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Cutting into Soyuz cover
Russian cosmonaut Oleg Kononenko uses a cutting tool to open up the Soyuz spacecraft’s external cover, at bottom, while crewmate Sergey Prokopyev looks on. (NASA TV via YouTube)

During an extraordinary spacewalk, two Russian cosmonauts used sharp objects today to cut away layers of protective insulation on a Soyuz capsule and take samples of sealant plugging up a mysterious drill hole.

The hole, measuring just a tenth of an inch wide, was the source of an alarming air leak detected on the International Space Station in August. Soon after discovering the breach, the station’s crew managed to plug the hole in the Soyuz’s habitation module with epoxy and gauze, and the Soyuz has since been judged safe for next week’s return trip to Earth.

Three returning spacefliers will take their seats in a separate area of the Soyuz spacecraft, the descent module, and the habitation module will be jettisoned as usual before atmospheric re-entry.

Russian mission planners scheduled today’s spacewalk to gather evidence from the Soyuz’s exterior, in order to track down the cause of the breach and to determine the best way to make such repairs in the future.

During a seven-hour, 45-minute outing, spacewalkers Oleg Kononenko and Sergey Prokopyev made their way from the station’s Pirs docking compartment to the side of the Soyuz with the aid of a Russian-made inspection boom.

They used a knife, a scissors and another tool that looked like a tree trimmer to cut through the Soyuz’s external covering, layers of fluffy insulation and a debris shield. Bits of insulation floated harmlessly into space as the cosmonauts carved away.

“Oleg, be careful. … please, try to be calm,” Russian Mission Control said.

Several hours into the spacewalk, the Soyuz’s shiny metal hull was finally exposed, with an irregular-shaped squirt of dark sealant sticking up from the surface.

“That is exactly the hole we’ve been looking for, guys,” Mission Control told the pair.

The cosmonauts took pictures of the hull and carefully sampled the plug for later inspection, leaving behind a ragged wound in the Soyuz’s insulation layers They also retrieved science experiments from the exterior of the station’s Rassvet module before heading back inside.

Samples and other evidence are due to be brought back to Earth on Dec. 19 with the Soyuz crew, which consists of Prokopyev plus NASA’s Serena Auñón-Chancellor and Germany’s Alexander Gerst.

For a time, there were Russian rumors that the hole was drilled through the hull as a deliberate act of sabotage, but space officials managed to tamp down the conspiracy theories. The investigation is continuing, but the current leading hypothesis is that a worker drilled the hole by accident and then plugged it with sealant. This scenario would suggest that the plug came loose during flight, resulting in the leak.

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