Editing Apollo Lunar Module (section)

==Operational profile==
At launch, the Lunar Module sat directly beneath the [[Apollo command and service module|command and service module]] (CSM) with legs folded, inside the [[Apollo (spacecraft)#Spacecraft–lunar module adapter (SLA)|Spacecraft-to-LM adapter (SLA)]] attached to the [[S-IVB]] third stage of the [[Saturn V]] rocket. There it remained through Earth parking orbit and the [[trans-lunar injection]] (TLI) rocket burn to send the craft toward the Moon.

Soon after TLI, the SLA opened; the CSM [[Transposition, docking, and extraction|performed a maneuver]] whereby it separated, turned around, came back to dock with the Lunar Module, and extracted it from the S-IVB. During the flight to the Moon, the docking hatches were opened and the Lunar Module pilot entered the LM to power up temporarily and test all systems except propulsion. The Lunar Module pilot performed the role of an engineering officer, monitoring the systems of both spacecraft.

After achieving a lunar parking orbit, the commander and LM pilot entered and powered up the LM, replaced the hatches and docking equipment, unfolded and locked its landing legs, and separated from the CSM, flying independently. The commander operated the flight controls and engine throttle, while the Lunar Module pilot operated other spacecraft systems and kept the commander informed about systems status and navigational information. After the command module pilot visually inspected the [[Landing gear (spaceflight)|landing gear]], the LM was withdrawn to a safe distance, then rotated until the [[Descent propulsion system|descent engine]] was pointed forward into the direction of travel. A 30-second descent orbit insertion burn was performed to reduce speed and drop the LM's [[perilune]] to within about {{convert|50000|ft|km}} of the surface,<ref>{{cite web|url=https://history.nasa.gov/SP-4029/Apollo_11g_Lunar_Orbit_Phase.htm|title=Apollo 11 Lunar Orbit Phase|access-date=July 12, 2017|archive-date=December 26, 2017|archive-url=https://web.archive.org/web/20171226033954/https://history.nasa.gov/SP-4029/Apollo_11g_Lunar_Orbit_Phase.htm|url-status=live}}</ref> about {{convert|260|nmi|km}} uprange of the landing site.
[[File:Earth, Moon and Lunar Module, AS11-44-6643 c.jpg|thumb|{{ship|Lunar Module|Eagle}}, the Lunar Module ascent stage of [[Apollo 11]], in orbit above the Moon. Earth is visible in the distance. Photograph by [[Michael Collins (astronaut)|Michael Collins]] aboard the {{ship|Command module|Columbia}}.]]
As the craft approached perilune, the descent engine was started again to begin powered descent. During this time, the crew flew on their backs, depending on the computer to slow the craft's forward and vertical velocity to near zero. Control was exercised with a combination of engine throttling and attitude thrusters, guided by the computer with the aid of landing radar. During braking, the LM descended to about {{convert|10000|ft|km}}, then, in the final approach phase, down to about {{convert|700|ft|m}}. During final approach, the vehicle pitched over to a near-vertical position, allowing the crew to look forward and down to see the lunar surface for the first time.<ref>
{{cite book
| last = Gatland
| first = Kenneth
| title = Manned Spacecraft, Second Revision
| publisher = Macmillan Publishing Co.
| location = New York
| year = 1976
| pages = 194–196
| isbn = 0-02-542820-9 }}
</ref>

