see diagram).

====Back pressure and optimal expansion====
For optimal performance, the pressure of the gas at the end of the nozzle should just equal the ambient pressure: if the exhaust's pressure is lower than the ambient pressure, then the vehicle will be slowed by the difference in pressure between the top of the engine and the exit; on the other hand, if the exhaust's pressure is higher, then exhaust pressure that could have been converted into thrust is not converted, and energy is wasted.

To maintain this ideal of equality between the exhaust's exit pressure and the ambient pressure, the diameter of the nozzle would need to increase with altitude, giving the pressure a longer nozzle to act on (and reducing the exit pressure and temperature). This increase is difficult to arrange in a lightweight fashion, although is routinely done with other forms of jet engines. In rocketry a lightweight compromise nozzle is generally used and some reduction in atmospheric performance occurs when used at other than the 'design altitude' or when throttled. To improve on this, various exotic nozzle designs such as the [[plug nozzle]], [[stepped nozzles]], the [[expanding nozzle]] and the [[aerospike engine|aerospike]] have been proposed, each providing some way to adapt to changing ambient air pressure and each allowing the gas to expand further against the nozzle, giving extra thrust at higher altitudes.

When exhausting into a sufficiently low ambient pressure (vacuum) several issues arise. One is the sheer weight of the nozzle—beyond a certain point, for a particular vehicle, the extra weight of the nozzle outweighs any performance gained. Secondly, as the exhaust gases adiabatically expand within the nozzle they cool, and eventually some of the chemicals can freeze, producing 'snow' within the jet. This causes instabilities in the jet and must be avoided.

On a [[de Laval nozzle]], exhaust gas flow detachment will occur in a grossly over-expanded nozzle. As the detachment point will not be uniform around the axis of the engine, a side force may be imparted to the engine. This side force may change over time and result in control problems with the launch vehicle.

Advanced [[altitude compensating nozzle|altitude-compensating]] designs, such as the [[aerospike engine|aerospike]] or [[plug nozzle]], attempt to minimize performance losses by adjusting to varying expansion ratio caused by changing altitude.

===Propellant efficiency===
{{See also|Specific impulse}}
[[Image:Nozzle de Laval diagram.svg|thumb|right|upright|Typical temperature (T), pressure (p), and velocity (v) profiles in a de Laval Nozzle]]
For a rocket engine to be propellant efficient, it is important that the maximum pressures possible be created on the walls of the chamber and nozzle by a specific amount of propellant; as this is the source of the thrust. This can be achieved by all of:

* heating the propellant to as high a temperature as possible (using a high energy fuel, containing hydrogen and carbon and sometimes metals such as [[aluminium]], or even using nuclear energy)
* using a low specific density gas (as hydrogen rich as possible)
* using propellants which are, or decompose to, simple molecules with few degrees of freedom to maximise translational velocity

Since all of these things minimise the mass of the propellant used, and since pressure is proportional to the mass of propellant present to be accelerated as it pushes on the engine, and since from [[Newton's third law]] the pressure that acts on the engine also reciprocally acts on the propellant, it turns out that for any given engine, the speed that the propellant leaves the chamber is unaffected by the chamber pressure (although the thrust is proportional). However, speed is significantly affected by all three of the above factors and the exhaust speed is an excellent measure of the engine propellant efficiency. This is termed ''exhaust velocity'', and after allowance is made for factors that can reduce it, the '''[[effective exhaust velocity]]''' is one of the most important parameters of a rocket engine (although weight, cost, ease of manufacture etc. are usually also very important).

For aerodynamic reasons the flow goes sonic ("[[Choked flow|chokes]]") at the narrowest part of the nozzle, the 'throat'. Since the [[speed of sound]] in gases increases with the square root of temperature, the use of hot exhaust gas greatly improves performance. By comparison, at room temperature the speed of sound in air is about 340 m/s while the speed of sound in the hot gas of a rocket engine can be over 1700 m/s; much of this performance is due to the higher temperature, but additionally rocket propellants are chosen to be of low molecular mass, and this also gives a higher velocity compared to air.

Expansion in the rocket nozzle then further multiplies the speed, typically between 1.5 and 2 times, giving a highly [[collimated]] hypersonic exhaust jet. The speed increase of a rocket nozzle is mostly determined by its area expansion ratio—the ratio of the area of the exit to the area of the throat, but detailed properties of the gas are also important. Larger ratio nozzles are more massive but are able to extract more heat from the combustion gases, increasing the exhaust velocity.

===Thrust vectoring===
{{Main|Thrust vectoring}}
Vehicles typically require the overall thrust to change direction over the length of the burn. A number of different ways to achieve this have been flown:

* The entire engine is mounted on a [[hinge]] or [[gimbal]] and any propellant feeds reach the engine via low pressure flexible pipes or rotary couplings.
* Just the combustion chamber and nozzle is gimballed, the pumps are fixed, and high pressure feeds attach to the engine.
* Multiple engines (often canted at slight angles) are deployed but throttled to give the overall vector that is required, giving only a very small penalty.
* High-temperature vanes protrude into the exhaust and can be tilted to deflect the jet.

==Overall performance==
Rocket technology can combine very high thrust ([[meganewton]]s), very high exhaust speeds (around 10 times the speed of sound in air at sea level) and very high thrust/weight ratios (>100) ''simultaneously'' as well as being able to operate outside the atmosphere, and while permitting the use of low pressure and hence lightweight tanks and structure.

Rockets can be further optimised to even more extreme performance along one or more of these axes at the expense of the others.

===Specific impulse===
{{Specific impulse|align=right}}
{{Main|Specific impulse}}

The most important metric for the efficiency of a rocket engine is [[impulse (physics)|impulse]] per unit of [[propellant]], this is called [[specific impulse]] (usually written <math>I_{sp}</math>). This is either measured as a speed (the ''effective exhaust velocity'' <math>v_{e}</math> in metres/second or ft/s) or as a time (seconds). For example, if an engine producing 100 pounds of thrust runs for 320 seconds and burns 100 pounds of propellant, then the specific impulse is 320 seconds. The higher the specific impulse, the less propellant is required to provide the desired impulse.

The specific impulse that can be achieved is primarily a function of the propellant mix (and ultimately would limit the specific impulse), but practical limits on chamber pressures and the nozzle expansion ratios reduce the performance that can be achieved.

===Net thrust===
{{Main|Thrust}}
Below is an approximate equation for calculating the net thrust of a rocket engine:<ref>{{cite book|author=George P. Sutton|author2=Oscar Biblarz|name-list-style=amp|title=Rocket Propulsion Elements|edition=8th|publisher=Wiley Interscience|date=2010|isbn=9780470080245|url=https://archive.org/details/Rocket_Propulsion_Elements_8th_Edition_by_Oscar_Biblarz_George_P._Sutton/page/34/mode/2up}} See Equation 2-14.</ref>

{{block indent|<math>F_n = \dot{m}\;v_{e} = \dot{m}\;v_{e-opt} + A_{e}(p_{e} - p_{amb})</math>}}

{| border="0" cellpadding="2" style="margin-left:1em"
|-
|align=right|where:
| 
|-
!align=right|<math>\dot{m}</math>
|align=left|=  exhaust gas mass flow
|-
!align=right|<math>v_{e}</math>
|align=left|=  effective exhaust velocity (sometimes otherwise denoted as ''c'' in publications)
|-
!align=right|<math>v_{e-opt}</math>
|align=left|=  effective jet velocity when Pamb = Pe
|-
!align=right|<math>A_{e}</math>
|align=left|=  flow area at nozzle exit plane (or the plane where the jet leaves the nozzle if separated flow)
|-
!align=right|<math>p_{e}</math>
|align=left|=  static pressure at nozzle exit plane
|-
!align=right|<math>p_{amb}</math>
|align=left|=  ambient (or atmospheric) pressure
|}

Since, unlike a jet engine, a conventional rocket motor lacks an air intake, there is no 'ram drag' to deduct from the gross thrust. Consequently, the net thrust of a rocket motor is equal to the gross thrust (apart from static back pressure).

The <math>\dot{m}\;v_{e-opt}\,</math> term represents the momentum thrust, which remains constant at a given throttle setting, whereas the <math>A_{e}(p_{e} - p_{amb})\,</math> term represents the pressure thrust term. At full throttle, the net thrust of a rocket motor improves slightly with increasing altitude, because as atmospheric pressure decreases with altitude, the pressure thrust term increases. At the surface of the Earth the pressure thrust may be reduced by up to 30%, depending on the engine design. This reduction drops roughly exponentially to zero with increasing altitude.

Maximum efficiency for a rocket engine is achieved by maximising the momentum contribution of the equation without incurring penalties from over expanding the exhaust. This occurs when <math>p_{e} = p_{amb}</math>. Since ambient pressure changes with altitude, most rocket engines spend very little time operating at peak efficiency.

Since specific impulse is force divided by the rate of mass flow, this equation means that the specific impulse varies with altitude.

===Vacuum specific impulse, Isp===

Due to the specific impulse varying with pressure, a quantity that is easy to compare and calculate with is useful. Because rockets [[choked flow|choke]] at the throat, and because the supersonic exhaust prevents external pressure influences travelling upstream, it turns out that the pressure at the exit is ideally exactly proportional to the propellant flow <math> \dot{m}</math>, provided the mixture ratios and combustion efficiencies are maintained. It is thus quite usual to rearrange the above equation slightly:<ref>{{cite book|author=George P. Sutton|author2=Oscar Biblarz|name-list-style=amp|title=Rocket Propulsion Elements|edition=8th|publisher=Wiley Interscience|date=2010|isbn=9780470080245|url=https://archive.org/details/Rocket_Propulsion_Elements_8th_Edition_by_Oscar_Biblarz_George_P._Sutton/page/34/mode/2up}} See Equation 3-33.</ref>

{{block indent|<math> F_{vac} = C_f\, \dot{m}\, c^*</math>}}

and so define the ''vacuum Isp'' to be:

{{block indent|<math>v_{evac} = C_f\, c^* \,</math>}}

where:

{{block indent|1=<math>c^*</math>  =  the [[characteristic velocity]] of the combustion chamber (dependent on propellants and combustion efficiency)}}
{{block indent|1=<math>C_f</math>  =  the thrust coefficient constant of the nozzle (dependent on nozzle geometry, typically about 2)}}

And hence:
{{block indent|<math> F_n = \dot{m}\, v_{evac} - A_{e}\, p_{amb}</math>}}

===Throttling===

Rockets can be throttled by controlling the propellant combustion rate <math> \dot{m}</math> (usually measured in kg/s or lb/s). In liquid and hybrid rockets, the propellant flow entering the chamber is controlled using valves, in [[solid rocket]]s it is controlled by changing the area of propellant that is burning and this can be designed into the propellant grain (and hence cannot be controlled in real-time).

Rockets can usually be throttled down to an exit pressure of about one-third of ambient pressure<ref name=Sutton/> (often limited by flow separation in nozzles) and up to a maximum limit determined only by the mechanical strength of the engine.

In practice, the degree to which rockets can be throttled varies greatly, but most rockets can be throttled by a factor of 2 without great difficulty;<ref name=Sutton/> the typical limitation is combustion stability, as for example, injectors need a minimum pressure to avoid triggering damaging oscillations (chugging or combustion instabilities); but injectors can be optimised and tested for wider ranges.

For example, some more recent liquid-propellant engine designs that have been optimised for greater throttling capability ([[BE-3]], [[Raptor (rocket engine)|Raptor]]) can be throttled to as low as 18–20 per cent of rated thrust.<ref name="sn20150407">
{{cite news |last1=Foust|first=Jeff |title=Blue Origin Completes BE-3 Engine as BE-4 Work Continues |url=http://spacenews.com/blue-origin-completes-be-3-engine-as-be-4-work-continues/ |access-date=2016-10-20 |work=Space News |date=2015-04-07 }}</ref><ref name="sfi20160927">{{cite news |url= http://www.spaceflightinsider.com/organizations/space-exploration-technologies/elon-musk-shows-off-interplanetary-transport-system/ |title= Elon Musk Shows Off Interplanetary Transport System |publisher= Spaceflight Insider |last= Richardson |first= Derek |date= 2016-09-27 |access-date= 2016-10-20 |archive-date= 2016-10-01 |archive-url= https://web.archive.org/web/20161001225649/http://www.spaceflightinsider.com/organizations/space-exploration-technologies/elon-musk-shows-off-interplanetary-transport-system/ |url-status= dead }}</ref>

Solid rockets can be throttled by using shaped grains that will vary their surface area over the course of the burn.<ref name="Sutton" />

===Energy efficiency===
{{Further|Rocket#Energy efficiency}}
[[File:Rocket propulsion efficiency.svg|thumb|Rocket vehicle mechanical efficiency as a function of vehicle instantaneous speed divided by effective exhaust speed. These percentages need to be multiplied by internal engine efficiency to get overall efficiency.]]
Rocket engine nozzles are surprisingly efficient [[heat engines]] for generating a high speed jet, as a consequence of the high combustion temperature and high [[compression ratio]]. Rocket nozzles give an excellent approximation to [[adiabatic expansion]] which is a reversible process, and hence they give efficiencies which are very close to that of the [[Carnot cycle]]. Given the temperatures reached, over 60% efficiency can be achieved with chemical rockets.

For a ''vehicle'' employing a rocket engine the energetic efficiency is very good if the vehicle speed approaches or somewhat exceeds the exhaust velocity (relative to launch); but at low speeds the [[Propulsive efficiency|energy efficiency]] goes to 0% at zero speed (as with all [[jet propulsion]]). See [[Rocket#Energy efficiency|Rocket energy efficiency]] for more details.

{{clear}}

===Thrust-to-weight ratio===
{{Main|thrust-to-weight ratio}}
Rockets, of all the jet engines, indeed of essentially all engines, have the highest thrust-to-weight ratio. This is especially true for liquid-fuelled rocket engines.

This high performance is due to the small volume of [[pressure vessel]]s that make up the engine—the pumps, pipes and combustion chambers involved. The lack of inlet duct and the use of dense liquid propellant allows the pressurisation system to be small and lightweight, whereas duct engines have to deal with air which has around three orders of magnitude lower density.

{{Engine thrust to weight table}}

Of the liquid fuels used, density is lowest for [[liquid hydrogen]]. Although hydrogen/oxygen burning has the highest [[specific impulse]] of any in-use chemical rocket, hydrogen's very low density (about one-fourteenth that of water) requires larger and heavier turbopumps and pipework, which decreases the engine's thrust-to-weight ratio (for example the RS-25) compared to those that do not use hydrogen (NK-33).

==Mechanical issues==
Rocket combustion chambers are normally operated at fairly high pressure, typically 10–200{{nbsp}}bar (1–20{{nbsp}}MPa, 150–3,000{{nbsp}}psi). When operated within significant atmospheric pressure, higher combustion chamber pressures give better performance by permitting a larger and more efficient nozzle to be fitted without it being grossly overexpanded.

However, these high pressures cause the outermost part of the chamber to be under very large [[hoop stress]]es – rocket engines are [[pressure vessel]]s.

Worse, due to the high temperatures created in rocket engines the materials used tend to have a significantly lowered working tensile strength.

In addition, significant temperature gradients are set up in the walls of the chamber and nozzle, these cause differential expansion of the inner liner that create [[internal stresses]].

=== Hard starts ===
A '''hard start''' refers to an over-pressure condition during start of a rocket engine at ignition. In the worst cases, this takes the form of an unconfined explosion, resulting in the damage or destruction of the engine.

Rocket fuels, [[hypergolic]] or otherwise, must be introduced into the combustion chamber at the correct rate in order to have a controlled rate of production of hot gas.<ref>{{Cite web |title=Introducing Propellant into a Combustion Chamber |url=https://www.idc-online.com/technical_references/pdfs/mechanical_engineering/Introducing_Propellant_into_a_Combustion_Chamber.pdf |access-date=February 16, 2024 |website=IDC Online}}</ref> A "hard start" indicates that the quantity of combustible propellant that entered the combustion chamber prior to ignition was too large. The result is an excessive spike of pressure, possibly leading to structural failure or explosion.

Avoiding hard starts involves careful timing of the ignition relative to valve timing or varying the mixture ratio so as to limit the maximum pressure that can occur or simply ensuring an adequate ignition source is present well prior to propellant entering the chamber.

Explosions from hard starts usually cannot happen with purely gaseous propellants, since the amount of the gas present in the chamber is limited by the injector area relative to the throat area, and for practical designs, propellant mass escapes too quickly to be an issue.

A famous example of a hard start was the explosion of [[Wernher von Braun]]'s "1W" engine during a demonstration to General [[Walter Dornberger]] on December 21, 1932. Delayed ignition allowed the chamber to fill with alcohol and liquid oxygen, which exploded violently. Shrapnel was embedded in the walls, but nobody was hit.

==Acoustic issues==
The extreme vibration and acoustic environment inside a rocket motor commonly result in peak stresses well above mean values, especially in the presence of [[organ pipe]]-like resonances and gas turbulence.<ref>{{Cite news|url=https://www.technologyreview.com/s/414364/whats-the-deal-with-rocket-vibrations/|title=What's the Deal with Rocket Vibrations?|last=Sauser|first=Brittany|work=MIT Technology Review|access-date=2018-04-27|language=en}}</ref>

===Combustion instabilities===
The combustion may display undesired instabilities, of sudden or periodic nature. The pressure in the injection chamber may increase until the propellant flow through the injector plate decreases; a moment later the pressure drops and the flow increases, injecting more propellant in the combustion chamber which burns a moment later, and again increases the chamber pressure, repeating the cycle. This may lead to high-amplitude pressure oscillations, often in ultrasonic range, which may damage the motor. Oscillations of ±200 psi at 25 kHz were the cause of failures of early versions of the [[LGM-25C Titan II|Titan II]] missile second stage engines. The other failure mode is a [[deflagration to detonation transition]]; the supersonic [[Longitudinal wave|pressure wave]] formed in the combustion chamber may destroy the engine.<ref name="titan2">{{cite book|author=David K. Stumpf|title=Titian II: A History of a Cold War Missile Program|publisher=University of Arkansas Press|date=2000|isbn=1-55728-601-9}}</ref>

Combustion instability was also a problem during [[SM-65 Atlas|Atlas]] development. The Rocketdyne engines used in the Atlas family were found to suffer from this effect in several static firing tests, and three missile launches exploded on the pad due to rough combustion in the booster engines. In most cases, it occurred while attempting to start the engines with a "dry start" method whereby the igniter mechanism would be activated prior to propellant injection. During the process of man-rating Atlas for [[Project Mercury]], solving combustion instability was a high priority, and the final two Mercury flights sported an upgraded propulsion system with baffled injectors and a hypergolic igniter.

The problem affecting Atlas vehicles was mainly the so-called "racetrack" phenomenon, where burning propellant would swirl around in a circle at faster and faster speeds, eventually producing vibration strong enough to rupture the engine, leading to complete destruction of the rocket. It was eventually solved by adding several baffles around the injector face to break up swirling propellant.

More significantly, combustion instability was a problem with the Saturn [[F-1 engines]]. Some of the early units tested exploded during static firing, which led to the addition of injector baffles.

In the Soviet space program, combustion instability also proved a problem on some rocket engines, including the RD-107 engine used in the R-7 family and the RD-216 used in the R-14 family, and several failures of these vehicles occurred before the problem was solved. Soviet engineering and manufacturing processes never satisfactorily resolved combustion instability in larger RP-1/LOX engines, so the RD-171 engine used to power the Zenit family still used four smaller thrust chambers fed by a common engine mechanism.

The combustion instabilities can be provoked by remains of cleaning solvents in the engine (e.g. the first attempted launch of a Titan II in 1962), reflected shock wave, initial instability after ignition, explosion near the nozzle that reflects into the combustion chamber, and many more factors. In stable engine designs the oscillations are quickly suppressed; in unstable designs they persist for prolonged periods. Oscillation suppressors are commonly used.

Three different types of combustion instabilities occur:

====Chugging====
A low frequency oscillation in chamber pressure below 200 [[Hertz]]. Usually it is caused by pressure variations in feed lines due to variations in acceleration of the vehicle, when rocket engines are building up thrust, are shut down or are being throttled.<ref name=sutton1975/>{{rp|261}}<ref name="HuzelAndHuang"/>{{rp|146}}

Chugging can cause a worsening feedback loop, as cyclic variation in thrust causes longitudinal vibrations to travel up the rocket, causing the fuel lines to vibrate, which in turn do not deliver propellant smoothly into the engines. This phenomenon is known as "[[pogo oscillation]]s" or "pogo", named after the [[pogo stick]].<ref name="sutton1975" />{{rp|258}}

In the worst case, this may result in damage to the payload or vehicle. Chugging can be minimised by using several methods, such as installing energy-absorbing devices on feed lines.<ref name=sutton1975/>{{rp|259}} Chugging may cause Screeching.<ref name="HuzelAndHuang"/>{{rp|146}}

====Buzzing====
An intermediate frequency oscillation in chamber pressure between 200 and 1000 [[Hertz]]. Usually caused due to insufficient pressure drop across the injectors.<ref name=sutton1975/>{{rp|261}} It generally is mostly annoying, rather than being damaging.

Buzzing is known to have adverse effects on engine performance and reliability, primarily as it causes [[material fatigue]].<ref name="HuzelAndHuang" />{{rp|147}} In extreme cases combustion can end up being forced backwards through the injectors – this can cause explosions with monopropellants.{{citation needed|date=April 2018}} Buzzing may cause Screeching.<ref name="sutton1975" />{{rp|261}}

====Screeching====
A high frequency oscillation in chamber pressure above 1000 [[Hertz]], sometimes called screaming or squealing. The most immediately damaging, and the hardest to control. It is due to acoustics within the combustion chamber that often couples to the chemical combustion processes that are the primary drivers of the energy release, and can lead to unstable resonant "screeching" that commonly leads to catastrophic failure due to thinning of the insulating thermal boundary layer. Acoustic oscillations can be excited by thermal processes, such as the flow of hot air through a pipe or combustion in a chamber. Specifically, standing acoustic waves inside a chamber can be intensified if combustion occurs more intensely in regions where the pressure of the acoustic wave is maximal.<ref name=strutt1896>
{{cite book|author=John W. Strutt|title=The Theory of Sound – Volume 2|edition=2nd|publisher=Macmillan (reprinted by Dover Publications in 1945)|date=1896|page=226}} According to Lord Rayleigh's criterion for thermoacoustic processes, "If heat be given to the air at the moment of greatest condensation, or be taken from it at the moment of greatest rarefaction, the vibration is encouraged. On the other hand, if heat be given at the moment of greatest rarefaction, or abstracted at the moment of greatest condensation, the vibration is discouraged."</ref><ref>Lord Rayleigh (1878) "The explanation of certain acoustical phenomena" (namely, the [[Rijke tube]]) ''Nature'', vol. 18, pages 319–321.</ref><ref>E. C. Fernandes and M. V. Heitor, "Unsteady flames and the Rayleigh criterion" in {{cite book|editor=F. Culick|editor2=M. V. Heitor|editor3=J. H. Whitelaw|title=Unsteady Combustion|edition=1st|publisher=Kluwer Academic Publishers|date=1996|page=4|isbn=0-7923-3888-X|url=https://books.google.com/books?id=Je_hG6UfnogC&pg=PA1}}</ref><ref name=sutton1975>
{{cite book |author=G.P. Sutton |author2=D.M. Ross |name-list-style=amp |title=Rocket Propulsion Elements: An Introduction to the Engineering of Rockets |edition=4th |url=https://archive.org/details/rocketpropulsion0000sutt/page/258/mode/2up |publisher=Wiley Interscience |date=1975 |isbn=0-471-83836-5 }} See Chapter 8, Section 6 and especially Section 7, re combustion instability.</ref>

Such effects are very difficult to predict analytically during the design process, and have usually been addressed by expensive, time-consuming and extensive testing, combined with trial and error remedial correction measures.

Screeching is often dealt with by detailed changes to injectors, changes in the propellant chemistry, vaporising the propellant before injection or use of [[Helmholtz damper]]s within the combustion chambers to change the resonant modes of the chamber.{{citation needed|date=April 2018}}

Testing for the possibility of screeching is sometimes done by exploding small explosive charges outside the combustion chamber with a tube set tangentially to the combustion chamber near the injectors to determine the engine's [[impulse response]] and then evaluating the time response of the chamber pressure- a fast recovery indicates a stable system.

===Exhaust noise===
{{Main|acoustic signature}}
For all but the very smallest sizes, rocket exhaust compared to other engines is generally very noisy. As the [[hypersonic]] exhaust mixes with the ambient air, [[shock wave]]s are formed. The [[Space Shuttle]] generated over 200 [[dB(A)]] of noise around its base. To reduce this, and the risk of payload damage or injury to the crew atop the stack, the [[mobile launcher platform]] was fitted with a [[Sound Suppression System]] that sprayed {{convert|1.1|e6L|USgal}} of water around the base of the rocket in 41 seconds at launch time. Using this system kept sound levels within the payload bay to 142 dB.<ref>{{Cite web
|title=Sound Suppression System
|publisher=NASA
|url=https://www.nasa.gov/mission_pages/shuttle/launch/sound-suppression-system.html
|access-date=2017-02-09
|archive-date=2020-08-10
|archive-url=https://web.archive.org/web/20200810203904/https://www.nasa.gov/mission_pages/shuttle/launch/sound-suppression-system.html
|url-status=dead
}}</ref>

The [[sound intensity]] from the shock waves generated depends on the size of the rocket and on the exhaust velocity. Such shock waves seem to account for the characteristic crackling and popping sounds produced by large rocket engines when heard live. These noise peaks typically overload microphones and audio electronics, and so are generally weakened or entirely absent in recorded or broadcast audio reproductions. For large rockets at close range, the acoustic effects could actually kill.<ref name="CR566">R.C. Potter and M.J. Crocker (1966). [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660030602_1966030602.pdf NASA CR-566, Acoustic Prediction Methods For Rocket Engines, Including The Effects Of Clustered Engines And Deflected Flow] From website of the National Aeronautics and Space Administration Langley (NASA Langley)</ref>

More worryingly for space agencies, such sound levels can also damage the launch structure, or worse, be reflected back at the comparatively delicate rocket above. This is why so much water is typically used at launches. The water spray changes the acoustic qualities of the air and reduces or deflects the sound energy away from the rocket.

Generally speaking, noise is most intense when a rocket is close to the ground, since the noise from the engines radiates up away from the jet, as well as reflecting off the ground. Also, when the vehicle is moving slowly, little of the chemical energy input to the engine can go into increasing the kinetic energy of the rocket (since useful power ''P'' transmitted to the vehicle is <math>P = F*V</math> for thrust ''F'' and speed ''V''). Then the largest portion of the energy is dissipated in the exhaust's interaction with the ambient air, producing noise. This noise can be reduced somewhat by flame trenches with roofs, by water injection around the jet and by deflecting the jet at an angle.

== Rocket engine development ==
=== United States ===
The development of the US rocket engine industry has been shaped by a complex web of relationships between government agencies, private companies, research institutions, and other stakeholders.

Since the establishment of the first [[liquid-propellant rocket]] engine company ([[Reaction Motors|Reaction Motors, Inc.]]) in 1941 and the first government laboratory ([[Guggenheim Aeronautical Laboratory|GALCIT]]) devoted to the subject, the US liquid-propellant rocket engine (LPRE) industry has undergone significant changes. At least 14 US companies have been involved in the design, development, manufacture, testing, and flight support operations of various types of rocket engines from 1940 to 2000. In contrast to other countries like Russia, China, or India, where only government or pseudogovernment organisations engage in this business, the US government relies heavily on private industry. These commercial companies are essential to the continued viability of the United States and its form of governance, as they compete with one another to provide cutting-edge rocket engines that meet the needs of the government, the military, and the private sector. In the United States the company that develops the LPRE usually is awarded the production contract.

Generally, the need or demand for a new rocket engine comes from government agencies such as [[NASA]] or the [[United States Department of Defense|Department of Defense]]. Once the need is identified, government agencies may issue [[Request for proposal|requests for proposals]] (RFPs) to solicit proposals from private companies and research institutions. Private companies and research institutions, in turn, may invest in research and development (R&D) activities to develop new rocket engine technologies that meet the needs and specifications outlined in the RFPs.

Alongside private companies, universities, independent research institutes and government laboratories also play a critical role in the research and development of rocket engines.

Universities provide graduate and undergraduate education to train qualified technical personnel, and their research programs often contribute to the advancement of rocket engine technologies. More than 25 universities in the US have taught or are currently teaching courses related to Liquid Propellant Rocket Engines (LPREs), and their graduate and undergraduate education programs are considered one of their most important contributions. Universities such as Princeton University, Cornell University, Purdue University, Pennsylvania State University, University of Alabama, the Navy's Post-Graduate School, or the California Institute of Technology have conducted excellent R&D work on topics related to the rocket engine industry.<ref name=":0" /> One of the earliest examples of the contribution of universities to the rocket engine industry is the work of the GALCIT in 1941. They demonstrated the first jet-assisted takeoff (JATO) rockets to the Army, leading to the establishment of the Jet Propulsion Laboratory.

However the transfer of knowledge from research professors and their projects to the rocket engine industry has been a mixed experience. While some notable professors and relevant research projects have positively influenced industry practices and understanding of LPREs, the connection between university research and commercial companies has been inconsistent and weak.<ref name=":0" /> Universities were not always aware of the industry's specific needs, and engineers and designers in the industry had limited knowledge of university research. As a result, many university research programs remained relatively unknown to industry decision-makers. Furthermore, in the last few decades, certain university research projects, while interesting to professors, were not useful to the industry due to a lack of communication or relevance to industry needs.<ref name=":0" />

Government laboratories, including the Rocket Propulsion Laboratory (now part of Air Force Research Laboratory), Arnold Engineering Test Center, NASA Marshall Space Flight Center, Jet Propulsion Laboratory, Stennis Space Center, White Sands Proving Grounds, and NASA John H. Glenn Research Center, have played crucial roles in the development of liquid rocket propulsion engines (LPREs).<ref name=":0" /> They have conducted unbiased testing, guided work at US and some non-US contractors, performed research and development, and provided essential testing facilities including hover test facilities and simulated altitude test facilities and resources. Initially, private companies or foundations financed smaller test facilities, but since the 1950s, the U.S. government has funded larger test facilities at government laboratories. This approach reduced costs for the government by not building similar facilities at contractors' plants but increased complexity and expenses for contractors. Nonetheless, government laboratories have solidified their significance and contributed to LPRE advancements.

LPRE programs have been subject to several cancellations in the United States, even after spending millions of dollars on their development. For example, the M-l LOX/LH2 LPRE, Titan I, and the RS-2200 aerospike, as well as several JATO units and large uncooled thrust chambers were cancelled. The cancellations of these programs were not related to the specific LPRE's performance or any issues with it. Instead, they were due to the cancellation of the vehicle programs the engine was intended for or budget cuts imposed by the government.

=== USSR ===
Russia and the former Soviet Union was and still is the world's foremost nation in developing and building rocket engines. From 1950 to 1998, their organisations developed, built, and put into operation a larger number and a larger variety of liquid propellant rocket engine (LPRE) designs than any other country. Approximately 500 different LPREs have been developed before 2003. For comparison the United States has developed slightly more than 300 (before 2003). The Soviets also had the most rocket-propelled flight vehicles. They had more liquid propellant [[ballistic missile]]s and more [[Launch vehicle|space launch vehicles]] derived or converted from these decommissioned ballistic missiles than any other nation. As of the end of 1998, the Russians (or earlier the Soviet Union) had successfully launched 2573 [[satellite]]s with LPREs or almost 65% of the world total of 3973. All of these vehicle flights were made possible by the timely development of suitable high-performance reliable LPREs.<ref name=":0">{{Cite book |last=Sutton |first=George |title=History of Liquid Propellant Rocket Engines |publisher=AIAA |year=2006 |isbn=978-1-56347-649-5}}</ref>

==== Institutions and actors ====
Unlike many other countries where the development and production of rocket engines were consolidated within a single organisation, the Soviet Union took a different approach, they established numerous specialised [[OKB|design bureaus]] (DB) which would compete for development contracts. These design bureaus, or "konstruktorskoye buro" (KB) in Russian were state run organisations which were primarily responsible for carrying out [[Research and development|research, development]] and [[Prototype|prototyping]] of advanced technologies usually related to [[Military technology|military hardware]], such as [[turbojet]] [[engine]]s, aircraft components, [[missile]]s, or [[Launch vehicle|space launch vehicles]].

[[OKB|Design Bureaus]] which specialised in rocket engines often possessed the necessary personnel, facilities, and equipment to conduct l[[Launch vehicle system tests|aboratory tests, flow tests, and ground testing of experimental rocket engines]]. Some even had specialised facilities for testing very large engines, conducting [[Launch vehicle system tests|static firings]] of engines installed in vehicle stages, or simulating altitude conditions during engine tests. In certain cases, engine testing, certification and [[quality control]] were outsourced to other organisations and locations with more suitable test facilities. Many DBs also had housing complexes, gymnasiums, and medical facilities intended to support the needs of their employees and their families.

The Soviet Union's LPRE development effort saw significant growth during the 1960s and reached its peak in the 1970s. This era coincided with the [[Cold War]] between the Soviet Union and the United States, characterised by intense competition in spaceflight achievements. Between 14 and 17 Design Bureaus and research institutes were actively involved in developing LPREs during this period. These organisations received relatively steady support and funding due to high military and [[Soviet space program|spaceflight priorities]], which facilitated the continuous development of new engine concepts and manufacturing methods.

Once a mission with a new vehicle (missile or spacecraft) was established it was passed on to a design bureau whose role was to oversee the development of the entire rocket. If none of the previously developed rocket engines met the needs of the mission, a new rocket engine with specific requirements would be contracted to another DB specialised in LPRE development (oftentimes each DB had expertise in specific types of LPREs with different applications, propellants, or engine sizes). This meant that the development or design study of a rocket engine was always aimed at a specific application which entailed set requirements.

When it comes to which DBs were awarded contracts for the development of new rocket engines either a single design bureau would be chosen or several design bureaus would be given the same contract which sometimes led to fierce competition between DBs.

When only one DB was picked for the development, it was often the result of the relationship between a vehicle or system's chief designer and the chief designer of a rocket engine specialised DB. If the vehicle's chief designer was happy with previous work done by a certain design bureau it was not unusual to see continued reliance on that LPRE bureau for that class of engines. For example, all but one of the LPREs for submarine-launched missiles were developed by the same design bureau for the same vehicle development prime contractor.

However, when two parallel engine development programs were supported in order to select the superior one for a specific application, several qualified rocket engine models were never used. This luxury of choice was not commonly available in other nations. However, the use of design bureaus also led to certain issues, including program cancellations and duplication. Some major programs were cancelled, resulting in the disposal or storage of previously developed engines.

One notable example of duplication and cancellation was the development of engines for the R-9A ballistic missile. Two sets of engines were supported, but ultimately only one set was selected, leaving several perfectly functional engines unused. Similarly, for the ambitious heavy N-l space launch vehicle intended for lunar and planetary missions, the Soviet Union developed and put into production at least two engines for each of the six stages. Additionally, they developed alternate engines for a more advanced N-l vehicle. However, the program faced multiple flight failures, and with the United States' successful [[Moon landing]], the program was ultimately cancelled, leaving the Soviet Union with a surplus of newly qualified engines without a clear purpose.

These examples demonstrate the complex dynamics and challenges faced by the Soviet Union in managing the development and production of rocket engines through Design Bureaus.

==== Accidents ====
The development of rocket engines in the Soviet Union was marked by significant achievements, but it also carried ethical considerations due to numerous accidents and fatalities. From a [[Science and technology studies|Science and Technology Studies]] point of view, the ethical implications of these incidents shed light on the complex relationship between technology, human factors, and the prioritisation of scientific advancement over safety.

The Soviet Union encountered a series of tragic accidents and mishaps in the development and operation of rocket engines. Notably, the USSR holds the unfortunate distinction of having experienced more injuries and deaths resulting from liquid propellant rocket engine (LPRE) accidents than any other country. These incidents brought into question the ethical considerations surrounding the development, testing, and operational use of rocket engines.

One of the most notable disasters occurred in 1960 when the [[R-16 (missile)|R-16]] ballistic missile suffered a catastrophic accident on the launchpad at the [[Töretam|Tyuratam]] launch facility. This incident resulted in the deaths of 124 engineers and military personnel, including Marshal M.I. Nedelin, a former deputy [[Minister of Defence (Soviet Union)|minister of defence]]. The explosion occurred after the second-stage rocket engine suddenly ignited, causing the fully loaded missile to disintegrate. The explosion resulted from the ignition and explosion of the mixed [[hypergolic propellant]]s, consisting of [[nitric acid]] with additives and [[Unsymmetrical dimethylhydrazine|UDMH]] (unsymmetrical dimethylhydrazine).

While the immediate cause of the 1960 accident was attributed to a lack of protective circuits in the missile control unit, the ethical considerations surrounding LPRE accidents in the USSR extend beyond specific technical failures. The secrecy surrounding these accidents, which remained undisclosed for approximately three decades, raises concerns about transparency, accountability, and the protection of human life.

The decision to keep fatal LPRE accidents hidden from the public eye reflects a broader ethical dilemma. The Soviet government, driven by the pursuit of scientific and technological superiority during the Cold War, sought to maintain an image of invincibility and conceal the failures that accompanied their advancements. This prioritisation of national prestige over the well-being and safety of workers raises questions about the ethical responsibility of the state and the organisations involved.

==Testing==

Rocket engines are usually statically tested at a [[rocket engine test facility|test facility]] before being put into production. For high altitude engines, either a shorter nozzle must be used, or the rocket must be tested in a large vacuum chamber.

==Safety==
[[Rocket]] vehicles have a reputation for unreliability and danger; especially catastrophic failures. Contrary to this reputation, carefully designed rockets can be made arbitrarily reliable.{{Citation needed|date=January 2017}} In military use, rockets are not unreliable. However, one of the main non-military uses of rockets is for orbital launch. In this application, the premium has typically been placed on minimum weight, and it is difficult to achieve high reliability and low weight simultaneously. In addition, if the number of flights launched is low, there is a very high chance of a design, operations or manufacturing error causing destruction of the vehicle.{{Citation needed|date=January 2017}}

===Saturn family (1961–1975)===
The [[Rocketdyne H-1]] engine, used in a cluster of eight in the first stage of the [[Saturn I]] and [[Saturn IB]] [[launch vehicle]]s, had no catastrophic failures in 152 engine-flights. The [[Pratt and Whitney]] [[RL10]] engine, used in a cluster of six in the Saturn I second stage, had no catastrophic failures in 36 engine-flights.{{refn|group=notes|name=RL10|The RL10 ''has'', however, experienced occasional failures (some of them catastrophic) in its other use cases, as the engine for the much-flown [[Centaur (rocket stage)|Centaur]] and [[Delta Cryogenic Second Stage|DCSS]] upper stages.}} The [[Rocketdyne F-1]] engine, used in a cluster of five in the first stage of the [[Saturn V]], had no failures in 65 engine-flights. The [[Rocketdyne J-2]] engine, used in a cluster of five in the Saturn V second stage, and singly in the Saturn IB second stage and Saturn V third stage, had no catastrophic failures in 86 engine-flights.{{refn|group=notes|name=J2fail|The J-2 had three premature in-flight shutdowns (two second-stage engine failures on [[Apollo 6]] and one on [[Apollo 13]]), and one failure to restart in orbit (the third-stage engine of Apollo 6). But these failures did not result in vehicle loss or mission abort (although the failure of Apollo 6's third-stage engine to restart ''would'' have forced a mission abort had it occurred on a crewed lunar mission).}}

===Space Shuttle (1981–2011)===
The [[Space Shuttle Solid Rocket Booster]], used in pairs, caused [[Space Shuttle Challenger disaster|one notable catastrophic failure]] in 270 engine-flights.

The [[RS-25]], used in a cluster of three, flew in 46 refurbished engine units. These made a total of 405 engine-flights with no catastrophic in-flight failures. A single in-flight [[RS-25]] engine failure occurred during {{OV|99}}'s [[STS-51-F]] mission.<ref name="P&WFS">{{cite web|url=http://www.pw.utc.com/products/pwr/assets/pwr_SSME.pdf |title=Space Shuttle Main Engine |publisher=Pratt & Whitney Rocketdyne |access-date=November 23, 2011 |year=2005 |url-status=dead |archive-url=https://web.archive.org/web/20120208191620/http://www.pw.utc.com/products/pwr/assets/pwr_SSME.pdf |archive-date=February 8, 2012 }}</ref> This failure had no effect on mission objectives or duration.<ref name="Hale">{{cite web|author=[[Wayne Hale]] & various|title=An SSME-related request|publisher=NASASpaceflight.com|access-date=January 17, 2012|date=January 17, 2012|url=http://forum.nasaspaceflight.com/index.php?topic=27783}}</ref>

==Cooling==
For efficiency reasons, higher temperatures are desirable, but materials lose their strength if the temperature becomes too high. Rockets run with combustion temperatures that can reach {{cvt|6,000|F|C K|-2}}.<ref name="HuzelAndHuang" />{{rp|98}}

Most other jet engines have gas turbines in the hot exhaust. Due to their larger surface area, they are harder to cool and hence there is a need to run the combustion processes at much lower temperatures, losing efficiency. In addition, [[wiktionary:duct engine|duct engines]] use air as an oxidant, which contains 78% largely unreactive nitrogen, which dilutes the reaction and lowers the temperatures.<ref name="Sutton" /> Rockets have none of these inherent combustion temperature limiters.

The temperatures reached by combustion in rocket engines often substantially exceed the melting points of the nozzle and combustion chamber materials (about 1,200 K for [[copper]]). Most construction materials will also combust if exposed to high temperature oxidiser, which leads to a number of design challenges. The nozzle and combustion chamber walls must not be allowed to combust, melt, or vaporize (sometimes facetiously termed an "engine-rich exhaust").

Rockets that use common construction materials such as aluminium, steel, nickel or copper alloys must employ cooling systems to limit the temperatures that engine structures experience. [[Regenerative cooling (rocket)|Regenerative cooling]], where the propellant is passed through tubes around the combustion chamber or nozzle, and other techniques, such as film cooling, are employed to give longer nozzle and chamber life. These techniques ensure that a gaseous thermal [[boundary layer]] touching the material is kept below the temperature which would cause the material to catastrophically fail.

Material exceptions that can sustain rocket combustion temperatures to a certain degree are [[Reinforced carbon–carbon|carbon–carbon materials]] and [[rhenium]], although both are subject to oxidation under certain conditions. Other [[refractory]] alloys, such as alumina, [[molybdenum]], [[tantalum]] or [[tungsten]] have been tried, but were given up on due to various issues.<ref name="RocketProp8">{{cite book |author=George P. Sutton |url=https://archive.org/details/Rocket_Propulsion_Elements_8th_Edition_by_Oscar_Biblarz_George_P._Sutton/page/308/mode/2up |title=Rocket Propulsion Elements |author2=Oscar Biblarz |date=2010 |publisher=Wiley Interscience |isbn=9780470080245 |edition=8th |page=308 |name-list-style=amp}}</ref>

Materials technology, combined with the engine design, is a limiting factor in chemical rockets.

In rockets, the [[heat flux]]es that can pass through the wall are among the highest in engineering; fluxes are generally in the range of 0.8–80 MW/m{{sup|2}} (0.5-50 [[BTU]]/in{{sup|2}}-sec).<ref name="HuzelAndHuang" />{{rp|98}} The strongest heat fluxes are found at the throat, which often sees twice that found in the associated chamber and nozzle. This is due to the combination of high speeds (which gives a very thin boundary layer), and although lower than the chamber, the high temperatures seen there. (See {{section link||Nozzle}} above for temperatures in nozzle).

In rockets the coolant methods include:<ref name="HuzelAndHuang" />{{rp|98–99}}

#[[ablation|Ablative]]: The combustion chamber inside walls are lined with a material that traps heat and carries it away with the exhaust as it vaporizes.
#[[Radiative cooling]]: The engine is made of one or several [[refractory]] materials, which take heat flux until its outer thrust chamber wall glows red- or white-hot, radiating the heat away.
#Dump cooling: A cryogenic propellant, usually [[hydrogen]], is passed around the nozzle and dumped. This cooling method has various issues, such as wasting propellant. It is only used rarely.
#[[regenerative cooling (rocket)|Regenerative cooling]]: The fuel (and possibly, the oxidiser) of a [[liquid rocket engine]] is routed around the nozzle before being injected into the combustion chamber or preburner. This is the most widely applied method of rocket engine cooling.
#Film cooling: The engine is designed with rows of multiple orifices lining the inside wall through which additional propellant is injected, cooling the chamber wall as it evaporates. This method is often used in cases where the heat fluxes are especially high, likely in combination with [[regenerative cooling (rocket)|regenerative cooling]]. A more efficient subtype of film cooling is [[transpiration cooling]], in which propellant passes through a [[porous]] inner combustion chamber wall and transpirates. So far, this method has not seen usage due to various issues with this concept.

Rocket engines may also use several cooling methods. Examples:

* Regeneratively and film cooled combustion chamber and nozzle: [[V-2 rocket|V-2]] Rocket Engine<ref>{{cite web |title=Raketenmotor der A4 (V2)-Rakete |url=https://www.deutsches-museum.de/flugwerft-schleissheim/ausstellung/flugantriebe-und-raketen/raketenmotor-a-4 |access-date=19 September 2022 |language=de |quote=An additional coolant line takes alcohol to fine holes in the inner chamber wall. The alcohol flows alongside the wall, creating a thin, evaporating film for additional cooling.}}</ref>
* Regeneratively cooled combustion chamber with a film cooled nozzle extension: [[Rocketdyne F-1|Rocketdyne F-1 Engine]]<ref>{{cite web |author=McCutcheon, Kimble D. |date=3 August 2022 |title=U.S. Manned Rocket Propulsion Evolution Part 8.12: Rocketdyne F-1 Engine Description |url=https://www.enginehistory.org/Rockets/RPE08.11/RPE08.12.shtml |access-date=19 September 2022}}</ref>
* Regeneratively cooled combustion chamber with an ablatively cooled nozzle extension: The [[LR-91]] rocket engine<ref>{{cite web |author=McCutcheon, Kimble D. |date=3 August 2022 |title=U.S. Manned Rocket Propulsion Evolution Part 6: The Titan Missile |url=https://www.enginehistory.org/Rockets/RPE06/RPE06.shtml |access-date=19 September 2022}}</ref>
* Ablatively and film cooled combustion chamber with a radiatively cooled nozzle extension: [[Lunar module descent engine]] (LMDE), [[Apollo command and service module#Service propulsion system|Service propulsion system engine]] (SPS)<ref>{{cite book |last=Bartlett |first=W. |url=https://ntrs.nasa.gov/api/citations/19700026405/downloads/19700026405.pdf |title=Apollo spacecraft liquid primary propulsion systems |last2=Kirkland |first2=Z. D. |last3=Polifka |first3=R. W. |last4=Smithson |first4=J. C. |last5=Spencer |first5=G. L. |date=7 February 1966 |publisher=NASA, Lyndon B. Johnson Space Center |location=Houston, TX |pages=8 |archive-url=https://web.archive.org/web/20220823092501/https://ntrs.nasa.gov/api/citations/19700026405/downloads/19700026405.pdf |archive-date=23 August 2022 |access-date=10 September 2022 |url-status=bot: unknown }}</ref>
* Radiatively and film cooled combustion chamber with a radiatively cooled nozzle extension: [[Deep Space Industries|Deep space]] storable propellant thrusters<ref name="RocketProp8" />

In all cases, another effect that aids in cooling the rocket engine chamber wall is a thin layer of combustion gases (a [[boundary layer]]) that is notably cooler than the combustion temperature. Disruption of the boundary layer may occur during cooling failures or combustion instabilities, and wall failure typically occurs soon after.

With regenerative cooling a second boundary layer is found in the coolant channels around the chamber. This boundary layer thickness needs to be as small as possible, since the boundary layer acts as an insulator between the wall and the coolant. This may be achieved by making the coolant [[velocity]] in the channels as high as possible.<ref name="HuzelAndHuang" />{{rp|105–106}}

Liquid-fuelled engines are often run [[Air-fuel ratio|fuel-rich]], which lowers combustion temperatures. This reduces heat loads on the engine and allows lower cost materials and a simplified cooling system. This can also ''increase'' performance by lowering the average molecular weight of the exhaust and increasing the efficiency with which combustion heat is converted to kinetic exhaust energy.

==Chemistry==
[[Rocket propellant]]s require a high energy per unit mass ([[specific energy]]), which must be balanced against the tendency of highly energetic propellants to spontaneously explode. Assuming that the chemical potential energy of the propellants can be safely stored, the combustion process results in a great deal of heat being released. A significant fraction of this heat is transferred to kinetic energy in the engine nozzle, propelling the rocket forward in combination with the mass of combustion products released.

Ideally all the reaction energy appears as kinetic energy of the exhaust gases, as exhaust velocity is the single most important performance parameter of an engine. However, real exhaust species are [[molecule]]s, which typically have translation, vibrational, and [[rotational modes]] with which to dissipate energy. Of these, only translation can do useful work to the vehicle, and while energy does transfer between modes this process occurs on a timescale far in excess of the time required for the exhaust to leave the nozzle.

The more [[chemical bond]]s an exhaust molecule has, the more rotational and vibrational modes it will have. Consequently, it is generally desirable for the exhaust species to be as simple as possible, with a diatomic molecule composed of light, abundant atoms such as H2 being ideal in practical terms. However, in the case of a chemical rocket, hydrogen is a reactant and [[reducing agent]], not a product. An [[oxidizing agent]], most typically oxygen or an oxygen-rich species, must be introduced into the combustion process, adding mass and chemical bonds to the exhaust species.

An additional advantage of light molecules is that they may be accelerated to high velocity at temperatures that can be contained by currently available materials - the high gas temperatures in rocket engines pose serious problems for the engineering of survivable motors.

Liquid [[hydrogen]] (LH2) and [[oxygen]] (LOX, or LO2), are the most effective propellants in terms of exhaust velocity that have been widely used to date, though a few exotic combinations involving boron or liquid ozone are potentially somewhat better in theory if various practical problems could be solved.<ref>[http://yarchive.net/space/rocket/fuels/fuel_ratio.html Newsgroup correspondence], 1998–99</ref>

When computing the specific reaction energy of a given propellant combination, the entire mass of the propellants (both fuel and oxidiser) must be included. The exception is in the case of air-breathing engines, which use atmospheric oxygen and consequently have to carry less mass for a given energy output. Fuels for car or [[turbojet engine]]s have a much better effective energy output per unit mass of propellant that must be carried, but are similar per unit mass of fuel.

Computer programs that predict the performance of propellants in rocket engines are available.<ref>[http://rocketworkbench.sourceforge.net/equil.phtml Complex chemical equilibrium and rocket performance calculations], Cpropep-Web</ref><ref>[http://propulsion-analysis.com/ Tool for Rocket Propulsion Analysis], RPA</ref><ref>[https://web.archive.org/web/20000901045039/http://www.grc.nasa.gov/WWW/CEAWeb/ NASA Computer program Chemical Equilibrium with Applications], CEA</ref>

==Ignition==
{{Further|Combustion}}
With liquid and hybrid rockets, immediate ignition of the propellants as they first enter the combustion chamber is essential.

With liquid propellants (but not gaseous), failure to ignite within milliseconds usually causes too much liquid propellant to be inside the chamber, and if/when ignition occurs the amount of hot gas created can exceed the maximum design pressure of the chamber, causing a catastrophic failure of the pressure vessel. This is sometimes called a ''[[hard start]]'' or a ''rapid unscheduled disassembly'' (RUD).<ref name=aw20121126>
{{cite news |last=Svitak|first=Amy |title=Falcon 9 RUD? |url=http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385Post:c973f72f-55d3-4374-b722-df31a8d333e6 |archive-url=https://web.archive.org/web/20140321053215/http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385Post:c973f72f-55d3-4374-b722-df31a8d333e6 |url-status=dead |archive-date=2014-03-21 |access-date=2014-03-21 |newspaper=Aviation Week |date=2012-11-26 }}</ref>

Ignition can be achieved by a number of different methods; a pyrotechnic charge can be used, a plasma torch can be used,{{citation needed|date=October 2016}} or electric spark ignition<ref name=nsf20161003>
{{cite news |last=Belluscio|first=Alejandro G. |title=ITS Propulsion – The evolution of the SpaceX Raptor engine |work=[[NASASpaceFlight.com]] |date=2016-10-03 |url=https://www.nasaspaceflight.com/2016/10/its-propulsion-evolution-raptor-engine/ |access-date=2016-10-03 }}</ref> may be employed. Some fuel/oxidiser combinations ignite on contact ([[hypergolic]]), and non-hypergolic fuels can be "chemically ignited" by priming the fuel lines with hypergolic propellants (popular in Russian engines).

Gaseous propellants generally will not cause [[hard start]]s, with rockets the total injector area is less than the throat thus the chamber pressure tends to ambient prior to ignition and high pressures cannot form even if the entire chamber is full of flammable gas at ignition.

Solid propellants are usually ignited with one-shot pyrotechnic devices and combustion usually proceeds through total consumption of the propellants.<ref name=Sutton/>

Once ignited, rocket chambers are self-sustaining and igniters are not needed and combustion usually proceeds through total consumption of the propellants. Indeed, chambers often spontaneously reignite if they are restarted after being shut down for a few seconds. Unless designed for re-ignition, when cooled, many rockets cannot be restarted without at least minor maintenance, such as replacement of the pyrotechnic igniter or even refueling of the propellants.<ref name=Sutton/>

==Jet physics==
[[File:Armadillo Aerospace Pixel Hover.jpg|thumb|right|[[Quad (rocket)|Armadillo Aerospace's quad vehicle]] showing visible banding (shock diamonds) in the exhaust jet]]
Rocket jets vary depending on the rocket engine, design altitude, altitude, thrust and other factors.

Carbon-rich exhausts from kerosene-based fuels such as [[RP-1]] are often orange in colour due to the [[black-body radiation]] of the unburnt particles, in addition to the blue [[Swan band]]s. [[high test peroxide|Peroxide]] oxidiser-based rockets and hydrogen rocket jets contain largely [[steam]] and are nearly invisible to the naked eye but shine brightly in the [[ultraviolet]] and [[infrared]] ranges. Jets from [[solid-propellant rocket]]s can be highly visible, as the propellant frequently contains metals such as elemental aluminium which burns with an orange-white flame and adds energy to the combustion process. Rocket engines which burn liquid hydrogen and oxygen will exhibit a nearly transparent exhaust, due to it being mostly [[superheated steam]] (water vapour), plus some unburned hydrogen.

The nozzle is usually over-expanded at sea level, and the exhaust can exhibit visible [[shock diamonds]] through a [[schlieren#Schlieren flow visualization|schlieren effect]] caused by the [[incandescence]] of the exhaust gas.

The shape of the jet varies for a fixed-area nozzle as the expansion ratio varies with altitude: at high altitude all rockets are grossly under-expanded, and a quite small percentage of exhaust gases actually end up expanding forwards.

