RL-10A-5

Pratt and Whitney LOx/LH2 rocket engine. Throttleable to 30% of thrust, sea level version of RL10. Four engines were built and were used on the DC-X and the upgraded DC-XA VTOVL SSTO launch vehicle demonstrators. First flight 1993.

The DC-Y was a conceptual vehicle design and did not use these engines. The RL-10A-5KA was proposed for use on the Kistler K-1 vehicle but was not selected.

Thrust (sl): 54.800 kN (12,320 lbf). Thrust (sl): 5,591 kgf. Engine: 143 kg (315 lb). Chamber Pressure: 39.12 bar. Area Ratio: 4. Thrust to Weight Ratio: 47. Oxidizer to Fuel Ratio: 6. Coefficient of Thrust vacuum: 1.5. Coefficient of Thrust sea level: 1.37.