Ascent propulsion system


The ascent propulsion system or lunar module ascent engine is a fixed-thrust hypergolic rocket engine developed by Bell Aerosystems for use in the Apollo lunar module ascent stage. It used Aerozine 50 fuel, and dinitrogen tetroxide| oxidizer. Rocketdyne provided the injector system, at the request of NASA, when Bell could not solve combustion instability problems.

Origins

The LMAE traces its origin to the earlier Bell Aerosystems engines used in the RM-81 Agena, the American rocket upper stage and satellite support bus developed by Lockheed initially for the canceled WS-117L reconnaissance satellite program.
The Agena served as an upper stage for several defense, intelligence, and exploration programs: SAMOS-E, SAMOS-F and MIDAS military early-warning satellites, Corona photo intelligence program, and the Ranger and Lunar Orbiter lunar probes.
The Lockheed Agena target vehicle using the Bell 8247 engine was qualified for 15 restarts for NASA's Project Gemini.
A total of 365 Agena rockets were launched by NASA and the US Air Force between February 28, 1959 and the last Agena D launched on 12 February 1987, configured as the upper stage of a Titan 34B.

Development

During the spring of 1963, Grumman hired Bell to develop the lunar module ascent engine, on the assumption that Bell's experience in development of the Air Force Agena engine would be transferable to the lunar module requirements. Grumman placed heavy emphasis upon high reliability through simplicity of design, and the ascent engine emerged as the least complicated of the three main engines in the Apollo space vehicle, including the LM descent and CSM service propulsion system engines.
Embodying a pressure-fed fuel system using hypergolic propellants, the ascent engine was fixed-thrust and nongimbaled, capable of lifting the ascent stage off the Moon or aborting a landing if necessary.
The engine developed about of thrust, which produced a velocity of 2,000 meters per second from lunar launch, to LOR, and CM docking. It weighed 180 pounds, with a length of 47 inches and diameter of 34 inches.

RS-18 Engine

Rocketdyne brought the lunar module ascent engine out of its 36-year retirement, now designated as RS-18, and reconfigured this non-throttleable hypergolic engine to use LOX/methane for NASA Exploration Systems Architecture Study engine testing in 2008.