December 16, 2013
ISS Spacewalk May Be Needed To Fix Faulty Cooling Pump
Lawrence LeBlond for redOrbit.com - Your Universe Online
The crew of Expedition 38 was busy on Sunday preparing their spacesuits for a possible extra-vehicular activity (EVA) mission to fix a failing coolant system that was first discovered last Wednesday outside the International Space Station (ISS).
One of two ammonia cooling systems on the US side of the orbiting complex shut down unexpectedly on Wednesday, December 11, after a problem developed with a valve inside a pump located outside the space station. The shutdown forced the crew to turn off non-critical systems and equipment and to suspend some activities and experiments. NASA maintained that the crew themselves were not in any danger due to the issue.
Engineers were still trying to assess their options for fixing the valve on Sunday, according to NASA spokesman Josh Byerly, of the Johnson Space Center in Houston, Texas.
The NASA engineers continued efforts to regulate temperatures in the cooling loop on the station’s starboard truss. The malfunctioning Flow Control Valve in the Pump Module kept ammonia from flowing as needed to keep systems cool. The problem resulted in a drop in temperature in Cooling Loop A. The ammonia helps regulate the temperatures, keeping systems from overheating, yet also keeping them from freezing. Without the ammonia being able to flow through the system properly, the crew shut down systems to keep them from potential damage.
NASA said that it is very likely that spacewalks will be needed sometime this week to attempt to resolve the issue. Flight engineers Rick Mastracchio and Michael Hopkins have been preparing their spacesuits in case spacewalks were needed to replace the faulty pump.
"It's a serious problem, obviously it's something we have to fix," Mastracchio said during an inflight interview with Reuters on Friday. "It's not something I'm worried about, though."
The current malfunction is occurring in the same pump that astronauts used to replace another faulty pump back in 2010. That issue required three separate spacewalks to fix the problem.
"The biggest challenge on this spacewalk, in my opinion, is the large fluid connectors that are connected to the pump module. But of course, we have a lot of tools if we have problems with those to fix that," Mastracchio said.
Because of the malfunction, NASA had also made the call to delay the launch of an Orbital Sciences Corp Antares rocket that was scheduled to lift off on Dec 18. NASA pushed back the launch one day but noted it could also be pushed back as to as far as Dec 21 before having to move the launch into January.
The launch of the Cygnus resupply ship will be Orbital Science’s first attempt at delivering equipment to the $100 billion space station. Cygnus has already made a successful test flight to the orbiting lab in September and once the next flight is given the green light, it will be the first of nine such missions for Orbital Sciences, under a $1.9 billion contract with NASA.
NASA is now looking at a potential window of opportunity on Thursday to launch Cygnus to the ISS. However, if the EVA mission(s) to replace the pump are delayed or take longer than anticipated, that launch window will be moved back.
In hopes of a Thursday launch, Cygnus is scheduled to fair with Antares on Monday and the pair will roll out to the launch pad at Wallops Flight Facility in Virginia on Tuesday.