General Electric YJ93



The General Electric YJ93 turbojet engine was designed as the powerplant for both the North American XB-70 Valkyrie bomber and the North American XF-108 Rapier interceptor. The YJ93 was a single-shaft axial-flow turbojet with a variable-stator compressor and a fully variable convergent/divergent exhaust nozzle. The maximum sea-level thrust was 28,800 lbf.

Design and development
The YJ93 started life as the General Electric J79-X275, an enlarged version of the General Electric J79 turbojet with "275" meaning Mach 2.75, the engine's target operating speed. This design evolved into the X279 when Mach 3 cruise became a requirement, and ultimately became the YJ93.

The engine used a special high-temperature JP-6 fuel. The six YJ93 engines in the XB-70 Valkyrie were capable of producing a thrust to weight ratio of 5:1 allowing for a speed of 2000 mph (approximately Mach 3) at an altitude of 70000 ft. The first engine went on test in September 1958 and featured advanced technology achievements such as electrolytically drilling longitudinal air cooling holes in the turbine blades.

The XF-108 interceptor was cancelled outright, and the B-70 project was re-oriented to a research project only.

Variants

 * J93-GE-1: 24800 lbf thrust with afterburner.
 * J93-GE-3: Production variant produced in small numbers for the North American XB-70 Valkyrie program.
 * J93-GE-3R: Variant with thrust reverser, 27200 lbf thrust with afterburner.
 * J93-GE-3AR: Variant intended for the North American XF-108 Rapier.

Applications

 * Convair NB-58A Hustler (testbed)
 * North American XB-70 Valkyrie
 * North American XF-108 Rapier (intended)