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Pesky ISS cooling pump: NASA has a plan

Isolate ammonia, unbolt unit, beers all round

NASA reckons it's nailed a way to safely disconnect the failed ammonia cooling system pump which on Saturday refused to play ball with spacewalkers Tracy Caldwell Dyson and Doug Wheelock.

The pair were tasked with removing the clapped-out unit and slotting in a replacement. However, "due to a leak in the fourth of four ammonia line connectors hooked up to the old pump", this had to be deferred to two further EVAs.

The first of those is scheduled for tomorrow. NASA explains: "The plan would call for Wheelock and Caldwell Dyson to close other quick disconnect lines where the S1 and S0 trusses meet that will isolate ammonia upstream in the system from the final connector, preventing any recurrence of leakage while the new pump module is being installed.

"Additional work to configure lines and valves would be conducted by the spacewalkers prior to the final electrical demating of the old pump so it can be parked on a stowage bracket on the station’s Mobile Base System."

That done, the two astronauts will prep the replacement pump for "its removal from a stowage platform adjacent to the Quest airlock and its installation on the truss during a third spacewalk targeted for no earlier than next Sunday".

NASA has the latest from the ISS here, and more details of the cooling unit failure here. ®

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