Previously posted at: https://www.history.com/this-day-in-history/soviet-cosmonauts-perish-in-reentry-disaster
The three Soviet cosmonauts who served as the first crew of the world’s first space station die when their spacecraft depressurizes during reentry.
On June 6, the cosmonauts Georgi Dobrovolsky, Vladislav Volkov, and Viktor Patsayev were launched into space aboard Soyuz 11 on a mission to dock and enter Salyut 1, the Soviet space station that had been placed in orbit in April. The spacecraft successfully docked with the station, and the cosmonauts spent 23 days orbiting the earth. On June 30, they left Salyut 1 and began reentry procedures. When they fired the explosive bolts to separate the Soyuz 11 reentry capsule from another stage of the spacecraft, a critical valve was jerked open.
One hundred miles above the earth, the capsule was suddenly exposed to the nearly pressureless environment of space. As the capsule rapidly depressurized, Patsayev tried to close the valve by hand but failed. Minutes later, the cosmonauts were dead. As a result of the tragedy, the Soviet Union did not send any future crews to Salyut 1, and it was more than two years before they attempted another manned mission.