As the year 1966 progressed, NASA was pushing hard to keep to its schedule so that Apollo could land on the Moon before the end of the decade. But before the first manned test flight, Apollo 1, could lift off for Earth orbit, a whole range of tests was required to certify that Apollo was ready to carry a crew. These tests not only included unmanned flights of actual hardware, but manned “flights” that would subject the spacecraft to the rigors of space without ever leaving the ground.

Simulating Space on the Earth

At this stage of the Apollo program, there were two versions of the Apollo spacecraft being built by the spacecraft’s prime contractor, North American Aviation (which, after decades of corporate mergers, is now part of Boeing). The first variant, designated Block I, was meant to be a prototype for test flights in low Earth orbit in order to verify the basic Apollo CSM (Command-Service Module) design. Lessons learned from constructing and flying these versions would be incorporated into the improved Block II Apollo CSM which would include all of the equipment required to support a flight to the Moon. The Apollo CM (Command Module), which carried the astronauts during their mission and the recovery systems needed to return them safely to Earth, was conical in shape with a diameter of 3.9 meters and a height of 3.2 meters. The SM (Service Module), which included all the systems and consumables needed to support the astronauts and their mission, was a cylinder with the same diameter. Its appearance was dominated by the 91-kilonewton Aerojet AJ10-137 engine of the Service Propulsion System (SPS). The total height of the CSM was 11 meters and the Block I version had a nominal launch mass in excess of 20 metric tons.

The first flight-ready piece of Apollo hardware to be test flown was the CM-002 (Command Module number 002). It was used in the final launch abort test, designated Apollo A-004, using a Little Joe II rocket on January 20, 1966. During a successful flight which lasted less than seven minutes, CM-002 was subjected to a punishing tumbling abort situation which pushed the capsule to its design limits (see “The First Launch of Apollo Flight Hardware”). The first flight of Apollo hardware into space followed on February 26 during the AS-201 mission where CSM-009 (Command-Service Module number 009) successfully flew a 37-minute suborbital flight which provided a test of key Apollo hardware including the new Saturn IB rocket (see “The First Flight of the Apollo-Saturn IB”). On the AS-202 mission launched on August 25, CSM-011 flew a longer suborbital test flight lasting about an hour and a half which qualified many key systems for manned orbital flight including subjecting the CM heat shield to stressful reentry heating (see “AS-202: The Last Test Flight Before Apollo 1”).

Before a crew could fly Apollo into space for the first time during the upcoming Apollo 1 mission, more tests were required to verify the flightworthiness of Apollo. One means of doing so involved vacuum chamber tests employing flight-ready hardware. On April 13, 1966 three North American engineers – Richard Erman, John Moyles and Norman Abell – completed a simulated two-week mission with a Block I CM inside of a five-meter vacuum chamber at North American’s facility in Downey, California nicknamed “the bell jar”. While this proved that the CM could support a crew, a more thorough thermal-vacuum test of the complete CSM was required before the Apollo 1 mission could fly in February 1967.

The facilities for just such a test had been completed in 1965 at what was then known as NASA’s Manned Spacecraft Center in Houston, Texas (MSC, which is today known as the Johnson Space Center). The newly completed Space Environment Simulation Laboratory (SESL) in MSC’s Building 32 included two large man-rated vacuum chambers designed to test space hardware including complete spacecraft. The larger of the two, Chamber A, had an interior space that was 36 meters tall and 17 meters in diameter which could accommodate a test article up to 23 meters tall and 7.6 meters in diameter with a mass of up to 68 metric tons – more than large enough to hold a complete Apollo CSM standing vertically.

SESL’s Chamber A was fitted with a vacuum pump system which was capable of reducing the internal pressure to about 1.3 millibars in three hours (equivalent to the atmospheric pressure at an altitude of about 46 kilometers) and down to a minimum of 1.3 nanobars (equivalent to an altitude of about 210 kilometers) after another 16 hours. In an emergency, the air pressure could be raised to 410 millibars in 30 seconds with a dry nitrogen and oxygen mixture to allow rescue crews quick access to the spacecraft and its crew. Full repressurization was possible in as little as 90 seconds. The walls of the chamber were cooled to -173° C with liquid nitrogen to simulate the cold of space while banks of carbon arc lamps located on the top and side of the chamber simulated the Sun.

For the thermal-vacuum tests inside SESL’s Chamber A, the Apollo CSM was mounted on a platform which could be rotated through 180° allowing the angle of the spacecraft with respect to the solar simulators to be changed as required. Access to the spacecraft was provided via a manlock at an elevation of 9.4 meters on the side of Chamber A fitted with an elevated walkway which reached out to and encircled the spacecraft being tested. This walkway could split along its centerline and would be moved out of the way during spacecraft testing.

