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 engines. It is colorless to straw-colored in appearance. The most commonly used fuels for commercial a ...

originally developed in 1956 for the

Lockheed U-2 The Lockheed U-2, nicknamed "''Dragon Lady''", is an American single-jet engine, high altitude reconnaissance aircraft operated by the United States Air Force (USAF) and previously flown by the Central Intelligence Agency (CIA). It provides day ...

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 service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Sign ...

Captain assigned to the Fuels Branch was instructed to buy a

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

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 Charcoal lighter fluid is a flammable fluid used to accelerate the ignition of charcoal in a barbecue grill. It can either be petroleum based (e.g., mineral spirits) or alcohol based (usually methanol or ethanol). It can be used both with lump ch ...

(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". (EN 60079-10-1) The fl ...

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

flammability limit Mixtures of dispersed combustible materials (such as gaseous or vaporised fuels, and some dusts) and oxygen in the air will burn only if the fuel concentration lies within well-defined lower and upper bounds determined experimentally, referred to a ...

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

specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water (molecule), wa ...

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 The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inte ...

, 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 corrosio ...

. 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