Apollo 4

Apollo 4, (also known as AS-501), was the first, unmanned test flight of the Saturn V launch vehicle, which was used by the U.S. Apollo program to send the first astronauts to the Moon. The space vehicle was assembled in the Vertical Assembly Building, and was the first to be launched from Launch Complex 39 at the John F. Kennedy Space Center on Merritt Island, Florida, facilities built specially for the Saturn V.

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 Block I Command Service Module (CSM) modified to test several key Block II revisions, including its heat shield at simulated lunar-return velocity and angle.

Originally planned for late 1966, the flight was delayed to November 9, 1967, largely due to development problems of the S-II stage encountered by North American Aviation, the manufacturer of the stage. Delay was also caused, to a lesser extent, by a large number of wiring defects found by NASA in the Apollo spacecraft, also built by North American.

The mission was the first Apollo flight after the stand-down imposed after the Apollo 1 fire which killed the first Apollo crew. It was the first to use NASA's official Apollo numbering scheme established in April 1967, designated Apollo 4 because there had been three previous unmanned Apollo/Saturn flights in 1966, using the Saturn IB launch vehicle.

The mission lasted almost nine hours, splashing down in the Pacific Ocean, achieving all mission goals. NASA deemed the mission a complete success, because it proved the Saturn V worked, an important step towards achieving the Apollo program's objective of landing astronauts on the Moon and bringing them back safely, before the end of the decade.

Objectives
AS-501 was the Saturn V's first flight. At the time, it was the largest launch vehicle to ever attempt a flight. This mission was NASA's first to use "all-up" testing, a decision that goes back to late-1963. George Mueller, the head of the NASA Office of Manned Space Flight at that time, was a systems engineer who previously worked on military missile projects, recognized all-up testing was successfully used to rapidly develop the Air Force's Minuteman ICBM program, and thought it could be used to meet Apollo's schedule. Previously, the way Wernher von Braun's team at the Marshall Space Flight Center, and the old NACA Langley Research Center engineers tested new rockets was by testing each stage incrementally. The Saturn V's test program departed from the conservative incremental approach previously used by the Marshall and Langley engineers. It would be tested all at once, with all stages live and fully flight-worthy, including an Apollo Command/Service Module (CSM). This decision dramatically streamlined the program's test flight phase, eliminating four missions, but it required everything to work properly the first time. Apollo program managers had misgivings about all-up testing but agreed to it with some reluctance since incremental component tests would inevitably push the lunar landing mission past the 1970 goal.

The mission was the first launch from the Kennedy Space Center Launch Complex 39, specifically built for the Saturn V. Since this was an all-up test, it was the S-IC first stage and S-II second stage's first launch. It would also be the first time that the S-IVB third stage would be restarted in Earth orbit, and the first time that the Apollo spacecraft would reenter the Earth's atmosphere at the speed of a lunar return trajectory.

The payload was a CSM, serial number 017. This was a Block I design meant for systems testing, not the Block II spacecraft designed for use with the Lunar Module (LM) on the actual Moon landings. However, several significant Block II modifications were made for certification, since no all-up Block II spacecraft would fly without a crew. The modifications included: a new CM heat shield outer covering; a new CM-to-SM umbilical connector; moving the VHF scimitar antennas from the CM to the SM; a new Unified S-band antenna; and a modified crew compartment hatch.

A dummy LM known as a Lunar Module Test Article, LTA-10R was carried as ballast to simulate the loadings of the LM on the launch vehicle. At 29,500 lb, the LTA-10R was slightly lighter than a nominal LM used on the first lunar landing, which weighed 33,278 lb.

Vehicle assembly


The launch of AS-501 was originally planned for late 1966, but was pushed back by stage development problems to April 1967. The first piece to arrive at the Kennedy Space Center was the S-IVB third stage, built by the Douglas Aircraft Company. Small enough to be transported by a specially built plane, the "Pregnant Guppy" built by Aero Spacelines, Inc., it arrived on August 14, 1966.

The other stages were much larger and had to travel by barge along the Banana River. The S-IC first stage, built by the Boeing Company, arrived next on September 12 from Michoud, Louisiana.

Additional delay caused by North American Aviation
North American Aviation was the contractor for both the S-II Saturn V second stage, and the Apollo Command/Service Module spacecraft. NASA had been experiencing problems with North American's schedule, cost, and quality performance on both programs, severe enough that Apollo program director Samuel C. Phillips sent a team to North American 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.

Saturn V second stage
The S-II development was known to be about a year behind schedule, and the first flight-ready stage did not make its delivery in 1966. In the meantime, vehicle assembly continued, using a huge spool-shaped spacer in its place, in order to gain more experience in the third-stage stack procedure. The S-II did not arrive until January 21, 1967, six days before the fatal Apollo 1 spacecraft fire which killed the first Apollo crew. Upon inspection, cracks were found in the liquid hydrogen tank. These were repaired, the third stage and spacer were removed, and assembly continued with the S-II on February 23.

Apollo spacecraft
CSM 017 had arrived from North American about a month before the Apollo 1 fire, on December 24, 1966. It had already passed a quality-control inspection, but after the fire that destroyed its sister CM 012, it was subjected to an intensive inspection that found a total of 1,407 errors in the spacecraft. Dozens of haphazardly routed and skinned wires were short circuits just waiting to happen. NASA managers came to see the problems for themselves. Director of Launch Operations Rocco Petrone was said to have cursed; Apollo Spacecraft Program Office manager Joseph Francis Shea welled up in tears; and Phillips stood in stunned silence.

