The International Space Station (ISS), in Earth orbit at hundreds of kilometers altitude, is not perfectly airtight. Every day, the cabin loses a minute how much air, carefully controlled so that a viable atmospheric pressure can be maintained, and to identify leaks.
Now the last one just happened, just two years after the last leak. The rate of air loss at the station has risen above a level that can be explained by the normal ISS day-to-day, according to a NASA blog post.
Mission control first experienced some annoyance in September of 2019, but the increase in air leakage was slight – not enough to raise serious concerns. Now that rate has increased, so they bend in to find out where the extra air is escaping.
The current ISS crew is no danger, but NASA astronaut Commander Chris Cassidy and Roscosmos cosmonauts Ivan Vagner and Anatoly Ivanishin will have to hole up in the Zvezda Service Module this weekend, while mission control seeks out the source of the leak.
“All of the space station space will be closed this weekend so that mission controllers can carefully monitor the air pressure in each module,” wrote Mark Garcia of NASA. “The test presents no safety concerns to the crew. The test must determine which module has a higher than normal leakage rate.”
The last leak on the ISS took place two years ago, identified by ground control at 23:00 UTC (19:00 EDT) on August 29, 2018. At that time, the same measures were taken – the crew moved to the Russian segment, and the space station modules were shut down and their atmospheric pressure examined.
This procedure limited the leak to the Soyuz MS-09 spacecraft, which at the time was temporarily attached to the Rassvet module of the ISS. It was moved to a small hole of two millimeters with drill tracks next to it, leading to speculation that it was caused by a manufacturing error. But although Roscosmos has closed his investigation, the source of the hole is not disclosed.
An earlier leak was identified and patched in 2004, in a vacuum jumper cable used to simulate the air pressure across a window in the Destiny laboratory module.
Detecting such leaks can be challenging due to the normal air pressure fluctuations in the space station. In addition to the normal leak rate, the pressure also changes due to temperature fluctuations, as well as routine station operations, such as space weeks and the arrival and departure of space travel for newer supply.
During their weekend in the Zvezda module, the ISS crew will continue their normal duties as much as they can. Once the leak is detected to a specific module, the crew will be able to perform a more granular search to find the exact source.
“U.S. and Russian specialists expect preliminary results to be available for review by the end of next week,” Garcia wrote.
.
