Soyuz 21

Soyuz 21

Operator	Soviet space program
COSPAR ID	1976-064A
SATCATno.	8934
Mission duration	49 days, 6 hours and 23 minutes
Orbits completed	791
Spacecraft properties
Spacecraft	Soyuz 7K-T No.9
Spacecraft type	Soyuz 7K-T/A9
Manufacturer	NPO Energia
Launch mass	6,750 kg (14,880 lb)
Landing mass	1,200 kg (2,600 lb)
Crew
Crew size	2
Members	Boris Volynov Vitaly Zholobov
Callsign	Байкал(Baikal- "Lake Baikal")
Start of mission
Launch date	6 July 1976, 12:08:45UTC
Rocket	Soyuz11A511
Launch site	Baikonur1/5
End of mission
Landing date	24 August 1976, 18:32:17 UTC
Landing site	200 km at the southwest ofKokshetau,Kazakhstan
Orbital parameters
Reference system	Geocentric orbit
Regime	Low Earth orbit
Perigee altitude	193 km (120 mi)
Apogee altitude	253 km (157 mi)
Inclination	51.6°
Period	88.7 minutes
Docking withSalyut 5
Docking date	7 July 1976, 13:40:00 UTC
Undocking date	24 August 1976, 13:40:13 UTC
Time docked	48 days
Vimpel Diamond patch Soviet stamp featuring Volynov and Zholobov (1976) Soyuz programme

Soyuz 21(Russian:Союз 21,Union 21) was a 1976Sovietcrewed mission to theSalyut 5space station,the first of three flights to the station.The mission's objectives were mainly military in scope, but included other scientific work. The mission ended abruptly with cosmonautsBoris VolynovandVitaly Zholobovreturning toEarthafter 49 days in orbit. The precise reason for the early end of the mission was the subject of much speculation, but was reported to be an emergency evacuation after the Salyut atmosphere developed an acrid odor.

Crew

Position	Cosmonaut
Commander	Boris Volynov Second and final spaceflight
Flight Engineer	Vitaly Zholobov Only spaceflight

Backup crew

Position	Cosmonaut
Commander	Vyacheslav Zudov
Flight Engineer	Valery Rozhdestvensky

Reserve crew

Position	Cosmonaut
Commander	Viktor Gorbatko
Flight Engineer	Yury Glazkov

Mission parameters

• Mass:6,750 kg (14,880 lb)
• Perigee:193.0 km (119.9 mi)
• Apogee:253.0 km (157.2 mi)
• Inclination:51.6°
• Period:88.7 minutes

Mission highlights

Salyut 5,the last dedicatedmilitaryspace stationin theSovietspace program,was launched 22 June 1976. Its first crew was launched 14 days later on 6 July 1976, with Commander Volynov and Flight Engineer Zholobov aboard Soyuz 21. Based on landing opportunities, observers estimated the mission was intended to last 54 to 66 days.They docked with the station the next day, and gave a televised tour 8 July 1976.

Their stay coincided with the start of the Siber military exercise inSiberia,which they observed as part of an assessment of the station's military surveillance capabilities. They conducted only a few scientific experiments, including the first use of the Kristall furnace forcrystalgrowth. Engineering experiments included propellant transfer system tests with implications for future operation of the freight-carryingProgress spacecraft.

Experiments conducted during the mission were mainly of amilitary natureas part of theAlmazprogram. Various purely scientific tasks were also carried out, includingsolar observationsandbiological observationsof anaquarium of fishcarried into orbit.A television link-up with school children on 17 August 1976 was also undertaken.

On 24 August 1976, it was announced the mission was to end in only 10 hours, a development which caught even the reporters ofRadio Moscowby surprise.The reason for the sudden termination of the mission was reported at the time to have been an acrid odor that developed in the environmental control system. The problem was said to have begun as early as 17 August 1976.The Soviets made no comments at the time, but the next crew to board the station wore breathing masks.Later reports indicate that the mission may have ended owing to a deterioration in the health of Zholobov. The mission was to last two months but was cut short by a gradually worsening illness of Zholobov.

Thecosmonautsboarded Soyuz 21 but as Volynov tried to undock from the station, the docking latches failed to release properly. As he fired the jets to move the spacecraft away, the docking mechanism jammed, resulting in the Soyuz being undocked but still linked to Salyut. As the two spacecraft moved out of range of ground communications, the cosmonauts received only the first set of emergency procedures. Volynov tried a second time to undock but only managed slightly to loosen the latches. The situation persisted for an entire orbit, 90 minutes, when the final set of emergency procedures were received and the crew finally disengaged the latches.

Because Soyuz 21 was returning early, it was outside the normal recovery window. It then encountered strong winds as it descended, which caused uneven firing of the retrorockets. It made a hard landing around midnight 200 km (120 mi) at the southwest ofKokchetav,Kazakhstan.

Zholobov's illness was apparently caused bynitric acidfumes leaking from the Salyut's propellant tanks; other reports, however, indicate that the crew failed to follow their physical exercise program and suffered from lack of sleep.Sources atNASAhave reported that psychologists with theRussian Aviation and Space Agencycited Soyuz 21 as ending prematurely due to unspecified "interpersonal issues" with the crew.The next mission to successfully dock with the station,Soyuz 24,would vent Salyut 5's air to space and replace it due to concerns the air had become toxic.