ASME-Landmark:R L-10 Rocket Engine

The Pratt & Whitney Aircraft RL-10, which served as the power plant for NASA's upper-stage Centaur space launch vehicle, was the first rocket engine to use high-energy liquid hydrogen as a fuel. It was the technological pathfinder in hydrogen rocketry and led to the development of larger engines that made the 1969 lunar landing possible.

The RL-10 provided precisely controlled, reliable power for lunar and planetary explorations. It embodied numerous advanced design features, including multiple use of its fuel with the "bootstrap cycle." The RL-10 was also capable of multiple restarts in space, which enabled positioning of satellites or further escape of Earth's gravity.

Design of the RL-10 began in the fall of 1958 at the Pratt & Whitney Aircraft Florida Research and Development Center. In the first flight demonstration on November 27, 1963, a pair of RL-10s successfully boosted a Centaur space vehicle into orbit around the earth. Two months later, on January 29, 1964, a six-engine cluster of RL-10s generated 90,000 pounds of thrust to lift the first test flight of the Saturn S-IV stage, pioneering hydrogen technology on the Saturn I booster.

The RL-10 was transferred to the Smithsonian National Air and Space Museum in 1974. Its current design as of 2016 include the RL-10B-2, in use in the Delta III and Delta IV second stage, and the RL-10A-4-2, used on Centaur upper stage for Atlas V. See ASME website for more information