Much of the ground support equipment for these tests was virtually identical to that to be used at Kennedy Space Center for launch. But in addition to these standard connections, others were included specifically to support various SESL tests. Since no propulsion system tests would be made inside the vacuum chamber, the spacecraft’s various propellant tanks were filled with a water-glycol mixture which could be dumped into tanks outside of the chamber when the effects of propellant usage were to be simulated. Since testing of Apollo’s power-producing fuel cell system was deemed essential, provisions were made to supply the hydrogen and oxygen reactants they required from storage tanks outside the chamber to minimize the explosion risk in case of a leak.

The First Thermal Vacuum Tests

For the thermal-vacuum tests at SESL, the first human-rated production Apollo spacecraft, CSM-008, was chosen and outfitted for the task. In addition to changes needed to support testing Apollo hardware at SESL, there were more mundane modifications made like changes in the astronaut’s couches and the inclusion of additional padding to make the crew more comfortable in a one-g environment. Since the completed CSM was too large to fit through even the large 12-meter door of Chamber A, each individual module had to be moved into the chamber and stacked on top of the test platform. Before actual Apollo flight hardware was used in Chamber A, testing of all of the handling and assembly procedures was performed and completed in April of 1966 using a boilerplate model of the CSM.

The components of CSM-008 arrived at MSC on May 5 and 9, 1966. After unpacking and checkout, the modules were moved inside of Chamber A for assembly on May 17. Two tests were planned with CSM-008: the first was a 94-hour unmanned test to demonstrate the capabilities of the CSM and verify its compatibility with SESL’s ground support equipment. The second would be a 183-hour test with a volunteer crew of three engineers from MSC’s Flight Crew Support Division that would demonstrate the adequacy of the Block I Apollo spacecraft for the upcoming Apollo 1 manned test flight. The primary crew consisted of Donald R. Garrett, Joel M. Rosenweig and Neil B. Anderson with Joseph A. Gagliano, William M. Anderson and Michael K. Lake serving as their backups. All of the crew members were former or current military pilots on assignment to NASA.

The unmanned test started on July 26, 1966 and almost immediately encountered a problem – a leak in the CM’s side crew hatch. It was determined that the issue was the slow decrease in pressure inside Chamber A during pump down which was too slow to allow a proper seal (a problem that was not expected with the faster change in pressure during an actual ascent). The problem as resolved by temporarily increasing the CM’s internal pressure by 34 to 70 millibars after hatch closure for the initial phase of the chamber’s second pump down. Once the pressure inside Chamber A had dropped sufficiently, the pressure inside the CM cabin would be decreased to its operational pressure of 345 millibars. With the hatch issue resolved, the test proceeded with only one problem of note: ice built up and blocked a steam duct in the Environmental Control System (ECS) through which cabin air passed. After using the solar simulator to help remove the ice, subsequent blockage was avoided with a procedural change in the operation of the ECS water boiler.

With the successful conclusion of the initial unmanned test, preparations were immediately begun for a crewed test of CSM-008. On August 1, 1966 at 10:15 PM CDT, Garret, Rosenweig and Anderson entered CSM-008 wearing the new A1C Apollo space suits for their eight-day test. The 19-hour pump down took twice as long as expected because of issues with the chamber’s emergency repressurization system which required repairs as well as a leak in the system installed to sample and analyze the CM’s cabin atmosphere during the thermal-vacuum tests. Eventually, the chamber’s pressure stabilized at 8.2 nanobars – higher than the minimum possible for Chamber A but still sufficiently low for the tests to proceed.

These initial problems were only the beginning for this “test flight”. Issues with the chamber’s solar simulators resulted in several holds forcing changes in the test schedule. The spacecraft’s urine dump line froze forcing the crew to store their waste onboard. Frozen water also eventually blocked the fuel cells’ hydrogen purge line and hydrogen vent. Two windows on the CM began fogging up as water condensed in the dead space between the glass panes – a problem that would persist to some degree even through the early Block II Apollo manned flights. Condensation on the walls and instrument panels became so severe that they became dripping wet.

During the course of the test a powerful thunderstorm, which the crew could hear even inside their spacecraft (with the vibrations being transferred through the vacuum chamber structure to the CSM, of course), caused the power in the SESL and CSM-008 to fail. In the dark, the crew members were forced to don their spacesuits because the cabin life support system had failed along with the power. According to an interview decades later with Neil Anderson, after a couple of minutes the lights came back on and the crew discovered that all three of them were trying to don the same suit! As a final indignity, the crew was forced to remove their underwear when it was discovered that its fabric was outgassing poisonous lithium fluoride gas. The crew’s frustration with the test was reflected in their log which stated “the crew is losing confidence with the environment”. It was with great relief that the test was finally concluded after about 182 hours at 12:30 CDT on August 9.

