Apollo 13 launched from Cape Canaveral on April 11, intended to be the third manned lunar landing. The crew — James A. Lovell Jr., John L. Swigert Jr. and Fred W. Haise Jr. — experienced a slight vibration shortly after launch, but things were going normally until 55 hours, 55 minutes into the flight.
Oxygen tank No. 2 exploded, causing No. 1 to fail and start leaking rapidly. Warning lights started blinking. The astronaut's supplies of air, water, light and electricity were imperiled ... 200,000 miles from Earth.
They didn’t land on the moon as planned, but just making it home alive was an amazing accomplishment. The film Apollo 13 (based on astronaut James Lovell’s book Lost Moon) recounted the story of their close call and McGyver-like operations. Wired has more details. Link