Who is originally behind the development of XXX?
RL10
Built in the United States by Aerojet Rocketdyne (formerly by Pratt & Whitney Rocketdyne), the RL10 burns cryogenic liquid hydrogen and liquid oxygen propellants, with each engine producing 64.7 to 110 kN (14,545--24,729 lbf) of thrust in vacuum depending on the version in use.