==Types of rocket engines==

===Physically powered===
{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Water rocket]]
| Partially filled pressurised carbonated drinks container with tail and nose weighting
| Very simple to build
| Altitude typically limited to a few hundred feet or so (world record is 830 meters, or 2,723 feet)
|-
! [[Cold gas thruster]]
| A non-combusting form, used for [[vernier thruster]]s
| Non-contaminating exhaust
| Extremely low performance
|}

===Chemically powered===
{{See also|Liquid rocket propellant}}

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Solid-propellant rocket]]
| Ignitable, self-sustaining solid fuel/oxidiser mixture ("grain") with central hole and nozzle
| Simple, often no [[moving parts]], reasonably good mass fraction, reasonable [[Specific Impulse|''I''sp]]. A thrust schedule can be designed into the grain.
| Throttling, burn termination, and reignition require special designs. Handling issues from ignitable mixture. Lower performance than liquid rockets. If grain cracks it can block nozzle with disastrous results. Grain cracks burn and widen during burn. Refueling harder than simply filling tanks. Cannot be turned off after ignition; will fire until all solid fuel is depleted.
|-
! [[Hybrid-propellant rocket]]
| Separate oxidiser/fuel; typically the oxidiser is liquid and kept in a tank and the fuel is solid.
| Quite simple, solid fuel is essentially inert without oxidiser, safer; cracks do not escalate, throttleable and easy to switch off.
| Some oxidisers are monopropellants, can explode in own right; mechanical failure of solid propellant can block nozzle (very rare with rubberised propellant), central hole widens over burn and negatively affects mixture ratio.
|-
! [[Monopropellant rocket]]
| Propellant (such as hydrazine, hydrogen peroxide or nitrous oxide) flows over a catalyst and exothermically decomposes; hot gases are emitted through nozzle.
| Simple in concept, throttleable, low temperatures in combustion chamber
| Catalysts can be easily contaminated, monopropellants can detonate if contaminated or provoked, [[Specific Impulse|''I''sp]] is perhaps 1/3 of best liquids
|-
! [[Liquid bipropellant rocket engine|Bipropellant rocket]]
| Two fluid (typically liquid) propellants are introduced through injectors into combustion chamber and burnt.
| Up to ~99% efficient combustion with excellent mixture control, throttleable, can be used with turbopumps which permits incredibly lightweight tanks, can be safe with extreme care
| Pumps needed for high performance are expensive to design, huge thermal fluxes across combustion chamber wall can impact reuse, failure modes include major explosions, a lot of plumbing is needed.
|-
! [[Methane-oxygen gaseous thruster|Gas-gas rocket]]
| A bipropellant thruster using gas propellant for both the oxidiser and fuel
| Higher-performance than cold gas thrusters
| Lower performance than liquid-based engines
|-
! [[Dual mode propulsion rocket]]
| Rocket takes off as a bipropellant rocket, then turns to using just one propellant as a monopropellant.
| Simplicity and ease of control
| Lower performance than bipropellants
|-
! [[Tripropellant rocket]]
| Three different propellants (usually hydrogen, hydrocarbon, and liquid oxygen) are introduced into a combustion chamber in variable mixture ratios, or multiple engines are used with fixed propellant mixture ratios and throttled or shut down
| Reduces take-off weight, since hydrogen is lighter; combines good thrust to weight with high average [[specific impulse|''I''sp]], improves payload for launching from Earth by a sizeable percentage
| Similar issues to bipropellant, but with more plumbing, more research and development
|-
! [[Air-augmented rocket]]
| Essentially a ramjet where intake air is compressed and burnt with the exhaust from a rocket
| Mach 0 to Mach 4.5+ (can also run exoatmospheric), good efficiency at Mach 2 to 4
| Similar efficiency to rockets at low speed or exoatmospheric, inlet difficulties, a relatively undeveloped and unexplored type, cooling difficulties, very noisy, thrust/weight ratio is similar to ramjets.
|-
! [[Turborocket]]
| A combined cycle turbojet/rocket where an additional oxidiser such as oxygen is added to the airstream to increase maximum altitude
| Very close to existing designs, operates in very high altitude, wide range of altitude and airspeed
| Atmospheric airspeed limited to same range as turbojet engine, carrying oxidiser like [[LOX]] can be dangerous. Much heavier than simple rockets.
|-
! [[Precooled jet engine]] / [[liquid air cycle engine|LACE]] (combined cycle with rocket)
| Intake air is chilled to very low temperatures at inlet before passing through a ramjet or turbojet engine. Can be combined with a rocket engine for orbital insertion.
| Easily tested on ground. High thrust/weight ratios are possible (~14) together with good fuel efficiency over a wide range of airspeeds, mach 0–5.5+; this combination of efficiencies may permit launching to orbit, single stage, or very rapid intercontinental travel.
| Exists only at the lab prototyping stage. Examples include [[RB545]], [[Reaction Engines SABRE|SABRE]], [[ATREX]]
|}

===Electrically powered===
{{Main|Electrically powered spacecraft propulsion}}
{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Resistojet rocket]] (electric heating)
| Energy is imparted to a usually inert fluid serving as reaction mass via [[Joule heating]] of a heating element. May also be used to impart extra energy to a monopropellant.
| Efficient where electrical power is at a lower premium than mass. Higher [[specific impulse|''I''sp]] than monopropellant alone, about 40% higher.
| Requires a lot of power, hence typically yields low thrust.
|-
! [[Arcjet rocket]] (chemical burning aided by electrical discharge)
| Identical to resistojet except the heating element is replaced with an electrical arc, eliminating the physical requirements of the heating element.
| 1,600 seconds [[specific impulse|''I''sp]]
| Very low thrust and high power, performance is similar to [[ion drive]].
|-
![[Variable specific impulse magnetoplasma rocket]]
| Microwave heated plasma with magnetic throat/nozzle
| Variable ''I''sp from 1,000 seconds to 10,000 seconds
| Similar thrust/weight ratio with ion drives (worse), thermal issues, as with ion drives very high power requirements for significant thrust, really needs advanced nuclear reactors, never flown, requires low temperatures for superconductors to work
|-
! [[Pulsed plasma thruster]] (electric arc heating; emits plasma)
| Plasma is used to erode a solid propellant
| High ''I''sp, can be pulsed on and off for attitude control
| Low energetic efficiency
|-
! [[Ion thruster|Ion propulsion system]]
| High voltages at ground and plus sides
| Powered by battery
| Low thrust, needs high voltage
|}

===Thermal===

====Preheated====
{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Hot water rocket]]
| Hot water is stored in a tank at high temperature / pressure and turns to steam in nozzle
| Simple, fairly safe
| Low overall performance due to heavy tank; [[specific impulse|''I''sp]] under 200 seconds
|}

====Solar thermal====

The [[solar thermal rocket]] would make use of solar power to directly heat [[reaction mass]], and therefore does not require an electrical generator as most other forms of solar-powered propulsion do. A solar thermal rocket only has to carry the means of capturing solar energy, such as [[Concentrating solar power|concentrator]]s and [[mirror]]s. The heated propellant is fed through a conventional rocket nozzle to produce thrust. The engine thrust is directly related to the surface area of the solar collector and to the local intensity of the solar radiation and inversely proportional to the ''I''sp.

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Solar thermal rocket]]
| Propellant is heated by solar collector
| Simple design. Using hydrogen propellant, 900 seconds of [[specific impulse|''I''sp]] is comparable to nuclear thermal rocket, without the problems and complexity of controlling a fission reaction.{{citation needed|date=January 2011}} Ability to [[Solar thermal rocket#Proposed solar-thermal space systems|productively use]] waste gaseous [[hydrogen]]—an inevitable byproduct of long-term [[liquid hydrogen]] storage in the [[Radiative heat transfer|radiative heat]] environment of space—for both [[orbital stationkeeping]] and [[Spacecraft attitude control|attitude control]].<ref name=aiaa20100902>{{cite web|last=Zegler|first=Frank |title=Evolving to a Depot-Based Space Transportation Architecture |url=http://www.ulalaunch.com/site/docs/publications/DepotBasedTransportationArchitecture2010.pdf |archive-url=https://web.archive.org/web/20110717150155/http://www.ulalaunch.com/site/docs/publications/DepotBasedTransportationArchitecture2010.pdf |url-status=dead |archive-date=2011-07-17 |work=AIAA SPACE 2010 Conference & Exposition |publisher=AIAA |access-date=2011-01-25 |author2=Bernard Kutter |date=2010-09-02 }} See page 3.</ref>
| Only useful in space, as thrust is fairly low, but hydrogen has not been traditionally thought to be easily stored in space,<ref name=aiaa20100902/> otherwise moderate/low [[Specific impulse|''I''sp]] if higher–molecular-mass propellants are used.
|}

====Beamed thermal====

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Laser propulsion|Light-beam-powered rocket]]
| Propellant is heated by light beam (often laser) aimed at vehicle from a distance, either directly or indirectly via heat exchanger
| Simple in principle, in principle very high exhaust speeds can be achieved
| ~1 MW of power per kg of payload is needed to achieve orbit, relatively high accelerations, lasers are blocked by clouds, fog, reflected laser light may be dangerous, pretty much needs hydrogen monopropellant for good performance which needs heavy tankage, some designs are limited to ~600 seconds due to reemission of light since propellant/heat exchanger gets white hot
|-
! [[Beam-powered propulsion|Microwave-beam-powered rocket]]
| Propellant is heated by microwave beam aimed at vehicle from a distance
| [[Specific impulse|''I''sp]] is comparable to Nuclear Thermal rocket combined with T/W comparable to conventional rocket. While LH2 propellant offers the highest Isp and rocket payload fraction, ammonia or methane are economically superior for earth-to-orbit rockets due to their particular combination of high density and Isp. [[Single-stage-to-orbit|SSTO]] operation is possible with these propellants even for small rockets, so there are no location, trajectory and shock constraints added by the rocket staging process. Microwaves are 10-100× cheaper in $/watt than lasers and have all-weather operation at frequencies below 10 GHz.
| 0.3–3{{nbsp}}MW of power per kg of payload is needed to achieve orbit depending on the propellant,<ref>{{cite web|url=http://parkinresearch.com/microwave-thermal-rockets/|title=Microwave Thermal Rockets|last=Parkin|first=Kevin|access-date=8 December 2016}}</ref> and this incurs infrastructure cost for the beam director plus related R&D costs. Concepts operating in the millimeter-wave region have to contend with weather availability and high altitude beam director sites as well as effective transmitter diameters measuring 30–300 meters to propel a vehicle to LEO. Concepts operating in X-band or below must have effective transmitter diameters measured in kilometers to achieve a fine enough beam to follow a vehicle to LEO. The transmitters are too large to fit on mobile platforms and so microwave-powered rockets are constrained to launch near fixed beam director sites.
|}

====Nuclear thermal====

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Radioisotope rocket|Radioisotope rocket/"Poodle thruster"]] (radioactive decay energy)
| Heat from radioactive decay is used to heat hydrogen
| About 700–800 seconds, almost no moving parts
| Low thrust/weight ratio.
|-
! [[Nuclear thermal rocket]] (nuclear fission energy)
| Propellant (typically, hydrogen) is passed through a nuclear reactor to heat to high temperature
| [[Specific impulse|''I''sp]] can be high, perhaps 900 seconds or more, above unity thrust/weight ratio with some designs
| Maximum temperature is limited by materials technology, some radioactive particles can be present in exhaust in some designs, nuclear reactor shielding is heavy, unlikely to be permitted from surface of the Earth, thrust/weight ratio is not high.
|}

===Nuclear===
[[Nuclear propulsion]] includes a wide variety of [[spacecraft propulsion|propulsion]] methods that use some form of [[nuclear reaction]] as their primary power source. Various types of nuclear propulsion have been proposed, and some of them tested, for spacecraft applications:

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Gas core reactor rocket]] (nuclear fission energy)
| Nuclear reaction using a gaseous state fission reactor in intimate contact with propellant
| Very hot propellant, not limited by keeping reactor solid, [[Specific Impulse|''I''sp]] between 1,500 and 3,000 seconds but with very high thrust
| Difficulties in heating propellant without losing fissionables in exhaust, massive thermal issues particularly for nozzle/throat region, exhaust almost inherently highly radioactive. Nuclear lightbulb variants can contain fissionables, but cut [[Specific Impulse|''I''sp]] in half.
|-
! [[Fission-fragment rocket]] (nuclear fission energy)
| Fission products are directly exhausted to give thrust.
|
| Theoretical only at this point.
|-
! [[Fission sail]] (nuclear fission energy)
| A sail material is coated with fissionable material on one side.
| No moving parts, works in deep space
| Theoretical only at this point.
|-
! [[Nuclear salt-water rocket]] (nuclear fission energy)
| Nuclear salts are held in solution, caused to react at nozzle
| Very high [[Specific Impulse|''I''sp]], very high thrust
| Thermal issues in nozzle, propellant could be unstable, highly radioactive exhaust. Theoretical only at this point.
|-
! [[Nuclear pulse propulsion]] (exploding fission/fusion bombs)
| Shaped nuclear bombs are detonated behind vehicle and blast is caught by a 'pusher plate'
| Very high [[Specific Impulse|''I''sp]], very high thrust/weight ratio, no show stoppers are known for this technology.
| Never been tested, pusher plate may [[spall|throw off fragments]] due to shock, minimum size for nuclear bombs is still pretty big, expensive at small scales, nuclear treaty issues, fallout when used below Earth's magnetosphere.
|-
! [[Antimatter catalyzed nuclear pulse propulsion]] (fission and/or fusion energy)
| Nuclear pulse propulsion with antimatter assist for smaller bombs
| Smaller sized vehicle might be possible
| Containment of antimatter, production of antimatter in macroscopic quantities is not currently feasible. Theoretical only at this point.
|-
! [[Fusion rocket]] (nuclear fusion energy)
| Fusion is used to heat propellant
| Very high exhaust velocity
| Largely beyond current state of the art.
|-
! [[Antimatter rocket]] (annihilation energy)
| Antimatter annihilation heats propellant
| Extremely energetic, very high theoretical exhaust velocity
| Problems with antimatter production and handling; energy losses in [[neutrino]]s, [[gamma ray]]s, [[muon]]s; thermal issues. Theoretical only at this point.
|}

==History of rocket engines==
{{main|History of rockets}}
According to the writings of the Roman [[Aulus Gellius]], the earliest known example of [[jet propulsion]] was in c. 400 BC, when a [[Greek people|Greek]] [[Pythagoreanism|Pythagorean]] named [[Archytas]], propelled a wooden bird along wires using steam.<ref>{{cite book |author=Leofranc Holford-Strevens|title=Aulus Gellius: An Antonine Author and his Achievement|publisher=Oxford University Press|edition=Revised paperback |date=2005 |isbn=0-19-928980-8 }}
</ref><ref>{{cite EB1911 |wstitle=Archytas |volume=2 |page=446}}</ref> However, it was not powerful enough to take off under its own thrust.

The ''[[aeolipile]]'' described in the first century BC, often known as ''[[Hero's engine]]'', consisted of a pair of [[steam rocket]] nozzles mounted on a [[Bearing (mechanical)|bearing]]. It was created almost two millennia before the [[Industrial Revolution]] but the principles behind it were not well understood, and it was not developed into a practical power source.

The availability of [[black powder]] to propel projectiles was a precursor to the development of the first solid rocket. Ninth Century [[Chinese people|Chinese]] [[Taoist]] [[Alchemy|alchemists]] discovered black powder in a search for the [[elixir of life]]; this accidental discovery led to [[fire arrow]]s which were the first rocket engines to leave the ground.

It is stated{{By whom|date=May 2022}} that "the reactive forces of incendiaries were probably not applied to the propulsion of projectiles prior to the 13th century".{{Citation needed|date=May 2024}} A turning point in rocket technology emerged with a short manuscript entitled ''Liber Ignium ad Comburendos Hostes'' (abbreviated as ''The Book of Fires''). The manuscript is composed of recipes for creating incendiary weapons from the mid-eighth to the end of the thirteenth centuries—two of which are rockets. The first recipe calls for one part of colophonium and sulfur added to six parts of saltpeter (potassium nitrate) dissolved in [[Lauraceae|laurel]] oil, then inserted into hollow wood and lit to "fly away suddenly to whatever place you wish and burn up everything". The second recipe combines one pound of sulfur, two pounds of charcoal, and six pounds of saltpeter—all finely powdered on a marble slab. This powder mixture is packed firmly into a long and narrow case. The introduction of saltpeter into pyrotechnic mixtures connected the shift from hurled [[Greek fire]] into self-propelled rocketry.<ref>{{cite book|last1=Von Braun|last2= Ordway III|first1=Wernher |first2= Frederick I.|title=The Rockets' Red Glare|url=https://archive.org/details/rocketsredglare0000vonb|url-access=registration|date=1976|publisher=Anchor Press/ Doubleday|location=Garden City, New York|isbn=978-0-385-07847-4|page=[https://archive.org/details/rocketsredglare0000vonb/page/5 5]}}</ref>

Articles and books on the subject of rocketry appeared increasingly from the fifteenth through seventeenth centuries. In the sixteenth century, German military engineer Conrad Haas (1509–1576) wrote a manuscript which introduced the construction of multi-staged rockets.<ref>{{cite book|last1=Von Braun|last2= Ordway III|first1=Wernher |first2= Frederick I.|title=The Rockets' Red Glare|url=https://archive.org/details/rocketsredglare0000vonb|url-access=registration|date=1976|publisher=Anchor Press/ Doubleday|location=Garden City, New York|isbn=978-0-385-07847-4|page=[https://archive.org/details/rocketsredglare0000vonb/page/11 11]}}</ref>

Rocket engines were also put in use by [[Tippu Sultan]], the king of [[Mysore]]. These usually consisted of a tube of soft hammered iron about {{convert|8|in|cm|abbr=on}} long and {{convert|1+1/2|-|3|in|cm|abbr=on}} diameter, closed at one end, packed with black powder propellant and strapped to a shaft of bamboo about {{convert|4|ft|cm|abbr=on}} long. A rocket carrying about one pound of powder could travel almost {{convert|1000|yd|m}}. These 'rockets', fitted with swords, would travel several meters in the air before coming down with sword edges facing the enemy. These were used very effectively against the British empire.

===Modern rocketry===
Slow development of this technology continued up to the later 19th century, when Russian [[Konstantin Tsiolkovsky]] first wrote about [[liquid-propellant rocket|liquid-fuelled rocket engines]]. He was the first to develop the [[Tsiolkovsky rocket equation]], though it was not published widely for some years.

The modern solid- and liquid-fuelled engines became realities early in the 20th century, thanks to the American physicist [[Robert Goddard (scientist)|Robert Goddard]]. Goddard was the first to use a [[De Laval nozzle]] on a solid-propellant (gunpowder) rocket engine, doubling the thrust and increasing the efficiency by a factor of about twenty-five. This was the birth of the modern rocket engine. He calculated from his independently derived rocket equation that a reasonably sized rocket, using solid fuel, could place a one-pound payload on the Moon.

===The era of liquid-fuel rocket engines===
Goddard began to use liquid propellants in 1921, and in 1926 became the first to launch a liquid-fuelled rocket. Goddard pioneered the use of the De Laval nozzle, lightweight propellant tanks, small light turbopumps, thrust vectoring, the smoothly-throttled liquid fuel engine, regenerative cooling, and curtain cooling.<ref name=Sutton/>{{rp|247–266}}

During the late 1930s, German scientists, such as [[Wernher von Braun]] and [[Hellmuth Walter]], investigated installing liquid-fuelled rockets in military aircraft ([[Heinkel He 112]], [[Heinkel He 111|He 111]], [[Heinkel He 176|He 176]] and [[Messerschmitt Me 163]]).<ref>{{cite book|author=Lutz Warsitz|title=The First Jet Pilot – The Story of German Test Pilot Erich Warsitz|publisher=Pen and Sword Ltd.|date=2009|isbn=978-1-84415-818-8}} Includes von Braun's and Hellmuth Walter's experiments with rocket aircraft. [http://www.pen-and-sword.co.uk/?product_id=1762 English edition.]</ref>

The turbopump was employed by German scientists in World War II. Until then cooling the nozzle had been problematic, and the [[V-2 rocket|A4]] ballistic missile used dilute alcohol for the fuel, which reduced the combustion temperature sufficiently.

[[Staged combustion cycle (rocket)|Staged combustion]] (''Замкнутая схема'') was first proposed by [[Aleksei Mihailovich Isaev|Alexey Isaev]] in 1949. The first staged combustion engine was the S1.5400 used in the Soviet planetary rocket, designed by Melnikov, a former assistant to Isaev.<ref name=Sutton>{{cite book|last=Sutton|first=George P.|title=History of Liquid Propellant Rocket Engines|date=2005|publisher=American Institute of Aeronautics and Astronautics|location=Reston, Virginia}}</ref> About the same time (1959), [[Nikolai Dmitriyevich Kuznetsov|Nikolai Kuznetsov]] began work on the closed cycle engine [[NK-9]] for Korolev's orbital ICBM, GR-1. Kuznetsov later evolved that design into the [[NK-15]] and [[NK-33]] engines for the unsuccessful Lunar [[N1 rocket]].

In the West, the first laboratory staged-combustion test engine was built in Germany in 1963, by [[Ludwig Boelkow]].

Liquid hydrogen engines were first successfully developed in America: the [[RL-10]] engine first flew in 1962. Its successor, the [[Rocketdyne J-2]], was used in the [[Apollo program]]'s [[Saturn V]] rocket to send humans to the Moon. The high specific impulse and low density of liquid hydrogen lowered the upper stage mass and the overall size and cost of the vehicle.

The record for most engines on one rocket flight is 44, set by NASA in 2016 on a [[Black Brant (rocket)|Black Brant]].<ref>{{Cite web | url=https://www.space.com/33810-nasa-world-record-most-rocket-engines.html |title = NASA and Navy Set World Record for Most Engines in One Rocket Flight|website = [[Space.com]]|date = 19 August 2016}}</ref>

==See also==
* [[Comparison of orbital rocket engines]]
* [[Rotating detonation engine]]
* [[Jet damping]], an effect of the exhaust jet of a rocket that tends to slow a vehicle's rotation speed
* [[Model rocket motor classification]] lettered engines
* [[NERVA]] (Nuclear Energy for Rocket Vehicle Applications), a US nuclear thermal rocket programme
* [[Photon rocket]]
* [[Project Prometheus]], NASA development of nuclear propulsion for long-duration spaceflight, begun in 2003
* [[Rocket propulsion technologies (disambiguation)]]

==Notes==
{{reflist|group =notes}}

==References==
{{reflist}}

==External links==
{{commons category|Rocket engines}}
{{Wiktionary}}
*[https://web.archive.org/web/20071009153749/http://www.pwrengineering.com/articles/longterm.htm Designing for rocket engine life expectancy]
*[https://web.archive.org/web/20071007070232/http://www.pwrengineering.com/articles/plume.htm Rocket Engine performance analysis with Plume Spectrometry]
*[https://web.archive.org/web/20071009151907/http://www.pwrengineering.com/articles/heart.htm Rocket Engine Thrust Chamber technical article]
*[http://www.fxsolver.com/browse/formulas/Net+Thrust+of+a+Rocket+Engine Net Thrust of a Rocket Engine calculator]
*[http://www.lpre.de/resources/software/RPA_en.htm Design Tool for Liquid Rocket Engine Thermodynamic Analysis]
*[http://www.braeunig.us/space/propuls.htm Rocket & Space Technology - Rocket Propulsion]
*[http://www.erichwarsitz.com/ The official website of test pilot Erich Warsitz (world's first jet pilot) which includes videos of the Heinkel He 112 fitted with von Braun's and Hellmuth Walter's rocket engines (as well as the He 111 with ATO Units)]

{{Rocket engines}}
{{Aircraft gas turbine engine components}}
{{Heat engines|state=uncollapsed}}

{{Authority control}}

{{DEFAULTSORT:Rocket Engine}}
[[Category:Aerospace technologies]]
[[Category:Rocket engines| ]]

Rocket engine

2024-08-17T16:42:08Z

88.163.124.35: /* Combustion instabilities */ to F-1

{{Short description|Non-air breathing jet engine used to propel a missile or vehicle}}
{{Use British English|date=February 2019}}
[[File:RS-68 rocket engine test.jpg|thumb|right|[[RS-68]] being tested at NASA's [[Stennis Space Center]]]]
[[File:Viking 5C rocketengine.jpg|thumb|right|[[Viking (rocket engine)|Viking 5C rocket engine]] used on [[Ariane 1]] through [[Ariane 4]]]]

A '''rocket engine''' uses stored [[rocket propellant]]s as the [[reaction mass]] for forming a high-speed propulsive [[Jet (fluid)|jet]] of fluid, usually high-temperature gas. [[Rocket]] engines are [[reaction engine]]s, producing thrust by ejecting mass rearward, in accordance with [[Newton's third law]]. Most rocket engines use the [[combustion]] of reactive chemicals to supply the necessary energy, but non-combusting forms such as [[cold gas thruster]]s and [[nuclear thermal rocket]]s also exist. Vehicles propelled by rocket engines are commonly used by [[ballistic missiles]] (they normally use [[solid fuel]]) and [[rocket]]s. Rocket vehicles carry their own [[oxidiser]], unlike most combustion engines, so rocket engines can be used in a [[vacuum]] to propel [[spacecraft]] and [[ballistic missile]]s.

Compared to other types of jet engine, rocket engines are the lightest and have the highest thrust, but are the least propellant-efficient (they have the lowest [[specific impulse]]). The ideal exhaust is [[hydrogen]], the lightest of all elements, but chemical rockets produce a mix of heavier species, reducing the exhaust velocity.

Rocket engines become more efficient at high speeds, due to the [[Oberth effect]].<ref name=ways>{{cite web|url=https://archive.org/details/nasa_techdoc_19720008133|title=Ways to spaceflight|volume=NASA TT F-622|others=Translation of the German language original "Wege zur Raumschiffahrt," (1920)|location=Tunis, Tunisia|year=1970|author=Hermann Oberth|publisher=Agence Tunisienne de Public-Relations}}</ref>

==Terminology==
Here, "rocket" is used as an abbreviation for "rocket engine".

'''[[Thermal rocket]]s''' use an inert propellant, heated by electricity ([[electrothermal propulsion]]) or a nuclear reactor ([[nuclear thermal rocket]]).

'''Chemical rockets''' are powered by [[exothermic]] [[redox chemistry|reduction-oxidation]] chemical reactions of the propellant:

*'''[[Solid-fuel rocket]]s''' (or '''solid-propellant rockets''' or '''motors''') are chemical rockets which use propellant in a [[solid|solid state]].
*'''[[Liquid-propellant rocket]]s''' use one or more propellants in a [[liquid state]] fed from tanks.
*'''[[Hybrid rocket]]s''' use a solid propellant in the combustion chamber, to which a second liquid or gas [[oxidizing agent|oxidiser]] or propellant is added to permit combustion.
*'''[[Monopropellant rocket]]s''' use a single propellant decomposed by a [[catalyst]]. The most common monopropellants are [[hydrazine]] and [[hydrogen peroxide]].

==Principle of operation==
[[File:Liquid-Fuel Rocket Diagram.svg|thumb|upright=1.25|Simplified diagram of a liquid-fuel rocket: {{olist |
|[[Liquid rocket propellant|Liquid fuel]] tank
|[[Oxidizing agent|Liquid oxidiser]] tank
|Pumps feed fuel and oxidiser under high pressure.
|[[Combustion chamber]] mixes and burns the propellants.
|[[Propelling nozzle|Exhaust nozzle]] expands and accelerates the gas jet to produce thrust.
|Exhaust exits nozzle.
}}]]

[[File:Solid-Fuel Rocket Diagram.svg|thumb|upright=1.25|Simplified diagram of a solid-fuel rocket: {{olist
|Solid [[Rocket propellant#Solid chemical propellants|fuel–oxidiser mixture]] (propellant) packed into casing
|[[Pyrotechnic initiator|Igniter]] initiates propellant combustion.
|Central hole in propellant acts as the [[combustion chamber]].
|[[Propelling nozzle|Exhaust nozzle]] expands and accelerates the gas jet to produce thrust.
|Exhaust exits nozzle.
}}]]
Rocket engines produce thrust by the expulsion of an exhaust [[fluid]] that has been accelerated to high speed through a [[propelling nozzle]]. The fluid is usually a gas created by high pressure ({{convert|10|to|300|bar|psi|order=flip|adj=on}}) combustion of solid or liquid [[Rocket propellant|propellants]], consisting of [[fuel]] and [[oxidizing agent|oxidiser]] components, within a [[combustion chamber]]. As the gases expand through the nozzle, they are accelerated to very high ([[supersonic]]) speed, and the reaction to this pushes the engine in the opposite direction. Combustion is most frequently used for practical rockets, as the laws of [[thermodynamics]] (specifically [[Carnot's theorem (thermodynamics)|Carnot's theorem]]) dictate that high temperatures and pressures are desirable for the best [[thermal efficiency]]. [[Nuclear thermal rocket]]s are capable of higher efficiencies, but currently have [[Nuclear thermal rocket#Risks|environmental problems]] which preclude their routine use in the Earth's atmosphere and [[cislunar space]].

For [[model rocket]]ry, an available alternative to combustion is the [[water rocket]] pressurized by compressed air, [[carbon dioxide]], [[nitrogen]], or any other readily available, inert gas.

===Propellant===
Rocket propellant is mass that is stored, usually in some form of tank, or within the combustion chamber itself, prior to being ejected from a rocket engine in the form of a fluid jet to produce thrust.

Chemical rocket propellants are the most commonly used. These undergo exothermic chemical reactions producing a hot gas jet for propulsion. Alternatively, a chemically inert [[reaction mass]] can be heated by a high-energy power source through a heat exchanger in lieu of a combustion chamber.

[[Solid rocket]] propellants are prepared in a mixture of fuel and oxidising components called ''grain'', and the propellant storage casing effectively becomes the combustion chamber.

===Injection===
[[Liquid-propellant rocket|Liquid-fuelled rockets]] force separate fuel and oxidiser components into the combustion chamber, where they mix and burn. [[Hybrid rocket]] engines use a combination of solid and liquid or gaseous propellants. Both liquid and hybrid rockets use ''[[Liquid-fuel rocket#Injectors|injectors]]'' to introduce the propellant into the chamber. These are often an array of simple [[jet (nozzle)|jet]]s – holes through which the propellant escapes under pressure; but sometimes may be more complex spray nozzles. When two or more propellants are injected, the jets usually deliberately cause the propellants to collide as this breaks up the flow into smaller droplets that burn more easily.

===Combustion chamber===
For chemical rockets the combustion chamber is typically cylindrical, and [[flame holder]]s, used to hold a part of the combustion in a slower-flowing portion of the combustion chamber, are not needed. The dimensions of the cylinder are such that the propellant is able to combust thoroughly; different [[rocket propellant]]s require different combustion chamber sizes for this to occur.

This leads to a number called <math>L^*</math>, the [[characteristic length]]:
:<math>L^* = \frac {V_c} {A_t}</math>
where:
*<math>V_c</math> is the volume of the chamber
*<math>A_t</math> is the area of the throat of the nozzle.
L* is typically in the range of {{convert|64|-|152|cm|in}}.

The temperatures and pressures typically reached in a rocket combustion chamber in order to achieve practical [[thermal efficiency]] are extreme compared to a [[afterburner|non-afterburning]] [[airbreathing jet engine]]. No atmospheric nitrogen is present to dilute and cool the combustion, so the propellant mixture can reach true [[stoichiometric]] ratios. This, in combination with the high pressures, means that the rate of heat conduction through the walls is very high.

In order for fuel and oxidiser to flow into the chamber, the pressure of the propellants entering the combustion chamber must exceed the pressure inside the combustion chamber itself. This may be accomplished by a variety of design approaches including [[turbopump]]s or, in simpler engines, via [[Pressure-fed cycle (rocket)|sufficient tank pressure]] to advance fluid flow. Tank pressure may be maintained by several means, including a high-pressure [[helium]] pressurization system common to many large rocket engines or, in some newer rocket systems, by a bleed-off of high-pressure gas from the engine cycle to [[autogenous pressurization|autogenously pressurize]] the propellant tanks<ref name=nsf20160927>
{{cite news |last=Bergin|first=Chris |url=https://www.nasaspaceflight.com/2016/09/spacex-reveals-mars-game-changer-colonization-plan/ |title=SpaceX reveals ITS Mars game changer via colonization plan |work=[[NASASpaceFlight.com]] |date=2016-09-27 |access-date=2016-09-27 }}</ref><ref name=sfi20160927/> For example, the self-pressurization gas system of the [[SpaceX Starship]] is a critical part of SpaceX strategy to reduce launch vehicle fluids from five in their legacy Falcon 9 vehicle family to just two in Starship, eliminating not only the helium tank pressurant but all [[hypergolic propellant]]s as well as [[nitrogen]] for cold-gas [[reaction control system|reaction-control thrusters]].<ref name=nsf20161003/>

===Nozzle===
{{Main|Rocket engine nozzle}}
[[File:Rocket thrust.svg|thumb|right|Rocket thrust is caused by pressures acting in the combustion chamber and nozzle. From Newton's third law, equal and opposite pressures act on the exhaust, and this accelerates it to high speeds.]]
The hot gas produced in the combustion chamber is permitted to escape through an opening (the "throat"), and then through a diverging expansion section. When sufficient pressure is provided to the nozzle (about 2.5–3 times ambient pressure), the nozzle ''[[choked flow|choke]]s'' and a supersonic jet is formed, dramatically accelerating the gas, converting most of the thermal energy into kinetic energy. Exhaust speeds vary, depending on the [[expansion ratio]] the nozzle is designed for, but exhaust speeds as high as ten times the [[speed of sound]] in air at sea level are not uncommon. About half of the rocket engine's thrust comes from the unbalanced pressures inside the combustion chamber, and the rest comes from the pressures acting against the inside of the nozzle (see diagram). As the gas expands ([[Adiabatic process|adiabatically]]) the pressure against the nozzle's walls forces the rocket engine in one direction while accelerating the gas in the other.

{{Anchor|opt_expansion}} 
[[File:Rocket nozzle expansion.svg|thumb|right|upright|The four expansion regimes of a de Laval nozzle:
• under-expanded
• perfectly expanded
• over-expanded
• grossly over-expanded]]
The most commonly used nozzle is the [[de Laval nozzle]], a fixed geometry nozzle with a high expansion-ratio. The large bell- or cone-shaped nozzle extension beyond the throat gives the rocket engine its characteristic shape.

The exit [[static pressure#Static pressure in fluid dynamics|static pressure]] of the exhaust jet depends on the chamber pressure and the ratio of exit to throat area of the nozzle. As exit pressure varies from the ambient (atmospheric) pressure, a choked nozzle is said to be
* '''under-expanded''' (exit pressure greater than ambient),
* '''perfectly expanded''' (exit pressure equals ambient),
* '''over-expanded''' (exit pressure less than ambient; [[shock diamond]]s form outside the nozzle), or
* '''grossly over-expanded''' (a [[shock wave]] forms inside the nozzle extension).

In practice, perfect expansion is only achievable with a variable–exit-area nozzle (since ambient pressure decreases as altitude increases), and is not possible above a certain altitude as ambient pressure approaches zero. If the nozzle is not perfectly expanded, then loss of efficiency occurs. Grossly over-expanded nozzles lose less efficiency, but can cause mechanical problems with the nozzle. Fixed-area nozzles become progressively more under-expanded as they gain altitude. Almost all de Laval nozzles will be momentarily grossly over-expanded during startup in an atmosphere.<ref name="HuzelAndHuang">{{cite book
|last = Huzel
|first = Dexter K.
|last2 = Huang
|first2 = David H.
|date = 1 January 1971
|title = NASA SP-125, Design of Liquid Propellant Rocket Engines, Second Edition
|url = https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710019929_1971019929.pdf
|publisher = NASA
|page = 
|archive-url = https://web.archive.org/web/20170324150551/https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710019929_1971019929.pdf/
|archive-date = 24 March 2017
|url-status = dead
|access-date = 7 July 2017
}}</ref>

Nozzle efficiency is affected by operation in the atmosphere because atmospheric pressure changes with altitude; but due to the supersonic speeds of the gas exiting from a rocket engine, the pressure of the jet may be either below or above ambient, and equilibrium between the two is not reached at all altitudes (see diagram).

====Back pressure and optimal expansion====
For optimal performance, the pressure of the gas at the end of the nozzle should just equal the ambient pressure: if the exhaust's pressure is lower than the ambient pressure, then the vehicle will be slowed by the difference in pressure between the top of the engine and the exit; on the other hand, if the exhaust's pressure is higher, then exhaust pressure that could have been converted into thrust is not converted, and energy is wasted.

To maintain this ideal of equality between the exhaust's exit pressure and the ambient pressure, the diameter of the nozzle would need to increase with altitude, giving the pressure a longer nozzle to act on (and reducing the exit pressure and temperature). This increase is difficult to arrange in a lightweight fashion, although is routinely done with other forms of jet engines. In rocketry a lightweight compromise nozzle is generally used and some reduction in atmospheric performance occurs when used at other than the 'design altitude' or when throttled. To improve on this, various exotic nozzle designs such as the [[plug nozzle]], [[stepped nozzles]], the [[expanding nozzle]] and the [[aerospike engine|aerospike]] have been proposed, each providing some way to adapt to changing ambient air pressure and each allowing the gas to expand further against the nozzle, giving extra thrust at higher altitudes.

When exhausting into a sufficiently low ambient pressure (vacuum) several issues arise. One is the sheer weight of the nozzle—beyond a certain point, for a particular vehicle, the extra weight of the nozzle outweighs any performance gained. Secondly, as the exhaust gases adiabatically expand within the nozzle they cool, and eventually some of the chemicals can freeze, producing 'snow' within the jet. This causes instabilities in the jet and must be avoided.

On a [[de Laval nozzle]], exhaust gas flow detachment will occur in a grossly over-expanded nozzle. As the detachment point will not be uniform around the axis of the engine, a side force may be imparted to the engine. This side force may change over time and result in control problems with the launch vehicle.

Advanced [[altitude compensating nozzle|altitude-compensating]] designs, such as the [[aerospike engine|aerospike]] or [[plug nozzle]], attempt to minimize performance losses by adjusting to varying expansion ratio caused by changing altitude.

===Propellant efficiency===
{{See also|Specific impulse}}
[[Image:Nozzle de Laval diagram.svg|thumb|right|upright|Typical temperature (T), pressure (p), and velocity (v) profiles in a de Laval Nozzle]]
For a rocket engine to be propellant efficient, it is important that the maximum pressures possible be created on the walls of the chamber and nozzle by a specific amount of propellant; as this is the source of the thrust. This can be achieved by all of:

* heating the propellant to as high a temperature as possible (using a high energy fuel, containing hydrogen and carbon and sometimes metals such as [[aluminium]], or even using nuclear energy)
* using a low specific density gas (as hydrogen rich as possible)
* using propellants which are, or decompose to, simple molecules with few degrees of freedom to maximise translational velocity

Since all of these things minimise the mass of the propellant used, and since pressure is proportional to the mass of propellant present to be accelerated as it pushes on the engine, and since from [[Newton's third law]] the pressure that acts on the engine also reciprocally acts on the propellant, it turns out that for any given engine, the speed that the propellant leaves the chamber is unaffected by the chamber pressure (although the thrust is proportional). However, speed is significantly affected by all three of the above factors and the exhaust speed is an excellent measure of the engine propellant efficiency. This is termed ''exhaust velocity'', and after allowance is made for factors that can reduce it, the '''[[effective exhaust velocity]]''' is one of the most important parameters of a rocket engine (although weight, cost, ease of manufacture etc. are usually also very important).

For aerodynamic reasons the flow goes sonic ("[[Choked flow|chokes]]") at the narrowest part of the nozzle, the 'throat'. Since the [[speed of sound]] in gases increases with the square root of temperature, the use of hot exhaust gas greatly improves performance. By comparison, at room temperature the speed of sound in air is about 340 m/s while the speed of sound in the hot gas of a rocket engine can be over 1700 m/s; much of this performance is due to the higher temperature, but additionally rocket propellants are chosen to be of low molecular mass, and this also gives a higher velocity compared to air.

Expansion in the rocket nozzle then further multiplies the speed, typically between 1.5 and 2 times, giving a highly [[collimated]] hypersonic exhaust jet. The speed increase of a rocket nozzle is mostly determined by its area expansion ratio—the ratio of the area of the exit to the area of the throat, but detailed properties of the gas are also important. Larger ratio nozzles are more massive but are able to extract more heat from the combustion gases, increasing the exhaust velocity.

===Thrust vectoring===
{{Main|Thrust vectoring}}
Vehicles typically require the overall thrust to change direction over the length of the burn. A number of different ways to achieve this have been flown:

* The entire engine is mounted on a [[hinge]] or [[gimbal]] and any propellant feeds reach the engine via low pressure flexible pipes or rotary couplings.
* Just the combustion chamber and nozzle is gimballed, the pumps are fixed, and high pressure feeds attach to the engine.
* Multiple engines (often canted at slight angles) are deployed but throttled to give the overall vector that is required, giving only a very small penalty.
* High-temperature vanes protrude into the exhaust and can be tilted to deflect the jet.

==Overall performance==
Rocket technology can combine very high thrust ([[meganewton]]s), very high exhaust speeds (around 10 times the speed of sound in air at sea level) and very high thrust/weight ratios (>100) ''simultaneously'' as well as being able to operate outside the atmosphere, and while permitting the use of low pressure and hence lightweight tanks and structure.

Rockets can be further optimised to even more extreme performance along one or more of these axes at the expense of the others.

===Specific impulse===
{{Specific impulse|align=right}}
{{Main|Specific impulse}}

The most important metric for the efficiency of a rocket engine is [[impulse (physics)|impulse]] per unit of [[propellant]], this is called [[specific impulse]] (usually written <math>I_{sp}</math>). This is either measured as a speed (the ''effective exhaust velocity'' <math>v_{e}</math> in metres/second or ft/s) or as a time (seconds). For example, if an engine producing 100 pounds of thrust runs for 320 seconds and burns 100 pounds of propellant, then the specific impulse is 320 seconds. The higher the specific impulse, the less propellant is required to provide the desired impulse.

The specific impulse that can be achieved is primarily a function of the propellant mix (and ultimately would limit the specific impulse), but practical limits on chamber pressures and the nozzle expansion ratios reduce the performance that can be achieved.

===Net thrust===
{{Main|Thrust}}
Below is an approximate equation for calculating the net thrust of a rocket engine:<ref>{{cite book|author=George P. Sutton|author2=Oscar Biblarz|name-list-style=amp|title=Rocket Propulsion Elements|edition=8th|publisher=Wiley Interscience|date=2010|isbn=9780470080245|url=https://archive.org/details/Rocket_Propulsion_Elements_8th_Edition_by_Oscar_Biblarz_George_P._Sutton/page/34/mode/2up}} See Equation 2-14.</ref>

{{block indent|<math>F_n = \dot{m}\;v_{e} = \dot{m}\;v_{e-opt} + A_{e}(p_{e} - p_{amb})</math>}}

{| border="0" cellpadding="2" style="margin-left:1em"
|-
|align=right|where:
| 
|-
!align=right|<math>\dot{m}</math>
|align=left|=  exhaust gas mass flow
|-
!align=right|<math>v_{e}</math>
|align=left|=  effective exhaust velocity (sometimes otherwise denoted as ''c'' in publications)
|-
!align=right|<math>v_{e-opt}</math>
|align=left|=  effective jet velocity when Pamb = Pe
|-
!align=right|<math>A_{e}</math>
|align=left|=  flow area at nozzle exit plane (or the plane where the jet leaves the nozzle if separated flow)
|-
!align=right|<math>p_{e}</math>
|align=left|=  static pressure at nozzle exit plane
|-
!align=right|<math>p_{amb}</math>
|align=left|=  ambient (or atmospheric) pressure
|}

Since, unlike a jet engine, a conventional rocket motor lacks an air intake, there is no 'ram drag' to deduct from the gross thrust. Consequently, the net thrust of a rocket motor is equal to the gross thrust (apart from static back pressure).

The <math>\dot{m}\;v_{e-opt}\,</math> term represents the momentum thrust, which remains constant at a given throttle setting, whereas the <math>A_{e}(p_{e} - p_{amb})\,</math> term represents the pressure thrust term. At full throttle, the net thrust of a rocket motor improves slightly with increasing altitude, because as atmospheric pressure decreases with altitude, the pressure thrust term increases. At the surface of the Earth the pressure thrust may be reduced by up to 30%, depending on the engine design. This reduction drops roughly exponentially to zero with increasing altitude.

Maximum efficiency for a rocket engine is achieved by maximising the momentum contribution of the equation without incurring penalties from over expanding the exhaust. This occurs when <math>p_{e} = p_{amb}</math>. Since ambient pressure changes with altitude, most rocket engines spend very little time operating at peak efficiency.

Since specific impulse is force divided by the rate of mass flow, this equation means that the specific impulse varies with altitude.

===Vacuum specific impulse, Isp===

Due to the specific impulse varying with pressure, a quantity that is easy to compare and calculate with is useful. Because rockets [[choked flow|choke]] at the throat, and because the supersonic exhaust prevents external pressure influences travelling upstream, it turns out that the pressure at the exit is ideally exactly proportional to the propellant flow <math> \dot{m}</math>, provided the mixture ratios and combustion efficiencies are maintained. It is thus quite usual to rearrange the above equation slightly:<ref>{{cite book|author=George P. Sutton|author2=Oscar Biblarz|name-list-style=amp|title=Rocket Propulsion Elements|edition=8th|publisher=Wiley Interscience|date=2010|isbn=9780470080245|url=https://archive.org/details/Rocket_Propulsion_Elements_8th_Edition_by_Oscar_Biblarz_George_P._Sutton/page/34/mode/2up}} See Equation 3-33.</ref>

{{block indent|<math> F_{vac} = C_f\, \dot{m}\, c^*</math>}}

and so define the ''vacuum Isp'' to be:

{{block indent|<math>v_{evac} = C_f\, c^* \,</math>}}

where:

{{block indent|1=<math>c^*</math>  =  the [[characteristic velocity]] of the combustion chamber (dependent on propellants and combustion efficiency)}}
{{block indent|1=<math>C_f</math>  =  the thrust coefficient constant of the nozzle (dependent on nozzle geometry, typically about 2)}}

And hence:
{{block indent|<math> F_n = \dot{m}\, v_{evac} - A_{e}\, p_{amb}</math>}}

===Throttling===

Rockets can be throttled by controlling the propellant combustion rate <math> \dot{m}</math> (usually measured in kg/s or lb/s). In liquid and hybrid rockets, the propellant flow entering the chamber is controlled using valves, in [[solid rocket]]s it is controlled by changing the area of propellant that is burning and this can be designed into the propellant grain (and hence cannot be controlled in real-time).

Rockets can usually be throttled down to an exit pressure of about one-third of ambient pressure<ref name=Sutton/> (often limited by flow separation in nozzles) and up to a maximum limit determined only by the mechanical strength of the engine.

In practice, the degree to which rockets can be throttled varies greatly, but most rockets can be throttled by a factor of 2 without great difficulty;<ref name=Sutton/> the typical limitation is combustion stability, as for example, injectors need a minimum pressure to avoid triggering damaging oscillations (chugging or combustion instabilities); but injectors can be optimised and tested for wider ranges.

For example, some more recent liquid-propellant engine designs that have been optimised for greater throttling capability ([[BE-3]], [[Raptor (rocket engine)|Raptor]]) can be throttled to as low as 18–20 per cent of rated thrust.<ref name="sn20150407">
{{cite news |last1=Foust|first=Jeff |title=Blue Origin Completes BE-3 Engine as BE-4 Work Continues |url=http://spacenews.com/blue-origin-completes-be-3-engine-as-be-4-work-continues/ |access-date=2016-10-20 |work=Space News |date=2015-04-07 }}</ref><ref name="sfi20160927">{{cite news |url= http://www.spaceflightinsider.com/organizations/space-exploration-technologies/elon-musk-shows-off-interplanetary-transport-system/ |title= Elon Musk Shows Off Interplanetary Transport System |publisher= Spaceflight Insider |last= Richardson |first= Derek |date= 2016-09-27 |access-date= 2016-10-20 |archive-date= 2016-10-01 |archive-url= https://web.archive.org/web/20161001225649/http://www.spaceflightinsider.com/organizations/space-exploration-technologies/elon-musk-shows-off-interplanetary-transport-system/ |url-status= dead }}</ref>

Solid rockets can be throttled by using shaped grains that will vary their surface area over the course of the burn.<ref name="Sutton" />

===Energy efficiency===
{{Further|Rocket#Energy efficiency}}
[[File:Rocket propulsion efficiency.svg|thumb|Rocket vehicle mechanical efficiency as a function of vehicle instantaneous speed divided by effective exhaust speed. These percentages need to be multiplied by internal engine efficiency to get overall efficiency.]]
Rocket engine nozzles are surprisingly efficient [[heat engines]] for generating a high speed jet, as a consequence of the high combustion temperature and high [[compression ratio]]. Rocket nozzles give an excellent approximation to [[adiabatic expansion]] which is a reversible process, and hence they give efficiencies which are very close to that of the [[Carnot cycle]]. Given the temperatures reached, over 60% efficiency can be achieved with chemical rockets.

For a ''vehicle'' employing a rocket engine the energetic efficiency is very good if the vehicle speed approaches or somewhat exceeds the exhaust velocity (relative to launch); but at low speeds the [[Propulsive efficiency|energy efficiency]] goes to 0% at zero speed (as with all [[jet propulsion]]). See [[Rocket#Energy efficiency|Rocket energy efficiency]] for more details.

{{clear}}

===Thrust-to-weight ratio===
{{Main|thrust-to-weight ratio}}
Rockets, of all the jet engines, indeed of essentially all engines, have the highest thrust-to-weight ratio. This is especially true for liquid-fuelled rocket engines.

This high performance is due to the small volume of [[pressure vessel]]s that make up the engine—the pumps, pipes and combustion chambers involved. The lack of inlet duct and the use of dense liquid propellant allows the pressurisation system to be small and lightweight, whereas duct engines have to deal with air which has around three orders of magnitude lower density.

{{Engine thrust to weight table}}

Of the liquid fuels used, density is lowest for [[liquid hydrogen]]. Although hydrogen/oxygen burning has the highest [[specific impulse]] of any in-use chemical rocket, hydrogen's very low density (about one-fourteenth that of water) requires larger and heavier turbopumps and pipework, which decreases the engine's thrust-to-weight ratio (for example the RS-25) compared to those that do not use hydrogen (NK-33).

==Mechanical issues==
Rocket combustion chambers are normally operated at fairly high pressure, typically 10–200{{nbsp}}bar (1–20{{nbsp}}MPa, 150–3,000{{nbsp}}psi). When operated within significant atmospheric pressure, higher combustion chamber pressures give better performance by permitting a larger and more efficient nozzle to be fitted without it being grossly overexpanded.

However, these high pressures cause the outermost part of the chamber to be under very large [[hoop stress]]es – rocket engines are [[pressure vessel]]s.

Worse, due to the high temperatures created in rocket engines the materials used tend to have a significantly lowered working tensile strength.

In addition, significant temperature gradients are set up in the walls of the chamber and nozzle, these cause differential expansion of the inner liner that create [[internal stresses]].

=== Hard starts ===
A '''hard start''' refers to an over-pressure condition during start of a rocket engine at ignition. In the worst cases, this takes the form of an unconfined explosion, resulting in the damage or destruction of the engine.

Rocket fuels, [[hypergolic]] or otherwise, must be introduced into the combustion chamber at the correct rate in order to have a controlled rate of production of hot gas.<ref>{{Cite web |title=Introducing Propellant into a Combustion Chamber |url=https://www.idc-online.com/technical_references/pdfs/mechanical_engineering/Introducing_Propellant_into_a_Combustion_Chamber.pdf |access-date=February 16, 2024 |website=IDC Online}}</ref> A "hard start" indicates that the quantity of combustible propellant that entered the combustion chamber prior to ignition was too large. The result is an excessive spike of pressure, possibly leading to structural failure or explosion.

Avoiding hard starts involves careful timing of the ignition relative to valve timing or varying the mixture ratio so as to limit the maximum pressure that can occur or simply ensuring an adequate ignition source is present well prior to propellant entering the chamber.

Explosions from hard starts usually cannot happen with purely gaseous propellants, since the amount of the gas present in the chamber is limited by the injector area relative to the throat area, and for practical designs, propellant mass escapes too quickly to be an issue.

A famous example of a hard start was the explosion of [[Wernher von Braun]]'s "1W" engine during a demonstration to General [[Walter Dornberger]] on December 21, 1932. Delayed ignition allowed the chamber to fill with alcohol and liquid oxygen, which exploded violently. Shrapnel was embedded in the walls, but nobody was hit.

==Acoustic issues==
The extreme vibration and acoustic environment inside a rocket motor commonly result in peak stresses well above mean values, especially in the presence of [[organ pipe]]-like resonances and gas turbulence.<ref>{{Cite news|url=https://www.technologyreview.com/s/414364/whats-the-deal-with-rocket-vibrations/|title=What's the Deal with Rocket Vibrations?|last=Sauser|first=Brittany|work=MIT Technology Review|access-date=2018-04-27|language=en}}</ref>

===Combustion instabilities===
The combustion may display undesired instabilities, of sudden or periodic nature. The pressure in the injection chamber may increase until the propellant flow through the injector plate decreases; a moment later the pressure drops and the flow increases, injecting more propellant in the combustion chamber which burns a moment later, and again increases the chamber pressure, repeating the cycle. This may lead to high-amplitude pressure oscillations, often in ultrasonic range, which may damage the motor. Oscillations of ±200 psi at 25 kHz were the cause of failures of early versions of the [[LGM-25C Titan II|Titan II]] missile second stage engines. The other failure mode is a [[deflagration to detonation transition]]; the supersonic [[Longitudinal wave|pressure wave]] formed in the combustion chamber may destroy the engine.<ref name="titan2">{{cite book|author=David K. Stumpf|title=Titian II: A History of a Cold War Missile Program|publisher=University of Arkansas Press|date=2000|isbn=1-55728-601-9}}</ref>

Combustion instability was also a problem during [[SM-65 Atlas|Atlas]] development. The Rocketdyne engines used in the Atlas family were found to suffer from this effect in several static firing tests, and three missile launches exploded on the pad due to rough combustion in the booster engines. In most cases, it occurred while attempting to start the engines with a "dry start" method whereby the igniter mechanism would be activated prior to propellant injection. During the process of man-rating Atlas for [[Project Mercury]], solving combustion instability was a high priority, and the final two Mercury flights sported an upgraded propulsion system with baffled injectors and a hypergolic igniter.

The problem affecting Atlas vehicles was mainly the so-called "racetrack" phenomenon, where burning propellant would swirl around in a circle at faster and faster speeds, eventually producing vibration strong enough to rupture the engine, leading to complete destruction of the rocket. It was eventually solved by adding several baffles around the injector face to break up swirling propellant.

More significantly, combustion instability was a problem with the Saturn [[F-1]] engines. Some of the early units tested exploded during static firing, which led to the addition of injector baffles.

In the Soviet space program, combustion instability also proved a problem on some rocket engines, including the RD-107 engine used in the R-7 family and the RD-216 used in the R-14 family, and several failures of these vehicles occurred before the problem was solved. Soviet engineering and manufacturing processes never satisfactorily resolved combustion instability in larger RP-1/LOX engines, so the RD-171 engine used to power the Zenit family still used four smaller thrust chambers fed by a common engine mechanism.

The combustion instabilities can be provoked by remains of cleaning solvents in the engine (e.g. the first attempted launch of a Titan II in 1962), reflected shock wave, initial instability after ignition, explosion near the nozzle that reflects into the combustion chamber, and many more factors. In stable engine designs the oscillations are quickly suppressed; in unstable designs they persist for prolonged periods. Oscillation suppressors are commonly used.

Three different types of combustion instabilities occur:

====Chugging====
A low frequency oscillation in chamber pressure below 200 [[Hertz]]. Usually it is caused by pressure variations in feed lines due to variations in acceleration of the vehicle, when rocket engines are building up thrust, are shut down or are being throttled.<ref name=sutton1975/>{{rp|261}}<ref name="HuzelAndHuang"/>{{rp|146}}

Chugging can cause a worsening feedback loop, as cyclic variation in thrust causes longitudinal vibrations to travel up the rocket, causing the fuel lines to vibrate, which in turn do not deliver propellant smoothly into the engines. This phenomenon is known as "[[pogo oscillation]]s" or "pogo", named after the [[pogo stick]].<ref name="sutton1975" />{{rp|258}}

In the worst case, this may result in damage to the payload or vehicle. Chugging can be minimised by using several methods, such as installing energy-absorbing devices on feed lines.<ref name=sutton1975/>{{rp|259}} Chugging may cause Screeching.<ref name="HuzelAndHuang"/>{{rp|146}}

====Buzzing====
An intermediate frequency oscillation in chamber pressure between 200 and 1000 [[Hertz]]. Usually caused due to insufficient pressure drop across the injectors.<ref name=sutton1975/>{{rp|261}} It generally is mostly annoying, rather than being damaging.

