Russian cosmonauts became the only people to die in space after spending 23 days orbiting Earth

The space race. A fierce battle of the cosmos between Soviet Russia and the United States of America spanning two decades of the twentieth century.

While a thing of the past, it saw humanity land on the Moon for the very first time while significantly advancing technology back here on Earth, from scientific understanding of space to advancements in the world of GPS and satellites.

There was also elements of tragedy. And while the tragic tale of the USSR's space dog called Laika is enough to pull at the heartstrings, humans have also died while in service to their country's space agency.

One of the worst incidents to result in the loss of human life was the fate of the Soyuz 11 crew which headed in to space back in June 1971. Three Russian cosmonauts ventured in to space and returned in the most tragic of circumstances.

Voyage of the ill-fated Soyuz 11

The tragic tale of Soyuz 11's cosmonauts and their journey back to Earth (STAFF/AFP via Getty Images)

Blasting off from modern day Kazakhstan, Soyuz 11 had a crew of three cosmonauts with Georgi Dobrovolski, Vladislav Volkov and Viktor Patsayev heading for the world's first ever space station Salyut 1.

Arriving at Salyut 1 on 7 June, 1971, the trio of engineers spent a total of 23 days onboard the space station where they lived conducting a variety of experiments in the orbiting laboratory.

There was a particular focus on experiments to study humanity's ability to undergo long-duration spaceflights, with experiments including exercising on the space station's treadmill and monitoring their state of health.

To maximise their output, they worked in three shift patterns so that there was always one person working at any one time.

Time onboard the Salyut 1 space station

An artist's impression of the Russian Soyuz 11 spacecraft linking up with the Salyut 1 space station (Keystone/Hulton Archive/Getty Images)

Dobrovolski, Volkov, and Patsayev became stars back home in Soviet Russia after treating citizens of the USSR to almost daily broadcasts of their activities in space while explaining what they were getting up to in their experiments.

"Soviet journalists dubbed the events Cosmovision," NASA explained.

"They cast ballots from Salyut in Soviet elections, becoming the first people to vote from space."

In journeying to the space station, they set a then-record for the time spent in space for one trip, breaking a previous record set by the Soyuz 9 crew in 1970.

Preparing for Earth and tragedy

The interior of the Salyut 1 space station with the hatchway leading to the Soyuz 11 spacecraft (Sovfoto/Universal Images Group via Getty Images)

29 June was the final day that the trio spent on the Salyut space station, with them packing up the Soyuz 11 spacecraft with their samples and scientific research that they had worked on for more than three weeks in the void of space.

Getting ready to leave the space station, a warning light had indicated to the cosmonauts that the hatch pressurising the return spacecraft was not sealed.

After seemingly addressing the issue, both crew and ground control agreed the problem was fixed. This was despite the light remaining active up in space.

Slowing down for re-entry to Earth's atmosphere, tragedy occurred nine minutes after the end of the retrorocket's backfire.

At around 80 miles high, explosive bolts separated the spacecraft in to its three components, with the crew inside the middle bell-shaped descent module. It was at this moment that tragedy struck, just 30 minutes from landing.

"The shock from the explosive bolts jarred open a pressure equalisation valve that normally opened only once the spacecraft was descending on its parachute, well inside the atmosphere. But in this case, the valve opened to the vacuum of space and the capsule’s air escaped in less than one minute," NASA explained.

Soviets turned out in numbers to mourn the fallen cosmonauts (Getty Stock Images)

Evidence exists to show the cosmonauts tried to fix the issue by trying to manually close the valve. But with that processing taking minutes, they lost consciousness before they could save their own lives.

Soyuz 11 continued on its journey to Earth where it safely landed. Ground control had some concern after communication went quiet with the crew but it wasn't until they opened the hatch and found the three cosmonauts that they realised just how tragic of a situation this was.

"They were not wearing pressure suits. The Soviet government honored the cosmonauts with a state funeral, with NASA astronaut Thomas P. Stafford representing the President of the United States," NASA writes.

"As a result of the accident, the Soviets temporarily halted human spaceflights while engineers redesigned the Soyuz spacecraft. Since then, all cosmonauts have worn spacesuits during Soyuz launches and landings."