RS-25

The RS-25, also known as the Space Shuttle Main Engine, is a liquid fuel cryogenic rocket engine burning liquid hydrogen and liquid oxygen, designed by Rocketdyne and now built by Aerojet Rocketdyne. It first flew aboard Space Shuttle Columbia on April 12, 1981, three engines mounted in each orbiter's aft structure generating about 1,859 kilonewtons of thrust apiece at liftoff, and the engine continues in service on NASA's Space Launch System, the first four SLS flights reusing refurbished shuttle-era engines and later flights using a new expendable variant, RS-25E.