Editing Apollo Lunar Module (section)

==History==
[[File:Joseph Francis Shea.jpg|thumb|left|upright|A 1962 model of the first LEM design, docked to the command and service module. The model is held by [[Joseph Francis Shea|Joseph Shea]], the key engineer behind the adoption of [[lunar orbit rendezvous]] mission logistics.]]
The Lunar Module (originally designated the Lunar Excursion Module, known by the [[Acronym and initialism|acronym]] LEM) was designed after NASA [[Project Apollo#Choosing a mission mode|chose to reach the Moon]] via [[Lunar Orbit Rendezvous]] (LOR) instead of the [[direct ascent]] or [[Earth Orbit Rendezvous]] (EOR) methods. Both direct ascent and EOR would have involved landing a much heavier, complete Apollo spacecraft on the Moon. Once the decision had been made to proceed using LOR, it became necessary to produce a separate craft capable of reaching the lunar surface and ascending back to lunar orbit.

===Contract letting and construction location===
In July 1962, eleven firms were invited to submit proposals for the LEM. Nine companies responded in September, answering 20 questions posed by the NASA RFP in a 60-page limited technical proposal. [[Grumman]] was awarded the contract officially on November 7, 1962.<ref>{{Cite web|first=Amy Shira|last=Teitel|date=May 31, 2019|title=Lunar Module: How do you land on the Moon?|url=https://astronomy.com/news/2019/05/lunar-module-how-do-you-land-on-the-moon|access-date=September 29, 2021|website=Astronomy.com|language=en}}</ref> Grumman had begun lunar orbit rendezvous studies in the late 1950s and again in 1961. The contract cost was expected to be around $350&nbsp;million.<ref>{{Cite news|date=November 16, 1962|title=Aerospace: Grumman in Orbit|language=en-US|magazine=Time|url=https://content.time.com/time/subscriber/article/0,33009,829433,00.html|access-date=September 29, 2021|issn=0040-781X}}</ref> There were initially four major subcontractors: [[Bell Aerosystems]] ([[Ascent Propulsion System|ascent engine]]), [[Hamilton Standard]] ([[Environmental control system|environmental control systems]]), [[Marquardt Corporation|Marquardt]] ([[reaction control system]]) and [[Rocketdyne]] ([[Descent Propulsion System|descent engine]]).<ref>{{cite web |url=http://www.hq.nasa.gov/office/pao/History/SP-4205/ch6-5.html |title=Chariots for Apollo: A History of Manned Lunar Spacecraft; Engines, Large and Small |author1=Courtney G. Brooks |author2=James M. Grimwood |author3=Loyd S. Swenson |date=September 20, 2007 |access-date=June 7, 2012 |archive-date=March 1, 2012 |archive-url=https://web.archive.org/web/20120301152142/http://www.hq.nasa.gov/office/pao/History/SP-4205/ch6-5.html |url-status=live }}</ref>

The [[Apollo PGNCS|Primary Guidance, Navigation and Control System]] (PGNCS) was developed by the [[Charles Stark Draper Laboratory|MIT Instrumentation Laboratory]]; the [[Apollo Guidance Computer]] was manufactured by [[Raytheon]] (a similar guidance system was used in the [[Apollo command and service module|command module]]). A backup navigation tool, the [[Apollo Abort Guidance System|Abort Guidance System]] (AGS), was developed by [[TRW Inc.|TRW]]. The landing gear was manufactured by [[Héroux-Devtek|Héroux]].<ref>{{cite web | url=https://spaceq.ca/the-canadian-story-of-the-apollo-lunar-module-landing-legs/ | title=The Canadian Story of the Apollo Lunar Module Landing Legs | date=July 15, 2019 }}</Ref> 

The Apollo Lunar Module was assembled in a Grumman factory in [[Bethpage, New York]].<ref name="NASA Jan182018">{{cite web |last=Garcia|first=Mark|title=50 Years Ago: The Apollo Lunar Module | website=NASA | date=18 January 2018 | url=http://www.nasa.gov/feature/50-years-ago-the-apollo-lunar-module | access-date=26 December 2022}}</ref><ref name="Newsday Jul192019">{{cite web | last=Jones | first=Bart | title=Bethpage park honors workers who built Apollo 11 lunar module | website=Newsday | date=19 July 2019 | url=https://www.newsday.com/long-island/nassau/apollo-grumman-bethpage-park-dedication-a09303 | access-date=26 December 2022}}</ref>

