Highest altitude reached by humans

The highest altitude reached by humans is 400,041 km (248,573 mi), achieved by American astronauts James Lovell, Fred Haise and John Swigert in the severely damaged Apollo 13 spacecraft. The record-breaking flight was made between 11 and 17 April 1970 from the Kennedy Space Center in Florida, USA, and reached its farthest point from Earth at 00:33 UTC on 15 April, during their free-return loop around the far side of the Moon.

Apollo 13 was planned as a "Type H" mission (like Apollo 12 and Apollo 14). While Apollo 11 (the "Type G" mission) had very limited objectives aside from landing safely and returning to Earth, the "Type H" missions were to land at specific, precisely defined locations and conduct extensive scientific fieldwork. The crew selected for this mission comprised James Lovell as commander, Fred Haise as command module pilot and Ken Mattingly as lunar module pilot. Around two weeks before launch, however, Mattingly was exposed to someone with rubella, and was therefore replaced by backup lunar module pilot Jack Swigert.

The mission launched without major incident on 11 April 1970 and everything went as planned for the first 55 hours of the flight, which covered the Earth orbits and trans-lunar injection burn. At around 10 p.m. central time (03.08 UTC), the mission controllers in Houston, Texas, asked the crew to conduct some routine housekeeping tasks, including turning on the circulating fans in the oxygen tanks.

Due to a section of damaged wiring, the activation of these fans caused one of the oxygen tanks to explode, damaging various critical life support systems and blowing several panels off the side of the service module. For a few minutes, the situation was chaotic, with alarms blaring and the ship tumbling erratically through space. Mission control couldn't figure out which parts of their telemetry were real and which parts were instrumentation failures.

Eventually, however, the crew stabilized the crippled ship and mission control settled on a plan. The crew were to retreat to the lunar lander, which had enough air to keep them alive for the return to Earth, and mission control would give them instructions on how to set the spacecraft on a "free return" trajectory – looping around the Moon and then flying straight back to Earth for landing.

This trajectory saw Apollo 13 swing around the moon at a higher altitude relative to the lunar surface than any previous Apollo mission – 254 km (157 mi). It is often said that this high fly-by is the reason why it holds the altitude record, but this is not so. At the time of Apollo 13's scheduled arrival in lunar orbit, the Moon would have been around 80 km more distant than it was for Apollo 10 so it would have broken the record regardless, although not by so wide a margin.

Despite the mission coming terrifyingly close to disaster, the Apollo 13 crew returned to Earth unscathed, albeit having never set foot on the Moon. No subsequent Apollo mission travelled to the Moon so close to its apogee, and no humans have ventured beyond low-Earth orbit since Apollo 17 in 1972. As a result, this record has stood for more than 50 years.