This has been a long-running, largely hidden conflict between NASA and Roscosmos.
Ten days ago, in a highly dramatic moment in orbit, NASA instructed its astronauts aboard the International Space Station to temporarily take emergency shelter inside a Crew Dragon spacecraft.
Since that event, neither the U.S. space agency nor Roscosmos has released further public details about the orbital situation. However, sources who spoke with Ars indicate that the problem has been successfully resolved following the incident in space.
The core issue involved ongoing cracks in a small section of the International Space Station attached to the Russian Zvezda service module, referred to as the PrK module. This problem has existed since 2019, and Russian cosmonauts have been trying various repairs, frequently employing a sealant called Germetall-1.
The leaks worsen
These repair attempts finally seemed to show results early this year, when Roscosmos reported that the leaks had stabilized. However, they resumed in May and intensified in early June. This led Roscosmos to begin preparations for a more thorough inspection and structural repair effort on the morning of Friday, June 5.
A brief statement from Roscosmos provided no further details. But the solution proposed by Russian officials on June 5 alarmed NASA officials, prompting them to take the extreme measure of securing their astronauts inside Dragon in case of a depressurization event on the station. Later, Russia withdrew its plan, citing the need for additional measurements and inspections of the leak areas.
“NASA strongly supported that decision, and as a result, following that decision, Crew-12 and Williams ended their safe haven activities and returned to normal operations aboard the orbiting laboratory,” the space agency stated.
Since then, no official updates have been provided. To gain insight into what actually occurred, Ars spoke with two NASA officials on condition of anonymity.
So what really happened?
The PrK module connects the main area of the Russian segment of the space station to a docking port. Russian cosmonauts must pressurize the tunnel to access the Progress spacecraft that dock there and to unload and stow cargo on the vehicles. The cracking problem in the PrK module’s structure stems from corrosion, and leaks occur inside the aging transfer tunnel when pressure is cycled up or down.
Although NASA has not publicly detailed the severity of its concerns about the issue—likely out of respect for its Russian counterpart—the PrK module could break apart with little warning. Under pressure, the module could unzip and fail completely. Former astronaut and retired NASA official Bob Cabana described the situation in late 2024, stating, “NASA has expressed concerns about the structural integrity of the PrK and the possibility of a catastrophic failure.”
This has been a persistent, behind-the-scenes disagreement between NASA and Russian officials for years. Russia claims it has the situation under control, but leak rates on the space station suggest otherwise. The new cracks discovered in early June brought the total to approximately 16.
As leak rates increased, Russian officials informed NASA on Thursday, June 4, of plans to attempt physical repairs to the new leaks using a drill and a “drill stop” device to prevent drilling completely through the module’s structure. NASA officials were deeply worried about this because Roscosmos had not provided them with an analysis of the problem or explained why their procedures to address the leaks would be effective.
“We threatened we would put astronauts in suits, in Dragon, to send a message to world that we disagreed,” one NASA official told Ars. “They didn’t care.”
Reaching a resolution
The standoff continued into Friday morning, when Russian cosmonauts appeared to back off their plans, only to later approach the PrK module with a saw and the intention of removing a load-bearing bracket. Meanwhile, Roscosmos officials continued to ignore communication with NASA officials on the ground.
At that point, NASA directed Crew 12—U.S. astronauts Jessica Meir and Jack Hathaway, French astronaut Sophie Adenot, and Russian cosmonaut Andrey Fedyaev—into SpaceX’s Crew Dragon Freedom spacecraft, along with U.S. astronaut Chris Williams, who had traveled to the station in a Russian Soyuz spacecraft.
“We felt there was a very high probability of a bad outcome happening if they sawed that bracket off,” a NASA source said. NASA’s decision to send its astronauts into a safe haven finally prompted Roscosmos to back off.
In the days since, there has been some additional back-and-forth, but Russia has now told NASA it will decommission the PrK module.
Effectively, this means cosmonauts will no longer enter the PrK module or attempt to pressurize it. Progress vehicles will still be able to use the docking port to transfer fluids or perform other functions, but Russia will need to use other ports to move supplies on board the space station.
For NASA and the space station’s longevity, this agreement with Russia represents a significant step forward. For years, NASA has reluctantly accepted the risk of a rapid depressurization event on board the space station due to the PrK module’s issues. Now that risk should be retired.