The Final “Flight” of CSM-008

Based on the results of the first manned test with CSM-008, a laundry list of changes in hardware and procedures were recommended. And because of these problems and a host of other minor issues which were encountered, the decision was made to perform a second manned test lasting 173 hours in order to certify the flightworthiness of the Block I Apollo. For this second test, CSM-008 would be modified to emulate the configuration of CSM-012, which would be used for the Apollo 1 mission, as closely as possible. In addition to system modifications and outright replacements of faulty hardware to resolve problems encountered during the first manned test, the side crew hatch was modified to include a scientific airlock which was planned for use in later Block I Apollo missions.

During the review of the first manned thermal-vacuum test, Deke Slayton, who was the Director of Flight Crew Operations at MSC at the time, recommended that future manned tests in the vacuum chamber include a doctor to monitor the health of the crew better. In the end, it was decided that the second manned test of CSM-008 would include two astronauts: Joseph P. Kerwin, who became an astronaut in June 1965 as part of the first science-astronaut group and was the only medical doctor in NASA’s astronaut corps at that time, and Edward G. Givens, who had been chosen as part of NASA’s fifth group of astronauts only a few months earlier in April 1966. Joseph A. Gagliano, a USAF pilot assigned to MSC who was part of the backup crew of the first manned test, rounded out the crew for the second test.

As CSM-008 was being prepared for its second manned test to start on October 25, 1966, a procedural error led to the loss of two of the three fuel cells when water backed up into the units. The decision was made to perform the test with only a single fuel cell with ground power providing the balance of the spacecraft’s requirements. The three-man crew was inserted into CSM-008 on schedule but a water flowmeter failure in the ECS forced the test to be scrubbed and the crew was removed from the spacecraft. On October 26, Kerwin, Givens and Gagliano boarded CSM-008 a second time to start their week-long mission.

The pump down of Chamber A took longer than expected due to leaks in the lines to ground support equipment and was not completed until October 28 with the pressure levelling out at 13 nanobars. Over the coming days, the crew experienced only minor problems as they and the ground crews worked through their assigned test program. Attempts to perform a urine dump failed because of a blockage in the line. Analysis following the test had shown that crystals of urine salts, which had built up from the first manned test, had blocked the line. Problems were also encountered during the testing of the science airlock. Testing of the emergency oxygen-supply system, however, demonstrated its ability to maintain cabin pressure after suffering a 1.3-centimeter meteorite hole.

Early on the evening of October 30, the remaining fuel cell on CSM-008 failed forcing the test to continue on ground power alone. A subsequent attempt to transfer potable water from the SM to a storage tank in the CM failed leaving the crew with only 36 hours of drinking water. A second attempt to transfer water the following day was successful allowing the test to continue. Chamber A was finally repressurized on November 1 ending the second manned test of CSM-008. While problems had been encountered, the tests were considered a success and the configuration of CSM-012 was certified for the upcoming Apollo 1 mission.

Although there had been a frustrating list of issues raised by the testing of CSM-008, it was the purpose of the thermal-vacuum tests to uncover such issues before they were encountered during a manned mission so that they could be more easily corrected. All together, 14 hardware and another 14 procedural changes were made as a result of the CSM-008 “test flights”. Unfortunately, other problems with the Block I Apollo design led to an accidental fire inside CM-012 on January 27, 1967 during a countdown rehearsal for the Apollo 1 mission resulting in the tragic deaths of astronauts Gus Grissom, Ed White and Roger Chaffee (see “The Future That Never Came: The Unflown Mission of Apollo 1“). All testing of Apollo hardware at SESL was suspended as the cause of the fire was investigated. In another sad postscript to the CSM-008 “missions”, Ed Givens died in a car accident on June 6, 1967 after serving as part of the support crew for the Apollo 1 mission. Despite the issues raised by the Apollo 1 accident, the usefulness of the thermal-vacuum tests at SESL had been clearly demonstrated and would be repeated with both the Block II Apollo (with Joe Kerwin’s participation) as well as the Lunar Module two years later as the Apollo program recovered.

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Related Reading

“AS-202: The Last Test Flight Before Apollo 1”, Drew Ex Machina, August 25, 2016 [Post]

“The Saturn 500F: The Moon Rocket That Couldn’t Fly”, Drew Ex Machina, September 23, 2016 [Post]

“The Future That Never Came: The Unflown Mission of Apollo 1”, Drew Ex Machina, January 27, 2017 [Post]

General References

Marc Cecotti, “Interview de Neil R. Anderson”, 2004 [Interview]

James C. McLane, Jr., Apollo Experience Report – Manned Thermal-Vacuum Testing of Spacecraft, NASA TN D-7610, March 1974

Lori C. Walters, To Create Space on Earth: The Space Environment Simulation Laboratory and Project Apollo, NASA/CR-2003-208933, February 2003