Buzzing is known to have adverse effects on engine performance and reliability, primarily as it causes [[material fatigue]].<ref name="HuzelAndHuang" />{{rp|147}} In extreme cases combustion can end up being forced backwards through the injectors – this can cause explosions with monopropellants.{{citation needed|date=April 2018}} Buzzing may cause Screeching.<ref name="sutton1975" />{{rp|261}}

====Screeching====
A high frequency oscillation in chamber pressure above 1000 [[Hertz]], sometimes called screaming or squealing. The most immediately damaging, and the hardest to control. It is due to acoustics within the combustion chamber that often couples to the chemical combustion processes that are the primary drivers of the energy release, and can lead to unstable resonant "screeching" that commonly leads to catastrophic failure due to thinning of the insulating thermal boundary layer. Acoustic oscillations can be excited by thermal processes, such as the flow of hot air through a pipe or combustion in a chamber. Specifically, standing acoustic waves inside a chamber can be intensified if combustion occurs more intensely in regions where the pressure of the acoustic wave is maximal.<ref name=strutt1896>
{{cite book|author=John W. Strutt|title=The Theory of Sound – Volume 2|edition=2nd|publisher=Macmillan (reprinted by Dover Publications in 1945)|date=1896|page=226}} According to Lord Rayleigh's criterion for thermoacoustic processes, "If heat be given to the air at the moment of greatest condensation, or be taken from it at the moment of greatest rarefaction, the vibration is encouraged. On the other hand, if heat be given at the moment of greatest rarefaction, or abstracted at the moment of greatest condensation, the vibration is discouraged."</ref><ref>Lord Rayleigh (1878) "The explanation of certain acoustical phenomena" (namely, the [[Rijke tube]]) ''Nature'', vol. 18, pages 319–321.</ref><ref>E. C. Fernandes and M. V. Heitor, "Unsteady flames and the Rayleigh criterion" in {{cite book|editor=F. Culick|editor2=M. V. Heitor|editor3=J. H. Whitelaw|title=Unsteady Combustion|edition=1st|publisher=Kluwer Academic Publishers|date=1996|page=4|isbn=0-7923-3888-X|url=https://books.google.com/books?id=Je_hG6UfnogC&pg=PA1}}</ref><ref name=sutton1975>
{{cite book |author=G.P. Sutton |author2=D.M. Ross |name-list-style=amp |title=Rocket Propulsion Elements: An Introduction to the Engineering of Rockets |edition=4th |url=https://archive.org/details/rocketpropulsion0000sutt/page/258/mode/2up |publisher=Wiley Interscience |date=1975 |isbn=0-471-83836-5 }} See Chapter 8, Section 6 and especially Section 7, re combustion instability.</ref>

Such effects are very difficult to predict analytically during the design process, and have usually been addressed by expensive, time-consuming and extensive testing, combined with trial and error remedial correction measures.

Screeching is often dealt with by detailed changes to injectors, changes in the propellant chemistry, vaporising the propellant before injection or use of [[Helmholtz damper]]s within the combustion chambers to change the resonant modes of the chamber.{{citation needed|date=April 2018}}

Testing for the possibility of screeching is sometimes done by exploding small explosive charges outside the combustion chamber with a tube set tangentially to the combustion chamber near the injectors to determine the engine's [[impulse response]] and then evaluating the time response of the chamber pressure- a fast recovery indicates a stable system.

===Exhaust noise===
{{Main|acoustic signature}}
For all but the very smallest sizes, rocket exhaust compared to other engines is generally very noisy. As the [[hypersonic]] exhaust mixes with the ambient air, [[shock wave]]s are formed. The [[Space Shuttle]] generated over 200 [[dB(A)]] of noise around its base. To reduce this, and the risk of payload damage or injury to the crew atop the stack, the [[mobile launcher platform]] was fitted with a [[Sound Suppression System]] that sprayed {{convert|1.1|e6L|USgal}} of water around the base of the rocket in 41 seconds at launch time. Using this system kept sound levels within the payload bay to 142 dB.<ref>{{Cite web
|title=Sound Suppression System
|publisher=NASA
|url=https://www.nasa.gov/mission_pages/shuttle/launch/sound-suppression-system.html
|access-date=2017-02-09
|archive-date=2020-08-10
|archive-url=https://web.archive.org/web/20200810203904/https://www.nasa.gov/mission_pages/shuttle/launch/sound-suppression-system.html
|url-status=dead
}}</ref>

The [[sound intensity]] from the shock waves generated depends on the size of the rocket and on the exhaust velocity. Such shock waves seem to account for the characteristic crackling and popping sounds produced by large rocket engines when heard live. These noise peaks typically overload microphones and audio electronics, and so are generally weakened or entirely absent in recorded or broadcast audio reproductions. For large rockets at close range, the acoustic effects could actually kill.<ref name="CR566">R.C. Potter and M.J. Crocker (1966). [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660030602_1966030602.pdf NASA CR-566, Acoustic Prediction Methods For Rocket Engines, Including The Effects Of Clustered Engines And Deflected Flow] From website of the National Aeronautics and Space Administration Langley (NASA Langley)</ref>

More worryingly for space agencies, such sound levels can also damage the launch structure, or worse, be reflected back at the comparatively delicate rocket above. This is why so much water is typically used at launches. The water spray changes the acoustic qualities of the air and reduces or deflects the sound energy away from the rocket.

Generally speaking, noise is most intense when a rocket is close to the ground, since the noise from the engines radiates up away from the jet, as well as reflecting off the ground. Also, when the vehicle is moving slowly, little of the chemical energy input to the engine can go into increasing the kinetic energy of the rocket (since useful power ''P'' transmitted to the vehicle is <math>P = F*V</math> for thrust ''F'' and speed ''V''). Then the largest portion of the energy is dissipated in the exhaust's interaction with the ambient air, producing noise. This noise can be reduced somewhat by flame trenches with roofs, by water injection around the jet and by deflecting the jet at an angle.

== Rocket engine development ==
=== United States ===
The development of the US rocket engine industry has been shaped by a complex web of relationships between government agencies, private companies, research institutions, and other stakeholders.

Since the establishment of the first [[liquid-propellant rocket]] engine company ([[Reaction Motors|Reaction Motors, Inc.]]) in 1941 and the first government laboratory ([[Guggenheim Aeronautical Laboratory|GALCIT]]) devoted to the subject, the US liquid-propellant rocket engine (LPRE) industry has undergone significant changes. At least 14 US companies have been involved in the design, development, manufacture, testing, and flight support operations of various types of rocket engines from 1940 to 2000. In contrast to other countries like Russia, China, or India, where only government or pseudogovernment organisations engage in this business, the US government relies heavily on private industry. These commercial companies are essential to the continued viability of the United States and its form of governance, as they compete with one another to provide cutting-edge rocket engines that meet the needs of the government, the military, and the private sector. In the United States the company that develops the LPRE usually is awarded the production contract.

Generally, the need or demand for a new rocket engine comes from government agencies such as [[NASA]] or the [[United States Department of Defense|Department of Defense]]. Once the need is identified, government agencies may issue [[Request for proposal|requests for proposals]] (RFPs) to solicit proposals from private companies and research institutions. Private companies and research institutions, in turn, may invest in research and development (R&D) activities to develop new rocket engine technologies that meet the needs and specifications outlined in the RFPs.

Alongside private companies, universities, independent research institutes and government laboratories also play a critical role in the research and development of rocket engines.

Universities provide graduate and undergraduate education to train qualified technical personnel, and their research programs often contribute to the advancement of rocket engine technologies. More than 25 universities in the US have taught or are currently teaching courses related to Liquid Propellant Rocket Engines (LPREs), and their graduate and undergraduate education programs are considered one of their most important contributions. Universities such as Princeton University, Cornell University, Purdue University, Pennsylvania State University, University of Alabama, the Navy's Post-Graduate School, or the California Institute of Technology have conducted excellent R&D work on topics related to the rocket engine industry.<ref name=":0" /> One of the earliest examples of the contribution of universities to the rocket engine industry is the work of the GALCIT in 1941. They demonstrated the first jet-assisted takeoff (JATO) rockets to the Army, leading to the establishment of the Jet Propulsion Laboratory.

However the transfer of knowledge from research professors and their projects to the rocket engine industry has been a mixed experience. While some notable professors and relevant research projects have positively influenced industry practices and understanding of LPREs, the connection between university research and commercial companies has been inconsistent and weak.<ref name=":0" /> Universities were not always aware of the industry's specific needs, and engineers and designers in the industry had limited knowledge of university research. As a result, many university research programs remained relatively unknown to industry decision-makers. Furthermore, in the last few decades, certain university research projects, while interesting to professors, were not useful to the industry due to a lack of communication or relevance to industry needs.<ref name=":0" />

Government laboratories, including the Rocket Propulsion Laboratory (now part of Air Force Research Laboratory), Arnold Engineering Test Center, NASA Marshall Space Flight Center, Jet Propulsion Laboratory, Stennis Space Center, White Sands Proving Grounds, and NASA John H. Glenn Research Center, have played crucial roles in the development of liquid rocket propulsion engines (LPREs).<ref name=":0" /> They have conducted unbiased testing, guided work at US and some non-US contractors, performed research and development, and provided essential testing facilities including hover test facilities and simulated altitude test facilities and resources. Initially, private companies or foundations financed smaller test facilities, but since the 1950s, the U.S. government has funded larger test facilities at government laboratories. This approach reduced costs for the government by not building similar facilities at contractors' plants but increased complexity and expenses for contractors. Nonetheless, government laboratories have solidified their significance and contributed to LPRE advancements.

LPRE programs have been subject to several cancellations in the United States, even after spending millions of dollars on their development. For example, the M-l LOX/LH2 LPRE, Titan I, and the RS-2200 aerospike, as well as several JATO units and large uncooled thrust chambers were cancelled. The cancellations of these programs were not related to the specific LPRE's performance or any issues with it. Instead, they were due to the cancellation of the vehicle programs the engine was intended for or budget cuts imposed by the government.

=== USSR ===
Russia and the former Soviet Union was and still is the world's foremost nation in developing and building rocket engines. From 1950 to 1998, their organisations developed, built, and put into operation a larger number and a larger variety of liquid propellant rocket engine (LPRE) designs than any other country. Approximately 500 different LPREs have been developed before 2003. For comparison the United States has developed slightly more than 300 (before 2003). The Soviets also had the most rocket-propelled flight vehicles. They had more liquid propellant [[ballistic missile]]s and more [[Launch vehicle|space launch vehicles]] derived or converted from these decommissioned ballistic missiles than any other nation. As of the end of 1998, the Russians (or earlier the Soviet Union) had successfully launched 2573 [[satellite]]s with LPREs or almost 65% of the world total of 3973. All of these vehicle flights were made possible by the timely development of suitable high-performance reliable LPREs.<ref name=":0">{{Cite book |last=Sutton |first=George |title=History of Liquid Propellant Rocket Engines |publisher=AIAA |year=2006 |isbn=978-1-56347-649-5}}</ref>

==== Institutions and actors ====
Unlike many other countries where the development and production of rocket engines were consolidated within a single organisation, the Soviet Union took a different approach, they established numerous specialised [[OKB|design bureaus]] (DB) which would compete for development contracts. These design bureaus, or "konstruktorskoye buro" (KB) in Russian were state run organisations which were primarily responsible for carrying out [[Research and development|research, development]] and [[Prototype|prototyping]] of advanced technologies usually related to [[Military technology|military hardware]], such as [[turbojet]] [[engine]]s, aircraft components, [[missile]]s, or [[Launch vehicle|space launch vehicles]].

[[OKB|Design Bureaus]] which specialised in rocket engines often possessed the necessary personnel, facilities, and equipment to conduct l[[Launch vehicle system tests|aboratory tests, flow tests, and ground testing of experimental rocket engines]]. Some even had specialised facilities for testing very large engines, conducting [[Launch vehicle system tests|static firings]] of engines installed in vehicle stages, or simulating altitude conditions during engine tests. In certain cases, engine testing, certification and [[quality control]] were outsourced to other organisations and locations with more suitable test facilities. Many DBs also had housing complexes, gymnasiums, and medical facilities intended to support the needs of their employees and their families.

The Soviet Union's LPRE development effort saw significant growth during the 1960s and reached its peak in the 1970s. This era coincided with the [[Cold War]] between the Soviet Union and the United States, characterised by intense competition in spaceflight achievements. Between 14 and 17 Design Bureaus and research institutes were actively involved in developing LPREs during this period. These organisations received relatively steady support and funding due to high military and [[Soviet space program|spaceflight priorities]], which facilitated the continuous development of new engine concepts and manufacturing methods.

Once a mission with a new vehicle (missile or spacecraft) was established it was passed on to a design bureau whose role was to oversee the development of the entire rocket. If none of the previously developed rocket engines met the needs of the mission, a new rocket engine with specific requirements would be contracted to another DB specialised in LPRE development (oftentimes each DB had expertise in specific types of LPREs with different applications, propellants, or engine sizes). This meant that the development or design study of a rocket engine was always aimed at a specific application which entailed set requirements.

When it comes to which DBs were awarded contracts for the development of new rocket engines either a single design bureau would be chosen or several design bureaus would be given the same contract which sometimes led to fierce competition between DBs.

When only one DB was picked for the development, it was often the result of the relationship between a vehicle or system's chief designer and the chief designer of a rocket engine specialised DB. If the vehicle's chief designer was happy with previous work done by a certain design bureau it was not unusual to see continued reliance on that LPRE bureau for that class of engines. For example, all but one of the LPREs for submarine-launched missiles were developed by the same design bureau for the same vehicle development prime contractor.

However, when two parallel engine development programs were supported in order to select the superior one for a specific application, several qualified rocket engine models were never used. This luxury of choice was not commonly available in other nations. However, the use of design bureaus also led to certain issues, including program cancellations and duplication. Some major programs were cancelled, resulting in the disposal or storage of previously developed engines.

One notable example of duplication and cancellation was the development of engines for the R-9A ballistic missile. Two sets of engines were supported, but ultimately only one set was selected, leaving several perfectly functional engines unused. Similarly, for the ambitious heavy N-l space launch vehicle intended for lunar and planetary missions, the Soviet Union developed and put into production at least two engines for each of the six stages. Additionally, they developed alternate engines for a more advanced N-l vehicle. However, the program faced multiple flight failures, and with the United States' successful [[Moon landing]], the program was ultimately cancelled, leaving the Soviet Union with a surplus of newly qualified engines without a clear purpose.

These examples demonstrate the complex dynamics and challenges faced by the Soviet Union in managing the development and production of rocket engines through Design Bureaus.

==== Accidents ====
The development of rocket engines in the Soviet Union was marked by significant achievements, but it also carried ethical considerations due to numerous accidents and fatalities. From a [[Science and technology studies|Science and Technology Studies]] point of view, the ethical implications of these incidents shed light on the complex relationship between technology, human factors, and the prioritisation of scientific advancement over safety.

The Soviet Union encountered a series of tragic accidents and mishaps in the development and operation of rocket engines. Notably, the USSR holds the unfortunate distinction of having experienced more injuries and deaths resulting from liquid propellant rocket engine (LPRE) accidents than any other country. These incidents brought into question the ethical considerations surrounding the development, testing, and operational use of rocket engines.

One of the most notable disasters occurred in 1960 when the [[R-16 (missile)|R-16]] ballistic missile suffered a catastrophic accident on the launchpad at the [[Töretam|Tyuratam]] launch facility. This incident resulted in the deaths of 124 engineers and military personnel, including Marshal M.I. Nedelin, a former deputy [[Minister of Defence (Soviet Union)|minister of defence]]. The explosion occurred after the second-stage rocket engine suddenly ignited, causing the fully loaded missile to disintegrate. The explosion resulted from the ignition and explosion of the mixed [[hypergolic propellant]]s, consisting of [[nitric acid]] with additives and [[Unsymmetrical dimethylhydrazine|UDMH]] (unsymmetrical dimethylhydrazine).

While the immediate cause of the 1960 accident was attributed to a lack of protective circuits in the missile control unit, the ethical considerations surrounding LPRE accidents in the USSR extend beyond specific technical failures. The secrecy surrounding these accidents, which remained undisclosed for approximately three decades, raises concerns about transparency, accountability, and the protection of human life.

The decision to keep fatal LPRE accidents hidden from the public eye reflects a broader ethical dilemma. The Soviet government, driven by the pursuit of scientific and technological superiority during the Cold War, sought to maintain an image of invincibility and conceal the failures that accompanied their advancements. This prioritisation of national prestige over the well-being and safety of workers raises questions about the ethical responsibility of the state and the organisations involved.

==Testing==

Rocket engines are usually statically tested at a [[rocket engine test facility|test facility]] before being put into production. For high altitude engines, either a shorter nozzle must be used, or the rocket must be tested in a large vacuum chamber.

==Safety==
[[Rocket]] vehicles have a reputation for unreliability and danger; especially catastrophic failures. Contrary to this reputation, carefully designed rockets can be made arbitrarily reliable.{{Citation needed|date=January 2017}} In military use, rockets are not unreliable. However, one of the main non-military uses of rockets is for orbital launch. In this application, the premium has typically been placed on minimum weight, and it is difficult to achieve high reliability and low weight simultaneously. In addition, if the number of flights launched is low, there is a very high chance of a design, operations or manufacturing error causing destruction of the vehicle.{{Citation needed|date=January 2017}}

===Saturn family (1961–1975)===
The [[Rocketdyne H-1]] engine, used in a cluster of eight in the first stage of the [[Saturn I]] and [[Saturn IB]] [[launch vehicle]]s, had no catastrophic failures in 152 engine-flights. The [[Pratt and Whitney]] [[RL10]] engine, used in a cluster of six in the Saturn I second stage, had no catastrophic failures in 36 engine-flights.{{refn|group=notes|name=RL10|The RL10 ''has'', however, experienced occasional failures (some of them catastrophic) in its other use cases, as the engine for the much-flown [[Centaur (rocket stage)|Centaur]] and [[Delta Cryogenic Second Stage|DCSS]] upper stages.}} The [[Rocketdyne F-1]] engine, used in a cluster of five in the first stage of the [[Saturn V]], had no failures in 65 engine-flights. The [[Rocketdyne J-2]] engine, used in a cluster of five in the Saturn V second stage, and singly in the Saturn IB second stage and Saturn V third stage, had no catastrophic failures in 86 engine-flights.{{refn|group=notes|name=J2fail|The J-2 had three premature in-flight shutdowns (two second-stage engine failures on [[Apollo 6]] and one on [[Apollo 13]]), and one failure to restart in orbit (the third-stage engine of Apollo 6). But these failures did not result in vehicle loss or mission abort (although the failure of Apollo 6's third-stage engine to restart ''would'' have forced a mission abort had it occurred on a crewed lunar mission).}}

===Space Shuttle (1981–2011)===
The [[Space Shuttle Solid Rocket Booster]], used in pairs, caused [[Space Shuttle Challenger disaster|one notable catastrophic failure]] in 270 engine-flights.

The [[RS-25]], used in a cluster of three, flew in 46 refurbished engine units. These made a total of 405 engine-flights with no catastrophic in-flight failures. A single in-flight [[RS-25]] engine failure occurred during {{OV|99}}'s [[STS-51-F]] mission.<ref name="P&WFS">{{cite web|url=http://www.pw.utc.com/products/pwr/assets/pwr_SSME.pdf |title=Space Shuttle Main Engine |publisher=Pratt & Whitney Rocketdyne |access-date=November 23, 2011 |year=2005 |url-status=dead |archive-url=https://web.archive.org/web/20120208191620/http://www.pw.utc.com/products/pwr/assets/pwr_SSME.pdf |archive-date=February 8, 2012 }}</ref> This failure had no effect on mission objectives or duration.<ref name="Hale">{{cite web|author=[[Wayne Hale]] & various|title=An SSME-related request|publisher=NASASpaceflight.com|access-date=January 17, 2012|date=January 17, 2012|url=http://forum.nasaspaceflight.com/index.php?topic=27783}}</ref>

==Cooling==
For efficiency reasons, higher temperatures are desirable, but materials lose their strength if the temperature becomes too high. Rockets run with combustion temperatures that can reach {{cvt|6,000|F|C K|-2}}.<ref name="HuzelAndHuang" />{{rp|98}}

Most other jet engines have gas turbines in the hot exhaust. Due to their larger surface area, they are harder to cool and hence there is a need to run the combustion processes at much lower temperatures, losing efficiency. In addition, [[wiktionary:duct engine|duct engines]] use air as an oxidant, which contains 78% largely unreactive nitrogen, which dilutes the reaction and lowers the temperatures.<ref name="Sutton" /> Rockets have none of these inherent combustion temperature limiters.

The temperatures reached by combustion in rocket engines often substantially exceed the melting points of the nozzle and combustion chamber materials (about 1,200 K for [[copper]]). Most construction materials will also combust if exposed to high temperature oxidiser, which leads to a number of design challenges. The nozzle and combustion chamber walls must not be allowed to combust, melt, or vaporize (sometimes facetiously termed an "engine-rich exhaust").

Rockets that use common construction materials such as aluminium, steel, nickel or copper alloys must employ cooling systems to limit the temperatures that engine structures experience. [[Regenerative cooling (rocket)|Regenerative cooling]], where the propellant is passed through tubes around the combustion chamber or nozzle, and other techniques, such as film cooling, are employed to give longer nozzle and chamber life. These techniques ensure that a gaseous thermal [[boundary layer]] touching the material is kept below the temperature which would cause the material to catastrophically fail.

Material exceptions that can sustain rocket combustion temperatures to a certain degree are [[Reinforced carbon–carbon|carbon–carbon materials]] and [[rhenium]], although both are subject to oxidation under certain conditions. Other [[refractory]] alloys, such as alumina, [[molybdenum]], [[tantalum]] or [[tungsten]] have been tried, but were given up on due to various issues.<ref name="RocketProp8">{{cite book |author=George P. Sutton |url=https://archive.org/details/Rocket_Propulsion_Elements_8th_Edition_by_Oscar_Biblarz_George_P._Sutton/page/308/mode/2up |title=Rocket Propulsion Elements |author2=Oscar Biblarz |date=2010 |publisher=Wiley Interscience |isbn=9780470080245 |edition=8th |page=308 |name-list-style=amp}}</ref>

Materials technology, combined with the engine design, is a limiting factor in chemical rockets.

In rockets, the [[heat flux]]es that can pass through the wall are among the highest in engineering; fluxes are generally in the range of 0.8–80 MW/m{{sup|2}} (0.5-50 [[BTU]]/in{{sup|2}}-sec).<ref name="HuzelAndHuang" />{{rp|98}} The strongest heat fluxes are found at the throat, which often sees twice that found in the associated chamber and nozzle. This is due to the combination of high speeds (which gives a very thin boundary layer), and although lower than the chamber, the high temperatures seen there. (See {{section link||Nozzle}} above for temperatures in nozzle).

In rockets the coolant methods include:<ref name="HuzelAndHuang" />{{rp|98–99}}

#[[ablation|Ablative]]: The combustion chamber inside walls are lined with a material that traps heat and carries it away with the exhaust as it vaporizes.
#[[Radiative cooling]]: The engine is made of one or several [[refractory]] materials, which take heat flux until its outer thrust chamber wall glows red- or white-hot, radiating the heat away.
#Dump cooling: A cryogenic propellant, usually [[hydrogen]], is passed around the nozzle and dumped. This cooling method has various issues, such as wasting propellant. It is only used rarely.
#[[regenerative cooling (rocket)|Regenerative cooling]]: The fuel (and possibly, the oxidiser) of a [[liquid rocket engine]] is routed around the nozzle before being injected into the combustion chamber or preburner. This is the most widely applied method of rocket engine cooling.
#Film cooling: The engine is designed with rows of multiple orifices lining the inside wall through which additional propellant is injected, cooling the chamber wall as it evaporates. This method is often used in cases where the heat fluxes are especially high, likely in combination with [[regenerative cooling (rocket)|regenerative cooling]]. A more efficient subtype of film cooling is [[transpiration cooling]], in which propellant passes through a [[porous]] inner combustion chamber wall and transpirates. So far, this method has not seen usage due to various issues with this concept.

Rocket engines may also use several cooling methods. Examples:

* Regeneratively and film cooled combustion chamber and nozzle: [[V-2 rocket|V-2]] Rocket Engine<ref>{{cite web |title=Raketenmotor der A4 (V2)-Rakete |url=https://www.deutsches-museum.de/flugwerft-schleissheim/ausstellung/flugantriebe-und-raketen/raketenmotor-a-4 |access-date=19 September 2022 |language=de |quote=An additional coolant line takes alcohol to fine holes in the inner chamber wall. The alcohol flows alongside the wall, creating a thin, evaporating film for additional cooling.}}</ref>
* Regeneratively cooled combustion chamber with a film cooled nozzle extension: [[Rocketdyne F-1|Rocketdyne F-1 Engine]]<ref>{{cite web |author=McCutcheon, Kimble D. |date=3 August 2022 |title=U.S. Manned Rocket Propulsion Evolution Part 8.12: Rocketdyne F-1 Engine Description |url=https://www.enginehistory.org/Rockets/RPE08.11/RPE08.12.shtml |access-date=19 September 2022}}</ref>
* Regeneratively cooled combustion chamber with an ablatively cooled nozzle extension: The [[LR-91]] rocket engine<ref>{{cite web |author=McCutcheon, Kimble D. |date=3 August 2022 |title=U.S. Manned Rocket Propulsion Evolution Part 6: The Titan Missile |url=https://www.enginehistory.org/Rockets/RPE06/RPE06.shtml |access-date=19 September 2022}}</ref>
* Ablatively and film cooled combustion chamber with a radiatively cooled nozzle extension: [[Lunar module descent engine]] (LMDE), [[Apollo command and service module#Service propulsion system|Service propulsion system engine]] (SPS)<ref>{{cite book |last=Bartlett |first=W. |url=https://ntrs.nasa.gov/api/citations/19700026405/downloads/19700026405.pdf |title=Apollo spacecraft liquid primary propulsion systems |last2=Kirkland |first2=Z. D. |last3=Polifka |first3=R. W. |last4=Smithson |first4=J. C. |last5=Spencer |first5=G. L. |date=7 February 1966 |publisher=NASA, Lyndon B. Johnson Space Center |location=Houston, TX |pages=8 |archive-url=https://web.archive.org/web/20220823092501/https://ntrs.nasa.gov/api/citations/19700026405/downloads/19700026405.pdf |archive-date=23 August 2022 |access-date=10 September 2022 |url-status=bot: unknown }}</ref>
* Radiatively and film cooled combustion chamber with a radiatively cooled nozzle extension: [[Deep Space Industries|Deep space]] storable propellant thrusters<ref name="RocketProp8" />

In all cases, another effect that aids in cooling the rocket engine chamber wall is a thin layer of combustion gases (a [[boundary layer]]) that is notably cooler than the combustion temperature. Disruption of the boundary layer may occur during cooling failures or combustion instabilities, and wall failure typically occurs soon after.

With regenerative cooling a second boundary layer is found in the coolant channels around the chamber. This boundary layer thickness needs to be as small as possible, since the boundary layer acts as an insulator between the wall and the coolant. This may be achieved by making the coolant [[velocity]] in the channels as high as possible.<ref name="HuzelAndHuang" />{{rp|105–106}}

Liquid-fuelled engines are often run [[Air-fuel ratio|fuel-rich]], which lowers combustion temperatures. This reduces heat loads on the engine and allows lower cost materials and a simplified cooling system. This can also ''increase'' performance by lowering the average molecular weight of the exhaust and increasing the efficiency with which combustion heat is converted to kinetic exhaust energy.

==Chemistry==
[[Rocket propellant]]s require a high energy per unit mass ([[specific energy]]), which must be balanced against the tendency of highly energetic propellants to spontaneously explode. Assuming that the chemical potential energy of the propellants can be safely stored, the combustion process results in a great deal of heat being released. A significant fraction of this heat is transferred to kinetic energy in the engine nozzle, propelling the rocket forward in combination with the mass of combustion products released.

Ideally all the reaction energy appears as kinetic energy of the exhaust gases, as exhaust velocity is the single most important performance parameter of an engine. However, real exhaust species are [[molecule]]s, which typically have translation, vibrational, and [[rotational modes]] with which to dissipate energy. Of these, only translation can do useful work to the vehicle, and while energy does transfer between modes this process occurs on a timescale far in excess of the time required for the exhaust to leave the nozzle.

The more [[chemical bond]]s an exhaust molecule has, the more rotational and vibrational modes it will have. Consequently, it is generally desirable for the exhaust species to be as simple as possible, with a diatomic molecule composed of light, abundant atoms such as H2 being ideal in practical terms. However, in the case of a chemical rocket, hydrogen is a reactant and [[reducing agent]], not a product. An [[oxidizing agent]], most typically oxygen or an oxygen-rich species, must be introduced into the combustion process, adding mass and chemical bonds to the exhaust species.

An additional advantage of light molecules is that they may be accelerated to high velocity at temperatures that can be contained by currently available materials - the high gas temperatures in rocket engines pose serious problems for the engineering of survivable motors.

Liquid [[hydrogen]] (LH2) and [[oxygen]] (LOX, or LO2), are the most effective propellants in terms of exhaust velocity that have been widely used to date, though a few exotic combinations involving boron or liquid ozone are potentially somewhat better in theory if various practical problems could be solved.<ref>[http://yarchive.net/space/rocket/fuels/fuel_ratio.html Newsgroup correspondence], 1998–99</ref>

When computing the specific reaction energy of a given propellant combination, the entire mass of the propellants (both fuel and oxidiser) must be included. The exception is in the case of air-breathing engines, which use atmospheric oxygen and consequently have to carry less mass for a given energy output. Fuels for car or [[turbojet engine]]s have a much better effective energy output per unit mass of propellant that must be carried, but are similar per unit mass of fuel.

Computer programs that predict the performance of propellants in rocket engines are available.<ref>[http://rocketworkbench.sourceforge.net/equil.phtml Complex chemical equilibrium and rocket performance calculations], Cpropep-Web</ref><ref>[http://propulsion-analysis.com/ Tool for Rocket Propulsion Analysis], RPA</ref><ref>[https://web.archive.org/web/20000901045039/http://www.grc.nasa.gov/WWW/CEAWeb/ NASA Computer program Chemical Equilibrium with Applications], CEA</ref>

==Ignition==
{{Further|Combustion}}
With liquid and hybrid rockets, immediate ignition of the propellants as they first enter the combustion chamber is essential.

With liquid propellants (but not gaseous), failure to ignite within milliseconds usually causes too much liquid propellant to be inside the chamber, and if/when ignition occurs the amount of hot gas created can exceed the maximum design pressure of the chamber, causing a catastrophic failure of the pressure vessel. This is sometimes called a ''[[hard start]]'' or a ''rapid unscheduled disassembly'' (RUD).<ref name=aw20121126>
{{cite news |last=Svitak|first=Amy |title=Falcon 9 RUD? |url=http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385Post:c973f72f-55d3-4374-b722-df31a8d333e6 |archive-url=https://web.archive.org/web/20140321053215/http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog:04ce340e-4b63-4d23-9695-d49ab661f385Post:c973f72f-55d3-4374-b722-df31a8d333e6 |url-status=dead |archive-date=2014-03-21 |access-date=2014-03-21 |newspaper=Aviation Week |date=2012-11-26 }}</ref>

Ignition can be achieved by a number of different methods; a pyrotechnic charge can be used, a plasma torch can be used,{{citation needed|date=October 2016}} or electric spark ignition<ref name=nsf20161003>
{{cite news |last=Belluscio|first=Alejandro G. |title=ITS Propulsion – The evolution of the SpaceX Raptor engine |work=[[NASASpaceFlight.com]] |date=2016-10-03 |url=https://www.nasaspaceflight.com/2016/10/its-propulsion-evolution-raptor-engine/ |access-date=2016-10-03 }}</ref> may be employed. Some fuel/oxidiser combinations ignite on contact ([[hypergolic]]), and non-hypergolic fuels can be "chemically ignited" by priming the fuel lines with hypergolic propellants (popular in Russian engines).

Gaseous propellants generally will not cause [[hard start]]s, with rockets the total injector area is less than the throat thus the chamber pressure tends to ambient prior to ignition and high pressures cannot form even if the entire chamber is full of flammable gas at ignition.

Solid propellants are usually ignited with one-shot pyrotechnic devices and combustion usually proceeds through total consumption of the propellants.<ref name=Sutton/>

Once ignited, rocket chambers are self-sustaining and igniters are not needed and combustion usually proceeds through total consumption of the propellants. Indeed, chambers often spontaneously reignite if they are restarted after being shut down for a few seconds. Unless designed for re-ignition, when cooled, many rockets cannot be restarted without at least minor maintenance, such as replacement of the pyrotechnic igniter or even refueling of the propellants.<ref name=Sutton/>

==Jet physics==
[[File:Armadillo Aerospace Pixel Hover.jpg|thumb|right|[[Quad (rocket)|Armadillo Aerospace's quad vehicle]] showing visible banding (shock diamonds) in the exhaust jet]]
Rocket jets vary depending on the rocket engine, design altitude, altitude, thrust and other factors.

Carbon-rich exhausts from kerosene-based fuels such as [[RP-1]] are often orange in colour due to the [[black-body radiation]] of the unburnt particles, in addition to the blue [[Swan band]]s. [[high test peroxide|Peroxide]] oxidiser-based rockets and hydrogen rocket jets contain largely [[steam]] and are nearly invisible to the naked eye but shine brightly in the [[ultraviolet]] and [[infrared]] ranges. Jets from [[solid-propellant rocket]]s can be highly visible, as the propellant frequently contains metals such as elemental aluminium which burns with an orange-white flame and adds energy to the combustion process. Rocket engines which burn liquid hydrogen and oxygen will exhibit a nearly transparent exhaust, due to it being mostly [[superheated steam]] (water vapour), plus some unburned hydrogen.

The nozzle is usually over-expanded at sea level, and the exhaust can exhibit visible [[shock diamonds]] through a [[schlieren#Schlieren flow visualization|schlieren effect]] caused by the [[incandescence]] of the exhaust gas.

The shape of the jet varies for a fixed-area nozzle as the expansion ratio varies with altitude: at high altitude all rockets are grossly under-expanded, and a quite small percentage of exhaust gases actually end up expanding forwards.

==Types of rocket engines==

===Physically powered===
{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Water rocket]]
| Partially filled pressurised carbonated drinks container with tail and nose weighting
| Very simple to build
| Altitude typically limited to a few hundred feet or so (world record is 830 meters, or 2,723 feet)
|-
! [[Cold gas thruster]]
| A non-combusting form, used for [[vernier thruster]]s
| Non-contaminating exhaust
| Extremely low performance
|}

===Chemically powered===
{{See also|Liquid rocket propellant}}

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Solid-propellant rocket]]
| Ignitable, self-sustaining solid fuel/oxidiser mixture ("grain") with central hole and nozzle
| Simple, often no [[moving parts]], reasonably good mass fraction, reasonable [[Specific Impulse|''I''sp]]. A thrust schedule can be designed into the grain.
| Throttling, burn termination, and reignition require special designs. Handling issues from ignitable mixture. Lower performance than liquid rockets. If grain cracks it can block nozzle with disastrous results. Grain cracks burn and widen during burn. Refueling harder than simply filling tanks. Cannot be turned off after ignition; will fire until all solid fuel is depleted.
|-
! [[Hybrid-propellant rocket]]
| Separate oxidiser/fuel; typically the oxidiser is liquid and kept in a tank and the fuel is solid.
| Quite simple, solid fuel is essentially inert without oxidiser, safer; cracks do not escalate, throttleable and easy to switch off.
| Some oxidisers are monopropellants, can explode in own right; mechanical failure of solid propellant can block nozzle (very rare with rubberised propellant), central hole widens over burn and negatively affects mixture ratio.
|-
! [[Monopropellant rocket]]
| Propellant (such as hydrazine, hydrogen peroxide or nitrous oxide) flows over a catalyst and exothermically decomposes; hot gases are emitted through nozzle.
| Simple in concept, throttleable, low temperatures in combustion chamber
| Catalysts can be easily contaminated, monopropellants can detonate if contaminated or provoked, [[Specific Impulse|''I''sp]] is perhaps 1/3 of best liquids
|-
! [[Liquid bipropellant rocket engine|Bipropellant rocket]]
| Two fluid (typically liquid) propellants are introduced through injectors into combustion chamber and burnt.
| Up to ~99% efficient combustion with excellent mixture control, throttleable, can be used with turbopumps which permits incredibly lightweight tanks, can be safe with extreme care
| Pumps needed for high performance are expensive to design, huge thermal fluxes across combustion chamber wall can impact reuse, failure modes include major explosions, a lot of plumbing is needed.
|-
! [[Methane-oxygen gaseous thruster|Gas-gas rocket]]
| A bipropellant thruster using gas propellant for both the oxidiser and fuel
| Higher-performance than cold gas thrusters
| Lower performance than liquid-based engines
|-
! [[Dual mode propulsion rocket]]
| Rocket takes off as a bipropellant rocket, then turns to using just one propellant as a monopropellant.
| Simplicity and ease of control
| Lower performance than bipropellants
|-
! [[Tripropellant rocket]]
| Three different propellants (usually hydrogen, hydrocarbon, and liquid oxygen) are introduced into a combustion chamber in variable mixture ratios, or multiple engines are used with fixed propellant mixture ratios and throttled or shut down
| Reduces take-off weight, since hydrogen is lighter; combines good thrust to weight with high average [[specific impulse|''I''sp]], improves payload for launching from Earth by a sizeable percentage
| Similar issues to bipropellant, but with more plumbing, more research and development
|-
! [[Air-augmented rocket]]
| Essentially a ramjet where intake air is compressed and burnt with the exhaust from a rocket
| Mach 0 to Mach 4.5+ (can also run exoatmospheric), good efficiency at Mach 2 to 4
| Similar efficiency to rockets at low speed or exoatmospheric, inlet difficulties, a relatively undeveloped and unexplored type, cooling difficulties, very noisy, thrust/weight ratio is similar to ramjets.
|-
! [[Turborocket]]
| A combined cycle turbojet/rocket where an additional oxidiser such as oxygen is added to the airstream to increase maximum altitude
| Very close to existing designs, operates in very high altitude, wide range of altitude and airspeed
| Atmospheric airspeed limited to same range as turbojet engine, carrying oxidiser like [[LOX]] can be dangerous. Much heavier than simple rockets.
|-
! [[Precooled jet engine]] / [[liquid air cycle engine|LACE]] (combined cycle with rocket)
| Intake air is chilled to very low temperatures at inlet before passing through a ramjet or turbojet engine. Can be combined with a rocket engine for orbital insertion.
| Easily tested on ground. High thrust/weight ratios are possible (~14) together with good fuel efficiency over a wide range of airspeeds, mach 0–5.5+; this combination of efficiencies may permit launching to orbit, single stage, or very rapid intercontinental travel.
| Exists only at the lab prototyping stage. Examples include [[RB545]], [[Reaction Engines SABRE|SABRE]], [[ATREX]]
|}

===Electrically powered===
{{Main|Electrically powered spacecraft propulsion}}
{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Resistojet rocket]] (electric heating)
| Energy is imparted to a usually inert fluid serving as reaction mass via [[Joule heating]] of a heating element. May also be used to impart extra energy to a monopropellant.
| Efficient where electrical power is at a lower premium than mass. Higher [[specific impulse|''I''sp]] than monopropellant alone, about 40% higher.
| Requires a lot of power, hence typically yields low thrust.
|-
! [[Arcjet rocket]] (chemical burning aided by electrical discharge)
| Identical to resistojet except the heating element is replaced with an electrical arc, eliminating the physical requirements of the heating element.
| 1,600 seconds [[specific impulse|''I''sp]]
| Very low thrust and high power, performance is similar to [[ion drive]].
|-
![[Variable specific impulse magnetoplasma rocket]]
| Microwave heated plasma with magnetic throat/nozzle
| Variable ''I''sp from 1,000 seconds to 10,000 seconds
| Similar thrust/weight ratio with ion drives (worse), thermal issues, as with ion drives very high power requirements for significant thrust, really needs advanced nuclear reactors, never flown, requires low temperatures for superconductors to work
|-
! [[Pulsed plasma thruster]] (electric arc heating; emits plasma)
| Plasma is used to erode a solid propellant
| High ''I''sp, can be pulsed on and off for attitude control
| Low energetic efficiency
|-
! [[Ion thruster|Ion propulsion system]]
| High voltages at ground and plus sides
| Powered by battery
| Low thrust, needs high voltage
|}

===Thermal===

====Preheated====
{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Hot water rocket]]
| Hot water is stored in a tank at high temperature / pressure and turns to steam in nozzle
| Simple, fairly safe
| Low overall performance due to heavy tank; [[specific impulse|''I''sp]] under 200 seconds
|}

====Solar thermal====

The [[solar thermal rocket]] would make use of solar power to directly heat [[reaction mass]], and therefore does not require an electrical generator as most other forms of solar-powered propulsion do. A solar thermal rocket only has to carry the means of capturing solar energy, such as [[Concentrating solar power|concentrator]]s and [[mirror]]s. The heated propellant is fed through a conventional rocket nozzle to produce thrust. The engine thrust is directly related to the surface area of the solar collector and to the local intensity of the solar radiation and inversely proportional to the ''I''sp.

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Solar thermal rocket]]
| Propellant is heated by solar collector
| Simple design. Using hydrogen propellant, 900 seconds of [[specific impulse|''I''sp]] is comparable to nuclear thermal rocket, without the problems and complexity of controlling a fission reaction.{{citation needed|date=January 2011}} Ability to [[Solar thermal rocket#Proposed solar-thermal space systems|productively use]] waste gaseous [[hydrogen]]—an inevitable byproduct of long-term [[liquid hydrogen]] storage in the [[Radiative heat transfer|radiative heat]] environment of space—for both [[orbital stationkeeping]] and [[Spacecraft attitude control|attitude control]].<ref name=aiaa20100902>{{cite web|last=Zegler|first=Frank |title=Evolving to a Depot-Based Space Transportation Architecture |url=http://www.ulalaunch.com/site/docs/publications/DepotBasedTransportationArchitecture2010.pdf |archive-url=https://web.archive.org/web/20110717150155/http://www.ulalaunch.com/site/docs/publications/DepotBasedTransportationArchitecture2010.pdf |url-status=dead |archive-date=2011-07-17 |work=AIAA SPACE 2010 Conference & Exposition |publisher=AIAA |access-date=2011-01-25 |author2=Bernard Kutter |date=2010-09-02 }} See page 3.</ref>
| Only useful in space, as thrust is fairly low, but hydrogen has not been traditionally thought to be easily stored in space,<ref name=aiaa20100902/> otherwise moderate/low [[Specific impulse|''I''sp]] if higher–molecular-mass propellants are used.
|}

====Beamed thermal====

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Laser propulsion|Light-beam-powered rocket]]
| Propellant is heated by light beam (often laser) aimed at vehicle from a distance, either directly or indirectly via heat exchanger
| Simple in principle, in principle very high exhaust speeds can be achieved
| ~1 MW of power per kg of payload is needed to achieve orbit, relatively high accelerations, lasers are blocked by clouds, fog, reflected laser light may be dangerous, pretty much needs hydrogen monopropellant for good performance which needs heavy tankage, some designs are limited to ~600 seconds due to reemission of light since propellant/heat exchanger gets white hot
|-
! [[Beam-powered propulsion|Microwave-beam-powered rocket]]
| Propellant is heated by microwave beam aimed at vehicle from a distance
| [[Specific impulse|''I''sp]] is comparable to Nuclear Thermal rocket combined with T/W comparable to conventional rocket. While LH2 propellant offers the highest Isp and rocket payload fraction, ammonia or methane are economically superior for earth-to-orbit rockets due to their particular combination of high density and Isp. [[Single-stage-to-orbit|SSTO]] operation is possible with these propellants even for small rockets, so there are no location, trajectory and shock constraints added by the rocket staging process. Microwaves are 10-100× cheaper in $/watt than lasers and have all-weather operation at frequencies below 10 GHz.
| 0.3–3{{nbsp}}MW of power per kg of payload is needed to achieve orbit depending on the propellant,<ref>{{cite web|url=http://parkinresearch.com/microwave-thermal-rockets/|title=Microwave Thermal Rockets|last=Parkin|first=Kevin|access-date=8 December 2016}}</ref> and this incurs infrastructure cost for the beam director plus related R&D costs. Concepts operating in the millimeter-wave region have to contend with weather availability and high altitude beam director sites as well as effective transmitter diameters measuring 30–300 meters to propel a vehicle to LEO. Concepts operating in X-band or below must have effective transmitter diameters measured in kilometers to achieve a fine enough beam to follow a vehicle to LEO. The transmitters are too large to fit on mobile platforms and so microwave-powered rockets are constrained to launch near fixed beam director sites.
|}

====Nuclear thermal====

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Radioisotope rocket|Radioisotope rocket/"Poodle thruster"]] (radioactive decay energy)
| Heat from radioactive decay is used to heat hydrogen
| About 700–800 seconds, almost no moving parts
| Low thrust/weight ratio.
|-
! [[Nuclear thermal rocket]] (nuclear fission energy)
| Propellant (typically, hydrogen) is passed through a nuclear reactor to heat to high temperature
| [[Specific impulse|''I''sp]] can be high, perhaps 900 seconds or more, above unity thrust/weight ratio with some designs
| Maximum temperature is limited by materials technology, some radioactive particles can be present in exhaust in some designs, nuclear reactor shielding is heavy, unlikely to be permitted from surface of the Earth, thrust/weight ratio is not high.
|}

===Nuclear===
[[Nuclear propulsion]] includes a wide variety of [[spacecraft propulsion|propulsion]] methods that use some form of [[nuclear reaction]] as their primary power source. Various types of nuclear propulsion have been proposed, and some of them tested, for spacecraft applications:

{| class="wikitable"
|-
! Type
! Description
! Advantages
! Disadvantages
|-
! [[Gas core reactor rocket]] (nuclear fission energy)
| Nuclear reaction using a gaseous state fission reactor in intimate contact with propellant
| Very hot propellant, not limited by keeping reactor solid, [[Specific Impulse|''I''sp]] between 1,500 and 3,000 seconds but with very high thrust
| Difficulties in heating propellant without losing fissionables in exhaust, massive thermal issues particularly for nozzle/throat region, exhaust almost inherently highly radioactive. Nuclear lightbulb variants can contain fissionables, but cut [[Specific Impulse|''I''sp]] in half.
|-
! [[Fission-fragment rocket]] (nuclear fission energy)
| Fission products are directly exhausted to give thrust.
|
| Theoretical only at this point.
|-
! [[Fission sail]] (nuclear fission energy)
| A sail material is coated with fissionable material on one side.
| No moving parts, works in deep space
| Theoretical only at this point.
|-
! [[Nuclear salt-water rocket]] (nuclear fission energy)
| Nuclear salts are held in solution, caused to react at nozzle
| Very high [[Specific Impulse|''I''sp]], very high thrust
| Thermal issues in nozzle, propellant could be unstable, highly radioactive exhaust. Theoretical only at this point.
|-
! [[Nuclear pulse propulsion]] (exploding fission/fusion bombs)
| Shaped nuclear bombs are detonated behind vehicle and blast is caught by a 'pusher plate'
| Very high [[Specific Impulse|''I''sp]], very high thrust/weight ratio, no show stoppers are known for this technology.
| Never been tested, pusher plate may [[spall|throw off fragments]] due to shock, minimum size for nuclear bombs is still pretty big, expensive at small scales, nuclear treaty issues, fallout when used below Earth's magnetosphere.
|-
! [[Antimatter catalyzed nuclear pulse propulsion]] (fission and/or fusion energy)
| Nuclear pulse propulsion with antimatter assist for smaller bombs
| Smaller sized vehicle might be possible
| Containment of antimatter, production of antimatter in macroscopic quantities is not currently feasible. Theoretical only at this point.
|-
! [[Fusion rocket]] (nuclear fusion energy)
| Fusion is used to heat propellant
| Very high exhaust velocity
| Largely beyond current state of the art.
|-
! [[Antimatter rocket]] (annihilation energy)
| Antimatter annihilation heats propellant
| Extremely energetic, very high theoretical exhaust velocity
| Problems with antimatter production and handling; energy losses in [[neutrino]]s, [[gamma ray]]s, [[muon]]s; thermal issues. Theoretical only at this point.
|}

==History of rocket engines==
{{main|History of rockets}}
According to the writings of the Roman [[Aulus Gellius]], the earliest known example of [[jet propulsion]] was in c. 400 BC, when a [[Greek people|Greek]] [[Pythagoreanism|Pythagorean]] named [[Archytas]], propelled a wooden bird along wires using steam.<ref>{{cite book |author=Leofranc Holford-Strevens|title=Aulus Gellius: An Antonine Author and his Achievement|publisher=Oxford University Press|edition=Revised paperback |date=2005 |isbn=0-19-928980-8 }}
</ref><ref>{{cite EB1911 |wstitle=Archytas |volume=2 |page=446}}</ref> However, it was not powerful enough to take off under its own thrust.

The ''[[aeolipile]]'' described in the first century BC, often known as ''[[Hero's engine]]'', consisted of a pair of [[steam rocket]] nozzles mounted on a [[Bearing (mechanical)|bearing]]. It was created almost two millennia before the [[Industrial Revolution]] but the principles behind it were not well understood, and it was not developed into a practical power source.

The availability of [[black powder]] to propel projectiles was a precursor to the development of the first solid rocket. Ninth Century [[Chinese people|Chinese]] [[Taoist]] [[Alchemy|alchemists]] discovered black powder in a search for the [[elixir of life]]; this accidental discovery led to [[fire arrow]]s which were the first rocket engines to leave the ground.

It is stated{{By whom|date=May 2022}} that "the reactive forces of incendiaries were probably not applied to the propulsion of projectiles prior to the 13th century".{{Citation needed|date=May 2024}} A turning point in rocket technology emerged with a short manuscript entitled ''Liber Ignium ad Comburendos Hostes'' (abbreviated as ''The Book of Fires''). The manuscript is composed of recipes for creating incendiary weapons from the mid-eighth to the end of the thirteenth centuries—two of which are rockets. The first recipe calls for one part of colophonium and sulfur added to six parts of saltpeter (potassium nitrate) dissolved in [[Lauraceae|laurel]] oil, then inserted into hollow wood and lit to "fly away suddenly to whatever place you wish and burn up everything". The second recipe combines one pound of sulfur, two pounds of charcoal, and six pounds of saltpeter—all finely powdered on a marble slab. This powder mixture is packed firmly into a long and narrow case. The introduction of saltpeter into pyrotechnic mixtures connected the shift from hurled [[Greek fire]] into self-propelled rocketry.<ref>{{cite book|last1=Von Braun|last2= Ordway III|first1=Wernher |first2= Frederick I.|title=The Rockets' Red Glare|url=https://archive.org/details/rocketsredglare0000vonb|url-access=registration|date=1976|publisher=Anchor Press/ Doubleday|location=Garden City, New York|isbn=978-0-385-07847-4|page=[https://archive.org/details/rocketsredglare0000vonb/page/5 5]}}</ref>

Articles and books on the subject of rocketry appeared increasingly from the fifteenth through seventeenth centuries. In the sixteenth century, German military engineer Conrad Haas (1509–1576) wrote a manuscript which introduced the construction of multi-staged rockets.<ref>{{cite book|last1=Von Braun|last2= Ordway III|first1=Wernher |first2= Frederick I.|title=The Rockets' Red Glare|url=https://archive.org/details/rocketsredglare0000vonb|url-access=registration|date=1976|publisher=Anchor Press/ Doubleday|location=Garden City, New York|isbn=978-0-385-07847-4|page=[https://archive.org/details/rocketsredglare0000vonb/page/11 11]}}</ref>

Rocket engines were also put in use by [[Tippu Sultan]], the king of [[Mysore]]. These usually consisted of a tube of soft hammered iron about {{convert|8|in|cm|abbr=on}} long and {{convert|1+1/2|-|3|in|cm|abbr=on}} diameter, closed at one end, packed with black powder propellant and strapped to a shaft of bamboo about {{convert|4|ft|cm|abbr=on}} long. A rocket carrying about one pound of powder could travel almost {{convert|1000|yd|m}}. These 'rockets', fitted with swords, would travel several meters in the air before coming down with sword edges facing the enemy. These were used very effectively against the British empire.

===Modern rocketry===
Slow development of this technology continued up to the later 19th century, when Russian [[Konstantin Tsiolkovsky]] first wrote about [[liquid-propellant rocket|liquid-fuelled rocket engines]]. He was the first to develop the [[Tsiolkovsky rocket equation]], though it was not published widely for some years.

The modern solid- and liquid-fuelled engines became realities early in the 20th century, thanks to the American physicist [[Robert Goddard (scientist)|Robert Goddard]]. Goddard was the first to use a [[De Laval nozzle]] on a solid-propellant (gunpowder) rocket engine, doubling the thrust and increasing the efficiency by a factor of about twenty-five. This was the birth of the modern rocket engine. He calculated from his independently derived rocket equation that a reasonably sized rocket, using solid fuel, could place a one-pound payload on the Moon.

===The era of liquid-fuel rocket engines===
Goddard began to use liquid propellants in 1921, and in 1926 became the first to launch a liquid-fuelled rocket. Goddard pioneered the use of the De Laval nozzle, lightweight propellant tanks, small light turbopumps, thrust vectoring, the smoothly-throttled liquid fuel engine, regenerative cooling, and curtain cooling.<ref name=Sutton/>{{rp|247–266}}

During the late 1930s, German scientists, such as [[Wernher von Braun]] and [[Hellmuth Walter]], investigated installing liquid-fuelled rockets in military aircraft ([[Heinkel He 112]], [[Heinkel He 111|He 111]], [[Heinkel He 176|He 176]] and [[Messerschmitt Me 163]]).<ref>{{cite book|author=Lutz Warsitz|title=The First Jet Pilot – The Story of German Test Pilot Erich Warsitz|publisher=Pen and Sword Ltd.|date=2009|isbn=978-1-84415-818-8}} Includes von Braun's and Hellmuth Walter's experiments with rocket aircraft. [http://www.pen-and-sword.co.uk/?product_id=1762 English edition.]</ref>

The turbopump was employed by German scientists in World War II. Until then cooling the nozzle had been problematic, and the [[V-2 rocket|A4]] ballistic missile used dilute alcohol for the fuel, which reduced the combustion temperature sufficiently.

[[Staged combustion cycle (rocket)|Staged combustion]] (''Замкнутая схема'') was first proposed by [[Aleksei Mihailovich Isaev|Alexey Isaev]] in 1949. The first staged combustion engine was the S1.5400 used in the Soviet planetary rocket, designed by Melnikov, a former assistant to Isaev.<ref name=Sutton>{{cite book|last=Sutton|first=George P.|title=History of Liquid Propellant Rocket Engines|date=2005|publisher=American Institute of Aeronautics and Astronautics|location=Reston, Virginia}}</ref> About the same time (1959), [[Nikolai Dmitriyevich Kuznetsov|Nikolai Kuznetsov]] began work on the closed cycle engine [[NK-9]] for Korolev's orbital ICBM, GR-1. Kuznetsov later evolved that design into the [[NK-15]] and [[NK-33]] engines for the unsuccessful Lunar [[N1 rocket]].

In the West, the first laboratory staged-combustion test engine was built in Germany in 1963, by [[Ludwig Boelkow]].

