https://en.wikipedia.org/wiki/Soyuz_11 https://en.wikipedia.org/wiki/Soyuz_11 The mission ended in disaster when the crew capsule depressurised during preparat

https://en.wikipedia.org/wiki/Soyuz_11 https://en.wikipedia.org/wiki/Soyuz_11 The mission ended in disaster when the crew capsule depressurised during preparations for re-entry, killing the three-person crew.[9] The three crew members of Soyuz 11 are the only humans to have died in space.[b][10]