This is the Lunar Module Ascent Engine, one of the most important in the manned Project Apollo missions. It was used to lift up the ascent stage of the Lunar Excursion Module (LM) from the surface of the Moon. The LM then docked with the Command Module (CM) orbiting the Moon. Developed by Bell Aerosystems, the engine generated 3,500 pounds of thrust.
The engine shown here was used in tests at White Sands Test Facility, New Mexico, in 1964, and was later installed on a Lunar Module test article for thermal tests at Grumman Aerospace, Bethpage, New York, the prime contractor for the LM. This engine was donated to the Smithsonian in 1972 by the Grumman Aerospace Co.
Grumman Aerospace Corp.