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front port. Moving a replacement Soyuz to the front port became standard procedure; it freed the aft port for Progress supply ships. |}

	Soyuz 32	February 25-June 13, 1979
	Launch crew—Vladimir Lyakhov, Valeri Ryumin Crew code name—Proton Landing crew—none Its long-duration crew spent 175 days on Salyut 6. Less than 2 months into their stay, Soyuz 33 failed to dock because of a main engine malfunction. Soyuz 32 returned to Earth unmanned with a cargo of experiment results and equipment no longer in use after Soyuz 34 had docked unmanned with Salyut 6 to replace it.

	Soyuz 33	April 10-12, 1979
	Nikolai Rukavishnikov, Georgi Ivanov/Bulgaria Crew code name—Saturn Failed to dock with Salyut 6. Fired its main engine while closing to within 4 km of the station. The burn, the sixth of the flight, was to have lasted 6 sec, but the engine shut down after 3 sec. The Igla docking system also closed down. The Proton crew aboard Salyut 6 reported flames shooting sideways from the main engine, toward the backup engine, at the time of the shutdown. The docking was called off and the Saturns made ready to return to Earth. The backup engine fired, but did not shut off at the end of the planned 188-sec burn. Rukavishnikov, uncertain if the engine operated at the proper thrust, determined to let it burn an additional 25 sec before shutting it down manually. As a result, Soyuz 33 made a steep ballistic reentry with gravity loads up to 10 g’s. Because the service module was discarded after deorbit burn, examination of the failed engine was impossible. The Soyuz 33 crew was to have traded its spacecraft for Soyuz 32.[1]

	Soyuz 34	June 6-August 19, 1979
	Launch crew—none Landing crew—Vladimir Lyakhov, Valeri Ryumin Crew code name—Proton Launched unmanned to replace Soyuz 32 following the Soyuz 33 failure. Soyuz 34 included main engine modifications made to prevent a recurrence of the Soyuz 33 failure.[2]

	Soyuz 35	April 9-June 3, 1980
	Launch crew—Leonid Popov, Valeri Ryumin Crew code name—Dneiper

1. V. Golovachev, “Unsuccessful First Soviet-Bulgarian Mission in Soyuz 33 Recalled,” TRUD, June 8, 1988, pp. 5-6. Translated in JPRS Report, Science & Technology, USSR: Space, February 16, 1989 (JPRS-USP-89-004), p. 19.
2. Golavachev, p. 20.