Shannon Walker, left, Doug Wheelock and Tracy Caldwell Dyson talk with CBS News about thermal control problem. Photo Credit/NASA TV
Activities aboard the International Space Station resumed normal operations on Thursday, following a near three week campaign to overcome an external pump motor failure that crippled half of the orbiting lab’s cooling system.
Back to normal meant that all three of the science labs, the U. S. Destiny, European Columbus and Japanese Kibo modules were receiving the electrical power and thermal control they require.
“It’s all spic and span; it’s back to business as usual,” NASA astronaut Tracy Caldwell Dyson told CBS News in an interview on Thursday. “As far as we can tell, everything is coming back up, nominally.”
The failed Loop A of the station’s dual loop cooling system was fully repaired with a series of spacewalks by Doug Wheelock and Caldwell Dyson on Monday, Aug. 11 and Aug. 7. During Monday’s excursion, the spacewalkers succeeded in replacing a failed pump motor that circulates an ammonia coolant through radiators that jut from the station’s long solar power system truss. The cooling dissipates heat generated by vital internal electronics, including communications and navigation systems, life support equipment and science gear.
The original pump was disabled by an internal electrical short on July 31. The malfunction forced the station’s six U. S. and Russian astronauts to reduce their use of electricity and curtail scientific research. All of the thermal control was temporarily switched to Loop B cooling as a backup.
By Wednesday, all of the electrical systems had returned to operation, and Loop A had resumed its previous thermal control responsibilities. The final step in the recovery on Thursday was the removal of an internal cable that furnished backup Loop B cooling to the station’s Russian segment.
The long recovery effort featured around-the-clock planning by NASA’s Mission Control and space station program personnel. The three spacewalks spanned 22 hours, 49 minutes. The first outing on Aug. 7 provided some anxious moments as the spacewalkers encountered a leak of toxic ammonia while struggling to remove the failed circulation pump.
“When you have half the cooling down for the U. S. segment, there is not room for much error beyond that,” Kirk Shireman, NASA’s space station program deputy manager, told a news briefing that followed the final spacewalk. “Any additional failures could really be ugly for us. From that perspective, we are very happy.”
The station crew intends to make up for lost research activities, and in particular those devoted to life sciences in which they serve as test subjects. The station’s three U.S. crew members will strive for 63 hours of research time next week, about twice the norm.
“We really look forward to getting back to normal and doing the kind of work the space station was meant to accomplish,” said Shireman.
Wheelock characterized the whole episode as a challenge, but a valuable learning experience for NASA.
Congress is currently weighing a White House proposal to extend station operations until at least 2020, five years longer than the original expectation.
“The confidence is real high now,” Wheelock told CBS. “It’s a validation of our team work and our training. Everyone involved, the way everyone came together was just a great lesson in teamwork, how to stick to it and solve a problem.”