Russian spacewalkers to inspect leaking radiator

Russian cosmonauts Oleg Kononenko and Nikolai Chub work outside the International Space Station on Oct. 25, 2023. Image: NASA TV
Two Russian cosmonauts ventured outside the International Space Station Wednesday to look for the source of a leak at or near a newly installed radiator on the Nauka lab module and to isolate it from coolant lines.

They also planned to attach a small synthetic aperture radar instrument to the hull of the multi-purpose laboratory, deploy a mini satellite to test solar sail technology and, if time is available, replace an electrical connector panel.

Floating in the Russian Poisk module, veteran cosmonaut Oleg Kononenko, making his sixth spacewalk, and first-time flyer Nikolai Chub began the excursion at 1:49 p.m. EDT when they opened the side hatch to the vacuum of space.

For identification, Kononenko, call sign EV-1, is wearing an Orlan spacesuit with red stripes while Chub, EV-2, is using a suit with blue stripes. Both men are equipped with NASA helmet cameras.

The radiator in question was launched with the Russian Rassvet module aboard the space shuttle Atlantis in May 2010. The radiator and a small experiment airlock remained stored on Rassvet until earlier this year when spacewalking cosmonauts attached both to the Nauka multi-purpose laboratory module.

The radiator’s installation went normally and valves were opened to route coolant from Nauka into its unfolded panels. But on Oct. 9, flight controllers noted flakes streaming from the area of the radiator. The flakes turned out to be frozen coolant that was spewing overboard.

Kononenko and Chub planned to spend about three hours documenting the positions of coolant loop valves, adjusting them to isolate the radiator from supply lines and photographing the leak site to help engineers figure out what caused it.

It was the third coolant leak in less than a year for the Russians, starting with a massive rupture that disabled a Soyuz crew ferry ship last December. A similar leak developed on an unpiloted Progress cargo carrier earlier this year.

The presumed cause of the Soyuz leak was a micrometeoroid impact. The Russians have not addressed the possible cause of the Progress leak or the one affecting the Nauka radiator. But it seems extremely unlikely micrometeoroids could have caused three such incidents in similar systems.

In any case, shortly after the latest leak occurred the Russian space agency Roscosmos said in a post on Telegram that the lab’s primary coolant loop was not affected and “the crew and the station are not in any danger.”

Kononenko and Chub were not planning any sort of repair. Their primary objective was to find and document where the leak might have originated and to isolate the radiator from coolant supply lines to prevent any future problems.