Over the past five years, air has been escaping through a Russian section of the International Space Station (ISS) at an ever-increasing rate. NASA and its Russian counterpart, Roscosmos, are still at odds over the root cause of the leak, as well as the severity of the consequences.

The leak was first discovered in 2019 in the vestibule (called PrK) that connects a docking port to the Russian Zvezda module, which Roscosmos launched into low Earth orbit in July 2000. Earlier this year, NASA raised the leak to the highest level of risk, as the air escape rate from the module had doubled from one kilogram of air per day to just over two pounds.

“While the Russian team continues to search and seal the leaks, they do not believe that the catastrophic disintegration of PrK is realistic,” Bob Cabana, a former NASA astronaut who now chairs the ISS Advisory Board, told SpaceNews during a Wednesday meeting. reported. “NASA has expressed concern about the structural integrity of the PrK and the possibility of a catastrophic failure.”

“The Russians believe that continued operations are safe, but they cannot prove to our satisfaction that they are, and the US believes that it is not safe, but we cannot prove to the satisfaction of the Russians that this is the case,” he added.

Russian teams believe the air leak was likely caused by high cyclic fatigue from microvibrations, while NASA teams believe mechanical pressure and stress, residual stress, module material properties and environmental exposure are all at play, according to SpaceNews.

The air leak was addressed in a recent report by NASA’s Office of the Inspector General (OIG), which highlighted its true severity and the risk it poses to the crew. The OIG report stated that the two space agencies appear to disagree on the point at which the leak should be considered unsustainable. NASA and Roscosmos met to discuss the ISS air leak, with NASA officials noting that Roscosmos “is confident that it will be able to monitor and close the hatch to the service module before the leak rate reaches an unbearable level,” according to the report.

“Although teams continue to investigate the causative factors for fissure initiation and growth, the US and Russian technical teams do not have a common understanding of the likely root cause or severity of the consequences of these leaks,” Cabana said. quoted in SpaceNews as saying.

The rate of air leakage from the hole increased about a week before the February 14 launch of the Progress MS-26 cargo spacecraft, which docked at the aft end of Zvezda. The hatch connecting the module to the ISS remained open for five days while the crew unloaded cargo from Progress MS-26 onto the space station, but was later closed.

NASA and Roscosmos are currently monitoring the leak and are preparing to close the hatch to the service module when access is not needed to minimize the amount of air lost and isolate the leak itself from the rest of the space station. If necessary, space agencies are prepared to permanently close the hatch if the leak rate becomes unmanageable. The ISS would operate as normal, but there would be one less docking port for spacecraft delivering cargo to the space station.

As the two space agencies continue to discuss the potential risk, the aging space station nears retirement in the next six years, and its hardware may finally succumb to the wear and tear of the harsh space environment.