US Astronauts Set for Key ISS Repair Spacewalk

Two International Space Station astronauts were prepared Saturday to set out on the first of two spacewalks to fix a cooling pump that dramatically failed last week.

Photo: US Astronauts Set for Key ISS Repair Spacewalk

ISS astronauts will need at least two spacewalks to remove the failed ammonia pump unit and replace it with a new one after the device failed Saturday, according to AFP reports.

The seven-hour spacewalk, or extra-vehicular activity (EVA), will begin at 6:55 a.m. ET on Saturday, followed by a second spacewalk Wednesday.

Repairs will be conducted by U.S. astronauts Douglas Wheelock and Tracy Caldwell Dyson, who are among the six astronauts currently living aboard the ISS as part of Expedition 24.

Over the course of both spacewalks, the pair will swap out a broken 780-pound (354-kilogram) ammonia pump with one of four spares stored on the space station's exterior. They'll also disconnect, then reconnect, the electrical and ammonia lines running between the pump and the station.

Astronauts on Earth are currently practicing the swap in a huge swimming pool at Johnson Space Center in Houston called the Neutral Buoyancy Lab, National Geographic reports.