JP-7
JP-7 (Jet Propellant 7, MIL-T-38219) is a fuel developed by the U.S. Air Force for use in supersonic aircraft because of its high flashpoint and thermal stability. JP-7 is a compound composed primarily of hydrocarbons, including alkanes, cycloalkanes, alky-benzenes, indan/tetralins, and naphthalenes. It is the fuel used in the Lockheed SR-71 Blackbird.
Properties
- Melting Point −30 °C
- Boiling Point (1 atm) 182–288 °C
- Density (at 15 °C) 779–806 kg/m³
- Vapor Pressure (at 300 °F (149 °C)) 155 mmHg (20.7 kPa)
- Flashpoint 60 °C
From the SR-71 Flight Manual:
“The operating envelope of the JT11D-20 engine requires special fuel. The fuel is not only the source of energy but is also used in the engine hydraulic system. During high Mach flight, the fuel is also a heat sink for the various aircraft and engine accessories which would otherwise overheat at the high temperatures encountered. This requires a fuel having high thermal stability so that it will not break down and deposit coke and varnishes in the fuel system passages. A high luminometer number (brightness of flame index) is required to minimize transfer of heat to the burner parts. Other items are also significant, such as the amount of sulfur impurities tolerated. Advanced fuels, JP-7 (PWA 535) and PWA 523E, were developed to meet the above requirements.”