Soyuz 11 was the second planned visit to the world's first space station, Salyut 1. It was launched on June 6, 1971, from Baikonur Cosmodrome in central Kazakh SSR with cosmonauts Vladislav Volkov, Georgi Dobrovolski and Viktor Patsayev on-board.

They successfully docked with Salyut 1 on June 7 and remained on-board for 22 days, for the moment setting space endurance records that would hold until the American Skylab 2 mission in May-June 1973.

On June 30, 1971, after a normal re-entry of the capsule of the Soyuz 11 mission, the recovery team opened the capsule to find the crew dead. It quickly became apparent that they had asphyxiated and the fault was traced to a valve that had been jolted open as the descent module separated from the service module. The two were held together by explosive bolts designed to fire sequentially, but in fact they fired simultaneously while over France. The valve, less than 1 mm in diameter, was supposed to equalise pressure inside the capsule in the final moments before landing, but in this case had instead allowed the cosmonauts' air to leak away into space. Located beneath the cosmonaut's couches, it proved impossible to locate and block the leak before atmosphere was lost.

The cosmonauts were given a large state funeral. U.S. astronaut Tom Stafford was one of the pallbearers.

The Soyuz spacecraft was extensively re-designed after this incident to carry only two cosmonauts. The extra room meant that the crew could wear space suits during launch and landing.

Crew

• Georgi Dobrovolski (1)
• Viktor Patsayev (1)
• Vladislav Volkov (2)

(1) number of spaceflights each crew member has completed, including this mission.

The prime crew for Soyuz 11 consisted of Valery Kubasov, Alexei Leonov and Pyotr Kolodin . A medical X-ray examination four days before launch suggested that Kubasov might have tuberculosis, and as per mission rules the crew were replaced with their back-up. For Dobrovolski and Patsayev this was to be their first space mission.

Mission parameters

• Mass: 6790 kg
• Perigee: 163 km
• Apogee: 237 km
• Inclination: 51.5°
• Period: 88.4 min