In April 1970, Apollo 13 was supposed to be the third mission to land people on the Moon. Two days in, the astronauts heard what one later called a "pretty large bang." Moments later came words that became famous: "Houston, we've had a problem."
The short answer to how they survived: the crew climbed into their lunar lander and used it as a lifeboat. They looped around the Moon and headed home, while engineers on the ground invented fixes on the fly. After four tense days, they splashed down safely in the South Pacific on April 17, 1970.
What Went Wrong
The crew was commander Jim Lovell, command module pilot Jack Swigert, and lunar module pilot Fred Haise. Swigert was a last-minute replacement after Ken Mattingly was grounded for exposure to German measles.
A routine stir of an oxygen tank in the service module sparked damaged wire insulation inside it. The explosion that followed vented the contents of both oxygen tanks into space. That oxygen was needed for breathing and for making electricity. The main spacecraft was crippled, and its command module had to be shut down to save its batteries for the final return to Earth.
A Lifeboat Built for Two
Luckily, the lunar module, nicknamed Aquarius, was still attached, with charged batteries and full oxygen tanks. It was designed to support two men on the Moon for two days. Mission Control in Houston worked out new procedures to stretch it to three men for four days.
Timing mattered enormously. If the explosion had happened on the way home, after the lander had been cast off, or while two astronauts were walking on the Moon, the crew would have died.
Rather than turn around, they swung around the far side of the Moon and fired the lander's engine to speed the trip home. On April 14, at their farthest point, they were about 248,655 miles from Earth. That set a record for the farthest humans have traveled from our planet, a record that stood until Artemis II's lunar flyby in 2026.
The Famous "Mailbox" Fix
Oxygen wasn't the only worry. The crew also needed to remove the carbon dioxide they exhaled, which was absorbed by canisters inside the spacecraft. The lander didn't have enough canisters for three people, and the command module's spares were a different shape and wouldn't fit.
Engineers on the ground came up with a solution using plastic covers ripped from procedure manuals, duct tape, and other items on board. They called it "the mailbox." Over about an hour, the instructions were read up to the crew, and Swigert and Haise built it. Carbon dioxide levels began dropping immediately.
Cold, Thirsty, and Tired
To save power, the cabin stayed dark, and the temperature dropped as low as 38°F. Water condensed on the walls, and drinking water was short. Swigert had gotten his feet wet and had no Moon boots, since he wasn't scheduled to walk on the Moon. Despite it all, the crew made few complaints.
Reentry brought one last scare. The usual radio blackout lasted six minutes instead of four, and controllers feared the heat shield had failed. Then the capsule, named Odyssey, called in and splashed down about four miles from the recovery ship, USS Iwo Jima. Tens of millions watched on television.
Lovell later called the mission a "successful failure." It never reached the Moon, but it showed what calm thinking and teamwork can do. Many still call it NASA's finest hour, and it's easy to see why.
