Video: 'Soyuz 11 - Death Of Three Astronauts'

(Wednesday, June 30, 1971, approximately 1:47 a.m. Moscow Standard Time) — After a successful mission aboard Salyut 1, the world’s first manned space station, the crew of the Soyuz 11 spacecraft were killed today during their return into Earth’s atmosphere after 23 days on the orbiting station, setting a new record for time spent in space.

When the recovery team reached the capsule after its landing, they opened the hatch and found the bodies of all three cosmonauts — Colonel Georgi T. Dobrovolsky and engineers Vladislav N. Volkov and Viktor I. Patsayev.

An investigation later determined that a faulty valve within the Soyuz capsule had caused the oxygen within the capsule to slowly leak out as the craft was descending to Earth.

The three crew members of Soyuz 11 are the first (and only) humans known to have died in space.