===Design phase===
[[File:Lunar Lander Model.jpg|thumb|This 1963 model depicts the second LEM design, which gave rise to informal references as "the bug".]]
The Apollo Lunar Module was chiefly designed by Grumman aerospace engineer [[Thomas J. Kelly (aerospace engineer)|Thomas J. Kelly]].<ref>{{cite news|url=https://www.nytimes.com/2002/03/27/nyregion/t-j-kelly-72-dies-father-of-lunar-module.html|title=T. J. Kelly, 72, Dies; Father of Lunar Module|first=Warren E.|last=Leary|newspaper=The New York Times|date=March 27, 2002|access-date=February 18, 2017|archive-date=June 23, 2017|archive-url=https://web.archive.org/web/20170623183449/http://www.nytimes.com/2002/03/27/nyregion/t-j-kelly-72-dies-father-of-lunar-module.html|url-status=live}}</ref> The first LEM design looked like a smaller version of the Apollo command and service module (a cone-shaped cabin atop a cylindrical propulsion section) with folding legs. The second design invoked the idea of a helicopter cockpit with large curved windows and seats to improve the astronauts' visibility for hover and landing. This also included a second, forward docking port, allowing the LEM crew to take an active role in docking with the CSM.

As the program continued, there were numerous redesigns to save weight, improve safety, and fix problems. First to go were the heavy cockpit windows and the seats; the astronauts would stand while flying the LEM, supported by a cable and pulley system, with smaller triangular windows giving them sufficient visibility of the landing site. Later, the redundant forward docking port was removed, which meant the Command Pilot gave up active control of the docking to the Command Module Pilot; he could still see the approaching CSM through a small overhead window. Egress while wearing bulky extra-vehicular activity spacesuits was eased by a simpler forward hatch ({{cvt|32|x|32|in|disp=or}}).

The configuration was frozen in April 1963, when the ascent and descent engine designs were decided. In addition to Rocketdyne, a parallel program for the descent engine<ref name="NASA"/> was ordered from [[TRW Inc.#Space exploration|Space Technology Laboratories (TRW)]] in July 1963, and by January 1965 the Rocketdyne contract was cancelled.

Power was initially to be produced by [[fuel cell]]s built by [[Pratt and Whitney]] similar to the CSM, but in March 1965 these were discarded in favor of an all-battery design.<ref>{{cite web|url=http://www.astronautix.com/craft/lmerical.htm|title=LM Electrical|publisher=[[Encyclopedia Astronautica]]|url-status=dead|archive-url=https://web.archive.org/web/20100201084039/http://astronautix.com/craft/lmerical.htm|archive-date=February 1, 2010}}</ref>

The initial design had three landing legs, the lightest possible configuration. But as any particular leg would have to carry the weight of the vehicle if it landed at a significant angle, this was also the least stable configuration if one of the legs were damaged during landing. The next landing gear design iteration had five legs and was the most stable configuration for landing on an unknown terrain. That configuration, however, was too heavy and the designers compromised on four landing legs.<ref>{{cite web|url=http://www.astronautix.com/craft/lmlggear.htm|title=LM Landing Gear|publisher=Encyclopedia Astronautica|url-status=dead|archive-url=https://web.archive.org/web/20100201083530/http://astronautix.com/craft/lmlggear.htm|archive-date=February 1, 2010}}</ref>

In June 1966, the name was changed to Lunar Module (LM), eliminating the word ''excursion''.<ref>{{cite web |title=SP-4402 Origins of NASA Names |url=https://history.nasa.gov/SP-4402/ch4.htm |website=NASA History |publisher=NASA |access-date=January 16, 2015 |archive-date=December 4, 2016 |archive-url=https://web.archive.org/web/20161204214326/http://history.nasa.gov/SP-4402/ch4.htm |url-status=live }}</ref><ref>Scheer, Julian W. (Assistant Administrator for Public Affairs, NASA). Memorandum from Project Designation Committee, June 9, 1966.</ref> According to [[George Low]], Manager of the Apollo Spacecraft Program Office, this was because NASA was afraid that the word ''excursion'' might lend a frivolous note to Apollo.<ref>{{cite book |last=Cortright |first=Edgar M. |title=Apollo expeditions to the moon |url=https://archive.org/details/apolloexpedition00cort |url-access=registration |year=1975 |publisher=Scientific and Technical Information Office, National Aeronautics and Space Administration }} [https://history.nasa.gov/SP-350/ch-4-2.html NASA.gov ch-4-2] {{Webarchive|url=https://web.archive.org/web/20210428015444/https://history.nasa.gov/SP-350/ch-4-2.html |date=April 28, 2021 }}.</ref> Despite the name change, the astronauts and other NASA and Grumman personnel continued to pronounce the abbreviation as ({{IPAc-en|l|ɛ|m}}) instead of the letters "L-M".

