First test flight of the Apollo Saturn V rocket
Apollo 4 (November 9, 1967), also known as SA-501, was the uncrewed first test flight of the Saturn V launch vehicle, the rocket that eventually took astronauts to the Moon. The space vehicle was assembled in the Vehicle Assembly Building, and was the first to be launched from Kennedy Space Center (KSC) in Florida, ascending from Launch Complex 39, where facilities built specially for the SaturnV had been constructed.
Apollo 4 was an "all-up" test, meaning all rocket stages and spacecraft were fully functional on the initial flight, a first for NASA. It was the first time the S-IC first stage and S-II second stage flew. It also demonstrated the S-IVB third stage's first in-flight restart. The mission used a BlockI command and service module modified to test several key BlockII revisions, including its heat shield at simulated lunar-return velocity and angle.
The launch was planned for early 1967, but delayed to November9 because of problems with various elements of the spacecraft and difficulties during pre-flight testing. Additional inspections were also required after a fire killed the Apollo 1 crew in January 1967. 
The mission splashed down in the Pacific Ocean slightly less than nine hours after launch, having achieved its objectives. NASA considered the mission a complete success, proving that the SaturnV worked, an important step towards achieving the main objective of landing astronauts on the Moon, and bringing them back safely, before the end of the 1960s.
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. One of the early choices that had to be made to accomplish this goal was what launch vehicle to use. NASA decided on the SaturnC-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. In early 1963, NASA redesignated the C-5 as the Saturn V.
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. 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. This was dubbed the Launch Operations Center, but after Kennedy's assassination in November 1963 was renamed the John F. Kennedy Space Center (KSC). Apollo4 was the first flight from KSC, and the first using Launch Complex 39 (LC-39) there, built to accommodate the SaturnV.
The first three flights carrying Apollo equipment were launched using Saturn IBs. This smaller launch vehicle did not use the facilities at KSC, but issues resolved by SaturnIB flights would be valid for those to be launched by the SaturnV. Both the SaturnIB and the SaturnV would use a S-IVB, though the IB would use it as its second, final stage, rather than the third stage as on the SaturnV. Thus, many of the flight qualifications for the payload the SaturnV would carry could be resolved without having to expend one of the large launch vehicles. 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.
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-SaturnIB launches of 1966 represented important gains for NASA's launch team. LC-34 and LC-37, testbeds for automated checkout, were found wanting. In the twenty months between AS-201 and SA-501 [Apollo4], 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."
Delays.
In January 1965 Major General Samuel C. Phillips, the Apollo Program Director, scheduled SA-501, the first test flight of the SaturnV, for January 1967. This left little spare time for delay, especially since two additional SaturnV launches were planned to follow in 1967. Many Apollo officials lacked confidence in the proposed launch date, and these misgivings proved accurate. After an explosion involving a liquid oxygen line flowing to LC-39, from which SA-501 was to be launched, there was a potential for a delay of several weeks.
North American Aviation was the contractor for both the S-II SaturnV second stage, and the Apollo command and service module (CSM) spacecraft. NASA had been experiencing problems with North American's schedule, cost, and quality performance on both programs, severe enough that Phillips led a team to North American's facility in California in November and December 1965 to investigate matters, and recommend solutions to the program management problems. He published his findings in a report to his supervisor, George Mueller. Technicians found cracks in the S-II, delaying its test firings prior to acceptance by NASA. As North American worked to fix the S-II, parts of the rocket began to arrive at KSC, beginning with the S-IVB on August 14, 1966, (by Pregnant Guppy aircraft) and followed closely by the first stage S-IC on September 12 (by barge). A spool-shaped "spacer" that took the place of the S-II allowed NASA to stack the vehicle as its checkout proceeded in the Vehicle Assembly Building (VAB). With the S-II still not arrived by November 1966 (it had originally been planned for July), NASA planned January 1967 for its arrival, with launch three months later. The CSM arrived on December 24, 1966, with the S-II arriving on January 21, 1967. Last to arrive was the aft interstage (the structure between the first and second stages), on January 31.
The Apollo 1 fire on January 27, 1967, which killed three astronauts during a launch pad test, threw NASA's schedules into further question – even though SA-501 was uncrewed, NASA officials wanted to closely examine its CSM. NASA had planned to restack the vehicle once this was done, but instead the inspections that took place found a total of 1,407 errors in the spacecraft. Inspectors found many haphazardly routed and skinned wires, prime material for short circuits.
