Two NASA astronauts expect to repair the external cooling system aboard the International Space Station with a pair of upcoming spacewalks, following a serious malfunction late on July 31.
Doug Wheelock, Tracy Caldwell Dyson train for their space station mission Photo Credit/NASA
The first spacewalk by Doug Wheelock and Tracy Caldwell Dyson to replace a bulky pump module that experienced an internal electrical current spike is scheduled to get under way on Friday at 6:55 a.m., EDT. If all goes well, they’ll finish the replacement task on Monday, starting their second six to seven hour spacewalk at the same time.
The current spike shut down one of two external cooling systems, forcing the station’s three Russian cosmonauts and three NASA astronauts to shut off electrical systems and curtail scientific research. Non essential internal lighting and other electrical equipment that must be cooled to prevent dangerous overheating on the orbiting science laboratory has been temporarily de-activated as well.
NASA’s space station mission management team will convene Thursday to make a formal decision on whether to proceed with the spacewalks. Normally, planning for spacewalks of similar complexity would take a couple of weeks. However, managers wish to act quickly to avoid the possibility that the backup cooling system would also experience a crippling problem, said Mike Suffredini, NASA’s space station program manager.
During Friday’s outing, Wheelock and Caldwell Dyson will remove the 780 pound failed pump motor module that circulates an ammonia coolant through outstretched radiators on the right side of the station’s 357-foot-long solar power truss.
Spare cooling system pump module prior to November 2009 shuttle launch Photo credit/NASA
A spare pump module is stowed close to the station’s U. S. airlock on an equipment platform.
Shannon Walker trains for her space station mission
Wheelock will move the old and new pump modules while secured to the tip of the station’s long Canadian robot arm. Fellow astronaut Shannon Walker will operate the arm from a control station in the U. S. Destiny science module.
During Friday’s spacewalk, Wheelock and Caldwell Dyson expect to release five electrical cables and four ammonia fluid cables from the old module, then release and temporarily stow the old module. They’ll install the new module and re-connect as many of the electrical cables and fluid lines as they can.
They’ll finish the connections during Monday’s spacewalk.
At least four fellow NASA astronauts have been assisting with the planning for the spacewalk by rehearsing the activities in NASA’s Neutral Buoyancy Laboratory, a large swimming pool for spacewalk training in Houston.
Mission managers are also keeping an eye on the Sun, which on Aug. 1 unleashed a large Coronal Mass Ejection, a cloud of charged particles that crashed into the Earth’s magnetic field on Tuesday.
While the radiation from the ejection caused the aurora to glow, the levels of charged electrical particles are not expected to endanger Wheelock and Caldwell Dyson during the upcoming spacewalk.
“That is always watched closely,” said NASA mission commentator Kyle Herring.
The spacewalks will be aired on NASA/TV.