While astronauts Scott and Irwin motored around Hadley Rille, KSC officials turned their attention to the Apollo 16 mission scheduled for March 1972. In early August, North American mated the command and service modules. Three weeks later Grumman joined the two LM stages for their altitude tests. September saw the start of lunar rover checkout and the erection of the S-IC stage. In October the launch vehicle team stacked the Saturn stages. Meanwhile the astronauts went through the crew compartment fit and functional tests and the altitude chamber runs. The spacecraft modules moved out of the chambers in November and landing gear was installed on the lunar module. In December the spacecraft team mated the Apollo spacecraft to the lunar adapter and moved the combination to the assembly building. Twelve days before Christmas Apollo 16 rolled out to the pad.19
The launch team had made relatively few changes to the Apollo 16 spacecraft during the first five months of launch operations. Malfunctions on Apollo 15 prompted two command module changes: replacing panel switches for the spacecraft propulsion system and replacing the main parachutes. One of the three main parachutes had failed to open for the splashdown of Apollo 15, and NASA officials suspected hydrogen embrittlement in the connector links of the suspension lines. After replacing the suspect parts with steel alloy links, North American shipped a new set of parachutes to KSC in mid-November. That same week the launch team replaced the water glycol accumulators in two fuel cells of the service module. When the fuel cells converted oxygen and hydrogen to electricity and water, considerable heat was produced. As it transferred this heat to a series of radiators, the glycol expanded and the excess liquid accumulated in reservoirs. The accumulators had been damaged in September when technicians overpressurized the glycol system during a vacuum-purging test.20
One of the few problem areas in the Saturn operations involved the engine actuators on the S-IC stage. These hydraulic actuators, 1.5 meters in length, swivelled the four outboard F-1 engines to change pitch, yaw, and roll. Actuator tests included the calibration of a recorder in the launch control center. As the actuators swivelled the F-1 engines, a potentiometer sent a voltage to the recorder indicating the direction and amount of movement. During November tests, excessive noise in one actuator interfered with the signal to the control center; the actuator was replaced on the 25 th. The following week Boeing engineers inspected the S-IC LOX and RP-1 tanks for stress corrosion but found no problem.21
Early in the new year a spacesuit alteration and two spacecraft problems delayed the Apollo 16 launch to 16 April. Grumman engineers had increased the capacity of the lunar module batteries and wanted more time to gather test data. At Downey technicians discovered that an explosive device used to separate the command-service and lunar modules would malfunction under certain conditions; modification required additional time. The delay proved a godsend for KSC in late January when a fuel tank in the command module's reaction control system ruptured.22
The hypergolic propellants of the reaction control system, which controlled the attitude of the command module during reentry, were forced from their tanks by high pressure helium gas. Within each fuel tank, the fuel was inside a teflon bladder. As gas entered the tank, outside the bladder, rising pressure squeezed the bladder and forced the hazardous fuel from its tank. The flow of helium was tested during the integrated systems test. The primary and secondary regulators were checked to guarantee that an accurate flow was maintained, that the regulator shut off properly, and that after shutoff the pressure did not creep up, which would indicate internal leakage.
Problems with ground support equipment had put the launch team about two shifts behind schedule on 25 January when technicians completed the fuel-tank relief-valve checks and moved to the regulator tests. For these tests, the bladders were filled with helium gas instead of the hazardous monomethyl hydrazine. Human error brought the team grief: a technician failed to fully engage a quick-disconnect valve that controlled the flow of helium to a pressure regulator. Pressure inside a fuel tank, but outside the filled bladder, dropped quickly, and the bladder ruptured.23
The seriousness of the problem stemmed from its location. Replacement of the fuel tank involved removing the command module's aft heatshield, an operation that had to be conducted in the operations and checkout building. KSC faced a roll-back of the space vehicle from the pad to the assembly building - the first time this had happened since a hurricane threatened 500-F in June 1966. At first glance the accident seemed to preclude the April launch, and NASA officials announced a possible second month's delay; but after reviewing the work needed to replace the damaged fuel tank, Kapryan and Petrone concluded that the launch team could recover in time for the 16 April launch. The space vehicle was returned to the assembly building on 27 January. The following day the launch team transferred the spacecraft to the operations and checkout building where both fuel tanks were replaced, along with the descent propulsion system regulators. By working overtime and weekends,* KSC had Apollo 16 back on the pad in less than two weeks.24
While operations resumed their smooth course for most of the KSC team, the propellants section experienced more headaches. The spacecraft was undergoing another integrated systems test on 17 February when a leak developed in a quick-disconnect test point. A North American engineer closed off test points improperly and excessive pressure ruptured discs on both oxidizer tanks. While the launch team waited for replacements to arrive, the program office rescheduled the remaining propulsion tests. New burst discs were emplaced and x-rayed on the 22nd, and propulsion tests resumed the following day.25
* On 16 April 1972 the Washington Post noted that the damaged fuel tank had added an extra $200,000 to the cost of Apollo 16. Most of the money had gone for overtime pay at KSC.
