| Country of origin | United States |
|---|---|
| Date | 1964–72 |
| Manufacturer | Bell Aircraft / Rocketdyne |
| Purpose | Lunar Ascent Stage/Spacecraft propulsion |
| Predecessor | Bell 8247 |
| Successor | RS-18 |
| Status | Retired |
| Oxidiser | N2O4 |
| Fuel | Aerozine 50 |
| Mixture ratio | 1.6 |
| Cycle | Pressure-fed |
| Pumps | None |
| Combustion chamber | 1 |
| Nozzle ratio | 46 |
| Thrust(vac) | 3,500 pounds-force (16 kN) |
| Thrust to weight | 16.7 (weight on Earth) |
| Chamber pressure | 120 pounds per square inch (8.3 bar) |
| Specific impulse vacuum | 311 isp |
| Burn time | 200 seconds |
| Restarts | Designed for 1 restarts |
| Length | 47 inches (120 cm) |
| Diameter | 31 inches (79 cm) |
| Dry weight | 209.1 pounds (94.8 kg) |
| Used in | Lunar module as ascent engine |
| References | [1] |
The ascent propulsion system (APS) or lunar module ascent engine (LMAE) 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 N2O4 oxidizer. Rocketdyne provided the injector system, at the request of NASA, when Bell could not solve combustion instability problems.[2]
Origins
The LMAE traces its origin to the earlier Bell Aerosystems engines (8096, 8247) used in the RM-81 Agena, the rocket upper stage and satellite support bus developed by Lockheed initially for the canceled WS-117L reconnaissance satellite program.[3] The Agena served as an upper stage for several defense, intelligence, and exploration programs: SAMOS-E, SAMOS-F (ELINT Ferret) and MIDAS (Missile Defense Alarm System) 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.[4]
A total of 365 Agena rockets were launched by NASA and the U.S. 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.[5][6]
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 (self-igniting) propellants, the ascent engine was fixed-thrust and nongimbaled, capable of lifting the ascent stage off the Moon or aborting a landing if necessary.[7]
The engine developed about 1,600 pounds-force (7.1 kN) of thrust, which produced a velocity of 3,200 meters per second from lunar launch, to LOR, and CM docking.[7][2]
RS-18 Engine
Rocketdyne brought the lunar module ascent engine out of its 36-year retirement in 2008 for NASA's Exploration Systems Architecture Study (ESAS) engine testing, re-designated it as RS-18, and reconfigured the non-throttleable hypergolic engine to use LOX/methane.[8]
References
- ^ Bartlett, W.; Kirkland, Z. D.; Polifka, R. W.; Smithson, J. C.; Spencer, G. L. (February 7, 1966). Apollo spacecraft liquid primary propulsion systems. Houston, TX: NASA, Manned Spacecraft Center. pp. 8–9. 70N35721. Archived August 23, 2022 at the Wayback Machine. Retrieved August 23, 2022.
- ^ "LM Ascent Propulsion". Encyclopedia Astronautica. Archived from the original on 17 November 2002. Retrieved June 7, 2012.
- ^ Neufeld, Jacob; Watson, Jr., George M.; Chenoweth, David (eds.) (1997). "Technology and the Air Force A Retrospective Assessment". Air Force History and Museums Program. Archived October 7, 2012 at the Wayback Machine.
- ^ Lockheed Missiles and Space Company (February 25, 1972). Shuttle/Agena Study. Vol. 1. NASA. CR-115491. Archived May 18, 2023 at the Wayback Machine.
- ^ Grassly, Sarah A. (June 1969). Agena Flight History as of 31 December 1967. Vol. 1. Air Force Systems Command. Archived from the original on September 16, 2012. Retrieved June 7, 2012.
- ^ Parsch, Andreas (February 27, 2003). "Lockheed RM-81 Agena". Directory of U.S. Military Rockets and Missiles. Archived June 5, 2023 at the Wayback Machine. Retrieved June 6, 2012.
- ^ Brooks, Courtney G.; Grimwood, James M.; Swenson, Loyd S. (September 20, 2007). "Engines, Large and Small". Chariots for Apollo: A History of Manned Lunar Spacecraft. LCCN 79001042. SP-4205. Archived from the original on October 5, 2015. Retrieved June 7, 2012.
- ^ "Heritage lunar engine fired up once again". Pratt & Whitney Rocketdyne. 2 September 2008. Archived 19 December 2008 at the Wayback Machine. Retrieved 12 September 2023. – via Spaceflight Now.