Soyuz 25 (Russian: Союз 25, Union 25) was a 1977 Soviet manned space flight, the first to the new Salyut 6 space station, which had been launched 10 days earlier. However, the mission was aborted when cosmonauts Vladimir Kovalyonok and Valery Ryumin failed to engage the docking latches of the station despite five attempts. Lacking sufficient fuel to attempt a dock at the other end of the station and with battery power for only two days, they returned to Earth. The failure led to a new rule whereby every crew had to have at least one person aboard who had previously flown in space.