Two Russian cosmonauts aboard the International Space Station (ISS) completed a high-stakes spacewalk on Thursday, successfully locating and addressing the source of a coolant leak that had threatened the station's thermal control system.

Cosmonauts Oleg Artemyev and Denis Matveev, facing a potentially critical situation, spent over seven hours outside the station's pressurized modules, maneuvering in the unforgiving vacuum of space to repair the damaged radiator.

The leak, discovered earlier in the week, originated in a section of the Soyuz MS-22 spacecraft's radiator.

Initial concerns centered around the possibility of a micrometeoroid impact, but the precise nature of the damage remained unclear until the spacewalk.

Live video feeds showed Artemyev and Matveev meticulously inspecting the radiator's intricate network of tubes, carefully documenting the extent of the damage before implementing a repair strategy.

Their primary objective was not to fully repair the radiator itself – a task beyond the scope of the extravehicular activity (EVA) – but to pinpoint the precise location of the leak and implement a temporary fix to mitigate further coolant loss.

This involved carefully deploying a specialized thermal cover, designed to insulate the damaged section and prevent the escape of the vital coolant needed to regulate the temperature inside the station.

The process, demanding both precision and dexterity in the challenging space environment, was closely monitored by mission control in Moscow.

The success of the spacewalk represents a significant triumph for the Russian space program.

The potential consequences of a catastrophic coolant leak were severe, threatening the habitability of the ISS and potentially jeopardizing ongoing scientific research.

While the temporary fix buys time, further repairs or replacements will likely be necessary during subsequent missions.

The precise cause of the radiator damage remains under investigation, with a thorough post-spacewalk analysis planned to determine whether micrometeoroid impact, manufacturing defect, or another factor was responsible.

The bravery and expertise of Artemyev and Matveev averted a potentially disastrous scenario, showcasing the critical role of human spaceflight in maintaining the operational integrity of the International Space Station.

Two Russian spacewalkers floated outside the International Space Station Wednesday and isolated a leaking radiator as planned, apparently causing residual coolant still trapped inside to make its way to the leak site and spew out into space.

Cosmonaut Oleg Kononenko planned to sop up the pooling coolant with a cloth towel, but was told to leave the area immediately when he reported some of the liquid had made it onto a safety tether. He said none had reached his suit.

The tether was secured in a bag and procedures were already in place to make sure the cosmonauts' spacesuits were clear of any such contamination before they re-entered the space station at the end of the spacewalk.

In the meantime, Kononenko and crewmate Nikolai Chub pressed ahead with work to attach a small synthetic aperture radar antenna to the hull of the Nauka module. One of its four panels failed to fully deploy and lock in place, and officials said adjustments would be made in a future spacewalk.

Finally, Kononenko and Chub released a small student-built "nanosatellite," but the solar sail propulsion system it was designed to test failed to deploy. After making a final attempt to coax the radar panel into place, the cosmonauts called it a day.

Kononenko, making his sixth spacewalk, and Chub, making his first, began the excursion at 1:49 p.m. EDT when they opened the side hatch of the Poisk airlock compartment to the vacuum of space.

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 Nakua 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, streaming from the area of the radiator. The flakes turned out to be frozen coolant that was spewing overboard.

Kononenko and Chub checked and reset 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.

Kononenko initially reported "the radiator is clean. I don't see anything ... I do not see any traces of coolant."

But he reported numerous "black spots" on one radiator panel and after the valves used to isolate the radiator from its coolant lines were adjusted, droplets of coolant could be seen leaking from a line connecting two radiator panels.

The droplets combined to form a fairly large bubble around the leaking coolant line. Kononenko said the bubble was too large to sop up with the towel he had planned to use. Instead, the cosmonauts simply left it as is while engineers on the ground began considering possible courses of action.

What might have ruptured the coolant line in the first place was not immediately known.

It was the third coolant leak in less than a year for the Russians, starting with a massive rupture that last December. A similar leak developed on an 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, 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.