Shell Oil developed JP-7 in 1955. Manufacturing several hundred thousand gallons of the new fuel required the petroleum byproducts Shell normally used to make its Flit insecticide, causing a nationwide shortage of that product!
The legendary SR-71 Blackbird aircraft was powered by two 34,000 lbf (151,240 N) thrust-class J58 afterburning turbojet engines. Each engine contained a nine-stage compressor driven by a two-stage turbine. The main burner used an eight-can combustor and the afterburner is fully modulating. The primary nozzle area was variable. Above Mach 2.2, some of the airflow was bled from the fourth stage of the compressor and dumped into the augmentor inlet through six bleed-bypass tubes, circumventing the core of the engine and transitioning the propulsive cycle from a pure turbojet to a turbo-ramjet. The engine was hydromechanically controlled and burns a special low volatility jet fuel mixture known as JP7.
‘Noteworthy, JP7 production caused a nationwide shortage of bug spray,’ says our friend Linda Sheffield Miller (Col Richard (Butch) Sheffield’s daughter, Col. Sheffield was an SR-71 Reconnaissance Systems Officer) on her Facebook Page Habubrats.
“The operating envelope of the [J58] 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 [nb 1] (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,” SR-71A Flight Manual states.
Sheffield Miller explains;
‘Shell Oil developed JP-7 in 1955. Company vice president Jimmy Doolittle arranged for Shell to develop the fuel for the Central Intelligence Agency (CIA) and United States Air Force’s (USAF) secret Lockheed U-2 spy plane, which needed a low-volatility fuel that would not evaporate at high altitude. Manufacturing several hundred thousand gallons of the new fuel required the petroleum byproducts Shell normally used to make its Flit insecticide, causing a nationwide shortage of that product!
‘One of the ingredients in JP7 just so happened to be a crucial part of Flit mosquito repellant. Bearing in mind the huge amount of fuel we’re talking about here, Shell didn’t exactly have enough supply to meet the newly increased demand, so mosquitos everywhere caught a lucky break!’
Sheffield Miller concludes;
‘JP7 Had a high flashpoint was not flammable, every time an SR 71 needed fuel …tankers were always there, they were terrific and deserve high praise.’
Photo credit: NASA and U.S. Air Force