CAPE CANAVERAL — Astronauts ventured out Saturday on the first of a series of urgent repair spacewalks to revive a crippled cooling line at the International Space Station.
The two Americans on the crew, Rick Mastracchio and Michael Hopkins, will need to perform two and, quite possibly, three spacewalks to replace an ammonia pump containing a bad valve.
Next will be one Monday, followed by a third on Christmas Day if it's needed.
The breakdown 10 days ago left one of two identical cooling loops too cold and forced the astronauts to turn off all nonessential equipment inside the orbiting lab, bringing scientific research to a near-halt and leaving the station in a vulnerable state.