RS 27

The RS-27 is a liquid-propellant rocket engine developed by Rocketdyne. It was used to power the first stage of the Delta 2000, 3000, 5000, and the first model of the Delta II, the Delta 6000.

The RS-27 was a modified Rocketdyne H-1 from surplus engines built to power the first stage of the Saturn I and Saturn IB and replaced the MB-3 engine that had been used on previous versions of the Delta launcher. In addition to its main engine, the RS-27 included two vernier engines to provide vehicle roll control during flight. RS-27 was later developed into the RS-27A, and RS-56.