On an aging space station, air leaks become routine

Anyone who’s ever owned an older car will know the feeling: the nagging worry at the back of your mind that today might be the day that something important actually stops working. Oh, it’s not the little problems that bother you: the rips in the seats, the buzz out of the rear speakers, and that slow oil leak that might have annoyed you at first, but eventually just blend into the background. So long as the car starts and can get you from point A to B, you can accept the sub-optimal performance that inevitably comes with age. Someday the day will come when you can no longer ignore the mounting issues and you’ll have to get a new vehicle, but today isn’t that day.

Looking at developments over the last few years one could argue that the International Space Station, while quite a bit more advanced and costly than the old beater parked in your driveway, is entering a similar phase of its lifecycle. The first modules of the sprawling orbital complex were launched all the way back in 1998, and had a design lifetime of just 15 years. But with no major failures and the Station’s overall condition remaining stable, both NASA and Russia’s Roscosmos space agency have agreed to several mission extensions. The current agreement will see crews living and working aboard the Station until 2030, but as recently as January, NASA and Roscosmos officials were quoted as saying a further extension isn’t out of the question.

Still, there’s no debating that the ISS isn’t in the same shape it was when construction was formally completed in 2011. A perfect case in point: the fact that the rate of air leaking out of the Russian side of the complex has recently doubled is being treated as little more than a minor annoyance, as mission planners know what the problem is and how to minimize the impact is has on Station operations.


While the leak might have been generating some additional buzz over the last week or two, this is only the latest chapter in a story that’s been unfolding for several years.

Zvezda, launched in July of 2000

You can find similar headlines popping up every year or so since at least 2019, and even back that far, it was noted that the Station was constantly losing breathable atmosphere to some degree. It’s only considered a proper “leak” when ground controllers see a notable spike in the normal amount of air being lost.

By 2020, the rate of air being lost was getting to the point that NASA and Roscosmos decided it was worth spending some time to investigate. So during a (relatively) slow operational period, with only three crew members aboard, all of the inter-module hatches were closed throughout the Station. The air pressure in each module was then carefully monitored over the next several days, an effort which ultimately determined the leak was somewhere within the Russian Zvezda module.

Once it was determined the leak was on the Russian side of the complex, cosmonauts started a more localized search. By 2021, they were watching thin strips of paper and tea leaves as they were carried by air currents within Zvezda. This allowed them to identify a few cracks in the hull where air was escaping, which were taped up to help slow the bleed.


Our latest update comes from NASA’s International Space Station Program Manager, Joel Montalbano. In a February 28th media briefing ahead of the launch of the SpaceX Crew-8 mission, Montalbano explained that the Station leak rate doubled to approximately 0.9 kilograms air per day as preparations were made to dock the Progress MS-26 cargo spacecraft to the Station.

Zvezda’s rear docking port

It was eventually determined that the leak was within the one-meter long vestibule in the rear of Zvezda known as the PrK, which acts as a sort of air lock between a visiting Progress spacecraft and the rest of the module. The leak rate only increased when the inner hatch to this chamber was open, and went back to normal as soon as it was closed. Since this hatch only needs to be open during active loading and unloading of a Progress vehicle, NASA feels confident that it presents no risk to the crew or the Station.

Even still, Montalbano did say the situation was being continuously monitored from the ground, and that Russian engineers are currently looking into locating the leak within the PrK and patching it permanently. It was also explained that, thanks to the nature of the PrK chamber, even if the leak were to become worse and found to be beyond repair, it would pose no risk to the Zvezda module. It could potentially mean permanently losing access to the docking port on the other side of the PrK however — an unfortunate, but not insurmountable, situation.