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Soyuz-11 crew lost at landing

On June 30, 1971, the three members of the Soyuz-11 crew lost their lives just minutes from landing when their Descent Module suddenly depressurized on its way back to Earth from the Salyut orbital laboratory.

Previous chapter: Soyuz-11 mission

A photo attributed to the Soyuz-11 mission shows the Descent Module at the landing site.

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Soyuz-11 accident at a glance:

Preparing for landing

On June 29, 1971, at 13:30 Moscow Time, the members of the State Commission, overseeing the operations aboard the Salyut space station, gathered at the main nerve center of the Soviet human space flight at the NIP-16 ground station on the Crimean Peninsula. Vasily Mishin, Designer General at TsKBEM, and other leading engineers in the program landed in the Crimea that very morning after a flight from Tyuratam, where they had overseen the latest launch of the N1 Moon rocket, which ended in another painful failure, just two days earlier.

The State Commission cleared the crew of Soyuz-11 for undocking and landing after a record-breaking 23 days in space. (774) On the evening of the same day, cosmonauts Georgy Dobrovolsky, Vladislav Volkov and Viktor Patsaev got into their seats onboard Soyuz-11 and closed the hatch between the Descent and Habitation modules.

Right away they had a very unpleasant surprise in the form of an “open hatch” signal on their console that remained on after the hatch was actually shut. Volkov, who had already earned a reputation of a less than patient troubleshooter among flight managers, tensely demanded a solution from the ground. On the advice of a fellow cosmonaut Aleksei Yeliseev, who was on shift at mission control, the crew re-opened and re-closed the hatch, but the stubborn light remained on. For the cosmonauts, who had no protective suits, a problem of this sort was an extremely bad omen. The “hatch open” sign could indicate a breach in the air-tight seal of the crew module – a potential death sentence for the crew without protective pressure suits.

In an effort to resolve the issue, mission controllers told the cosmonauts to check a sensor on the edge of the hatch. Dobrovolsky put a small piece of tape under the sensor and closed the hatch again. After a half-an-hour struggle, the warning light finally went off. Some air was then vented out of the Habitation Module, and to their relief, the crew saw no change in pressure in the Descent Module, confirming that the hatch between two compartments remained air-tight.

Soyuz-11 departs Salyut

At 21:25 Moscow Time on June 29, 1971, Soyuz-11 undocked from Salyut. At the request from the ground, Dobrovolsky maneuvered the crew vehicle near the station, while Patsaev took photos of their former home in orbit. A few grainy photos of Salyut in orbit that surfaced decades later were probably taken during that fly around.

At 00:16 Moscow Time on June 30, the Head of cosmonaut training Nikolai Kamanin got on the radio with the crew to report on weather conditions at the planned landing site in the grasslands of Kazakhstan. He promised the cosmonauts a mostly cloudless sky with a visibility of 10 kilometers, a wind speed between 2 and 3 meters per second, a temperature around 16 degrees and air pressure 720 millimeters. Kamanin reminded the crew to provide voice commentary during all phases of the descent via short-wave and UHF antennas and follow the instructions after the touchdown. "Wish you a soft landing and see you on the ground," Kamanin remembered saying. Dobrovolsky responded that everything was well onboard and that crew was in good shape. "Thank you for all the work and good wishes," he concluded.

The telemetry confirmed that everything worked well aboard Soyuz-11, as the ship was completing its third orbit in autonomous flight after departing from Salyut. Some 15 minutes ahead of the 187-second braking maneuver, officials, cosmonauts and engineers crowded into the operational command hall at the NIP-16 ground station in Crimea. (142)

Soyuz-11 fired its engine at 01:35:24 Moscow Time on June 30, 1971. A tracking ship in the Atlantic confirmed that the braking maneuver had gone as scheduled, but several attempts by Vladimir Shatalov to establish voice communications with his fellow cosmonauts aboard Soyuz-11 were unsuccessful. The scheduled time of separation of the Descent Module at 01:47:28 Moscow Time also came and went without voice confirmation by the crew. Between 01:49:37 and 02:04:07 Moscow Time, mission control had a backup communications window with the spacecraft in case it failed to leave orbit, but, once again, it passed in complete silence.

The lack of contact with the cosmonauts was very worrying, but there could be many possible explanations for the problem not involving a catastrophe. In the meantime, Soviet air defense radar detected the crew module at 01:54 Moscow Time, still some 2,200 kilometers away from the projected landing area and tracked its seemingly nominal path to touchdown.

The main parachute opened without a hitch at 02:02 Moscow Time, as the capsule was at an altitude of seven kilometers. The parachute lines contained a powerful antenna which had the capability to transmit voice communications, but once again, nothing came from the crew during the capsule's nearly 15-minute descent under the parachute.

Crews aboard Mi-8 recovery helicopters and an Il-14 fixed-wing aircraft spotted the capsule under its parachute and followed it to the planned landing site, some 202 kilometers east of Dzhezkazgan. While there were still no communications with the crew, the Descent Module touched down normally with the burst of soft-landing engines at 02:16:52 Moscow Time.

Four helicopters landed nearby almost immediately, and search specialists rushed to the capsule. It took them only a minute to open the hatch and discover the lifeless bodies of the three cosmonauts. Their seat belts were partially unbuckled. Rescue doctors tried in vain to resuscitate the victims, after they had been urgently extracted from the capsule.

