RS-56
RS-56 was an American liquid fueled rocket engine, developed by Rocketdyne. RS-56 was derived from the RS-27 rocket engine. 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.
