Three Russian cosmonauts are scheduled to launch to the International Space Station on Friday, in what should be a routine mission to the orbiting outpost but is now taking place in the midst of Russia’s invasion of Ukraine.

The planned liftoff has drawn increased scrutiny as the conflict in Ukraine has strained relations between Russia and its space station partners, including NASA, and has cast doubt on the iconic orbiting lab’s future.

Cosmonauts Oleg Artemyev, Denis Matveev, and Sergey Korsakov are scheduled to launch from Russia’s Baikonur Cosmodrome in southern Kazakhstan at 11:55 a.m. ET aboard a Soyuz rocket and capsule. The trio will spend about six and a half months living and working on the orbiting lab, and will replace three of the seven crew members currently on board.

On March 30, Russian cosmonauts Pyotr Dubrov and Anton Shkaplerov, as well as NASA astronaut Mark Vande Hei, will return to Earth in a Soyuz capsule.

NASA, Russia’s Roscosmos space program, the European Space Agency, the Canadian Space Agency, and the Japan Aerospace Exploration Agency collaborated on the International Space Station. The outpost in low-Earth orbit was built starting in 1998 and finished in 2011.

The space station’s more than 20-year legacy may now be under threat as a civil space victory between two former Cold War adversaries. Dmitry Rogozin, the director of Roscosmos, has repeatedly expressed his displeasure with the United States’ sanctions against Russia, posting angry tirades on Twitter criticizing the US and adding to the escalating tensions.

In late February, he denounced what he called “openly hostile” US policy and threatened the space station’s survival.

“Who will save the ISS from uncontrolled deorbiting and falling into the United States if you block cooperation with us?” he tweeted Feb. 24, according to a translation.

Rogozin got into an online spat with retired NASA astronaut Scott Kelly last week after Kelly chastised Roscosmos for covering up non-Russian flags on Soyuz rockets bought for commercial launches. “Your space program will be worthless without those flags and the foreign exchange they bring in,” Kelly wrote in Russian. “If McDonald’s still exists in Russia, you might be able to find work there.”

Rogozin retaliated by insulting Kelly and referring to him as “defiant” and “destructive.”

In a now-deleted tweet, he said, “Perhaps the dementia and aggression that you have developed is a result of the overload and stress of four flights into space.”

Rogozin stepped up his threats in another tweet, which was quickly deleted, saying: “Get out of here, you moron! Otherwise, you’ll be responsible for the #ISS’s demise!”

Tensions reached a breaking point after a video purportedly showing Dubrov and Shkaplerov leaving the space station without Vande Hei was shared by a Russian state news program. The video sparked fears that Vande Hei, who broke the record for the single longest spaceflight by an American explorer earlier this week, would be imprisoned aboard the space station by Russia.

Vande Hei would return on the Soyuz capsule as planned, according to a subsequent article published on March 14 by the state-run TASS news agency.

Rogozin’s Twitter outbursts contrast sharply with NASA officials, who have maintained a low profile and insisted that space operations are proceeding normally. According to a transcript of his remarks obtained by NBC News, NASA Administrator Bill Nelson said the agency is “continuing to work with all our international partners to continue safe operation of the ISS” in a video town hall held Monday.

“We’ve been meeting almost every day for the past three weeks to ensure the ISS’s safe operations,” Nelson said.