NASA Troubleshoots Space Station Cooling System Pump Shutdown

An external cooling system pump module aboard the International Space Station shut down on Wednesday, prompting a round of troubleshooting by NASA's Mission Control team and a decision to power down non critical solar powered systems in three U. S. segment modules.

NASA troubleshoots external cooling system pump module shutdown. Pump circulates ammonia

coolant.  Photo Credit/NASA 

The station's six person crew -- two Americans, a Japanese and three Russians -- were in no danger, NASA said late Wednesday, after the astronauts and cosmonauts began their normal sleep period.

The orbiting science lab is equipped with primary and backup external cooling systems integrated into the vaulting solar power truss. The system uses pumps to circulate an ammonia coolant through outstretched radiator panels to dissipate heat generated by the station's many electrical systems, including life support and science hardware.

Early analysis pointed to a faulty flow control valve in the pump module as the source of the problem, according to a space agency statement.

The pump shutdown, which may require a spacewalk to repair, emerged days before the planned Dec. 18 launch of an Orbital Sciences Corp. commercial re-supply mission to the orbital outpost. Orbital Sciences' Cygnus module and a 3,230 pound cargo  is scheduled to rendezvous with the station three days after the launch from Virginia's Mid Atlantic Regional Spaceport and remain berthed for 42 days.

At the same time, U. S. spacewalks have been on hold since July 16, when the helmet of the NASA space suit worn by Italian astronaut Luca Parmitano filled with water, forcing an abrupt end to his excursion with U. S. astronaut Chris Cassidy. Parmitano and Cassidy, who returned to Earth earlier this year, were preparing the station for the arrival of a future Russian science module.

The suit failure, which allowed cooling system water from the personal life support system backpack on Parmitano's space suit to invade an air vent at the back of his helmet, has since been repaired, though the results of an investigation have not been announced.

Although water pooled around his eyes, ears and nose, Parmitano made his way to the safety of the U. S. airlock on July 16.

Doug Wheelock during August 2010 ISS cooling 

system repairs. Photo Credit/NASA TV 

The space station faced a similar cooling system pump module failure in August of 2010. NASA astronauts Doug Wheelock and Tracy Caldwell Dyson carried out three difficult spacewalks to successfully install a spare pump stowed outside the station.

Astronaut Tracy Caldwell Dyson during August 2010

spacewalk repairs. Photo Credit/NASA TV

The latest cooling system difficulties prompted NASA to shutdown non critical systems in the Harmony node, Europe's Columbus science module and Japan's Kibo laboratory compartment.