One spacewalking cosmonaut was hit on their visor by a contaminated tether as a pair of International Space Station crew members ventured outside the outpost a few hours ago to investigate a leaky radiator.

Streamed live on NASA TV, the spacewalkers had several tasks, but it was dealing with the leak earlier this month from a radiator on the Nauka module that was the highlight.

The cosmonauts, Oleg Kononenko and Nikolai Chub, were tasked with inspecting and isolating the coolant leak, which required turning the valves to cut the radiator off from the cooling system.

While frozen crystals had been observed spewing into space, the cosmonauts could initially find no sign of the leak on the connecting line. However, traces were spotted where the radiator panels were connected. Later in the spacewalk, a large blob of coolant was observed on a line at a radiator joint.

The cosmonauts brought towels to mop up the mess, but it soon became apparent they didn't have enough. One end of a tether became soaked in the stuff, and it appeared to have touched the visor of a cosmonaut.

The pair were advised to leave the area and get on with the rest of the spacewalk tasks, which did not go entirely to plan. A nanosatellite to test solar sail technology was released, but the sail failed to deploy. A synthetic radar communications system was also installed, but one of the four panels could not be fully deployed. Eventually, controllers decided to defer the work to a future date.

As far as coolant was concerned, the cosmonauts checked out their Roscosmos Orlan spacesuits for signs of contamination during the spacewalk and wiped everything down as usual after repressurization. Managers plan to use additional filtration within the ISS to scrub the air of any remaining coolant traces.

Cameras on the orbiting lab detected the leak. The crew was asked to confirm it by peering out of the windows, and saw a backup radiator on the Nauka module appeared to have sprung a leak. The radiator had been delivered by one of the final Space Shuttle missions in 2010 but only fitted during a Russian spacewalk this year.

Managers have yet to decide on the next steps. Kononenko and Chub were to find and isolate the leak, and have completed both tasks - although it's debatable if more work will be needed for the former. Repairing the leak is another thing entirely. The primary coolant loop is unaffected, and the crew is not in any danger. ®

https://www.theregister.com//2023/10/26/spacewalking_cosmonauts_find_iss_leak/