Other problems were discovered, such as an extra, out-of-place bolt in one of the J-2 engines; NASA was concerned not only with retrieving the surplus hardware, but also with discovering how it got there. A meeting in March 1967, with Phillips in attendance, disclosed twelve hundred problems with the SaturnV, which the technicians proposed to deal with at the rate of eighty per day. While the CSM was undergoing repairs, the spacer was removed from the vehicle stack, and the S-II positioned. On May 24 it was announced that the S-II would be removed for inspection following the discovery of hairline cracks in another S-II then being constructed, this work being completed by mid-June, after which the CSM was also returned to the stack, the first time the launch vehicle and spacecraft had been fully assembled. It was rolled out to LC-39 on August 26, 1967, where it was joined by the Mobile Servicing Structure that allowed access to the launch vehicle and spacecraft two days later, also transported by crawler. This was the first time a NASA spacecraft had been assembled away from its launch site, something allowing protection from Florida's hot and humid climate for equipment and personnel.
The countdown demonstration test had been scheduled for September 20 but was soon rescheduled for the 25th and did not begin until the evening of the 27th. By October2 another two days had been lost to delays, but by October4 it reached launch minus 45 minutes. Then a computer failed, and the count, reset to minus 13 hours before launch, resumed on October 9. More computer and equipment problems appeared. By then, the launch team was exhausted and a two-day break was declared. The test was completed on October 13, meaning that it took three weeks rather than the expectation of a week or slightly over. With world attention on the launch, NASA public relations head Julian Scheer brought the skeptical questions from the media as to whether Apollo4 would ever fly to the attention of NASA Administrator James E. Webb, leading to a heated meeting in which Webb said he would announce the launch date when he wanted to.
These difficulties provided the launch crew with valuable experience, but meant that Apollo4 could not be launched at the earliest until November 7. A flight readiness review on October 19 cleared Apollo4 for launch, assuming the remaining tests and modifications were satisfactorily completed. Concerned about the potential for leaks in the Teflon seal rings and drain valves of the liquid oxygen tanks on board the vehicle due to the long time it had been sitting on the launch pad in the Florida sun, on November2 Phillips postponed the launch until November9.
Objectives.
The purpose of Apollo 4 (together with the SaturnV's other uncrewed test flight, Apollo6) was to qualify the launch vehicle, the Apollo spacecraft, and the ground systems, for the crewed lunar landing missions that would follow. In addition to being the first flight of the SaturnV, Apollo4 marked the first flight for two of its stages: the S-IC first stage and the S-II second stage (the S-IVB had flown as part of the SaturnIB).
Objectives for the Apollo 4 mission were to gain flight data on the SaturnV and spacecraft structural integrity and mutual compatibility, including on flight loads and during the separations as each SaturnV stage was exhausted and was discarded. NASA also wanted data on subsystem operations, including the emergency detection subsystem, and sought to evaluate the Apollo CM's heat shield under conditions simulating a return from a lunar mission. NASA was also seeking to test the restart capability of the S-IVB in space. These objectives would all be achieved.
Equipment.
Apollo 4 carried CSM-017, a BlockI design of the command and service modules meant for testing and for Apollo's early Earth orbit flights. Unlike the BlockII spacecraft which would go to the Moon, it lacked the capability to dock with a lunar module (LM). CSM-017 was made up of command module CM-017 and service module SM-020. CM-017 was the second fully-functional CM to be delivered to NASA; the first, CM-012, was designated for Apollo1, and was severely damaged in the fire. SM-020 was originally to be used in CSM-020, slated for the second SaturnV test, but this changed after SM-017, which was intended to be part of CSM-017, was damaged in an explosion and was scrapped.
Several significant Block II modifications were made to CSM-017 for certification purposes, since no BlockII spacecraft would fly without a crew. These included upgrading the heat shield to BlockII standards, using a BlockII CM-to-SM umbilical connector, and installing BlockII-style VHF and S-band antennae. Additionally, there were modifications to the CM's hatch. The fact that the spacecraft hatch could not be readily opened in case of emergency had trapped the Apollo1 astronauts in the fire that took their lives, and led to a redesign of the hatch. The new hatch was not scheduled to fly until the second SaturnV test (Apollo 6), but its seals were to be flight-qualified on Apollo4 – the hatch window was replaced with a test panel simulating the seals and exterior heat shield. The heat shield was upgraded to BlockII standards since Apollo4's high-speed re-entry into Earth's atmosphere was intended to simulate a return from the Moon. Special equipment had been installed to allow Mission Control to operate the CSM's systems remotely, and there was a camera that would automatically take pictures out of one of the CM's windows on its final orbit. Since Apollo4 carried no crew the CM lacked couches, controls and displays.
A Lunar Module Test Article, LTA-10R, was carried, and remained inside the Spacecraft–LM