The launch vehicle and spacecraft for the Apollo 13 mission arrived at KSC in June 1969. Following the Apollo 11 success, NASA set a March 1970 launch date for Apollo 13. More planning time was added in January, moving the launch to 11 April. Prelaunch operations went smoothly through the fall and winter months. The work in high bay 1 marked its last use for Apollo; subsequently the area would be used for Skylab operations. The Bendix crawler team transferred the space vehicle to pad A on 15 December. The flight readiness test, scheduled before the January program change, was run on 29 January as a "confidence test" and rerun on 26 February. After four days of hypergolic load tests in mid-March, the launch team began the countdown demonstration test on the 18th.22
A strange accident punctuated the last day of the test. Early on 25 March, Graydon Corn's propellants crew started the chill-down of the LOX pumping system. The operation required a 760-liter-per-minute flow to the replenishing pumps (which could handle five times that rate) and a lesser amount through a bleed line that had been added to the LOX system after the 500-F spill in August 1966. [see chapter 15-9] During the 40 minutes of precooling, the launch team emptied 39,000 liters of LOX into a drainage ditch outside the perimeter fence. Normally ocean breezes dissipated the oxygen fog. On the morning of the 25th, however, there was no wind and a pronounced temperature inversion. A dense fog built up in the drainage ditch; at a culvert where the road to the slide wire bunker crossed the ditch, the invisible oxygen overflowed onto the bank. At 6:00 a.m. the closeout crew and safety personnel left the LOX storage area. First-stage loading could begin after a three-minute chill-down of the 38,000-liter-per-minute main pumps. A security team completed its job of clearing the pad area and proceeded in three cars to the perimeter gate southwest of the LOX sphere. The driver of the first car, Patrolman Nolan Watson, drove through the gate and parked. As he walked back to Earl Paige's car, an order over the radio directed the team to clear the slide wire bunker area. Paige turned his ignition on and heard a loud pop. Soon flames sprang up from beneath the hood. Watson ran back to his car, only to find it also on fire. About the same time, the third car burst into flames. The three guards quickly ran for cover. A fire and rescue crew arrived in five minutes but took no action until the oxygen cloud dissipated. It was nearly 7:00 a.m. before the fire was under control, leaving three burnt hulks and a shaken crew.
Debus called for an immediate investigation. The preliminary report, rendered a week later, blamed the accident on the enriched oxygen atmosphere. Spontaneous ignition resulting from the engine heat, combustibles (oil and grease on the engine covers and gas around the carburetors) and the oxygen vapor cloud caused two of the fires, the third apparently starting when the driver turned the ignition switch. The report criticized the practice of dumping large quantities of cryogenics and termed the resulting vapor a hazard. Recommendations included immediate studies of the drainage system leading from the LOX storage area and its dump reservoir, of entry and exit routes at pad 39 A, and of KSC's safety training course. The major change brought about by the accident was to extend the LOX drainage pipes beyond the perimeter ditch to a marshy area farther from the pad.23
Another anomaly during the demonstration test appeared insignificant at the time; in fact, it was the beginning of what was to prove Apollo's most nerve-wracking hours. On 24 March the North American launch crew finished loading the cryogenics into the service module. Tank testing had gone smoothly and nothing about the loading operation presaged troubles ahead. The first sign came when the launch crew partially emptied the two liquid oxygen tanks. While the first tank performed normally, emptying half of its contents, the second tank released only 8% of its LOX. The crew prepared an interim discrepancy report and postponed further action until the end of the demonstration test.
The spacecraft team resumed detanking operations on the 27th, after discussing the matter with Houston, Downey, and Beech Aircraft Corporation. The problem centered on a possible leak between the fill line and the quantity probe because of a loose fit in the sleeves and tube. A second failure of the detanking procedure strengthened this view. After additional attempts at higher pressures proved unsuccessful, the KSC team decided to "boil off" the remaining LOX. The tank heaters, energized by 65 volts of direct current, were turned on; 90 minutes later the tank fans were also activated. The solution proved to be a slow one. After 6 hours the quantity of LOX in the tank still stood at 35%. The team continued to run the heaters and began pressurizing the tank for a few minutes and then venting the fill line. After two more hours of alternately heating and venting, the tank emptied.
Apollo officials faced a difficult decision. Replacement of the oxygen shelf in the service module would take two days and posed the possibility of damaging other equipment. If the problem were a loose fill tube, the shortcoming would not threaten the mission. The LOX tank would still supply the fuel cells properly and any electrical short at the capacitance gauge would be insignificant. After further discussions with Washington, Houston, and Downey, KSC undertook a partial fill on the 30th. Both tanks reached the 20% level without any trouble, but emptying the second tank again required heating and pressure cycling. Apollo technical and management personnel weighed the possible hazards of flying with a loose fill tube against the problems of shelf replacement. The decision was to keep the defective tank.24
A second cryogenic tank problem received more publicity in the closing days of the prelaunch operations. Liquid helium from a tank in the lunar module was used to assure a steady flow of propellants to the descent engine. The tank's design allowed for a slow increase of pressure as the helium warmed, but during the countdown demonstration, pressure in the tank began rising too fast. If a faulty vacuum allowed heat to build up too rapidly, the increased pressure would blow the tank's burst disk and prevent a lunar landing. Over the first weekend in April, newspapers reported the helium tank as a serious problem. A test conducted on Monday the 6th, however, indicated that the "heat rate loss was well within parameters and acceptable for launch."25
Apollo operations continued to attract famous people from around the world. In early March, French President and Mme. Pompidou spent a day at the center. The following week, 50 members of the U.S. Congress and the Canadian Parliament got a close view of Apollo 13; 60 German and Japanese astronomers visited Merritt Island on 9 March, after viewing a solar eclipse in north Florida. Later that month the British astronomer, Sir Bernard Lovell, and his wife were guests. The VIP list for the 11 April launch included Willy Brandt, Chancellor of West Germany, Vice President Agnew, and Secretary of State William Rogers.26