The General Electric YJ93turbojet 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 (128 kN).
The YJ93 started life as the General Electric X275, an enlarged version of the General Electric J79 turbojet. This evolved to 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, allowing for a speed of 2,000 mph (3,200 km/h) (approximately Mach 3) at an altitude of 70,000 feet (21,000 m).
The XF-108 interceptor was cancelled outright and the B-70 project was reoriented to a research project only.