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Spacewalking astronauts make station cooling changes BY WILLIAM HARWOOD STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION Posted: January 31, 2007 Space station commander Mike Lopez-Alegria and Sunita Williams successfully connected one of two critical ammonia coolant loops today during the first of two spacewalks devoted to switching the lab complex to its permanent cooling system. It took the astronauts nearly three hours to disconnect and re-connect a variety of fluid lines to bypass an interim cooling system and route ammonia from the permanent system, mounted in the station's main solar array truss, to heat exchangers in the Destiny laboratory module. Because ammonia is toxic, electronic gear in the lab is mounted on cold plates that use circulating water to carry away heat. The warmed water flows through heat exchangers that transfer the heat to ammonia that is pumped through external radiators. Up until this point in the station's assembly, the heat exchangers were connected to a temporary ammonia cooling system that utilized radiators on the P6 solar array truss extending up from the Unity module. But during the last shuttle mission in December, astronauts and flight controllers activated the station's permanent electrical system, along with big pumps, radiators and other equipment in the main solar array truss that make up the lab's two independent permanent cooling loops. The P6 solar wings and radiators providing interim power and cooling up to this point will be moved to the left end of the solar array truss in September where it will become part of the permanent power system. The left wing of the P6 array was retracted in December and the starboard wing will be retracted during a shuttle mission in March. During today's spacewalk, Lopez-Alegria and Williams, working in a cramped area known as the "rat's nest" between the lab module, Unity and the Z1 truss that supports the P6 solar array, disconnected four fluid lines that had been routing ammonia to the temporary cooling system and reconnected them to loop A of the permanent system. Flight controllers reported good ammonia flow through Loop A and good temperatures after the reconfiguration "so you guys have been doing really good work," called spacewalk engineer Chris Looper from mission control. "I know it's been hard. It looked to me like access to those was actually tougher than it is in the NBL (spacewalk training pool), which is not really surprising. But I feel for you." "Well thanks," Lopez-Alegria said. "You're right about that access. It's pretty abysmal." The astronauts took great care making sure each quick-disconnect fitting was secure and leak free, pushing and pulling on the lines and securing thermal booties as required to maintain the proper temperature. "OK, I see a good line on your latch," Lopez-Alegria said in a typical exchange. "And I see a good line on yours," Williams confirmed. "OK, and then a pull test, right?" "That's affirmative, Mike," mission control replied. "A pull test and then the final will be to pull the bale aft and then full forward. That'll tell you you've got it on good." "OK, that's complete." The astronauts were strictly business as they worked through the long checklist with the only levity coming when Lopez-Alegria joked at one point, "OK, my bootie is open and bootie integrity is bootie-licious." Because of problems with ammonia leakage during an earlier mission, the astronauts were prepared to carry out extensive spacesuit decontamination procedures to make sure no dangerous levels of ammonia could make it into the station's airlock and into the lab's air supply. But to everyone's relief, there were no signs of leakage today and with the loop A connections complete, ground controllers geared up to retract one of the three radiators on the P6 array. Lopez-Alegria and Williams will lock the radiator down and install a thermal cover before moving on to a few final items if time allows. Three hours into the spacewalk, they were about 50 minutes behind schedule. "We didn't have any ammonia leaks, though," Williams observed. "Boy, we are thankful for that," Looper replied. "We're confident we're going to finish all our nominal tasks in the time that we have remaining. So everybody's feeling good about it up here." "Us too, Chris," said Lopez-Alegria. "It was worth it taking our time."
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