The nominal 200,000 lb. sea-level thrust RS-27A powers the Delta II launch vehicle and has compiled one of the most consistent and successful launch records in the history of rocketry with a 100-percent reliability factor.
A single-start power plant is gimbal-mounted and operates on a combination of liquid oxygen and RP-1 (kerosene). The thrust chamber is regeneratively cooled with fuel circulating through tubes that comprise the thrust chamber.
The RS-27A is the latest version of this propulsion system that includes a higher 12:1 area expansion ratio thrust chamber nozzle among other improvements. The RS-27A is used as the main booster propulsion system for the Delta II family of launch vehicles.