RS-27A
The RS-27A is a liquid-fuel rocket engine developed in 1980s by Rocketdyne for use on the first stage of the Delta II and Delta III launch vehicles. It provides of thrust burning RP-1 and LOX in a gas-generator cycle. The engine is a modified version of its predecessor, the RS-27; its thrust nozzle has been extended to increase its area ratio from 8:1 to 12:1, which provides greater efficiency at altitude. The earlier RS-27 was derived from surplus Rocketdyne H-1 engines used in the Saturn 1B launcher.
The RS-27A main engine is neither restartable nor throttleable. In addition to its main engine, it includes two vernier engines to provide vehicle roll control during flight.. When used as the main booster propulsion system for the Delta II family of launch vehicles, has an operational duration of 265 seconds.
The last RS-27A engine was used for the ICESat-2 launch on 15 September, 2018.
