The second generation orbital stations («Salyut-6» and «Salyut-7») had two docking units which significantly expanded the stations' operation capabilities.
 An important stage in the provision of the «Salyut-6» and «Salyut-7» stations' operation was the use of «Kosmos» ferry spacecraft. The Center manufactured four such spacecraft: «Kosmos-929», «Kosmos-1267», «Kosmos-1443» and «Kosmos-1686».
  «Kosmos-929» was in flight from July 17,1977 to February 3, 1978. It included a return module which separated from the| s/c and returned to Earth after a month in flight. It was not planned to dock  «Kosmos-929» with the orbital station.
   «Kosmos-126"7» could dock with the station but without creating an inner passage to the orbital station «Salyui-6». It also had the return module which descended to Harth  after 30 days. S/c operated from April 25,  1981 to July 29,1982. the s/c returned to  Earth together with the orbital station. 

«Kosmos-1443» operated together with «Salyut-7», an inner passage was formed and there was a return module. This module descended in 5.5 months after launcher. S/c flight lasted from March 2, 1983 to September 19, 1983.

«Kosmos-1686» was in flight from September 27,1985 to February 7,1991, and created an inner passage to the orbital station «Salyut-7». It had a set of scientific instrumentation instead of a return module.

The ferry spacecraft integrated into the space complex fulfilled the following functions:
• orbit correction for the complexas a whole;
• maneuvering;
• attitude control and stabilization during scientific experiments;
• cargo delivery and return;
• transition to new orbits (operating as interorbital tug).

The ferry, which consisted of an energy module and a return capsule were launched by the «Proton» launcher.