RS-68
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 | 20 November 2002 |
| Last flight | 9 April 2024 |
| Designer | Rocketdyne |
| Manufacturer |
|
| Application | First stage engine |
| Associated LV | Delta IV · Delta IV Heavy |
| Status | Retired |
| Liquid-fuel engine | |
| Propellant | LOX / LH2 |
| Cycle | Gas-generator |
| Configuration | |
| Nozzle ratio | 21.5:1 |
| Performance | |
| Thrust, sea-level | RS-68: 2,950 kN (660,000 lbf) RS-68A: 3,137 kN (705,000 lbf) |
| Thrust-to-weight ratio | RS-68: 45.3:1 RS-68A: 47.4:1 |
| 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) |
| Dimensions | |
| Length | 5.20 m (17.1 ft) |
| Diameter | 2.43 m (8 ft 0 in) |
| Dry mass | RS-68: 6,600 kg (14,560 lb) RS-68A: 6,740 kg (14,870 lb) |
The 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 cycle. It was the largest hydrogen-fueled rocket engine ever flown.
Designed and manufactured in the United States by Rocketdyne (later Pratt & Whitney Rocketdyne and Aerojet Rocketdyne). 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 the cancellation of the rocket and the Constellation Program in 2010.