Russia's ISS Module Zvezda suddenly stopped leaking

After half a decade of leaking, a small section attached to Russia's Zvezda service module on the International Space Station has apparently stopped leaking. 

The leaks were caused by microscopic structural cracks inside the small PrK module on the Russian segment of the space station, which lies between a Progress spacecraft airlock and the Zvezda module. The problem has been a long-running worry for Russian and US operators of the station, especially after the rate of leakage doubled in 2024. This prompted NASA officials to label the leak as a “high likelihood” and “high consequence” risk. 

Recently, two sources indicated that the leaks have stopped. And NASA has now confirmed this.

“Following additional inspections and sealing activities, the pressure in the transfer tunnel attached to the Zvezda Service Module of the International Space Station, known as the PrK, is holding steady in a stable configuration,” a space agency spokesman, Josh Finch, told Ars. “NASA and Roscosmos continue to monitor and investigate the previously observed cracks for any future changes that may occur.”

For five years, Russian cosmonauts have been searching for the leak like a proverbial needle in a haystack. They would periodically close the hatch leading to the PrK module and then, upon re-opening it, they'd float around the station, looking for tiny accumulations of dust to indicate the leak sites. When they found such a leak, they'd apply a sealant known as Germetall-1 (used in a leak story in 2018) to the areas, close the hatch again, monitor the pressure inside the PrK module, and begin the search anew for additional leaks. This process went on for years.

In reality, this probably doesn't mean much, with the leak having been continually monitored practically since Zvezda was first added to the station 25 years - a quarter of a century - ago, and the station being expected to be deorbited in four years. But one less thing to worry about is always better than one more thing.

The Zvezda service module, seen here near the top of this image, is one the oldest parts of the International Space Station. Image Credit: NASA

The topmost portion of the relatively long, straight line of hardware in the middle of the image is a Soyuz spacecraft, the orbital "ferry" the Russians have been flying for many years. Zvezda is the more or less cylindrical section just below Zvezda. The mention of the "small PrK module" as the precise location of the leak(s) doesn't tell me any more information on where to find it in this photograph.