Liquid hydrogen engines were first successfully developed in America: the [[RL-10]] engine first flew in 1962. Its successor, the [[Rocketdyne J-2]], was used in the [[Apollo program]]'s [[Saturn V]] rocket to send humans to the Moon. The high specific impulse and low density of liquid hydrogen lowered the upper stage mass and the overall size and cost of the vehicle.

The record for most engines on one rocket flight is 44, set by NASA in 2016 on a [[Black Brant (rocket)|Black Brant]].<ref>{{Cite web | url=https://www.space.com/33810-nasa-world-record-most-rocket-engines.html |title = NASA and Navy Set World Record for Most Engines in One Rocket Flight|website = [[Space.com]]|date = 19 August 2016}}</ref>

==See also==
* [[Comparison of orbital rocket engines]]
* [[Rotating detonation engine]]
* [[Jet damping]], an effect of the exhaust jet of a rocket that tends to slow a vehicle's rotation speed
* [[Model rocket motor classification]] lettered engines
* [[NERVA]] (Nuclear Energy for Rocket Vehicle Applications), a US nuclear thermal rocket programme
* [[Photon rocket]]
* [[Project Prometheus]], NASA development of nuclear propulsion for long-duration spaceflight, begun in 2003
* [[Rocket propulsion technologies (disambiguation)]]

==Notes==
{{reflist|group =notes}}

==References==
{{reflist}}

==External links==
{{commons category|Rocket engines}}
{{Wiktionary}}
*[https://web.archive.org/web/20071009153749/http://www.pwrengineering.com/articles/longterm.htm Designing for rocket engine life expectancy]
*[https://web.archive.org/web/20071007070232/http://www.pwrengineering.com/articles/plume.htm Rocket Engine performance analysis with Plume Spectrometry]
*[https://web.archive.org/web/20071009151907/http://www.pwrengineering.com/articles/heart.htm Rocket Engine Thrust Chamber technical article]
*[http://www.fxsolver.com/browse/formulas/Net+Thrust+of+a+Rocket+Engine Net Thrust of a Rocket Engine calculator]
*[http://www.lpre.de/resources/software/RPA_en.htm Design Tool for Liquid Rocket Engine Thermodynamic Analysis]
*[http://www.braeunig.us/space/propuls.htm Rocket & Space Technology - Rocket Propulsion]
*[http://www.erichwarsitz.com/ The official website of test pilot Erich Warsitz (world's first jet pilot) which includes videos of the Heinkel He 112 fitted with von Braun's and Hellmuth Walter's rocket engines (as well as the He 111 with ATO Units)]

{{Rocket engines}}
{{Aircraft gas turbine engine components}}
{{Heat engines|state=uncollapsed}}

{{Authority control}}

{{DEFAULTSORT:Rocket Engine}}
[[Category:Aerospace technologies]]
[[Category:Rocket engines| ]]

Talk:War in Donbas

2023-06-04T10:41:39Z

88.163.124.35: /* Use "russian-speaking" instead "russian" everywhere in the article */ new section

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== Changing title ==

<s>This title “War in Donbas” just proves Russian trolls’ points about “Ukraine bombing Donbas”. I think it should be renamed to the “Insurgency in Donbas”. Then, Wikipedia would not have any Russian propaganda! [[User:TankDude2000|TankDude2000]] ([[User talk:TankDude2000|talk]]) 17:53, 20 February 2023 (UTC)</s>

Non-extended-confirmed users (including [[User:TankDude2000]]) may not make edits in internal project discussions, including requested moves, in this topic area, per [[wp:GS/RUSUKR]]. —''[[user:Mzajac|Michael]] [[user_talk:Mzajac|Z]].'' 15:47, 20 April 2023 (UTC)

:It was not an insurgency. Courts have found that in eastern Ukraine from mid-May 2014 there was an international conflict, and not a civil war, because Russian soldiers and illegal combatants were waging war and the militia organizations were under overall control of Russia.  —''[[user:Mzajac|Michael]] [[user_talk:Mzajac|Z]].'' 18:11, 20 February 2023 (UTC)

:No idea what you’re trying to get at. What exactly is your policy reasoning for changing the title? [[User:HappyWithWhatYouHaveToBeHappyWith|HappyWith]] ([[User talk:HappyWithWhatYouHaveToBeHappyWith|talk]]) 18:47, 20 February 2023 (UTC)

:Regardless of court definitions, the common name for the past eight years was "war" and that's what we are going with as per WP guidelines. Also, there was both a discussion and editor consensus reached at the start of the conflict regarding its name, as well as a more recent discussion/consensus (last year) when this phase of the overall [[Russo-Ukrainian War]] ended and the invasion phase started which basically reaffirmed the title, with the addition of the year span. Best regards! [[User:EkoGraf|EkoGraf]] ([[User talk:EkoGraf|talk]]) 22:10, 20 February 2023 (UTC)

== Change title ==

<s>[[War in Donbas (2014-2022)]] -> [[War in Donbas]] The title would be shorter. Plus, if we are going to reffer to the current situation in Donbas, we would use the title [[Battle of Donbas (2022-present)]]. [[User:TankDude2000|TankDude2000]] ([[User talk:TankDude2000|talk]]) 15:40, 4 April 2023 (UTC)</s>

Non-extended-confirmed users (including [[User:TankDude2000]]) may not make edits in internal project discussions, including requested moves, in this topic area, per [[WP:GS/RUSUKR]]. —''[[user:Mzajac|Michael]] [[user_talk:Mzajac|Z]].'' 15:47, 20 April 2023 (UTC)

:Why [[User:TankDude2000|TankDude2000]] ([[User talk:TankDude2000|talk]]) 16:17, 22 April 2023 (UTC)
::The link is right there: [[WP:GS/RUSUKR]] [[User:HappyWithWhatYouHaveToBeHappyWith|HappyWith]] ([[User talk:HappyWithWhatYouHaveToBeHappyWith|talk]]) 02:47, 23 April 2023 (UTC)
:Wikipedia is becoming so undemocratic! [[User:TankDude2000|TankDude2000]] ([[User talk:TankDude2000|talk]]) 18:11, 26 April 2023 (UTC)
::@[[User:TankDude2000|TankDude2000]]: for “democracy,” see [[WP:NOTDEMOCRACY]].
::For “censoring,” please reread provisions C and D at [[WP:GS/RUSUKR]], and be aware that more stringent measures may be taken to enforce the community sanctions if you continue violating it.  —''[[user:Mzajac|Michael]] [[user_talk:Mzajac|Z]].'' 18:47, 26 April 2023 (UTC)

== Edit request ==
{{Edit extended-protected|War in Donbas (2014–2022)|answered=yes}}Please [[WP:BLPREMOVE]] the fully unsourced paragraph between{{sxhl|<nowiki>''[[Novaya Gazeta]]'' concluded in 2020 that, as long Russia doesn't prosecute these "poorly prepared hooligans turning a whole region into a bloodbath", it is morally and politically responsible for all casualties.<ref name=":2">{{Cite web |title=Бесславные гибриды |url=https://novayagazeta.ru/articles/2020/07/17/86300-besslavnye-gibridy |access-date=20 July 2020 |website=Новая газета – Novayagazeta.ru |language=ru}}</ref></nowiki>}}and{{sxhl|<nowiki>=== Expansion of separatist territorial control ===</nowiki>}} [[Special:Contributions/89.206.112.12|89.206.112.12]] ([[User talk:89.206.112.12|talk]]) 13:10, 28 April 2023 (UTC)
:[[File:Red information icon with gradient background.svg|20px|link=|alt=]] '''Not done for now:''' It's not clear why you want this text removed. [[User:Mattdaviesfsic|Mattdaviesfsic]] ([[User talk:Mattdaviesfsic|talk]]) 13:34, 28 April 2023 (UTC)
<templatestyles src="Block indent/styles.css"/><div class="block-indent " {{#if:{{#expr:1.6*2}}|style="{{#if:{{#expr:1.6*2}}|padding-left: {{#expr:1.6*2}}em;}}{{#if:|padding-right: {{{right}}}em;}}{{#if:|{{{style}}}}}"}}>per [[WP:BLPREMOVE]] criterion 1 {{tq2|'''contentious material about living persons that is unsourced should be removed immediately and without discussion'''.}} and there is not a single [[WP:BLPRS]] here. [[Special:Contributions/89.206.112.12|89.206.112.12]] ([[User talk:89.206.112.12|talk]]) 13:48, 28 April 2023 (UTC)</div>
:[[File:Red information icon with gradient background.svg|20px|link=|alt=]] '''Not done:''' The text is already supported by a reliable source, as you have linked to above. Why this might be "contentious", I don't know. [[User:Mattdaviesfsic|Mattdaviesfsic]] ([[User talk:Mattdaviesfsic|talk]]) 13:55, 28 April 2023 (UTC)
<templatestyles src="Block indent/styles.css"/><div class="block-indent " {{#if:{{#expr:1.6*2}}|style="{{#if:{{#expr:1.6*2}}|padding-left: {{#expr:1.6*2}}em;}}{{#if:|padding-right: {{{right}}}em;}}{{#if:|{{{style}}}}}"}}>I'm refering to the paragraph ''after'' the citation linked above. How can it be {{tq|q=1|already supported by a reliable source}} when it does not mention a single reference for its criminal accusations that I avoided repeating here as per the header at [[WP:BLPN]]? [[Special:Contributions/89.206.112.12|89.206.112.12]] ([[User talk:89.206.112.12|talk]]) 14:16, 28 April 2023 (UTC)</div>
:{{Not done}} Mandatory form "Please change X to Y" not used. [[User:Rsk6400|Rsk6400]] ([[User talk:Rsk6400|talk]]) 14:23, 28 April 2023 (UTC)
:I removed the unsourced and contentious BLP material. [[User:ScottishFinnishRadish|ScottishFinnishRadish]] ([[User talk:ScottishFinnishRadish|talk]]) 15:39, 28 April 2023 (UTC)

== Refugees ==

Please add number of refugees - [https://www.ohchr.org/en/press-releases/2016/03/ukraine-growing-despair-among-over-three-million-civilians-conflict-zone-un] [https://en.interfax.com.ua/news/general/328981.html] ''The report also said that Ukrainian government registered 1.6 million internally displaced persons, who fled their homes as a result of the conflict. From 800,000 to 1 million of them lived on Kyiv-controlled territory, the report said.'' [[User:Manyareasexpert|Manyareasexpert]] ([[User talk:Manyareasexpert|talk]]) 22:02, 3 May 2023 (UTC)

== The war started on April 6th, not April 12th 2014 ==

The [[War in Donbas (2014–2022)]] and the absolute rebellion began on April 6, 2014 in [[Donetsk]] and [[Luhansk]], and on April 12 it only escalated into an [[armed uprising]]. In the period of six days (April 6 - 12), there were already dozens of injured and wounded. The first military corps of the armed forces of Ukraine entered the Donbass on April 9, and [[Siege of Sloviansk|the uprising in Sloviansk]] and [[Battle of Kramatorsk|Kramatorsk]] was still three days away. [[Capture of Donetsk (2014)|April 6 is the precise date of the beginning]] of [[War in Donbas (2014–2022)|the war in Donbass (2014 - 2022)]] when the rebels seized state institutions in the two largest cities of Donbass, Donetsk and Lugansk. The following day, the unrecognized [[Donetsk People's Republic|Donetsk]] and [[Lugansk People's Republic]]s were formed, and in the next six days, the rebels occupied various administrative offices. There are sources of information about all this. I don't hear anything vague. – [[User:Baba Mica|Baba Mica]] ([[User talk:Baba Mica|talk]]) 20:57, 25 May 2023 (UTC)

:What “absolute rebellion”? [[2014 pro-Russian unrest in Ukraine|Pro-Russian demonstrations]] began February 23, 2014, not April 6. They included violence, and I believe their first fatal victim was in Donetsk on March 13. This was not the Donbas War.
:The first military operation by Russian-controlled forces started April 12, 2014, and they haven’t stopped fighting yet.  —''[[user:Mzajac|Michael]] [[user_talk:Mzajac|Z]].'' 21:32, 25 May 2023 (UTC)
::For the record, here is my edit with sources.[https://en.wikipedia.org/w/index.php?title=War_in_Donbas_%282014%E2%80%932022%29&diff=1156647977&oldid=1156599046]
::* {{Cite book |last=Galeotti |first=Mark |title=Armies of Russia's war in Ukraine |last2=Hook |first2=Adam |date=2019 |publisher=Osprey Publishing |isbn=978-1-4728-3345-7 |editor-last=Windrow |editor-first=Martin |series=Elite |location=Oxford New York, NY}}, pages=14–16.
::* {{Cite book |last=Mitrokhin |first=Nikolay |title=Civil war? Interstate war? Hybrid war? dimensions and interpretations of the Donbas Conflict in 2014-2020 |date=2021 |publisher=ibidem Verlag |isbn=978-3-8382-7383-9 |editor-last=Hauter |editor-first=Jakob |series=Soviet and post-Soviet politics and society |location=Stuttgart |chapter=Infiltration, Instruction, Invasion: Russia’s War in the Donbas |editor-last2=Wilson |editor-first2=Andrew}}, page=115.
:: —''[[user:Mzajac|Michael]] [[user_talk:Mzajac|Z]].'' 22:51, 26 May 2023 (UTC)

:{{u|Baba Mica}}, where are your sources for the claim that "the war started on April 6th"? This is the line you added to the lead: {{tq|"The war nominally commenced on 6 April 2014,[http://www.globalpost.com/dispatch/news/afp/140416/ukraines-eastern-hot-spots] with the Ukrainian government announcing a large scale military response to pro-Russian separatists"}}. That reference doesn't say the war began on April 6th, it says "demonstrators stormed the government building on April 6". Armed separatists [[Siege of Sloviansk|seized Sloviansk]] on April 12th, and the Ukrainian government began its anti-terrorist operation on April 15th. – [[User:Asarlaí|Asarlaí]] ([[User talk:Asarlaí|talk]]) 09:09, 26 May 2023 (UTC)
::On April 6, there was an escalation of the conflict with the incursion of pro-Russian or Russian separatists in Donetsk and Luhansk into state institutions, and on April 12 they occupied state institutions in Sloviansk and Kramatorsk. Before the start of Ukrainian ATO on April 13, pro-Russian separatists occupied state institutions in Mariupol as well. On April 6, the burning of tires, the setting up of barricades and numerous injuries to members of the Ukrainian police began. The army of Ukraine started the military operation only on April 15, nine days late, and the Russians have already occupied strategic points in Donetsk, Lugansk, Sloviansk, Kramatorsk, Mariupol and Baḫmut. In 2014, the armed forces of Ukraine were quite late with the ATO, and Russia already had logistics ready to raise a rebellion. The [[2014 pro-Russian unrest in Ukraine|protests]] lasted from February 23 to April 6, when separatists permanently occupied government buildings in Donetsk and Lugansk with the intention of escalating the conflict, which only spread to other cities on April 12. Ukraine was not militarily strong at the time, and on April 6, the separatists also occupied [[Kharkiv]]. However, at the last moment, the authorities suppressed the uprising in Kharkiv on April 30. A rebellion broke out in Odessa on April 16, when the ''Odessa People's Republic'' was proclaimed, and two days after the suppression of the rebellion in Kharkiv, emboldened Ukrainian nationalists brutally suppressed the [[2014 Odesa clashes|rebellion in Odessa]], which led to the collapse of [[2014 pro-Russian unrest in Ukraine|pro-Russian protests in Russian-speaking regions]]. However, it was already too late for Donbas due to mass desertion and active Russian assistance in armaments. – [[User:Baba Mica|Baba Mica]] ([[User talk:Baba Mica|talk]]) 22:49, 26 May 2023 (UTC)

:::Simple question. Sources explicitly stating a start to the war on 6 April? [[User:Cinderella157|Cinderella157]] ([[User talk:Cinderella157|talk]]) 23:11, 26 May 2023 (UTC)
:::Baba Mica, everything on Wikipedia must be [[Wikipedia:Verifiability|verifiable]]. Michael has shown us sources saying the war began on 12 April, but you haven't shown us any sources saying it began on 6 April. We know government buildings were occupied by separatists around that time, but the first ''armed'' capture and first armed conflict were on 12 April (see [[Siege of Sloviansk]] and [[Battle of Kramatorsk]]). – [[User:Asarlaí|Asarlaí]] ([[User talk:Asarlaí|talk]]) 23:15, 26 May 2023 (UTC)
::::What is important and fundamental are both Ukrainian and Russian claims that the general uprising began on April 6 with the capture of Donetsk and Luhansk. Kramatorsk and Sloviansk were occupied only six days later. From February 23 to April 6, there were mostly peaceful protests combined with occasional riots and clashes with the police and occasional deaths. Institutions were attacked mostly on Sundays. Since April 6, the institutions in Donetsk and Luhansk have been permanently occupied, which led to radicalization the very next day, when two separatist states, [[DPR]] and [[LNR]], were declared. Riots and clashes became a daily occurrence between April 6 and 12 throughout Donbass. On April 6, Russia decided to start a rougher game aimed at, at best, wider decentralization and autonomy of the Donbass and Russophone areas, and at worst, direct separation, which will occur de facto on May 11, 2014, and de jure on February 21, 2022. three days before the invasion. Numerous sources in the chronology of this eight-year, small-scale war speak of constant clashes with the use of firearms between April 6 and 12, both in [[Donetsk]] and [[Luhansk]], and throughout the [[Donbass]]. Things escalate on April 12 into a wider conflict after [[Sloviansk]] and [[Kramatorsk]] when the Ukrainian leadership launches the ATO the next morning. Between April 6 and 12, numerous roadblocks sprung up across Donbas, which is a clear act of the beginning of the civil war and armed rebellion. On April 6, 2014, Ukraine lost control over the two most important cities in Donbass (Donetsk and Luhansk), although the army still controlled some peripheral parts of the city. However, Ukraine at that time, which had not yet stabilized after the Maidan, did not lose between April 6 and 12 Donetsk and Lugansk and some other places due to some military success of the separatists, but due to the mass desertion of Russian personnel employed in security structures. The first resistance of that transitional government of Yatsenyuk came only after the loss of Sloviansk and Kramatorsk on April 12, when it became clear that the separatists did not want negotiations but secession along the lines of Crimea, and after that day the then head of the [[CIA]] visited Kiev and presented a detailed plan to interim president Turchynov the USA will stand behind the territorial integrity of Ukraine. This encouraged the then acting president to launch ATO on April 13, which he did. Between April 6 and 13, the cities of Donbass fell one after the other like pears due to mass desertion (instigated and coordinated from Moscow) until the Ukrainian authorities used force after Sloviansk and Kramatorsk because there was a danger that it would be their turn after Donetsk and Luhansk Oblasts Kharkiv Dnipropetrovsk and Zaporizhia Oblasts, and in correlation with the USA, a decision was reached to at least limit the inevitable armed conflict to Donetsk and Luhansk Oblasts, which is what happened. The events between April 6 and 13 are the turning point of this war. If the Russians had not permanently occupied the residences or if they had been prevented on April 6, 2014, the separatist republics of the DPR and LNR would not have been declared on April 7 and 8, there would not have been mass desertions between April 6 and 13, it would not have been the same the scenario was easily implemented on April 12 in Sloviansk and Kramatorsk and Ukraine would not have been forced to start ATO in Donbass on April 13. This event is the most important and key moment of the beginning of this limited war '''[[Capture of Donetsk (2014)]]'''. A template for this article needs to be created urgently, and an article on the '''[[Capture of Lugansk (2014)]]''' is also needed. Everything started on the same day and went on the path of escalation and peaceful protests suddenly turned into riots and desertion, and desertion is an act of war. Another thing is that Ukraine hesitated to suppress the rebellion for seven days, so the separatists got stronger and occupied Sloviansk and Kramatorsk and subsequent Russian interference by inserting [[GRU]] agents like [[Igor Girkin|Igor Girkin Strelkov]]. The logistics were ready if Ukraine refused decentralization or federalization of the state, which the leadership from Kiev categorically refused, and the signal from Moscow was given that after the third raid on the representative offices on April 6, there would be no more retreat and that the path of armed rebellion should be taken to all goals. It is likely that the Ukrainian leadership prolonged the ATO for seven days because of possible negotiations with the separatists and because of consultations with the USA, what if the separatists and Russia reject the Ukrainian proposals. In the meantime, the situation worsened, desertions increased and Sloviansk and Kramatorsk fell on April 12. After the devil took the joke and the rebellion began to spread more and more in the cities of Donbass, after assurances of support from Washington, Kiev was encouraged to start the ATO on April 13, but many cities and members of the authorities deserted between April 6 and 13 from the Ukrainian security structures and approached the separatists and formed their own parallel police and army that occupied in that second and crucial week of April 2014 town by town, place by place, village by village. – [[User:Baba Mica|Baba Mica]] ([[User talk:Baba Mica|talk]]) 01:37, 28 May 2023 (UTC)
:::::When did armed Russians enter eastern Ukraine and start fighting?  —''[[user:Mzajac|Michael]] [[user_talk:Mzajac|Z]].'' 14:11, 28 May 2023 (UTC)

:::::OP was asked to supply sources to support their claim but haven't. This wall of words is unhelpful. It does not address the issue of when sources say the war started, which is how we determine the matter. More of the same could easily be considered disruptive. [[User:Cinderella157|Cinderella157]] ([[User talk:Cinderella157|talk]]) 01:11, 29 May 2023 (UTC)

== Use "russian-speaking" instead "russian" everywhere in the article ==

"Russian" means from Russia.
"Russian-speaking" means speak russian.
All begins here. [[Special:Contributions/88.163.124.35|88.163.124.35]] ([[User talk:88.163.124.35|talk]]) 10:41, 4 June 2023 (UTC)

Talk:Valerii Zaluzhnyi

2023-06-02T07:47:12Z

88.163.124.35: /* Extended-confirmed-protected edit request on 25 May 2023 */ Reply

{{Gs/talk notice|topic=rusukr}}
{{WikiProject banner shell |living=yes |1=
{{WikiProject Biography|class=Start|living=yes|listas=Zaluzhnyi, Valerii}}
{{WikiProject Ukraine|class=start|importance=mid}}
{{WikiProject Military history|Biography=y|European=y|class=C|b1=no|b2=yes|b3=yes|b4=yes|b5=yes}}
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== USSR allegiance? ==

I'm not an expert on the subject, but it seems like he started his military career after 1991. And the article says he "did not serve in the USSR". He was born in USSR, but did he have USSR allegiance? — Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/37.73.57.241|37.73.57.241]] ([[User talk:37.73.57.241#top|talk]]) 14:52, 23 February 2022 (UTC) 

:If he joined the armed forces before 25 December 1991,then the answer is yes. A source confirming this would be good. [[User:Essex History|Essex History]] ([[User talk:Essex History|talk]]) 20:25, 10 May 2023 (UTC)
::The article is wrong, according to the Ukrainian government website, Zaluzhnyi entered the military in 1997. [[User:Essex History|Essex History]] ([[User talk:Essex History|talk]]) 20:27, 10 May 2023 (UTC)

== A Commons file used on this page or its Wikidata item has been nominated for deletion ==
The following Wikimedia Commons file used on this page or its Wikidata item has been nominated for deletion:
* [[commons:File:Zaluzhny2021.jpg|Zaluzhny2021.jpg]]
Participate in the deletion discussion at the [[commons:Commons:Deletion requests/Files uploaded by Fisherman1149|nomination page]]. —[[User:Community Tech bot|Community Tech bot]] ([[User talk:Community Tech bot|talk]]) 18:52, 19 June 2022 (UTC)

== swastika-armband ==

{{ping|Schläger4|}}, concerning your following edit: https://en.wikipedia.org/w/index.php?title=Valerii_Zaluzhnyi&type=revision&diff=1115092226&oldid=1115092063
and also the edit war initiated by an anonymous.
 Swastika can be seen on the original zoomed photo on Twitter: https://pbs.twimg.com/media/FeZ69HAWIAEe_uR?format=jpg&name=large
originating from Zaluzhnyi's tweet: https://twitter.com/CinC_AFU/status/1578083916296192000/photo/1
and a [https://deutsche-wirtschafts-nachrichten.de/700618/Oberkommandierender-der-Ukraine-zeigt-sich-mit-Hakenkreuz citation] in accordance with [[WP:RS]] is also provided [[User:Eugrus|eugrus]] ([[User talk:Eugrus|talk]]) 19:54, 9 October 2022 (UTC)

:Hi. Sorry for the oversight.
:I reverted my edit after checking the source.[[User:Schläger4|Schläger4]] [[User talk:Schläger4|(talk)]] 19:56, 9 October 2022 (UTC)
: I've removed the edit. I doubt that a website that has an entire section dedicated to the [[Great Reset]] conspiracy theory ([https://deutsche-wirtschafts-nachrichten.de/tag/35012/Great-Reset]) is [[WP:RS|reliable]] for such a [[WP:BLP|sensitive claim]]. [[User:Kleinpecan|Kleinpecan]] ([[User talk:Kleinpecan|talk]]) 20:20, 9 October 2022 (UTC)
:[https://nitter.net/Shtirlitz53/status/1579191642636300288#m A close-up of the bracelet was recently posted to Nitter.]
:[https://pakabone.com/eng/braslety/braslety-vikingov-midgard/poserebrennyy-braslet-viking-art-000-911.html This bracelet can be found on a Ukrainian site named Pakabone.] [[User:FreeFallingCement|FreeFallingCement]] ([[User talk:FreeFallingCement|talk]]) 20:25, 9 October 2022 (UTC)
:: Agree that the deutsche-wirtschafts-nachrichten.de source is thin and not sufficient by itself for such an assertion. [[User:Ohnoitsjamie|OhNoitsJamie]] [[User talk:Ohnoitsjamie|Talk]] 23:40, 9 October 2022 (UTC)

Those are Viking symbols. What is the fuss about? [[Special:Contributions/2601:647:5800:3B60:293A:FA92:47D0:1319|2601:647:5800:3B60:293A:FA92:47D0:1319]] ([[User talk:2601:647:5800:3B60:293A:FA92:47D0:1319|talk]]) 21:26, 11 October 2022 (UTC)

:Yes, such a symbol. A fact check by the [[Deutsche Presse-Agentur]] says that it is probably a [[Solomon's knot]].[https://dpa-factchecking.com/germany/221014-99-127338/] (German). [[User:KurtR|KurtR]] ([[User talk:KurtR|talk]]) 23:10, 17 October 2022 (UTC)
::And now another one, this time photo with [[Nazi Ukraine]] hero [[Stepan Bandera]] for his birthday celebration retweeted (and later removed) by Ukraine's parliament
::https://twitter.com/Dispropoganda/status/1610003321288548352 [[User:Joaziela|Joaziela]] ([[User talk:Joaziela|talk]]) 11:14, 5 January 2023 (UTC)
:::@TimothyBlue what is non-encyclopedic and POV in:
:::“On January 1, 2023 took a selfie with a portrait of [[Nazi Ukraine]] hero [[Stepan Bandera]] celebrated the 114th anniversary of the birth of ultra-nationalist and antisemite whose followers engaged in a campaign of ethnic cleansing against Jews and Poles during World War II as [[Volhynia genocide]] <ref>{{Cite web |title= Szef ukraińskiej armii z portretem Bandery. Wicemarszałek Sejmu: To skandal, prowokacja | url=https://www.polsatnews.pl/wiadomosc/2023-01-03/piotr-zgorzelski-i-prof-blazej-kmieciak-w-gosciu-wydarzen-transmisja-od-godz-1920/}}</ref><ref>{{Cite web |title=Ukrainian parliament, army leadership celebrate birthday of the fascist mass murderer Bandera | url=https://www.wsws.org/en/articles/2023/01/05/jnwx-j05.html}}</ref>“
:::You have some other view in Bandera, even [[Hero of Ukraine#Controversial awards]] was revoked, so that he is [[antisemitism]], [[antipolonism]] and responsible for [[Volhynia genocide]] is worth to mentioning [[User:Joaziela|Joaziela]] ([[User talk:Joaziela|talk]]) 11:58, 5 January 2023 (UTC)
::::@[[User:Joaziela|Joaziela]] The information you are trying to enter is [[WP:UNDUE]] for general bio article. You can try to create a new article about the incident if you want but please read [[WP:BLP]] first - [[User:GizzyCatBella|'''GizzyCatBella''']][[User talk:GizzyCatBella|🍁]] 14:49, 5 January 2023 (UTC)
{{BLP noticeboard}}

== Bandera and Verkhovna Rada ==

User @[[User:TimothyBlue|TimothyBlue]]is not even taking part in discussion, but deleted once again information about sad story about Zaluzhny and Bandera saying it’s poorly sourced, it’s [[Verkhovna Rada]] a poor source? It’s just censorship. I also put 3 articles from three different countries, those websites easily could be 20 more...
i know that Commander-in-Chief first with swastika-like, now with Bandera it’s not a good image, but Wikipedia it’s not a propaganda place for censorship, erased stories that don’t fit to narrative. Facts are the is photo with Bandera, promoted by parliament, that been international scandal mostly in Poland and Islael, because Bandera is a part of [[Volhynia genocide]] of Poles and Jews.

“On January 1, 2023 posted a selfie with a portrait of [[Nazi Ukraine]] hero [[Stepan Bandera]] (celebrated the 114th anniversary of the birth of ultra-nationalist and antisemite whose followers engaged in a campaign of ethnic cleansing against Jews and Poles during World War II as [[Volhynia genocide]]), retweeted by Ukrainian parliament [[Verkhovna Rada]] account, deleted after strong international criticism<ref>{{Cite web |title= Szef ukraińskiej armii z portretem Bandery. Wicemarszałek Sejmu: To skandal, prowokacja | url=https://www.polsatnews.pl/wiadomosc/2023-01-03/piotr-zgorzelski-i-prof-blazej-kmieciak-w-gosciu-wydarzen-transmisja-od-godz-1920/}}</ref><ref>{{Cite web |title=Ukrainian parliament, army leadership celebrate birthday of the fascist mass murderer Bandera | url=https://www.wsws.org/en/articles/2023/01/05/jnwx-j05.html}}</ref><ref>{{Cite web |title=Victory to Come When Russian Empire 'Ceases to Exist': Ukraine Parliament Quotes Nazi Collaborator | url=https://www.haaretz.com/world-news/europe/2023-01-02/ty-article/.premium/victory-to-come-when-russia-ceases-to-exist-ukraine-parliament-quotes-nazi-collaborator/00000185-71dc-de47-afdf-f3fdb3410000}}</ref>.”

could we we please bring it back or have any not-propaganda discussion... [[User:Joaziela|Joaziela]] ([[User talk:Joaziela|talk]]) 17:10, 6 January 2023 (UTC)

:@[[User:Joaziela|Joaziela]] - The issue is '''over the top''' POV tone but I also think it’s [[WP:UNDUE]] for general BLP Bio article. - [[User:GizzyCatBella|'''GizzyCatBella''']][[User talk:GizzyCatBella|🍁]] 17:32, 6 January 2023 (UTC)
::@[[User:GizzyCatBella|GizzyCatBella]] maybe you don’t see it from Jewish and Polish perspective (200 000 brutally murdered in Volhynia massacre) so analogy for Germany: “[[Federal Ministry of Defence (Germany)]] publish selfie with Hitler portrait, this been retweeted by [[Bundestag]] account” isn’t the huge af scandal, so yeah I know that for @[[User:TimothyBlue|TimothyBlue]] it’s might be not comfortable, but let’s be neutral no propaganda and [[historical negationism]], bring back the truth [[User:Joaziela|Joaziela]] ([[User talk:Joaziela|talk]]) 18:09, 6 January 2023 (UTC)
:::@[[User:Joaziela|Joaziela]] - [[Stepan Bandera|Bandera]] is not [[Adolf Hitler|Hitler]] (not even close) and I already answered [https://en.wikipedia.org/w/index.php?title=Wikipedia:Biographies_of_living_persons/Noticeboard&diff=1131977322&oldid=1131975508&diffmode=source here] - [[User:GizzyCatBella|'''GizzyCatBella''']][[User talk:GizzyCatBella|🍁]] 18:20, 6 January 2023 (UTC)
::::The you answered that it’s not a big deal because '''quickly removed''', and I’m saying you it stay for a long time, long enough to be put on official account of parliament, and '''it’s scandal enough that he took selfie with genocide criminal''', because yes, as well Bandera as Hitler was on top of criminal organizations: Bandera- OUN and Hitler- Nazi Party responsible for genocide of Jews and Poles [[Volhynia massacre]]. If you don’t think so and you are going to say that Bandera have nothing to do with war crimes and genocide, we have a huge problem here like [[genocide denial]] and [[historical negationism]], if not very please explain why you mean by “not even close”? [[User:Joaziela|Joaziela]] ([[User talk:Joaziela|talk]]) 18:43, 6 January 2023 (UTC)
:::I'm pretty good at seeing things for the perspective of a Polish Jew. Your personal attacks are very close to going to ANI.  // [[User:TimothyBlue|Timothy]] :: [[User talk:TimothyBlue|talk]]  18:22, 6 January 2023 (UTC)
::::@[[User:TimothyBlue|TimothyBlue]] there’s any personal attack on you at all (which part you read like it?). Please take a part in discussion, to maybe form it different way if you think this one it’s not okay, so far you only deleted without saying a word, so bring your perspective please. I presented Germany analogy, because Bandera is a genocide criminal and as I write it’s outrageous to even selfie not even saying that it’s go to Verkhovna Rada profile [[User:Joaziela|Joaziela]] ([[User talk:Joaziela|talk]]) 18:54, 6 January 2023 (UTC)

*This edit [https://en.wikipedia.org/w/index.php?title=Valerii_Zaluzhnyi&diff=1131961804&oldid=1131734494] and whole story are definitely "undue" on this page. Two first sources used in the edit are hardly RS. Third one is definitely an RS, but it is written on a different subject of Bandera and Verkhovna Rada (the title of this thread), although it does mention Zaluzhnyi in passing. [[User:My very best wishes|My very best wishes]] ([[User talk:My very best wishes|talk]]) 19:11, 6 January 2023 (UTC)
*:Very RS national news agency [[Polish Press Agency]] https://www.pap.pl/en/news/news%2C1516667%2Cpolish-mfa-unhappy-about-ukrainian-nationalist-leaders-commemoration.html and [[Ministry of Foreign Affairs (Poland)]] that express his discontent, is the source and Polish officials enough,
*:https://www.thefirstnews.com/article/pm-against-glorification-of-ukrainian-nationalist-bandera-35525
https://english.almayadeen.net/news/politics/poland-pm-to-remind-ukraine-that-glorifying-bandera-unaccept [[First News]] and even [[Al Mayadeen]] about not so happy [[Prime Minister of Poland]]
*:https://www.prezydent.pl/kancelaria/archiwum/archiwum-bronislawa-komorowskiego/aktualnosci/wydarzenia/z-konsternacja-przyjelismy-uhonorowanie-bandery,13602,archive [[President of Poland]] on his official site
*: next to previous one from [[Deputy Marshal of the Sejm]] Wicemarszałek Sejmu? Is that scandalous enough? Is it really about sources? Because those sources looks pretty solid and also why you don’t accept Ukrainian parliament as an RS? That come straight from them, so could we put this news on [[User:Joaziela|Joaziela]] ([[User talk:Joaziela|talk]]) 21:59, 6 January 2023 (UTC)
*::I propose a new version: “On January 1, 2023 Ukrainian parliament [[Verkhovna Rada]] Twitter account published a Zaluzhnyi selfie with a portrait of [[Nazi Ukraine]] [[Stepan Bandera]] with his books quotes (celebrated the 114th anniversary of the birth of ultra-nationalist and antisemite whose followers engaged in a campaign of ethnic cleansing against Jews and Poles during World War II as [[Volhynia genocide]]), deleted after strong international criticism, especially from Poland: [[President of Poland|President]], [[Prime Minister of Poland|Prime Minister]], [[Ministry of Foreign Affairs (Poland)|Ministry of Foreign Affairs]] and [[Deputy Marshal of the Sejm]]“, (ofc with all sources) better, any other ideas? [[User:Joaziela|Joaziela]] ([[User talk:Joaziela|talk]]) 22:15, 6 January 2023 (UTC)
*I see two serious problems here. First, a significant number of Ukrainians have a positive opinion of Bandera. Should we place "and he likes Bandera" on every BLP page? Secondly, we do not even know what Zaluzhnyi thinks about Bandera because ... he did not tell. Simply making such photo can mean anything, a joke, a prank, whatever, just to make Putin angry. [[User:My very best wishes|My very best wishes]] ([[User talk:My very best wishes|talk]]) 01:41, 7 January 2023 (UTC)
*:Please no [[reductio ad absurdum]], first not every BLP, only to those whose actions bring significant criticism from all officials from other country. This is why I bring “German analogy”, to understand it better, because it was post from official parliament of one country and it’s commander-in-chief. Please also not again with absurd “it is joke, prank” (as before @GizzyCatBella “quickly removed”). Genocide it’s not to joke about. Bandera had [[Volhynia genocide]], as Hitler had Holocaust. Maybe some one could write “not even close” again, but it’s not competition how is “greatest genocider by numbers”! Some will say that Hitler is also not even close by numbers to [[Mao Zedong]]- but genocide is genocide, not a competition.
*:And of course the are maybe some numbers of people who have positive opinion on Hiter as well, [[David Irving]] belief even that Adolf knew nothing of the Holocaust. But common sense and international consensus is that Hitler knew about Holocaust and Bandera is involved in killing Jews and Poles at Volhynia (no matter what some Ukrainians think [again “some”, I don’t think significant as you write, this is main Russian narrative for “denazification of Ukraine” claim])
*:So again: official statement from state authority of one country (to understand it seriousness use “German analogy” because genocide is not a competition), bring action from official statement from state authority of another country. [[User:Joaziela|Joaziela]] ([[User talk:Joaziela|talk]]) 12:16, 7 January 2023 (UTC)
:::This selfie got very little coverage, and when it mentioned (like [https://www.pap.pl/en/news/news%2C1516667%2Cpolish-mfa-unhappy-about-ukrainian-nationalist-leaders-commemoration.html here]), the sources say it was Rada who published this selfie. This incident is so minor it does not belong anywhere, but if it does, it would be page about Bandera or Rada, exactly as you noted yourself in the title of this thread, i.e. "Bandera and Verkhovna Rada". Could you answer to my WP:ANI question [https://en.wikipedia.org/w/index.php?title=Wikipedia:Administrators%27_noticeboard/Incidents&diff=prev&oldid=1132088593] please? [[User:My very best wishes|My very best wishes]] ([[User talk:My very best wishes|talk]]) 17:43, 7 January 2023 (UTC)
:::Like I said: "this incident is so minor it does not belong anywhere". If you think it belongs to any other page, please start discussion on talk of that other page and get WP:Consensus for inclusion.[[User:My very best wishes|My very best wishes]] ([[User talk:My very best wishes|talk]]) 19:27, 7 January 2023 (UTC)
::::This is not minor incident, joke or quickly removed! AGAIN Berlin analogy: “'''Official [[Bundestag]] Twitter post a [[Mein Kampf]] quotes with photo of [[Federal Ministry of Defence (Germany)]] posing with [[Adolf Hitler]] portrait, with strong reaction of Israel state authorities'''” the same happened to Ukraine and Poland.
::::Taking this selfie by such a person is scandal enough, but posting it by parliament just unbelievable villainy. This is HUGE scandal, and it would be on German Federal Minister page, so it should be on Ukrainian Commander-in-Chief. [[User:Joaziela|Joaziela]] ([[User talk:Joaziela|talk]]) 10:31, 8 January 2023 (UTC)
:::::@[[User:Joaziela|Joaziela]] please, '''enough'''. You keep repeating identical arguments on multiple pages. Look, there is no support for your desired changes. I understand that you still have to learn Wikipedia's standards of contribution and conduct, but this is too much. Your behaviour becomes disturbing, please, focus on a different subject. - [[User:GizzyCatBella|'''GizzyCatBella''']][[User talk:GizzyCatBella|🍁]] 11:41, 8 January 2023 (UTC)
::::::@[[User:GizzyCatBella|GizzyCatBella]] there are multiple pages, because @[[User:TimothyBlue|TimothyBlue]] and you are creating them and try to roast me on BLP and ANI, participate in discussion here. Here you try to call it as a minor incident or even joke, which is obvious [[WP:NOTCENSORED]] [[User:Joaziela|Joaziela]] ([[User talk:Joaziela|talk]]) 12:36, 8 January 2023 (UTC)
:::::::Once again, you say "Official Bundestag Twitter...". Hence, it would be about Bundestag and belong to page [[Bundestag]] assuming that the inclusion would be supported by WP:Consensus on talk page of article Bundestag. [[User:My very best wishes|My very best wishes]] ([[User talk:My very best wishes|talk]]) 18:51, 8 January 2023 (UTC)
::::::::On [[Verkhovna Rada]] you silenced it and saying it is „selfie of Zaluzhnyi” [https://en.wikipedia.org/w/index.php?title=Verkhovna_Rada&diff=1132204346&oldid=1132196879], here you say it belong there... so what to call it as one big CENSORSHIP???
::::::::If [[Christine Lambrecht]], Federal Minister of Defence did it, it would be even on [[Germany]] page and even create separate page for this '''antisemitic, hate speech hate crime''', but here follow Ukraine propaganda (as bad as Russian propaganda, it’s encyclopedia should be no propaganda) and try to call it minor incident, quickly removed joke. Just trying to silence it!
::::::::You have group of people who edit in proukrainian POV, roasting me personally creating threads on BLP and ANI, not discuss on topic here. Sources are very strong, there was a strong reaction from other country on action from two state authorities [[WP:NOTCENSORED]] again [[User:Joaziela|Joaziela]] ([[User talk:Joaziela|talk]]) 09:28, 9 January 2023 (UTC)
:::::::::No one is censoring anything. You need to follow [[WP:Consensus]] for including contentious materials, such as these, and especially on [[WP:BLP]] pages.[[User:My very best wishes|My very best wishes]] ([[User talk:My very best wishes|talk]]) 20:14, 9 January 2023 (UTC)
:::::::::@[[User:Joaziela|Joaziela]]’s arguments are obvious POV pushing, with demonizing language and easily verifiable disinformation. “Nazi Ukraine”?! “Genocidal criminal,” which they bludgeon us with repeatedly, is false: Bandera was recalled to Berlin and arrested two weeks into Barbarossa in July 1941, released in 1944, fleeing to Austria never to return to Ukraine or Poland, while the Volhynia massacres were conducted 1943 to 1945. “Antisemitic, hate speech hate crime,” if it refers to the article’s subject, is libellous and can’t be put into the article.
:::::::::This article is subject to [[WP:ACDS]] and [[WP:GS/RUSUKR]], and this kind of speech should not be humoured as acceptable here, or indeed in any discussion. —''[[user:Mzajac|Michael]] [[user_talk:Mzajac|Z]].'' 23:35, 11 January 2023 (UTC)
::::::::::(And the irony of them decrying “propaganda and historical negationism” at the same time.)  —''[[user:Mzajac|Michael]] [[user_talk:Mzajac|Z]].'' 23:39, 11 January 2023 (UTC)
:::::::::::@[[User:Mzajac|Mzajac]] This “arrests” was two room comfortable apartment (as for a Nazi collaborator)... you are very close to [[David Irving]] (claims there is no evidence of Hitler knowing of the Holocaust)... you don’t need to use weapon yourself to be responsible and still should be called genocide criminal...
:::::::::::Glorifying of Bandera really don’t help Ukraine, good that [[Hero of Ukraine]] award was annulled, but this kind of propaganda as you presented is very sad and show that pro[[Nazi Ukraine]] is unfortunately still strong
:::::::::::@[[User:My very best wishes|My very best wishes]] No censorship? so why it was put down also at [[Verkhovna Rada]] and even [[Stepan Bandera]]? [[User:Joaziela|Joaziela]] ([[User talk:Joaziela|talk]]) 15:53, 13 January 2023 (UTC)
::::::::::::@[[User:Joaziela|Joaziela]], please take a breath, delete or strike your comment, and apologize for implying that I’m a Nazi propagandist. —''[[user:Mzajac|Michael]] [[user_talk:Mzajac|Z]].'' 16:41, 13 January 2023 (UTC)
:::::::::::::Yeah, and once they do what you rightly asking them to do, perhaps '''you''' [[User:Mzajac|Mzajac]] will do the same [https://en.wikipedia.org/w/index.php?title=Wikipedia%3ABiographies_of_living_persons%2FNoticeboard&diff=1133189888&oldid=1133182403&diffmode=source here]? That would be great. Thanks - [[User:GizzyCatBella|'''GizzyCatBella''']][[User talk:GizzyCatBella|🍁]] 16:54, 13 January 2023 (UTC)
::::::::::::::Why, because you’ll advertise in discussions far and wide? Editors can follow your link and see that you unapologetically support Joaziela’s anti-Ukrainian disinformation there. They’re likely to find that you’re being disruptive on top of extremely inappropriate.  —''[[user:Mzajac|Michael]] [[user_talk:Mzajac|Z]].'' 17:10, 13 January 2023 (UTC)
{{ref-talk}}

== Unconfirmed reports ==

On 10th May there have been several, as yet, unconfirmed or verified reports that General Zaluzhnyi has been KIA.

Monitor official sources on this. [[User:Essex History|Essex History]] ([[User talk:Essex History|talk]]) 20:22, 10 May 2023 (UTC)

:the guy is dead [[Special:Contributions/185.188.190.137|185.188.190.137]] ([[User talk:185.188.190.137|talk]]) 18:36, 16 May 2023 (UTC)

:: not yet, Ivan. [[Special:Contributions/2601:647:5800:9120:FC10:37B9:E330:BF6E|2601:647:5800:9120:FC10:37B9:E330:BF6E]] ([[User talk:2601:647:5800:9120:FC10:37B9:E330:BF6E|talk]]) 05:04, 19 May 2023 (UTC)
:::Not every conveyor of information you don't like is Russian, troll.[[Special:Contributions/122.150.92.52|122.150.92.52]] ([[User talk:122.150.92.52|talk]]) 11:31, 20 May 2023 (UTC)
:::Im Slovak with obsesion in reading about current military operations and watching them unfold.
:::He is missing for 10 days now. The guy is 99% dead. [[Special:Contributions/185.188.190.137|185.188.190.137]] ([[User talk:185.188.190.137|talk]]) 18:12, 20 May 2023 (UTC)
:Ukraine’s Deputy Defence Minister, Hanna Maliar, says Russian claims of Zaluzhnyi's death are misinformation: https://news.yahoo.com/russia-spreads-false-claims-disappearance-185342725.html [[User:AncientWalrus|AncientWalrus]] ([[User talk:AncientWalrus|talk]]) 14:00, 22 May 2023 (UTC)
::Here is a summary from RS [https://www.lemonde.fr/international/live/2023/05/22/guerre-en-ukraine-en-direct-le-kremlin-reagit-a-l-incursion-d-un-groupe-ukrainien-de-sabotage-dans-la-region-de-belgorod_6174298_3210.html?#id-964388 Le Monde] (French) [[User:AncientWalrus|AncientWalrus]] ([[User talk:AncientWalrus|talk]]) 14:02, 22 May 2023 (UTC)
:::Further denial of injury from Ukr gov't https://news.yahoo.com/national-security-council-secretary-reacts-134746898.html [[User:AncientWalrus|AncientWalrus]] ([[User talk:AncientWalrus|talk]]) 21:09, 24 May 2023 (UTC)
::::It is interesting that you consider [[Ukrainska Pravda]] to be a credible source. But only time will tell. [[User:Carptrash|Carptrash]] ([[User talk:Carptrash|talk]]) 20:48, 26 May 2023 (UTC)
:::::Credible with regards to UKR government statements, yes. [[User:AncientWalrus|AncientWalrus]] ([[User talk:AncientWalrus|talk]]) 10:20, 27 May 2023 (UTC)
::::::The video linked here [https://kp.ua/ua/politics/a670304-valerij-zaluzhnij-zapisav-video-shchob-rozvijati-rosijski-fejki-pro-svoje-zdorovja] may be relevant, as may be this photo [https://t.me/ministry_of_defense_ua/7631]. In the video, a person looking very much like Zaluzhnyi (i.e. having both his physique and his mannerisms) directly addresses the rumours of him having been killed, meaning the video post-dates the supposed attack. If a Russian attack on a staff meeting near Bakhmut did actually take place, this would explain why he kept a much lower public presence in the last 2 weeks or so (the target coordinates would not have been widespread knowledge, thus an attack would indicate RU has infiltrated the UA chain-of-command at an unexpectedly high level), as well as the delay in major-scale UA offensive operations. (The question of whether the Russian equipment is actually in a condition to permit precision strikes nonwithstanding; RU propaganda indicated it as an artillery strike, but this is not in line of what is known and can be inferred about the quality of the RU artillery and ammunition. Not even Ukraine, with Cesars/PaH2000s and top-grade guided artillery ammunition, is able to conduct such strikes on a regular basis.) [[Special:Contributions/2A02:908:4B33:BD80:0:0:0:5FCF|2A02:908:4B33:BD80:0:0:0:5FCF]] ([[User talk:2A02:908:4B33:BD80:0:0:0:5FCF|talk]]) 20:18, 28 May 2023 (UTC)
:::::Some more RS discussion of the denials: [https://www.telegraph.co.uk/world-news/2023/05/25/ukraine-video-commander-valeriy-zaluzhnyi-alive-rumours/ The Telegraph (London)], here it is unpaywalled via MSN [https://www.msn.com/en-gb/news/world/ukraine-commander-valeriy-zaluzhnyi-appears-in-video-to-dispel-russian-reports-of-his-death/ar-AA1bHl38?li=BBoPWjQ]. [[User:AncientWalrus|AncientWalrus]] ([[User talk:AncientWalrus|talk]]) 06:38, 30 May 2023 (UTC)

== Transitional Sword of the Queen of Great Britain ==

He was awarded this? What in earth IS this? More info will help the article. [[Special:Contributions/2601:647:5800:9120:FC10:37B9:E330:BF6E|2601:647:5800:9120:FC10:37B9:E330:BF6E]] ([[User talk:2601:647:5800:9120:FC10:37B9:E330:BF6E|talk]]) 05:04, 19 May 2023 (UTC)

:There is no such award. I have removed this claim. [[Special:Contributions/78.150.88.107|78.150.88.107]] ([[User talk:78.150.88.107|talk]]) 22:10, 19 May 2023 (UTC)

== And another one, Bandera again ==

https://kresy.pl/wydarzenia/replika-wyszywanki-stepana-bandery-dla-glownodowodzacego-ukrainskiej-armii/ again and again Bandera, new Nazi cases coming every few months — Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Leocadii|Leocadii]] ([[User talk:Leocadii#top|talk]] • [[Special:Contributions/Leocadii|contribs]]) 19:12, 20 May 2023 (UTC) 

== Removing external video as not clear why useful ==

I don't see why we need 4 external links to videos at the bottom. I've therefore undone this edit. Happy to be convinced why this would be neccessary, but the edit summary doesn't mention. This is the [https://en.wikipedia.org/w/index.php?title=Valerii_Zaluzhnyi&diff=prev&oldid=1154554944 edit] I mean by [[User:Максим_Огородник]]. [[User:AncientWalrus|AncientWalrus]] ([[User talk:AncientWalrus|talk]]) 16:04, 22 May 2023 (UTC)

:<s>Oh also this page is under [[WP:GS/RUSUKR]] where only extended confirmed users may edit (reverts are not edit warring) [[User:AncientWalrus|AncientWalrus]] ([[User talk:AncientWalrus|talk]]) 19:54, 22 May 2023 (UTC)</s> User is extended confirmed so the sanction doesn't apply, I will undo my undo as I am not extended confirmed myself and hence am not allowed to undo

== Pro Russian sources ==

are stating that Gen. Zaluzhnyi is badly wounded with a head injury and is in a more-or-less vegetative state. It will be interesting to see how this bit of propaganda plays out. [[User:Carptrash|Carptrash]] ([[User talk:Carptrash|talk]]) 15:56, 25 May 2023 (UTC)

and Ukrainian and Western propaganda is either silent or claims that he is doing great — Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/86.111.119.54|86.111.119.54]] ([[User talk:86.111.119.54#top|talk]]) 17:06, 25 May 2023 (UTC) 

== Extended-confirmed-protected edit request on 25 May 2023 ==

{{edit extended-protected|Valerii Zaluzhnyi|answered=yes}}
Add to biography: In May 2023, Russian propaganda falsely claimed Zaluzhnyi was killed in an airstrike, Zaluzhnyi himself refuted this claim in a video released on the 25th of may, in which he thanked the Ukrainian people and proclaimed they will win. [[Special:Contributions/2A02:1811:D581:0:F4E8:5FF6:84DB:E4BC|2A02:1811:D581:0:F4E8:5FF6:84DB:E4BC]] ([[User talk:2A02:1811:D581:0:F4E8:5FF6:84DB:E4BC|talk]]) 17:33, 25 May 2023 (UTC)
:[[File:Red information icon with gradient background.svg|20px|link=|alt=]] '''Not done:''' please provide [[Wikipedia:Reliable sources|reliable sources]] that support the change you want to be made. – [[User:Jonesey95|Jonesey95]] ([[User talk:Jonesey95|talk]]) 17:39, 25 May 2023 (UTC)
::Yes, a link to the video would be good. [[User:Carptrash|Carptrash]] ([[User talk:Carptrash|talk]]) 01:41, 26 May 2023 (UTC)
::This is already being discussed higher up in section "Unconfirmed reports" where I posted links to more or less reliable sources discussing this topic. [[User:AncientWalrus|AncientWalrus]] ([[User talk:AncientWalrus|talk]]) 07:56, 26 May 2023 (UTC)
:::The more reliable referred to Le Monde @[[User:Carptrash|Carptrash]] [[User:AncientWalrus|AncientWalrus]] ([[User talk:AncientWalrus|talk]]) 10:21, 27 May 2023 (UTC)
::::Thanks, and can you please drop me a line when Zaluzhnyi actually shows up? [[User:Carptrash|Carptrash]] ([[User talk:Carptrash|talk]]) 15:28, 27 May 2023 (UTC)
:::::Also, {{ping|AncientWalrus}}, I have not used much French since high school (1968) but could not find this story in your link. Perhaps, since all the stories their are 5/22, you could mention which minute it appears in? Thanks again, [[User:Carptrash|Carptrash]] ([[User talk:Carptrash|talk]]) 15:41, 27 May 2023 (UTC)
::::::Here's a direct link, I was able to find it directly by Ctrl+F'ing for "Valer": [https://www.lemonde.fr/international/live/2023/05/22/guerre-en-ukraine-en-direct-des-civils-evacues-de-la-zone-ou-une-incursion-armee-est-en-cours-selon-le-gouverneur-de-la-region-russe-de-belgorod_6174298_3210.html?#id-964388]. The start reads as: {{tqb| Les Russes disent avoir tué ou blessé Valerii Fedorovych Zaluzhnyi sur les résaux sociaux ? Qu'en est-il ? Est-ce juste de la propagande ? Bonjour Boulip, Samedi, la vice-ministre ukrainienne de la défense, Hanna Maliar, a annoncé que « le commandant en chef [Valeri Zaloujny] est en place. Il fait son travail. Nous venons de lui parler », sur Telegram. Pour Mme Maliar, il s’agit d’une stratégie de désinformation voulue par la Russie au moment du « pic de Bakhmout » pour « démoraliser [les] troupes ».}} [[User:AncientWalrus|AncientWalrus]] ([[User talk:AncientWalrus|talk]]) 06:29, 30 May 2023 (UTC)
:::::::Des références sûres authentifiées pour ces informations ? D'ailleurs, qui est Mme Maliar ?
:::::::Visiblement cet article sent le propos outrancier pro-ukrainien, même si je compatis sincèrement avec le "petit" peuple ukrainien (si vous savez ce que c'est ?) pour ses souffrances mais certainement pas avec Zélensky comique troupier sorti du néant et corrompu avec ses multiples villas et ses dollars en millions ! [[Special:Contributions/88.163.124.35|88.163.124.35]] ([[User talk:88.163.124.35|talk]]) 07:47, 2 June 2023 (UTC)

== Extended-confirmed-protected edit request on 29 May 2023 ==

{{edit extended-protected|Valerii Zaluzhnyi|answered=yes}}
The following sentence in the article requires an edit: In January 2023, Zaluzhny received $1 million USD as an inheritance from an American-Ukrainian, Gregory Stepants.