===Astronaut training===
[[File:Lunar Landing Research Vehicle in Flight - GPN-2000-000215.jpg|thumb|upright|[[Lunar Landing Research Vehicle]] (LLRV) during a test flight]]

Comparing landing on the Moon to "a hovering operation", [[Gus Grissom]] said in 1963 that although most early astronauts were fighter pilots, "now we're wondering if the pilot making this first moon landing shouldn't be a highly experienced helicopter pilot".<ref name="grissom196302">{{Cite interview |last=Grissom |first=Gus |interviewer=John P. Richmond Jr. |title=The MATS Flyer Interviews Major Gus Grissom |url=https://books.google.com/books?id=wZ7RZyYIsmIC&pg=PA4 |access-date=June 28, 2020 |work=The MATS Flyer |publisher=Military Air Transport Service, United States Air Force |date=February 1963 |pages=4-7 |archive-date=July 26, 2020 |archive-url=https://web.archive.org/web/20200726073159/https://books.google.com/books?id=wZ7RZyYIsmIC&lpg=PA7&ots=JIkBJkm3cs&&pg=PA4#v=onepage&f=true |url-status=live }}</ref> To allow astronauts to learn lunar landing techniques, NASA contracted [[Bell Aerosystems]] in 1964 to build the [[Lunar Landing Research Vehicle]] (LLRV), which used a [[gimbal]]-mounted vertical jet engine to counter five-sixths of its weight to simulate the Moon's gravity, in addition to its own hydrogen peroxide thrusters to simulate the LM's descent engine and attitude control. Successful testing of two LLRV prototypes at the [[Dryden Flight Research Center]] led in 1966 to three production Lunar Landing Training Vehicles (LLTV) which along with the LLRV's were used to train the astronauts at the Houston Manned Spacecraft Center. This aircraft proved fairly dangerous to fly, as three of the five were destroyed in crashes. It was equipped with a rocket-powered ejection seat, so in each case the pilot survived, including the first man to walk on the Moon, [[Neil Armstrong]].<ref name="ugly">{{cite web|url=https://history.nasa.gov/alsj/alsj-LLRV.html|title=LLRV Monograph|access-date=July 12, 2017|archive-date=December 25, 2017|archive-url=https://web.archive.org/web/20171225232405/https://history.nasa.gov/alsj/alsj-LLRV.html|url-status=live}}</ref>

===Development flights===
[[File:67-H-1230 Lunar module LTA-2 R.jpg|thumb|The [[Apollo 6]] Lunar Module Test Article (LTA-2R) shortly before being mated with the SLA|250x250px]]

LM-1 was built to make the first uncrewed flight for propulsion systems testing, launched into low Earth orbit atop a [[Saturn IB]]. This was originally planned for April 1967, to be followed by the first crewed flight later that year. But the LM's development problems had been underestimated, and LM-1's flight was delayed until January 22, 1968, as [[Apollo 5]]. At that time, LM-2 was held in reserve in case the LM-1 flight failed, which did not happen.

LM-3 now became the first crewed LM, again to be flown in low Earth orbit to test all the systems and practice the separation, rendezvous, and docking planned for [[Apollo 8]] in December 1968. But again, last-minute problems delayed its flight until [[Apollo 9]] on March 3, 1969. A second, higher Earth orbit crewed practice flight had been planned to follow LM-3, but this was cancelled to keep the program timeline on track. [[Apollo 10]] launched on May 18, 1969, using LM-4 for a "dress rehearsal" for the lunar landing, practicing all phases of the mission except powered descent initiation through takeoff. The LM descended to {{convert|47400|ft|mi km|1}} above the lunar surface, then jettisoned the descent stage and used its ascent engine to return to the CSM.<ref name="chariots11-2">{{cite book|url=http://www.hq.nasa.gov/office/pao/History/SP-4205/contents.html|title=Chariots for Apollo: A History of Manned Lunar Spacecraft|author1=Courtney G. Brooks |author2=James M. Grimwood |author3=Loyd S. Swenson |year=1979|access-date=January 29, 2008|publisher=NASA|chapter=Chapter 12 Part 7|chapter-url = http://www.hq.nasa.gov/office/pao/History/SP-4205/ch12-7.html|isbn=0-486-46756-2| archive-url= https://web.archive.org/web/20080209003722/http://www.hq.nasa.gov/office/pao/History/SP-4205/contents.html| archive-date= February 9, 2008 | url-status= live}}</ref>

