This is a cutaway of the RL-10 rocket engine, the world's first operational liquid-hydrogen/liquid oxygen high energy rocket engine that was re-startable in space. Two RL-10 engines, each producing 15,000 pounds of thrust, made up the Centaur upper stage used with the Atlas and Titan launch vehicles.
A cluster of six RL-10 engines also powered the second stage of the Saturn 1 vehicle, a precursor to the Saturn V that sent the first astronauts to the Moon under Project Apollo. The first successful operational flight of the Atlas-Centaur took place in 1966 and this was also the first time the RL-10 made a full-thrust re-start in space. The engine was donated to the Smithsonian in 1976 by the NASA Lewis Research Center.
Transferred from the National Aeronautics and Space Administration