Please correct "Stepants" to "Stepanets" [[User:Actura|Actura]] ([[User talk:Actura|talk]]) 23:54, 29 May 2023 (UTC)
: {{done}} [[User:Pppery|* Pppery *]] [[User talk:Pppery|it has begun...]] 02:29, 30 May 2023 (UTC)

Great Blizzard of 1888

2022-12-24T21:53:16Z

88.163.124.35: /* Further reading */Additionnal ref

{{short description|Severe snowstorm in the northeastern United States and Canada}}

{{about|the blizzard in the eastern United States and Canada|the blizzard in the Great Plains|Schoolhouse Blizzard}}
{{Infobox winter storm
| name = Great Blizzard of 1888
| image location = 10 PM March 12 surface analysis of Great Blizzard of 1888.png
| image name = [[surface weather analysis|Surface analysis]] of Blizzard on March 12, 1888 at 10 p.m.
| stormtype = [[Extratropical cyclone]] [[Blizzard]]
| duration =
| RSI =
| maximum amount = {{convert|58|in|cm|0}}
| pressure = {{convert|29|inHg|hPa|abbr=on|order=flip}}
| total damages (USD) = $25 million in 1888 (equivalent to ${{Inflation|US|25|1888|r=-1}} million in {{currentyear}})
| fatalities = 400 fatalities
| areas affected = [[Eastern United States]], [[Eastern Canada]]
}}

The '''Great Blizzard of 1888''', also known as the '''Great Blizzard of '88''' or the '''Great White Hurricane''' (March 11–14, 1888), was one of the most severe recorded [[blizzard]]s in American history. The storm paralyzed the [[East Coast of the United States|East Coast]] from the [[Chesapeake Bay]] to [[Maine]],<ref name=Christiano>{{cite web |url=http://www.nycsubway.org/articles/1888-blizzard.html |title=The Blizzard of 1888; the Impact of this Devastating Storm on New York Transit}}</ref><ref name= noaa/> as well as the [[Atlantic provinces]] of Canada.<ref name=douglas /> Snow fell from {{convert|10|to|58|in|cm}} in parts of [[New Jersey]], [[New York (state)|New York]], [[Massachusetts]], [[Rhode Island]], and [[Connecticut]], and sustained winds of more than {{convert|45|mph|km/h|0}} produced [[snowdrift]]s in excess of {{convert|50|ft|m}}. Railroads were shut down and people were confined to their homes for up to a week.<ref name=douglas>{{cite book | last = Douglas | first = Paul | title = Restless Skies | publisher = Barnes & Noble Publishing, Inc. | year = 2004 | pages = [https://archive.org/details/isbn_9780760761137/page/12 12–13] | isbn = 978-0-7607-6113-7 | url = https://archive.org/details/isbn_9780760761137/page/12 }}</ref> Railway and [[telegraph line]]s were disabled, and this provided the impetus to [[Undergrounding|move these pieces of infrastructure underground]]. Emergency services were also affected.

==Storm details==
[[File:Blizzard 1888 01.jpg|thumb|right|Streets in New York City as the storm hit. Many overhead wires broke and presented a hazard to city dwellers.<ref>{{cite web |title=Building the invisible city |publisher=Virtual New York |url=http://www.vny.cuny.edu/blizzard/building/building.html |access-date=2007-05-10}}</ref>]]
[[File:Brooklyn Bridge snowy.jpg|thumb|right|[[Brooklyn Bridge]] during the blizzard]]

The weather was unseasonably mild just before the blizzard, with heavy rains that turned to snow as temperatures dropped rapidly.<ref name=douglas /> On March 12, [[New York City]] dropped from {{convert|33|F|C}} to {{convert|8|F|C}}, and rain changed to snow at 1am.<ref name=wunderground>[https://www.wunderground.com/cat6/the-blizzard-of-1888-americas-greatest-snow-disaster The Blizzard of 1888: America’s Greatest Snow Disaster], Weather Underground, September 2, 2020</ref> The storm began in earnest shortly after midnight on March 12 and continued unabated for a full day and a half. In a 2007 article, the National Weather Service estimated that this [[nor'easter]] dumped as much as {{convert|50|in|cm}} of snow in parts of Connecticut and Massachusetts, while parts of New Jersey and New York had up to {{convert|40|in|cm}}.<ref name= noaa>{{cite web |url=http://www.crh.noaa.gov/mkx/climate/big.php |title=Biggest Snowstorms in the United States: From 1888 to Present |access-date=2007-12-21 |work=NWS Milwaukee/Sullivan, WI|archive-url=https://web.archive.org/web/20070324154647/http://www.crh.noaa.gov/mkx/climate/big.php|archive-date=24 March 2007|url-status=dead}}</ref> Most of northern Vermont received from {{convert|20|in|cm}} to {{convert|30|in|cm}}.<ref>{{cite web |url=http://www5.ncdc.noaa.gov/climatenormals/clim60/states/Clim_VT_01.pdf |title=Climate of Vermont |access-date=2007-12-21 |work=National Climatic Data Center |url-status=dead |archive-url=https://web.archive.org/web/20080229021750/http://www5.ncdc.noaa.gov/climatenormals/clim60/states/Clim_VT_01.pdf |archive-date=2008-02-29 }}</ref>

Drifts averaged {{convert|30|–|40|ft|m}}, over the tops of houses from New York to New England, with reports of drifts covering three-story houses. The highest drift was recorded in [[Gravesend, Brooklyn]] at {{convert|52|ft|m|disp=or}}. {{convert|58|in|cm}} of snow fell in [[Saratoga Springs, New York]]; {{convert|48|in|cm}} in [[Albany, New York]]; {{convert|45|in|cm}} in [[New Haven, Connecticut]]; and {{convert|22|in|cm}} in [[New York City]].<ref name=NCDC>{{cite web |url=http://www1.ncdc.noaa.gov/pub/data/blizzard/blizz.txt |title= The Big One! A Review of the March 12–14, 1993 "Storm of the Century" [With comparisons to the Blizzard of 1888] |access-date=2007-12-21 |work=National Climatic Data Center }}</ref> The storm also produced severe winds; {{convert|80|mph|km/h|0|abbr=|adj=off}} wind gusts were reported, although the highest official report in New York City was {{convert|40|mph|km/h|0}}, with a {{convert|54|mph|km/h|0|abbr=|adj=off}} gust reported at [[Block Island]].<ref name=NCDC/> On March 13, [[New York City]] recorded a low of {{convert|6|F|C}}, the coldest so late in the season, with the high rising to only {{convert|12|F|C}}.<ref name=wunderground/>

==Impacts==
In New York, neither rail nor road transport was possible anywhere for days,<ref name=Christiano/><ref>{{cite web |url=http://www.nycsubway.org/articles/1888-blizzard.html |title=The Blizzard of 1888; the Impact of this Devastating Storm on New York Transit}}</ref> and drifts across the [[New York, New Haven and Hartford Railroad|New York–New Haven rail line]] at [[Westport, Connecticut]], took [[New Haven Line#History|eight days]] to clear. Transportation gridlock as a result of the storm was partially responsible for the creation of the [[Massachusetts Bay Transportation Authority|first underground subway]] system in the United States, which opened nine years later in Boston.<ref>{{cite web |url=http://www.massmoments.com/moment.cfm?mid=77 |title=Blizzard shuts down Massachusetts |publisher=Massachusetts Foundation for the Humanities |quote=Perhaps the most important legacy of the Blizzard of 1888 was the Boston subway system. Alarmed by the paralysis and economic damage the storm caused, Boston decided to build a subway.}}</ref><ref>{{cite web |url=http://www.nycsubway.org/articles/1888-blizzard.html |title=The Blizzard of 1888; the Impact of this Devastating Storm on New York Transit |quote=There is no overstating the significant impact this tragedy had on the metropolis, especially on transportation. The resulting standstill on the elevated lines resulted in the city adopting a plan to build subways.}}</ref> The [[New York Stock Exchange]] was closed for two days.<ref>{{cite web|title=NEW YORK STOCK EXCHANGE SPECIAL CLOSINGS, 1885–date |url=https://www.nyse.com/pdfs/closings.pdf |url-status=dead |archive-url=https://web.archive.org/web/20070925210452/http://www.nyse.com/pdfs/closings.pdf |archive-date=2007-09-25 }}</ref> A full two day closure would not occur again until [[Hurricane Sandy]] in 2012.<ref>{{cite news |last1=Redden |first1=Molly |title=The New York Stock Exchange Has a Long History of Shutdowns |url=https://www.motherjones.com/politics/2015/07/new-york-stock-exchange-shutdown-history/ |access-date=November 17, 2022 |publisher=MotherJones}}</ref>

Similarly, telegraph [[infrastructure]] was disabled, isolating [[Montreal]] and most of the large northeastern U.S. cities from [[Washington, D.C.]] to Boston for days. Following the storm, New York began placing its telegraph and telephone infrastructure underground to prevent their destruction.

[[Fire station]]s were immobilized, and property loss from fire alone was estimated at $25 million (equivalent to ${{Inflation|US|25|1888|r=-1}} million in {{currentyear}}).<ref name=Christiano/>
The blizzard resulted in the founding of the [[Christman Bird and Wildlife Sanctuary]] located near [[Delanson, New York]].

From Chesapeake Bay through the [[New England]] area, more than 200 ships were either grounded or wrecked, resulting in the deaths of at least 100 seamen.<ref name=NCDC/> More than 400 people died from the storm and the ensuing cold, including 200 in New York City alone.<ref name=NCDC/><ref>{{cite web |url=http://www.crh.noaa.gov/iwx/program_areas/wxhisttdy/index.php?url=Mar12 |title=On Mar 12 in weather history |access-date=2007-12-21 |work=NWS Northern Indiana Weather History }}</ref> Efforts were made to push the snow into the Atlantic Ocean. Severe flooding occurred after the storm due to melting snow, especially in the [[Brooklyn]] area, which was susceptible to flooding because of its topography.<ref name=NCDC/>

Not all areas were notably affected by the Blizzard of 1888; an article in the ''Cambridge Press'' published five days after the storm noted that the "fall of snow in this vicinity was comparatively small, and had it not been accompanied by a strong wind it would have been regarded as rather trifling in amount, the total depth, on a level, not exceeding ten inches".<ref>[http://cambridge.dlconsulting.com/cgi-bin/cambridge?a=d&d=Press18880317-01.2.16&e=-------en-20--1--txt-txIN------ "The Great Storm"] ''Cambridge Press'', Cambridge, MA, 17 March 1888. Retrieved 29 November 2014.</ref>

[[Roscoe Conkling]], an influential [[Republican Party (United States)|Republican]] politician, died as a result of the storm.<ref>{{cite news |last=O'Grady |first=Jim |date=January 27, 2015 |title=Bad Idea: The Most Powerful Man in America Walks Home Through the Blizzard of 1888 |url=https://www.wnyc.org/story/bad-idea-most-powerful-man-america-walks-home-through-blizzard-1888/ |work=WNYC News |location=New York, NY}}</ref>

On 1 October 1888, an article appeared in the first issue of the [[National Geographic Society]] magazine about the great blizzard. It was written by [[Edward Everett Hayden]] and described the blizzard and the courageous and successful struggle, told by boat-keeper Robert Robinson, of the crew from the pilot-boat [[Charles H. Marshall (pilot boat)|''Charles H. Marshall, No. 3'']].<ref>{{cite web|url=https://www.gutenberg.org/files/49711/49711-h/49711-h.htm#chap5|title=The Great Storm Of March 11-14, 1888|work=Everett Hayden|date=|access-date=2020-12-14}}</ref>

==Pictures==
<gallery mode="packed" heights="150">
File:Blizzard 1888 Grand Central NY.jpg|45th Street and [[Grand Central Terminal|Grand Central Depot]], [[Manhattan]], March 12
File:Brooklyn blizzard 1888.jpg|Park Place in [[Brooklyn]], March 14
File:Brooklyn Museum - Blizzard of March 1888, Brooklyn - Breading G. Way - overall.jpg|Brooklyn children after the blizzard
File:StereoviewNewBritainCTGrandStMar131888BlizzardFWAllderige enh.jpg|[[New Britain, Connecticut]], March 13
File:Stebbins-11-Cythera.jpg|''Cythera'', lost with all aboard in the blizzard
File:Bone-valley-trail.jpg|Bone Valley Trail, where a herd of cattle froze
File:(King1893NYC) pg047 THE BLIZZARD OF MARCH 1888 (PHOTO BY LANGILL).jpg|14th Street, New York City, "just after the storm" (March 14)
</gallery>

==References==
{{reflist}}

==Further reading==
* {{cite news | title = In a Blizzard's Grasp | newspaper = [[The New York Times]] | date = March 13, 1888 | url = https://timesmachine.nytimes.com/timesmachine/1888/03/13/106317050.pdf | access-date = April 17, 2012 }}
* [http://librivox.org/national-geographic-magazine-vol-01-no-1-by-various/ "The Great Storm of March 11 to 14, 1888", ''National Geographic Magazine'', Vol. 1, No. 1, 1889 (audio)] Accessed April 17, 2012
* {{cite web |url=http://www.infoplease.com/spot/blizzard1.html |first=Borgna |last=Brunner |title=The Great White Hurricane" |website=infoplease.com |access-date=April 17, 2012}}
* {{cite web |url=http://www.nycsubway.org/articles/1888-blizzard.html |first=G. J. |last=Christiano |title=The Blizzard of 1888; the Impact of this Devastating Storm on New York Transit |website=nycsubway.org |access-date=April 17, 2012}}
* {{cite news |url=https://www.bostonglobe.com/metro/2019/03/11/been-years-since-great-white-hurricane-you-know-about/C9pjG4d5ia2nu72RwYFoQO/story.html |title=It's been 131 years since the Great White Hurricane. Do you know about it? |first=Breanne |last=Kovatch |newspaper=[[The Boston Globe]] |url-access=limited |date=March 11, 2019 |access-date=March 12, 2019}}
* {{cite book|last1=Martí|first1=José|author-link=José Martí|editor1-last=Lopate|editor1-first=Phillip|title=Writing New York: A Literary Anthology|date=2000|publisher=Washington Square Press|location=New York|isbn=9780671042356|pages=[https://archive.org/details/writingnewyorkli0000unse_w2z6/page/271 271–277]|edition=Paperback|chapter-url=https://books.google.com/books?id=mQnTQjSS5qEC&pg=PA271|access-date=26 January 2015|chapter=New York Under the Snow|ref=none|url=https://archive.org/details/writingnewyorkli0000unse_w2z6/page/271}}
* {{cite book |title=Blizzard!: The Storm That Changed America |last=Murphy |first=Jim |year=2006 |publisher=Scholastic |isbn=978-0-590-67310-5 |url=https://archive.org/details/blizzard00jimm }}
* {{cite book |title=The children's blizzard |last=Laskin |first=David |year=2004 |publisher=Harper Perennial |isbn=978-0-06-052076-2 }}

==External links==
{{Commons category|Great Blizzard of 1888}}
* [http://www.erh.noaa.gov/aly/Past/WINTER.htm NOAA: Major winter storms] Accessed April 17, 2012
* [http://usasearch.gov/search?v%3Aproject=firstgov-noaa-images&query=blizzard+1888 Blizzard 1888, US Government images]{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }} Accessed April 17, 2012
* [https://web.archive.org/web/20090428171243/http://nsidc.org/snow/shovel.html National Snow and Ice Data Center: "Have Snow Shovel, Will Travel"] Accessed April 17, 2012
* http://cslib.cdmhost.com/cdm/landingpage/collection/p15019coll17 {{Webarchive|url=https://web.archive.org/web/20121102221833/http://cslib.cdmhost.com/cdm/landingpage/collection/p15019coll17 |date=2012-11-02 }} Connecticut State Library Blizzard of 1888 Photographic Collection

{{United States winter storms}}

[[Category:Blizzards in the United States|1888-3]]
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[[Category:1888 meteorology]]
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Budapest Memorandum

2022-12-23T15:26:23Z

88.163.124.35: /* Analysis */clarity and examplarity

{{Short description|1994 OSCE conference agreements}}
{{Use dmy dates|date=December 2020}}
{{Infobox treaty
| name = Budapest Memorandum on Security Assurances
| long_name = Memorandum on Security Assurances in connection with the Republic of Belarus'/Republic of Kazakhstan's/Ukraine's accession to the [[Treaty on the Non-Proliferation of Nuclear Weapons]]
| image = Presidents after signing the Trilateral Statement, Moscow, 1994.png
| image_width = 
| image_alt = 
| caption = U.S. [[Bill Clinton|President Clinton]], Russian [[Boris Yeltsin|President Yeltsin]], and Ukrainian [[leonid Kravchuk|President Kravchuk]] after signing the Trilateral Statement in Moscow on 14 January 1994
| type =
| context =
| date_drafted =
| date_signed = {{Start date|df=yes|1994|12|5}}
| location_signed = [[Budapest]], [[Hungary]]
| date_sealed =
| date_effective =
| condition_effective =
| date_expiration = 
| date_expiry = 
| mediators = 
| negotiators = 
| original_signatories =
* {{flag|Belarus|1991}}
* {{flag|Kazakhstan}}
* {{flag|Ukraine}}
* {{flag|Russia}}
* {{flag|United States}}
* {{flag|United Kingdom}}
| signatories = 
| parties = 
| ratifiers = 
| depositor = 
| depositories = 
| citations = 
| languages =
* [[English language]]
* [[Russian language]]
* [[Ukrainian language]] (Ukraine Memorandum)
* [[Belarusian language]] (Belarus Memorandum)
* [[Kazakh language]] (Kazakhstan Memorandum)
| wikisource1 = Ukraine. Memorandum on Security Assurances
| wikisource2 = Memorandum on Security Assurances in connection with the Republic of Kazakhstan's accession to the Treaty on the Non-Proliferation of Nuclear Weapons
| wikisource3 = Memorandum on Security Assurances in connection with the Republic of Belarus' accession to the Treaty on the Non-Proliferation of Nuclear Weapons

| footnotes =
}}

The '''Budapest Memorandum on Security Assurances''' comprises three substantially identical political agreements signed at the [[Organization for Security and Co-operation in Europe|OSCE]] conference in [[Budapest]], [[Hungary]], on 5 December 1994, to provide security assurances by its signatories relating to the accession of [[Belarus]], [[Kazakhstan]] and [[Ukraine]] to the [[Treaty on the Non-Proliferation of Nuclear Weapons]] (NPT). The three memoranda were originally signed by three nuclear powers: the [[Russian Federation]], the [[United Kingdom]] and the [[United States]]. [[China]] and [[France]] gave somewhat weaker individual assurances in separate documents.<ref name=vasylenko-20091215>{{cite news|last=Vasylenko|first=Volodymyr|date=15 December 2009|url=http://www.day.kiev.ua/en/article/close/assurances-without-guarantees-shelved-document |title=On assurances without guarantees in a 'shelved document'|newspaper=The Day|access-date=7 March 2022}}</ref>

The memoranda, signed in Patria Hall at the [[Budapest Convention Center]] with US Ambassador [[Donald M. Blinken]] amongst others in attendance,<ref name="bubba">{{cite news |title=1994 Public Papers 2146 - Remarks at the Denuclearization Agreements Signing Ceremony in Budapest |url=https://www.govinfo.gov/app/details/PPP-1994-book2/PPP-1994-book2-doc-pg2146 |publisher=Public Papers of the Presidents of the United States: William J. Clinton (1994, Book II) |date=5 December 1994}}</ref> prohibited the Russian Federation, the United Kingdom and the United States from threatening or using military force or economic coercion against Ukraine, Belarus, and Kazakhstan, "except in self-defence or otherwise in accordance with the [[Charter of the United Nations]]." As a result of other agreements and the memorandum, between 1993 and 1996, Belarus, Kazakhstan and Ukraine gave up their nuclear weapons.<ref name=harahan-2014>{{cite web |pages=101–134,186 |last=Harahan |first=Joseph P. |date=2014 |url=https://www.dtra.mil/Portals/61/Documents/History/With%20Courage%20and%20Persistence%20CTR.pdf?ver=2016-05-09-102902-893 |url-status=dead |title=With Courage and Persistence: Eliminating and Securing Weapons of Mass Destruction with the Nunn-Lugar Cooperative Threat Reduction Programs |work=DTRA History Series |publisher=Defense Threat Reduction Agency |asin=B01LYEJ56H |archive-url=https://web.archive.org/web/20220228153820/https://www.dtra.mil/Portals/61/Documents/History/With%20Courage%20and%20Persistence%20CTR.pdf?ver=2016-05-09-102902-893 |archive-date=28 February 2022 |access-date=7 March 2022}}</ref><ref name="bmemo">{{cite news |title=Memorandum on security assurances in connection with Ukraine's accession to the Treaty on the Non-Proliferation of Nuclear Weapons |url=https://treaties.un.org/Pages/showDetails.aspx?objid=0800000280401fbb |publisher=treaties.un.org |date=5 December 1994}}</ref>

==Content==
According to the three memoranda,<ref>{{cite web |url=http://www.cfr.org/nonproliferation-arms-control-and-disarmament/budapest-memorandums-security-assurances-1994/p32484 |title=Budapest Memorandums on Security Assurances, 1994 - Council on Foreign Relations |publisher=Cfr.org |date=5 December 1994 |access-date=7 March 2017 |archive-url=https://web.archive.org/web/20170312052208/http://www.cfr.org/nonproliferation-arms-control-and-disarmament/budapest-memorandums-security-assurances-1994/p32484 |archive-date=12 March 2017 |url-status=dead}}</ref> Russia, the US and the UK confirmed their recognition of Belarus, Kazakhstan and Ukraine becoming parties to the [[Treaty on the Non-Proliferation of Nuclear Weapons]] and effectively abandoning their nuclear arsenal to Russia and that they agreed to the following:

# Respect the signatory's independence and sovereignty in the existing borders.<ref>{{cite web|title=Joint Declaration of the Leaders of Ukraine, Russia, the United Kingdom of Great Britain and Northern Ireland, and the United States of America, as well as a Memorandum on Security Assurances in Connection with Ukraine's Accession to the Non-Proliferation Treaty, signed in Budapest on 5 December 1994|url=https://undocs.org/CD/1285|website=undocs.org|publisher=United Nations|access-date=19 March 2017|id=CD/1285 |language=en|date=21 December 1994}}</ref>
# Refrain from the threat or the use of force against the signatory.
# Refrain from economic coercion designed to subordinate to their own interest the exercise by the signatory of the rights inherent in its sovereignty and thus to secure advantages of any kind.
# Seek immediate [[Security Council]] action to provide assistance to the signatory if they "should become a victim of an act of aggression or an object of a threat of aggression in which nuclear weapons are used".
# Refrain from the use of nuclear arms against the signatory.
# Consult with one another if questions arise regarding those commitments.<ref name="A/49/765">{{cite web|url=http://dag.un.org/bitstream/handle/11176/44537/A_49_765%3bS_1994_1399-EN.pdf?sequence=21&isAllowed=y|title=Letter dated 94/12/07 from the Permanent Representative of the Russian Federation, Ukraine, the United Kingdom of Great Britain and Northern Ireland and the United States of America to the United Nations addressed to the Secretary-General|hdl=11176/44537|publisher=[[United Nations]]|id=A/49/765; S/1994/1399|date=19 December 1994|access-date=27 February 2017|archive-url=https://web.archive.org/web/20171019081043/http://dag.un.org/bitstream/handle/11176/44537/A_49_765%3bS_1994_1399-EN.pdf?sequence=21&isAllowed=y|archive-date=19 October 2017|url-status=dead}}</ref><ref name=acw-20140429>{{cite news |url=http://lewis.armscontrolwonk.com/archive/7316/ukraine-and-the-1994-budapest-memorandum |title=Why Ukraine wasn't a nuclear power in the early 1990s and the West has no legal obligation to come to its aid now |author=Philipp Bleek |publisher=Arms Control Wonk |date=29 April 2014 |access-date=16 August 2014 |archive-url=https://web.archive.org/web/20140819085816/http://lewis.armscontrolwonk.com/archive/7316/ukraine-and-the-1994-budapest-memorandum |archive-date=19 August 2014 |url-status=dead}}</ref>

==History==
Until Ukraine gave up the Soviet nuclear weapons stationed on its soil, it had the world's [[Nuclear weapons and Ukraine|third-largest nuclear weapons stockpile]],<ref name="flashpoint">{{cite web|last=Kuzio|first=Taras|author-link=Taras Kuzio|url=http://www.taraskuzio.net/media13_files/30.pdf|title=The Crimea: Europe's Next Flashpoint|date=November 2010|url-status=dead|archive-url=https://web.archive.org/web/20140309221523/http://www.taraskuzio.net/media13_files/30.pdf|archive-date=9 March 2014}}</ref><ref name="cfr">{{cite web|url=http://www.cfr.org/arms-control-disarmament-and-nonproliferation/budapest-memorandums-security-assurances-1994/p32484|title=Budapest Memorandums on Security Assurances, 1994|work=Council on Foreign Relations|date=5 December 1994|access-date=2 March 2014|archive-url=https://web.archive.org/web/20140317182201/http://www.cfr.org/arms-control-disarmament-and-nonproliferation/budapest-memorandums-security-assurances-1994/p32484|archive-date=17 March 2014|url-status=dead}}</ref> of which Ukraine had physical but no operational control. Russia controlled the codes needed to operate the nuclear weapons through electronic [[Permissive Action Link]]s and the Russian command and control system, although this could not be sufficient guarantee against Ukrainian access.<ref name=martel-1998>{{cite book|first=William C.|last=Martel|author-link=William C. Martel|url=https://books.google.com/books?id=MNanc3lYUsQC|chapter=Why Ukraine gave up nuclear weapons: non-proliferation incentives and disincentives|pages=88–104|title=Pulling Back from the Nuclear Brink: Reducing and Countering Nuclear Threats|editor1=Barry R. Schneider|editor2=William L. Dowdy|publisher=Psychology Press|year=1998|isbn=9780714648569|access-date=6 August 2014|quote=There are some reports that Ukraine had established effective custody, but not operational control, of the cruise missiles and gravity bombs. ... By early 1994 the only barrier to Ukraine's ability to exercise full operational control over the nuclear weapons on missiles and bombers deployed on its soil was its inability to circumvent Russian permissive action links (PALs).}}</ref><ref name=pikayev-1994>{{cite journal |last=Pikayev|first=Alexander A. |url=http://cns.miis.edu/npr/pdfs/pikaye13.pdf|title=Post-Soviet Russia and Ukraine: Who can push the Button? |journal=The Nonproliferation Review |volume=1 |issue=3 |date=Spring–Summer 1994 |doi=10.1080/10736709408436550 |access-date=6 August 2014 |pages=31,40–45 |quote=Ukrainian officials always underline that they provide purely administrative control over the strategic weapons, while the Russians provide 'operational' control. ... technical features themselves could not be considered a sufficient guarantee against Ukraine gaining unauthorized access to weapons.}}</ref> Formally, these weapons were controlled by the [[Commonwealth of Independent States]].<ref name=hansard-19930622>{{cite news |url=https://publications.parliament.uk/pa/cm199293/cmhansrd/1993-06-22/Orals-1.html#Orals-1_sbhd1 |title=Nuclear Weapons |last=Hanley |first=Jeremy |publisher=UK Parliament |work=Hansard |date=June 22, 1993 |id=Column 154 |access-date=September 9, 2018 |quote=''The Minister of State for the Armed Forces (Mr. Jeremy Hanley):'' ... Some weapons are also possessed by Ukraine, Kazakhstan and Belarus, but these are controlled by the Commonwealth of Independent States.}}</ref><ref name=acw-20220224>{{cite AV media |url=https://www.armscontrolwonk.com/archive/1215097/deterrence-in-ukraine/ |title=Deterrence in Ukraine |last1=Lewis |first1=Jeffrey |last2=Stein |first2=Aaron |newspaper=Arms Control Wonk |author-link1=Jeffrey Lewis (academic) |date=24 February 2022 |access-date=28 February 2022 |time=3m13s-, 11m37s- |quote=''Jeffrey Lewis:'' Ukraine did not possess nuclear weapons after the collapse of the Soviet Union. They were not the third largest nuclear power. They did not give up those weapons because they did not possess them. ... The Rocket Forces pushed back and instead of taking the Ukrainian oath were able to arrange to take an oath to the Commonwealth of Independent States.}}</ref> Belarus only had mobile missile launchers, and Kazakhstan had chosen to quickly give up its nuclear warheads and missiles to Russia. Ukraine went through a period of internal debate on their approach.<ref name=harahan-2014/><ref name=pifer-201105>{{cite web |pages=5,7,10-13,21-24 |url=https://www.brookings.edu/wp-content/uploads/2016/06/05_trilateral_process_pifer.pdf |title=The Trilateral Process: The United States, Ukraine, Russia and Nuclear Weapons |last=Pifer |first=Steven |publisher=Brookings Institution |author-link1=Steven Pifer |id=Arms Control Series Paper 6 |date=May 2011 |access-date=1 March 2022}}</ref>

===Preliminaries===
On 23 May 1992, Russia, the U.S., Belarus, Kazakhstan and Ukraine signed the [[Lisbon Protocol]] to the [[START I]] treaty, ahead of ratifying the treaty later. The protocol committed Belarus, Kazakhstan and Ukraine to adhere to the NPT as non-nuclear weapons states as soon as possible. However, the terms for the transfer of the nuclear warheads were not agreed, and some Ukrainian officials and parliamentarians started to discuss the possibility of retaining some of the modern Ukrainian built [[RT-23 Molodets|RT-23]] (SS-24) missiles and Soviet built warheads.<ref name=pifer-201105/><ref name=aca-202012>{{cite web |url=https://www.armscontrol.org/node/3289 |title=The Lisbon Protocol At a Glance |last=Reif |first=Kingston |publisher=Arms Control Association |date=December 2020 |access-date=1 March 2022}}</ref>

In 1993, two regiments of [[UR-100N]] (SS-19) missiles in Ukraine were withdrawn to storage because warhead components were past their operational life, and Ukraine's political leadership realised that Ukraine could not become a credible nuclear military force as they could not maintain the warheads and ensure long term nuclear safety. Later in 1993, the Ukrainian and Russian governments signed a series of bilateral agreements giving up Ukrainian claims to the nuclear weapons and the [[Black Sea Fleet]], in return for $2.5 billion of gas and oil debt cancellation and future supplies of fuel for its [[Nuclear power in Ukraine|nuclear power reactors]]. Ukraine agreed to ratify the [[START I]] and NPT treaties promptly. This caused severe public criticism leading to the resignation of Ukrainian Defence Minister [[Kostyantyn Morozov|Morozov]].<ref name=harahan-2014/> On 18 November 1993, the [[Verkhovna Rada|Rada]] passed a motion agreeing to [[START I]] but renouncing the Lisbon Protocol, suggesting Ukraine would only decommission 36% of missile launchers and 42% of the warheads on its territory, and demanded financial compensation for the tactical nuclear weapons removed in 1992. This caused U.S. diplomatic consternation, and the following day Ukrainian President [[Leonid Kravchuk|Kravchuk]] said "we must get rid of [these nuclear weapons]. This is my viewpoint from which I have not and will not deviate." He then brought a new proposal to the Rada.<ref name=pifer-201105/><ref name=aca-202012/>

[[File:President Clinton's News Conference with President Yeltsin (1994).webm|thumb|right|300x300px|Yeltsin and Clinton news conference, 14 January 1994]]

On 15 December 1993, U.S. Vice President [[Al Gore]] visited Moscow for a meeting. Following side discussions, a U.S and Russian delegation, including U.S. Deputy Secretary of Defense [[William J. Perry]], flew to Ukraine to agree to the outlines of a trilateral agreement including U.S. assistance in dismantling the nuclear systems in Ukraine and compensation for the uranium in nuclear warheads. Participants were invited to Washington on 3–4 January to finalise the agreement. A Trilateral Statement with a detailed annex was agreed, based on the previously agreed terms but with detailed financial arrangements and a firm commitment to an early start to the transfer of at least 200 warheads to Russia and the production in Russia of nuclear reactor fuel for Ukraine. Warheads would be removed from all [[RT-23 Molodets|RT-23s]] (SS-24) within 10 months. However Ukraine did not want a commitment to transfer all warheads by 1 June 1996 to be made public for domestic political reasons, and Russia did not want the financial compensation for uranium made public concerned that Belarus and Kazakhstan would also demand this. It was decided to exclude these two matters from the published agreement, but cover them in private letters between the countries' presidents.

Another key point was that U.S. State Department lawyers made a distinction between "security guarantee" and "security assurance", referring to the security guarantees that were desired by Ukraine in exchange for non-proliferation. "Security guarantee" would have implied the use of military force in assisting its non-nuclear parties attacked by an aggressor (such as [[North_Atlantic_Treaty#Article_5|Article 5]] of the [[North Atlantic Treaty]] for [[NATO]] members) while "security assurance" would simply specify the non-violation of these parties' [[territorial integrity]]. In the end, a statement was read into the negotiation record that the (according to the U.S. lawyers) lesser sense of the English word "assurance" would be the sole implied translation for all appearances of both terms in all three language versions of the statement.<ref name=pifer-201105/>

President [[Bill Clinton|Clinton]] made a courtesy stop at [[Kyiv]] on his way to [[Moscow]] for the Trilateral Statement signing, only to discover Ukraine was having second thoughts about signing. Clinton told Kravchuk not signing would risk major damage to U.S.-Ukraine relations. After some minor rewording, the Trilateral Statement was signed by the three presidents in Moscow in front of the media on 14 January 1994.<ref name=pifer-201105/><ref name=hus-1996>{{cite journal |url=https://www.jstor.org/stable/41036699 |title=Trilateral Statement by the Presidents of the United States, Russia, Ukraine |journal=Harvard Ukrainian Studies |volume=20 |year=1996 |pages=313–316 |jstor=41036699 |access-date=1 March 2022}}</ref>

===The Budapest Memoranda===
[[File:Budapest Congress Centre by József Finta (1984). - Hungary.JPG|thumb|right|upright=1.4|On 5 December 1994 to sign the three documents the leaders of the seven nations gathered at the Budapest Congress Center, shown here in a photograph dated October 2015]]
{{external media| float = left | video1 = [https://www.c-span.org/video/?61971-1/presidential-return-hungary# "President Clinton arrived back at the White House by helicopter from a one-day trip to Budapest, Hungary"], [[C-SPAN]]}}
The fabled "Budapest Memorandum" is actually three documents signed individually on 5 December 1994 by the three leaders of the ex-Soviet nations, together with the guarantor nations: United States, United Kingdom and Russia. So the UNTERM portal notes for one: "To distinguish this from the other two Budapest Memorandums of the same date, this one could be referred to as the 'Budapest Memorandum regarding Kazakhstan{{'"}}.<ref name="unterm">{{cite news |title=Memorandum on Security Assurances in Connection with the Republic of Kazakhstan's Accession to the Treaty on the Non-Proliferation of Nuclear Weapons |url=https://untermportal.un.org/unterm/display/record/unhq/memorandum_on_security_assurances_in_connection_with_the_republic_of_kazakhstan/e3f3c6f0-504b-4935-b059-d91b1e462ae8 |publisher=UNTERM portal |date= }}</ref>

===Sequels===
{{wikisource portal|Remarks at the Denuclearization Agreements Signing Ceremony in Budapest}}
After this was agreed, the U.S. used its [[Nunn–Lugar Cooperative Threat Reduction]] programme to provide financial assistance over $300 million (equivalent to ${{Inflation|US|300|1994}} million in {{Inflation/year|US}}), and technical assistance in decommissioning the nuclear weapons and delivery systems, which took to 2008 to fully complete.<ref name=harahan-2014/> The U.S. also doubled other economic aid to Ukraine to $310 million (equivalent to ${{Inflation|US|310|1994}} million in {{Inflation/year|US}}) for 1994.<ref name=lat-19940111>{{cite news |url=https://www.latimes.com/archives/la-xpm-1994-01-11-mn-10675-story.html |title=Ukraine Agrees to Give Up Its Nuclear Arsenal, Clinton Says: Summit: President hails the accord as a breakthrough, but it faces parliamentary opposition. NATO endorses the U.S. 'Partnership for Peace' plan to broaden alliance. |last=Nelson |first=Jack |newspaper=Los Angeles Times |date=11 January 1994 |access-date=1 March 2022}}</ref>

In 2009, Russia and the United States released a joint statement that the memorandum's security assurances would still be respected after the expiration of the [[START Treaty]].<ref>{{Cite web|url=https://www.armscontrol.org/factsheets/Ukraine-Nuclear-Weapons|title=Ukraine, Nuclear Weapons, and Security Assurances at a Glance|publisher=[[Arms Control Association]]|website=ArmsControl.org|access-date=2019-03-14}}</ref>

====2013 Belarus sanctions====
In 2013, the government of Belarus complained that American sanctions against it were in breach of Article 3 of the Memorandum. The US government responded that its sanctions were targeted at combating human rights violations and other illicit activities of the government of Belarus and not the population of Belarus.<ref name=usembassy-20130412/>

====2014 Russian annexation of Crimea====
{{Further|Annexation of Crimea by the Russian Federation}}
In February 2014, Russian forces seized or blockaded various airports and other strategic sites throughout [[Crimea]].<ref>{{cite web|url=http://www.diplomaticourier.com/news/topics/politics/2187-political-legitimacy-and-international-law-in-crimea-pushing-the-u-s-and-russia-apart|title=Political Legitimacy and International Law in Crimea: Pushing the U.S. and Russia Apart|publisher=Diplomatic Courier|date=8 May 2014|access-date=9 May 2014|archive-url=https://web.archive.org/web/20140512063148/http://diplomaticourier.com/news/topics/politics/2187-political-legitimacy-and-international-law-in-crimea-pushing-the-u-s-and-russia-apart|archive-date=12 May 2014|url-status=dead}}</ref> The troops were attached to the Russian [[Black Sea Fleet]] stationed in Crimea,<ref>{{cite news|url=https://www.washingtonpost.com/world/ukraine-calls-russian-troops-invasion/2014/02/28/e066bfc8-a0be-11e3-878c-65222df220eb_story.html|title=Reports of Russian military activity in Crimea prompts stern warning from Obama|newspaper=The Washington Post|first1=William|last1=Booth|first2=Karen|last2=DeYoung|date=28 February 2014|access-date=1 March 2014}}</ref> which placed Russia in violation of the Budapest Memorandum. The Russian Foreign Ministry had confirmed the movement of armoured units attached to the Black Sea Fleet in Crimea but asserted that they were acting within the scope of the various agreements between the two countries.{{citation needed|date=December 2020}} Russia responded by supporting a referendum on whether the Crimea should join it. Crimea parliament announces referendum on the Autonomous republic's future in accordance with the law "On the Autonomous Republic of Crimea". On 16 March the referendum was held, on 17 March Crimea declared independence and on 21 March it was incorporated into the Russian Federation. Ukraine vigorously protested the action as a violation of Article 1 of the Budapest Memorandum.

After the [[Annexation of Crimea by the Russian Federation|annexation of Crimea]] by Russia in 2014, Canada,<ref name="CTV">{{cite news |first1=Corinne Ton |last1=That |first2=Christina |last2=Commisso |date=22 March 2014 |title=In Kyiv, Harper calls for 'complete reversal' of Crimea annexation |url=http://www.ctvnews.ca/politics/in-kyiv-harper-calls-for-complete-reversal-of-crimea-annexation-1.1740986 |publisher=CTV News}}</ref> France, Germany, Italy, Japan,<ref>{{cite news|first=Matthew |last=Fisher |url=http://news.nationalpost.com/2014/03/24/there-is-no-g8-russia-suspended-from-exclusive-club-until-it-changes-course-group-of-seven-nations-says/ |title=Russia suspended from G8 over annexation of Crimea, Group of Seven nations says |work=[[National Post]] |date=24 March 2014 |access-date=27 February 2017}}</ref> the UK,<ref>{{cite news |first1=Chris |last1=Stevenson |first2=Oscar |last2=Williams |date=1 March 2014 |title=Ukraine crisis: David Cameron joins Angela Merkel in expressing anxiety and warns that 'the world is watching' |url=https://www.independent.co.uk/news/uk/politics/ukraine-crisis-david-cameron-joins-angela-merkel-in-expressing-anxiety-and-warns-that-the-world-is-watching-9162830.html |work=The Independent}}</ref> and US<ref name="whitehouse">{{cite press release |title=Readout of President Obama's Call with President Putin |date=1 March 2014 |url=https://obamawhitehouse.archives.gov/the-press-office/2014/03/01/readout-president-obama-s-call-president-putin |via=[[NARA|National Archives]] |work=[[whitehouse.gov]] |access-date=26 March 2014}}</ref><ref name="washingtonpost">{{cite news |url=https://www.washingtonpost.com/opinions/condemnation-isnt-enough-for-russian-actions-in-crimea/2014/02/28/7b93b7c0-a09d-11e3-9ba6-800d1192d08b_story.html |title=Condemnation isn't enough for Russian actions in Crimea |newspaper=The Washington Post|date=28 February 2014}}</ref> [[Group of Eight#Russia's participation suspension (2014)|stated]] that Russian involvement was a breach of its Budapest Memorandum obligations to Ukraine and in violation of Ukrainian sovereignty and territorial integrity.

On 1 March the ''Address of the Verkhovna Rada of Ukraine to the Guarantor States in accordance with the Budapest Memorandum of 1994 on Security Assurances in connection with Ukraine's accession to the Treaty on the Non-Proliferation of Nuclear Weapons'' was published.<ref name="addvr">{{cite news |title=Address of the Verkhovna Rada of Ukraine to the Guarantor States in accordance with the Budapest Memorandum of 1994 on Security Assurances in connection with Ukraine's accession to the Treaty on the Non-Proliferation of Nuclear Weapons |url=https://uk.mfa.gov.ua/en/press-centr/3732-adress |publisher=Ministry of Foreign Affairs of Ukraine |date=1 March 2014}}</ref><ref>{{cite web|url=http://en.interfax.com.ua/news/general/193360.html|title=Ukrainian parliament appeals to Budapest Memorandum signatories|publisher=Interfax Ukraine|date=28 February 2014|access-date=1 March 2014}}</ref>

On 4 March the Russian president [[Vladimir Putin]] replied to a question on the violation of the Budapest Memorandum, describing the current [[2014 Ukrainian revolution|Ukrainian situation]] as a revolution: "a new state arises, but with this state and in respect to this state, we have not signed any obligatory documents".<ref>{{cite web|url=https://www.youtube.com/watch?v=ZwspcvY5kvg |archive-url=https://ghostarchive.org/varchive/youtube/20211220/ZwspcvY5kvg |archive-date=2021-12-20 |url-status=live|title=Putin at a press conference, 4 March 2014 (in Russian)|publisher=YouTube|date=4 March 2014|access-date=15 December 2016}}{{cbignore}}</ref> Russia stated that it had never been under obligation to "force any part of Ukraine's civilian population to stay in Ukraine against its will". Russia suggested that the US was in violation of the Budapest Memorandum and described the [[Euromaidan]] as a US-instigated coup.<ref>{{cite news|url=http://www.bbc.com/russian/rolling_news/2014/05/140520_rn_medvedev_ukraine.shtml|script-title=ru:Медведев: Россия не гарантирует целостность Украины|trans-title=Medvedev: Russia does not guarantee the integrity of Ukraine|language=ru|publisher=bbc.com|date=20 May 2014|access-date=27 February 2017}}</ref>

[[File:U.S. Secretary of State John Kerry speaks with British Foreign Secretary William Hague and Ukrainian Foreign Minister Andrii Deshchytsia.jpg|thumbnail|US Secretary of State [[John Kerry]] speaks with British Foreign Secretary [[William Hague]] and Ukrainian Foreign Minister [[Andrii Deshchytsia]] after hosting the Budapest Memorandum Ministerial on the Ukraine crisis in Paris, France, on 5 March 2014.]]

On 24 March 2014, Canadian Prime Minister [[Stephen Harper]] led the [[G7]] partners in an ''ad hoc'' meeting during the [[2014 Nuclear Security Summit|Nuclear Security Summit]], at [[The Hague]], for a partial suspension of Russian membership from the G8 due to Russia's breach of the Budapest Memorandum. He said that Ukraine had given up its nuclear weapons "on the basis of an explicit Russian assurance of its territorial integrity. By breaching that assurance, President Putin has provided a rationale for those elsewhere who needed little more than that already furnished by pride or grievance to arm themselves to the teeth." Harper also indicated support for Ukraine by saying he would work with the new Ukrainian government towards a [[free trade agreement]].<ref>{{cite news|first1=Steven|last1=Chase|first2=Mark |last2=MacKinnon|url=https://www.theglobeandmail.com/news/politics/harper-leads-charge-to-expel-russia-from-g8-ramp-up-sanctions/article17631725/|title=Harper leads charge to expel Russia from G8, ramp up sanctions|newspaper=[[The Globe and Mail]]|date=24 March 2014|access-date=27 February 2017}}</ref>

In February 2016, [[Sergey Lavrov]] claimed, "Russia never violated Budapest memorandum. It contained only one obligation, not to attack Ukraine with nukes."<ref>{{cite web | url=https://twitter.com/RussianEmbassy/status/692321689254830080 | title=Lavrov: Russia never violated Budapest memorandum | publisher=Russian Embassy in United Kingdom | date=2016-01-27 | access-date=2016-01-27}}</ref> However, Canadian journalist Michael Colborne pointed out that "there are actually six obligations in the Budapest Memorandum, and the first of them is 'to respect the independence and sovereignty and the existing borders of Ukraine'". Colborne also pointed out that a broadcast of Lavrov's claim on the [[Twitter]] account of Russia's embassy in the United Kingdom actually "provided a link to the text of the Budapest Memorandum itself with all six obligations, including the ones Russia has clearly violated – right there for everyone to see." [[Steven Pifer]], an American diplomat who was involved in drafting the Budapest Memorandum, later commented on "the mendacity of Russian diplomacy and its contempt for international opinion when the foreign minister says something that can be proven wrong with less than 30 seconds of [[Google]] fact-checking?"<ref>{{cite news |url=https://nationalpost.com/opinion/michael-colborne-russias-bald-faced-lies |title=Russia's bald-faced lies |first=Michael |last=Colborne |work=[[National Post]] |date=4 February 2016}}</ref> Russia argued that the United States broke the third point of the agreement by introducing and threatening further sanctions against the Yanukovych government.

On 20 April 2016, Ukraine established the [[Ministry of Reintegration of Temporarily Occupied Territories]],<ref name=NMC20416>{{cite news |language=uk |url=http://www.pravda.com.ua/news/2016/04/20/7106169/ |title=У Гройсмана створили нове міністерство |trans-title=Groisman created a new ministry |work=[[Ukrayinska Pravda]] |date=20 April 2016}}</ref> to manage occupied parts of the [[temporarily occupied and uncontrolled territories of Ukraine (2014-present)|Donetsk, Luhansk and Crimea]] regions, which are affected by Russian military intervention of 2014.

====Kerch Strait incident====
{{main|Kerch Strait incident}}
On 25 November 2018, the [[Russia]]n [[Federal Security Service]] (FSB) [[Coast Guard (Russia)|coast guard]] fired upon and captured three [[Ukrainian Navy]] vessels after they attempted to transit from the [[Black Sea]] into the [[Sea of Azov]] through the Kerch Strait on their way to the port of [[Mariupol]].<ref>{{cite news|url=https://www.bbc.com/news/world-europe-46338671|title=Tension escalates after Russia seizes Ukraine naval ships|date=26 November 2018|work=BBC News|access-date=26 November 2018|archive-date=26 November 2018|archive-url=https://web.archive.org/web/20181126095932/https://www.bbc.com/news/world-europe-46338671|url-status=live}}</ref><ref name="Osborn-Polityuk">{{cite news|url=https://www.reuters.com/article/us-ukraine-crisis-russia/russia-blocks-ukrainian-navy-from-entering-sea-of-azov-idUSKCN1NU0DL|title=Russia seizes Ukrainian ships near annexed Crimea after firing on them|first1=Andrew|last1=Osborn|first2=Pavel|last2=Polityuk|work=[[Reuters]]|date=25 November 2018|access-date=26 November 2018|archive-date=26 November 2018|archive-url=https://web.archive.org/web/20181126005901/https://www.reuters.com/article/us-ukraine-crisis-russia/russia-blocks-ukrainian-navy-from-entering-sea-of-azov-idUSKCN1NU0DL|url-status=live}}</ref>
On 27 November 2018, the [[Ministry of Foreign Affairs (Ukraine)|Ministry of Foreign Affairs of Ukraine]] appealed to the signatory states of the Budapest Memorandum to hold urgent consultations to ensure full compliance with the memorandum's commitments and the immediate cessation of Russian aggression against Ukraine.<ref>{{cite web |url=http://uprom.info/news/vpk/ukrayina-sklikaye-zustrich-yadernih-derzhav/ |title=Україна скликає зустріч ядерних держав |trans-title=Ukraine convenes a meeting of nuclear states |date=2018-12-05 |website=uprom.info |access-date=2018-12-05}}</ref><ref>{{cite web |url=https://www.eurointegration.com.ua/news/2018/12/5/7090281/ |title=Україна скликає зустріч ядерних держав за механізмом Будапештського меморандуму |trans-title=Ukraine convenes a meeting of nuclear states under the mechanism of the Budapest Memorandum |author= |date=2018-12-05 |website=www.eurointegration.com.ua |publisher=[[Ukrayinska Pravda]] }}</ref><ref>{{cite web |url=https://mfa.gov.ua/ua/press-center/comments/9591-zajava-mzs-ukrajini-u-zvjazku-zi-sklikannyam-konsulytacij-vidpovidno-do-budapeshtsykogo-memorandumu |title=Заява МЗС України у зв'язку зі скликанням консультацій відповідно до Будапештського меморандуму |trans-title=Statement of the Ministry of Foreign Affairs of Ukraine in connection with the convening of consultations in accordance with the Budapest Memorandum |author= |date=2018-12-05 |website=mfa.gov.ua |publisher=[[Ministry of Foreign Affairs (Ukraine)|Ministry of Foreign Affairs of Ukraine]] }}</ref>

====2022 Russian invasion of Ukraine====
{{Main|2022 Russian invasion of Ukraine|Legality of the 2022 Russian invasion of Ukraine}}
Ukrainian President [[Volodymyr Zelenskyy]] has publicly commented on the Budapest Memorandum by arguing that it provides no true guarantee of safety due to Russia's coercive power. On 19 February 2022, Zelenskyy made a speech at the [[Munich Security Conference]] in which he said "Since 2014, Ukraine has tried three times to convene consultations with the guarantor states of the Budapest Memorandum [i.e. [[United States]] and [[United Kingdom]]]. Three times without success. Today Ukraine will do it for the fourth time. ... If they do not happen again or their results do not guarantee security for our country, Ukraine will have every right to believe that the Budapest Memorandum is not working and all the package decisions of 1994 are in doubt."<ref>{{cite web|publisher=[[Kyiv Post]]|url=https://kyivindependent.com/national/zelenskys-full-speech-at-munich-security-conference/|title=Zelensky's full speech at Munich Security Conference|date=2022-02-19|access-date=2022-03-03}}</ref> Putin used Zelenskyy's comments as part of his claims that Ukraine could develop nuclear weapons. Critics have disputed Putin's claims.<ref name="Putin 2/23/22 NY Times Nuclear Weapons">{{cite news |last=Sanger |first=David |date=2022-02-23 |title=Putin Spins a Conspiracy Theory That Ukraine Is on a Path to Nuclear Weapons |url=https://www.nytimes.com/2022/02/23/us/politics/putin-ukraine-nuclear-weapons.html |url-status=live |work=The New York Times |location=New York |archive-url=https://web.archive.org/web/20220224031358/https://www.nytimes.com/2022/02/23/us/politics/putin-ukraine-nuclear-weapons.html |archive-date=2022-02-23 |access-date=2022-02-23}}</ref> This treaty has since been violated by Russia at the outbreak of the [[2022 Russian invasion of Ukraine]].<ref name="budapestmemorandum15804369">[https://www.ctvnews.ca/mobile/world/what-is-the-budapest-memorandum-and-how-does-it-impact-the-current-crisis-in-ukraine-1.5804369 What is the Budapest Memorandum and how does it impact the current crisis in Ukraine?], [[CTV News]] (3 March 2022)</ref>

==Analysis==
Under the agreement, the signatories offered Ukraine "security assurances" in exchange for its adherence to the [[Treaty on the Non-Proliferation of Nuclear Weapons]]. The memorandum bundled together a set of assurances that Ukraine had already held from the [[Conference on Security and Co-operation in Europe]] (CSCE) Final Act, the [[United Nations Charter]] and the [[Non-Proliferation Treaty]]<ref name=vasylenko-20091215/> but the Ukrainian government found it valuable to have these assurances in a Ukraine-specific document.<ref name="Ukraine-Crisis-France24">[http://www.france24.com/en/20140303-ukraine-us-uk-diplomacy-russia-budapest-memorandum/ "Are the US and the UK bound to intervene in Ukraine?"] {{Webarchive|url=https://web.archive.org/web/20171019080737/http://www.france24.com/en/20140303-ukraine-us-uk-diplomacy-russia-budapest-memorandum |date=19 October 2017 }}, [[france24]], 3 March 2014</ref><ref name=cnn-20140304>{{cite news |url=http://edition.cnn.com/2014/03/04/opinion/pifer-ukraine-budapest-memorandum/ |title=Ukraine crisis' impact on nuclear weapons |author=Steven Pifer |author-link=Steven Pifer |publisher=CNN |date=4 March 2014 |access-date=6 March 2014}}</ref>

The Budapest Memorandum was negotiated at political level, but it is not entirely clear whether the instrument is devoid entirely of legal provisions. It refers to assurances, but unlike guarantees, it does not impose a legal obligation of military assistance on its parties.<ref name=vasylenko-20091215/><ref name=cnn-20140304/> According to Stephen MacFarlane, a professor of international relations, "It gives signatories justification if they take action, but it does not force anyone to act in Ukraine."<ref name="Ukraine-Crisis-France24"/> In the US, neither the [[George H. W. Bush administration]] nor the [[Clinton administration]] was prepared to give a military commitment to Ukraine, and they did not believe the [[US Senate]] would ratify an [[international treaty]] and so the memorandum was adopted in more limited terms.<ref name=cnn-20140304/> The memorandum has a requirement of consultation among the parties "in the event a situation arises that raises a question concerning the ... commitments" set out in the memorandum.<ref>Budapest Memorandum, paragraph 6.</ref> Whether or not the memorandum sets out legal obligations, the difficulties that Ukraine has encountered since early 2014 may cast doubt on the credibility of future security assurances that are offered in exchange for nonproliferation commitments.<ref>{{cite web|url=https://www.ejiltalk.org/the-budapest-memorandum-and-beyond-have-the-western-parties-breached-a-legal-obligation/|website=EJIL: Talk!|title=The Budapest Memorandum and Beyond: Have the Western Parties Breached a Legal Obligation?|date=18 February 2015}}</ref> Regardless, the United States publicly maintains that "the Memorandum is not legally binding", calling it a "political commitment".<ref name=usembassy-20130412>{{cite press release |url=http://minsk.usembassy.gov/budapest_memorandum.html |title=Belarus: Budapest Memorandum |website=United States Embassy – Minsk |publisher=U.S. Department of State |date=12 April 2013 |archive-url=https://web.archive.org/web/20140419030507/http://minsk.usembassy.gov/budapest_memorandum.html |archive-date=19 April 2014}}</ref>

Ukrainian international law scholars such as Olexander Zadorozhny maintain that the Memorandum is an international treaty because it satisfies the criteria for one, as fixed by the 1969 [[Vienna Convention on the Law of Treaties]] (VCLT) and is "an international agreement concluded between States in written form and governed by international law".<ref>{{Cite journal|last=Zadorozhny|first=Olexander|date=2015|title=Russian Aggression against Ukraine, the annexation of the Crimean peninsula and the 1994 Budapest Memorandum|journal=European Political and Law Discourse}}</ref>

China and France gave security assurances for Ukraine in separate documents. China's governmental statement of 4 December 1994 did not call for mandatory consultations if questions arose but only for "fair consultations". France's declaration of 5 December 1994 did not mention consultations.<ref name=vasylenko-20091215/>

Scholars assumed at the time that Ukraine's decision to sign the Budapest Memorandum was proof of Ukraine's development as a democracy and its desire to step away from the post-Soviet world and make first steps toward a European future. For 20 years, until the [[Russo-Ukrainian War|2014 Russian military occupation of regions of Ukraine]],<ref name=Shymanska-20180301>{{cite news |url=https://trace.tennessee.edu/ijns/vol4/iss1/1/ |title=The 'Double Standard' of Nonproliferation: Regime Type and the U.S. Response to Nuclear Weapons Program |first=Alina |last=Shymanska |newspaper=International Journal of Nuclear Security |date=1 March 2018}}</ref> the Ukrainian nuclear disarmament was an exemplary case of nuclear non-proliferation as Monaco or Vatican.