Astronauts flew Apollo spacecraft manually only during the lunar approach.<ref name="agle199809">{{Cite magazine |last=Agle |first=D.C. |date=September 1998 |title=Flying the Gusmobile |url=https://www.airspacemag.com/flight-today/flying-the-gusmobile-218187/ |magazine=Air & Space |language=en |access-date=December 15, 2018 |archive-date=April 3, 2020 |archive-url=https://web.archive.org/web/20200403013717/https://www.airspacemag.com/flight-today/flying-the-gusmobile-218187/ |url-status=live }}</ref> The final landing phase began about {{convert|2000|ft|km}} uprange of the targeted landing site. At this point, manual control was enabled for the commander, who had enough [[liquid rocket propellant|propellant]] to hover for up to two minutes to survey where the computer was taking the craft and make any necessary corrections. If necessary, landing could have been aborted at almost any time by jettisoning the descent stage and firing the ascent engine to climb back into orbit for an emergency return to the CSM. Finally, one or more of three {{convert|67.2|in|m|adj=on}} probes extending from footpads on the legs of the lander touched the surface, activating the contact indicator light which signaled the commander to shut off the descent engine, allowing the LM to settle onto the surface. On touchdown, the probes would be bent as much as 180 degrees, or even break off. The original design used the probes on all four legs, but starting with the first landing (LM-5 on Apollo 11), the one at the ladder was removed out of concern that the bent probe after landing might puncture an astronaut's suit as he descended or stepped off the ladder.

The original [[extravehicular activity]] plan, up through at least 1966, was for only one astronaut to leave the LM while the other remained inside "to maintain communications".<ref>{{cite web |url=https://www.youtube.com/watch?v=6UuRCwsGugg&t=3m20s |title=Landing on the Moon, 1966 episode of MIT's ''Science Reporter'' |via=YouTube (posted by MIT) |date=January 20, 2016 |quote=While one astronaut explores the area around the LEM, the second remains inside to maintain communications. |access-date=December 20, 2017 |archive-date=April 15, 2021 |archive-url=https://web.archive.org/web/20210415173259/https://www.youtube.com/watch?v=6UuRCwsGugg&t=3m20s |url-status=dead }}</ref> Communications were eventually deemed to be reliable enough to allow both crew members to walk on the surface, leaving the spacecraft to be only remotely attended by Mission Control.

Beginning with [[Apollo 14]], extra LM propellant was made available for the powered descent and landing, by using the CSM engine to achieve the {{convert|50000|ft|km|adj=on}} perilune. After the spacecraft undocked, the CSM raised and circularized its orbit for the remainder of the mission.

When ready to leave the Moon, the LM's ascent engine fired, leaving the descent stage on the Moon's surface. After a few course correction burns, the LM rendezvoused with the CSM and docked to transfer the crew and rock samples. Having completed its job, the ascent stage was separated. The Apollo 10 ascent stage engine was fired until its fuel was used up, sending it past the Moon into a [[heliocentric orbit]].<ref name="nasa_apollo10">{{cite web |url=http://www.nasa.gov/mission_pages/apollo/missions/apollo10.html |title=Apollo 10 |date=July 8, 2009 |editor-last=Ryba |editor-first=Jeanne |publisher=NASA |access-date=June 26, 2013 |archive-date=July 23, 2013 |archive-url=https://web.archive.org/web/20130723165654/http://www.nasa.gov/mission_pages/apollo/missions/apollo10.html |url-status=live }}</ref><ref name="disposition">{{cite web|title=Current locations of the Apollo Command Module Capsules (and Lunar Module crash sites)|url=http://nssdc.gsfc.nasa.gov/planetary/lunar/apolloloc.html|website=Apollo: Where are they now?|publisher=NASA|access-date=December 27, 2014|archive-date=July 17, 2011|archive-url=https://web.archive.org/web/20110717164926/http://nssdc.gsfc.nasa.gov/planetary/lunar/apolloloc.html|url-status=live}}</ref> The [[Apollo 11]] ascent stage was left in lunar orbit to eventually crash; all subsequent ascent stages (except for Apollo 13) were intentionally steered into the Moon to obtain readings from seismometers placed on the surface.<ref>{{Cite web |title=New Evidence Suggests Apollo 11's Lunar Ascent Module Could Still Be Orbiting the Moon |url=https://www.discovermagazine.com/technology/new-evidence-suggests-apollo-11s-lunar-ascent-module-could-still-be-orbiting |access-date=2024-05-20 |website=Discover Magazine |language=en}}</ref>