Editing Apollo program (section)

===Profile variations===
[[File:AP11 FINAL APPROACH.ogv|thumb|[[Neil Armstrong]] pilots the Apollo [[Lunar Module Eagle|Lunar Module ''Eagle'']] and lands himself and navigator [[Buzz Aldrin]] on the Moon, July 20, 1969.]]

* The first three lunar missions (Apollo 8, [[Apollo 10]], and Apollo 11) used a [[free return trajectory]], keeping a flight path coplanar with the lunar orbit, which would allow a return to Earth in case the SM engine failed to make lunar orbit insertion. Landing site lighting conditions on later missions dictated a lunar orbital plane change, which required a course change maneuver soon after TLI, and eliminated the free-return option.<ref>{{cite book|last1=McDivitt|first1=James A.|title=Apollo 12 Mission Report|date=March 1970|publisher=NASA Manned Spacecraft Center|location=Houston, Texas|page={{Not a typo|5–4}}<!-- A single page in document -->|url=http://www.hq.nasa.gov/alsj/a12/A12_MissionReport.pdf}}</ref>
* After Apollo 12 placed the second of several [[seismometer]]s on the Moon,<ref>{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1969-099C|title=Apollo 12 Lunar Module / ALSEP|access-date=June 15, 2016|website=NASA Space Science Data Coordinate Archive}}</ref> the jettisoned LM ascent stages on Apollo 12 and later missions were deliberately crashed on the Moon at known locations to induce vibrations in the Moon's structure. The only exceptions to this were the Apollo 13 LM which burned up in the Earth's atmosphere, and [[Apollo 16]], where a loss of [[Spacecraft attitude control|attitude control]] after jettison prevented making a targeted impact.<ref>{{cite web |url=http://nssdc.gsfc.nasa.gov/planetary/lunar/apolloloc.html |title=Apollo: Where are they now? |last=Williams |first=David R. |work=[[National Space Science Data Center]] |publisher=NASA |access-date=December 2, 2011}}</ref>
* As another active seismic experiment, the S-IVBs on Apollo 13 and subsequent missions were deliberately crashed on the Moon instead of being sent to solar orbit.<ref>{{cite web|url=https://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/lroc-20100322-apollo13booster.html#.V2JPbfkrLD4|title=Apollo 13's Booster Impact|website=NASA|access-date=June 16, 2016}}</ref>
* Starting with Apollo 13, descent orbit insertion was to be performed using the service module engine instead of the LM engine, in order to allow a greater fuel reserve for landing. This was actually done for the first time on Apollo 14, since the Apollo 13 mission was aborted before landing.<ref>{{cite book|last1=McDivitt|first1=James A.|title=Apollo 14 Mission Report|date=April 1971|publisher=NASA Manned Spacecraft Center|location=Houston, Texas|chapter-url=http://www.hq.nasa.gov/alsj/a14/a14mr07.htm|access-date=19 May 2016|chapter=7.0 Command and Service Module Performance}}</ref>