Back RS-68 Catalan RS-68 Czech RS-68 German RS-68 (motor de cohete) Spanish RS-68 (rakettimoottori) Finnish RS-68 French RS-68 Galician RS-68 HE RS-68 ID RS-68 Italian
 An RS-68 engine undergoing hot-fire testing at NASA's Stennis Space Center during its developmental phase. | |
| Country of origin | United States |
|---|---|
| First flight | 2002 |
| Manufacturer | Rocketdyne Pratt & Whitney Rocketdyne Aerojet Rocketdyne |
| Application | First stage engine for the Delta IV rocket |
| Status | Retired |
| Liquid-fuel engine | |
| Propellant | Liquid oxygen / Liquid hydrogen |
| Cycle | Gas-generator cycle |
| Configuration | |
| Nozzle ratio | 21.5 |
| Performance | |
| Thrust, sea-level | RS-68: 660,000 lbf (2,950 kN) RS-68A: 705,000 lbf (3,137 kN)[1] |
| Thrust-to-weight ratio | RS-68: 45.3 RS-68A: 47.4 |
| Chamber pressure | 1,488 psi (10.26 MPa) |
| Specific impulse, vacuum | RS-68: 410 s (4.0 km/s) RS-68A: 411.9 s (4.039 km/s)[2] |
| Dimensions | |
| Length | 17.1 ft (5.20 m) |
| Diameter | 8 ft 0 in (2.43 m) |
| Dry weight | RS-68: 14,560 lb (6,600 kg) RS-68A: 14,870 lb (6,740 kg)[1] |
| Used in | |
| Delta IV | |
The Aerojet Rocketdyne RS-68 (Rocket System 68) was a liquid-fuel rocket engine that used liquid hydrogen (LH2) and liquid oxygen (LOX) as propellants in a gas-generator power cycle. It was the largest hydrogen-fueled rocket engine ever flown.[3]
Its development started in the 1990s with the goal of producing a simpler, less-costly, heavy-lift engine for the Delta IV launch system. Two versions of the engine have been produced: the original RS-68 and the improved RS-68A. A third version, the RS-68B, was planned for the National Aeronautics and Space Administration's (NASA) Ares V rocket before cancellation of the rocket and the Constellation Program in 2010.
- ^ a b "DELTA IV". United Launch Alliance. Archived from the original on July 20, 2014. Retrieved July 13, 2014.
- ^ "Delta IV User's Guide" (PDF). United Launch Alliance. June 2013. Archived (PDF) from the original on July 10, 2014. Retrieved July 13, 2014.
- ^ "ATK Propulsion and Composite Technologies Help Launch National Reconnaissance Office Satellite" (Press release). Alliant Techsystems. January 19, 2009. Archived from the original on February 22, 2014.