Editing Apollo 4 (section)

==Background==
In 1961 [[U.S. President]] [[John F. Kennedy]] proposed that his nation land an astronaut on the [[Moon]] by the end of the decade, with a safe return to Earth.<ref name = "mission overview">{{cite web|title=Apollo 11 Mission Overview|url=https://www.nasa.gov/mission_pages/apollo/missions/apollo11.html|date=December 21, 2017|access-date=February 14, 2019|publisher=[[NASA]]}}</ref> One of the early choices that had to be made to accomplish this goal was what launch vehicle to use. [[NASA]] decided on the Saturn{{nbs}}C-5 rocket, a three-stage launch vehicle based on rockets already in development. In 1962 this was approved by NASA, which contemplated an initial test launch in 1965 and a first crewed flight by 1967, leaving plenty of time to accomplish Kennedy's goal.{{sfn|Orloff & Harland 2006|pp=21–22}} In early 1963, NASA redesignated the C-5 as the [[Saturn&nbsp;V]].{{sfn|Bilstein 1996|p=60}}

After considerable debate within NASA, it was decided in late 1962 that lunar missions would have a "[[lunar orbit rendezvous]]" mode whereby the complete Apollo spacecraft would be propelled towards lunar orbit by the third stage of the launch vehicle, the [[S-IVB]]. Once in lunar orbit, the astronauts who would land would enter what was then known as the [[Lunar Excursion Module]], which would separate from the rest of the spacecraft, land, and after taking off again be discarded once the crew had transferred back. The remainder of the vehicle would then return to Earth.{{sfn|Orloff & Harland 2006|pp=25–26}} The launch facilities under development would not be sufficient for the new launch vehicle, and in 1962, NASA announced plans for a new complex on the Florida coast from which the Apollo lunar missions could be launched.{{sfn|Bilstein 1996|p=70}} This was dubbed the Launch Operations Center, but after [[Assassination of John F. Kennedy|Kennedy's assassination]] in November 1963 was renamed the [[John F. Kennedy Space Center]] (KSC).{{sfn|Orloff & Harland 2006|p=34}} Apollo{{nbs}}4 was the first flight from KSC, and the first using [[Launch Complex 39]] (LC-39) there, built to accommodate the Saturn{{nbs}}V.{{sfn|Press Kit|pp=30–31}}

The first three flights carrying Apollo equipment were launched using [[Saturn&nbsp;IB]]s. This smaller launch vehicle did not use the facilities at KSC, but issues resolved by Saturn{{nbs}}IB flights would be valid for those to be launched by the Saturn{{nbs}}V. Both the Saturn{{nbs}}IB and the Saturn{{nbs}}V would use a S-IVB, though the IB would use it as its second, final stage, rather than the third stage as on the Saturn{{nbs}}V. Thus, many of the [[flight qualification]]s for the payload the Saturn{{nbs}}V would carry could be resolved without having to expend one of the large launch vehicles.<ref>{{cite book |last1=Benson |first1=Charles D. |last2=Faherty |first2=William Barnaby |title=Moonport: A History of Apollo Launch Facilities and Operations |url=https://www.hq.nasa.gov/office/pao/History/SP-4204/contents.html |access-date=September 28, 2021 |year=1978 |publisher=NASA |id=NASA SP-4204 |chapter=The Apollo-Saturn IB Space Vehicle |chapter-url=https://www.hq.nasa.gov/office/pao/History/SP-4204/ch17-3.html |url-status=dead |archive-date=January 23, 2008 |archive-url=https://web.archive.org/web/20080123133438/https://www.hq.nasa.gov/office/pao/History/SP-4204/contents.html }} Ch.17-3.</ref> In addition to flight-qualifying the hardware, it was necessary to prove that the ground systems at KSC could successfully launch a Saturn V before risking the lives of astronauts on one.{{sfn|Saturn V evaluation|p=xxxviii}}

Three Saturn IB launches (in order of launch, [[AS-201]], [[AS-203]] and [[AS-202]]) took place in 1966; all were successful. According to Charles D. Benson and William B. Flaherty in their history of KSC, "The Apollo-Saturn{{nbs}}IB launches of 1966 represented important gains for NASA's launch team. [[LC-34]] and [[LC-37]], testbeds for automated [[Operations and Checkout Building|checkout]], were found wanting. In the twenty months between AS-201 and SA-501 [Apollo{{nbs}}4], KSC corrected the major automation problems. Without these trial and error advances, SA-501, the toughest launch in Apollo's history, would have been far more difficult."<ref>{{cite book |last1=Benson |first1=Charles D. |last2=Faherty |first2=William Barnaby |title=Moonport: A History of Apollo Launch Facilities and Operations |url=https://www.hq.nasa.gov/office/pao/History/SP-4204/contents.html |access-date=September 28, 2021 |year=1978 |publisher=NASA |id=NASA SP-4204 |chapter=More Launches of the Saturn IB |chapter-url=http://www.hq.nasa.gov/office/pao/History/SP-4204/ch17-7.html |url-status=dead |archive-date=January 23, 2008 |archive-url=https://web.archive.org/web/20080123133438/https://www.hq.nasa.gov/office/pao/History/SP-4204/contents.html }} Ch.17-7.</ref>