Editing Marshall Space Flight Center (section)

====Saturn launch vehicles====
On May 25, 1961, just 20 days after Shepard's flight, President [[John F. Kennedy]] committed the US to a lunar landing by the end of the decade.<ref>John F. Kennedy; "Special Message to the Congress on Urgent National Needs." Delivered in person before a joint session of Congress, May 25, 1961</ref> The primary mission of MSFC under the [[Apollo program]] was developing the heavy-lift Saturn family rockets. This required the development and qualification of three new liquid-fueled rocket engines, the [[J-2 (rocket engine)|J-2]], [[F-1 (rocket engine)|F-1]], and [[H-1 (rocket engine)|H-1]]. Additionally, the existing [[RL10]] was improved for use on the Saturn S-IV stage. [[Leland F. Belew]] managed the Engine Development Office.<ref>Bilstein, Roger E.; [https://history.nasa.gov/SP-4206/sp4206.htm "Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicles] {{Webarchive|url=https://web.archive.org/web/20210209041807/https://history.nasa.gov/SP-4206/sp4206.htm |date=2021-02-09 }}" NASA History Series;</ref> The F-1 engine is the most powerful single-nozzle liquid-fueled rocket engine ever used in service; each produced 1.5-million-pounds thrust. Originally started by the U.S. Air Force, responsibility for the development was taken over by ABMA in 1959, and the first test firings at MSFC were in December 1963.{{citation_needed|date=July 2019}}

The original vehicle, designated [[Saturn I]], consisted of two propulsion stages and an instrument unit; it was first tested in flight on October 27, 1961. The first stage (S-I) had a cluster of eight H-1 engines, giving approximately 1.5-million-pounds thrust total. The four outboard engines were [[Gimbaled thrust|gimbaled]] to allow vehicle steering. The second stage (SIV) had six gimbaled LR10A-3 engines, producing a combined 90-thousand-pounds thrust. Ten Saturn Is were used in flight-testing of Apollo [[Boilerplate (spaceflight)|boilerplate]] units. Five of the test flights also carried important auxiliary scientific experiments.{{citation_needed|date=July 2019}}

The [[Saturn IB]] (alternatively known as the Uprated Saturn I) also had two propulsion stages and an instrument unit. The first stage (S-IB) also had eight H-1 engines with four gimballed, but the stage had eight fixed fins of equal size fitted to the sides to provide aerodynamic stability. The second stage (S-IVB) had a single J-2 engine that gave a more powerful 230-thousand-pounds thrust. The J-2 was gimbaled and could also be restarted during flight. The vehicle was first flight-tested on February 26, 1966. Fourteen Saturn 1Bs (or partial vehicles) were built, with five used in uncrewed testing and five others used in crewed missions, the last on July 15, 1975.{{citation_needed|date=July 2019}}

The [[Saturn V]], an [[expendable launch system|expendable]] [[Human-rating certification|human-rated]] heavy-lift vehicle, was the most vital element in the Apollo Program. Designed under the direction of [[Arthur Rudolph]], the Saturn V holds the record as the largest and most powerful launch vehicle ever brought to operational status from a combined height, weight, and payload standpoint. The Saturn V consisted of three propulsion stages and an instrument unit. The first stage (S-IC), had five F-1 engines, giving a combined total of 7.5-million-pounds thrust. The S-II second stage had five J-2 engines with a total of 1.0-million-pounds thrust. The third stage (S-IVB) had a single gimballed J-2 engine with 200-thousand-pounds thrust. As previously noted, the J-2 engine could be restarted in flight. The basic configuration for this heavy-lift vehicle was selected in early 1963, and the name Saturn V was applied at that time (configurations that might have led to Saturn II, III, and IV were discarded).{{citation_needed|date=July 2019}}

While the three propulsion stages were the "muscle" of the Saturn V, the [[Saturn V Instrument Unit|Instrument Unit]] (IU) was the "brains." The IU was on a 260-inch (6.6-m) diameter, 36-inch (91-cm) high, ring that was held between the third propulsion stage and the LM. It contained the basic guidance system components – a stable platform, accelerometers, a digital computer, and control electronics – as well as radar, telemetry, and other units. Basically the same IU configuration was used on the Saturn I and IB. With IBM as the prime contractor, the IU was the only full Saturn component manufactured in Huntsville.{{citation_needed|date=July 2019}}

The first Saturn V test flight was made on November 9, 1967. On July 16, 1969, as its crowning achievement in the Apollo space program, a Saturn V vehicle lifted the Apollo 11 spacecraft and three astronauts on their journey to the Moon. Other Apollo launches continued through December 6, 1972. The last Saturn V flight was on May 14, 1973, in the Skylab Program (described later). A total of 15 Saturn Vs were built; 13 functioned flawlessly, and the other two remain unused.{{citation_needed|date=July 2019}}