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  • Fourth Discovery Spacewalk Unnecessary
    Posted by Mark Carreau 6:38 AM on Apr 15, 2010

    Discovery's astronauts will not be assigned an unplanned fourth spacewalk to replace a jammed external thermal control system valve on the International Space Station, NASA mission management team concluded early Thursday.The station's thermal control system can safely accommodate high as well as low temperature swings associated with a period of high beta solar angle exposure that will begin in late April, Mission Control informed Discovery commander Alan Poindexter as the astronauts were awakened. The stuck nitrogen valve was discovered early Tuesday as Discovery spacewalkers Rick Mastracchio and Clay Anderson neared the end of a third spacewalk for the installation of a new ammonia coolant tank on the station's right side truss. A separate but linked nitrogen tank assembly with the stuck valve provides the pressure to circulate ammonia through outstretched radiators to dissipate heat generated by the station’s internal electronics, including the life support systems.

    The thermal control system can function for at least a month with the jammed valve, flight controllers told the station's six U. S., Russian and Japanese astronauts. They could be asked to conduct a spacewalk to install a spare nitrogen tank assembly with a new valve, or the task could be assigned to the crew of the shuttle Atlantis, which is tentatively scheduled to lift off for the station on May 14 with a Russian mini research module.

    The latest analysis means Discovery's seven astronauts can proceed with plans to end their 14-day re-supply mission with a landing at the Kennedy Space Center on Monday, shortly before 9 a.m., EDT.

    Tags: os99, Discovery, shuttle, ISS

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