==See also==
* [[2022 Russian invasion of Ukraine]]
* [[Minsk Agreement]]
* [[Normandy Format]]
* [[Nuclear weapons and Ukraine]]
* [[Russian military intervention in Ukraine (2014–present)]]
* [[Russian–Ukrainian Friendship Treaty]]

==References==
{{Reflist}}

==External links==
* [https://web.archive.org/web/20000419030507/https://treaties.un.org/doc/Publication/UNTS/Volume%202866/Part/volume-2866-I-50069.pdf Text of the Budapest Memorandum regarding Belarus] in the [[Treaty series#United Nations|United Nations Treaty Series]] {{in lang|be|en|ru|fr}}
* [http://unterm.un.org/DGAACS/unterm.nsf/8fa942046ff7601c85256983007ca4d8/d93b05adeda7271d85257b640074fb13 Text of Budapest Memorandum (Kazakhstan)]{{dead link|date=May 2022|bot=medic}}{{cbignore|bot=medic}}
* [https://treaties.un.org/doc/Publication/UNTS/Volume%203007/Part/volume-3007-I-52241.pdf Text of the Budapest Memorandum regarding Ukraine] in the United Nations Treaty Series {{in lang|en|ru|uk|fr}}
*{{Wikisourcelang-inline|en|Ukraine. Memorandum on Security Assurances|Text of the Budapest Memorandum (Ukraine)}}
*{{Wikisourcelang-inline|uk|Меморандум про гарантії безпеки у зв'язку з приєднанням України до Договору про нерозповсюдження ядерної зброї|Text of Budapest Memorandum|lang=uk}}
*[https://web.archive.org/web/20200529064610/https://zakon.rada.gov.ua/cgi-bin/laws/main.cgi?nreg=998_158 Text of Budapest Memorandum] {{in lang|uk}}
* ''[[Pavlo Hai-Nyzhnyk]]'' [https://web.archive.org/web/20170202040813/http://hai-nyzhnyk.in.ua/doc/2017doc.rosiya-proty-ukrainy.php Росія проти України (1990–2016 рр.): від політики шантажу і примусу до війни на поглинання та спроби знищення.] – К.: «МП Леся», 2017. – 332 с. {{ISBN|978-617-7530-02-1}}

{{Russian intervention in Ukraine}}
{{Annexation of Crimea by the Russian Federation}}
{{War in Donbas}}
{{Politics of Ukraine footer}}

[[Category:Treaties concluded in 1994]]
[[Category:Treaties entered into force in 1994]]
[[Category:Military history of Ukraine]]
[[Category:20th-century military history of Russia]]
[[Category:Nuclear proliferation]]
[[Category:Foreign relations of Belarus]]
[[Category:Foreign relations of Russia]]
[[Category:Foreign relations of Kazakhstan]]
[[Category:Foreign relations of the United Kingdom]]
[[Category:Foreign relations of the United States]]
[[Category:Foreign relations of Ukraine]]
[[Category:Ukraine–United Kingdom relations]]
[[Category:Russia–Ukraine relations]]
[[Category:Treaties of Belarus]]
[[Category:Treaties of Russia]]
[[Category:Treaties of Kazakhstan]]
[[Category:Treaties of the United Kingdom]]
[[Category:Treaties of the United States]]
[[Category:Treaties of Ukraine]]
[[Category:1994 in Belarus]]
[[Category:1994 in Ukraine]]
[[Category:1994 in Kazakhstan]]
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[[Category:1994 in British politics]]
[[Category:1994 in American politics]]
[[Category:Annexation of Crimea by the Russian Federation]]
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[[Category:December 1994 events in Europe]]
[[Category:Multilateral relations of Ukraine]]

Talk:Accounts Chamber of Russia

2022-11-30T13:50:24Z

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Talk:First strike (nuclear strategy)

2022-10-14T08:56:38Z

88.163.124.35: /* ... to be updated... */ new section

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==worth a mention? it's what we all think..==
is it worth mentioning that when the US was the only power to poses nuclear weapons it used them. And in the MAD era that followed, nobody used them. Which is probably why the US is finding it difficult to get people to disarm now?

I deleted peacekeeper as a counter first strike weapon, because it is really silly putting it as counter first strike considering it would not have survived first strike by SS-18 if one would be executed by USSR. Trident though is a good example, I don't know about Pershing, it is land based system too, with range of 1800 km, there is great doubt whether it would survive first strike by 5000 km range of SS-20 Pioneer. Some of the numbers are also wrong, CEPS in particular, for soviet system and for american. Also, what does Russel's opinion has to do with all these issues, especially considering his ignorant "west victory anyway" comments, Russell probably never talked to american CIA military analysts, who would disagree with his optimism and had no clue of what Red Army was. [[User:99.231.59.7|99.231.59.7]] 23:17, 9 October 2007 (UTC)Pavel. October 9, 2007.

Poorly written article, presents only western point of view. USSR's SS-18 was a perfect fisrst strike weapon, 8 warheads, each with 1.2 MT was more than capable of destroying Minuteman silos with one or two warheads. USSR's silos, SS-18's silos in particular, were fortified to withstand a direct nuclear strike.
[[User:74.98.216.68|74.98.216.68]] 02:32, 3 July 2007 (UTC)Pavel Golikov. July 2, 2007.

:It's worth mentioning that the last time nuclear weapons were used was during a world war. Quite likely the soviet union would have found uses for nuclear weapons in a world war as well.[[User:Driftwoodzebulin|Zebulin]] ([[User talk:Driftwoodzebulin|talk]]) 09:56, 27 November 2007 (UTC)

=='Wild Speculation"==

"In response, President Bush cited Hersh's reportage as "wild speculation"[4] but did not deny its veracity." - Is labelling something as 'wild speculation' not questioning its veracity?
:No, and questioning is not denying. What it means is that he won't deny or confirm it or discuss it at all. If later it came out that it was true, he wouldn't have lied about it.

== POV in History section ==

A paragraph in the History section reads:

"In the 1940s the US enjoyed a monopoly of nuclear forces, while in the late 1950s and early 1960s Khrushchev incautiously and inaccurately boasted of a Soviet superiority in missile forces. The arrival of Soviet missiles in Cuba was meant to weaken the US as it exposed the homeland to attack almost without warning, but instead exposed Khrushchev to personal humiliation as the "Cuban Missile Crisis" resulted in him backing down rather than risking war. During the crisis, Fidel Castro wrote Nikita Khrushchev a letter about the prospect that the US might follow an invasion of Cuba with a first strike against the USSR. The following quotation from the letter suggests to some writers that Castro was calling for a Soviet first strike against the US."

1. If it's going to say that Khrushchev was "inaccurately" boasting of Soviet missile superiority, then it must be referenced. Anyway, this claim is questionable -- there's considerable debate and until everything is declassified, we won't know for sure.

2. The line "instead exposed Khrushchev to personal humiliation" is at least POV; it's probably also an exaggeration. There was a bigger context to the Soviet placement of weapons in Cuba (not least, the American deployment of short range nuclear missiles in Turkey). This line should be removed or changed. --[[User:Rhombus|Rhombus]] 05:09, 12 March 2006 (UTC)

:I've altered that line to a somewhat more balanced view of what happened. I think part of the problem here is that the Soviets gave up their missiles in public, while the American agreement to remove missiles from Turkey was kept somewhat more secret, so it was perceived that the USSR backed down when in reality they were both giving up some of their bargaining chips.

== Other comments ==

Definition is WRONG! The concept of attacking MILITARY is VANITY and not logic. MAIN target is always FOOD and forests and it insulting that an OLD definition clearly wrong in this age is still here to be seen. 1st strike is not about hitting military or ability to strike back and easy can be for simple revenge or hate or spite and insanity. The 1st strike is NOT about Military as important but FOOD and FORESTS and the BILLIONS in starvation and 1 man does no care what [X] BILLION others might say or think or do! VANITY in the definition makes it completely wrong...one cares not about the military prepared and go for the crops and forests IGNORED due to this wrong definition? SO PLEASE CHANGE THE INCORRECT DEFINITION! I poison the food and burn the forests...what you ALL going to eat on the planet? Central Canada and USA all the way to the south Americas and Africa burns...you die in the hundreds of millions AT HOME! and inside of what? 3 months? ANY MILITARY EFFORT IN ANY WAY becomes MUTE! Damages are DONE and it is too late... MADMAN or WOMAN does not care what you do AFTER it is done. He or she does NOT have to like own people or even LIFE ITSELF! To assume military targets and ability to fight back....not very logical since the 1960's in my opinion. Nuke the food and forests...and not care what anyone thinks after is a very possible 1st strike concept when 1 human is in such power as to be able to use nukes that way and get mindless reactions from all under him or her. SO my point here is NOT Military ANYTHING has to do with 1st strikes in this age...it is even a avoided target if you got much more deadly easy ones..like food forests sea coast and giant lakes...silly to think reactions are important when insane people do not care what you do AFTER. SO please change the definition to reflect reality not 1945 logic. — Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/64.229.70.228|64.229.70.228]] ([[User talk:64.229.70.228#top|talk]]) 10:28, 1 March 2022 (UTC) 

Bertrand Russell said "better red than dead" and it got reversed by some American commentators during the Cold War.

:Interestingly, before the Soviets obtained atomic weapons, Bertrand Russell publically advocated a first strike on the USSR during a speech he gave to Westminster School (a famous educational establishment between Parliament and Westminster Abbey). His argument was that if both sides of the cold war had nuclear weapons the apocalypse was certain to come, whereas if one side destroyed the other utterly (which America theoretically had the chance to do, when it was the only nuclear power) then it would be a holocaust but not an apocalypse. This speech was witnessed by many pupils who went on to become prominent figures, including Nigel Lawson, who became the Chancellor of the Exchequer (Finance Minister) under Margaret Thatcher. I can cite sources for these, and in fact I'm going to add this to the article right now. Okay, I've added it, I've tried to keep it as balanced as possible because it's not totally clear whether Russell advocated actual First Strike, or just the public advocacy of First Strike as a diplomatic tool to force the Soviets to back down from Eastern Europe.

Also, first strike and assured destruction and madness of mad are so similar as to be hard topics to distinguish. Madness of mad was not just resource use but also the probability of error, communications or equipment failure, and other things that had nothing to do with intent to destroy each other - film War Games was a nice demonstration of this.

Linking the death penalty debate, terrorism debate, nuclear arms debate, as I did in assured destruction, is difficult, so the illustration of all three in advance of my next edit would probably improve "assured destruction" a lot - I would be summarizing rather than introducing the topic, with three examples...
----
Okay, but bear in mind that we are trying to create an encyclopedia here -- not just giving our own opinions about things.

Except for uncontroversial and generally accepted information, it's better to provide a source. Such as

*the Green Party believes that global warming is one of the biggest problems facing the world today.

or

*the [[WWF (wildlife)|WWF]] supports the [[Kyoto Treaty]] because a scientist reported a rising temperature trend in a recent scientific paper (please specify).

The goal is that a reader who disagrees with the '''position''' advocated will nevertheless agree that '''the article is correct''' because it accurately reports that X believes Y about Z. A reader might disagree about whether Y is true, so the article shouldn't say "Y is true" but rather "X believs Y is true".

[[User:Ed Poor]]

----
"NATO later explicitly ruled out a first-strike posture - a pledge not matched by the Soviets."

Completely untrue. The "no first strike" posture was first ever taken by the USSR in 1982 at special session of General Assembly of UN. This has not been matched by NATO throughout the Cold War (not sure about later, though.)

Egor.

==Castro letter==

*I said that if the second variant took place and the imperialists -- this was a very common word at that time -- invaded Cuba with the aim of occupying it, the Soviet Union must never allow a situation to develop in which the imperialists would launch the first nuclear strike. This was literally what I said, because I was absolutely convinced that if they invaded our country, this would create the grave risk for the Soviet Union of the U.S. taking the second step of carrying out a nuclear air strike against the Soviet Union. That's why I raised this question with Khrushchev as delicately as I could, saying that the Soviet Union must never allow a situation to develop in which the imperialists could launch the first nuclear strike -- because I was sure that after [an invasion], the second step would be for the Americans to launch a first nuclear strike against the Soviet Union. -- March 1998 interview with Castro [http://www.cnn.com/SPECIALS/cold.war/episodes/10/interviews/castro/]

There is clearly nothing in there to suggest that Castro was promoting a first strike by the Soviet Union. Any mention of a nuclear first strike in that paragraph is linked with his justifiable fear that the Americans would be insane enough to do such a thing. In the same interview he goes on to say
:"I dictated this letter to the [Soviet] ambassador. I wrote the letter on the basis of the notes that I had, and the ambassador did not even speak good Spanish, and we had no interpreters. Who knows what the ambassador actually sent over there, but apparently he did convey something of this idea, perhaps not very clearly."
It is impossible to be sure of what Castro was saying without seeing the original Spanish version, as well as the Russian translation that was presented to Khrushchev. To impute these intentions to Castro is a grossly speculative distortion of historical facts. [[User:Eclecticology|Eclecticology]] 21:27, 2004 Apr 23 (UTC)

Yes Ed, your changes are a definite improvement. I'll be wanting to look at the earlier paragraphs. This is a situation where, perhaps because of multiple edits, I had to read it several times to make sense of it, and it even seems that some of it ends up with the opposite sides mixed up. [[User:Eclecticology|Eclecticology]] 22:57, 2004 Apr 23 (UTC)

----
I don't at all understand how that quote from Castro could be construed to say he is recommending first strike against the USA. He's saying that the USA must never be able to get first strike cability on the Communist bloc -- which is no more damning that Robert McNamara saying that the USA would take first strike capability if it had the chance, or that it would be unacceptable for the USA to let the USSR have first strike capability against it. There are many ways to prevent another country from getting first strike capability without advocating nuclear war (for example, the arms race). --[[User:Fastfission|Fastfission]] 22:40, 18 Jul 2004 (UTC)

== merge in "First-strike attack" ==

I don't have the time to research the history of nuclear war strategy, so I haven't completed the merge. In general, my thoughts are:

* the introduction, headings, links, and categorization of this article is better than that of the "First-strike attack" article.
* the history from the "First-strike attack" article is interesting, and should be folded into this article - it'd be nice if the editor had a solid knowledge of the history or time to research it, and I don't have either.

[[User:Asmendel|Asmendel]] 23:10, 10 Feb 2005 (UTC)

== Move Bertrand Russell & Hersch/Iran to Different Articles. ==

Moving Bertrand Russell and Hersch/Iran out of this article and into more appropriate locations would be a good idea. Russell only gave his opinions on a first strike, while quite provocative, it never led to one, while the Hersch/Iran item might be better in an article about Iran, the current situation there, or Hersch. —Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Katana0182|Katana0182]] ([[User talk:Katana0182|talk]] • [[Special:Contributions/Katana0182|contribs]]) 06:28, 10 July 2008 (UTC) 

If nobody has any objections, I am going to be [[WP:BOLD]] and move the Hersch/Iran to something about Iranian nuclear weapons programs, and the Bertrand Russell section to an article about Bertrand Russell. I think that these would be more appropriate places for the content of the two sections. Any objections, please discuss; otherwise, will move them in 24-48 hours from of 04:00[[Zulu time|Z]] 15-7-08.[[User:Katana0182|Katana0182]] ([[User talk:Katana0182|talk]]) 03:44, 15 July 2008 (UTC)

It is done.[[User:Katana0182|Katana0182]] ([[User talk:Katana0182|talk]]) 06:31, 17 July 2008 (UTC)

== Historical Analysis Reads Like a Cheap Novel==

Sorry, but it does. In particular the phrase

"Luckily for the world, when the superpowers drew close to the edge of the nuclear abyss during both the Cuban Missile Crisis and the Able Archer/VRYAN Crisis, they took the time to stare intently into its depths, and came away knowing that the abyss stared back into them."

What abyss is this? did the leaders travel to the bottom of the ocean in a submarine to look out the window? and if so, the deep ocean environment has eyes? or is this another abyss that has eyes?

id fix it, but I dont know where to begin. —Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/86.140.76.72|86.140.76.72]] ([[User talk:86.140.76.72|talk]]) 14:43, 21 November 2008 (UTC) 

This article reads like somebody just pasted their high school history paper into Wikipedia. It contains countless uncited and possibly biased points, and uses rhetoric for dramatic effect that has no place in an encyclopedia. [[Special:Contributions/96.48.73.85|96.48.73.85]] ([[User talk:96.48.73.85|talk]]) 19:30, 19 February 2010 (UTC)
== Anti-Russian bias? ==

This article seems to have many POV issues, for example:
<blockquote>
The military invasion of Iraq was seen by Russia as indicating potential U.S. disrespect for what the Russian leadership views as international law, '''which it allegedly values'''.
</blockquote>
[[Special:Contributions/24.36.78.185|24.36.78.185]] ([[User talk:24.36.78.185|talk]]) 15:36, 27 June 2009 (UTC)
:Will rewrite phrasing in attempt to avoid appearance of impropriety. [[Special:Contributions/74.106.86.91|74.106.86.91]] ([[User talk:74.106.86.91|talk]]) 00:11, 24 September 2009 (UTC)

== Trident II incomplete sentence problem ==

In the article section on possible first strike systems, the Trident II is discussed, and ends with this sentence:

:However, the fact that SSBNs are usually deep underwater for their mission, and can only receive very low rate data communications via VLF or ELF, causing slow reception and verification of strike orders, and the one-missile at a time fire rate of a nuclear missile submarine.

This is not a complete sentence. I would assume that something needs to be added that either relates to the GPS guidance discussed in the preceding sentence or the countervalue purpose mentioned at the beginning of the paragraph. As it is, I'm not sure where the sentence was headed. --[[User:Wesley R. Elsberry|Wesley R. Elsberry]] ([[User talk:Wesley R. Elsberry|talk]]) 05:10, 21 December 2009 (UTC)

== Overall Content of this Article ==

There is a problem overall with this article. As mentioned by others, it is written as a personal reflection essay. While reading it I discovered another flaw, one that has not already been posted. This flaw is that, the article itself, focuses too much on the "Cold War", and it's history. This article is only about what a "Nuclear First Strike" is, not any other social, or political issues. (Unless there is a specific sub-category, but presently, there is not). —Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Gold Contaxt|Gold Contaxt]] ([[User talk:Gold Contaxt|talk]] • [[Special:Contributions/Gold Contaxt|contribs]]) 18:15, 24 July 2010 (UTC) 

== This Entire Article Needs to Be Re-Written, In a Neutral, Scholarly Manner ==

This article is written like an essay, and is full of personal opinions/interpretations. Additionally, like another user said, this article only covers the U.S & Soviet Russia; this must be widened to include the entire world. —Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Gold Contaxt|Gold Contaxt]] ([[User talk:Gold Contaxt|talk]] • [[Special:Contributions/Gold Contaxt|contribs]]) 02:27, 27 September 2010 (UTC) 

== Historical Background Problems ==

Maybe the Historical Background section should just be removed entirely. None of it seems directly related to the topic. —Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[User:Nivlek273|Nivlek273]] ([[User talk:Nivlek273|talk]] • [[Special:Contributions/Nivlek273|contribs]]) 19:12, 4 November 2010 (UTC) 

== Detailed source and film<nowiki>:</nowiki> SIOP-62 ==
* [http://www.gwu.edu/~nsarchiv/NSAEBB/NSAEBB130/ ''The Creation of SIOP-62 More Evidence on the Origins of Overkill'' National Security Archive Electronic Briefing Book No. 130'', gwu.edu, July 13, 2004]
* [http://www.gwu.edu/~nsarchiv/nukevault/ebb336/index.htm ''"Nobody Wins a Nuclear War" But "Success" is Possible Mixed Message of 1950s Air Force Film on a U.S.-Soviet Conflict''] ( Air Force Special Film Project 416, "Power of Decision"- Produced by Air Photographic and Charting Service (component of Military Air Transport Service) Circa 1958, For Official Use Only)

== Launch on Warning ==

From the section on Increasing alert state and readiness:
"By adopting a launch on warning nuclear posture, the possibility of a first-strike can be significantly mitigate."

This might be a matter of the definition of "first strike", but it seems to me that the launch on warning strategy increases the probability of it happening: an incorrect warning could lead to an inadvertent first strike. I assume that the point being made here is that the term "first strike" is being used to refer to an unprovoked, deliberate nuclear attack rather than what the "attacking" side might see as a counterattack; but the distinction is not particularly clear.
[[Special:Contributions/200.121.193.133|200.121.193.133]] ([[User talk:200.121.193.133|talk]]) 06:48, 1 April 2011 (UTC)

== Jargon of "first strike capability" ==

The use of the term "first strike capability" appears twice, once in the opening summary and a second time in the body of the article. In both cases it appears to be used as technical jargon of nuclear warfare strategy, but in neither case are there any citations as to this concept. Contrast this with "second-strike capability," which indeed is a major concept, literally the ability (capability) of a country to retaliate on the perpetrator of an initial nuclear attack and thereby guarantee, in most cases, mutually-agreed destruction, another well-established term and concept.

I don't think "first strike capability" is a thing outside of casual use and coincidental formation, eg, discussing that cruise missiles are too slow to have the capability to be used in a first strike (ergo "first strike capability"), and/or misstatements by, at best, the media. After all, ANY nation possessing nuclear weapons thereby has a "first strike capability," - that is, the ability to use their weapons first - but in the context it seems to be used (suppression of enemy weapons to deny them second strike capability) this is more properly a [pre-emptive] disarming nuclear strike - another variety for instance is the decapitation strike. These specific terms are more narrow in their definition and obvious in their meaning, so I think this term either needs some backup in the form of references or should really be extinguished, especially with its spurious treatment as a genuine technical term. [[User:AnyyVen|AnyyVen]] ([[User talk:AnyyVen|talk]]) 17:43, 30 November 2017 (UTC)
== "First strike" listed at [[Wikipedia:Redirects for discussion|Redirects for discussion]] ==
[[File:Information.svg|30px]]
A discussion is taking place to address the redirect [[:First strike]]. The discussion will occur at [[Wikipedia:Redirects for discussion/Log/2020 November 3#First strike]] until a consensus is reached, and readers of this page are welcome to contribute to the discussion.  [[User:TheAwesomeHwyh|TheAwesome]][[User_Talk:TheAwesomeHwyh|Hwyh]] 15:35, 3 November 2020 (UTC)
== "First-strike" listed at [[Wikipedia:Redirects for discussion|Redirects for discussion]] ==
[[File:Information.svg|30px]]
A discussion is taking place to address the redirect [[:First-strike]]. The discussion will occur at [[Wikipedia:Redirects for discussion/Log/2020 November 3#First-strike]] until a consensus is reached, and readers of this page are welcome to contribute to the discussion.  [[User:TheAwesomeHwyh|TheAwesome]][[User_Talk:TheAwesomeHwyh|Hwyh]] 15:35, 3 November 2020 (UTC)

==Unsourced==
Some parts of this page like "historical analysis" are unsourced and terribly written. [[User:My very best wishes|My very best wishes]] ([[User talk:My very best wishes|talk]]) 19:49, 3 November 2020 (UTC)

:[[User:My very best wishes|@My very best wishes]] much of this article seems like the writer's opinion. [[User:Angiest|Angiest]] ([[User talk:Angiest|talk]]) 18:47, 10 March 2022 (UTC)

== Move to "First strike (nuclear strategy)"? ==

The article unanimously uses the term "first strike" and makes zero mention of the term "pre-emptive [sic?] nuclear strike", even though that is the article's title.

Given that, I argue the article should be titled "first strike".

I understand that the term "first strike" refers to [[first strike (disambiguation)|other things]], so I think a fair and unambiguous title would be "First strike (nuclear strategy)". [[User:Quohx|Quohx]] ([[User talk:Quohx|talk]]) 06:17, 28 March 2022 (UTC)

I am going to move it preemptively, as this is probably not very controversial. [[User:Quohx|Quohx]] ([[User talk:Quohx|talk]]) 06:21, 28 March 2022 (UTC)

== ... to be updated... ==

https://www.defenseone.com/policy/2022/03/bidens-nuke-review-omits-no-first-use-kills-naval-cruise-missile/363823/ [[Special:Contributions/88.163.124.35|88.163.124.35]] ([[User talk:88.163.124.35|talk]]) 08:56, 14 October 2022 (UTC)

United States bombing of the Chinese embassy in Belgrade

2022-05-31T16:36:08Z

88.163.124.35: /* Settlement */

{{short description|1999 bombing of a diplomatic mission}}
{{Use mdy dates |date = January 2012}}{{Use American English|date = April 2019}}
{{Infobox civilian attack
| partof = the [[NATO bombing of Yugoslavia]] and the [[Kosovo War]]
| title = United States bombing of the Chinese embassy in Belgrade
| image = Chinese-embassy-belgrade-post-bombing.JPG
| caption = The Embassy Building in 2009, demolished in 2011. In 1999, the embassy was damaged by the United States.
| location = [[Belgrade]], [[Republic of Serbia (1992–2006)|Serbia]], [[Federal Republic of Yugoslavia|Yugoslavia]]
| coordinates = {{coord|44.8250|N|20.4190|E|display=title, inline}}
| target = Disputed
| date = May 7, 1999
| time =
| timezone =
| type = [[strategic bombing|Aerial bombing]]
| fatalities = 3<ref name=bbc-20190507-dead-injured>{{cite news |url=https://www.bbc.co.uk/news/world-europe-48134881 |title=The night the US bombed a Chinese embassy |first1=Kevin |last1=Ponniah |first2=Lazara |last2=Marinkovic |work=BBC News |date=7 May 2019 |access-date=12 October 2021|quote=In total, three people were killed and at least 20 injured.}}</ref>
| injuries = At least 20<ref name=bbc-20190507-dead-injured/>
| perps = [[United States Air Force]]
| motive =
}}
{{Campaignbox Kosovo War}}

On May 7, 1999, during the [[NATO bombing of Yugoslavia]] (Operation Allied Force), five U.S. [[Joint Direct Attack Munition]] guided bombs hit the [[People's Republic of China]] [[embassy]] in the [[Belgrade]] district of [[Novi Beograd|New Belgrade]], killing three [[Chinese state media]] journalists and outraging the Chinese public.<ref name=bbc-20190507>{{cite news |url=https://www.bbc.co.uk/news/world-europe-48134881 |title=The night the US bombed a Chinese embassy |first1=Kevin |last1=Ponniah |first2=Lazara |last2=Marinkovic |work=BBC News |date=7 May 2019 |access-date=12 October 2021}}</ref> According to the U.S. government, the intention had been to bomb the nearby Yugoslav Federal Directorate for Supply and Procurement (FDSP). President [[Bill Clinton]] apologized for the bombing, stating it was an accident.<ref>{{Cite web|date=May 10, 1999|title=CNN - Clinton apologizes to China over embassy bombing - May 10, 1999|url=http://edition.cnn.com/WORLD/europe/9905/10/kosovo.china.02/|url-status=live|access-date=2021-10-12|website=CNN}}</ref><ref>{{Cite web|date=May 10, 1999|title=Youth Violence and Embassy Bombing Apology {{!}} C-SPAN.org|url=https://www.c-span.org/video/?123188-1/youth-violence-embassy-bombing-apology|url-status=live|access-date=2021-10-12|website=CSPAN|language=en-us}} Begin time: 00:34 End time: 01:54</ref><ref name=crs-report-dumbaugh-apology>{{Cite web|last=Dumbaugh|first=Kerry|date=April 12, 2000|title=Chinese Embassy Bombing in Belgrade: Compensation Issues|url=https://www.everycrsreport.com/reports/RS20547.html|url-status=live|access-date=2021-12-21|website=EveryCRSReport.com|language=en |archive-url=https://web.archive.org/web/20211028171239/https://www.everycrsreport.com/reports/RS20547.html |archive-date=2021-10-28 |quote=U.S. officials offered a number of apologies for the attack...May 10, 1999 – President Clinton, in opening remarks at a White House strategy meeting on children and violence, began with "I would like to say a word about the tragic bombing of the Chinese Embassy in Belgrade. I have already expressed our apology and our condolences to President Jiang and to the Chinese people...."}}</ref> [[Central Intelligence Agency]] (CIA) Director [[George Tenet]] testified before a congressional committee that the bombing was the only one in the campaign organized and directed by his agency,<ref name="Schmitt1">{{cite news |url = http://partners.nytimes.com/library/world/global/072399china-embassy.html |title = In a Fatal Error, C.I.A. Picked a Bombing Target Only Once: The Chinese Embassy |access-date = October 22, 2009 |last= Schmitt |first= Eric |date=July 23, 1999 |work=New York Times |url-access=limited}}</ref> and that the CIA had identified the wrong coordinates for a Yugoslav military target on the same street.<ref name="Tenet">{{cite web |url = https://www.cia.gov/news-information/speeches-testimony/1999/dci_speech_072299.html |title = DCI Statement on the Belgrade Chinese Embassy Bombing House Permanent Select Committee on Intelligence Open Hearing |access-date = October 4, 2006 |last= Tenet |first= George |author-link = George Tenet |date = July 22, 1999 |publisher = Central Intelligence Agency }}</ref> The Chinese government issued a statement on the day of the bombing, stating that it was a "barbarian act".<ref>{{cite news|url=http://edition.cnn.com/WORLD/europe/9905/07/kosovo.05/index.html|title=Chinese demand U.N. meeting after Belgrade embassy attacked|work=CNN|archive-url=https://web.archive.org/web/20150402163309/http://edition.cnn.com/WORLD/europe/9905/07/kosovo.05/index.html|archive-date=April 2, 2015}}</ref>

In October 1999, five months after the bombing, ''[[The Observer]]''<ref group=lower-alpha name=observer_and_guardian>Note that the story actually appears on ''[[The Guardian]]'''s website (www.theguardian.com). ''The Observer'' is published on Sundays and ''The Guardian'' is published daily and both are sister publications owned by [[Guardian Media Group]].</ref> of London along with ''[[Politiken]]'' of Copenhagen, published the results of an investigation citing anonymous sources which said that the bombing had actually been deliberate as the Embassy was being used to transmit Yugoslav army communications.<ref name=observer1/><ref>{{cite news |url=https://politiken.dk/search/?q=NATO%20ambassade&target=epaper&fDate=1999-10-17&tDate=1999-10-17 |title=Kina hjalp Jugoslavien |trans-title=China helped Yugoslavia |language=da |pages=1, 10 |work=Politiken |last1=Holsøe |first1=Jens |last2=Larsen |first2=Jørgen |last3=Leijonhufvud |first3=Göran |date=October 17, 1999 |url-access=subscription}}</ref> The governments of both the U.S. and the U.K. emphatically denied it was deliberate, with U.S. Secretary of State [[Madeleine Albright]] calling the story "balderdash" and British Foreign Secretary [[Robin Cook]] saying there was "not a single shred of evidence" to support it.<ref>{{cite news |url=https://www.bbc.co.uk/news/world-europe-48134881 |title=The night the US bombed a Chinese embassy |first1=Kevin |last1=Ponniah |first2=Lazara |last2=Marinkovic |work=BBC News |date=7 May 2019 |access-date=12 October 2021 |quote=US Secretary of State Madeleine Albright decried the story as "balderdash", while British Foreign Secretary Robin Cook said there was "not a single shred of evidence" to support it.}}</ref> In April 2000 ''[[The New York Times]]'' published the results of its own investigation for which, "the investigation produced no evidence that the bombing of the embassy had been a deliberate act."<ref name=WideNet_no_evidence>{{cite news
|author=Steven Lee Myers |title = Chinese Embassy Bombing: A Wide Net of Blame |url=https://www.nytimes.com/2000/04/17/world/chinese-embassy-bombing-a-wide-net-of-blame.html
|work=New York Times |location=New York |date=April 17, 2000 |access-date=October 18, 2021 |url-access=limited |quote=While the investigation produced no evidence that the bombing of the embassy had been a deliberate act, it provided a detailed account of a broader set of missteps than the United States or NATO have acknowledged...All of the officials interviewed by the Times said they knew of no evidence to support the assertion, and none has been produced.}}</ref>

Right after the bombing, most Chinese believed it was deliberate and many continue to believe that it was deliberate;<ref>{{multiref2
|1=That most Chinese believe that the bombing was deliberate was mentioned in the ''BBC News'' coverage at the twentieth anniversary of the bombing in May of 2019:
|2={{cite news |url=https://www.bbc.co.uk/news/world-europe-48134881 |title=The night the US bombed a Chinese embassy |first1=Kevin |last1=Ponniah |first2=Lazara |last2=Marinkovic |work=BBC News |date=7 May 2019 |access-date=12 October 2021 |quote=But, as former Nato officials point out, in 20 years no clear evidence has come to light proving what almost all of China believes and America strenuously denies: that it was deliberate.}}
|3=It was also mentioned in these two academic papers from 2010 and 2001:
|4={{Cite journal|last=Moore|first=Gregory J.|date=2010|title=Not Very Material but Hardly Immaterial: China's Bombed Embassy and Sino-American Relations|url=https://www.jstor.org/stable/24909876|journal=Foreign Policy Analysis|volume=6|issue=1|pages=23–41|doi=10.1111/j.1743-8594.2009.00100.x|jstor=24909876|issn=1743-8586|quote=While Americans explained that the embassy bombing was a horrible mistake, most Chinese are convinced to this day that it was an intentional attack.}} [https://papers.ssrn.com/sol3/papers.cfm?abstract_id=1449449 Preprint version of the content of the published paper] publicly available via [[SSRN]].
|5={{cite journal | author = Peter Hays Gries |date=July 2001 | title = Tears of Rage: Chinese Nationalist Reactions to the Belgrade Embassy Bombing | journal = The China Journal | issue = 46 | pages = 25–43 | publisher = Contemporary China Center, Australian National University | location = Canberra, Australia |doi=10.2307/3182306 | issn = 1324-9347 | oclc = 41170782 | jstor=3182306 |s2cid=145482835 |quote=Few accepted America's explanation that the bombing (and subsequent death of three Chinese journalists) was a mistake caused by the CIA's use of outdated maps}}
|6=And in this PhD thesis from 2005:
|7={{cite thesis |last=Wu |first=Xu |url=https://ufdc.ufl.edu/UFE0011607/00001 |date=2005 |title=Chinese Cyber Nationalism: How China's Online Public Sphere Affected Its Social and Political Transitions |publisher=University of Florida |quote=Most Chinese people with some political consciousness believed, and still believe till today, that this bombing was an intentional attempt, by the U.S. Department of Defense or maybe some lower-level officials, to humiliate China or to stop China’s intervention.}}}}</ref> however, in the results from structured interviews conducted in 2002, of the 57% of Chinese Sino-American relations experts who believed that the bombing was deliberate, 87.5% did not suspect President Clinton's involvement.<ref>{{Cite journal|last=Moore|first=Gregory J.|date=2010|title=Not Very Material but Hardly Immaterial: China's Bombed Embassy and Sino-American Relations|url=https://www.jstor.org/stable/24909876|journal=Foreign Policy Analysis|volume=6|issue=1|pages=23–41|doi=10.1111/j.1743-8594.2009.00100.x|jstor=24909876|issn=1743-8586|quote=Of the 57% of the Chinese experts who believed the bombing was intentional, 87.5% believed President Clinton had no motives to do it and consequently they did not suspect his involvement.}} [https://papers.ssrn.com/sol3/papers.cfm?abstract_id=1449449 Preprint version of the content of the published paper] publicly available via [[SSRN]].</ref>

In August 1999 the United States agreed to compensate the victims of the bombing and their families.<ref>{{Cite web|last=Chu|first=Henry|date=July 31, 1999|title=U.S. to Pay $4.5 Million for Bombing of Chinese Embassy in Yugoslavia|url=https://www.latimes.com/archives/la-xpm-1999-jul-31-mn-61319-story.html|url-access=limited|url-status=live|archive-url=https://web.archive.org/web/20211221210416/https://www.latimes.com/archives/la-xpm-1999-jul-31-mn-61319-story.html|archive-date=2021-12-21|access-date=2021-12-21|website=Los Angeles Times|language=en-US}}</ref> In December 1999 the United States agreed to pay China for the damage to the embassy and China agreed to compensation to the United States for damage to U.S. property that occurred during the demonstrations.<ref>{{Cite news|last=Laris|first=Michael|date=December 16, 1999|title=U.S., China Reach Deal On Embassy Payments|language=en-US|newspaper=Washington Post|url=https://www.washingtonpost.com/archive/politics/1999/12/16/us-china-reach-deal-on-embassy-payments/690c1ec6-b118-487a-a086-fc850ef67a67/|url-access=limited|access-date=2021-12-21|issn=0190-8286}}</ref><ref>{{Cite news|last=Rosenthal|first=Elisabeth|date=1999-12-16|title=U.S. Agrees To Pay China $28 Million For Bombing|language=en-US|work=The New York Times|url=https://www.nytimes.com/1999/12/16/world/us-agrees-to-pay-china-28-million-for-bombing.html|url-access=limited|access-date=2021-12-21|issn=0362-4331}}</ref><ref name=crs-report-dumbaugh>{{Cite web|last=Dumbaugh|first=Kerry|date=April 12, 2000|title=Chinese Embassy Bombing in Belgrade: Compensation Issues|url=https://www.everycrsreport.com/reports/RS20547.html|url-status=live|access-date=2021-12-21|website=EveryCRSReport.com|language=en |archive-url=https://web.archive.org/web/20211028171239/https://www.everycrsreport.com/reports/RS20547.html |archive-date=2021-10-28 }}</ref>

In May 2000 a major U.S.-China trade bill passed the United States House of Representatives which became the [[United States–China Relations Act of 2000]]<ref>{{Cite web|title=HR 4444 - U.S.-China Relations Act of 2000 - National Key Vote|url=https://justfacts.votesmart.org/bill/3035/7879/us-china-relations-act-of-2000#7879|url-status=live|archive-url=https://web.archive.org/web/20210701203144/https://justfacts.votesmart.org/bill/3035/7879/us-china-relations-act-of-2000|archive-date=2021-07-01|access-date=2021-12-21|website=[[Vote Smart]]}}</ref> integrating with China's entry into the [[World Trade Organization]].<ref>{{Cite news|last1=Vita|first1=Matthew|last2=Eilperin|first2=Juliet|date=May 25, 2000|title=House Passes China Trade Bill|language=en-US|newspaper=Washington Post|url=https://www.washingtonpost.com/archive/politics/2000/05/25/house-passes-china-trade-bill/322ed34f-5d5f-4c6e-8e9e-d3e7a8d36128/|url-access=limited|access-date=2021-12-21|issn=0190-8286}}</ref><ref>{{Cite web|last=Lardy|first=Nicholas R.|date=May 10, 2000|title=Permanent Normal Trade Relations for China|url=https://www.brookings.edu/research/permanent-normal-trade-relations-for-china/|url-status=live|archive-url=https://web.archive.org/web/20211210130611/https://www.brookings.edu/research/permanent-normal-trade-relations-for-china/|archive-date=2021-12-10|access-date=2021-12-21|website=[[Brookings Institution]]|language=en-US}}</ref><ref>{{Cite web|title=China Trade bill (2000 - H.R. 4444)|url=https://www.govtrack.us/congress/bills/106/hr4444|url-status=live|archive-url=https://web.archive.org/web/20210426091427/https://www.govtrack.us/congress/bills/106/hr4444|archive-date=2021-04-26|access-date=2021-12-21|website=[[GovTrack]]|language=en}}</ref> By June 2000, during a visit to China by U.S. Secretary of State Madeleine Albright, both sides said that relations between them had improved.<ref>{{Cite news|last=Perlez|first=Jane|date=June 23, 2000|title=With Relations Warming, Albright Presses China on Taiwan|language=en-US|work=The New York Times|url=https://www.nytimes.com/2000/06/23/world/with-relations-warming-albright-presses-china-on-taiwan.html|access-date=2021-12-21|issn=0362-4331|quote=More than a year after the NATO bombing of the Chinese Embassy in Serbia, the United States and China officially declared today during a visit by Secretary of State Madeleine K. Albright that the interlude of bitterness had given way to an era of improved relations.}}</ref>

== Sequence of events ==
In the days prior to the bombing, an attack folder labelled "Belgrade Warehouse 1" was circulated for command approval. The folder originated within the CIA and described the target as a warehouse for a Yugoslav government agency suspected of arms proliferation activities. In this form, the strike was approved by President Clinton.<ref name=WideNet>{{cite news
|author=Steven Lee Myers |title = Chinese Embassy Bombing: A Wide Net of Blame |url=https://www.nytimes.com/2000/04/17/world/chinese-embassy-bombing-a-wide-net-of-blame.html
|work=New York Times |location=New York |date=April 17, 2000 |access-date=October 18, 2021 |url-access=limited}}</ref>

It is unclear if other [[NATO]] leaders approved the strike. A report by the French Ministry of Defense after the war stated that "part of the military operations were conducted by the United States outside the strict framework of NATO"<ref name=outside_nato>{{cite news |url = https://www.nytimes.com/1999/11/11/world/us-military-acted-outside-nato-framework-during-kosovo-conflict-france-says.html |title = U.S. Military Acted Outside NATO Framework During Kosovo Conflict, France Says |access-date=October 19, 2021 |last= Whitney |first= Craig |date=November 11, 1999|work=New York Times |url-access=limited}}</ref> and that a dual-track command structure existed. NATO had no authority to use any [[Northrop Grumman B-2 Spirit|B-2 stealth bomber]] which was used to carry out the strike.<ref name=outside_nato/> That the United States was running missions outside of NATO's joint command structure was a source of some contention between the U.S. and other members of NATO, especially France.<ref name=observer2>{{cite news |url=https://www.theguardian.com/theobserver/1999/nov/28/focus.news1 |title=Truth behind America's raid on Belgrade |access-date=October 19, 2021 |date=November 27, 1999|work=The Observer |location=London}}</ref>

According to officials interviewed by ''The New York Times'', the target was checked against a 'no-strike' database of locations such as hospitals, churches, and embassies, but this raised no alarm as the embassy was listed at its old address. Officials said a similar list in the U.K. also had the same error.<ref name=WideNet_no_hit_list>{{cite news
|author=Steven Lee Myers |title = Chinese Embassy Bombing: A Wide Net of Blame |url=https://www.nytimes.com/2000/04/17/world/chinese-embassy-bombing-a-wide-net-of-blame.html
|work=New York Times |location=New York |date=April 17, 2000 |access-date=October 18, 2021 |url-access=limited |quote=According to the officials interviewed by The Times, American commanders in Europe did maintain such a list of buildings, like hospitals, churches and embassies. The Chinese Embassy was on that list, officials said, but at its old address and was not removed. They said the embassy was also listed at the wrong address on a similar list in Britain.}}</ref> However, the joint ''Observer''/''Politiken'' investigation reported that a NATO flight controller in Naples said that on this "don't hit" map the Chinese embassy was listed at its correct location.<ref name="observer1_quote_dont_hit_map">{{cite news|url=https://www.theguardian.com/world/1999/oct/17/balkans |title=Nato bombed Chinese deliberately |work=The Guardian |date= October 17, 1999|access-date=December 15, 2021 |location=London |first1=Ed |last1=Vulliamy |first2=John |last2=Sweeney |quote=A Nato flight control officer in Naples also confirmed to us that a map of 'non-targets': churches, hospitals and embassies, including the Chinese, did exist. On this 'don't hit' map, the Chinese embassy was correctly located at its current site, and not where it had been until 1996 - as claimed by the US and NATO.}}</ref> The investigation also reported that the coordinates of the Chinese embassy were correctly listed in a NATO computer.<ref name="observer2_quote_nato_computer">{{cite news |url=https://www.theguardian.com/Archive/Article/0,4273,3935955,00.html |title=Truth behind America's raid on Belgrade |access-date=October 18, 2021 |date=November 28, 1999|work=The Observer |location=London |quote=In the immediate aftermath of the attack there were some among non-US staff who were suspicious. On 8 May they tapped into the Nato target computer and checked out the satellite co-ordinates for the Chinese Embassy. The co-ordinates were in the computer and they were correct. While the world was being told the CIA had used out-of-date maps, Nato's officers were looking at evidence that the CIA was bang on target.}}</ref>

On the night of May 7–8, the strike was carried out by a single B-2 bomber with a crew of two<ref name="diamond_pg332_quote_single_bomber">{{Cite book |last = Diamond |first = John |title = The CIA and the Culture of Failure: U.S. Intelligence from the end of the Cold War to the Invasion of Iraq |publisher = Stanford University Press |year = 2008 |page = 332 |isbn = 978-0-8047-5601-3 |url-access = registration |url = https://archive.org/details/ciacultureoffail00john/ |quote=In the predawn hours of May 7, 1999, a single B-2 "Spirit" bomber took off from Whiteman Air Force Base in Missouri for the fifteen-hour flight to Belgrade. The highly trained two-member crew,...}}</ref> of the [[United States Air Force]]'s [[509th Bomb Wing]] flying directly out of [[Whiteman Air Force Base|Whiteman AFB]], [[Missouri]]. The bomber was armed with [[Joint Direct Attack Munition|JDAM]] GPS-guided precision bombs accurate to {{convert|13|m|yd|abbr=on}}. However, the geographic coordinates provided by the CIA and programmed into the bombs were those of the Chinese embassy {{convert|440|m|yd|abbr=on}} away. At around midnight local time, five bombs landed at different points on the embassy complex. The embassy had taken precautionary measures in view of the ongoing bombing campaign, sending staff home and housing others in the basement,<ref name="diamond_pg330-332">{{Cite book |last = Diamond |first = John |title = The CIA and the Culture of Failure: U.S. Intelligence from the end of the Cold War to the Invasion of Iraq |publisher = Stanford University Press |year = 2008 |pages = 330–332 |isbn = 978-0-8047-5601-3 |url-access = registration |url = https://archive.org/details/ciacultureoffail00john/}}</ref> but the attack still resulted in three fatalities, Shao Yunhuan (邵云环) who worked for the ''[[Xinhua News Agency]]'', Xu Xinghu (许杏虎) and his wife Zhu Ying (朱颖) who worked for ''[[Guangming Daily]]'', both [[Chinese state media]], as well as at least 20 people injured.<ref name=bbc-20190507-dead-injured/> American officials said that some or all of the three who were killed were actually intelligence agents, but the Chinese denied the claim.<ref name="observer1_quote_intel_agents">{{cite news|url=https://www.theguardian.com/world/1999/oct/17/balkans |title=Nato bombed Chinese deliberately |work=The Guardian |date= October 17, 1999 |access-date=December 15, 2021 |location=London |first1=Ed |last1=Vulliamy |first2=John |last2=Sweeney |quote=Only three people died in the attack, two of whom were, reportedly, not journalists - the official Chinese version - but intelligence officers.}}</ref><ref name="diamond_pg332_quote_intel_officers">{{Cite book |last = Diamond |first = John |title = The CIA and the Culture of Failure: U.S. Intelligence from the end of the Cold War to the Invasion of Iraq |publisher = Stanford University Press |year = 2008 |page = 332 |isbn = 978-0-8047-5601-3 |url-access = registration |url = https://archive.org/details/ciacultureoffail00john/ |quote=U.S. officials later suggested privately that at least two of the three victims were actually intelligence officers, a claim the Chinese denied.}}</ref><ref name=WideNet_quote_intel_agents>{{cite news
|author=Steven Lee Myers |title = Chinese Embassy Bombing: A Wide Net of Blame |url=https://www.nytimes.com/2000/04/17/world/chinese-embassy-bombing-a-wide-net-of-blame.html
|work=New York Times |location=New York |date=April 17, 2000 |access-date=October 18, 2021 |url-access=limited |quote=The officials said that after the bombing they did learn a great deal about the embassy's intelligence operations, including the background of the three Chinese journalists who were killed and who American officials say were in fact intelligence agents.}}</ref>

== Chinese reaction ==
[[File:Flagloweredinrespect.jpg|thumb|right|On May 12, to mourn the deaths of the bombing victims, American flags were ordered to be lowered to half-staff at U.S. diplomatic missions in mainland China and [[HKSAR]]. The photo above shows the lowered American flag at the American consulate in Hong Kong.<ref>{{cite web |url=http://www.usconsulate.org.hk/kosovo/statement.htm |title=Statements on NATO Bombing of China's Embassy in Belgrade |access-date=October 4, 2006 |author=Consulate General of the United States Hong Kong & Macau |author-link=Consul (representative) |date=August 2, 1999 |publisher=U.S. Department of State |archive-url=https://web.archive.org/web/19991013201236/http://www.usconsulate.org.hk/kosovo/statement.htm |archive-date=October 13, 1999 |url-status=dead |df=mdy-all }}</ref> "The lives of those killed and injured was secondary to the escalating tensions between the two powers," states a study of the diplomatic exchanges surrounding the affair. "U.S. officials to the families of the deceased were only incidental and, at best, pro-forma."<ref>{{Cite book| last1 = Negash | first1 = Girma| title = Apologia Politica: States and Their Apologies by Proxy| location = Westport, Connecticut| publisher = [[Lexington Books]]| year= 2007|edition=reprint| page = 116| isbn = 978-0-7391-2206-8 }}</ref>]]
[[File:Anti-American Protests in Nanjing, 1999 (flickr 2543499638).jpg|thumb|An anti-American protest in Nanjing]]
The raid caused a dramatic rise in tension between China and the United States. An official statement on Chinese television denounced what it called a "barbaric attack and a gross violation of Chinese sovereignty".<ref>{{cite news |url = http://news.bbc.co.uk/2/hi/europe/338424.stm |title = Nato hits Chinese embassy |access-date=October 25, 2009 |date=May 8, 1999 |work=BBC News}}</ref> China's ambassador to the [[UN]] described what he called "NATO's barbarian act" as "a gross violation of the United Nations charter, international law and the norms governing international relations" and "a violation of the Geneva convention".<ref>{{cite news |url = http://news.bbc.co.uk/2/hi/europe/338557.stm | title=Embassy strike 'a mistake' |access-date=October 25, 2009 |date=May 8, 1999|work=BBC News}}</ref> On May 12, 1999, the Hong Kong Legislative Council passed the "Condemnation of NATO" motion by a rare bipartisan vote of 54-0.<ref name="hong kong legco">* 香港立法會中文會議記錄：{{cite book |url=https://www.legco.gov.hk/yr98-99/chinese/counmtg/hansard/990512fc.pdf |title=會議過程正式紀錄1999年5月12日星期三 |date=1999-05-12 |newspaper=香港立法會 |page=5425-5474 |archiveurl=https://web.archive.org/web/20030729190443/https://www.legco.gov.hk/yr98-99/chinese/counmtg/hansard/990512fc.pdf |archivedate=2003-07-29}}
* 英文版：{{cite news |last= |date=1995-05-12 |title=Council Meeting (Hansard) 12 May 1999 OFFICIAL RECORD OF PROCEEDINGS |newspaper=香港立法會 |url=https://www.legco.gov.hk/yr98-99/english/counmtg/hansard/990512fe.htm |archiveurl= |archivedate=}}</ref>

Large demonstrations erupted at consular offices of the United States and other NATO countries in China in reaction to news of the bombing. On May 9, 1999, then-[[Vice President of the People's Republic of China|Vice President]] [[Hu Jintao]] delivered a national televised speech calling the act both "criminal" and "barbaric" and that it "has greatly infuriated the Chinese people."<ref>{{cite news |title=Chinese Vice-President Hu: Broadcast to Nation on NATO Strike - Domestic Report. |date=May 9, 1999 |work=BBC Monitoring Asia Pacific - Political |url=https://www.proquest.com/docview/450115043 |id={{ProQuest|450115043}} |url-access=subscription |via=ProQuest}}</ref><ref>{{cite news |title=China: Vice-President's Televised Speech Widely Supported. |date=May 10, 1999 |work=BBC Monitoring Asia Pacific - Political |url=https://www.proquest.com/docview/449810360 |id={{ProQuest|449810360}} |via=ProQuest |url-access=subscription}}</ref><ref name=autogenerated1>(Chinese) ''[[People's Daily]]'' via [[Sina Corporation|Sina.com]] [http://news.sina.com.cn/c/2003-05-25/14421097103.shtml "资料：1999年5月9日胡锦涛就我驻南使馆遭袭击发表讲话"] Accessed October 18, 2021</ref> He said the unauthorized demonstrations in Beijing, Shanghai, Guangzhou, Chengdu and Shenyang reflected the anger and patriotism of the Chinese people, and which the Chinese government fully supported, but urged against extreme and illegal conduct.<ref name=autogenerated1/><ref>{{cite news |url=http://edition.cnn.com/WORLD/asiapcf/9905/09/china.protests.02/ |title=China gives green light to embassy protests, but warns against violence |date=May 9, 1999 |work=CNN |access-date=October 18, 2021 |archive-url=https://web.archive.org/web/20210721054500/http://edition.cnn.com/WORLD/asiapcf/9905/09/china.protests.02/ |archive-date=July 21, 2021 |url-status=live}}</ref><ref name=autogenerated2>{{cite news
|url=http://articles.cnn.com/1999-05-09/world/9905_09_china.protest.03_1_federal-directorate-nato-bombing-supply-and-procurement?_s=PM:WORLD |title=Chinese in Belgrade, Beijing protest NATO embassy bombing |date=May 9, 1999 |work=CNN |archive-url=https://web.archive.org/web/20131231042323/http://www.cnn.com/WORLD/asiapcf/9905/09/china.protest.03/index.html?_s=PM:WORLD |archive-date=December 31, 2013 |url-status=dead}}</ref>

The protests continued for several days, during which tens of thousands of rock-throwing protesters kept U.S. Ambassador [[James Sasser]] and other staff trapped in the [[Embassy of the United States, Beijing|Beijing embassy]].<ref name=bbc-20190507/><ref name=crs-report-dumbaugh/> The residence of the U.S. Consul in Chengdu was damaged by fire and protestors tried to burn the consulate in Guangzhou. There were no reported injuries.<ref name=autogenerated2/>

President Clinton's apologies and those of the U.S. State Department were not initially broadcast by Chinese state-run media outlets. The demonstrations continued for four days before the Chinese government called a halt, eventually broadcasting President Clinton's apology on television and ordering the police to restrain the demonstrators.<ref>{{Cite journal|last=Xinbo|first=Wu|date=2008|title=Understanding Chinese and U.S. Crisis Behavior|journal=The Washington Quarterly|language=en|volume=31|issue=1|pages=63|doi=10.1162/wash.2007.31.1.61|s2cid=153746626|issn=0163-660X |url=https://www.csis.org/analysis/twq-understanding-chinese-and-us-crisis-behavior-winter-2008}}</ref>

