ABOUT RS-68A
The RS-68A is a simplified, high-thrust hydrogen/oxygen gas generator engine built by Aerojet Rocketdyne for the Delta IV family. It was designed for low cost and manufacturability rather than maximum performance, using an ablatively-cooled nozzle. The RS-68A is an upgraded version of the RS-68 with increased thrust and efficiency.
Image: ULA
PERFORMANCE
| Thrust (Sea Level) | 3,137 kN (705,300 lbf) kN |
| Thrust (Vacuum) | 3,560 kN (800,000 lbf) kN |
| ISP (Sea Level) | 362 s s |
| ISP (Vacuum) | 412 s s |
| Chamber Pressure | 10.26 MPa (1,488 psi) bar |
| Mass | 6 kg |
| Thrust-to-Weight | 54 |
| Throttle Range | 57–102% |
| Restart Capable | No |
THRUST CONVERSIONS (VACUUM)
| Kilonewtons | 3.0 kN |
| Pounds-force | 674 lbf |
ENGINE CYCLE
Gas Generator
A gas generator cycle taps off a small portion of propellants to drive turbopumps via a separate combustion chamber. The turbine exhaust is dumped overboard, making it less efficient but simpler and more reliable. Used by the Merlin, F-1, and RS-27.
PROPULSION
| Propellant | Liquid Hydrogen (LH₂) |
| Oxidizer | LOX |
| Engine Cycle | Gas Generator |
| Mixture Ratio | 6:1 |
| Flow Rate | ~880 kg/s kg/s |
PHYSICAL
| Dimensions | 2.44 m diameter × 5.2 m length |
| Combustion Chambers | 1 |
| Nozzle Expansion Ratio | 21.5:1:1 |
GENERAL
| Manufacturer | Aerojet Rocketdyne |
| Country | United States |
| Status | Retired (with Delta IV) |
| First Flight | January 1, 1970 |
VARIANTS (2)
- RS-68
- RS-68A
VEHICLES USING RS-68A (2)
- Delta IV
- Delta IV Heavy
ENGINE LINEAGE
RS-68→RS-68A
⚖ PROPELLANTS
