It was hailed as a post-Cold War collaboration for the good of humanity: two old rivals joining forces to launch the International Space Station (ISS) more than 20 years ago. 

“The International Space Station is regarded as the most complex engineering, scientific, collaborative human feat ever managed,” boasts the U.S. National Aeronautics and Space Administration (NASA). 

But as relations between Russia and the West become increasingly strained due to Russia’s invasion of Ukraine, officials in Moscow announced on Tuesday that Russia will opt out of the ISS after 2024, and concentrate instead on building its own competing outer space infrastructure. 

Analysts say they worry Russia quitting one of the last remaining vestiges of co-operation with the West will set back scientific research and potentially lead to an increased militarization of space. 

“There has been rumbles of this coming for a while, but it is a sad day,” said Mubdi Rahman, the founder of Sidrat Research, a Toronto-based space technology firm. “Even before the invasion of Ukraine and all of [Russian President Vladimir] Putin’s various aggressions, there has been some fragmentation happening in the space community with nations wanting to go on their own.”

CBC News breaks down what Russia’s move means for the ISS, space exploration and the politics of the great beyond.

WATCH | Russia to quit ISS over Ukraine war tensions: 

Who is currently involved in the ISS? 

First launched in 1998, the main organizations working on the station, according to NASA, include the space agencies of the United States (NASA), Russia (ROSCOSMOS), Canada (CSA), Japan (JAXA) and Europe (ESA), which includes the following participating countries: Belgium, Denmark, France, Germany, Italy, The Netherlands, Norway, Spain, Sweden, Switzerland, and the United Kingdom.

Canada’s contribution, for instance, has accounted for an ownership of only around 2.3 per cent of the station, said Adam Sirek, a professor at Western University’s Institute for Earth and Space Exploration in London, Ont.

Why is Russia leaving now? 

With Russian forces shelling Ukrainian cities, and Western sanctions hitting Moscow’s economy, there had been rumblings about Russia quitting the ISS for a while.   

Yuri Borisov, who leads Russia’s state-controlled space corporation Roscosmos, made the announcement about Moscow’s planned departure from the initiative Tuesday during a meeting with Putin. 

Russia, Borisov said, would honour all of its current operational commitments before leaving. 

Previously, Russia had signaled that it intended to leave the station post-2024, while NASA had wanted it to keep running until 2030. 

Some analysts, however, consider Russia’s announcement more of a public relations move than anything. 

“It’s a non-story in my view,” Michael Byers, a professor at the University of British Columbia who studies outer space politics, said of Russia’s announcement. “The Russians say this periodically,” he wrote in an email; then they continue working on missions.

NASA did not immediately reply to CBC News’ requests for comment, nor did the Canadian Space Agency.

What does Russia currently do on the ISS? 

Russian cosmonauts, technology and transport systems are responsible for a host of key functions for the ISS. Russia mostly built one half of the station launched in 1998, while the U.S. constructed the other half. 

The ISS was originally conceived so technology could be shared between different countries; participants are dependent on each other.

For instance, NASA’s solar panels provide much of the power to the station, while Russian technology stabilizes the ISS, keeping it where it needs to be in orbit around Earth. 

“Sharing resources to perform research in space has been a highlight of the ISS program,” Sirek said.

Moreover, Russia has been responsible for transporting cosmonauts to the station for recent missions. NASA contracted out transportation missions to private firms like SpaceX. 

“To be quite frank, the U.S. and the rest of the world still doesn’t have a viable, well-tested solution to get to the ISS,” Rahman from Sidrat Research said. “Russian space vehicles have been the reliable ones to get people up to the ISS.” 

Are tensions between the West and Russia impacting work on the station?

Geopolitical strife has not visibly spilled onto the decks of the ISS. 

As recently as last week, Russian and European astronauts were on a seven-hour space-walk together where they installed platforms on the ISS, deployed nanosatellites and replaced a protective window, according to NASA.

There is no current suggestion from Russian officials that Moscow will stop providing transport or other support to the station before 2024. 

Earlier this month, ahead of Tuesday’s announcement, NASA and Roscosmos announced an exchange agreement which would see NASA astronaut Frank Rubio fly aboard Russia’s Soyuz MS-22 spaceship in September and Russian cosmonaut Anna Kikina fly with SpaceX’s Crew-5 Dragon. Nothing was said in Tuesday’s announcement suggesting these pre-existing collaborations would be cancelled.

WATCH | Canadian civilian heads to the ISS on historic private mission: 

Canadian joins historic private mission to the International Space Station

Entrepreneur and philanthropist Mark Pathy is part of a four-person crew who made history Friday on board the first civilian mission to the International Space Station. The mission isn’t solely about space tourism — crew members plan to conduct several science experiments during their visit.

Looking past 2024, getting replacement parts for Russian-made components on the station is sure to be challenging in light of sanctions and general supply chain issues in building new parts from scratch, Rahman said. 

What happens on the ISS? 

The station is home to a series of research projects that couldn’t be conducted anywhere else. For instance, it’s used to conduct experiments on how long-term weightlessness affects the human body, according to NASA, and it’s “the only place to test technologies that will take humankind farther into space.”

The CSA and Roscosmos have also been co-ordinating several projects on the ISS, said Western University’s Sirek, including space radiation research to enable humans to live longer off the Earth.

“These partnerships and collaborations using Russian technology and parts of the Russian segment of ISS have increased the yield of Canadian research,” Sirek said. 

MDA, the Ontario-based company behind the Canadarm2 on the ISS and a key Canadian company involved with the station, declined to comment. 

Is Russia’s move a precursor to a new arms race in space? 

Space-based technology is already crucial for military campaigns on Earth, including the war in Ukraine, said Rahman, as nations battle to keep control over sensitive information and communications systems. 

“That is why nations like China and India are making sure they have an operational and well-funded space program,” he said.

For now, Rahman said, it’s unclear if Russia’s recent move could harken a return to the 1980s and fears over space-based lasers or the “Star Wars” program to shoot down intercontinental ballistic missiles. 

But he says the move is likely to rachet up concern from military planners and reduce hopes for co-operation on joint scientific projects for the benefit of humankind.

“The militarization of space happens the minute the rocket is launched,” Rahman said. “There is much more going on than what we are privy to in the public.”