Two US astronauts spent nearly eight hours spacewalking outside the International Space Station on Friday, grappling with an escape of potentially hazardous ammonia as they switched out a cooling system, NASA said. Station commander Scott Kelly and flight engineer Kjell Lindgren left the station's airlock around 6:30 am EST (1030 GMT) for what turned out to be a spacewalk lasting nearly eight hours.
A few flakes of ammonia escaped when the cooling system was being recharged, but posed no threat to the astronauts and required no decontamination before they returned to the station, said NASA mission commentator Rob Navias. Kelly and Lindgren disconnected a spare cooling system which had been used since 2012 to circumvent an ammonia leak in one of the station's eight primary cooling loops. The leak persisted, and in May 2013 another pair of astronauts replaced a faulty pump, fixing the problem.
During Friday's spacewalk, the primary cooling system was recharged with ammonia and put back into service. NASA had hoped to pack away the spare, but Kelly and Lindgren ran out of time to fold and cover its extended radiator panels. NASA spokesman Dan Huot said that work likely would be rescheduled for a future spacewalk. No more space walks are scheduled for 2015. NASA had to scrap plans this year to outfit the station with two new parking spots for commercial space taxis under development by Boeing and privately owned Space Exploration Technologies, known as SpaceX.
The first docking adapter was destroyed during a botched SpaceX cargo run in June. A second adapter is now due to fly aboard another SpaceX Dragon cargo capsule next year. Spacewalks to continue preparing the station for the new spaceships are expected to resume as early as January, Huot said.