It's the handy man's secret weapon, and has become a must-have item for astronauts, too. While duct tape alone didn't save the Apollo 13 crew, it certainly would have been difficult for them to have survived without it. Even though the accident which crippled the ship took out the two main oxygen tanks in the Service Module, having enough oxygen really wasn't an issue for the crew. A big problem was having too much carbon dioxide (CO2), which came from the astronauts' own exhalations. The Lunar Module had lithium hydroxide canisters to remove the CO2 for two men for two days, but on board were three men trying to survive in this LM lifeboat for four days. However, with a little ingenuity and duct tape, the Apollo Mission Operations Team was able to fit "a square peg in a round hole."