Salyut 6 EP-1

Soyuz 6 EP-1 was a 1978 Soviet manned space flight to the orbiting Salyut 6 space station, during the expedition EO-1. It was the third manned flight to the station, and the second successful docking. It was also the first crew to visit an occupied station and marked the first time that three spacecraft were docked together. The launching spacecraft was Soyuz 27 (Russian: Союз 27, Union 27), and the crew of EP-1 are often referred to as the Soyuz 27 crew.

The main function of the mission was to swap Soyuz craft with the orbiting crew, in so doing freeing a docking port for a forthcoming supply tanker. Cosmonauts Vladimir Dzhanibekov and Oleg Makarov returned to earth in the Soyuz 26 spacecraft after spending five days on the station.

The Soyuz 27 crew comprised the original prime and back-up commanders for the scheduled East German Intercosmos mission. Dzhanibekov and Makarov were reassigned as a result of the Soyuz 25 dock failure and the new rule that no all-rookie crew was allowed to fly. Soyuz 27 was launched with its two-man crew on 10 January, 1978. Its primary goal was to swap ships with the resident Soyuz 26 crew and thereby free up the aft port of the Salyut 6 space station for the upcoming Progress 1 resupply mission (Mission control was not yet willing to attempt to redock Soyuz 26 to the other port, a now-standard practice). Its immediate goal was to ensure the station's forward port was a functional dock.Soyuz 25 had failed to dock with the forward port the previous October, and a December spacewalk and inspection by the Soyuz 26 crew had seemed to indicate that the docking problem was a fault of the Soyuz 25 craft rather than the Salyut's dock. The Soyuz 25's dock mechanism was burned up and destroyed during reentry and could not be inspected.

Dzhanibekov noticed that as he and Makarov approached the station in Soyuz 27, they were slightly off-course, but he allowed the automatic system to continue and, with 7 metres (23 ft) to go, it corrected the slight alignment error. To the relief of mission control, Soyuz 27 successfully docked at the forward port. While the docking took place, Grechko and Romanenko moved into Soyuz 26 and closed the hatches in case of an accident. It was the first-ever docking of three independently launched spacecraft.