WASHINGTON — NASA says it is studying a long-running air leak on a Russian International Space Station module that recently doubled in magnitude, but that the leak does not currently pose a safety risk.

At a briefing Feb. 28 about the upcoming Crew-8 mission to the station, now scheduled for launch on the evening of March 2, Joel Montalbano, NASA ISS program manager, said the leak in the Zvezda service module increased about a week before the Feb. 14 launch of the Progress MS-26 cargo spacecraft to the station. That spacecraft successfully docked to the aft end of Zvezda two days later.

“The teams are watching it. We’re working with our Russian colleagues on the next step,” he said. “It’s not an impact to crew safety or vehicle operations.”

Montalbano said later that the leak has increased to a rate of more than 0.9 kilograms of air lost per day, double the previous rate detected in that part of Zvezda. When Progress docked to the station, he said they kept the hatch closed for about 24 hours “to let everything dampen out” and see if that affected the leak. “Nothing changed.”

The leak is in a vestibule known as PrK between the docking port and the rest of the module. That section can be sealed off to minimize the loss of air from the rest of the station.

Montalbano said that, once the hatch was opened after the Progress docking, it was kept open for about five days to allow crews to unload the spacecraft, then it was closed. The hatch will remain closed until early April. “We’re working with our Russian colleagues on the next steps,” he said, including future plans to access the vestibule and ways to study the leak.

The PrK leak was first detected in 2019 and has been extensively aanlyzed by Roscosmos and NASA. That included apply Kapton tape to try to plug the leak, as well as installing gauges to measure stresses on the module that could be causing cracks.

In a November presentation to the NASA Advisory Council’s human exploration and operations committee, Robyn Gatens, ISS director at NASA Headquarters, noted the PrK leak rate at the time, about 0.45 kilograms per day, was “manageable” and could be addressed with measures like closing the hatch. “It’s still well below our spec leak rate on the space station, but a little higher than our historical leak rate.”

She played down at that meeting any concerns about a catastrophic failure. “There’s a concern any time a structure is leaking and that’s why the team continues to investigate this and try to understand it,” she said. “The worst-case scenario would be the loss of that port for the space station, but not a catastrophic, existential concern for the International Space Station itself.”

The PrK leak has also been monitored by NASA’s Aerospace Safety Advisory Panel, which in some past meetings has mentioned its concerns about the leak and its implications for the station. The issue did not come up at the panel’s most recent public meeting, also held Feb. 28, because the panel did not get a briefing on the station at this quarterly meeting.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...