Ascent propulsion system
{{Short description|Apollo Lunar Module rocket engine}}
{{Use mdy dates|date=September 2023}}
{{Infobox rocket engine
|name = Ascent propulsion system (APS)
|image = Apollo Lunar Module Ascent Engine.jpg
|image_size =
|caption = Apollo LM ascent engine
|country_of_origin = United States
|date = 1964–72
|designer =
|manufacturer = Bell Aircraft / Rocketdyne
|purpose = Lunar Ascent Stage/Spacecraft propulsion
|associated =
|predecessor = Bell 8247
|successor = RS-18
|status = Retired
|type = liquid
|oxidiser = dinitrogen tetroxide
|fuel = Aerozine 50
|mixture_ratio = 1.6
|cycle = Pressure-fed
|pumps = None
|description =
|combustion_chamber = 1
|nozzle_ratio = 46
|thrust =
|thrust_at_altitude=
|thrust(Vac) = {{convert|3500|lbf|kN}}
|thrust(SL) =
|throttle_range =
|thrust_to_weight = 16.7 (weight on Earth)
|chamber_pressure= {{convert|120|psi|bar}}
|specific_impulse=
|specific_impulse_vacuum = {{convert|311|isp}}
|specific_impulse_sea_level=
|total_impulse =
|mass_flow =
|burn_time = 200 seconds
|restarts = Designed for 1 restarts
|gimbal =
|capacity =
|dimensions =
|length = {{convert|510|in|cm}}
|diameter = {{convert|100|in|cm}}
|dry_weight = {{convert|2100|lb|kg}}
|used_in = Lunar module as ascent engine
|references = {{cite tech report |last1=Bartlett |first1=W. |last2=Kirkland |first2=Z. D. |last3=Polifka |first3=R. W. |last4=Smithson |first4=J. C. |last5=Spencer |first5=G. L. |date=February 7, 1966 |title=Apollo spacecraft liquid primary propulsion systems |url=https://ntrs.nasa.gov/api/citations/19700026405/downloads/19700026405.pdf |location=Houston, TX |publisher=NASA, Manned Spacecraft Center |pages=8–9 |archive-url=https://web.archive.org/web/20220823092501/https://ntrs.nasa.gov/api/citations/19700026405/downloads/19700026405.pdf |archive-date=August 23, 2022 |access-date=August 23, 2022 |url-status=live |id=70N35721}}
|notes =
}}
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 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 (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.{{cite web |editor-last1=Neufeld |editor-first1=Jacob |editor-last2=Watson, Jr. |editor-first2=George M. |editor-last3=Chenoweth |editor-first3=David |date=1997 |title=Technology and the Air Force A Retrospective Assessment |url=https://apps.dtic.mil/sti/pdfs/ADA440094.pdf |publisher=Air Force History and Museums Program |archive-url=https://web.archive.org/web/20121007221217/http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA440094&Location=U2&doc=GetTRDoc.pdf |archive-date=October 7, 2012 |url-status=live }}
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.{{cite tech report |author=Lockheed Missiles and Space Company |date=February 25, 1972 |title=Shuttle/Agena Study |volume=1 |url=https://ntrs.nasa.gov/api/citations/19720013175/downloads/19720013175.pdf |publisher=NASA |archive-url=https://web.archive.org/web/20230518210732/https://ntrs.nasa.gov/api/citations/19720013175/downloads/19720013175.pdf |archive-date=May 18, 2023 |url-status=live |id=CR-115491 }}
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.{{cite tech report |last=Grassly |first=Sarah A. |date=June 1969 |title=Agena Flight History as of 31 December 1967 |volume=1 |url=http://www.nro.gov/foia/declass/WS117L_Records/276.PDF |publisher=Air Force Systems Command |access-date=June 7, 2012 |archive-url=https://web.archive.org/web/20120916000501/http://www.nro.gov/foia/declass/WS117L_Records/276.PDF |archive-date=September 16, 2012 |url-status=dead }}{{cite web |last=Parsch |first=Andreas |date=February 27, 2003 |title=Lockheed RM-81 Agena |url=https://www.designation-systems.net/dusrm/app1/rm-81.html |website=Directory of U.S. Military Rockets and Missiles |access-date=June 6, 2012 |archive-url=https://web.archive.org/web/20230605203820/https://www.designation-systems.net/dusrm/app1/rm-81.html |archive-date=June 5, 2023 |url-status=live }}
File:Apollo 17 LM Ascent Stage.jpg LM Ascent Stage]]
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.{{cite book |last1=Brooks |first1=Courtney G. |last2=Grimwood |first2=James M. |last3=Swenson |first3=Loyd S. |date=September 20, 2007 |title=Chariots for Apollo: A History of Manned Lunar Spacecraft |chapter=Engines, Large and Small |url=http://www.hq.nasa.gov/office/pao/History/SP-4205/ch6-5.html |archive-url=https://web.archive.org/web/20151005065217/http://www.hq.nasa.gov/office/pao/History/SP-4205/ch6-5.html |archive-date=October 5, 2015 |access-date=June 7, 2012 |url-status=dead |id=SP-4205 |lccn=79001042}}
The engine developed about {{convert|1600|lbf|kN}} of thrust, which produced a velocity of 3,200 meters per second from lunar launch, to LOR, and CM docking.{{cite web |url=http://www.astronautix.com/craft/lmalsion.htm |publisher=Encyclopedia Astronautica |title=LM Ascent Propulsion |accessdate=June 7, 2012 |archive-url=https://web.archive.org/web/20021117170847/http://www.astronautix.com/craft/lmalsion.htm |archive-date=17 November 2002| url-status=dead}}
RS-18 Engine
{{ Main | RS-18 }}
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.{{cite press release |title=Heritage lunar engine fired up once again |url=https://spaceflightnow.com/news/n0809/02rs18/ |via=Spaceflight Now |publisher=Pratt & Whitney Rocketdyne |access-date=12 September 2023 |archive-url=https://web.archive.org/web/20081219104855/http://spaceflightnow.com/news/n0809/02rs18/ |archive-date=19 December 2008 |date=2 September 2008 |url-status=live}}
References
{{reflist}}
{{Include-NASA}}
External links
{{Apollo program hardware}}
{{Orbital spacecraft rocket engines}}
Category:Rocket engines using hypergolic propellant
Category:Apollo program hardware