This day in history | 1971 Space mission ends in tragedy

Three Russian cosmonauts have been found dead in their space capsule after it made what looked like a perfect landing in Kazakhstan.
Lieutenant-Colonel Georgi Dobrovolsky, Vladislav Volkov and Viktor Patsayev were found dead in their seats on the Soyuz 11 but did not appear to have suffered any physical injuries.
Post mortem examinations are being carried out and the Soviet Government has ordered an immediate inquiry into the tragedy.
The most likely causes are oxygen failure on re-entry into the atmosphere or unknown side-effects of their lengthy stay in space.
The crew had spent a record 24 days in space, the longest period anyone has yet remained “weightless” and experts believe this could be linked to their deaths.
The cosmonauts had become the first men to stay at a space station when they docked with the Soviet Salyut 1. They were conducting scientific experiments and observations during their trip which started when they launched on 6 June.
The tragedy follows a number of problems involving Soyuz craft and could seriously damage the future of the Soviet space programme.
In 1967 Vladimir Komarov became the first man to die in space when the parachute on his Soyuz 1 developed trouble on landing and, after several other troubled missions, the flight by Soyuz 10 was abandoned before any of the crew boarded the space station due to technical difficulties.
The men will be buried at the Kremlin wall alongside Yuri Gagarin, the first man in space.
To acknowledge the magnitude of what the crew undertook they were immediately named Heroes of the Soviet Union. Mr Volkov has been given a Gold Star medal as he was previously named a hero of Soviet Union.

Courtesy BBC News

In context

The inquiry concluded the three cosmonauts on the Soyuz 11 were killed by a fatal rise in their blood pressure caused when the cabin became depressurised.
The cabin became depressurised because air escaped through a hole created when the landing capsule separated from the main craft.
The crew who died – Georgy Dobrovolsky, Vladislav Volkov and Viktor Patsayev – had been brought in as replacements for the original crew when Valery Kubasov became ill.
It was two years before Russia sent another manned craft into space.