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V-1 flying bomb

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V1
File:V1 flying bomb.jpg
V1 flying bomb
First modern cruise missile
Description
RoleFlying bomb
Crewnone
Dimensions
Length7.90 m25' 11"
Wingspan5.37 m17' 7"
Height1.42 m4' 8"
Wing area
Weights
Empty
Loaded2,150 kg4,750 lb
Powerplant
Engine1x Argus As 14 pulsejet
Power2.9 kN660 lb
Performance
Maximum speed656 km/h410 mph
Range240 km150 mile
Service ceiling3,050 m10,000 ft
Rate of Climb
Armament
Amatol warhead830 kg1,832 lb

The Vergeltungswaffe 1 FZG-76 (V1), known as the Flying Bomb, Buzz Bomb or Doodlebug, was the first modern guided missile used in wartime and the first cruise missile. Vergeltungswaffe means "reprisal weapon", and FZG is an abbreviation of Flak Ziel Gerät ("anti-aircraft aiming device"), a misleading name.

Called the Buzz Bomb because of the characteristic buzzing sound of the engine, it caused considerable fear in targeted areas. People would listen for the missile approaching, but then be relieved when it could be heard overhead as that meant it had actually passed them. If the engine noise cut out, it was time to duck, as the missile would then go into its terminal dive.

The V1 was developed in Germany during the Second World War and was used operationally between June 1944 and March 1945. It was used to attack targets in south-eastern England and Belgium, mainly the cities of London and Antwerp. V1s were launched from "ski-jump" launch sites along the French (Pas-de-Calais) and Dutch coasts until they were over-run by Allied forces. It was later complemented by the more sophisticated V2 rocket.

Description

The V1 was jointly designed by Robert Lusser of the Fieseler company and Fritz Gosslau from the Argus engine works as the Fi 103. It was powered by an Argus pulse jet engine providing 2.9 kN (660 pounds) of thrust for a top speed of 630 km/h (390 mph) and a range of around 250 km (150 mile) later 400 km (250 mile). It was 7.9 m (26 ft) long, 5.3 m (17 ft) in span and weighed 2,180 kg (4,800 pound). It flew at an altitude of between 100 to 1000 m (300 to 3000 ft). It carried a 850 kg (1,870 pound) warhead. The missile was a relatively simple device with a fuselage constructed mainly from sheet metal, and could be assembled in around fifty man-hours.

The guidance system was very crude in construction but sophisticated in conception (and had a few flaws in execution). Once clear of the launching pad, an autopilot was engaged. It regulated height and speed together, using a weighted pendulum system to get fore and aft feedback linking these and the device's attitude to control its pitch (damped by a gyromagnetic compass, which it also stabilized). There was a more sophisticated interaction between yaw, roll, and other sensors: a gyromagnetic compass (set by swinging in a hangar before launch) gave feedback to control each of pitch and roll, but it was angled away from the horizontal so that controlling these degrees of freedom interacted (the gyroscope stayed trued up by feedback from the magnetic field, and from the fore and aft pendulum mentioned before). This interaction meant that rudder control was sufficient without any separate banking mechanism. On reaching the target, the desired altitude was reset to be negative; this should have led to a power dive, but the steep descent caused the fuel to run away from the pipes and so the power cut out. As there was a belly fuse as well as a nose fuse, there was still usually an explosion, although not always with the device buried deep enough to increase the effect of the blast.

Operation and impact

The first test flight of a V1 was in late 1941 or early 1942 at Peenemünde. Early guidance and stabilization problems were finally resolved by a daring test flight by Hanna Reitsch, in a V1 modified for manned operation. The data she brought back after fighting the unwieldy V1 down to a successful landing enabled the engineers to devise the stabilization system described above.

The first offensive launch was on June 12, 1944. The Allies organized a heavy series of air attacks on the launch sites and also attacked the V1s in flight (see Countermeasures below). Due to a combination of defensive measures, mechanical unreliability and guidance errors, only a quarter successfully hit their targets.

