APOLLO 13: Okay, Houston, we’ve had a problem here. CAPCOM: This is Houston, say again, please. 13: Houston, we’ve had a problem.

Perhaps no line in the history of the space program is better known than that one. Fifty years ago today, while more than halfway to the Moon, the crew of Apollo 13 — Jim Lovell, Fred Haise, and Jack Swigert — was in big trouble.

LOVELL: It looks to me, looking out the hatch, that we are venting something. We are venting something out into space.

An oxygen tank had exploded, damaging other systems and shutting down the mothership’s fuel cells. Without them it had no power — and no way to keep the crew alive. Flight director Gene Kranz prepped his team in Mission Control for the challenge:

KRANZ: Okay, now, let’s everybody keep cool. We got the LM still attached, the LM spacecraft’s good, so if we need to get back home we’ve got a LM to do a good portion of it with. So let’s solve the problem, but let’s not make it any worse by guessing.

Within an hour of the explosion, the astronauts were prepping their lunar lander, Aquarius, to serve as a lifeboat. They fired its main engine to put them on a path that would take them behind the Moon, then straight back to Earth. Over the following three and a half days, they relied on its power and engines to keep them alive and on course. And they relied on hundreds of engineers and technicians on the ground to solve problems and work out procedures.

The astronauts were cold, thirsty, and miserable for much of the journey, but they made it home — surviving a famous problem in space.

Script by Damond Benningfield