The high-stakes marathon of repairing a cooling system in orbit

Space · Published 14 October 2026 Swipe more like this →

In short: When an ammonia leak threatens the International Space Station's power systems, astronauts must perform a grueling six-hour manual repair in the vacuum of space. This 2012 mission highlights the delicate balance between maintaining complex orbital infrastructure and the constant threat of micrometeorite damage.

On November 1, 2012, NASA astronaut Suni Williams and Japanese spaceflyer Akihiko Hoshide conducted a marathon extra-vehicular activity (EVA) to address a persistent ammonia leak. The leak was first identified by international partners in 2007. Because the station's eight large solar panels rely on circulating ammonia to cool their power systems, an unaddressed leak posed a risk to critical power channels.

The repair required the astronauts to navigate to the port side of the station’s truss backbone to reconfigure coolant lines and deploy a spare radiator. NASA officials suspected the source of the leak was an older, swapped-out radiator that extended outward, making it particularly vulnerable to impacts from micrometeorites—tiny particles traveling at high speeds that can puncture orbital structures.

The mission was a significant milestone for both explorers: Williams reached her fifth cumulative spacewalk and set a record for total time by a female astronaut (50 hours and 40 minutes), while Hoshide set the record for total cumulative spacewalking time by a Japan Aerospace Exploration Agency astronaut (21 hours and 23 minutes). Despite the complexity, the team completed their primary objectives on schedule, though officials noted that because the leak is so slow, it would take several weeks to confirm if the fix was successful.

This repair underscores the ongoing maintenance reality of long-term space habitation. While the immediate goal was isolating the ammonia, the operation serves as a reminder of the 'waiting game' involved in orbital engineering, where repairs are often verified over months rather than minutes.

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