Apollo 13 Launch Operations
After four days of hypergolic load tests in mid-March, the launch team began the countdown demonstration test on the 18th.
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.
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.