SSVP, a probe-and-drogue docking system, is the main docking system used by the Soviet/Russian space program. Ever since the first Salyut 1 mission, only three Soyuz spacecraft, Soyuz 16, Soyuz 19, and Soyuz TM-16, did not equip the SSVP docking system. Mir and the Russian segment of the ISS also make use of SSVP to attach space station modules.

Kristall and Buran notably depart from this tradition. Both were to be equipped with APAS-89 ports, an androgynous docking port modified from the earlier APAS-75 used in the Apollo-Soyuz test program. Kristall had an aft and a radial APAS-89 port. The aft port was originally intended for Buran and later used by the Space Shuttle.

What cause the Soviet to rework a docking standard they only used once instead of using the tested SSVP?


1 Answer 1


The major claimed advantage of the APAS was that it can be applied to more massive vehicles because it incorporates a damping system. Buran was going to be much more massive than Soyuz.

Source: United We Orbit

  • 1
    $\begingroup$ SSVP also looks like it provides a tiny opening, not ideal for moving large amounts of cargo. $\endgroup$
    – Hobbes
    May 4, 2019 at 7:50
  • 3
    $\begingroup$ APAS-89's tunnel diameter is 800mm, same as SSVP. $\endgroup$
    – Mys_721tx
    May 4, 2019 at 15:52
  • $\begingroup$ Buran aside, the only other spacecraft available were Soyuz and Progress. Because of the greater mass of APAS the payload would be reduced for these craft, like a whole cosmonaut less. If it aint broke, don't fix it - so they carried on with SSVP. $\endgroup$ Jan 13, 2022 at 16:53

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