Two Russian cosmonauts ventured outside the International Space Station today (Dec. 11) to cut into a spacecraft and inspect the source of a pressurization leak that briefly plagued the outpost earlier this year.
Expedition 57 flight engineers Oleg Kononenko and Sergey Prokopyev of the Russian federal space agency Roscosmos conducted the 7-hour and 45-minute spacewalk. The two cosmonauts worked on the exterior of the Russian Soyuz MS-09 spacecraft, where the space station’s crew had earlier found and repaired the leak from the inside.
On Aug. 29, flight controllers monitoring the space station’s systems from the ground first noticed a small loss of cabin pressure aboard the orbiting laboratory. The then-Expedition 56 crew, including Prokopyev, Alexander Gerst of the European Space Agency (ESA) and Serena Auñón-Chancellor of NASA, were able to trace the leak back to a 0.1-inch (2 millimeters) hole in the orbital compartment of the Soyuz MS-09 spacecraft, which was docked to the Rassvet module on the Russian segment of the space station. [Russia's Crewed Soyuz Space Capsule Explained (Infographic)]
After consulting with both Russian and U.S. flight controllers, Prokopyev applied an epoxy to a gauze wipe and used it to plug the hole. The repair halted the leak, and the space station has since maintained a steady pressure.
Today, Prokopyev joined Kononenko on a spacewalk to inspect the repair area from the outside in an effort to discover what caused the leak and to collect a sample of the epoxy that had extruded through the hole from the inside.
To reach the area needed to perform the inspection, Kononenko rode at the end of two Russian Strela booms, translating from the Pirs docking compartment where the spacewalk began to the Zarya functional cargo block (FGB) and then up alongside the Soyuz. Prokopyev controlled the booms’ motion from the opposite end, moving Kononenko into place, before shimmying up the second boom himself.
At the worksite, Kononenko and Prokopyev took turns using a knife and a pair of long-arm scissors to stab at and cut away layers of brown, gold and silvery insulation. As they cut into the spacecraft, small fragments of the material floated away and formed a cloud of debris.
The two cosmonauts then used the same tools to cut into and peel away a thin metal orbital debris shield to expose the hole in the Soyuz MS-09’s orbital compartment.
"That is exactly the hole we’ve been looking for," reported Kononenko after peeling back more of the foil insulation and metal layers that were hiding it.
The hole appeared as a black mark or spot on the exposed metal skin of the Soyuz spacecraft.
Kononenko used a pair of forceps and a swab to collect samples of the dark epoxy. The residue, stowed inside a bag, was brought back inside the space station and will be returned to Earth for analysis.
With the spacewalk running long on time, flight controllers decided to forgo having Kononenko and Prokopyev install a replacement insulation blanket over the spacecraft’s exposed skin. The orbital compartment on which they worked is purposely jettisoned and destroyed during the re-entry of the Soyuz descent module into Earth’s atmosphere.
Tuesday’s spacewalk began at 10:59 a.m. EST (1559 GMT) and ended at 6:44 p.m. EST (2344 GMT) when the hatch to the Pirs docking compartment was closed. The extravehicular activity (EVA) was the 213th spacewalk in support of assembly and maintenance in the 20-year history of the space station.
This was Kononenko’s fourth EVA and Prokopyev’s second. Kononenko has now logged a total of 26 hours and 12 minutes working in the vacuum of space, including a 2008 spacewalk when he performed similar work to what he did on today, cutting into the insulation covering the Soyuz TMA-12 spacecraft to remove a pyrotechnic device. Prokopyev now has spent 15 hours and 31 minutes on EVA.
Prokopyev, Gerst and Auñón-Chancellor are scheduled to return to Earth aboard Soyuz MS-09 on Dec. 19 after 6.5 months aboard the space station.
Kononenko, together with NASA astronaut Anne McClain and David Saint-Jacques of the Canadian Space Agency, will remain aboard the space station as Expedition 58 crewmembers through June. An additional three crew members, including Roscosmos cosmonaut Aleksey Ovchinin and NASA astronauts Nick Hague and Christina Hammock-Koch, are slated to launch to the station on Feb. 28.
Robert Pearlman is a Space.com contributing writer and the editor of collectSPACE.com, a Space.com partner site and the leading space history news publication. Follow collectSPACE on Facebook and on Twitter at @collectSPACE. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.