Jet Propellant Thermally Stable (JPTS) is a

jet fuel Jet fuel or aviation turbine fuel (ATF, also abbreviated avtur) is a type of aviation fuel designed for use in aircraft powered by Gas turbine, gas-turbine engines. It is colorless to straw-colored in appearance. The most commonly used fuels for ...

originally developed in 1956 for the

Lockheed U-2 The Lockheed U-2, nicknamed the "''Dragon Lady''", is an American single-engine, high–altitude reconnaissance aircraft operated by the United States Air Force (USAF) and the Central Intelligence Agency (CIA) since the 1950s. Designed for all- ...

reconnaissance aircraft.

History

Because of tight security restrictions enforced during the U-2's development, batches of fuel that were delivered to the aircraft's engine manufacturer were initially labeled LF-1. In 1956, a year after the U-2's first flight, a

USAF The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its ori ...

Captain assigned to the Fuels Branch was instructed to buy a

tank car A tank car (International Union of Railways (UIC): tank wagon) or tanker is a type of railroad car (UIC: railway car) or rolling stock designed to transport liquid and gaseous commodity, commodities. History Timeline The following major event ...

load of LF-1 and have it shipped to an engine manufacturer. Not knowing what LF-1 was, he obtained a sample, had it analyzed, and determined that it was paraffinic kerosene, a fluid commonly known as charcoal lighter fluid (hence LF-1). Specification MIL-T-25524 was later written to include an additive for improving JPTS' thermal oxidative stability.

Properties

JPTS has a

flash point The flash point of a material is the "lowest liquid temperature at which, under certain standardized conditions, a liquid gives off vapours in a quantity such as to be capable of forming an ignitable vapour/air mixture". The flash point is somet ...

of 43 °C (110 °F), a freezing point of -53 °C (-64 °F) and

flammability limit Flammability limits or explosive limits are the ranges of fuel concentrations in relation to oxygen from the air. Combustion can range in violence from deflagration through detonation. Limits vary with temperature and pressure, but are normally ...

s of 1 and 6 %. It has an appearance of a water-white clear liquid with

specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

of 0.816. It is insoluble in water. It is composed of a complex mixture of petroleum hydrocarbons. JPTS has a lower freeze point, lower

viscosity Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for e ...

, and higher thermal stability than standard aviation fuels. The fuel's low viscosity is needed to overcome the risk of it freezing in the low temperatures encountered during flight at high altitudes. JPTS also serves as coolant of engines and aerodynamically heated surfaces. As the fuel flow to the U-2's engines at cruise altitudes is about sixteen times lower than at sea level, the dwell time over hot surfaces is longer and increases the chances of thermal breakdown; JTPS's high thermal stability is therefore desired to avoid coking and deposition of varnishes in the piping. JPTS is a specialty fuel and is produced by only two oil refineries in the United States. As such, it has limited worldwide availability and costs over three times the per-gallon price of the Air Force's primary jet fuel,

JP-8 JP-8, or JP8 (for "Jet Propellant 8"), is a jet fuel, specified and used widely by the US military. It is specified by MIL-DTL-83133 and British Defence Standard 91-87, and similar to commercial aviation's Jet A-1, but with the addition of corros ...

. Research is under way to find a cheaper and easier alternative involving additives to generally used jet fuels. A JP-8 based alternative, JP-8+100LT, is being considered. JP-8+100 has increased thermal stability by 100 degrees F more than stock JP8, and is only 0.5 cents per gallon more expensive; low temperature additives can be blended to this stock to add the desired cold performance.

History

Properties

References

See also