Apollo 13: The Tank Flaw and Crew’s Lifeboat Return

Apollo 13 lifted off from Kennedy Space Center on April 11, 1970, with Jim Lovell, Fred Haise and Jack Swigert aboard. Two days later, about 200,000 miles from Earth, an oxygen tank exploded, and the crew spent four days getting home in a lunar module built to keep two men alive for about two days. All three returned and the Odyssey splashed down in the South Pacific.

A crew changed three days before launch

Apollo 13 was meant to be the third Moon landing, at a hilly region called Fra Mauro. Commander Jim Lovell, 42, was on his fourth spaceflight and had already flown around the Moon on Apollo 8. Fred Haise was the lunar module pilot. Ken Mattingly was to be command module pilot, but a backup astronaut developed German measles, Mattingly had been exposed without having had the disease, and flight surgeons grounded him. Jack Swigert got the job three days before launch. Mattingly never fell ill.

At launch, five and a half minutes in, the center engine of the second stage shut down two minutes early. The other four engines burned longer to make up for it, and the crew reached orbit and headed for the Moon.

The flaw in oxygen tank 2

Two tanks of super cold liquid oxygen sat in the service module. They supplied air to breathe and fed the fuel cells that made electricity and water. Tank 2 had a history: in 1968, at the factory, the shelf holding it was dropped about 2 inches. In March 1970, during a ground test at Kennedy, the tank would not empty properly, so technicians switched on its internal heaters to boil the oxygen off.

Those heaters had safety switches built for 28 volts, but the ground equipment ran at 65. The switches welded shut, the heaters ran for hours, and the temperature inside may have reached 1,000° F. The gauge read only up to 85, so nobody saw it. The wires inside were cooked bare, and the tank was loaded onto Apollo 13.

The explosion

At 55 hours the crew gave a live TV tour of both spacecraft, which none of the big networks carried. Houston then asked for a routine chore: stir the oxygen tanks. At 9:08 p.m. Houston time Swigert flipped the switch, the bare wires sparked, and the tank exploded. Swigert reported: "Okay, Houston, we've had a problem here." Controllers first suspected a bad sensor, until Lovell saw something venting into space. It was oxygen. Tank 2 was gone, tank 1 was leaking, and two of the three fuel cells were dead.

Aquarius as a lifeboat

Flight director Gene Kranz told his team to keep cool and not make things worse by guessing. The command module Odyssey had to be shut down completely to save its batteries for re-entry. Haise and Lovell powered up the lunar module Aquarius. Because the craft had left its free return path, the crew fired the lander's descent engine in a 30-second burn to get back on course.

On April 14 the spacecraft passed behind the far side of the Moon, out of radio contact, 248,655 miles from Earth, farther than any human had been. Two hours after closest approach Houston ordered a second burn of more than 4 minutes, which cut about 12 hours off the trip and moved splashdown from the Indian Ocean to the Pacific.

Air, cold and a manual burn

Aquarius scrubbed carbon dioxide with lithium hydroxide canisters, but carried enough for two men for two days. Odyssey's spare canisters were square, and Aquarius took round ones. Engineers on the ground devised a fix from plastic flight-manual covers, space suit hoses, cardboard and duct tape, called the mailbox. Astronaut Joe Kerwin read the instructions up for about an hour, Swigert and Haise built it, and carbon dioxide levels began to fall.

With nearly everything off to save power, the cabin dropped to about 38° Fahrenheit and water beaded on the walls. Water was rationed to about 6 ounces per man per day. Haise developed a urinary infection and a fever. Together the three lost 31 pounds.

The crew drifted off course with the guidance computer shut down, so Lovell lined up the line between day and night on Earth in his window, and Swigert timed a 14-second burn that put them back on track. Meanwhile Mattingly helped engineers in simulators work out how to revive the dead Odyssey.

Re-entry

On April 17 the crew released the service module and saw that an entire panel was blown off, with Odyssey's heat shield having sat right against it. Odyssey powered up. About an hour before re-entry they cast off Aquarius, and Mission Control radioed, "Farewell, Aquarius, and we thank you."