Two spacewalking astronauts finally removed a faulty pump outside the International Space Station Wednesday after overcoming a stubborn ammonia hose during their second attempt in less than a week to repair the outpost’s cooling system.
It came down to brute strength in the end for NASA astronauts Douglas Wheelock and Tracy Caldwell Dyson to remove the balky ammonia hose, which had stuck fast and leaked toxic ammonia coolant during an earlier spacewalk.
“This will allow us to get our station back,” Wheelock said. “Back in action.”
Wheelock had to shake a hose connector hard to pry it free from the broken pump that his helmet camera showed him swaying from side-to-side. But ultimately he disconnected the hose to the delight of the astronauts and Mission Control. He saw only a few flakes of ammonia while detaching the pump’s final fluid hose Wednesday, far less than the snowstorm of frozen ammonia he reported seeing during the Saturday spacewalk.
The astronauts parked the broken pump at a storage point outside the space station after removing it. NASA plans one more spacewalk, currently scheduled for no earlier than Monday, to complete the ammonia pump repair.
“We still have a little ways to go, but today was a great day,” Wheelock radioed Mission Control after the spacewalk, which lasted seven hours and 26 minutes.
The International Space Station uses liquid ammonia to cool its onboard systems by transporting waste heat to a network of radiators mounted to its main truss. Spacewalking astronauts take care to avoid exposure to ammonia (which freezes into flakes when it leaks) while working outside and have lengthy decontamination protocols to clean their spacesuits when they do see leaks in order to avoid bringing the toxic chemical inside.
The faulty ammonia pump failed July 31, forcing astronauts to turn off some experiments and systems, as well as leave others without backups, in order to prevent the station from overheating. An internal electrical short tripped a circuit breaker to cause the malfunction, station managers have said.