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Soyuz TM-5
Mission insignia
Soyuz-tm5.gif
Mission statistics
Mission name Soyuz TM-5
Spacecraft mass 7000 kg
Crew size 3 launched / 2 landed
Call sign Родни́к (Rodnik- Spring)
Launch date June 7, 1988
14:03:13 UTC
Gagarin's Start
Landing September 7, 1988
00:49:38 UTC
202 km SE of Dzhezkazgan
Mission duration 91 days, 10 h, 46 min, 25 s
Number of orbits ~1,475
Apogee 241 km
Perigee 173 km
Orbital period 88.6 minutes
Orbital inclination ~51.6°
Related missions
Previous mission Next mission
Soyuz TM-4 Soyuz-tm6.gifSoyuz TM-6

Soyuz TM-5 was the fifth expedition to the Russian Space Station Mir.

Crew

Launched:

Landed:

(1) number of spaceflights each crew member has completed, including this mission.

Mission highlights

Soyuz TM-5 launched on 1988 June 7 and arrived at Mir on June 9 carrying the second Bulgarian in space, Alexandrov (not to be confused with the Soviet cosmonaut of the same name). He became the first Bulgarian to reach a Soviet space station (Georgi Ivanov failed to reach Salyut 6 on Soyuz 33 in 1979—Alexandrov was his backup). Their launch had been advanced by 2 weeks late in the planning stages to improve lighting conditions for the Rozhen astronomical experiment. On September 5 cosmonauts Alexandr Lyakhov and Abdul Ahad Mohmand undocked from Mir. They jettisoned the orbital module and made ready for deorbit burn to return to Earth. However, unbeknownst to the cosmonauts or the Mission Control Center in Korolev (TsUP), the guidance computer was using the docking software of the Bulgarian Mir mission in June. The deorbit burn did not occur at the appointed time because the infrared horizon sensor could not confirm the proper attitude. Seven minutes after the scheduled time, the sensor determined that the correct attitude had been achieved. The main engine fired, but Lyakhov shut it down after 3 seconds. A second firing 3 hours later lasted only 6 seconds. Lyakhov immediately attempted to manually deorbit the craft, but the computer shut down the engine after 60 seconds.

According to James Oberg (Secrets of Soyuz), in order to restart the automatic descent program for the second burn attempt, Lyakhov had to instruct the computer to ignore the first shutdown. It was therefore running down its checklist as though the first burn had been successful and the ship was on a normal reentry trajectory. The next item on that checklist was to jettison the Equipment Module, which contained, among other things, the primary propulsion system – the very system they needed to deorbit. Mohmand, disregarding a directive to sit back and let Mission Control assess the situation, had scanned the ship’s gauges and displays, and discovered that separation was going to take place in less than a minute. Lyakhov quickly disabled the program. Had he not done so, he and Mohmand would have perished, as the Soyuz Descent Module had only enough air and battery power for a couple of hours.

The cosmonauts were forced to remain in orbit a further day in the cramped quarters of the Descent Module with minimal food and water and no sanitary facilities. Even if the main engine had permitted them to do so, they would not have been able to redock with Mir because they had discarded the docking system along with the orbital module.

Reentry occurred as normal on September 7. After this the Soviets retained the orbital module until after deorbit burn, as they had done on the Soyuz Ferry flights.

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