On April 11, 1970, NASA launched Apollo 13, its third attempt to land astronauts on the Moon. The planned mission took an unexpected turn when an oxygen tank failed in deep space. Commander Jim Lovell, command module pilot Jack Swigert and lunar module pilot Fred Haise spent the next four days trying to survive long enough to return to Earth.
The story is often summarized by a famous radio message. But the engineering behind the rescue is even more remarkable: a damaged service module, a lunar lander used as a lifeboat, an improvised carbon dioxide filter and a complex return trajectory around the Moon.
Who flew aboard Apollo 13?
Apollo 13 launched from Kennedy Space Center aboard a Saturn V rocket on April 11, 1970. Its crew consisted of Jim Lovell, Jack Swigert and Fred Haise. Swigert had replaced Ken Mattingly before launch after concern about exposure to German measles.
The spacecraft included the command module Odyssey, the service module with major power and life-support systems, and the lunar module Aquarius, which was originally designed to carry two astronauts to the Moon's surface.
What happened to the oxygen tank?
About 55 hours and 55 minutes into the mission, an electrical failure in oxygen tank number two caused a rupture. The failure damaged the service module and compromised the oxygen supply needed by its fuel cells. Electrical power began falling, and Mission Control abandoned the planned Moon landing.
The later Apollo 13 Review Board connected the failure to damaged wiring insulation, component design and earlier ground operations. The disaster was not a meteor strike or a malfunctioning computer.
How did the astronauts survive?
Mission Control instructed the astronauts to move into the lunar module Aquarius. This vehicle was designed for two crew members, not three people on a multi-day emergency return. Nevertheless, it provided the oxygen, batteries and propulsion needed to serve as a temporary lifeboat.
The crew shut down Odyssey to preserve its remaining electricity for reentry. They faced extreme cold, limited water, short sleep and a shrinking supply of electrical energy.
What was the Apollo 13 mailbox?
Carbon dioxide built up as the three astronauts exhaled inside the lunar module. The command module had spare lithium hydroxide scrubber canisters, but those were rectangular, while the lunar module's filter fittings were round.
Engineers devised an adapter using available spacecraft materials, including cardboard, plastic and tape, so the different systems could work together. The improvised system is commonly called the mailbox. It allowed the crew to reduce dangerous carbon dioxide levels.
Why did Apollo 13 fly around the Moon?
A free-return trajectory uses lunar gravity to bend a spacecraft's path back toward Earth. Apollo 13 was placed on a suitable return course using the lunar module's descent engine. Mission Control and the crew then performed correction burns to improve the approach and conserve limited resources.
The crew passed around the far side of the Moon, but never landed on it.
How did the rescue end?
As Apollo 13 returned toward Earth, the crew separated the damaged service module and observed its missing outer panel. They later transferred back to Odyssey and jettisoned Aquarius.
On April 17, 1970, Odyssey reentered Earth's atmosphere. After the expected radio blackout, communications returned and the capsule splashed down in the Pacific Ocean. All three astronauts survived.
What did Apollo 13 change at NASA?
NASA investigated the oxygen tank failure and introduced changes to spacecraft oxygen systems, monitoring and emergency procedures. Apollo 13's technical mission failed, but its rescue demonstrated the importance of engineering, teamwork, contingency planning and calm decisions under pressure.
Frequently asked questions
Did Apollo 13 land on the Moon? No. The landing was canceled after the oxygen tank explosion. The spacecraft went around the Moon and returned to Earth.
Who were the astronauts aboard? Jim Lovell, Jack Swigert and Fred Haise.
What day did Apollo 13 return? April 17, 1970.
What saved Apollo 13? There was no single fix. Survival depended on converting Aquarius into a lifeboat, conserving power, navigating a return path, controlling carbon dioxide and restarting Odyssey for reentry.
Historical sources
- NASA Apollo 13 mission overview: https://www.nasa.gov/mission/apollo-13/
- NASA History, Apollo 13: https://www.nasa.gov/history/apollo-13/
- NASA Apollo 13 Review Board Report (NTRS): https://ntrs.nasa.gov/citations/19700078959
- NASA Image and Video Library: https://images.nasa.gov/
This feature uses archival photographs and original educational diagrams. The historical film and images are attributed in the companion video description.
