Astronauts remove failed cooling pump in ISS spacewalk
"Work has gone extremely well"
Astronauts from the International Space Station have removed a failed ammonia pump from the outside of the orbiting spaceship during a second spacewalk to fix the station’s cooling system.
“The work has gone extremely well,” Nasa said after astronauts Doug Wheelock and Tracy Caldwell Dyson wrapped up work on the exterior of the ISS, some 350 kilometres above the earth.
“It was a textbook space walk for Wheelock and Dyson,” the US space agency said.
On Saturday, the pair tried without success to wrest the faulty pump module from the outside of the station during an eight-hour walk that was the longest in ISS history, and the sixth longest ever.
The astronauts successfully disconnected three of four fluid lines connected to the pump but a fourth line leaked, forcing them to stop work, Nasa said.
The pump, which failed unexpectedly on July 31, will be replaced with a spare pump module during a third spacewalk scheduled for “no earlier than Sunday”, Nasa said.
Conditions on the ISS remained stable and the station’s six-person crew – three Americans and three Russians – was not in danger, Nasa officials said.
Astronauts switched to a back-up cooling system and the ship’s crew transferred batches of experiment samples to a different freezer to preserve them, Nasa said.
If the second of the two ISS cooling units fails – a highly unlikely scenario, according to Nasa – then the ISS astronauts would no longer be able to cool most of space station components.
But the crew would not be in danger because they could move to the Russian segment of the ISS, which has its own cooling system.
According to Nasa figures, without thermal controls the ISS’s sun-facing side would roast at 121°C, while the outpost’s dark side would plunge to some -157 °C.
The ISS, a $100 billion project involving 15 countries, is a sophisticated platform for scientific experiments. It has been manned continuously since October 1990.