Editing Skylab Rescue (section)

==History==
Plans for outfitting an [[Apollo Command/Service Module]] (CSM) as a space rescue vehicle date back to November 1965 when [[North American Rockwell]] technicians conceived the possibility of a rescue mission for astronauts trapped in [[lunar orbit]].<ref>"[https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720067283_1972067283.pdf 4-Man Apollo Rescue Mission]" ''Nasa Technical Reports Server''. Retrieved April 18, 2011</ref><ref>{{cite web|url=https://www.wired.com/wiredscience/2012/06/apollo-lunar-orbit-rescue-1965/|title=Beyond Apollo: Apollo Lunar Orbit Rescue (1965)|last=Portree|first=David S.F.|date=October 6, 2012|access-date=January 12, 2013}}</ref> After a rescue mission in Earth orbit was depicted in the 1969 film ''[[Marooned (1969 film)|Marooned]]'', the company revived the concept in November 1970.<ref name="astrorescue"/> [[Marshall Space Flight Center]] issued a formal Mission Requirements document on 17 May 1972, with subsequent revisions.<ref name="missionreq"/>{{Rp|iii}}

[[Skylab 3]] astronauts [[Alan Bean]] and [[Jack Lousma]] helped design the "field modification kit" to use a standard CSM for rescue, and would have flown the CSM for their mission to rescue [[Skylab 2]] if necessary.<ref name="evans20120812">{{Cite web |last=Evans |first=Ben |date=2012-08-12 |title=Launch Minus Nine Days: The Space Rescue That Never Was |url=https://www.americaspace.com/2012/08/12/launch-minus-nine-days-the-space-rescue-that-never-was/ |access-date=2020-07-09 |website=AmericaSpace |language=en-US}}</ref> The standard Skylab Command Module accommodated a crew of three with storage lockers on the aft bulkhead for resupply of experiment film and other equipment, as well as the return of exposed film, data tapes and experiment samples. To convert the standard CSM to a rescue vehicle, the storage lockers were removed and replaced with two crew couches to seat a total of five crewmen.<ref name="astrorescuecm"/> The biggest risk in a rescue was the three upper seats "stroking" or collapsing onto the two lower seats in a rough landing, but no stroking occurred in previous missions.{{r|evans20120812}}

===AS 208===
Soon after [[Skylab 3]]'s launch the crew's CSM developed a problem with Quad B, one of its four reaction control system thrusters. On August 2, 1973, six days later, a snowstorm-like effect outside the station startled the crew during breakfast. What appeared to be "a real blizzard" was fuel leaking from Quad D, opposite from Quad B.{{r|evans20120812}} The malfunctions left two available quads, and while the spacecraft could operate with just one, the leaks posed a possible risk to other systems.<ref name=shayler2001>{{cite book|last=Shayler|first=David J.|title=Skylab: America's Space Station|year=2001|publisher=Springer|location=Berlin|isbn=1-85233-407-X|url=https://books.google.com/books?id=X4WaYqQDVKwC&pg=PA208}}</ref>{{rp|208}} The fuel for all quads and the main [[service propulsion system]] (SPS) engine were from the same batch; if the SPS fuel was contaminated, the CSM might not be able to [[deorbit]].{{r|evans20120812}}

NASA considered bringing the crew home immediately,<ref name="time"/> but because the astronauts were safe on the station with ample supplies and because plans for a rescue flight existed,{{r|shayler2001}}{{rp|209}} the mission continued while the [[Saturn IB]] rocket AS 208 with CSM 119<ref name="astrorescuecm">Wade, Mark. "[http://www.astronautix.com/craft/apouecsm.htm Apollo Rescue CSM] {{webarchive|url=https://web.archive.org/web/20090317010102/http://astronautix.com/craft/apouecsm.htm |date=2009-03-17 }}". ''Encyclopedia Astronautica''. Retrieved April 10, 2009.</ref> was assembled in the [[Vehicle Assembly Building]] at [[Kennedy Space Center Launch Complex 39|Launch Complex 39]] for possible use. It was at one point rolled out to LC-39B.

