Apollo 13 was the third Apollo mission intended to land on the Moon. A mid-mission incident occurred when an oxygen tank rupture severely damaged the spacecraft and forced the lunar landing to be aborted. The flight was commanded by James A. Lovell; with John L. "Jack" Swigert, Command Module pilot; and Fred W. Haise, Lunar Module pilot. Swigert was a late replacement for the original CM pilot Ken Mattingly, who was grounded by the flight surgeon after exposure to German measles.
The mission was launched on April 11, 1970 at 13:13 CST. Two days later, en route to the Moon, a fault in electrical equipment inside one of the Service Module's oxygen tanks produced an explosion which caused the loss of both tanks' oxygen, depriving the Service Module of electrical power. This forced the crew to shut down the Command Module to conserve its batteries and oxygen needed for the last hours of flight, and use the Lunar Module's resources as a "lifeboat" during the return trip to Earth. Despite great hardship caused by limited power, loss of cabin heat, shortage of potable water, and the critical need to jury-rig the carbon dioxide removal system, the crew returned safely to Earth on April 17, and the mission was termed a "successful failure".