An Equatorial Guinea stamp commemorating those cosmonauts who had lost their lives in the Soyuz 11 spacecraft.
In those who have died in the pursuit of spaceflight, only the crew of Soyuz 11 was exposed to the environment above the Kármán line, which lies at an altitude of 100 km (62 mi; 330,000 ft) above the Earth’s sea level, and commonly represents the boundary between the Earth’s atmosphere and outer space. So technically, even to date, only three people have died in space: Georgiy Timofeyevich Dobrovolsky (b. June 1, 1928), Viktor Ivanovich Patsayev (b. 19 June 1933) and Vladislav Nikolayevich Volkov (November 23, 1935).
Soyuz 11 was the only manned mission to board the world’s first space station, Salyut 1 (Soyuz 10 had soft-docked but had not been able to enter due to latching problems). The mission arrived at the space station on 7 June 1971 and departed on 30 June. The mission ended in disaster when the crew capsule depressurized during preparations for reentry, killing the three-man crew.
After the disaster, there were changes made to the valves in the Soyuz descent module to make them safer,and it’s now a mission rule that cosmonauts and astronauts must wear their proper spacesuits during descent as an added protection against decompression. Not a single cosmonaut or astronaut has lost their lives because of decompression since 1971.