After years of failed attempts to locate and repair a persistent air leak aboard the International Space Station, the Russian space agency is reportedly preparing to shut down the affected section of the orbital outpost.
The leak was first detected in 2019 in the PrK transfer tunnel that connects a docking port to the Russian Zvezda module. Since then, NASA and its Russian counterpart, Roscosmos, have tried several times to repair it, but to no avail. Roscosmos appears to have decided to permanently close the hatch between the Zvezda module and the PrK tunnel in an attempt to isolate the leak from the rest of the space station, according to Anatoly Zak, the American journalist behind RussianSpaceWeb.
Loop
Next month, Russia will launch the Progress MS-36 cargo spacecraft to deliver supplies to the ISS. According to Zak’s report, this will be the first resupply mission hit; rather than unloading via Zvezda, the Progress MS-36 will be unloading via the hatches of Poisk, another Russian module.
Gizmodo contacted NASA to confirm the permanent closure of the transfer chamber to the Zvezda module, but did not hear back before publication. Neither NASA nor Roscosmos have released a statement regarding this decision.
Russian space industry analyst Georgy Trishkin, citing his own sources, says NASA pressured the Russian space agency to permanently plug the air leak by closing the PrK tunnel, Russian newspaper The Insider reported.
The two space agencies reportedly disagree on the root cause of the leak, as well as its severity. Tensions came to a head earlier this year when five ISS astronauts were asked to shelter in place as Roscosmos prepared a risky plan to repair the leak.
After identifying new suspected leak areas in PrK, Roscosmos had two of its cosmonauts use a saw, as reported by Ars Technica, to gain better access to an area that may have contributed to the leak. NASA officials reportedly disagreed with the Russian method to combat the air leak, noting that the new strategy “could have resulted in high structural risk in the area.”
The air leak saga
Since it was discovered, the leak not only persisted, but also worsened. The service module’s air leak rate doubled from one pound per day to just over two pounds per day, NASA officials said in February 2024, before peaking at 3.7 pounds per day in April, according to a report from NASA’s Office of Inspector General. This led NASA to elevate the leak to the highest risk level.
In June 2025, things start to look more promising. NASA measured a new pressure signal (a change in airflow or cabin pressure picked up by sensors), which may indicate that the leaks have been plugged.
Less than a year later, Russian cosmonauts were unloading cargo from the Progress 95 spacecraft when they noticed a slow drop in pressure in the PrK tunnel. This meant that air was still leaking from the space station and any promising signs of slowing down were false.
Following Russia’s aborted plan to cut support inside the tunnel, the two space agencies reportedly continued to argue over the issue before Roscosmos agreed to decommission the PrK tunnel.
With the hatch closed, the idea is to minimize the amount of air lost and isolate the leak itself from the rest of the space station. This also means that Russian cosmonauts will no longer have access to the tunnel and Roscosmos will have to use other docking ports to transfer supplies to the ISS.
If the transfer tunnel were indeed plugged, it would mark the end of several attempts (some of them questionable) to repair the leak while highlighting the growing challenges of maintaining the aging space station.
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