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 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.