MIAMI: Two US astronauts stepped out on a risky spacewalk on Friday to complete the repair of an ammonia cooling system at the International Space Station.

Highly toxic ammonia is used to cool electronics at the orbiting outpost, and the thermal system has been plagued by problems.

Friday’s outing aims to complete the final repairs to a system that broke down about three years ago.

Scott Kelly and Kjell Lindgren switched their spacesuits to battery power at 6:22 am and floated outside the orbiting outpost moments later, according to a live broadcast on Nasa television.

The goal for Friday’s 6.5 hour spacewalk is to “restore the port truss ammonia cooling system to its original configuration,” the space agency said in a statement. In 2012, Nasa detected a major leak in the ammonia cooling system.

Astronauts replaced the ammonia pump on the station’s truss in May 2013.

The spacewalkers reported seeing some flakes of ammonia when disconnecting some of the equipment, but the crew was in no danger, said Nasa commentator Rob Navias.

Published in Dawn, November 7th, 2015

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