Soyuz 25

Soyuz 25 was an uncrewed Soviet spacecraft launched on October 9, 1977, intended to dock with the Salyut 6 space station. It marked the first attempt to crew the Salyut 6 station, which had been launched two weeks prior. The crew consisted of cosmonauts Vladimir Kovalyonok and Valery Ryumin.

The mission was plagued by docking problems. Several attempts to achieve a hard dock with Salyut 6 failed. The reasons for the failure were never definitively determined, though theories included a faulty docking mechanism on either Soyuz 25 or Salyut 6, or pilot error.

Due to the inability to dock and limited onboard resources, the mission was aborted after just two days in orbit. Soyuz 25 returned to Earth on October 11, 1977, landing approximately 185 kilometers northwest of Tselinograd. The mission was considered a partial failure, as it did not achieve its primary objective of crewing the space station. This failure led to modifications in the Soyuz docking system for subsequent missions.