For a week, [[General Secretary of the Chinese Communist Party]] [[Jiang Zemin]] declined phone calls from President Bill Clinton, eventually accepting a 30-minute apology call on Friday, May 14, in which Clinton expressed "regret" over the incident.<ref name=crs-report-dumbaugh-apology-call>{{Cite web|last=Dumbaugh|first=Kerry|date=April 12, 2000|title=Chinese Embassy Bombing in Belgrade: Compensation Issues|url=https://www.everycrsreport.com/reports/RS20547.html|url-status=live|access-date=2021-12-21|website=EveryCRSReport.com|language=en |archive-url=https://web.archive.org/web/20211028171239/https://www.everycrsreport.com/reports/RS20547.html |archive-date=2021-10-28 |quote=President Clinton reportedly tried to place several phones calls to Chinese Party Secretary Jiang Zemin, but was rebuffed by Chinese officials. The President finally was able to speak with Jiang on May 14, 1999.}}</ref><ref name="Sly">{{cite news |last1=Sly |first1=Liz |title=JIANG FINALLY ACCEPTS CALL FROM CLINTON, GETS APOLOGY |url=https://www.chicagotribune.com/news/ct-xpm-1999-05-15-9905150119-story.html |access-date=1 August 2020 |work=Chicago Tribune |date=15 May 1999}}</ref> Jiang had chosen to leave U.S.-China leadership communications channels unused as he waited for the Politburo Standing Committee to reach a consensus.<ref name="Ji">{{Cite journal|last = Ji|first = You|date = March 2016|title = China's National Security Commission: theory, evolution and operations|journal = Journal of Contemporary China|volume = 25|issue = 98|page = 185|doi = 10.1080/10670564.2015.1075717|s2cid = 154533489|issn = 1067-0564}}</ref> The time it took for the Politburo to gather necessary information and reach a decision about China's responses motivated Party leadership to revisit a proposal to establish a [[National Security Commission of the Communist Party of China|centralized National Security Commission]], although this was ultimately not implemented at the time.{{sfn|Ji|2016|p=184}}

===Settlement===
By the end of 1999, relations began to gradually improve. In August, the U.S. government made a "voluntary humanitarian payment" of $4.5 million to the families of the three Chinese nationals who were killed and to those who were injured. On December 16, 1999, the two governments reached a settlement under which the United States agreed to pay $28 million in compensation for damage to the Chinese Embassy facility, and China agreed to pay $2.87 million in compensation for damage inflicted to the U.S. Embassy and other diplomatic facilities in China.<ref name=crs-report-dumbaugh/>

Technically, although the $4.5 million paid to the victims and their families came from Department of Defense discretionary funds, the $28 million for the damage to the embassy needed to be appropriated by the United States Congress;<ref name=crs-report-dumbaugh-appropriation-necessary>{{Cite web|last=Dumbaugh|first=Kerry|date=April 12, 2000|title=Chinese Embassy Bombing in Belgrade: Compensation Issues|url=https://www.everycrsreport.com/reports/RS20547.html|url-status=live|access-date=2021-12-21|website=EveryCRSReport.com|language=en |archive-url=https://web.archive.org/web/20211028171239/https://www.everycrsreport.com/reports/RS20547.html |archive-date=2021-10-28 |quote=Although the $4.5 million U.S. “voluntary humanitarian payment” of August 1999 was paid out of DoD discretionary funds, State Department officials maintain that the $28 million U.S. payment for property compensation is too large to be covered by such contingency accounts. Therefore, the property compensation agreement with China has to come from U.S. funds appropriated for that purpose.}}</ref><ref>{{Cite news|last=Laris|first=Michael|date=December 16, 1999|title=U.S., China Reach Deal On Embassy Payments|language=en-US|newspaper=Washington Post|url=https://www.washingtonpost.com/archive/politics/1999/12/16/us-china-reach-deal-on-embassy-payments/690c1ec6-b118-487a-a086-fc850ef67a67/|url-access=limited|access-date=2021-12-21|issn=0190-8286|quote=The delivery of the U.S. funds to the Chinese is contingent on congressional approval, but a U.S. official expressed confidence that the funds will be appropriated as part of the fiscal 2001 budget.}}</ref><ref>{{Cite news|last=Rosenthal|first=Elisabeth|date=1999-12-16|title=U.S. Agrees To Pay China $28 Million For Bombing|language=en-US|work=The New York Times|url=https://www.nytimes.com/1999/12/16/world/us-agrees-to-pay-china-28-million-for-bombing.html|url-access=limited|access-date=2021-12-21|issn=0362-4331|quote=It was also not clear when the money promised under today's agreements will be paid. The $28 million promised by the United States requires congressional approval and will be part of the fiscal year 2001 budget request, embassy officials here said.}}</ref> however, China did not receive any payment.<ref name=bbc-compensation>{{cite news |url=https://www.bbc.co.uk/news/world-europe-48134881 |title=The night the US bombed a Chinese embassy |first1=Kevin |last1=Ponniah |first2=Lazara |last2=Marinkovic |work=BBC News |date=7 May 2019 |access-date=21 December 2021|quote=China would receive $28m in compensation from the US for the bombing, but had to give back close to $3m for the damage to US diplomatic property in Beijing and elsewhere. The US paid another $4.5m to the families of the dead and injured.}}</ref>

==Official investigation and reporting in the aftermath==
Late on May 8, U.S. [[Defense Secretary]] [[William Cohen]] and George Tenet issued a joint press release stating neither the aircrew involved nor the equipment were to blame for the incident.<ref name="Schmitt2">{{cite news |url=https://www.nytimes.com/1999/05/10/world/crisis-in-the-balkans-human-error-wrong-address-of-embassy-in-databases.html?pagewanted=all |title=CRISIS IN THE BALKANS: HUMAN ERROR; Wrong Address of Embassy in Databases|access-date=October 19, 2021 |last= Schmitt |first= Eric |date=May 10, 1999|work=New York Times |url-access=limited}}</ref> The first attempt to explain the bombing came on May 10. William Cohen told reporters "In simple terms, one of our planes attacked the wrong target because the bombing instructions were based on an outdated map".<ref name="DefSec">{{cite web |url=http://www.defenselink.mil/transcripts/transcript.aspx?transcriptid=536 |title=Secretary of Defense Cohen's News Briefing on Chinese Embassy Bombing |access-date=October 23, 2009 |last= Cohen|first= William |date=May 10, 1999|publisher=US Department of Defense}}</ref> The statement made no mention of the CIA. It was subsequently revealed that the CIA possessed maps showing the embassy.<ref name="Schmitt2"/>

While U.S. officials then began, on the record, to deflect questions pending the outcome of further enquiries, they continued to brief journalists off the record. For example, also on May 10, [[Eric P. Schmitt|Eric Schmitt]] published an account with most of the elements that were to feature in [[Director of Central Intelligence|Director of Central Intelligence (DCI)]] Tenet's later admissions. Schmitt reported that from the grainy aerial photographs that were used the two buildings looked very similar in terms of size, shape and height, and that the distance between them is about {{convert|200|yd|m}}.<ref name="Schmitt2"/>

Media criticism focused on the [[National Geospatial-Intelligence Agency|National Imagery and Mapping Agency]] (NIMA) which made an announcement stating that "recent news reports regarding the accuracy of NIMA maps have been inaccurate or incomplete" and that "a hard-copy map is neither intended, nor used, as the sole source for target identification and approval."<ref>{{Cite web|last=Leopold|first=George|date=May 21, 1999|title=Human error takes rap in embassy bombing|url=https://www.edn.com/human-error-takes-rap-in-embassy-bombing/|url-status=live|access-date=October 26, 2021|website=[[EDN (magazine)|EDN]]|language=en-US}} Originally published in [[EE Times|''Electronic Engineering Times'']] May 24, 1999.</ref><ref name="NIMA">{{cite web |title=NIMA: FOR IMMEDIATE RELEASE: Release Number 990516-2: Chinese Embassy Bombing |url=http://164.214.2.59/general/embassy.html |access-date=October 26, 2021 |date=May 16, 1999|publisher=National Imagery and Mapping Agency |archive-url=https://web.archive.org/web/20000229144602/http://164.214.2.59/general/embassy.html |archive-date=February 29, 2000 |url-status=dead}}</ref> CIA Director George Tenet later acknowledged that the map used should never have been used for aerial bombing target selection.<ref name=bbc-20190507/>

===Official State Department account===
In June, [[Under Secretary of State for Political Affairs|Under Secretary of State]] [[Thomas R. Pickering|Thomas Pickering]] led a delegation to China to present the U.S. version of events.<ref name=pickering>{{cite web | url=https://1997-2001.state.gov/policy_remarks/1999/990617_pickering_emb.html | title=Oral Presentation the Chinese Government Regarding the Accidental Bombing of The P.R.C. Embassy in Belgrade|access-date=October 19, 2021 |last=Pickering |first=Thomas R.|date=July 6, 1999|publisher=US Department of State}}</ref>

According to the official account, CIA analysts knew the address of the Yugoimport office to be Bulevar Umetnosti 2 (2 Boulevard of the Arts). Using this information, they attempted to pinpoint its geographic location by using the known locations and addresses of other buildings on parallel streets as reference points. (''The New York Times'' reported that some referred to what was done as "resection and intersection"<ref name=WideNet/><ref group=lower-alpha>In activities such as surveying and inshore marine navigation ''intersection'' refers to finding one's current location by taking bearings from known locations. For example, while in a boat finding the bearing of a lighthouse, and other locations known on a map to find where one is on the water. ''Resection'' refers to finding the location of an unknown distant point by taking bearings to it from known locations. One bearing determines a line, and two bearings determine two lines which then intersect at a point. A third bearing can be taken which ought to intersect at or very close to where the first two lines intersect. See [[Position resection and intersection]]. However, generally speaking, these terms refer to the use of [[Bearing (angle)|bearings]] rather than street addresses.</ref> although Pickering did not use those terms in the statement.)<ref name=pickering/>

Parallel lines were drawn from known addresses and locations on a parallel street. With this information it was attempted to reconstruct the pattern of street addresses on Bulevar Umetnosti, which was information unknown to the targeters. The pattern of street addresses on Bulevar Umetnosti was not as expected, and the targeter erroneously pinpointed the embassy "located on a small side street at some distance on Bulevar Umetnosti" from the intended target.<ref name=pickering/>

Multiple checks designed to prevent attacks on sensitive targets each failed as the location of the embassy had not been updated since the embassy moved to New Belgrade three years earlier. As a result, the bombers took to the air with the coordinates of the Chinese embassy programmed into the bombs on board.<ref name=pickering/>

Pickering said that they found no evidence that the embassy was being used to assist Serbian forces, and said that it is not conceivable that any rogue group within the U.S. would have done such a thing. He said that, "Science has taught us that a direct explanation, backed up by full knowledge of facts obtained through a careful investigation, is always preferable to speculation and far fetched, convoluted or contrived theories with little or no factual backing."<ref name=pickering/>

===George Tenet's statement===
On July 22, [[George Tenet]] made a statement before a public hearing of the House Intelligence Committee.<ref name="Tenet"/> Covering the same ground as Under Sec. Pickering's statement in China, he additionally acknowledged the target package originated within the CIA and that it was the sole CIA-directed strike of the war, stated that he had been personally unaware that the CIA was circulating strike requests and recognised that the CIA possessed maps correctly displaying the embassy. [[United States Deputy Secretary of Defense|Deputy Defense Secretary]] [[John Hamre]], giving evidence the same day, stated that "NIMA is not at fault".<ref name="Hamre">{{cite web |url=https://fas.org/irp/congress/1999_hr/990722-hamre.htm |title=Testimony of John J. Hamre, Deputy Secretary of Defense Before the House Select Committee on Intelligence |access-date=October 26, 2021 |date=July 22, 1999}} Available via the website of the [[Federation of American Scientists]].</ref>

=== Repercussions for CIA employees responsible ===

Tenet reprimanded six CIA officers and fired one as a result of the investigation.<ref>{{Cite web|last=Kettle|first=Martin|date=April 10, 2000|title=CIA takes rap for embassy attack|url=http://www.theguardian.com/world/2000/apr/10/balkans|url-status=live|archive-url=https://web.archive.org/web/20210411035733/https://www.theguardian.com/world/2000/apr/10/balkans|archive-date=April 11, 2021|access-date=2021-11-09|website=The Guardian|language=en}}</ref><ref name=WideNet_cia_employees>{{cite news
|author=Steven Lee Myers |title = Chinese Embassy Bombing: A Wide Net of Blame |url=https://www.nytimes.com/2000/04/17/world/chinese-embassy-bombing-a-wide-net-of-blame.html
|work=New York Times |location=New York |date=April 17, 2000 |access-date=October 18, 2021 |url-access=limited |quote=Last week, 11 months after the fact, the director of central intelligence, George J. Tenet, dismissed a midlevel officer who put the X on what turned out to be the embassy. He also disciplined six other employees, saying that agency officers "at all levels of responsibility" contributed to the bombing.}}</ref>

===Chinese reaction===
Few Chinese politicians believed the U.S. version of events, believing instead that the strike had been deliberate.<ref name="ChinaJournal">{{cite journal | author = Peter Hays Gries |date=July 2001 | title = Tears of Rage: Chinese Nationalist Reactions to the Belgrade Embassy Bombing | journal = The China Journal | issue = 46 | pages = 25–43 | publisher = Contemporary China Center, Australian National University | location = Canberra, Australia |doi=10.2307/3182306 | issn = 1324-9347 | oclc = 41170782 | jstor=3182306|s2cid=145482835 }}</ref>

Former Ambassador [[Li Daoyu]] stated "we don't say it was a decision of Clinton or the White House",<ref name="Arkin2">{{cite news |url=https://www.washingtonpost.com/ac2/wp-dyn/A10160-1999Nov2 |archive-url=https://web.archive.org/web/20180810134624/https://www.washingtonpost.com/ac2/wp-dyn/A10160-1999Nov2/ |url-status=dead |archive-date=August 10, 2018 |title=Chinese Embassy Continues to Smolder|access-date=October 26, 2009 |newspaper=Washington Post| first=William M. | last=Arkin | date=November 8, 1999}}</ref> but the Chinese government describes the U.S. explanation for "the so-called mistaken bombing" as "anything but convincing" and has never accepted the U.S. version of events.<ref>{{cite web|url=http://www.fmprc.gov.cn/eng/ziliao/3602/3604/t18047.htm|title=Strong Protest by the Chinese Government Against The Bombing by the US-led NATO of the Chinese Embassy in the Federal Yugoslavia|access-date=October 22, 2009|date=November 17, 2001|publisher=Ministry of Foreign Affairs of the People's Republic of China|archive-url=https://web.archive.org/web/20090227155823/http://www.fmprc.gov.cn/eng/ziliao/3602/3604/t18047.htm|archive-date=February 27, 2009|url-status=dead|df=mdy-all}}</ref>

The incident left a toxic legacy on China-NATO relations and kept them frozen for years.<ref name=":0" /><ref name=":1" /> In a 2011 meeting with U.S. officials in the aftermath of the [[2011 NATO attack in Pakistan]], Chinese general [[Ma Xiaotian]] directly referred to the embassy bombing by asking "Were you using the wrong maps again?"<ref name=":0">{{Cite web|last=Small|first=Andrew|date=23 May 2012|title=Seizing Opportunities with a Less Reserved Beijing - German Marshall Fund Blog|url=http://blog.gmfus.org/2012/05/23/seizing-opportunities-with-a-less-reserved-beijing/|url-status=dead|archive-url=https://web.archive.org/web/20121117053251/http://blog.gmfus.org/2012/05/23/seizing-opportunities-with-a-less-reserved-beijing/|archive-date=17 November 2012|access-date=10 August 2020|website=German Marshall Fund}}</ref><ref name=":1">{{Cite web|last=Weitz|first=Richard|date=2012-07-06|title=China and NATO: Grappling with Beijing's Hopes and Fears|url=https://jamestown.org/program/china-and-nato-grappling-with-beijings-hopes-and-fears/|access-date=October 26, 2021|publisher=[[Jamestown Foundation]]|language=en-US}}</ref> Observers immediately noted the "cutting" nature of the remark, describing it as "jibing" and "priceless".<ref name=":0" /><ref name=":1" /><ref>{{Cite web|last=Bhakal|first=Maitreya|date=2012-07-07|title=Quote of the day: Mapping a lie|url=http://indiaschinablog.blogspot.com/2012/07/quote-of-day-mapping-lie.html|access-date=2020-08-10|website=India's China Blog}}</ref>

== '' The Observer''/''Politiken'' report ==

On Sunday, October 17, 1999, ''[[The Observer]]''<ref group=lower-alpha name=observer_and_guardian/> published an article by [[John Sweeney (journalist)|John Sweeney]], Jens Holsoe and [[Ed Vulliamy]] stating that the bombing was deliberate.<ref name=observer1>{{cite news |url=https://www.theguardian.com/world/1999/oct/17/balkans |title=Nato bombed Chinese deliberately |work=The Guardian |date= October 17, 1999|access-date=December 15, 2021 |location=London |first1=Ed |last1=Vulliamy |first2=Jens |last2=Holsoe |first3=Ed |last3=Vulliamy}}</ref> On the same day the Copenhagen-based publication ''[[Politiken]]'' published a similar story in Danish saying that the bombing was deliberate, claiming the Chinese were helping the Yugoslavian forces who were engaged in ethnic cleansing and [[War crimes in the Kosovo War|war crimes in Kosovo]].<ref>{{cite news |url=https://politiken.dk/search/?q=NATO%20ambassade&target=epaper&fDate=1999-10-17&tDate=1999-10-17 |title=Kina hjalp Jugoslavien |trans-title=China helped Yugoslavia |language=da |pages=1, 10 |work=Politiken |last1=Holsøe |first1=Jens |last2=Larsen |first2=Jørgen |last3=Leijonhufvud |first3=Göran |date=October 17, 1999 |url-access=subscription |quote=Under hele den 78 døgn lange bombekampagne, der startede 23, marts, var et af de vigtigste mål at ramme den jugoslaviske hærledelses kommunikationslinjer til hæren og politiet i Kosova, der gennemførte en etnisk udrensning, hvor op mod 800.000 etniske albanere blev fordrevet, og hvor over 10.000 blev dræbt.}} (article is available in the Politiken archive accessible with a subscription in image format, but not copyable text)</ref>

On Sunday, November 28, 1999, ''The Observer'' published a follow-up piece stating that the Americans bombed the embassy due to allegations that the Chinese were helping [[Arkan|Željko Ražnatović]], a Serbian mobster, paramilitary leader, and indicted war criminal.<ref name="observer2_quote_deliberate">{{cite news |url=https://www.theguardian.com/theobserver/1999/nov/28/focus.news1 |title=Truth behind America's raid on Belgrade |access-date=October 19, 2021 |date=November 27, 1999|work=The Observer |location=London |quote=The true story - though it is being denied by everyone from Albright, Foreign Secretary Robin Cook and CIA director George Tenet down - is that the Americans knew exactly what they are doing. The Chinese Embassy in Belgrade was deliberately targeted by the most precise weapons in the US arsenal because it was being used by Zeljko Raznatovic, the indicted war criminal better known as Arkan, to transmit messages to his `Tigers' - Serb death squads - in Kosovo...that it was an operating base for Arkan, an indicted war criminal, was something that convinced the Americans to strike.'}}</ref>

In the ''Politiken'' story, a source within the British Ministry of Defense is quoted as saying that the Chinese gave permission to the Yugoslavian army to use the embassy as a communications base. The British source stated the normal practice in this case would be to contact the Chinese and to ask them to stop the activity due to its violation of the Vienna Convention on Diplomatic Activity, and that they assumed that happened but did not have specific knowledge on it.<ref>{{cite news |url=https://politiken.dk/search/?q=NATO%20ambassade&target=epaper&fDate=1999-10-17&tDate=1999-10-17 |title=Kina hjalp Jugoslavien |trans-title=China helped Yugoslavia |language=da |pages=1, 10 |work=Politiken |last1=Holsøe |first1=Jens |last2=Larsen |first2=Jørgen |last3=Leijonhufvud |first3=Göran |date=October 17, 1999 |url-access=subscription |quote=Hans udsagn bekræftes af en kilde i det britiske forsvarsministerium..."Normal praksis i den slags tilfæde er, at man tager kontakt til kineserne og beder dem stoppe denne aktivitet, som er i strid med Wienerkonventionen om diplomatisk aktivitet. Jeg går ud fra, at det også skete her, men har ingen konkret viden om det..."}} (article is available in the Politiken archive accessible with a subscription in image format, but not copyable text)</ref> ''Politiken'' also reported that British sources surmised that the Chinese did not believe NATO would dare strike the embassy.<ref>{{cite news |url=https://politiken.dk/search/?q=NATO%20ambassade&target=epaper&fDate=1999-10-17&tDate=1999-10-17 |title=Kina hjalp Jugoslavien |trans-title=China helped Yugoslavia |language=da |pages=1, 10 |work=Politiken |last1=Holsøe |first1=Jens |last2=Larsen |first2=Jørgen |last3=Leijonhufvud |first3=Göran |date=October 17, 1999 |url-access=subscription |quote=Kineserne har, siger britiske kilder, sikkert regnet med, at NATO ikke ville vove at bombe ambassaden.}} (article is available in the Politiken archive accessible with a subscription in image format, but not copyable text)</ref>

The stories drew from anonymous sources, although in instances overall position in the hierarchy, role, and location was mentioned. One non-anonymous source was Dusan Janjic, an academic and advocate for ethnic reconciliation in Yugoslavia who testified that the military attaché at the embassy, Ren Baokai, openly spoke to him about how China was spying on the U.S.<ref name=bbc-20190507-quote-Dusan-Janjic>{{cite news |url=https://www.bbc.co.uk/news/world-europe-48134881 |title=The night the US bombed a Chinese embassy |first1=Kevin |last1=Ponniah |first2=Lazara |last2=Marinkovic |work=BBC News |date=7 May 2019 |access-date=12 October 2021|quote=On the day of the bombing, Dusan Janjic, an academic and advocate for ethnic reconciliation in Yugoslavia, was having lunch at an upscale restaurant in central Belgrade with a man he considered a good friend. Ren Baokai was the military attaché at the Chinese embassy and Janjic said he was surprisingly open with him about the fact that China was spying on Nato and US operations and tracking warplanes from its Belgrade outpost..}}</ref><ref name=observer1_quote_Dusan_Janjic>{{cite news |url=https://www.theguardian.com/world/1999/oct/17/balkans |title=Nato bombed Chinese deliberately |work=The Guardian |date= October 17, 1999|access-date=December 15, 2021 |location=London |first1=Ed |last1=Vulliamy |first2=Jens |last2=Holsoe |first3=Ed |last3=Vulliamy|quote=The Chinese military attache, Ven Bo Koy, who was seriously wounded in the attack and is now in hospital in China, told Dusan Janjic, the respected president of Forum for Ethnic Relations in Belgrade, only hours before the attack, that the embassy was monitoring incoming cruise missiles in order to develop counter-measures.}}</ref>

[[Madeleine Albright]], U.S. Secretary of State at the time, called the story that the bombing was deliberate "balderdash", and [[Robin Cook]], British Foreign Secretary at the time, said, "I know not a single shred of evidence to support this rather wild story."<ref name=bbc-20190507/><ref>{{cite news|title=Nato embassy attack 'not deliberate'|url=http://news.bbc.co.uk/1/hi/477374.stm|access-date=October 20, 2021 |work=BBC News |date=October 17, 1999}}</ref> The Chinese ambassador to Yugoslavia at the time, Pan Zhanlin, denied in a book that the embassy was being used for rebroadcasting by Yugoslavian forces.<ref name="bbc-20190507-quote-Pan-Zhanlin">{{cite news |url=https://www.bbc.co.uk/news/world-europe-48134881 |title=The night the US bombed a Chinese embassy |first1=Kevin |last1=Ponniah |first2=Lazara |last2=Marinkovic |work=BBC News |date=7 May 2019 |access-date=12 October 2021|quote=The Chinese ambassador who narrowly survived the strike, Pan Zhanlin, denied in a book that the embassy had been used for re-broadcasting and that China, in exchange, had been given parts of the US F-117 stealth fighter jet that Serbian forces had shot down in the early stages of the Nato campaign.}}</ref>

=== Fairness & Accuracy In Reporting (FAIR) posts on lack of U.S. media coverage ===

On October 22, 1999, media critique group [[Fairness & Accuracy in Reporting|Fairness & Accuracy In Reporting]] (FAIR) posted on the lack of U.S. media coverage of ''The Observer''/''Politiken'' report and called on its supporters to contact major newspapers to ask why it was not being covered.<ref name=FAIR1>{{cite web |url=https://fair.org/take-action/action-alerts/u-s-media-overlook-expose-on-chinese-embassy-bombing/ |title=U.S. Media Overlook Expose on Chinese Embassy Bombing |date=October 22, 1999 |work=FAIR |access-date=October 20, 2021}}</ref>

[[Andrew Rosenthal]] of ''The New York Times'' responded along with Douglas Stanglin of ''USA Today'', and FAIR summarized the exchanges in a post on November 3, 1999.<ref name=FAIR2>{{cite web |url=https://fair.org/take-action/activism-updates/chinese-embassy-bombing-media-reply-fair-responds/ |title=Chinese Embassy Bombing–Media Reply, FAIR Responds |date=November 3, 1999 |work=FAIR |access-date=October 20, 2021}}</ref> Rosenthal agreed that coverage should not have referred to the bombing as accidental when this was disputed; however, he said that the stories were not well sourced by their standards. He said that reporters were assigned to look into the matter, but that they were not yet ready to publish (about six months later, in April 2000, they did publish the results of an investigation, and it found no evidence that the bombing was deliberate).<ref name=WideNet_no_evidence/> In the post, and in response to Rosenthal, FAIR listed the various anonymous sources in terms of general position in the command hierarchy, location, and role and said that if they had come forward publicly they could have been court martialed. FAIR also argued that the report is consistent with other information known about the bombing such as where the bombs hit the embassy,<ref name=FAIR2_quote_where_bombs>{{cite web |url=https://fair.org/take-action/activism-updates/chinese-embassy-bombing-media-reply-fair-responds/ |title=Chinese Embassy Bombing–Media Reply, FAIR Responds |date=November 3, 1999 |work=FAIR |access-date=October 20, 2021 |quote=The London Daily Telegraph (6/27/99) disclosed that NATO’s precision-guided missiles struck only the embassy’s intelligence-gathering section.}}</ref><ref name=observer2_right_end_wrong_building>{{cite news |url=https://www.theguardian.com/theobserver/1999/nov/28/focus.news1 |title=Truth behind America's raid on Belgrade |access-date=October 19, 2021 |date=November 27, 1999|work=The Observer |location=London |quote=An intelligence expert told The Observer: `If it was the wrong building, why did they use the most precise weapons on Earth to hit the right end of that `wrong building'?''}}</ref><ref>{{Cite journal|last=Moore|first=Gregory J.|date=2010|title=Not Very Material but Hardly Immaterial: China's Bombed Embassy and Sino-American Relations|url=https://www.jstor.org/stable/24909876|journal=Foreign Policy Analysis|volume=6|issue=1|pages=23–41|doi=10.1111/j.1743-8594.2009.00100.x|jstor=24909876|issn=1743-8586|quote=Again, both Chinese and Western sources show the bombs hit strategic parts of the embassy, including the defense attaché’s office, the intelligence section and the ambassador’s quarters (Observer 1999; Russell 2002)}} [https://papers.ssrn.com/sol3/papers.cfm?abstract_id=1449449 Preprint version of the content of the published paper] publicly available via [[SSRN]].</ref> and also pointed out that ''The Observer''/''Politiken'' report was more widely covered internationally than in the U.S.<ref name=FAIR1_quote_internat_coverage>{{cite web |url=https://fair.org/take-action/action-alerts/u-s-media-overlook-expose-on-chinese-embassy-bombing/ |title=U.S. Media Overlook Expose on Chinese Embassy Bombing |date=October 22, 1999 |work=FAIR |access-date=October 20, 2021 |quote=By contrast, the story appeared in England not only in the Observer and its sister paper, the Guardian (10/17/99), but also in...}}</ref><ref>{{multiref2
|1=These are some of the international publications mentioned by FAIR that covered the report:
|2={{cite news |last=Evants |first=Michael |date=October 18, 1999 |title=Embassy Attack Claim Rejected |work=The Times |location=London |page=16 |url=https://www.proquest.com/docview/318180762 |id={{ProQuest|318180762}} |via=ProQuest |url-access=subscription
}}
|3={{cite news |title=Chinese Embassy Bombed for Help to Serbs: Report British Newspaper Says Mission Transmitted Army Intelligence; Alliance Officials Disagree |date=October 18, 1999 |work=The Globe and Mail |url=https://www.proquest.com/docview/384566422 |location=Toronto |id={{ProQuest|384566422}} |via=ProQuest |url-access=subscription}}
|4={{cite news |title=Britain Denies Chinese Embassy Bombed Deliberately by NATO |date=October 18, 1999 |work=Irish Times |url=https://www.proquest.com/docview/310510731 |location=Dublin |id={{ProQuest|310510731}} |url-access=subscription}}}}</ref>

The story was also covered by ''[[Mother Jones (magazine)|Mother Jones]]'', ''[[In These Times]]'' and ''[[World Socialist Web Site]]''.<ref>{{Cite web|last=Harris|first=Bob|title=The NATO Bombing Of The Chinese Embassy |date=October 29, 1999 |url=https://www.motherjones.com/politics/1999/10/nato-bombing-chinese-embassy/|access-date=October 20, 2021 |website=Mother Jones|language=en-US}}</ref><ref>{{Cite web |last=Bleifuss |first=Joel |title=A Tragic Mistake? |date=December 12, 1999 |url=https://inthesetimes.com/issue/24/01/bleifuss2401.html |access-date=October 20, 2021 |work=In These Times }}</ref><ref>{{Cite web|last=Marsden|first=Chris|date=December 1, 1999|title=Fresh evidence that NATO's bombing of Chinese embassy in Belgrade was deliberate|url=https://www.wsws.org/en/articles/1999/12/chin-d01.html|url-status=live|archive-url=https://web.archive.org/web/20210214090951/https://www.wsws.org/en/articles/1999/12/chin-d01.html|archive-date=February 14, 2021|access-date=2021-11-09|website=World Socialist Web Site|language=en}}</ref>

=== ''Salon'' interview with William M. Arkin ===

A 2000 ''[[Salon.com|Salon]]'' article by Laura Rozen featured an interview of ''Washington Post'' columnist and former intelligence officer [[William Arkin|William M. Arkin]], who stated his belief that the bombing was accidental. Rozen reported that the Chinese embassy and the Hotel Yugoslavia are across the street from each other, and that in the Hotel Yugoslavia, Željko Ražnatović owned a casino and had a headquarters. Both the Hotel Yugoslavia and the Chinese embassy were bombed the same night of May 7.<ref name="Salon">{{cite news |first=Laura |last=Rozen |title=A "Boneheaded" bombing
|url=https://www.salon.com/2000/02/10/embassy/ |work=Salon |location=San Francisco |date=February 10, 2000 |access-date=October 14, 2021 |archive-url=https://web.archive.org/web/20170419084607/https://www.salon.com/2000/02/10/embassy/ |archive-date=2017-04-19 |url-status=live}}</ref><ref>{{cite web |url=http://www.nato.int/koSovo/press/b990508a.htm | title = Morning Briefing | access-date=October 15, 2021|date=May 8, 1999|website=NATO Press Office|quote=We also struck last night the Hotel Jugoslavia, which is a location being used as a barracks for Arkan's Tigers in Belgrade and as an alternate Headquarters for the MUP special police forces.}}</ref>

Arkin told Rozen his belief that certain people at NATO erroneously believed that signals coming from the Hotel Yugoslavia were actually coming from the Chinese embassy saying, "I think there were communications emanating from the Hotel Yugoslavia across the street. And I think that stupid people who are leaking rumors to ''The Observer'' have made that mistake."<ref name="Salon"/>

=== Wreckage of shot down F-117 Nighthawk stealth fighter ===

{{See also|1999 F-117A shootdown|Lockheed F-117 Nighthawk}}

The article from ''The Observer'' in October 1999 reported that a stealth fighter had been shot down early in the air campaign and that since China lacked stealth technology they may have been glad to trade with the Yugoslav forces.<ref name=observer1_stealth_technology>{{cite news |url=https://www.theguardian.com/world/1999/oct/17/balkans |title=Nato bombed Chinese deliberately |work=The Guardian |date= October 17, 1999|access-date=December 15, 2021 |location=London |first1=Ed |last1=Vulliamy |first2=Jens |last2=Holsoe |first3=Ed |last3=Vulliamy |quote=Why the Chinese were prepared to help Milosevic is a more murky question. One possible explanation is that the Chinese lack Stealth technology, and the Yugoslavs, having shot down a Stealth fighter in the early days of the air campaign, were in a good position to trade.}}</ref>

In January 2011 the ''Associated Press'' via ''Fox News'' reported that the unveiled Chinese [[Chengdu J-20|J-20]] may have been developed in part by [[reverse engineering]] the U.S. [[Lockheed F-117 Nighthawk|F-117]] from parts of the wreckage that were recovered.<ref>{{Cite web|date=January 23, 2011 |agency=Associated Press |title=China's New Stealth Fighter May Use US Technology|url=https://www.foxnews.com/tech/chinas-new-stealth-fighter-may-use-us-technology|url-status=live|archive-url=https://web.archive.org/web/20210224202417/http://www.foxnews.com/tech/chinas-new-stealth-fighter-may-use-us-technology|archive-date=2021-02-24|access-date=2021-11-09|website=Fox News|language=en-US}}</ref>

In May 2019 ''BBC News'' reported that, "It's widely assumed that China did get hold of pieces of the plane to study its technology."<ref name=bbc-20190507-stealth-technology>{{cite news |url=https://www.bbc.co.uk/news/world-europe-48134881 |title=The night the US bombed a Chinese embassy |first1=Kevin |last1=Ponniah |first2=Lazara |last2=Marinkovic |work=BBC News |date=7 May 2019 |access-date=November 8, 2021 |quote=It's widely assumed that China did get hold of pieces of the plane to study its technology.}}</ref>

=== ''The Sunday Times'' report of an unpublished memoir by Jiang Zemin ===

In February 2011 ''[[The Sunday Times]]'' published an article stating that an unpublished memoir by former [[Paramount leader|Chinese leader]] [[Jiang Zemin]] recounts how Serbian forces were allowed to use the Chinese embassy, and that privately the U.S. showed evidence of this activity to the Chinese.<ref>{{multiref2
|1=The article is available at no cost via the New Zealand paper ''[[The Press]]'' and is shown with [[PressReader]]. It is also available via ProQuest and with a subscription to ''[[The Times]]'' (''The Times'' and ''[[The Sunday Times]]'' are sister papers).
|2=
|3={{Cite web|last=Sheridan|first=Michael|date=February 14, 2011|title=Former leader admits 'serious' mistake|url=https://www.pressreader.com/new-zealand/the-press/20110214/282699043607081|url-status=live|access-date=2021-11-09|work=The Press|location=Christchurch, New Zealand|via=PressReader}}
|4={{Cite web|last=Sheridan|first=Michael|date=February 13, 2011|title=Chinese embassy blitzed by Nato was hiding Serbs|url=https://www.proquest.com/docview/851401108|url-access=subscription|url-status=live|access-date=2021-11-09|website=The Sunday Times|id={{ProQuest|851401108}}|language=en|via=ProQuest}}
|5={{Cite news|last=Sheridan|first=Michael|date=February 13, 2011|title=Chinese embassy blitzed by Nato was hiding Serbs|language=en|work=The Times|url=https://www.thetimes.co.uk/article/chinese-embassy-blitzed-by-nato-was-hiding-serbs-pdgcctk8r0z|url-access=subscription|access-date=2021-11-09|issn=0140-0460 |archive-url=https://web.archive.org/web/20211109221607/https://www.thetimes.co.uk/article/chinese-embassy-blitzed-by-nato-was-hiding-serbs-pdgcctk8r0z |archive-date=2021-11-09 |url-status=live}}
|6=
|7=A book by David Nauta on NATO and international law also mentions this unpublished memoir.
|8=
|9={{Cite book|last=Nauta|first=David|url=https://books.google.com/books?id=toR1DwAAQBAJ&pg=PA102|title=The International Responsibility of NATO and its Personnel during Military Operations|publisher=Brill|year=2017|isbn=978-90-04-35464-7|pages=102|language=en|quote=In 2011 the former Chinese president Jiang Zemin admitted in an unpublished memoir that Serbian military intelligence units were hiding inside the Chinese embassy in Belgrade when NATO bombed it in 1999.|via=Google Books}} [https://www.semanticscholar.org/paper/The-International-Responsibility-of-NATO-and-its-Nauta/65c7bf2855ae529099b1d922625e995d0bf814d3? Full text available] via [[Semantic Scholar]].}}</ref>

== International Criminal Tribunal for the former Yugoslavia (ICTY) investigation ==
A report conducted by the [[International Criminal Tribunal for the former Yugoslavia|ICTY]] entitled "Final Report to the Prosecutor by the Committee Established to Review the NATO Bombing Campaign Against the Federal Republic of Yugoslavia" after the Kosovo War examined the attack on the Chinese embassy specifically and came to the conclusion that the Office of the Prosecutor should not undertake an investigation concerning the bombing.<ref>{{cite web|title=Final Report to the Prosecutor by the Committee Established to Review the NATO Bombing Campaign Against the Federal Republic of Yugoslavia|url=http://www.icty.org/sid/10052#IVB4|publisher=UNICTY}}</ref> In reaching its decision, it provided the following observations:
*That the root of the failures in target location appears to stem from the land navigation techniques employed by an intelligence officer in an effort to pinpoint the location of the FDSP building at Bulevar Umetnosti 2. The officer used techniques known as "intersection" and "resection" which, while appropriate to locate distant or inaccessible points or objects, are inappropriate for use in aerial targeting as they provide only an approximate location. Using this process, the individual mistakenly determined that the Chinese Embassy was the FDSP headquarters.<ref>{{cite web|title=Final Report to the Prosecutor by the Committee Established to Review the NATO Bombing Campaign Against the Federal Republic of Yugoslavia|url=http://www.icty.org/sid/10052#IVB4|publisher=UNICTY|location=Para 82}}</ref>
*The United States has formally apologized to the Chinese Government and agreed to pay $28 million in compensation to the Chinese Government and $4.5 million to the families of those killed or injured. The CIA has also dismissed one intelligence officer and reprimanded six senior managers. The U.S. Government also claims to have taken corrective actions in order to assign individual responsibility and to prevent mistakes such as this from occurring in the future.<ref>{{cite web|title=Final Report to the Prosecutor by the Committee Established to Review the NATO Bombing Campaign Against the Federal Republic of Yugoslavia|url=http://www.icty.org/sid/10052#IVB4|publisher=UNICTY|location=Para 84}}</ref>
*The aircrew involved in the attack should not be assigned any responsibility for the fact they were given the wrong target and that it is inappropriate to attempt to assign criminal responsibility for the incident to senior leaders because they were provided with wrong information by officials of another agency.<ref>{{cite web|title=Final Report to the Prosecutor by the Committee Established to Review the NATO Bombing Campaign Against the Federal Republic of Yugoslavia|url=http://www.icty.org/sid/10052#IVB4|publisher=UNICTY|location=Para 85}}</ref>

==Amnesty International report==
[[Amnesty International]] examined the NATO air campaign and assessed the legality of its actions.<ref name="Amnesty">{{cite web | url=https://www.amnesty.org/en/documents/eur70/018/2000/en/ | title="COLLATERAL DAMAGE" OR UNLAWFUL KILLINGS? : Violations of the laws of war by NATO during Operation Allied Force|access-date=October 26, 2021 |date=June 5, 2000|publisher=Amnesty International}}</ref> In the case of the embassy bombing Amnesty reported both on the official explanation and to the ''Observer''/''Politiken'' investigation without arbitrating as to which was true. NATO was criticised for continuing its bombing campaign uninterrupted when its safeguards to protect civilians were known to be faulty. A genuinely accidental attack would not imply legal responsibility, but the report stated that "the very basic information needed to prevent this mistake was publicly and widely available at the time" and that, "It would appear that NATO failed to take the necessary precautions required by Article 57(2) of Protocol I."<ref>{{cite web | url=https://www.amnesty.org/en/documents/eur70/018/2000/en/ | title="COLLATERAL DAMAGE" OR UNLAWFUL KILLINGS? : Violations of the laws of war by NATO during Operation Allied Force|access-date=October 26, 2021 |date=June 5, 2000|publisher=Amnesty International |page=60}}</ref> Article 57(2) of [[Protocol I]] of the [[Geneva Conventions]] says that an attacker shall, "do everything feasible to verify that the objectives to be attacked are neither civilians nor civilian objects."<ref>{{Cite web|title=Treaties, States parties, and Commentaries - Additional Protocol (I) to the Geneva Conventions, 1977|url=https://ihl-databases.icrc.org/applic/ihl/ihl.nsf/7c4d08d9b287a42141256739003e636b/f6c8b9fee14a77fdc125641e0052b079|url-status=live|access-date=October 26, 2021|website=International Committee of the Red Cross}}</ref>

==Aftermath==
===Future of the location===
Marking the 10th anniversary of the bombing on May 7, 2009, [[mayor of Belgrade|Belgrade Mayor]] [[Dragan Đilas]] and [[Chinese Ambassador to Serbia]] [[Wei Jinghua]] dedicated a [[commemorative plaque]] at the location. The author of the plaque was Nikola Kolja Milunović.<ref>{{cite web |url=https://www.politika.rs/scc/clanak/85997/Деценија-од-бомбардовања-кинеске-амбасаде |title=Деценија од бомбардовања кинеске амбасаде |trans-title=A decade since the bombing of the Chinese embassy |newspaper=[[Politika]] |language=sr |date=May 7, 2009 |access-date=October 27, 2021 |archive-url=https://web.archive.org/web/20211027043341/https://www.politika.rs/scc/clanak/85997/Деценија-од-бомбардовања-кинеске-амбасаде |archive-date=October 27, 2021 |url-status=live}}</ref> Wreaths were laid at the plaque on May 7, 2017, and also in September 2019.<ref>{{cite web |url=https://www.politika.rs/scc/clanak/380029/Положени-венци-на-месту-погибије-троје-кинеских-новинара |title=Положени венци на месту погибије троје кинеских новинара |trans-title=Wreaths were laid at the place of death of three Chinese journalists |newspaper=[[Politika]] |language=sr |date=May 7, 2017 |access-date=October 27, 2021 |archive-url=https://web.archive.org/web/20211027053630/https://www.politika.rs/scc/clanak/380029/Положени-венци-на-месту-погибије-троје-кинеских-новинара |archive-date=October 27, 2021 |url-status=live}}</ref><ref>{{cite web |url=https://www.politika.rs/scc/clanak/437432/Положени-венци-на-спомен-плочу-кинеским-новинарима |title=Положени венци на спомен-плочу кинеским новинарима |trans-title=Wreaths laid on a memorial plaque to Chinese journalists |newspaper=[[Politika]] |language=sr |date=September 8, 2019|access-date=October 27, 2021 |archive-url=https://web.archive.org/web/20211027053749/https://www.politika.rs/scc/clanak/437432/Положени-венци-на-спомен-плочу-кинеским-новинарима |archive-date=October 27, 2021 |url-status=live}}</ref>

During the visit of [[President of the People's Republic of China]] [[Xi Jinping]] to Serbia in June 2016, he and his [[President of Serbia|Serbian counterpart]] [[Tomislav Nikolić]] visited the location, declared the nearby [[Turnaround (road)|turnaround]] a Square of Serbian-Chinese Friendship and announced the construction of the Chinese Cultural Center on the location of the former embassy.<ref name=bbc-20190507/><ref>{{Cite web|date=June 18, 2016|title=Xi pays homage to Chinese martyrs killed in NATO bombing|url=http://www.xinhuanet.com//english/2016-06/18/c_135446039.htm|url-status=dead|archive-url=https://web.archive.org/web/20160622220656/http://news.xinhuanet.com/english/2016-06/18/c_135446039.htm|archive-date=2016-06-22|access-date=2021-11-09|website=[[Xinhua News Agency]] |quote=Mayor of Belgrade Sinisa Mali announced that the street outside the center will be named after ancient Chinese philosopher Confucius, and the square outside the center will be named "China-Serbia Friendship Square."}}</ref><ref>{{cite web|url= http://www.rts.rs/page/stories/sr/story/9/politika/2355508/predsednik-kine-stize-u-trodnevnu-posetu-srbiji.html|author= Tanjug|title= Predsednik Kine stigao u trodnevnu posetu Srbiji|date= June 17, 2016| publisher= [[Radio Television Serbia]]|language=sr|author-link= Tanjug}}</ref> The construction of the center began on July 20, 2017, in the presence of Mayor [[Siniša Mali]] and Chinese Ambassador [[Li Manchang]]. The center will have ten floors, two below ground and eight above, with a total floor area measuring {{convert|32,000|m2|abbr=on}}. The project will cost 45 million euros.<ref>{{Citation | author = B.H.| title = Počela gradnja prvog kineskog kulturnog centra na Balkanu | newspaper = [[Politika]] | pages = 05 | language = sr | date = July 21, 2017 }}</ref><ref>{{cite web|url= http://rs.n1info.com/a284816/Vesti/Kultura/Pocela-izgradnja-Kineskog-kulturnog-centra-na-Novom-Beogradu.html|author=Beta|title= Počela izgradnja Kineskog kulturnog centra na Novom Beogradu|date= July 20, 2017| publisher= [[N1 (television)|N1]]|language=sr}}</ref><ref name=bbc-20190507/>

In 2020, the Milunović plaque was replaced by a new, "modest" square memorial. While the inscription on the original plaque explained why it had been placed there and included the date of the bombing and number of victims, the new one has a generic text in Serbian and Chinese: ''As a token of gratitude to PR China for support and friendship in hardest moments for the people of the Republic of Serbia, and in memory of the killed''. This sparked objections by the Belgraders, who called the new memorial "a shame" and a "table which says nothing", asking for the reinstatement of the old plaque.<ref>{{cite news | first = Dušan | last = Milenković | script-title=sr: Табла која ништа не казује | trans-title = Table which says nothing | newspaper = Politika | page = 23 | language = sr | date = 28 July 2020}}</ref>

===Rise of anti-Western sentiment and warming of China-Russia relations===
Within the United Nations both China and Russia opposed military action against Yugoslavia.<ref name=crs-report-dumbaugh-china-russia-oppose>{{Cite web|last=Dumbaugh|first=Kerry|date=April 12, 2000|title=Chinese Embassy Bombing in Belgrade: Compensation Issues|url=https://www.everycrsreport.com/reports/RS20547.html|url-status=live|access-date=2021-12-21|website=EveryCRSReport.com|language=en |archive-url=https://web.archive.org/web/20211028171239/https://www.everycrsreport.com/reports/RS20547.html |archive-date=2021-10-28 |quote=For months prior to the accidental bombing of the Chinese Embassy in Belgrade, Chinese officials and Chinese press accounts had been uniformly critical of NATO’s and U.S. military involvement in Kosovo. On March 26, 1999, China joined Russia and Namibia in voting in favor of the U.N. Security Council resolution calling for an immediate halt to NATO airstrikes in Yugoslavia.}}</ref> [[Russia–Serbia relations|Strong cultural ties exist between Russia and Serbia]] and the bombing campaign along with the bombing of the Chinese embassy led to an increase in [[anti-Western sentiment]] in both countries and a warming of [[China-Russia relations]].<ref>{{Cite web |url=https://pittnews.com/article/121917/opinions/analysis-1999-nato-operation-turned-russia-west/ |last=Snyder |first=Christian |title=Analysis: How a 1999 NATO operation turned Russia against the West |date=September 7, 2017 |website=The Pitt News - The University of Pittsburgh's Daily Student Newspaper |access-date=November 1, 2021 |archive-url=https://web.archive.org/web/20210318233355/https://pittnews.com/article/121917/opinions/analysis-1999-nato-operation-turned-russia-west/ |archive-date=March 18, 2021 |url-status=live}}</ref><ref>{{multiref2
|1={{Cite book|last=Deng|first=Yong|url=https://books.google.com/books?id=6wgwzKqVWtoC&pg=PA143|title=China's Struggle for Status: The Realignment of International Relations|date=April 28, 2008|publisher=Cambridge University Press|isbn=978-1-139-47103-9|pages=143|language=en|quote=Perhaps the most serious interest in a separate global grouping surfaced in the aftermath of the NATO air war against Yugoslavia and the mistaken bombing of the Chinese embassy in Belgrade in May 1999. For a brief period, China and Russia did step up military ties, but the drive for an exclusive alliance proved to be feeble and short-lived.|access-date=November 1, 2021|via=Google Books}}
|2=
|3=The book is also available at no cost after registration on Internet Archive:
|4=
|5={{Cite book|last=Deng|first=Yong|url=http://archive.org/details/chinasstrugglefo0000deng|title=China's Struggle for Status: The Realignment of International Relations|publisher=Cambridge University Press|others=Internet Archive|year=2008|isbn=978-0-521-88666-6|pages=143|url-access=registration}}}}</ref><ref>{{Cite web|url=https://www.chinausfocus.com/peace-security/we-remember-1999-very-well--the-nato-bombing-of-the-federal-republic-of-yugoslavia-and-its-impacts-on-sino-russian- |last=Dinic |first=Leonardo |title=We Remember 1999 Very Well'- The NATO Bombing of Yugoslavia and its Impacts on Sino-Russian Relations |publisher=[[China–United States Exchange Foundation]] |date=September 13, 2019 |website=China-US Focus |quote=If studied in the future, it will be clear that the convergence of Chinese and Russian foreign policy began to solidify during the Kosovo War with the NATO bombing of Yugoslavia. |access-date=November 1, 2021 |archive-url=https://web.archive.org/web/20210313043020/https://www.chinausfocus.com/peace-security/we-remember-1999-very-well--the-nato-bombing-of-the-federal-republic-of-yugoslavia-and-its-impacts-on-sino-russian- |archive-date=March 13, 2021 |url-status=live}}</ref>

==See also==
{{Portal|Politics|United States|China|Serbia|1990s}}

* [[Civilian casualties during Operation Allied Force]]
*[[Yinhe incident]]
*[[Hainan Island incident]]
{{Clear}}

== Notes ==
{{Reflist|group=lower-alpha}}

== References ==
{{Reflist}}

== External links ==

{{Wars and battles involving Serbs}}

{{authority control}}{{China–United States relations}}
[[Category:1999 in China]]
[[Category:1999 in international relations]]
[[Category:1999 in Serbia]]
[[Category:1999 in the United States]]
[[Category:Explosions in 1999]]
[[Category:May 1999 events in Europe]]
[[Category:1990s in Belgrade]]
[[Category:20th-century history of the United States Air Force]]
[[Category:China–United States military relations]]
[[Category:Accidents and incidents involving United States Air Force aircraft]]
[[Category:Aerial operations and battles of the Kosovo War]]
[[Category:Airstrikes conducted by the United States]]
[[Category:War-related deaths]]
[[Category:People killed during the NATO bombing of Yugoslavia]]
[[Category:Journalists killed while covering the Yugoslav Wars]]
[[Category:Combat incidents]]
[[Category:Attacks on diplomatic missions of China]]
[[Category:Civilian casualties in the Kosovo War]]
[[Category:NATO airstrikes]]
[[Category:Incidents involving NATO]]
[[Category:Attacks on government buildings and structures]]
[[Category:Office buildings in Serbia]]
[[Category:War crimes]]

Geography of Halloween

2021-10-31T17:57:25Z

88.163.124.35: /* Europe */ ... France....

{{Short description|Event}}
{{Use dmy dates|date=November 2013}}
{{more citations needed|date=November 2010}}
{{multiple image
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| image1 = Halloween Bangladesh.jpg
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| alt2 =
| footer = On All Hallows' Eve, Christians in some parts of the world visit [[Cemetery|graveyards]] to pray and place flowers and candles on the graves of their loved ones.<ref>''Arising from Bondage: A History of the Indo-Caribbean People'' (Ron Ramdin), New York University Press, page 241</ref>
| footer_align = left
}}
[[Halloween]], a contraction of "All Hallows' Eve", is a celebration observed on [[October 31]], the day before the feast of [[All Hallows' Day|All Hallows']], also known as Hallowmas or All Saint's Day. The celebrations and observances of this day occur primarily in regions of the Western world, albeit some traditions vary significantly between geographical areas.

==Origins==
{{Main|Halloween}}
Halloween, also spelled as Hallowe'en or Allhallowe'en, is a contraction of All Hallows' Eve, the eve of [[vigil]] before the Western Christian feast of All Hallows (or All Saints) which is observed on November 1. This day begins the triduum of [[Hallowtide]], which culminates with [[All Souls' Day]]. In the [[Middle Ages]], many Christians held a folk belief that All Hallows' Eve was the "night where the veil between the material world and the [[Christian views on Hades|afterlife]] was at its most transparent".<ref>{{cite web|last1=Devros|first1=Isabelle|title=Little monsters play on All Hallow's Eve|date=31 October 2014|url=http://www.armidaleexpress.com.au/story/2662750/little-monsters-play-on-all-hallows-eve/?cs=475|publisher=The Armidale Express|access-date=2014-10-31}}</ref>

==Americas==
===Canada===
Scottish emigration, primarily to Canada before 1870 and to the United States thereafter, brought the Scottish version of the holiday to each country. The earliest known reference to ritual begging on Halloween in English speaking North America occurs in 1911 when a newspaper in [[Kingston, Ontario]] reported that it was normal for the smaller children to go street "[[guising]]" on Halloween between 6 and 7 p.m., visiting shops, and neighbours to be rewarded with nuts and candies for their rhymes and songs.<ref name="ATP" /> Canadians spend more on candy at Halloween than at any time apart from Christmas. Halloween is also a time for charitable contributions. Until 2006 when UNICEF moved to an online donation system, collecting small change was very much a part of Canadian trick-or-treating.<ref>[http://www.canadiangeographic.ca/blog/posting.asp?ID=935 Mackenzie, Marika. "10 things you didn't know about Halloween in Canada", ''Canadian Geographic'', 31 October 2013] {{webarchive|url=https://web.archive.org/web/20151103005825/http://www.canadiangeographic.ca/blog/posting.asp?ID=935|date=3 November 2015}}</ref> Quebec offers themed tours of parts of the old city and historic cemeteries in the area.<ref>{{cite web|url=http://www.quebecregion.com/en/what-to-do/activities-attractions/ideas/halloween/|title=Halloween Activities - Travel to Quebec City, Canada|last=Québec|first=Office du tourisme de|website=Official Web Site - Québec City Tourism|access-date=1 November 2017}}</ref> In 2014 the hamlet of [[Arviat]], [[Nunavut]] moved their Halloween festivities to the community hall, cancelling the practice of door-to-door "trick or treating", due to the risk of roaming polar bears.<ref>[http://www.slate.com/blogs/future_tense/2014/10/20/arviat_canada_cancels_trick_or_treating_because_of_polar_bears.html Holthaus, Eric. "Canadian Town Cancels Outdoor Halloween Because Polar Bears", ''Slate'', 20 October 2014]</ref><ref>{{cite web|url=http://www.cbsnews.com/news/polar-bears-ruining-halloween-for-some-in-canada-report-claims/|title=Polar bears ruining Halloween for some in Canada, report claims|website=Cbsnews.com|access-date=1 November 2017}}</ref> In British Columbia it is a tradition to set off fireworks at Halloween.<ref>{{cite web|url=http://www.vancitybuzz.com/2014/10/firecrackers-became-vancouver-halloween-tradition/|title=How firecrackers and fireworks became a Vancouver Halloween tradition|date=28 October 2014|website=Vancitybuzz.com|access-date=1 November 2017}}</ref>

===United States===
[[File:Children in Halloween costumes at High Point, Seattle, 1943.jpg|thumb|Children in Halloween costumes at [[High Point, Seattle]], 1943]]
[[File:Frazier Park Halloween.jpg|thumb|right|Community Halloween party in [[Frazier Park, California]].]]
[[File:WJ Halloween.jpg|thumb|upright|Children on Halloween, [[Woody Creek, Colorado]]]]

In the United States, Halloween did not become a holiday until the 19th century. The transatlantic migration of nearly two million Irish following the [[Great Famine (Ireland)|Great Irish Famine (1845–1849)]] brought the holiday to the United States.

