Soyuz 15

Soyuz 15 was the attempted second crewed mission to Salyut 3, the Almaz military station. Gennady Sarafanov and Lev Demin launched from Baikonur Site 1/5 on August 26, 1974, reached the station, but were unable to dock because of a fault in the automated Igla rendezvous and docking system. Spacefacts records that the Soyuz 15 spacecraft lacked the reserves or backup systems needed for repeated manual docking attempts, so the mission was abandoned and the crew returned to Earth on August 28 after a little more than two days in orbit. The failure led to modifications of the Soyuz Igla docking system, but those changes could not be completed before Salyut 3's orbital lifetime ended. The mission nevertheless belongs with the Salyut 3 / Almaz record because it tested the station operations plan and exposed a critical docking-system limitation.