Astronauts Take 3rd, Final Spacewalk; Valve Stuck

From ABC News:

Astronauts take 3rd, final spacewalk to finish installing tank; stuck valve threatens cooling.

A pair of spacewalking astronauts finished installing a fresh storage tank outside the International Space Station on Tuesday, but a stuck valve was threatening to jeopardize half of the cooling system.

No sooner had Rick Mastracchio hooked up the fluid valves for the new ammonia tank on the third and final spacewalk of shuttle Discovery's flight, then flight controllers encountered the valve trouble in a separate pressurizing unit.

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