This is the J-2 liquid propellant rocket engine that powered the second and third stages of the Project Apollo Saturn V launch vehicle which sent astronauts ito the Moon. The second stage was fitted with a cluster of five J-2s and a single J-2 powered the third stage. The J-2 used liquid oxygen and liquid hydrogen as propellants.
J-2 engines were successfully used on every Apollo mission from the first manned test flight, Apollo 7, in 1968 to the last Moon landing mission, Apollo 17, in 1972. The Saturn V also launched the Skylab 1 space station in 1973 and a J-2 powered the second stage of the Saturn 1B that launched the Apollo-Soyuz Test Project (ASTP) in 1975.
Gift of Rocketdyne Division, Rockwell International Corporation