Apollo 13 lifted off on April 11, 1970. About 56 hours later, the pressure in an oxygen tank in the service module rose abnormally fast, and within about 100 seconds the tank abruptly lost pressure. The mission had to be aborted. The crew powered up the lunar module and used it as a lifeboat for the trip home.
That raised a problem with the air. The lunar module cleaned carbon dioxide out of the cabin with lithium hydroxide canisters. The two installed in its system had been designed, together, to handle two people for about 30 hours. What was needed was enough for three people for at least four days. The command module had plenty of canisters of its own. They wouldn’t fit the lunar module’s system.
Houston worked out a way to pull cabin air through a command module canister using only materials the crew had with them. According to the mission report, the setup “was assembled and tested on the ground” before the crew used it.
About 90 hours into the flight, Jack Swigert put on a headset. The capsule communicator, Joe Kerwin, started by asking whether anybody had told him he had a 60-day extension on his income tax. Then he read the procedure.
First, cut open the plastic bags that held a liquid-cooling garment. Then: “Now pick up one of the lithium hydroxide canisters, and let me describe which end is which.” The canister was “approximately square.” Wrap two belts of gray tape around it, sticky side out. Bend a cardboard cue card into an arch over the top, so the bag won’t be sucked onto the screens. Plug the hole in the bottom. Here Kerwin stopped himself: “I forgot to tell you to get something to stick in that hole.” The crew used a piece of towel. Slip the bag over the canister, tape it down, and push a suit hose through a slit in one corner.
Kerwin read a step. Swigert read it back. The crew did it, and reported. When Swigert asked whether a strip of tape went sticky side down, Kerwin answered, “Oh, that’s correct. I forgot to say that.”
Some 48 minutes after Kerwin began, Swigert called down: “Our do-it-yourself lithium hydroxide canister change is complete.” Kerwin: “I think it’ll work, too.” Then he asked for a second unit, built the same way.
The crew built two, attached to two suit hoses, and later stacked a second canister on each. In each case, the mission report says, the drop in carbon dioxide levels reported by the ground showed the improvised system was working. With only command module canisters in use, the indicated carbon dioxide level stayed between 0.1 and 1.8 millimeters of mercury.