Apollo 13 launched into space on April 11, 1970 on a nearly six-day mission that some mission leaders would later describe as a "successful failure." Although NASA lost three astronauts during a ground-based training mission for Apollo 1, this was the first time the space agency came close to losing a crew in space.
Apollo 13 was designed to ferry the third crew to walk on the Moon. On April 13, two days after launch, an oxygen tank aboard the spacecraft exploded. At the time of the incident, the three-man crew were 200,000 miles from Earth, well on their way to our lone natural satellite.