American librarian and author [[Ruth Edna Kelley]] wrote the first book length history of the holiday in the U.S., ''The Book of Hallowe'en'' (1919), and references [[souling]] in the chapter "Hallowe'en in America": "All Hallowe'en customs in the United States are borrowed directly or adapted from those of other countries. The taste in Hallowe'en festivities now is to study old traditions, and hold a Scotch party, using [[Robert Burns]]'s poem ''[[Halloween (poem)|Halloween]]'' as a guide; or to go a-souling as the English used. In short, no custom that was once honored at Hallowe'en is out of fashion now."<ref>{{cite web|url=http://www.sacred-texts.com/pag/boh/boh17.htm|title=The Book of Hallowe'en: Chapter XV: Hallowe'en in America|publisher=Sacred-texts.com|access-date=21 November 2013}}</ref> The main event for children of modern Halloween in the United States and Canada is [[trick-or-treating]], in which children, teenagers, (sometimes) young adults, and parents (accompanying their children) disguise themselves in [[Halloween costume|costume]]s and go door-to-door in their neighborhoods, ringing each doorbell and yelling "Trick or treat!" to solicit a gift of candy or similar items.<ref name="ADH">{{cite book|title=Halloween: From Pagan Ritual to Party Night|url=https://archive.org/details/halloweenfrompag00roge|url-access=registration|last=Rogers|first=Nicholas|publisher=Oxford University Press|year=2002|isbn=0-19-516896-8|location=New York|pages=[https://archive.org/details/halloweenfrompag00roge/page/n58 49]–77|chapter=Coming Over: Halloween in North America}}</ref> Teenagers and adults will more frequently attend Halloween-themed costume parties typically hosted by friends or themed events at nightclubs either on Halloween itself or a weekend close to the holiday.

At the turn of the 20th century, Halloween had turned into a night of [[vandalism]], with destruction of property and cruelty to animals and people.<ref>{{cite web|url=http://www.nyise.org/hallowhistory.html|title=Halloween History|publisher=Nyise.org|url-status=dead|archive-url=https://web.archive.org/web/20141031031331/http://www.nyise.org/hallowhistory.html|archive-date=31 October 2014|access-date=21 November 2013}}</ref> Around 1912, the [[Boy Scouts of America|Boy Scouts]], [[Boys & Girls Clubs of America|Boys Clubs]], and other neighborhood organizations came together to encourage a safe celebration that would end the destruction that had become so common on this night.

The commercialization of Halloween in the United States did not start until the 20th century, beginning perhaps with [[Halloween card|Halloween postcards]] (featuring hundreds of designs), which were most popular between 1905 and 1915.<ref>{{cite web|url=http://www.shaktiweb.com/postcards|title=Antique Halloween Postcards and E-cards|last=Anderson|first=Richard|year=2000|publisher=shaktiweb.com|access-date=14 September 2006}}</ref> Dennison Manufacturing Company (which published its first Halloween catalog in 1909) and [[the Beistle Company]] were pioneers in commercially made Halloween decorations, particularly die-cut paper items.<ref>{{cite web|url=http://www.spookshows.com/beistle/beistle.htm|title=Beistle: An American Halloween Giant|author=Dawn Kroma|author2=Lou Kroma|publisher=Spookshows.com|access-date=14 September 2006}}</ref><ref>{{cite web|url=http://www.halloweencollector.com/history|title=A Brief History of Halloween Collectibles|last=Ledenbach|first=Mark B.|publisher=halloweencollector.com|access-date=14 September 2006}}</ref> German manufacturers specialised in Halloween figurines that were exported to the United States in the period between the two World Wars.

Halloween is now the United States' second most popular holiday (after Christmas) for decorating; the sale of candy and costumes is also extremely common during the holiday, which is marketed to children and adults alike. The [[National Confectioners Association]] (NCA) reported in 2005 that 80% of American adults planned to give out candy to trick-or-treaters.<ref name="candyusa.org1">{{cite web|url=http://www.candyusa.org/Media/Seasonal/Halloween/pr_2005.asp|title=Trick-or-treaters can expect Mom or Dad's favorites in their bags this year|year=2005|publisher=National Confectioners Association|archive-url=https://web.archive.org/web/20060827010441/http://www.candyusa.org/Media/Seasonal/Halloween/pr_2005.asp|archive-date=27 August 2006|access-date=14 September 2006}}</ref>
The NCA reported in 2005 that 93% of children planned to go trick-or-treating.<ref name="candyusa.org2">{{cite web|url=http://www.candyusa.org/Classroom/Facts/default.asp?Fact=Halloween|title=Fun Facts: Halloween|year=2005|publisher=National Confectioners Association|archive-url=https://web.archive.org/web/20060912205853/http://www.candyusa.org/Classroom/Facts/default.asp?Fact=Halloween|archive-date=12 September 2006|access-date=14 September 2006}}</ref> According to the [[National Retail Federation]], the most popular Halloween costume themes for adults are, in order: witch, pirate, vampire, cat, and clown.<ref>2006 Halloween Consumer Intentions and Actions Survey. Washington, DC: The National Retail Federation.</ref>{{when|date=November 2018}} Each year, popular costumes are dictated by various current events and pop culture icons. On many college campuses, Halloween is a major celebration, with the Friday and Saturday nearest 31 October hosting many costume parties. Other popular activities are watching horror movies and visiting haunted houses. Total spending on Halloween is estimated to be $8.4 billion.<ref>{{cite web|url=https://nrf.com/resources/consumer-data/halloween-headquarters|title=Halloween Headquarters|publisher=[[National Retail Federation]]|access-date=25 October 2016}}</ref>

====Events====
[[File:Slick Chicks Halloween 1947.jpg|thumb|upright|Four contestants in the Halloween Slick Chick beauty contest in [[Anaheim, California]], 1947]]
Many theme parks stage Halloween events annually, such as [[Halloween Horror Nights]] at [[Universal Studios Hollywood]] and [[Universal Orlando]], [[Mickey's Halloween Party]] and [[Mickey's Not-So-Scary Halloween Party]] at [[Disneyland Resort]] and [[Magic Kingdom]] respectively, and [[Knott's Scary Farm]] at [[Knott's Berry Farm]]. One of the more notable parades is [[New York's Village Halloween Parade]]. Each year approximately 50,000 costumed marchers parade up [[Sixth Avenue (Manhattan)|Sixth Avenue]].<ref>{{cite web|url=http://www.nycgo.com/events/village-halloween-parade1|title=Village Halloween Parade|website=NYCgo.com|access-date=1 November 2017}}</ref> [[Salem, Massachusetts]], site of the [[Salem witch trials]], celebrates Halloween throughout the month of October with tours, plays, concerts, and other activities.<ref>{{cite web|url=http://salemhalloweencity.com/halloween-events-activities-salem/|title=SALEM HALLOWEEN EVENTS FESTIVALS ACTIVITIES|website=Salemhalloweencity.com|access-date=1 November 2017}}</ref> A number of venues in New York's lower Hudson Valley host various events to showcase a connection with [[Washington Irving]]'s ''[[Legend of Sleepy Hollow]]''. [[Van Cortlandt Manor]] stages the "Great Jack o' Lantern Blaze" featuring thousands of lighted carved pumpkins.<ref>{{cite news|url=https://nypost.com/2014/10/04/7-halloween-events-you-wont-want-to-miss/|title=7 Halloween events you won't want to miss|last=Dawson|first=Mackensie|date=4 October 2014|work=New York Post|access-date=3 November 2018}}</ref>

Some locales have had to modify their celebrations due to disruptive behavior on the part of young adults. [[Madison, Wisconsin]] hosts an [[State Street Halloween Party|annual Halloween celebration]]. In 2002, due to the large crowds in the State Street area, a riot broke out, necessitating the use of mounted police and tear gas to disperse the crowds.<ref>{{cite news|url=http://www.jsonline.com/news/state/nov02/93044.asp|title=Halloween revelers erupt in Madison|date=4 November 2002|access-date=18 December 2007|archive-url=https://web.archive.org/web/20060222212133/http://www.jsonline.com/news/state/nov02/93044.asp|archive-date=22 February 2006|publisher=Milwaukee Journal Sentinel}}</ref> Likewise, [[Chapel Hill, NC|Chapel Hill]], site of the [[University of North Carolina at Chapel Hill|University of North Carolina]], has a [[Halloween on Franklin Street|downtown street party]] which in 2007 drew a crowd estimated at 80,000 on downtown Franklin Street, in a town with a population of just 54,000. In 2008, in an effort to curb the influx of out-of-towners, mayor Kevin Foy put measures in place to make commuting downtown more difficult on Halloween.<ref>{{cite news|url=http://www.newsobserver.com/264/story/1276364.html|title=Chapel Hill to goblins: stay away|date=31 October 2008|access-date=31 October 2008|archive-url=https://web.archive.org/web/20081103052017/http://www.newsobserver.com/264/story/1276364.html|archive-date=3 November 2008|publisher=The News & Observer}}</ref> In 2014, large crowds of college students rioted at the Keene, New Hampshire [[Pumpkin Fest (New Hampshire)|Pumpkin Fest]], whereupon the City Council voted not to grant a permit for the following year's festival,<ref name="City Council Reject Pumpkin Fest Permit">{{cite web|url=http://www.concordmonitor.com/home/16367372-95/keene-city-council-rejects-pumpkin-fest-permit|title=Keene City Council rejects pumpkin fest permit|agency=Associated Press|date=3 April 2015|publisher=Concord Monitor|url-status=dead|archive-url=https://web.archive.org/web/20150407050152/http://www.concordmonitor.com/home/16367372-95/keene-city-council-rejects-pumpkin-fest-permit|archive-date=7 April 2015|access-date=3 April 2015}}</ref> and organizers moved the event to [[Laconia, New Hampshire|Laconia]] for 2015.<ref name="Laconia-hosting">{{cite web|url=http://www.wmur.com/news/its-official-laconia-will-host-this-years-pumpkin-festival/32551994|title=It's official: Laconia will host this year's pumpkin festival|last1=Sexton|first1=Adam|date=24 April 2015|publisher=[[WMUR-TV]]|access-date=23 September 2015}}</ref>

===Dominican Republic===
In the [[Dominican Republic]] it has been gaining popularity, largely due to many Dominicans living in the United States and then bringing the custom to the island. In the larger cities of [[Santiago de los Caballeros|Santiago]] or [[Santo Domingo]] it has become more common to see children trick-or-treating, but in smaller towns and villages it is almost entirely absent, partly due to religious opposition. Tourist areas such as [[Sosua]] and [[Punta Cana]] feature many venues with Halloween celebrations, predominantly geared towards adults.<ref>{{cite web|url=http://kiskeya.life/why-dont-dominicans-celebrate-halloween/|title=Why Don't Dominicans Celebrate Halloween?|website=Kiskeya.life|access-date=1 November 2017}}</ref>

=== Mexico (''Día de Muertos'') ===
[[File:Tombe mexicaine le Jour des Morts.jpg|thumb|left|Mexican Tomb on the 2019 Day of the Dead, adorned with the [[cempasúchil]], the traditional flower of the Day of the Dead, and a Halloween ghost balloon, at the historic cemetery of [[San Luis Potosí City]] ]]
Observed in [[Mexico]] and [[Mexicans|Mexican]] communities abroad, [[Day of the Dead]] ([[Spanish language|Spanish]]: ''Día de Muertos'') celebrations arose from the [[syncretism]] of indigenous [[Aztecs|Aztec]] traditions with the Christian Hallowtide of the Spanish colonizers. Flower decorations, altars and candies are part of this holiday season. The holiday is distinct from Halloween in its origins and observances, but the two have become associated because of cross-border connections between Mexico and the United States through popular culture and [[Mexican Americans|migration]], as the two celebrations occur at the same time of year and may involve similar imagery, such as skeletons. Halloween and Día de Muertos have influenced each other in some areas of the United States and Mexico, with Halloween traditions such as costumes and face-painting becoming increasingly common features of the Mexican festival.<ref>{{Cite web|url=https://www.usatoday.com/story/news/world/2017/10/30/no-dia-de-los-muertos-isnt-mexican-halloween/762225001/|title=No, Día de los Muertos isn't 'Mexican Halloween'|last=Cummings|first=William|date=2017-10-30|website=USA TODAY|language=en|access-date=2019-10-24}}</ref><ref>{{Cite web|url=https://www.nbcnews.com/news/latino/what-s-el-d-de-los-muertos-it-s-not-n815966|title=What's El Día de los Muertos? It's Not Scary, and It's Not Halloween|last=Puga|first=Kristina|date=2017-11-01|website=NBC News|language=en|access-date=2019-10-24}}</ref>

==Asia==
===China===
The Chinese celebrate the "[[Hungry Ghost Festival]]" in mid-July, when it is customary to float river lanterns to remember those who have died. By contrast, Halloween is often called "All Saints' Festival" (''Wànshèngjié'', 萬聖節), or (less commonly) "All Saints' Eve" (''Wànshèngyè'', 萬聖夜) or "Eve of All Saints' Day" (''Wànshèngjié Qiányè'', ''萬聖節前夕''), stemming from the term "All Hallows Eve" (hallow referring to the souls of holy saints). Chinese Christian churches hold religious celebrations. Non-religious celebrations are dominated by expatriate Americans or Canadians, but costume parties are also popular for Chinese young adults, especially in large cities. [[Hong Kong Disneyland]] and [[Ocean Park Hong Kong|Ocean Park]] ([[Ocean Park Halloween Bash|Halloween Bash]]) host annual Halloween shows.

[[Mainland China]] has been less influenced by [[Anglo]] traditions than Hong Kong and Halloween is generally considered "foreign". As Halloween has become more popular globally it has also become more popular in China, however, particularly amongst children attending private or international schools with many foreign teachers from North America.<ref>{{cite news|author=Wu Ni|date=30 October 2013|url=http://usa.chinadaily.com.cn/china/2013-10/30/content_17070057.htm|title=Halloween gaining popularity but still sees cultural differences|work=[[China Daily]]}}</ref>

====Hong Kong====
Traditional "door-to-door" trick or treating is not commonly practiced in Hong Kong due to the vast majority of Hong Kong residents living in high-rise apartment blocks. However, in many buildings catering to expatriates, Halloween parties and limited trick or treating is arranged by the management. Instances of street-level trick or treating in Hong Kong occur in ultra-exclusive gated housing communities such as [[The Beverly Hills]] populated by Hong Kong's super-rich and in expatriate areas like Discovery Bay and the Red Hill Peninsula. For the general public, there are events at Tsim Sha Tsui's Avenue of the Stars that try to mimic the celebration.<ref>{{cite web|url=http://gohongkong.about.com/od/hongkongfestivals/a/halloweeninhk.htm|title=Events and Celebrations for Halloween in Hong Kong|last=Boland|first=Rory|date=30 October 2009|work=About.com|access-date=31 October 2009}}</ref> In the [[Lan Kwai Fong]] area of Hong Kong, known as a major entertainment district for the international community, a Halloween celebration and parade has taken place for over 20 years, with many people dressing in costume and making their way around the streets to various drinking establishments.<ref>{{cite web|title=Lan Kwai Fong Halloween Street Party |url=http://www.lankwaifong.com/halloween/ |url-status=dead |archive-url=https://web.archive.org/web/20151101071409/http://www.lankwaifong.com/halloween/ |archive-date=1 November 2015 }}</ref> Many international schools also celebrate Halloween with costumes, and some put an academic twist on the celebrations such as the "Book-o-ween" celebrations at [[Hong Kong International School]] where students dress as favorite literary characters.

===Japan===
[[File:Halloweendisplay-2012-saitama.jpg|thumb|A Halloween display in a local bank window, in [[Saitama prefecture|Saitama]], Japan.]]
Halloween arrived in [[Japan]] mainly as a result of American [[popular culture|pop culture]]. As recently as 2009, it was not appreciated and only celebrated by expats.<ref>{{cite news|last1=Ashcraft|first1=Brian|title=Japan's Infamous Halloween Trains|url=https://kotaku.com/japans-infamous-halloween-trains-1819762246|access-date=24 October 2017|work=[[Gizmodo]]|date=23 October 2017}}</ref> The wearing of elaborate [[costume]]s by young adults at night is recently very popular in areas such as [[Amerikamura]] in [[Osaka]] and [[Shibuya]] in [[Tokyo]], where, in October 2012, about 1700 people dressed in costumes to take part in the Halloween Festival.<ref>{{cite web|url=http://www.upi.com/News_Photos/Features/Halloween-in-Japan/fp/7197 |title=Halloween in Japan |publisher=UPI.com |date=26 October 2012 |access-date=20 November 2013}}</ref> The holiday has become popular with young adults as a costume party and club event.<ref>{{cite news|url=http://www.marketwatch.com/story/how-japan-fell-in-love-with-halloween-for-adults-2014-10-30|last=Richards|first=Jeff W.|title=How Japan fell in love with Halloween for adults|work=Market Watch|publisher=Dow Jones|date=30 October 2014}}</ref> Trick-or-treating for Japanese children has taken hold in some areas. The [[Yakuza]] have taken advantage of the festival by hosting parties and giving snacks and sweets to children, a tradition which goes back at least for 20 years.<ref>{{cite web|url=http://www.japantimes.co.jp/news/2016/11/01/national/yamaguchi-gumi-henchmen-make-kobe-kids-offer-cant-refuse-halloween-sweets/#.WJQPZGczWM8
|title=Yamaguchi-gumi henchmen make Kobe kids an offer they can't refuse: Halloween candy|publisher=The Japan Times|date=1 November 2016 |access-date=2 February 2016}}</ref>

===Philippines===
The period from 31 October through 2 November is a time for remembering dead family members and friends. Many Filipinos travel back to their hometowns for family gatherings of festive remembrance.<ref>{{cite news|url=http://asianjournal.com/lifestyle/how-do-we-spell-halloween-in-the-philippines/|last1=Canopio|first1=Camille|last2=Distor|first2=Tessa|title=How do we spell 'Halloween' in the Philippines?|work=Asian Journal|date=29 October 2014}}</ref>

Trick-or-treating is gradually replacing the dying tradition of ''Pangangaluluwâ'', a local analogue of the old English custom of [[souling]]. People in the provinces still observe ''Pangangaluluwâ'' by going in groups to every house and offering a song in exchange for money or food. The participants, usually children, would sing carols about the souls in [[Purgatory]], with the ''abúloy'' (alms for the dead) used to pay for Masses for these souls. Along with the requested alms, householders sometimes gave the children ''[[Suman (food)|suman]]'' (rice cakes). During the night, various small items, such as clothing, plants, etc., would "mysteriously" disappear, only to be discovered the next morning in the yard or in the middle of the street. In older times, it was believed that the spirits of ancestors and loved ones visited the living on this night, manifesting their presence by taking an item.<ref>{{cite web|url=http://ireport.cnn.com/docs/DOC-509344 |title=Halloween in the Philippines – CNN iReport |publisher=Ireport.cnn.com |date=28 October 2010 |access-date=20 November 2013}}</ref>

As the observation of [[Christmas in the Philippines|Christmas]] traditions in the Philippines begins as early as September, it is a common sight to see Halloween decorations next to Christmas decorations in urban settings.{{citation needed|date=December 2017}}

===Singapore===
Around mid-July Singapore Chinese celebrate "[[Ghost Festival#Singapore and Malaysia|Zhong Yuan Jie / Yu Lan Jie]]" (Hungry Ghosts Festival), a time when it is believed that the spirits of the dead come back to visit their families.<ref>{{cite web|author=National Library Board, Singapore |url=http://infopedia.nl.sg/articles/SIP_758_2004-12-16.html |title=Zhong Yuan Jie (Mid-Year Festival) |publisher=Infopedia |access-date=20 November 2013 |url-status=dead |archive-url=https://web.archive.org/web/20140212235245/http://infopedia.nl.sg/articles/SIP_758_2004-12-16.html |archive-date=12 February 2014 }}</ref> In recent years, Halloween celebrations are becoming more popular, with influence from the west.<ref>{{cite web|url=http://news.asiaone.com/News/Mailbox/Story/A1Story20101101-245033.html |title=What's the big fuss about Halloween? |publisher=News.asiaone.com |date=1 November 2010 |access-date=20 November 2013}}</ref> In 2012, there were over 19 major Halloween celebration events around Singapore.<ref>{{cite web|url=http://www.halloween.sg/2012-singapore-halloween-events-and-parties |archive-url=https://web.archive.org/web/20130818010706/http://www.halloween.sg/2012-singapore-halloween-events-and-parties |url-status=dead |archive-date=18 August 2013 |title=2012 Singapore Halloween Events And Parties – Singapore Halloween |publisher=Halloween.sg |access-date=21 November 2013 }}</ref> SCAPE's Museum of Horrors held its fourth scare fest in 2014.<ref>{{cite web|author=*SCAPE Admin|url=https://scape.sg/public/sources/pdf/SCAPE_Annual_Report_FY1415.pdf|title=Scare Actors Audition| Museum of Horrors IV: The Twins|publisher=Scape.com.sg|date=23 July 2013|access-date=21 November 2013}}</ref> [[Halloween Horror Nights#Universal Studios Singapore|Universal Studios Singapore]] hosts "Halloween Horror Nights".<ref>{{cite web|url=http://www.halloweenhorrornights.com.sg/|title=Halloween Horror Nights 7|website=Halloween Horror Nights 7|access-date=1 November 2017}}</ref>

==Australia and New Zealand==
[[File:Halloween display in Sydney.jpg|thumb|Halloween display in [[Sydney]], [[Australia]].]]
While not traditionally a part of Australian culture, non-religious celebrations of Halloween modelled on [[North America]]n festivities are growing increasingly popular in Australia,<ref>{{cite web|url=http://www.halloween-australia.com/|title=Halloween in Australia - Halloween Australia|website=Halloween Australia|access-date=1 November 2017}}</ref> in spite of seasonal differences and the transition from spring to summer. Criticism stems largely from the fact that Halloween has little relevance to Australian culture.<ref>{{cite news|url=http://www.news.com.au/story/0,27574,26283533-421,00.html |title=Should Australians be Hallo-weaned off Halloween celebrations? |work=news.com.au |date=31 October 2009 |access-date=1 November 2012 |archive-url=https://web.archive.org/web/20091101035209/http://www.news.com.au/story/0%2C27574%2C26283533-421%2C00.html |archive-date= 1 November 2009 |url-status=dead }}</ref><ref name=smh>{{cite news|url=http://www.smh.com.au/national/hell-of-a-row-as-kids-buy-into-imported-halloween-rituals-20091031-hqpn.html|title=Hell of a row as kids buy into imported Halloween rituals|first1=Rachel|last1=Browne|first2=Jonno|last2=Seidler|newspaper=[[The Sydney Morning Herald]]|date=1 November 2009|access-date=1 November 2012}}</ref> It is also considered, by some Australians, to be an unwanted American influence; as although Halloween does have Celtic/European origins, its increasing popularity in Australia is largely as a result of American pop-culture influence.<ref name=smh /><ref>{{cite news|url=http://www.news.com.au/comments/0,23600,26283533-421,00.html |title=Should Australians be Hallo-weaned off Halloween celebrations? (comments) |work=news.com.au |date=31 October 2009 |access-date=1 November 2012 |archive-url=https://web.archive.org/web/20131030213028/http://www.news.com.au/comments/0%2C23600%2C26283533-421%2C00.htm |archive-date=30 October 2013 |url-status=dead }}</ref> Supporters of the event claim that the critics fail to see that the event is not entirely American, but rather Celtic and is no different from embracing other cultural traditions such as [[Saint Patrick's Day]].<ref>{{cite web|url=http://www.smh.com.au/entertainment/about-town/halloween-shouldnt-give-us-the-creeps-20121024-285e5.html|title=Halloween shouldn't give us the creeps|author=Elissa Griesser|work=[[The Sydney Morning Herald]]|access-date=27 October 2012}}</ref>

Halloween historian and author of [https://www.goodreads.com/book/show/939868.Halloween Halloween: Pagan Festival to Trick or Treat], Mark Oxbrow says while Halloween may have been popularised by depictions of it in US movies and TV shows, it isn't a new entry into Australian culture<ref>https://www.hallozween.com.au/history-of-halloween/</ref> . His research shows Halloween was first celebrated in Australia in Castlemaine, Victoria, in 1858, which was 43 years before [[Federation of Australia|Federation]]. His research shows Halloween traditions were brought to the country by Scottish and Irish miners who settled in Victoria during the [[Gold rush|Gold Rush]].

Due to the opposition to Halloween by some people, there is a growing movement where people are inviting trick-or-treaters to take part by putting a balloon or decoration on their letter box, to indicate that they are welcome to come knocking. In the past decade, the popularity of Halloween in Australia has grown.<ref>{{cite web|url=http://www.abc.net.au/news/2015-10-30/love-it-or-hate-it-halloween-likely-to-continue-in-australia/6889420|title=Halloween: a festival that polarises Australians|date=30 October 2015|website=Abc.net.au|access-date=1 November 2017}}</ref> In 2020, Australia's first magazine dedicated solely to celebrating Halloween in Australia was launched, called Hallozween<ref>https://www.heraldsun.com.au/leader/west/halloween-2020-costumes-recipes-makeup-and-social-distancing/news-story/5eaa12c31a149d1ca3c70a98a4559a49</ref>, and in 2021, sales of costumes, decorations and carving pumpkins soared to an all-time high<ref>https://www.dailytelegraph.com.au/lifestyle/smart/top-tips-for-families-to-enjoy-a-healthy-and-safe-halloween/news-story/3847cac3f56b0c17ab7ad6d930138350</ref> despite the effect of the global [[COVID-19 pandemic|COVID-19]] pandemic limiting celebrations.

In New Zealand, as in neighbouring Australia, Halloween is not celebrated to the same extent as in North America, although in recent years the non-religious celebrations have been achieving some popularity especially among young children.<ref>{{cite web |url=http://www.kiwifamilies.co.nz/articles/halloween/ |title=Halloween in NZ |author=Kiwi Families |access-date=16 October 2014}}</ref><ref>{{cite web|url=http://my.christchurchcitylibraries.com/halloween/|title=Halloween|website=My.christchurchcitylibraries.com|access-date=1 November 2017}}</ref> Trick-or-treat has become increasingly popular with minors in New Zealand over the years, despite being not a "British or Kiwi event" that purely is only influenced by American globalization.<ref name="NZHeraldTrickTreat">{{Cite web |url=https://www.nzherald.co.nz/lifestyle/news/article.cfm?c_id=6&objectid=12151853 |title=Halloween trick or treating: How old is too old? Kiwi parents speak |website=NZ Herald |access-date=2018-11-01}}</ref> Critics of Halloween in New Zealand believe that commercialization of Halloween by the popular store [[The Warehouse]] has pushed the popularity of Halloween into an unofficial national holiday.<ref name="NZHeraldTrickTreat" />

==Europe==
[[File:Halloween! (15677234712).jpg|thumb|upright|A [[jack-o'-lantern]] in [[Finland]]]]
Over the years, Halloween has become more successful in Europe and has been partially ousting some older customs like the ''{{ill|Rübengeistern|de|display=y}}'' ({{lang-en|turnip ghosts, beet spirit}}), [[Martinisingen]], and others.<ref Name="Hör">Halloween in der Steiermark und anderswo, Volkskunde (Münster in Westfalen), Hrsg. Editha Hörandner, LIT Verlag Münster, 2005 {{ISBN|3825888894}}. {{in lang|de}}</ref>

===France===
Halloween has been introduced in France in the 1990's.

===Germany===
[[File:Hexenflug.jpg|thumb|upright|"Don't drink and fly" Halloween decoration in Germany]]
Halloween was not generally observed in Germany prior to the 1990s, but has been increasing in popularity. It has been associated with the influence of United States culture, and "Trick or Treating" (in German, ''"Süßes sonst gibt's Saures"'') has been occurring in various German cities, especially in areas such as the [[Dahlem (Berlin)|Dahlem]] neighborhood in Berlin, which was part of the American zone during the [[Cold War]]. Today, Halloween in Germany brings in 200 million euros a year, through multiple industries.<ref>{{Cite web|title = Das Geschäft mit dem Gruselfest: Aus Halloween wird Hallowahn - Stuttgarter Zeitung|url = http://www.stuttgarter-zeitung.de/inhalt.das-geschaeft-mit-dem-gruselfest-aus-halloween-wird-hallowahn.efeab0e3-fdb3-4035-b698-62048e30f267.html|website = stuttgarter-zeitung.de|access-date = 2015-10-31|language = de}}</ref> Halloween is celebrated by both children and adults. Adults celebrate at themed costume parties and clubs, while children go trick or treating. Complaints of vandalism associated with Halloween "Tricks" are increasing, particularly from many elderly Germans unfamiliar with "Trick or Treating".<ref>Rupert Neate and Nicholas Connolly (31 October 2013), [http://www.spiegel.de/international/zeitgeist/rise-of-halloween-culture-sees-backlash-in-germany-a-931005.html Holiday Backlash: Germans Cringe at Rise of Halloween] ''[[Der Spiegel]]''</ref>

===Greece===
In Greece, Halloween is a working day and was not celebrated much until interest began increasing in the early 2000s. It has continued to increase in popularity as both a commercial and secular celebration; although [[Carnival]] is more popular among Greeks, Halloween is now{{when|date=September 2021}} considered the fourth most profitable festival in the country after [[Christmas]], [[Easter]], and Carnival. Bars, nightclubs, and theme parks also organize Halloween parties. Its increase in popularity has been attributed to the influence of Western culture.

Since it is a working day, Halloween is not celebrated on 31st October unless the date falls on a weekend, in which case it is celebrated during the last weekend before [[All Hallow's Eve]]. Trick-or-treating is not widely popular because similar activities are already undertaken during Carnival. The rise in popularity of Halloween in Greece has led to an increase in its popularity throughout nearby countries such as [[Albania]], [[Bulgaria]], [[North Macedonia]], and [[Cyprus]]. In the latter, there has been an increase in [[Greek Cypriots|Greek-Cypriot]] retailers selling Halloween merchandise every year.<ref>https://cyprus-mail.com/2019/10/25/halloween-in-the-sun/</ref>

===Ireland===
[[File:Traditional Irish halloween Jack-o'-lantern.jpg|thumb|upright|A plaster cast of a traditional Irish turnip ([[rutabaga]]) jack-o'-lantern, ''c''. early 20th century, on display in the [[Museum of Country Life]], Ireland.]]
On Halloween night, adults and children dress up as various monsters and creatures, light bonfires, and enjoy fireworks displays; [[Derry]] in Northern Ireland is home to the largest organized Halloween celebration on the island, in the form of a street carnival and fireworks display.<ref>{{cite web|url=http://www.derrycity.gov.uk/halloween|title=Halloween 2007|work=Derrycity.gov.uk|access-date=31 October 2008|archive-url=https://web.archive.org/web/20080320043815/http://www.derrycity.gov.uk/halloween|archive-date=20 March 2008}}</ref>
[[File:maclise.snap.apple.night.jpg|thumb|left|''Snap-Apple Night'' (1832) by [[Daniel Maclise]] depicts [[apple bobbing]] and [[divination]] games at a Halloween party in Ireland]]

Games are often played, such as [[Apple bobbing|bobbing for apples]], in which apples, peanuts, other nuts and fruits, and some small coins are placed in a basin of water.<ref name=haggerty>{{cite web|url=http://www.irishcultureandcustoms.com/ACalend/Halloween1.html|title=An Irish Halloween - Part 1 - World Cultures European|website=Irishcultureandcustoms.com|access-date=1 November 2017}}</ref> Everyone takes turns catching as many items possible using only their mouths. Another common game involves the hands-free eating of an apple hung on a string attached to the ceiling. Games of divination are also played at Halloween.<ref>de Leary, Kim. "[http://www.startpage.ie/ireland/article/759.aspx Traditional Halloween Divination Games from Ireland]" ''www.startpage.ie''</ref> [[Colcannon]] is traditionally served on Halloween.<ref name=haggerty/>

31 October is the busiest day of the year for the [[Emergency Services]].<ref>{{cite news|title=Busy Halloween for emergency services|url=http://www.rte.ie/news/2011/1101/halloween.html|publisher=RTÉ|date=1 November 2011|access-date=1 November 2011}}</ref> [[Firecrackers|Bangers]] and [[fireworks]] are illegal in the [[Republic of Ireland]]; however, they are commonly smuggled in from [[Northern Ireland]] where they are legal.<ref>{{cite web|url=http://www.advertiser.ie/kilkenny/article/44718/gardai-warn-minors-to-stay-away-from-fireworks-following-haul|title=Gardai warn minors to stay away from fireworks following haul|publisher=Kilkenny Advertiser|date=30 September 2011|access-date=2 October 2011}}</ref> [[Bonfires]] are frequently built around Halloween.<ref>{{cite news|url=http://www.independent.ie/national-news/council-faces-euro1m-cleanup-bill-after-halloween-horror-2403219.html|title=Council faces €1m clean-up bill after Halloween horror|publisher=Irish Independent|date=2 November 2010|access-date=2 November 2010|first=Allison|last=Bray}}</ref> [[Trick-or-treating]] is popular amongst children on 31 October and Halloween parties and events are commonplace.

[[File:Pumpkin zucca Bono Sant'Andria.JPG|upright|thumb|A carved pumpkin in Sardinia]]

===Italy===
In Italy [[All Saints' Day]] is a public holiday. On 2 November, ''Tutti i Morti'' or [[All Souls' Day]], families remember loved ones who have died. These are still the main holidays.<ref>{{cite web|url=https://www.italiarail.com/halloween-italy|title=Halloween in Italy - ItaliaRail - Italy Train Ticket and Rail Pass Experts|website=Italiarail.com|access-date=1 November 2017}}</ref> In some Italian tradition, children would awake on the morning of All Saints or All Souls to find small gifts from their deceased ancestors. In Sardinia, ''Concas de Mortu'' (Head of the deads), carved pumpkins that look like skulls, with candles inside are displayed.<ref>{{cite web|author=Monia Melis |url=http://www.oggiviaggi.it/15067/tutte-le-halloween-della-sardegna |title=Tutte le Halloween della Sardegna |publisher=OggiViaggi.it |access-date=20 November 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131106103407/http://www.oggiviaggi.it/15067/tutte-le-halloween-della-sardegna/ |archive-date=6 November 2013 }}</ref><ref>{{cite web|author=Gian Luca Casu|url=http://sardegnaculturacolore.blogspot.it/2011/10/il-rito-de-is-fraccheras-un-rito-unico.html|title=Sardegna Cultura Colore: Il rito de "IS FRACCHERAS" un rito unico che si svolgeva in Sardegna il 2 Novembre nel piccolo paese chiamato Gadoni |publisher=Sardegnaculturacolore.blogspot.it|access-date=20 November 2013}}</ref><ref>{{cite web|url=http://www.goceano.it/paesi/bonofestasandrea.htm|title=C/O Comune di Bono – 07011 Bono (SS)|work=goceano.it|access-date=21 November 2013|url-status=dead|archive-url=https://web.archive.org/web/20020131225348/http://www.goceano.it/paesi/bonofestasandrea.htm|archive-date=31 January 2002|df=dmy-all}}</ref> Halloween is, however, gaining in popularity, and involves costume parties for young adults.<ref>[http://www.bestofsicily.com/mag/art179.htm Paglia, Roberto. "Saints and Souls", ''Best of Sicily Magazine'', 2005]</ref> The traditions to carve pumpkins in a skull figure, lighting candles inside, or to beg for small gifts for the deads e.g. sweets or nuts, also belong to [[North Italy]].<ref>{{cite web|url=http://www.focus.it/ambiente/quali-sono-le-halloween-italiane|title=Quali sono le Halloween italiane?|website=Focus.it|access-date=1 November 2017}}</ref> In [[Veneto]] these carved pumpkins were called ''lumère'' (lanterns) or ''suche dei morti'' (deads' pumpkins).<ref>{{cite web|url=http://www.veneziatoday.it/cronaca/veneto-festival-spettacoli-mistero-halloween.html|title=Dalle "lumère" alle famose zucche, il Veneto ritrova il suo Halloween|website=Veneziatoday.it|access-date=1 November 2017}}</ref>

===Poland ===
Since the [[fall of Communism]] in 1989, Halloween has become increasingly popular in Poland. Particularly, it is celebrated among younger people. The influx of Western tourists and expats throughout the 1990s introduced the costume party aspect of Hallowe'en celebrations, particularly in clubs and at private house parties. Door-to-door trick or treating is not common. Pumpkin carving is becoming more evident, following a strong North American version of the tradition.

===Romania===
Romanians observe the [[St. Andrew's Day|Feast of St. Andrew]], patron saint of Romania, on 30 November. On St. Andrew's Eve ghosts are said to be about. A number of customs related to divination, in other places connected to Halloween, are associated with this night.<ref>{{cite web|url=http://traditionsacrosseurope.wordpress.com/2008/11/25/st-andrews-day-in-romania/ |title=St. Andrew's Day in Romania |publisher=Traditionsacrosseurope.wordpress.com |date=2008-11-25 |access-date=2013-09-06}}</ref> However, with the popularity of Dracula in western Europe, around Halloween the Romanian tourist industry promotes trips to locations connected to the historical [[Vlad the Impaler|Vlad Tepeș]] and the more fanciful Dracula of [[Bram Stoker]]. One of the most successful Halloween Parties in Transylvania takes place in [[Sighișoara]], the citadel where Vlad the Impaler was born. This party include magician shows, ballet show and The Ritual Killing of a Living Dead<ref>{{cite web|url=http://www.visit-transylvania.co.uk/romania-travel-transylvania/halloween-party-transylvania.html|title=Transylvania Live – Awarded Halloween in Transylvania Party, Halloween Short Break, Dracula Short Break, Romania travel|publisher=Visit-transylvania.co.uk|access-date=20 November 2013}}</ref>The biggest Halloween party in Transylvania take place at Bran Castle, aka Dracula's Castle from Transylvania.<ref>{{cite web|url=https://halloween-party-at-draculas-castle-in-transylvania.business.site/|title=Bran Castle Halloween Party|publisher=Bran Castle Party planner|access-date=12 February 2020}}</ref>

Both the Catholic and Orthodox Churches in Romania discourage Halloween celebrations, advising their parishioners to focus rather on the "Day of the Dead" on 1 November, when special religious observances are held for the souls of the deceased.<ref>{{cite web|url=http://stirileprotv.ro/stiri/actualitate/bisericiile-din-romania-s-au-unit-impotriva-sarbatorii-de-halloween-nu-putem-petrece-de-ziua-mortilor.html|title=Bisericiile din Romania s-au unit impotriva sarbatorii de Halloween. Nu putem petrece de "Ziua Mortilor"|website=Stirileprotv.ro|access-date=1 November 2017}}</ref> Opposition by religious and nationalist groups, including calls to ban costumes and decorations in schools in 2015, have been met with criticism.<ref>{{cite web | url=http://www.hotnews.ro/stiri-esential-20543341-controversa-halloween-scoli-asociatia-parinti-pentru-ora-religie-lupta-dovlecii-vrea-scoata-vrajitoarele-din-clase.htm | title=Controversa de Halloween in scoli: Asociatia Parinti pentru Ora de Religie se lupta cu dovlecii si vrea sa scoata vrajitoarele din clase|website=Hotnews.ro | access-date=1 November 2015| date=30 October 2015}}</ref><ref>{{cite web | url=http://www.hotnews.ro/stiri-esential-20543148-scrisoarea-unui-tatic-vrajitoare-catre-parintii-care-interzis-copiilor-halloween-temeti-inocenta-care-arata-asa-cum-sunteti-habotnici-razbunatori.htm | title=Scrisoarea unui tatic de Vrajitoare, catre parintii care le-au interzis copiilor Halloween-ul: Va temeti de inocenta care va arata asa cum sunteti. Habotnici si razbunatori!|website=Hotnews.ro | access-date=1 November 2015| date=30 October 2015}}</ref><ref>{{cite web | url=http://www.hotnews.ro/stiri-esential-20543967-romania-linie-bulgaria-rusia-tarile-care-sperie-halloween-vad-aceasta-sarbatoare-forma-colonizare-culturala.htm | title=Romania, in linie cu Bulgaria si Rusia. Tarile care se sperie de Halloween si vad in aceasta sarbatoare "o forma de colonizare culturala" | access-date=1 November 2015| date=30 October 2015 }}</ref> Halloween parties are popular in bars and nightclubs.<ref>{{cite web | url=http://www.realitatea.net/halloween-in-romania-unde-te-poti-distra_1820459.html | title=Halloween în România. Unde te poţi distra | access-date=1 November 2015}}</ref>

===Russia===
In Russia most Christians are Orthodox, and in the Orthodox Church Halloween is on the Saturday after Pentecost and therefore 4 to 5 months before western Halloween. Celebration of western Halloween began in the 1990s around the downfall of the Soviet regime, when costume and ghoulish parties spread throughout night clubs throughout Russia. Halloween is generally celebrated by younger generations and is not widely celebrated in civic society (e.g. theaters or libraries). In fact, Halloween is among the Western celebrations that the Russian government and politicians—which have grown increasingly anti-Western in the early 2010s—are trying to eliminate from public celebration.<ref>{{cite magazine|last1=Shuster|first1=Simon|title=Russian Region Wages War on Halloween|url=http://world.time.com/2013/10/31/halloween-extremist-says-russian-region-enacting-ban/|magazine=Time|access-date=24 October 2014|date=31 October 2013}}</ref><ref>{{cite news|last1=Bennetts|first1=Marc|title=Nyet on Halloween: Russian church warns of 'dangers'; Siberia bans holiday|url=http://www.washingtontimes.com/news/2013/oct/30/authorities-warn-russians-dangers-halloween/|access-date=24 October 2014|work=Washington Times|date=30 October 2013}}</ref><ref>{{cite news|title=Russia: Activist calls for Halloween ban|url=https://www.bbc.com/news/blogs-news-from-elsewhere-29742511|access-date=24 October 2014|work=BBC News|date=23 October 2014}}</ref>

===Serbia===
Halloween ({{lang-sr-Cyrl|Ноћ вештица}}, lit. "Night of Witches") has not been celebrated until recently. Halloween is a work day in [[Serbia]]. Nowadays, it is very popular among younger generations. Many schools (mostly elementary schools) in Serbia throw special Halloween parties, full of children and teenagers wearing costumes and masks. Bars, nightclubs and fun parks organise Halloween parties for adults and young adults.

=== Spain===

In Spain, celebrations involve eating castanyes (roasted [[chestnut]]s), [[panellet]]s (special almond balls covered in pine nuts), moniatos (roast or baked [[sweet potato]]), Ossos de Sant cake and preserved fruit ([[Candied fruit|candied]] or [[Glacé|glazed fruit]]). [[Moscatell]] (Muscat) is drunk from [[porron]]s.<ref>{{Cite news|url=https://anglophone-direct.com/la-castanyada/|title=LA CASTANYADA {{!}} P-O Life|date=2017-10-24|work=anglophone-direct|access-date=2018-10-14|language=en-GB}} {{verify source |date=September 2019 |reason=This ref was deleted Special:Diff/901651330 by a bug in VisualEditor and later restored by a bot from the original cite located at Special:Permalink/886800512 cite #1 - verify the cite is accurate and delete this template. [[User:GreenC bot/Job 18]]}}</ref> Around the time of this celebration, it is common for [[street vendor]]s<nowiki/> to sell hot toasted chestnuts wrapped in [[newspaper]]. In many places, [[confectioner]]s often organise [[raffle]]s of chestnuts and preserved fruit.

The tradition of eating these foods comes from the fact that during [[All Saints' Day|All Saints']] night, on the eve of [[All Souls' Day]] in the [[Christianity|Christian]] tradition, [[bell ringer]]s would ring bells in commemoration of the dead into the early morning. Friends and relatives would help with this task, and everyone would eat these foods for sustenance.<ref>{{Cite news|url=https://anglophone-direct.com/la-castanyada/|title=LA CASTANYADA {{!}} P-O Life|date=2017-10-24|work=anglophone-direct|access-date=2018-10-14|language=en-GB}} {{verify source |date=September 2019 |reason=This ref was deleted Special:Diff/901651330 by a bug in VisualEditor and later restored by a bot from the original cite located at Special:Permalink/886800512 cite #2 - verify the cite is accurate and delete this template. [[User:GreenC bot/Job 18]]}}</ref>

Other versions of the story state that the Castanyada originates at the end of the 18th century and comes from the old funeral meals, where other foods, such as [[vegetable]]s and dried fruit were not served. The meal had the symbolic significance of a communion with the souls of the departed: while the chestnuts were roasting, prayers would be said for the person who had just died.<ref>Soler i Amigó, 2001, p. 200. {{verify source |date=September 2019 |reason=This ref was deleted Special:Diff/901651330 by a bug in VisualEditor and later restored by a bot from the original cite located at Special:Permalink/886800512 cite #3 - verify the cite is accurate and delete this template. [[User:GreenC bot/Job 18]]}}</ref>

The festival is usually depicted with the figure of a ''castanyera'': an old lady, dressed in peasant's clothing and wearing a [[headscarf]], sitting behind a table, roasting chestnuts for street sale.

In recent years, the Castanyada has become a [[Verbena (fair)|''revetlla'']] of All Saints and is celebrated in the home and community. It is the first of the four main school festivals, alongside [[Christmas]], [[Carnestoltes]] and [[St George's Day]], without reference to ritual or commemoration of the dead.<ref>Soler i Amigó, 2001, p. 201. {{verify source |date=September 2019 |reason=This ref was deleted Special:Diff/901651330 by a bug in VisualEditor and later restored by a bot from the original cite located at Special:Permalink/886800512 cite #4 - verify the cite is accurate and delete this template. [[User:GreenC bot/Job 18]]}}</ref>

=== Sweden ===
On All Hallow's Eve, a [[Requiem Mass]] is widely attended every year at [[Uppsala Cathedral]], part of the Lutheran [[Church of Sweden]].<ref name="VlasBoari2013">{{cite book|title=Religion and Politics in the 21st Century: Global and Local Reflections|last1=Vlas|first1=Natalia|last2=Boari|first2=Vasile|date=2013|publisher=Cambridge Scholars Publishing|isbn=9781443850766|language=en}}</ref>

Throughout the period of Allhallowtide, starting with All Hallow's Eve, Swedish families visit churchyards and adorn the graves of their family members with lit candles and wreaths fashioned from pine branches.<ref name="VlasBoari2013" />

Among children, the practice of dressing in costume and collecting candy gained popularity beginning around 2005.<ref name="Phil2016">{{cite web|url=http://www.relocatetosweden.com/en/halloween-first-time-trick-treating-sweden/|title=Halloween – my first time trick-or-treating in Sweden|last1=Pihl|first1=Anne|date=28 October 2016|website=Relocate To Sweden|archive-url=https://web.archive.org/web/20180708221025/https://relocatetosweden.com/en/halloween-first-time-trick-treating-sweden/|archive-date=2018-07-08|url-status=dead}}</ref> The American traditions of Halloween have however been met with skepticism among the older generations, in part due to conflicting with the Swedish traditions on All Hallow's Eve and in part due to their commercialism.<ref>{{cite web|title=Halloween|url=https://www.isof.se/folkminnen/handelser-i-almanackan/kalender/i-almanackan/handelser-i-almanackan/2020-10-31-halloween.html|website=isof.se|language=sv|publisher=[[Swedish Institute for Language and Folklore]]|date=19 October 2020|archive-url=https://web.archive.org/web/20210228002548if_/https://www.isof.se/folkminnen/handelser-i-almanackan/kalender/i-almanackan/handelser-i-almanackan/2020-10-31-halloween.html|archive-date=2021-02-28|url-status=dead}}</ref>

=== Switzerland ===
In [[Switzerland]], Halloween, after first becoming popular in 1999, is on the wane, and is most popular with young adults who attend parties. Switzerland already has a "festival overload" and even though Swiss people like to dress up for any occasion, they do prefer a traditional element, such as in the [[Fasnacht]] tradition of chasing away winter using noise and masks.<ref>{{cite web|url=http://www.swissinfo.ch/eng/Home/Archive/Halloween_retailers_get_a_shock.html?cid=6223458|title=Interest in Halloween in Switzerland starts to wane|work=Swissinfo.ch|date=31 October 2007|access-date=1 November 2012}}</ref><ref>[http://lenews.ch/2014/10/30/halloween-in-switzerland/ Taylor, Pamela. "Halloween in Switzerland", ''Le News'', 30 October 2014]</ref>

===United Kingdom and Crown dependencies===

====England====
{{See also|Mischief Night}}
In the past, on All Souls' Eve families would stay up late, and little "soul cakes" were eaten. At the stroke of midnight, there was solemn silence among households, which had candles burning in every room to guide the souls back to visit their earthly homes and a glass of wine on the table to refresh them. The tradition of giving soul cakes that originated in Great Britain and Ireland was known as [[souling]], often seen as the origin of modern [[trick or treating]] in North America, and souling continued in parts of England as late as the 1930s, with children going from door to door singing songs and saying prayers for the dead in return for cakes or money.<ref name=AFP>{{cite book|first=Nicholas|last=Rogers|title=Halloween: From Pagan Ritual to Party Night|url=https://archive.org/details/halloweenfrompag00roge|url-access=registration|publisher=Oxford University Press|year=2002|pages=[https://archive.org/details/halloweenfrompag00roge/page/n37 28]–30|isbn=0-19-514691-3}}</ref>

Trick or treating and other Halloween celebrations are extremely popular, with shops decorated with witches and pumpkins, and young people attending costume parties.<ref>[http://www.smithsonianmag.com/history/how-halloween-has-taken-over-england-180953211/?no-ist Hanc, John. "How Halloween Has Taken Over England", ''Smithsonian Magazine'', 31 October 2014]</ref>

====Scotland====
The name ''Halloween'' is first attested in the 16th century as a Scottish shortening of the fuller ''All-Hallow-Even'', that is, the night before All Hallows' Day.<ref name="OED">{{cite OED|Hallow-e'en}}</ref> [[Dumfries]] poet [[John Mayne]]'s 1780 poem made note of pranks at Halloween "What fearfu' pranks ensue!". Scottish poet [[Robert Burns]] was influenced by Maynes composition, and portrayed some of the customs in his poem ''[[Halloween (poem)|Halloween]]'' (1785).<ref name=cham>{{cite book|first=Robert|last=Chambers|url=https://archive.org/details/lifeandworksrob02chamgoog|page=[https://archive.org/details/lifeandworksrob02chamgoog/page/n165 154]|quote=halloween poem (burns).|title=The life and works of Robert Burns, Volume 1|publisher=Lippincott, Grambo & co.|year=1854}}</ref> According to Burns, Halloween is "thought to be a night when witches, devils, and other mischief-making beings are all abroad on their baneful midnight errands".<ref>{{cite book|url=https://books.google.com/books?id=y9A0uAW929EC&q=thought+to+be+a+night+when+witches%2C+devils%2C+and+other+mischief-making+beings&pg=PA342 |title=The Penny Cyclopaedia of the Society for the Difussion of Useful Knowledge|publisher=Charles Knight|year=1833 |access-date=21 November 2013}}</ref>

Among the earliest record of Guising at Halloween in Scotland is in 1895, where masqueraders in disguise carrying lanterns made out of scooped out turnips, visit homes to be rewarded with cakes, fruit and money.<ref>{{cite book|url=https://books.google.com/books?id=x7_QAAAAMAAJ&q=Frank%20Leslie's%20popular%20monthly%201895%20Halloween&pg=PA540 |title=Frank Leslie's Popular |publisher= Frank Leslie's|date=1895|access-date=21 November 2013}}</ref> If children approached the door of a house, they were given offerings of food. The children's practice of "[[Trick-or-treating#Guising|guising]]", going from door to door in costumes for food or coins, is a traditional Halloween custom in Scotland.<ref name=ATP>{{cite book|last=Rogers|first=Nicholas|year=2002|chapter=Festive Rights: Halloween in the British Isles|title=Halloween: From Pagan Ritual to Party Night|url=https://archive.org/details/halloweenfrompag00roge|url-access=registration|pages=[https://archive.org/details/halloweenfrompag00roge/page/n58 49]–77|publisher=Oxford University Press|isbn=0195146913}}</ref> These days children who knock on their neighbours doors have to sing a song or tell stories for a gift of sweets or money.<ref>{{cite web|url=http://www.scotland.org/features/halloween-traditions/|title=Halloween Traditions|website=Scotland.org|access-date=1 November 2017}}</ref>

A traditional Halloween game includes apple "[[Apple bobbing|dooking]]",<ref>{{cite web|url=http://news.bbc.co.uk/1/hi/scotland/south_of_scotland/7648188.stm |title=Apple dookers make record attempt |work=BBC News |date=2 October 2008 |access-date=21 November 2013}}</ref> or "dunking" or (i.e., retrieving one from a bucket of water using only one's mouth), and attempting to eat, while blindfolded, a [[treacle]]/[[jam]]-coated [[scone (bread)|scone]] hanging on a piece of string.

Traditional customs and [[folklore|lore]] include [[divination]] practices, ways of trying to predict the future. A traditional Scottish form of divining one's future spouse is to carve an apple in one long strip, then toss the peel over one's shoulder. The peel is believed to land in the shape of the first letter of the future spouse's name.<ref>{{cite book|last=McNeill|first=F. Marian|year=1961|title=The Silver Bough, Vol. 3|publisher=William MacLellan|location=Glasgow|isbn=0-948474-04-1|pages=11–46}}</ref>

In [[Kilmarnock]], Halloween is also celebrated on the last Friday of the month, and is known colloquially as "Killieween".<ref>{{cite web|url=https://www.scotsman.com/regions/glasgow-and-strathclyde/why-one-town-scotland-celebrates-halloween-today-1404215 |title=Why one town in Scotland celebrates Halloween today |work=The Scotsman |date=25 October 2019 |access-date=22 October 2021}}</ref>

====Isle of Man====
''See [[Hop-tu-Naa]]''.

Halloween is a popular traditional occasion on the [[Isle of Man]], where it is known as Hop-tu-Naa.

==Elsewhere==
[[File:Bonaire Holloween.jpg|thumb|right|The children of the largest town in [[Bonaire]] gather together on Halloween day.]]

===Saint Helena===
In [[Saint Helena]], Halloween is actively celebrated, largely along the American model, with ghosts, skeletons, devils, vampires, witches and the like. Imitation pumpkins are used instead of real pumpkins because the pumpkin harvesting season in Saint Helena's hemisphere is not near Halloween. Trick-or-treating is widespread. Party venues provide entertainment for adults.<ref>{{cite news|url=http://www.saint.fm/Independent/20091030.pdf|title=Entertainment & Events|publisher=St Helena Independent|date=30 October 2009|access-date=30 October 2009|archive-url=https://web.archive.org/web/20110720172608/http://www.saint.fm/Independent/20091030.pdf|archive-date=20 July 2011}}</ref>

{{-}}

==See also==
* [[Festival of the Dead]]
* [[Halloween#Games and other activities|Games and other activities during Halloween]]
{{portalbar|Holidays}}

==References==
{{Reflist}}

==Further reading==
* [https://web.archive.org/web/20141031081252/http://news.blogs.wlu.edu/2014/10/28/what-halloween-can-learn-from-history/ Brock, Michelle. "What Halloween Can Learn from History"]

{{Halloween| state=expanded}}

{{DEFAULTSORT:Geography of Halloween}}
[[Category:Halloween]]
[[Category:Human geography]]
[[Category:Allhallowtide]]