The CSM was removed from the stack on February 14, 1967, for repair, which required another four months until it was ready to be re-mated to the rocket on June 20. On August 26, the complete launch vehicle finally rolled out of the Vertical Assembly Building (VAB) - more than eight months after the originally scheduled launch date.

Mission numbering scheme
AS-501 was the first mission to fly under the official Apollo mission numbering scheme approved by Mueller on April 24, 1967. Since the failed first manned flight had been designated Apollo 1 in honor of the crew widows' wishes, and three unmanned Apollo/Saturn IB flights had already occurred, Mueller resumed the numbering sequence at Apollo 4.

Launch preparation
The vehicle's on-pad, pre-launch tests and preparation practice started in September, and encountered several problems with propellant loading and various equipment failures. These pushed the launch into November, but provided valuable lessons learned on the new vehicle. By this time, North American had been purchased by Rockwell Standard Corporation, so launch support was the first provided under the new name, North American Rockwell. On November 6, the 56½ hour countdown sequence began with propellant loading. In total there were 89 trailer-truck loads of LOX (liquid oxygen), 28 trailer loads of LH2 (liquid hydrogen), and 27 rail cars of RP-1 (refined kerosene). This time the problems encountered were few and minor.

Flight
Launch occurred on November 9 at 7:00AM EST (12:00PM UTC). Eight seconds before liftoff, the five F-1 engines ignited, sending tremendous amounts of noise across Kennedy Space Center. To protect from a possible explosion (see below), the launch pads at LC-39 were located more than three miles from the Vertical Assembly Building; still, the sound pressure was much stronger than expected and buffeted the VAB, Launch Control Center and press buildings. Ceiling tiles fell around news reporter Walter Cronkite, covering the launch for CBS News. Cronkite and producer Jeff Gralnick put their hands on the observation window in an effort to stop its powerful vibrations. Cronkite later admitted he was "overwhelmed" by the power of the rocket and the emotion of the moment. His on air description was delivered without his usual poise and reserve as he yelled above the launch noise into his microphone.

"...our building's shaking here. Our building's shaking! Oh it's terrific, the building's shaking! This big blast window is shaking! We're holding it with our hands! Look at that rocket go into the clouds at 3000 feet!...you can see it...you can see it...oh the roar is terrific!..."

- Walter Cronkite

Much like with the Saturn I's maiden flight six years earlier, the fear of a low altitude launch failure, and especially a pad explosion, was high. Several NASA studies had been conducted to assess this scenario by studying previous such accidents (notably the March 1965 Atlas-Centaur disaster), but in all such cases, they involved launch vehicles less than half the size and fuel load of the Saturn V. Such an event would be a catastrophe beyond all proportions (the Soviet N-1 disaster of 1969 however provides a glimpse of what it might have looked like). Fortunately for all concerned, the largest rocket ever built lifted from LC-39A and performed perfectly through all stages of the flight.

The launch placed the S-IVB and CSM into a nearly circular 100 nmi orbit, a nominal parking orbit that would be used on the actual lunar missions. After two orbits, the S-IVB's very first in-space re-ignition put the spacecraft into an elliptical orbit with an apogee of 9297 nmi and a perigee deliberately aimed 45.7 nmi below the Earth's surface; this would ensure both a high-speed atmospheric reentry of the Command Module, and destruction after reentry of the S-IVB. Shortly after this burn, the CSM separated from the S-IVB and fired its Service Module engine to adjust the apogee to 9769 nmi and a perigee of -40 nmi. After passing apogee, the Service Module engine fired again for 281 seconds to change the orbit to a hyperbolic trajectory, increasing re-entry speed to 36,545 ft/s, at an altitude of 400,000 ft and a flight path angle of -6.93 degrees, simulating a return from the Moon.

The CM landed approximately 8.6 nmi from the target landing site northwest of Midway Island in the North Pacific Ocean. Its descent was visible from the deck of the USS Bennington, the prime recovery ship.

Saturn V development
Two motion-picture cameras were mounted on the thrust structure of the S-II second stage, for verification of proper staging sequence. Similar cameras were also mounted on the second Saturn V flight, Apollo 6. The cameras ran at four times normal speed to show the events in slow motion. The camera capsules were jettisoned soon after the first stage separation, at an altitude of about 200,000 ft. They then reentered the atmosphere, and parachuted to the ocean for recovery. Both S-II cameras from Apollo 4 were recovered, so there is footage from both sides of the vehicle.

Documentaries often use footage of a Saturn V launch, and one of the most used pieces shows the interstage between the first and second stages falling away. This footage is usually mistakenly attributed to the Apollo 11 mission, when it was actually filmed on the flights of Apollo 4 and Apollo 6. A compilation of original NASA footage shows the jettisoning of the first stage (S-IC) and the interstage, filmed from the bottom of the second stage (S-II), both from Apollo 4. This is followed by footage of the separation of an S-IVB second stage from the first stage of a Saturn IB. The glow seen on the jettisoned stages is due to the hot, invisible hydrogen-oxygen exhaust of the J-2 engines used by the S-II and S-IVB. The footage also shows the more conspicuous plumes of the solid ullage motors as they push the S-II away from the first stage before the S-II engines are fired.

Earth images


The Command Module contained an automatic 70 mm film camera which captured photographs of almost the entire Earth. For a period of two hours and thirteen minutes as the craft approached and passed its apogee, a total of 755 color images were taken through the Command Pilot's (left-hand) forward-looking window, at altitudes ranging from 7295 to 9769 nmi. The photographs were not of sufficient resolution to obtain detailed scientific data, but were still of geographic, cartographic, meteorologic, oceanographic, geologic and hydrologic interest.

Capsule location
The Command Module is on display at the NASA's John C. Stennis Space Center, Bay St. Louis, Mississippi.