Soyuz-11 begins a fateful expedition

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Soyuz 7K-T spacecraft variant

A special version of the Soyuz spacecraft adapted for the purpose of carrying the crew to the station was designated 7K-T, where “T” stood for transport. The transport ship received a new docking port, which featured a hatch for crew, enabling internal transfer to the station in the short-sleeve environment. The modified Soyuz also lost its large thorus-shaped avionics section in its tail. Most of its contents, including crucial rendezvous antennas, were moved to the habitation section in front. The 7K-T version of the spacecraft could still accommodate three cosmonauts, tragically only as long as, they would fly without spacesuits. At the time, the probability of losing pressure in the cabin was considered very low.

Previous chapter: Soyuz-11 accident

oyuz-11 crew during training.

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Soyuz-7K-T spacecraft at a glance:

Spacecraft designation	Soyuz, 7K-T No. 32, 11F615A8
Launch vehicle	11A511 (Soyuz)

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Origin of the 7K-T variant

With the end of the Moon Race, the USSR quietly shifted its focus in human space flight to the Earth-orbiting station. Accordingly, the Soyuz was re-tailored for the role of a ferry, capable of delivering a crew of three to the outpost. The first such vehicle, designated Soyuz-10, flew in 1971. However the same year, mission of Soyuz-11 ended in a disaster, when its three cosmonauts died as a result of a decompression of their reentry capsule on the way home. In the wake of the catastrophe, the crew size aboard Soyuz was reduced to two to save mass for newly introduced pressure suits and related safety gear.

Soyuz-12 (498/491)

A death of three cosmonauts onboard Soyuz-11 prompted leaders of the Soviet space program to make a major revision of their approach to safety. No cosmonaut would ever be allowed to launch, land or conduct docking operations onboard Soyuz without wearing a protective spacesuit in case of depressurization. It was harder said than done, because all existing Soviet spacesuits were far too bulky to fit into a small Kazbek seat of the Soyuz spacecraft, which required cosmonauts to keep “an embryo” pose during launch and landing. To resolve the problem, engineers at the Zvezda enterprise urgently fashioned a special rubber-made Sokol-K rescue suit based on previous designs for military aircraft pilots. Although they managed to keep the mass of the Sokol-K at just 10 kilograms, the addition of an emergency air supply kit into an already cramped descent module forced to reduce the crew size onboard future Soyuz ships from three to two.

During an uneventful flight, the Sokol-K suit would be ventilated with a cabin air, however with a sudden loss of cabin pressure, it would instantly switch to a supply of mixture of oxygen and nitrogen. Cosmonauts were certified to wear Sokol up to 30 hours under normal circumstances and up to two hours in the unpressurized cabin. This time was considered enough to make an emergency return to Earth. Sokol-K could even help cosmonauts to survive in the cold water, even though Soyuz crews would also have specialized Forel flotation suits in their safety kits.

In a drastic move to save mass, the Soyuz was stripped of its solar panels. Proponents of the measure argued that for short trips to the space station, onboard batteries would suffice. The new version of the spacecraft was designated 7K-T, where “T” stood for “transport.”

A year after the Soyuz-11 tragedy, the flight testing of the 7K-T spacecraft started with an unmanned launch on June 26, 1972. In accordance with the Soviet practice, the identity of the spacecraft was kept secret behind the public designation Kosmos-496.

Following a successful landing of Kosmos-496 on July 1, the transport Soyuz was declared fit for its role of a taxi to the space station. However two Soviet attempts to orbit Salyuts in July 1972 and May 1973 failed. With no destination to go to, another unmanned Soyuz was launched in June 1973 for a series of tests under a cover name Kosmos-573.

Finally, more than two years after the Soyuz-11 tragedy, on Sept. 27, 1973, the Soyuz-12 resumed the Soviet manned space flight. Cosmonauts Vasily Lazarev and Oleg Makarov, who spent two years preparing to work onboard both ill-fated space stations, DOS-2 and DOS-3, had to content with a two-day test flight.

Still, in addition to trying out their new safety gear, cosmonauts were able to practice the scientific work that would later become a routine activity onboard the future Soviet space stations. They photographed the Earth in six different bands of spectrum covering infrared and ultraviolet range.

Next chapter: Loss of Soyuz-11 crew

The article by Anatoly Zak; Last update: August 10, 2024

Page editor: Alain Chabot; Last edit: June 6, 2021

The original primary crew of the Soyuz-11 mission (left to right) Petr Kolodin, Valery Kubasov and Aleksei Leonov. Nikolai Rukavishnikov from the Soyuz-10 crew is on the right. Click to enlarge. Credit: Roskosmos

docking port

launch

Soyuz launch to the Salyut-1 space station. Credit: RKK Energia

DOS-1

The Salyut-1 space station in orbit. Credit: RKK Energia