===Production flights===
[[File:Apollo 11 Lunar Module Eagle in landing configuration in lunar orbit from the Command and Service Module Columbia.jpg|thumb|The Apollo 11 [[Lunar Module Eagle|Lunar Module ''Eagle'']] in lunar orbit]]
The first crewed lunar landing occurred on July 20, 1969, in the [[Apollo 11]] [[Lunar Module Eagle|LM-5 ''Eagle'']]. Four days later, the Apollo 11 crew in the [[command module Columbia|command module ''Columbia'']] splashed down in the Pacific Ocean, completing [[Apollo program#Background|President John F. Kennedy's goal]]: "...before this decade is out, of landing a man on the Moon and returning him safely to the Earth".

This was followed by landings by [[Apollo 12]] (LM-6 ''Intrepid'') and [[Apollo 14]] (LM-8 ''Antares''). In April 1970, the [[Apollo 13]] LM-7 ''Aquarius'' saved the lives of the three astronauts after an oxygen tank in the [[Apollo command and service module#Service module|service module]] ruptured, disabling the CSM. ''Aquarius'' served as a "lifeboat" for the astronauts during their return to Earth. Its [[Descent propulsion system|descent stage engine]]<ref name="NASA">{{Cite book|title=Remembering the Giants - Apollo Rocket Propulsion Development - NASA|publisher=NASA|pages=73–86}}</ref> was used to replace the crippled CSM Service Propulsion System engine,<ref>{{Cite web |title=Apollo 13 Mission Report September 1970 MSC-02680 |url=https://www.nasa.gov/wp-content/uploads/static/history/alsj/a13/a13_missionreport.pdf |pages=12–14}}</ref> and its batteries supplied power for the trip home and recharged the Command Module's batteries critical for reentry. The astronauts splashed down safely in the [[Pacific Ocean|South Pacific Ocean]] on April 17, 1970. The LM's systems, designed to support two astronauts for 45 hours (including two depressurization and repressurization cycles, causing loss of oxygen supply), actually stretched to support three astronauts for 90 hours (without pressurization cycles and loss of oxygen).<ref>{{Cite web |title=Apollo 13 Lunar Module/ALSEP NSSDCA/COSPAR ID: 1970-029C |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1970-029C |archive-url=https://web.archive.org/web/20241217114705/https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1970-029C |url-status=dead |archive-date=2024-12-17 |website=NASA}}</ref>

Hover times were maximized on the last four landing missions by using the Service Module engine to perform the initial descent orbit insertion burn 22 hours before the LM separated from the CSM, a practice begun on Apollo 14. This meant that the complete spacecraft, including the CSM, orbited the Moon with a {{convert|9.1|nmi|km|adj=on}} perilune, enabling the LM to begin its powered descent from that altitude with a full load of descent stage propellant, leaving more reserve propellant for the final approach. The CSM would then raise its perilune back to the normal {{convert|60|nmi|km}}.<ref>{{Citation
| last = McDivitt
| first = James A.
| author-link = James McDivitt
| title = Apollo 14 Mission Report
| chapter = 6. Trajectory
| publisher = NASA
| date = May 1971
| chapter-url = http://www.hq.nasa.gov/alsj/a14/a14mr06.htm
| access-date = September 24, 2012
| archive-date = August 5, 2011
| archive-url = https://web.archive.org/web/20110805105053/http://www.hq.nasa.gov/alsj/a14/a14mr06.htm
| url-status = live
}}</ref>

===Extended J-class missions===
[[File:Apollo 15 Engine Bell.jpg|thumb|right|Decreased clearance led to buckling of the extended descent engine nozzle on the landing of [[Apollo 15]].]]
The Extended Lunar Module (ELM) used on the final three [[List of Apollo missions#Alphabetical mission types|"J-class missions"]]—[[Apollo 15]], [[Apollo 16|16]], and [[Apollo 17|17]]—was upgraded. The descent engine thrust was increased by the addition of a {{convert|10|in|mm|adj=on}} extension to the [[Bell nozzle|engine bell]], and the descent propellant tanks were enlarged. A waste storage tank was added to the descent stage, with plumbing from the ascent stage. These upgrades allowed stays of up to 75 hours on the Moon.<ref name=":4">{{Cite web |last=Salamé Páez |first=Ricardo |title=Building LM-11: Apollo 16's Orion |url=https://www.ninfinger.org/models/LM-11/LunarModuleOrion.html}}</ref> The [[Lunar Roving Vehicle]] was folded up and carried in Quadrant 1 of the descent stage. It was deployed by the astronauts after landing.<ref name=":4" />