Apollo 13: How Mission Control and Three Astronauts Got Home

Apollo 13 is the space mission people love even though it never reached its goal. NASA's own pages describe it as a "successful failure," and once you see how many problems had to be solved, fast, with whatever was on board, the nickname makes sense. Here's the story, drawn from NASA's own history pages.

The plan

On April 11, 1970, a Saturn V launched from Kennedy Space Center carrying Commander Jim Lovell, Command Module Pilot Jack Swigert and Lunar Module Pilot Fred Haise. It was meant to be humanity's third Moon landing, in the Fra Mauro highlands. Lovell and Haise were to spend 33 hours on the surface and make two moonwalks while Swigert worked from lunar orbit.

The two spacecraft had names. The command module, home for most of the trip, was Odyssey. The lunar module, the lander, was Aquarius. Remember Aquarius: it becomes the hero.

Trouble before the trouble

A few odd things happened before the big one:

• Days before launch, backup lunar module pilot Charlie Duke accidentally exposed the crew to German measles. Original command module pilot Ken Mattingly had no immunity, so backup Jack Swigert took his seat.
• About five and a half minutes after liftoff, the center engine of the rocket's second stage shut down two minutes early. The other engines burned longer to make up for it.

After that, things went smoothly. At 46 hours and 43 minutes, capcom Joe Kerwin told the crew, "We're bored to tears down here." NASA's mission summary notes it was the last time anyone mentioned boredom for a long while.

The bang

On the third day, about 205,000 miles from Earth, the crew wrapped up a TV broadcast and did a routine chore: stirring the super-cold oxygen and hydrogen tanks in the service module. At 55 hours, 55 minutes and 4 seconds into the flight they heard a dull bang. Warning lights came on, and Swigert called down: "Okay, Houston, we've had a problem here." Lovell repeated it and reported a Main B Bus Undervolt, a drop in electrical power.

At first everyone hoped it was a sensor glitch. Then two of the three fuel cells, the main power source, went offline, and oxygen readings started falling. About 14 minutes in, Lovell looked out a window and reported that they were venting a gas into space. It was their oxygen.

Flight Director Gene Kranz told his team to keep cool, noted they still had a healthy lunar module attached, and summed it up: "Let's solve the problem but let's not make it any worse by guessing."

Turning the lander into a lifeboat

The Moon landing was off, and the goal became getting the crew home. Odyssey had only about 15 minutes of power left by the time the crew moved into Aquarius. Haise powered up the lander while Swigert shut the command module down, saving its batteries for re-entry.

Aquarius wasn't built for this. It was designed to support two people for about two days, and now it had to keep three alive for about four. NASA's mission summary says its 45-hour lifetime had to stretch to 90. Ground controllers cut power use to about a fifth of normal.

Navigating home with the wrong engine

The service module's big engine couldn't be used, so Mission Control used the lander's descent engine, the one meant to set Aquarius down on the Moon. Luckily engineers had already drawn up contingency plans for exactly that.

• About five and a half hours after the accident, a 34-second burn put them back on a free-return path around the Moon. (NASA's mission summary rounds it to 35 seconds.)
• Debris from the explosion surrounded the spacecraft, making it impossible to sight stars to check their alignment. So the crew used the Sun, which was off by less than half a degree.
• Two hours after swinging around the Moon, a 4-minute, 24-second burn sped them up, bringing them home about 10 hours earlier and steering the landing into the Pacific.

While behind the Moon, Lovell, Swigert and Haise reached 248,655 miles from Earth, the record for the farthest humans had ever traveled. It stood for 56 years, until NASA's Artemis II crew passed it on April 6, 2026, during their own trip around the Moon. When the crew learned their spent rocket stage had hit the Moon as planned, Lovell said, "Well, at least something worked on this flight."

The square peg in the round hole

Next crisis: carbon dioxide. There were enough lithium hydroxide canisters on board to scrub the CO2 the crew breathed out, but the command module's canisters were square and the lander's system took round ones. After a day and a half in the lander, a warning light showed CO2 building to a dangerous level.

On the ground, a team led by Ed Smylie, with James Correale and Jim LeBlanc, built a fix using only copies of items aboard: a spacesuit hose, plastic bags, a cue card from the flight plan and duct tape. They tested it in an altitude chamber, and the procedure was read up to the crew. Swigert and Lovell built two of the contraptions, and CO2 levels dropped significantly within minutes.

Cold, thirsty and stubborn

With most systems switched off, the cabin got very cold. NASA reports temperatures as low as 38 degrees Fahrenheit, and Lovell and Haise wore their lunar overshoes to keep their feet warm. Water was the biggest worry, so the crew cut down to about six ounces each per day. Lovell lost 14 pounds, and the crew lost 31.5 pounds together, a record for the Apollo program. Haise also developed a urinary tract infection, likely from dehydration.

Power took clever engineering too. NASA credits Arturo Campos, the lunar module's electrical power subsystem manager, with helping adapt an untested contingency plan for sending power from the lander to the command module. Later, the crew spent about 15 hours recharging two of Odyssey's batteries from Aquarius, a procedure that had never been done before.

Waking Odyssey up

Restarting a cold, damp command module was a big unknown. Flight controllers wrote the power-up procedures in three days instead of the usual three months, and Ken Mattingly, the grounded crew member, spent hours in the simulator finalizing them. Moisture covered the cabin walls and panels, but no arcing took place. Lovell later recalled that during re-entry, "it rained inside the CM."

Near the end, the crew released the damaged service module and got their first look at it. One whole panel was gone. Then they let go of Aquarius, prompting capcom Joe Kerwin's farewell: "Farewell, Aquarius, and we thank you."

On April 17, 1970, Odyssey splashed down in the Pacific after a flight of 142 hours, 54 minutes and 41 seconds, about a mile from its target and four miles from the recovery ship USS Iwo Jima.

What went wrong, in one paragraph

NASA's investigation traced the explosion to oxygen tank No. 2. The tank had originally been installed in Apollo 10's service module, then removed for modification and damaged in the process. During testing before launch it wouldn't empty properly, so technicians used its internal heater to boil off the oxygen, running for eight hours on 65-volt power. Back in 1965, the permitted heater voltage had been raised from 28 to 65 volts, but the heater's thermostatic switches weren't upgraded to match. The switches probably welded shut, the wiring overheated, and its Teflon insulation was damaged, leaving a tank that NASA describes as a potential bomb the next time it was filled.

Why it still grabs people

The explosion itself was over in seconds. The rescue took four days of nonstop problem-solving by three tired astronauts and teams of flight controllers working around the clock in Houston. That's why NASA calls it a successful failure: the mission lost the Moon and brought everyone home.

One fun footnote from NASA: in Ron Howard's film Apollo 13, the real Jim Lovell makes a brief cameo as the captain of the recovery ship.