Cosmonauts Fyodor Yurchikhin and Alexander Misurkin prepared the International Space Station’s Russian segment for the arrival of the Nauka Multipurpose Laboratory Module during a spacewalk Monday.

Russia’s Nauka science compartment is scheduled for launching in December.

Spacewalker Alexander Misurkin outside International Space Station. Photo Credit/NASA TV

Monday’s spacewalk eclipsed the scheduled six hours, as Yurchikhin and Misurkin struggled with fatigue from the many hand intensive activities. It was the third spacewalk by space station crews this year. Four more NASA and Russian excursions are planned for July and August to finish the preparations for Nauka, address external maintenance tasks and carry out science experiments.

The station’s Russian Pirs airlock must be jettisoned to clear a docking port for the large new Russian lab compartment and some of the activities will involve salvaging equipment from the module before it departs.

The two cosmonauts began Monday’s space walk by assisting Russian flight controllers with tests of the KURS automated docking system hardware that will permit the unpiloted Nauka to rendezvous and berth once it’s launched.

While the flight controllers conducted the assessments, the spacewalkers replaced an aging cooling system valve and installed clamps for power and data cables that will be extended across the outside of the station’s Russian segment for Nauka. The cables will be deployed during the upcoming spacewalks.

“KURS test successful,” Russian flight controllers informed the grateful Yurchikhin and Misurkin as they moved on to other tasks.

The spacewalkers installed Indicator, a Russian experiment that will assess the space environment around the station. They retrieved a materials exposure experiment and cleared a space for a future telescope observatory.