The tragic story of the only 3 cosmonauts who died in space

• Three Russian cosmonauts were assigned to the Soyuz 11 mission that launched on June 6, 1971.
• They broke a record at the time for the longest space flight endurance.

About half an hour before the Soviet Union's Soyuz spacecraft was scheduled to touch down on June 30, 1971, in the plains of Kazakhstan, a flight control center in Yevpatoriya in western Crimea was met with an unexpected silence.

Three Soviet cosmonauts — Georgy Dobrovolsky, Vladislav Volkov, and Viktor Patasayev — were making their descent to Earth after a record-breaking time spent aboard the Salyut 1 space station, where they performed experiments and explored the then many unknowns of human space habitation.

The mission, Soyuz 11, launched on June 6, 1971. By the time of the Apollo 11 moon landing two years prior, the longest time humans spent in space was only about two weeks.

This Soviet crew had spent 23 days in space, setting a new record for human space flight endurance, and were finally coming home.

As the ship made its reentry, one crew communicator back in Yevpatoriya expressed concerns about the lack of reports from the cosmonauts.

"We asked Dobrovolskiy the whole time to give us a running commentary as soon as the Descent Module enters our coverage zone, but he hasn't said a word," crew communicator Aleksei Yeliseyev said, according to Boris Chertok, a space engineer who recounted the mission in his four-volume memoir "Rockets and People." "It's strange that Volkov is quiet. During the last session, he was very talkative."

The module carrying the men landed around 2 a.m., about 56 miles southwest of the town of Karazhal. A rescue team was immediately dispatched.

Chertok recalled there were another 20 minutes of silence when the team received no reports.

Finally, one lead Soviet engineer, with a disturbed expression on his face, would break the news he received from Moscow: Seated "in tranquil poses," Chertok wrote, the three cosmonauts were found dead inside the ship.

After the moon race

The Soyuz 11 mission launched as the public's interest in the space arena waned.

By then, Apollo 11 landed on the moon in 1969, which many historians argue was the hallmark event that settled the Great Space Race between the US and the Soviet Union.

"I think there was a kind of fascination in the '60s with space, and this presented all sorts of cultural things like 'Star Trek,'" Asif A. Siddiqi, a Fordham University history professor who wrote extensively on the Soviet space program and edited Chertok's memoirs, said in an interview with Insider. "But I think after the moon race, people just lost interest. People were saying that there's deeper problems at home that we should be devoting our money to."

Still, there was much to explore about space and many milestones yet to be broken.

Scientists had limited knowledge of the impacts of prolonged weightlessness on the human body, for example. The longest humans had spent in space by the time of the landmark moon landing was about two weeks.

"The Soviets were always interested in the long-term effects of human beings in space," Siddiqi said. "You couldn't really think about going anywhere, like Mars, unless you really understood how the human body would react."

To recoup the loss of the moon race, the Soviets quickly pivoted to a space station program. They gathered existing equipment and hastily put together a space station that was launched on April 19, 1971. The ship was named Salyut 1 and was the world's first space station to orbit the Earth.

The first attempt to send cosmonauts to the ship occurred merely three days after Salyut 1's launch. But the four-man crew failed to dock and returned to Earth in less than two days.

The next attempt came during a notably "perfect" June in southern Kazakhstan, Chertok wrote.

"It had rained recently, accompanied by an unusually cold wind for that time of year," he recalled. "As one might expect, the Tyuratam old-timers tried to convince us that they couldn't recall such a pleasant early June."

Three men were assigned to Soyuz 11. However, just two days before the scheduled launch, the discovery of a spot "the size of a chicken egg" inside a flight engineer's right lung would alter the fate of the cosmonauts, according to Chertok.

A backup crew consisting of Dobrovolsky, the commander, Volkov, the flight engineer, and Patasayev, a research engineer, would replace the primary team. One engineer rationalized: A "new crew that hasn't worked together will be worse than the backup crew," Chertok wrote.

Another leap for mankind

Soyuz 11 launched on June 6, 1971. The three cosmonauts would make a landmark achievement by successfully docking onto Salyut 1 the very next day.

The space station was of modest size — comparable to a two or three-bedroom apartment, according to Siddiqi. A lot of the research conducted inside Salyut 1 was related to biomedicine, but the crew performed a wide range of experiments.

According to NASA, Patsayev was the first to operate a telescope in space. Inside the oasis chamber, the cosmonauts grew Chinese cabbage and onions. Patsayev became the first person to celebrate their birthday in space, and the men cast their ballots for the Soviet elections.

Scientists also wanted to closely monitor the impacts of space on the human body. A treadmill was installed on the Salyut 1 and the cosmonauts forwent their space suits in the space station and Soyuz.

