When Apollo 13 astronaut Fred Haise drifted into the tunnel between the lunar module and the command module, he heard and felt a loud bang. Around him, the two vehicles began to twist. Then the metal walls of the tunnel wrinkled as the spacecraft shuddered.
Wide-eyed, Haise clambered out of the tunnel into the command module alongside Jack Swigert and their commander, Jim Lovell. From his usual position to Lovell’s right, Haise quickly determined that something was drastically wrong with the spacecraft’s cryogenic tanks — the oxygen was just away† Fortunately, there appeared to have been no chemical explosion, as only a thin wall separated the oxygen tank from the propellant tanks used to power the spacecraft’s main engine.
“It really didn’t explode the way you think with shrapnel,” Haise told Ars in an interview. “It just came under pressure, and then it let out some steam. If it had been a shrapnel-type explosion, I wouldn’t be here today.”
The incident occurred on April 13, 1970, towards the end of the second full day of the Apollo 13 flight. The crew aboard NASA’s third mission to the moon’s surface had just completed a live television broadcast. They were tired but also excited. They would soon go to bed, and when they woke up, the spacecraft would go into orbit around the moon. In about a day, Lovell and Haise would become just the fifth and sixth people to walk on the surface of another world.
But now, sitting in the Command Module odysseyWhile contemplating the loss of an oxygen tank, Haise’s first thought was not that Apollo 13 would be in danger of returning home. In the immediate aftermath of the accident, death didn’t seem so close. Haise previously lamented the missed opportunity to set foot on the moon.
“I was just nauseous with disappointment,” Haise recalls. “I knew we had an abortion, and I had lost the landing. That was my main feeling. We thought we had a second tank that was intact.”
But the damage was so extensive that the second tank was also hit. It may have been leaking oxygen more slowly, but the leak had started anyway. Soon, the spacecraft would lose both of its oxygen tanks. It didn’t matter much for oxygen in the Command Module, the astronauts had enough to breathe. But without the oxygen tanks, the spacecraft wouldn’t be able to run its fuel cells. The crew of Apollo 13 would have no power. They faced the prospect of freezing to death in space.
When the astronauts and flight controllers in Mission Control realized they couldn’t stop the leak in the second oxygen tank, the mission suddenly changed. Apollo 13 would no longer want to land on the moon. Their mission had become one of survival.
“So many opportunities”
Even before the Apollo 13 accident, some senior NASA executives had wondered how long they would get away with the serious risks associated with traveling to the moon. Considering all the different aspects of a lunar flight—from the Saturn V launch vehicle to the command and service modules, and finally the lunar modules—a lot of very complicated components had to work just right for a mission to be successful.
At the start of the program, NASA had formally set the target probability of overall success for any Apollo mission — a landing and reentry — at 90 percent. The overall safety of the crew was estimated at 99.9 percent. But a 1965 assessment of these risks had found that, based on current plans and technology, the probability of mission success for any flight was only about 73 percent, while the estimated crew safety was 96 percent.
Few people lived with these risks and worries from day to day more than Robert Gilruth. His fame may have waned over the decades, but Gilruth was above all others in America’s efforts to send humans to the moon and back. After the creation of NASA, the fledgling agency had turned to Gilruth to lead the Space Task Group to send a human into space before the Soviet Union. Later, after President John F. Kennedy called for moon landings, that task fell to the Manned Spacecraft Center in Houston, which was headed by Gilruth.
Gilruth, a small-town aeronautical engineer in Minnesota, had a more pragmatic view of human spaceflight than Kennedy’s grandiose vision. As he saw it, after NASA successfully put astronauts into orbit with the Mercury program, the next logical step toward a permanent presence in space would have been to build a space station there.
“But that didn’t have the flair it needed at the time, in the eyes of Mr. Kennedy,” Gilruth, who died in 2000, recalled in an oral history. “He thought going to the moon was about as good as you could possibly do. I think LBJ liked that too. No one at NASA would say they couldn’t. At least I said, ‘I’m not sure we can do it, but I’m not sure we can’t.’”
Gilruth was under no illusions about the challenge of reaching the moon. Moreover, when Neil Armstrong and Buzz Aldrin stepped on the moon in front of a worldwide television audience, NASA had reached Kennedy’s mandate. If every mission had a quarter chance of not landing on the moon and a non-negligible chance of losing a crew, why put up with it? That feeling only grew within Gilruth as NASA did more moon landings.
“I straightened up and said, ‘We have to stop,'” Gilruth said. “There are so many opportunities for us to lose a crew. We just know we’re going to do that if we keep going.”