Once the Allies had captured or destroyed the sites that were the principal launch points V1s aimed at England, the Germans switched to missile launches aimed at strategic points in the Low Countries, primarily the port of Antwerp.


Final dive of a V1

Although most V1s were launched from static sites on land, from July 1944 to January 1945 the Luftwaffe launched a number of V1s from Heinkel He 111 aircraft flying over the North Sea. This would also have been the launch method for the proposed piloted version of the weapon. Late in the war, it was hoped to use the Arado Ar 234 jet bomber to deploy V1s, either by towing them aloft, or by launching them from a "piggy back" position atop the aircraft. Neither Ar 234 concept was employed before the end of the war.

Almost 30,000 V1s were manufactured. Approximately 10,000 were fired at England up to March 29, 1945. Of these, about 7,000 were "hits" in the sense that they landed somewhere in England. A little more than half of those (3,876) landed in the Greater London area.

An almost equal number were shot down or intercepted by barrage balloons. When the V1 raids began, the only effective defense was interception by a handful of very high performance fighter aircraft, in particular the Hawker Tempest.

In the London area, roughly 5,500 people died as a result of V1 attacks, with some 16,000 more people injured.

Countermeasures

Anti-aircraft gunners found that such small, fast-moving targets were difficult to hit. At first, it took, on average, 2500 shells to bring down a single V1. Most fighter aircraft were too slow to catch a V1 unless they had a useful height advantage. Even when caught, the V1 was difficult to bring down. Machine gun bullets had little effect on the sheet steel structure, and 20mm cannon shells had a shorter range, which meant that detonating the warhead could easily destroy the intercepting fighter as well. Barrage balloons were a theoretical obstacle, but the leading edges of the V1's wings were equipped with balloon cable cutters and fewer than 300 V1s are known to have been destroyed by hitting cable.

When the attacks began in mid-June of 1944 there were fewer than 30 Tempests in 150 Wing to defend against them. Few other aircraft had the low altitude performance to be effective. Initial attempts to intercept V1s were often unsuccessful but interdiction techniques were rapidly developed. (These included the hair-raising but effective method of using the airflow over an interceptor's wing to raise one wing of the Doodlebug, by sliding the interceptor's wingtip under the V1's wing and bringing it to within six inches of the lower surface. Done properly, the airflow would tip the V1's wing up, overriding the buzz bomb's gyros and sending it into an out of control dive. At least three V1s were destroyed this way.)

The Tempest wing was built up to over 100 aircraft by September; Griffin-engined Spitfire XIVs and Mustangs were polished and tuned to make them almost fast enough, and during the short summer nights the Tempests shared defensive duty with Mosquitoes. Specially modified P-47 Thunderbolts (P-47Ms) with half their fuel tanks, half their 0.5 in (12.7 mm) machine guns, all external fittings and all their armor plate removed were also pressed into service against the V1 menace. (There was no need for radar - at night the V1's engine could be seen from 16 km (10 mile) or more away.)

In daylight, V1 chases were chaotic and often unsuccessful until a special defence zone between London and the coast was declared in which only the fastest fighters were permitted. Between June and mid-August 1944, the handful of Tempests shot down 638 flying bombs. (One Tempest pilot, Joseph Berry, downed fifty-nine V1s, another 44, and Wing Commander Beaumont destroyed 31.) Next most successful was the Mosquito (428), Spitfire XIV (303), and Mustang, (232). All other types combined added 158. The still-experimental jet-powered Gloster Meteor, which was rushed half-ready into service to fight the V1s, had ample speed but suffered from a readily jammed cannon and accounted for only 13.

By mid-August 1944, the threat was all but overcome - not by aircraft, but by the sudden arrival of two enormously effective electronic aids for anti-aircraft guns, both developed in the USA by the Rad Lab: radar-based automatic gunlaying, and above all, the proximity fuse. Within weeks, the vast majority of V1s launched were shot down by anti-aircraft guns as they crossed the coast. The kill rate increased from one V1 for every 2500 shells fired to one for every hundred.