Modifying a Spacecraft to Enter a Station
Salyut 1 entered orbit in April 1971 as the Soviet Union's first step toward testing long-duration crewed space stations. Soyuz 10 had approached and connected to it but had not completed the docking operations needed for crew entry. Soyuz 11 therefore undertook the tasks of activating station equipment, testing conditions for prolonged living and work, and conducting scientific experiments.
To permit internal transfer, the Central Design Bureau of Experimental Machine Building, led by Vasily Mishin, modified Soyuz with an active docking device containing a passage. Department 231 developed the transport configuration under the coordination of deputy chief designers Bushuyev and Tsybin, while the Azov machine-building plant manufactured the new docking mechanism. After locking and checking the seal, the crew could remove the probe and receiving device and pass through the connecting tunnel into the station, without an extravehicular transfer.
A Replacement Crew Flew to Salyut 1
An abnormality in Kubasov's lungs appeared during the original prime crew's prelaunch medical examination, and the State Commission decided on June 4 to replace the whole crew. Georgy Dobrovolsky became commander, Vladislav Volkov flight engineer and Viktor Patsayev research engineer. Only Volkov had previous spaceflight experience.
Soyuz 11 launched from Baikonur on June 6 and docked with Salyut 1 the following day. Controllers at Yevpatoria in Crimea awaited confirmation of the connection and seal checks. On entering the station, the cosmonauts activated air-regeneration equipment and replaced ventilation components. A burning smell prompted them to retreat temporarily into Soyuz; they began work once the station's air improved.
Long-Term Occupation Was Also an Engineering Test
Salyut 1 provided about 90 cubic meters of habitable space, with worktables, sleeping bags, food refrigeration and sanitary facilities with separate ventilation. While docked, Soyuz's solar arrays could also supply the station, bringing the combined array area to 42 square meters. The complex was both a laboratory and an integrated test of attitude control, power, air and docking systems.
The crew made medical measurements of cardiovascular function, bone tissue and vision, studied plant growth with the Oasis hydroponic apparatus, and took multispectral Earth images. Operations also revealed limitations: vibration from exercise equipment traveled to solar panels and antennas, affecting exercise, while the solar telescope's external cover failed to open, preventing observations. Station work required continuing adjustments among experimental plans, equipment condition and crew adaptation.
Stellar Spectra Supplied Testable Data
In a 1972 paper, G. A. Gurzadyan and J. B. Ohanesyan of Byurakan Astrophysical Observatory reported that the Orion instrument obtained nine spectra of Alpha Lyrae and six of Beta Centauri. They covered 2,000–3,800 angstroms, with a resolution of about 5 angstroms near 2,600 angstroms. Crew members identified targets and performed initial pointing; precise tracking and exposures of different durations then proceeded automatically.
The instrument used a 280-millimeter-diameter mirror and a slitless spectrograph. Film returned to Earth in the capsule for processing, and researchers used its unexposed portions to make calibration records controlling for fogging from space radiation. The paper presented spectra and microphotometric curves and identified a magnesium-ion absorption feature near 2,800 angstroms. Analysis of the full continuous energy distribution remained unfinished at the time.
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Depressurization Before the Capsule Landed
On June 29, the crew organized its experimental results and left the station. The capsule eventually landed automatically in Kazakhstan early on June 30 Moscow time, still the evening of June 29 in Universal Time. The mission lasted approximately 23 days 18 hours. Rescuers opened the hatch to find all three cosmonauts dead, and resuscitation attempts failed.
The investigation focused on a pressure-equalization valve that opened prematurely during module separation. Cabin air escaped at high altitude, and the crew's flight clothing could not sustain life during depressurization. An indicator-light problem had occurred earlier while closing the hatch, but subsequent inspection found the hatch seal intact. Repeated tests examined the mechanism triggering the valve failure, and investigators recommended improvements to shock resistance, rapid manual closure and personal protection.
Scientific Results and Safety Changes Both Remained
A commission chaired by Soviet Academy of Sciences president Mstislav Keldysh completed the investigation in August. Later Soyuz spacecraft made room for pressure suits and life-support equipment by reducing crews from three to two, while the Zvezda machine-building plant developed the Sokol-K pressure suit. Uncrewed flights tested modified equipment in 1972, and Soyuz 12 resumed crewed test flights in 1973.
The next planned stay aboard Salyut 1 was canceled, and the station made a controlled reentry on October 11. Soyuz 11's spectra were not lost with the crew; subsequent observational papers preserved the results. The flight demonstrated that people could enter an independently launched station and conduct sustained research, while making protection against depressurization during a transport spacecraft's return an engineering problem that future crewed missions had to address.