This engine lifted the ascent stage (upper section) of a Lunar Module off the surface of the Moon. The ascent stage then docked with the orbiting Command and Service Modules.
The ascent engine had to perform with high reliability; a serious malfunction could have stranded the astronauts on the Moon.
The ascent engine provides 1587 kilograms (3500 pounds) of thrust. The engine burns liquid propellants: the fuel is 50% hydrazine and 50% unsymmetrical dimethylhydrazine; the oxidizer is nitrogen tetroxide. These propellants are hypergolic; that is, they ignite spontaneously when brought together in the rocket's combustion chamber.