Ground controllers noticed a slight dip in ISS cabin pressure on Wednesday night (Aug. 29). Yesterday, crewmembers traced the leak to a 2-millimeter-wide hole in one of the two Russian Soyuz spacecraft that's currently docked to the orbiting lab.
Cosmonaut Sergey Prokopyev, the Soyuz commander, patched the hole with epoxy yesterday, and this on-orbit fix is still holding: Cabin pressure remains steady, NASA officials wrote in an update today (Aug. 31). Flight controllers in Moscow and at NASA's Johnson Space Center in Houston continue to monitor pressure levels, NASA added.
"Yesterday showed again how valuable our emergency training is. We could locate and stop a small leak in our Soyuz, thanks to great cooperation between the crew and control centres on several continents," ISS crewmember Alexander Gerst, a European Space Agency astronaut, said via Twitter today.
Yesterday showed again how valuable our emergency training is. We could locate and stop a small leak in our Soyuz, thanks to great cooperation between the crew and control centres on several continents. pic.twitter.com/Jo0MnIIprL— Alexander Gerst (@Astro_Alex) August 31, 2018
Russian space officials have said that the puncture was caused by a micrometeoroid, but NASA has not confirmed this.
Soyuz spacecraft have been crewmembers' only ride to and from the ISS since NASA grounded its space shuttle fleet in 2011. (This situation should change soon, however; private astronaut taxis built by SpaceX and Boeing are scheduled to start crewed flights next year.)
The hole was found in the orbital module of Soyuz MS-09, which arrived at the ISS in June. The orbital module is the spherical upper compartment of the Soyuz, and it provides extra room for cargo and crew while the spacecraft is aloft. The module does not survive the trip home to Earth, burning up by design during re-entry into the planet's atmosphere.
ISS crewmembers were never in any serious danger as a result of the recent leak, NASA officials have said.