| RS-56 | |
| First Date: | 1991 |
| Country Of Origin: | United States |
| Manufacturer: | Rocketdyne |
| Type: | liquid |
| Status: | Retired |
| Predecessor: | RS-27A |
| Fuel: | RP-1 |
| Oxidiser: | LOX |
| Cycle: | Gas-generator |
| Thrust(Sl): | RS-56-OBA: 920.8abbr=onNaNabbr=on RS-56-OSA: 269abbr=onNaNabbr=on |
| Specific Impulse Vacuum: | RS-56-OBA: 299isp RS-56-OSA: 316isp |
| Specific Impulse Sea Level: | RS-56-OBA: 263isp RS-56-OSA: 220isp |
| Chamber Pressure: | 48order=flipNaNorder=flip |
| Burn Time: | RS-56-OBA: 172 RS-56-OSA: 283 sec |
| Length: | RS-56-OBA: 3.43abbr=onNaNabbr=on 2.7abbr=onNaNabbr=on |
| Diameter: | RS-56-OBA: 2.45abbr=onNaNabbr=on 3.05abbr=onNaNabbr=on |
| Used In: | Atlas II |
RS-56 (Rocket System-56) was an American liquid-fueled rocket engine, developed by Rocketdyne. RS-56 was derived from the RS-27 rocket engine,[1] which itself is derived from the Rocketdyne H-1 rocket engine used in the Saturn I and Saturn IB. Two variants of this engine were built, both for use on the Atlas II rocket series. The first, RS-56-OBA, was a booster engine, while the RS-56-OSA was designed for use as a sustainer and produced lower thrust but at a higher specific impulse.[2] [3]