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 (128 kN).^[1]

YJ93
YJ93-GE-3 engine at National Museum of the United States Air Force
Type	Turbojet engine
National origin	United States
Manufacturer	General Electric Aircraft Engines
Major applications	North American XB-70 Valkyrie
Developed into	General Electric GE4

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.^[2] This design evolved into the X279 when Mach 3 cruise became a requirement, and ultimately became the YJ93.^[3]

YB-58 at Edwards AFB with GE J93 engine pod

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 2,000 mph (3,200 km/h) (approximately Mach 3) at an altitude of 70,000 feet (21,000 m).^[4] 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.^[2]

The XF-108 interceptor was cancelled outright, and the B-70 project was re-oriented to a research project only.^[5]

Variants

J93-GE-1

24,800 lbf (110 kN) thrust with afterburner.^[6]

J93-GE-3

Production variant produced in small numbers for the North American XB-70 Valkyrie program.

J93-GE-3R

Variant with thrust reverser, 27,200 lbf (121 kN) thrust with afterburner.^[7]

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)

Specifications (J93-GE-3)

Data from Aircraft engines of the World 1966/77,^[8] Military Turbojet/Turbofan Specifications,^[9] North American XB-70A Valkyrie^[1]

General characteristics

• Type: Turbojet with afterburner
• Length: 237 in (6,000 mm)
• Diameter: 52.5 in (1,330 mm)
• Dry weight: 5,000 lb (2,300 kg)

Components

• Compressor: 11-stage axial
• Combustors: Annular with 36 dual fuel nozzles
• Turbine: Two-stage axial
• Fuel type: Special high-temperature JP-6 Fuel to MIL-F-25656
• Oil system: Return oil spray system at 60 psi (410 kPa)

Performance

• Maximum thrust: 22,000 lbf (98 kN) dry; 30,000 lbf (130 kN) with afterburner
• Air mass flow: 275 lb/s (125 kg/s)
• Turbine inlet temperature: 1,149 °C (2,100 °F; 1,422 K)
• Specific fuel consumption: 0.700 lb/(lbf⋅h) (19.8 g/(kN⋅s)) dry; 1.800 lb/(lbf⋅h) (51.0 g/(kN⋅s)) wet
• Thrust-to-weight ratio: 6

See also

Related development

• General Electric J79
• General Electric GE4

Comparable engines

• de Havilland Gyron
• Lyulka AL-7
• Kolesov RD-36-51
• Kuznetsov NK-32
• Kuznetsov NK-144
• Orenda Iroquois
• Pratt & Whitney J58
• Rolls-Royce RB.106
• Tumansky R-15

Related lists

• List of aircraft engines