This is an APS (Auxiliary Propulsion System) attitude control rocket motor for the third stage (S-IV) of the Saturn V launch vehicle that took astronauts to the Moon in Project Apollo. The liquid propellant APS motors provided control in the three axes of roll, pitch and yaw control for the S-IV during Earth orbit and injection into lunar orbit. They produced 150 pounds of thrust, generated as pulses as required.
Each APS module contained three motors. This one was fired in tests. APS engines were used in all Apollo Saturn V missions from 1967 to 1972. They were also used in 1973 on the last Saturn V last boosted up Skylab into orbit, the U.S.'s first Earth-orbiting space station. This motor was donated to the Smithsonian in 1974 by McDonnelll Dougals Astronautics.
Gift of McDonnell Douglas Astronautics Company