Nov 21, 2024 07:00:00

Air leaks from the International Space Station for five years, cause unknown; US and Russia disagree on risk

The transfer tunnel called 'PrK' that connects the docking port where the crew of

the Soyuz spacecraft and the Progress resupply ship access the station in the Russian-made Zvezda Service Module, one of the modules that make up the International Space Station (ISS), has been leaking air since September 2019. Former astronaut Bob Cabana, who became the new chairman of NASA's International Space Station Advisory Committee, said, 'The United States and Russia do not have a common understanding of the root cause of this air leak or the seriousness of its consequences,' revealing that the cause is still unknown and that it is difficult to deal with it.

NASA and Roscosmos disagree on cause and severity of ISS air leak - SpaceNews
https://spacenews.com/nasa-and-roscosmos-disagree-on-cause-and-severity-of-iss-air-leak/

The ISS has been leaking air for 5 years, and engineers still don't know why - Ars Technica
https://arstechnica.com/space/2024/11/nasa-roscosmos-disagree-on-risk-of-catastrophic-failure-from-iss-air-leak/

On November 13, 2024, NASA's ISS Advisory Committee met to discuss in detail the contents of a meeting with their Russian counterparts in Moscow in September of that year. The main concern discussed was the air leak in the Zvezda Service Module PrK, which had previously been determined to have 'no immediate impact on crew safety or ISS operations,' but which has been ongoing for five years with no known cause.

Below is an image of the Zvezda Service Module by JAXA. On the side closest to Zarya is the 'transfer compartment,' a 'working area' with connections and equipment for the astronauts, and on the opposite side is the 'transfer chamber' with the docking port containing the PrK.

A report released by NASA's Office of Inspector General (OIG) in September 2024 stated that 'while no leaks were found anywhere else on the space station, both agencies focused on internal and external welds as the source of the leak.' According to the OIG, since it was first detected in 2019, the air leak reached a record high of 1.7 kg per day in early 2024. Subsequent repair work has curbed the air leak, but 600 g of air continues to leak per day.

According to Kavanagh, Russian engineers believe that the PrK leak is due to 'high cycle fatigue' caused by micro-vibrations, while NASA believes that multiple factors may be involved, including pressure, mechanical stress, residual stresses that often occur during the manufacturing process of metal parts, the material properties of the module, and its exposure to the environment. The two agencies disagree on this point.

According to Kavanagh, Roscosmos, the Russian space agency in charge of space development, and NASA do not agree on the cause of the leak, nor on the severity of the problem. Kavanagh said, 'NASA has expressed concerns about the structural integrity of PrK and the possibility of a catastrophic failure. While the Russian team continues to search for and seal the leak, they do not believe that a catastrophic collapse of PrK is realistic. Russia believes it is safe to continue operations, but has not been able to prove that to our satisfaction. Meanwhile, the United States believes PrK is unsafe, but has not been able to prove that to Russia's satisfaction.'

NASA astronaut Michael Barratt, who returned from the space station in October 2024, said of the work on PrK, 'While our Russian colleagues are optimistic about this issue, NASA took precautions while our astronauts were working on PrK. We have taken a very conservative approach to bridging the differences in U.S. and Russian views throughout this period. It's not comfortable, but it's the best agreement that has been reached between the U.S. and Russian sides, and it's something that we as a crew will accept and adapt to.'