NASA announced on August 4 that Skylab 3 and [[Skylab 4]] backup crewmen [[Vance Brand]] and [[Don Lind]] would fly any rescue mission; they had immediately begun training for the flight once the second quad had failed on August 2. After engineers found that the leaks would not disable the spacecraft, the two men used simulators to test reentry using two quads. If ground personnel worked 24 hours a day and skipped some tests, the mission could launch on September 10,<ref name="time">"[https://web.archive.org/web/20110629033729/http://www.time.com/time/magazine/article/0,9171,907680-1,00.html Skylab's New Crisis: A Rescue Mission?]" ''[[Time (magazine)|TIME]]'', August 13, 1973. Retrieved April 10, 2009.</ref><ref name="livingandworking">Benson, Charles Dunlap and William David Compton. ''[https://history.nasa.gov/SP-4208/contents.htm Living and Working in Space: A History of Skylab]''. NASA publication SP-4208.</ref>{{Rp|299}} and would last no more than five days.<ref name="missionreq"/>{{Rp|2–6}}{{r|shayler2001}}{{rp|208–209}} The astronauts would attempt to prepare Skylab for further use but returning experimental data and diagnosing the cause of the problem were more important,<ref name="missionreq"/>{{Rp|2-1}} with Lind choosing what would be brought back.{{r|shayler2001}}{{rp|211}}<ref name="lindoh">[http://www.jsc.nasa.gov/history/oral_histories/LindDL/linddl.pdf Don L. Lind oral history transcript], NASA Johnson Space Center Oral History Project, May 27, 2005.</ref> Human urine and feces samples and [[Apollo Telescope Mount]] and other film were the priorities.{{r|evans20120812}} Although Skylab had two docking ports the primary one would be used if possible, jettisoning the Skylab crew's CSM if necessary.<ref name="missionreq"/>{{Rp|2-2,3,8}}

While many within NASA believed that the rescue mission would occur, within hours of the failure of the second quad the agency canceled the rescue mission. Beyond NASA's conclusion that the failed quads would not disable the Skylab 3 CSM and the SPS fuel was uncontaminated, Brand and Lind had already shown during their training as backup Skylab crewmen that a reentry with failed quads was safe. They also devised a method to deorbit with the command module's attitude control system. Later joking that they were "very efficient but perfectly stupid, because we have literally worked ourselves out of the mission", Brand and Lind continued to train for a rescue mission, as well as for their backup roles,{{r|shayler2001}}{{rp|209–211}}{{r|lindoh}}{{r|evans20120812}} but the Skylab 3 crew was able to complete its full 59-day mission on the station and safely return to Earth using the two functional RCS thruster quads,<ref name="belew1977">Belew, Leland. F. (editor) ''[https://history.nasa.gov/SP-400/contents.htm Skylab, Our First Space Station]'' NASA publication SP-400.</ref>{{Rp|103–4}} using the SPS engine once instead of twice as precaution.{{r|evans20120812}}

===AS 209===
[[Image:SkylabRescue.jpg|thumb|alt=Black-and-white picture from inside a tall building with a space capsule being lifted from the top of a rocket|Skylab Rescue [[Apollo CSM|CSM]] being removed from its [[Saturn IB]] following the successful recovery of [[Skylab 4]] (19 February 1974)]]
After the Skylab 4 launch, another rescue flight was assembled as a backup contingency. The Saturn IB rocket AS 209 was assembled in the Vehicle Assembly Building at Launch Complex 39 for possible use. It also used the CSM 119 Command Module that was to be launched with Brand and Lind.

There were also plans for a short 20-day [[Skylab 5]] flight that would use this backup CSM. The crew, likely consisting of Brand, Lind, and Skylab backup Science Pilot [[William B. Lenoir]], would have performed some scientific research and closed out the station until the [[Space Shuttle]] was operational. However, the extension of Skylab 4 from fifty-six to eighty-four days obviated the need for the additional mission.