Spaceflight Insider

How was the exact location of the recent ISS air leak found?

An air leak was discovered on the International Space Station on Aug. 29, 2018. This resulted in the ISS crew working to find and seal its origin. Photo Credit: NASA

An air leak was discovered on the International Space Station on Aug. 29, 2018. This resulted in the ISS crew working to find and seal its origin. Photo Credit: NASA

The Aug. 29, 2018, discovery of an air leak at the International Space Station raised some troubling questions about how the U.S. travels to and from the outpost. However, one question doesn’t appear to have received a lot of attention—how did the astronauts figure out where the leak was originating from?

The two-millimeter-wide hole was found on the orbital module of the Soyuz MS-09 spacecraft. Credit: NASA

The two-millimeter-wide hole was found on the orbital module of the Soyuz MS-09 spacecraft. Photo Credit: NASA

The ISS is a very large spacecraft. Measuring some 358 feet (109 meters) by about 240 feet (73 meters), the station is roughly the size of an American football field. So how do astronauts aboard the outpost find the source of an air leak, especially one as minor as the one that originated from the Soyuz MS-09 spacecraft in late August 2018?

“From what I understand, the ground determined there was a leak and pointed the crew in the right direction,” said Nicole Stott, a former NASA astronaut and SpaceFlight Insider technical consultant.

Keep in mind that the ISS is comprised of a series of interconnected modules from the U.S., Russia, Europe and Japan. On top of that, there can also be spacecraft from different countries connected to the station. How did the astronauts hone in on where this leak was coming from?

First, according to NASA, ground-based flight controllers noticed the cabin pressure was off nominal. However, it wasn’t that severe and it was decided to allow the Expedition 56 crew members to continue their sleep cycle. 

Once they were awake, they were told to seal off various sections of the orbiting lab to narrow down where the leak was coming from.

There is nothing particularly complicated about this. Hatches were closed and the astronauts and ground controllers watched to see which side maintained pressure and which didn’t.

Soyuz MS-09, left, is docked to the Rassvet module. The leak is originating from the upper section of the spacecraft. Photo Credit: NASA

Soyuz MS-09, left, is docked to the Rassvet module. The leak is originating from the upper section of the spacecraft. Photo Credit: NASA

“First close hatch between segments. [This] lets you know which segment [is] leaking (Russian or U.S.),” retired NASA astronaut Clay Anderson told SpaceFlight Insider.

Anderson, who spent five months living aboard the outpost in 2007, said that once it was determined the leak was in the Russian segment, those hatches were methodically closed and the pressure on each side checked. He said each time a module or area was closed off, the astronauts had to make sure their particular Soyuz (which is their ride back to Earth) was on their side of the hatch so they don’t accidentally isolate themselves in case of a problem.

The astronauts would keep “reducing the size of station” with hatch closures until the Soyuz was isolated as the leaker, Anderson said.

After astronauts determined from which of the modules the leak is coming from, in this case the upper section of the Soyuz MS-09 spacecraft, they used a device called an ultrasonic leak detector (ULD) to find the precise location of the Soyuz spacecraft that was leaking atmosphere.

An example of a ULD being used on the International Space Station. This video is not from the Aug. 29, 2018, event.

Video courtesy of Measuretronix

 

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Jason Rhian spent several years honing his skills with internships at NASA, the National Space Society and other organizations. He has provided content for outlets such as: Aviation Week & Space Technology, Space.com, The Mars Society and Universe Today.

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