Using the lunar module as a "lifeboat."
But about 56 hours into the mission something went terribly wrong.
"Okay, Houston, we've had a problem here," commander module pilot Jack Swigert said to mission control.
"This is Houston. Say again please."
Commander Jim Lovell repeated: "Houston, we've had a problem. We've had a main B bus undervolt."
A real conversation from the
The transcript will give you chills.
Within three hours of the malfunction, the astronauts lost the ability to generate water and power. They also lost their oxygen stores.
Meanwhile, back in Houston, mission control was working frantically to get their men quickly and safely back to Earth.
NASA
The makeshift filter system that ultimately saved the astronauts' lives.
But because the module was only built for two people, and there were three astronauts, the canisters used to absorb the gas from the air were quickly used up, leading to a potentially lethal build-up of carbon dioxide.
The crew could use the canisters from the command module, but there was one problem: The command module used square canisters, while the lunar module used round ones.
Using only the materials on the craft, NASA engineers had to find a way to shove a square shape in a round hole.
This lead to one of the more remarkable feats during the rescue effort.
According to NASA, "following instructions from mission control, it took the astronauts about 1 hour to build the device out of plastic bags, cardboard, parts from a lunar suit and a lot of tape."
It worked!
This was just one of the many challenges NASA faced during an intense four days.
But all ended well.
The crew splashed down into the South Pacific on April 17, 1970.
They had missed the moon, but the mission was classified as a "successful failure" because the three astronauts safely returned to Earth.
Below is the full transcript, recording the events up to about 5 minutes after the accident.
(Times are given are in Ground Elapsed Time (G.E.T.), or the time elapsed since liftoff of
55:55:20 — Swigert: "Okay, Houston, we've had a problem here."
55:55:28 — Lousma: "This is Houston. Say again please."
55:55:35 — Lovell: "Houston, we've had a problem. We've had a main B bus undervolt."
55:55:42 — Lousma: "Roger. Main B undervolt."
55:55:49 — Oxygen tank No. 2 temperature begins steady drop lasting 59 seconds indicating a failed sensor.
55:56:10 — Haise: "Okay. Right now, Houston, the voltage is — is looking good. And we had a pretty large bang associated with the caution and warning there. And as I recall, main B was the one that had an amp spike on it once before.
55:56:30 — Lousma: "Roger, Fred."
55:56:38 — Oxygen tank No. 2 quantity becomes erratic for 69 seconds before assuming an off-scale low state, indicating a failed sensor.
55:56:54 — Haise: "In the interim here, we're starting to go ahead and button up the tunnel again."
55:57:04 — Haise: "That jolt must have rocked the sensor on — see now — oxygen quantity 2. It was oscillating down around 20 to 60 percent. Now it's full-scale high."
55:57:39 — Master caution and warning triggered by DC main bus B undervoltage. Alarm is turned off in 6 seconds.
55:57:40 — DC main bus B drops below 26.25 volts and continues to fall rapidly.
55:57:44 — Lovell: "Okay. And we're looking at our service module RCS helium 1. We have -- B is barber poled and D is barber poled, helium 2, D is barber pole, and secondary propellants, I have A and C barber pole." AC bus fails within 2 seconds.
55:57:45 — Fuel cell 3 fails.
55:57:59 — Fuel cell current begins to decrease.
55:58:02 — Master caution and warning caused by AC bus 2 being reset.
55:58:06 — Master caution and warning triggered by DC main bus undervoltage.
55:58:07 — DC main bus A drops below 26.25 volts and in the next few seconds levels off at 25.5 volts.
55:58:07 — Haise: "AC 2 is showing zip."
55:58:25 — Haise: "Yes, we got a main bus A undervolt now, too, showing. It's reading about 25 and a half. Main B is reading zip right now."
56:00:06 — Master caution and warning triggered by high hydrogen flow rate to fuel cell 2.