"One of the things that they were envisioning is that they wanted to get rid of the space suits because they were trying to secure the spacecraft so that you wouldn't need space suits," Siddiqi said. "It was a concession made in the early days when you weren't sure if the spaceships themselves were secure and safe. So they moved the safety consideration from the suit to the ship … And without the suits, you could put in more stuff, because it becomes spacious inside."

The cosmonauts experienced setbacks including a small fire on board as well as "personality conflicts," according to Siddiqi, but the crew successfully breached an 18-day record also set by the Soviets in 1970.

In total, they spent about 22 days docked at the station. Chertok, the space engineer and author of "Rockets and People," recalled the day the cosmonauts reached the milestone in his memoir with little fanfare.

"We departed from the Crimea after agreeing that Dobrovolskiy's crew should set a new record for time spent in space. A preliminary landing date of 30 June was set," he wrote.

Tragedy inside Soyuz 11

Almost everything about the Soyuz 11 spacecraft functioned as intended.

"The Soyuz spacecraft is a very automated ship, so you don't have to do much," Siddiqi said. "The program to return the Soyuz just kept operating and it operated perfectly."

The descent module that carried the three men oriented itself, the parachute deployed, and in the early hours of June 30, 1971, the ship landed softly in the steppes of Kazakhstan. According to Chertok's memoir, a report also stated that the cosmonauts were in good physical condition in the last few days of their journey.

But a few missteps on the ship and by the Soviet space program led to the tragic deaths of the cosmonauts. Michael Smith, a Cold War historian at Purdue University who studied the Soviet space program, told Insider that he teaches Soyuz 11 "as a case study in risk planning."

Soyuz 11 consisted of three modules. At the front of the ship is a module that operates like the crew's workspace; in the middle is the cabin for the three men; and behind is the service module that carries the engine and power source.

In order to split the modules, small cartridges containing tiny explosives set off at a precise moment in a sequence. However, according to prevailing theory, the cartridges fired off at the same time, Siddiqi said.

The shock of the explosion caused a valve in the cabin to open while the ship was at a lethal altitude. The module quickly decompressed, and in a matter of seconds, the cosmonauts lost consciousness.

"Without space suits and emergency oxygen to protect them, the cosmonauts perished," Smith said.

Just two minutes after landing, a rescue team in a helicopter made contact with the module lying on its side. Chertok recalled a report he heard from Kerim Kerimov, one of the key founders of the Soviet space program:

"They quickly opened the hatch. All three were sitting in their seats in tranquil poses. There were dark blue spots on their faces. Blood was running from the nose and ears. They pulled them out of the Descent Module. Dobrovolsky was still warm. Doctors continued to perform artificial resuscitation. According to their reports from the landing site, death was the result of asphyxiation."

An autopsy report conducted afterward made a "harrowing impression," Chertok wrote:

The valve opened at about a 105-mile altitude, above the Karman line — an imaginary boundary often used to determine when space flight is reached.

Dobrovolsky, Volkov, and Patsayev are the only humans to date to have died beyond that line.

Had the cosmonauts been wearing space suits, the three men certainly could have survived the event of depressurization, Siddiqi said. However, another pitfall of the mission was insufficient testing, which was partly due to the haste created by the space race.

"A lot of failures in the spaceship don't appear immediately," Siddiqi said. "You have to sometimes test it 50 times before something shows up. So they didn't fly these things enough to really know how it would react."

World nations mourn

A day of national mourning was held along with a massive state funeral, according to Time magazine. Condolences from Soviet leaders were extended to the men's families.

In a message to Nikolai Podgorny, the head of state of the Soviet Union at the time, President Richard Nixon wrote: "The American people join me in expressing to you and the Soviet people our deepest sympathy on the tragic death of the three Soviet cosmonauts. The whole world followed the exploits of these courageous explorers of the unknown and shares the anguish of their tragedy. But the achievement of cosmonauts Dobrovolsky, Volkov, and Patsayev remains."

According to Siddiqi, the death of the three cosmonauts had a lasting impact on the Soviet space program afterward. Another flight attempt wasn't made for more than two years.

"In retrospect, you don't want people to die, but it may have been the one thing that allowed the designers to stop and take a deep breath," he said.

By the late 1970s, there were no more fatalities. The Soviets launched the Salyut 6 space station in 1977 and was an indisputable success. Multiple large crews docked and undocked with the station, and the duration of the missions steadily increased from three months to six months.

"On a happier note, the subsequent Soviet redesigns and improvements to the Soyuz capsules (including space suits for ascent and descent) have been remarkably durable," Smith said. "Soyuz 11 was that last fatal space disaster for the Soviet Union and Russian Federation."