The J85 was originally designed to power a large decoy missile, the McDonnell ADM-20 Quail. The Quail was designed to be released from a B-52 Stratofortess in-flight and fly for long distances alongside the launch aircraft effectively multiplying the number of targets facing enemy surface-to-air missile operators on the ground. This mission demanded a small engine that could nevertheless provide enough power to keep up with the jet bomber.
The engine was a success on the Quail and was subsequently used to power other small jet aircraft including the Northrop T-38 Talon and F-5, Canadair CT-114 Tutor, and Cessna A-37 Dragonfly. More recently, J85s have powered the Scaled Composites’ White Knight aircraft (the carrier for the Scaled Composites’ Space Ship One spacecraft), and the Me 262 Project.
The basic engine design is quite small, about 18 inches in diameter, and 45 inches long. It features an eight-stage axial-flow compressor powered by two turbine stages, and is capable of generating up to 2,950 lb of dry thrust, or more with an afterburner. Weighing in at only about 400 lbs, the J85 offers the highest thrust-to-weight ratio of any production engine in its class in the free world.
General Electric built more than 12,000 J85 engines between the 1950s and the time production ended in 1988. However, the USAF currently plans to fly J85-equipped aircraft through 2040 when the youngest J85s will be over 50 years old.
The engine on display was acquired as a spare for the museum’s A-37 Dragonfly. A civilian version of this engine, the GE CF700, has been fitted to the museum’s T-33 as a light-weight replacement for its original J-33 turbojet engine.