Editing Skylab Rescue (section)

===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}}