Human Spaceflights

International Flight No. 68

Soyuz 33



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Launch, orbit and landing data

Launch date:  10.04.1979
Launch time:  17:34 UTC
Launch site:  Baikonur
Launch pad:  31
Altitude:  194 - 261 km
Inclination:  51,61°
Landing date:  12.04.1979
Landing time:  16:35 UTC
Landing site:  320 km SE of Dzheskasgan

walkout photo

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alternate crew photo

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alternate crew photo

alternate crew photo

alternate crew photo


No.   Surname Given names Position Flight No. Duration Orbits
1  Rukavishnikov  Nikolai Nikolayevich  Commander 3 1d 23h 01m  31 
2  Ivanov  Georgi  Research Cosmonaut 1 1d 23h 01m  31 

Crew seating arrangement

1  Rukavishnikov
2  Ivanov
1  Rukavishnikov
2  Ivanov

Animations: Soyuz

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Double Crew

No.   Surname Given names Position
1  Romanenko  Yuri Viktorovich  Commander
2  Aleksandrov  Aleksandr Panayatov "Sasha"  Research Cosmonaut

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Launch from the Baikonur Cosmodrome; landing 320 km southeast of Dzheskasgan.

Soyuz 33 carried the fourth Interkosmos mission (with Georgi Ivanov, the first cosmonaut from Bulgaria).

At 9 km distance from the station, the Igla automatic docking system was activated. But, as the craft approached to 1,000 meters, the engine failed and automatically shut down after three seconds of a planned six-second burn. Nikolai Rukavishnikov had to hold the instrument panel as the craft shook so violently. After consulting with ground control, the docking system was activated again, but the engine shut down again, and Valeri Ryumin, observing from the station, reported an abnormal lateral glow from behind the Soyuz during the burn. Mission control accordingly aborted the mission and told the crew to prepare to return to earth. It was the first in-orbit failure of the Soyuz propulsion system.

The failure was determined to be a malfunction of the main engine. A pressure sensor in the combustion chamber was shutting down the engine when it seemed normal combustion pressure was not being reached. This shut-down mechanism was designed to prevent propellants from being pumped into a damaged engine thus risking damage and/or an explosion.

It was only in 1983 that the Soviets revealed how serious the situation was. The craft had a back-up engine but it was feared that it may have been damaged by the main engine, potentially leaving the crew stranded with five days of supplies while it would take ten days for the orbit to decay. One option to return the crew if the backup engine was inoperable would have been to use attitude control thrusters to slow the Soyuz below orbit velocity. But there may have not been enough propellant to do this, and the landing point would have been unpredictable if it worked. Another option was to move the station to the Soyuz. The station could have been moved to within 1,000 m of the craft, at which point Soyuz 33 could be docked using its thrusters. But the two crafts were drifting apart at 28 meters per second, and time was needed to calculate the maneuvers. In any event, four crew on the station with one malfunctioning Soyuz and a second Soyuz (the station crew's Soyuz 32, already docked at Salyut 6) with a now-questionable engine (it had the same type as Soyuz 33) was not considered the best option.

The main option was to fire the back-up engine, but this option was not guaranteed to work, even if the engine fired. The nominal burn time was 188 seconds, and as long as the burn lasted more than 90 seconds, the crew could manually restart the engine to compensate. But this would mean an inaccurate landing. If, however, the burn was less than 90 seconds, the crew could be stranded in orbit. A burn longer than 188 seconds could result in too-high loads on the crew during re-entry.

In the end, the backup engine did fire, though for 213 seconds, 25 seconds too long, resulting in an unusually steep trajectory and loads of 10 G's to be endured by the crew. Nikolai Rukavishnikov and Georgi Ivanov were safely recovered. It was the second ballistic entry reported by the Soviets, Soyuz 1 being the first. Others noted that Soyuz 18A was a ballistic reentry, and Soyuz 24 reportedly also was one.

An investigation lasted a month and found that the part that failed had been tested 8,000 times previously without failing, and the Soyuz engine had fired some 2,000 times since 1967, also without a single failure. But the engine was modified for the next flight.




Last update on April 06, 2012.