PORTLAND, Ore. (KOIN) – On April 13, 1970 – 45 years ago – Apollo 13, four-fifths of the way to the moon, was crippled when a tank containing liquid oxygen burst.

“Houston, we have a problem,” Commander Jim Lovell said.

Apollo 13 was to be the third mission to land on the Moon. An explosion in one of the oxygen tanks crippled the spacecraft during flight and the crew – Lovell, Lunar Module Pilot Fred Haise and Command Module Pilot John Swigert Jr. – were forced to orbit the Moon and return to the Earth without landing.

The explosion happened 56 hours into the flight and 200,000 miles from Earth. Within minutes of the explosion the focus of the mission shifted from landing on the moon to getting the crew back to Earth safely.

When they landed safely on April 17, the mission was called NASA’s most successful failure.

NASA explained what happened:

After an intensive investigation, the Apollo 13 Accident Review Board identified the cause of the explosion. In 1965, the CM had undergone many improvements that included raising the permissible voltage to the heaters in the oxygen tanks from 28 to 65 volts DC. Unfortunately, the thermostatic switches on these heaters weren’t modified to suit the change. During one final test on the launch pad, the heaters were on for a long period of time. This subjected the wiring in the vicinity of the heaters to very high temperatures (1000 F), which have been subsequently shown to severely degrade teflon insulation. The thermostatic switches started to open while powered by 65 volts DC and were probably welded shut. Furthermore, other warning signs during testing went unheeded and the tank, damaged from eight hours of overheating, was a potential bomb the next time it was filled with oxygen. That bomb exploded on April 13, 1970 – 200,000 miles from Earth.