1970: Manned space flight has become so routine that it is easy to forget that it’s inherently dangerous to stuff astronauts inside a cramped capsule and blast them into the heavens on top of a Saturn V rocket. The Apollo 13 mission reminds us just how vulnerable we are.

Apollo 13, with astronauts James Lovell Jr., John Swigert Jr. and Fred Haise Jr. aboard, was on its way to the moon to perform the third lunar landing in a planned series of seven when, about 56 hours into the mission, an oxygen tank blew up, knocking out the command module’s electricity, light and water supply. “Hey, Houston, we’ve had a problem here,” Lovell told mission control, adding that some kind of gas was escaping outside the spacecraft. It was oxygen, and the mission quickly shifted from landing on the moon to getting the astronauts back alive. At the time, Apollo 13 was roughly 200,000 miles from Earth.

The crew moved into the lunar module to escape the decreasing air pressure in the service module, then prepared to make the necessary swing around the moon in order to boomerang back to Earth. Debris from the explosion had knocked out the navigation system, so the crew used the sun to guide the crippled craft home. It took nearly four agonizing days after the explosion before they splashed down safely in the Pacific Ocean.

(Source: NASA)

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