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Stowing equipment on the Apollo spacecraft grew more complicated with the lunar exploration missions. The SIM bay and the rover have been described. The modularized equipment storage assembly occupied another quadrant of the descent stage. These cargo pallets provided room for tools, the lunar communications relay unit, various cameras including the color television equipment, and other items to be mounted aboard the rover. Inside the command and lunar modules the astronauts required more of nearly all supplies: food, clothing, film, and life support items. During the latter missions the Manned Spacecraft Center placed a number of experiments aboard the command module, e.g., Apollo 16 carried 60 million microbial passengers in a small rectangular container, a light flash detector, a biostack,* and a Skylab food package.26
70 mm camera adapter H2 gas separator in bag
5 tissue dispensers
2 penlights in bag tool set pressure garment 02 interconnect, 3 in bag snag line in bag
2 probe stowage straps
3 temporary stowage bags A3
4 C02 absorbers fire extinguisher acoustic tone booster in bag remote control cable
2-speed interval timer
5 sleep restraint ropes 16mm camera sextant adapter 3 headrest pads
TV monitor, monitor cable, and mounting bracket
2 C02 absorbers A8
3 pilot preference kits inflight exerciser
2 tissue dispensers
3 constant wear garments extravehicular mobility unit maintenance kits 3 light-weight headsets relief receptacle assembly and strap
16mm camera with magazine, powerpack, and 2 film magazines in bag 10mm lens decontamination bags 02 umbilical interconnect contingency lunar sample return container R3
data card kit eyepatch 2 meter covers floodlight glare shield fuse (16mm camera) 6 flight data file clips flight data file books lunar module transfer data card kit and flight data file books R4
2 sanitation stowage boxes 30 fecal collection assemblies water panel coupling assembly waste management system water panel, quick disconnect, power cable, and quick disconnect pressure cap R11
3 urine transfer systems spare urine receiver assembly roll-on cuff(red, white, blue) U4
4 cassettes, 4 batteries for tape recorders 10 x 40 monocular intervalometer (Hasselblad) 250mm lens
The launch team stowed the spacecraft cabins on three separate occasions during the Apollo 16 operations: first, in the chambers prior to the astronauts' altitude runs, a second time for the crew compartment fit and function test; and finally the day before launch. KSC had dropped the practice of stowing the cabin for the countdown demonstration test; instead technicians placed empty lockers inside the command module to give the astronauts the appearance of a flight-ready cabin. A team of nine normally stowed the command module. Inside the cabin two technicians secured each item in its proper place. A KSC quality control representative observed their work. Outside, two technicians unpacked the flight articles. A North American quality representative and engineers from Houston, KSC, and North American completed the team. While the six "outside members" of the team found the white room of the mobile service structure confining, they preferred it to the occasional use of the ninth swing arm from the umbilical tower, which had to be used in changing flight articles when Swigert replaced Mattingly on Apollo 13. Carrying equipment across a catwalk a hundred meters above the ground unnerved some members of the group. During the countdown, stowage of the command module began about 24 hours before launch and ran for seven hours. If no problems arose, the team could finish with several hours to spare.
The stowage exercise culminated two weeks of intensive preparations for KSC's Anne Montgomery. Her group checked many of the flight articles such as cameras, communications equipment, and the lithium hydroxide canisters. The items were tested individually and then in conjunction with other flight articles and command module systems. Some items required special packaging; all were weighed and recorded by serial number. Every flight article received a detailed quality inspection and each mission disclosed a number of discrepancies.
James McKnight directed a similar activity for the lunar module, the final stowage of which began just before the start of the formal countdown. At T-55 hours Grumman technicians placed most of the articles aboard and checked out the lunar equipment conveyor. The astronauts relied on this moving clothesline to carry heavy items such as rocks inside the lunar module. The group completed stowage at T-30 hours. After placing a portable life support system on the cabin wall and another on the floor, the technicians took pictures of their work and then sealed the hatch.
Houston prepared the stowage plans for each mission; these took into consideration when and where the astronauts would use a particular flight article. Emergency items received first consideration. The Manned Spacecraft Center was also responsible for the contents of the crew preference kits, the bags in which astronauts carried their personal mementos. Following the incident with unauthorized postal covers on Apollo 15, NASA tightened its restrictions on what the astronauts could take to the moon.27
After a successful flight readiness test on 1 March, officials met for the launch readiness review. The session covered all major aspects of Apollo 16 operations - range safety, operations safety, base support, Eastern Test Range support, Goddard's communications network support, the central instrumentation facility, technical support, and the status of the space vehicle. Despite the problem with the reaction control system fuel talk, Apollo 16 had been KSC's smoothest Apollo operation yet.28
One month before the scheduled liftoff, John Young, Apollo 16 commander, and Charles M. Duke, lunar module pilot, briefed KSC employees on the upcoming mission. Although 1,500 attended the meeting, the crowd appeared insignificant inside the assembly building. Young and Duke discussed the problems they anticipated on landing in the high, rugged Descartes region. They outlined the goals of their extravehicular activities and explained the flight plan. After answering questions from the audience, Command Module Pilot Thomas K. Mattingly and Young circulated through the crowd, shaking hands and signing autographs. The briefing was one of the astronauts' last public appearances before the launch, as they began their three-week preflight quarantine on 26 March. This crew had special reason to appreciate the restriction; Mattingly's potential measles on Apollo 13 had prompted the quarantine and in January 1972 Duke had spent a week at the Patrick Air Force Base hospital with bacterial pneumonia.29
The last month of operations saw few hardware changes. The actual countdown went without a hitch. Liftoff came on a hot Sunday afternoon, 16 April, at 12:54.30
* NASA measured the effects of reduced oxygen, zero gravity, and solar ultraviolet irradiation on the microbes representing five strains of bacteria, fungi, and viruses. On one flight experiment a crewman donned an emulsion plate device or deflector while his mates wore eye shields. The purpose was to correlate light flashes, seen on each mission since Apollo 11, to cosmic rays. The biostack, a cylindrical aluminum container 10cm. high, contained live biological material that was exposed to high-energy heavy ions in cosmic radiation. The Skylab food package included some experimental snap-top cans with dried peaches, puddings, peanuts, and other items.
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