Some half an hour after the landing, an air force communications officer called Kamanin to Crimea and said that General Goreglyad radioed on his way from the landing site to Dzhezkazgan that "the outcome of this space flight was most devastating." In his announcement to other members of the State Commission, Kamanin interpreted this news as the death of the crew, but Mishin, Kerimov and Minister Afanasiev naturally refused to believe it and demanded a confirmation of the report from Goreglyad. It took another hour to finally confirm the worst. (142)

As the terrible news spread throughout the industry, the official Soviet press had no choice but to announce the tragedy to the world. Four years after the loss of Vladimir Komarov and three years after the Apollo fire, the space flight had claimed another three victims.

Investigation

On July 1 and 2, 1971, the USSR went through grim funeral ceremonies. The three fallen cosmonauts were interred in the Kremlin's wall not far from the ashes of Vladimir Komarov who had perished in the botched landing of Soyuz-1 in 1967.

But less than a day after facing relatives of lost cosmonauts on July 2, Mishin and other managers appeared at the meeting of the State Commission at noon on July 3. On the agenda was the formation of several investigative sub-commissions into different aspects of the tragic mission. They included:

By 18:30, the same evening, Mishin's Kremlin bosses Dmitry Ustinov and Leonid Smirnov were also due at TsKBEM in Podlipki.

Leaders of all the sub-groups met at another State Commission meeting on July 5, 1971, at 15:00. On June 6, along with another meeting probing the failed launch of the N1 rocket, the top managers at TsKBEM had a first look at the Descent Module of the Soyuz-11 spacecraft, which was delivered to Podlipki from the disaster site. In his notes, Mishin noted the abnormal appearance of the entrance hatch into the capsule. On July 7, 1971, a "governmental" investigative commission into the Soyuz-11 failure was formed under the chairmanship of Mstilsav Keldysh, the Head of Academy of Sciences.

As late as July 7, Mishin wrote that the hypothesis of a failure of the entrance hatch should not be discarded (from the list of possible accident scenarios), but by July 9, his attention appeared to be fully switched to the pressure equalization system aboard the Descent Module.

After more meetings with investigators on July 10, 11 and 12, Mishin came out from the meeting of the Keldysh commission at TsKBEM on July 13, at 16:00, with the conclusion that the most probable cause of the crew death was the depressurization of the Descent Module in the upper atmosphere through one of two pressure-equalization valves. (774)

The most important information on the sequence of events came from the Mir autonomous register, essentially a “black box” recording the telemetry from various systems aboard the spacecraft. Mir’s data showed that immediately after the separation of the descent module at an altitude of 150 kilometers, the air started venting out of the crew module. In just 115 seconds, the pressure inside the cabin collapsed to an almost complete vacuum. By that time, medical data showed no signs of either pulse or breathing among the crew.

The probe established that Valve No. 2, designed to equalize pressure inside the crew module with the surrounding atmosphere during the final phase of descent, had opened right after the separation of the Descent Module from other compartments. However, it was much more difficult to figure out the reason for the triggering of the fatal opening of the valve in the vacuum of space rather than in the dense atmosphere right before the touchdown.

The rate of air loss inside the Descent Module matched precisely the opening of the valve for equalizing the cabin pressure. However, the telemetry showed that a command to blow up a pyrotechnic device, which triggered the opening of the valve, had been issued exactly as planned, deep in the atmosphere.
During endless simulations on the ground, all efforts to open the valve by imitating the shock of separation between the spacecraft’s modules would fail to produce “desirable” results. Only a combination of the separation shock with an almost completely improbable violations of the valve’s assembly and installation procedures had finally triggered the fatal opening. This scenario became the official explanation for the Soyuz-11 accident.

The available data indicated that as the catastrophe began unfolding with the separation of the Descent Module, the cosmonauts likely saw that the pressure inside the module had started plunging. Perhaps remembering all the troubles with the hatch before undocking from Salyut, they rushed to check it first, but while the hatch was in order, the swooshing sound of the air could be heard in the cabin and the pressure kept dropping with every second. In a desperate effort to pinpoint the breach, they feverishly tried to turn off buzzing radios and ventilators. The cosmonauts seemingly located the fateful valve under Dobrovolsky’s seat and unbuckled their seat belts in order to reach the area. It was theoretically possible to shut down the valve, however, all three lost consciousness from severe decompression within 50 or 60 seconds after the breach had occurred.

By the second half of July 1971, engineers at TsKBEM, involved in the Soyuz-11 accident investigation, mostly switched their focus from understanding the cause of the tragedy to the designing a whole range of measures to prevent a similar situation in the future.

Next chapter: Kosmos-496: Fixing Soyuz-11 flaws

The article by Anatoly Zak; Last update: June 26, 2022

Page editor: Alain Chabot; Last edit: June 30, 2021

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A possible view of the first Salyut space station in orbit. Credit: RKK Energia

Crew of Soyuz-11 likely photographed during training inside the spacecraft simulator. Click to enlarge. Credit: Roskosmos

The Descent Module of the Soyuz-11 spacecraft at the landing site.

Search and rescue specialists extract members of the Soyuz-11 crew from the capsule.

Members of the search and rescue personnel at the Soyuz-11 landing site made a desperate attempt to resuscitate the fallen cosmonauts.

Members of the Soyuz-11 crew lying in state in Moscow.

Soyuz-11 crew funeral ceremony at the Kremlin Wall.

The memorial at the Soyuz-11 landing site. Credit: Roskosmos