Astronaut Doug Wheelock was given the OK by NASA to use a bit of elbow grease in repairing the International Space Station.
Wheelock was allowed to “shake violently” a stuck ammonia connector that has been preventing the crew from getting to a faulty cooling system. The move shook the part loose and will allow astronauts to make the necessary repairs.
A fourth spacewalk likely will be required later to wrap up loose ends and move the old pump to a permanent stowage location.
“Today was a very successful day for us, EVA-2, on our way to replacing the starboard ammonia pump on the ISS,” space station Program Manager Mike Suffredini told reporters. The astronauts and flight controllers “did a fantastic job today. The hardware cooperated with us in some instances, we had a struggle or two in others, but overall we got ahead of the time line and got a few of our get-ahead tasks done in preparation for installing the new pump during EVA-3.”
Wheelock and fellow astronaut Tracy Caldwell Dyson spent 7 hours and 26 minutes during their second coolant system repair spacewalk, removing the fourth and final ammonia line, disconnecting five electrical cables, loosening four bolts, and moving the 780-pound pump module to a nearby attachment fitting. They also prepared the replacement pump for installation by disconnecting three of its five electrical lines.
The third spacewalk originally was targeted for Sunday, but Suffredini said he decided to delay the excursion one day to give the team a chance to catch its collective breath and complete additional planning.
“Based on the amount of work that has been required over the last several days to prepare and implement these last two EVAs, we’ve decided one additional day between EVAs is necessary,” he said. “Therefore, we’re going to do EVA-3…on Monday.
“Our goal on that EVA is to try to get the (replacement) pump installed and hooked up so the team can activate the pump subsequent to that EVA,” Suffredini said. That’ll be a stretch goal. I think the team’s up to it, we’ll have to have a little more cooperation from the hardware. But I think we can get there.”
Asked what might have gone wrong with the original pump, Suffredini said engineers reviewing data from the system discovered unusual currents in the pump motor starting about two months before it shorted out on July 31. Troubleshooters quickly checked the performance of the pump in coolant loop B, but no similar signature was found.
As for problems with the M3 quick-disconnect, Suffredini said it was possible a small piece of debris lodged in one of the internal valves, resulting in the leak seen Saturday.
The procedure to lower pressure in the system prior to the second spacewalk forced ammonia coolant back through the quick-disconnect, possibly freeing any debris that might have been trapped there.
Reactivating coolant loop A will take a few days after the replacement pump is installed. Along with activating the pump and re-pressurizing the ammonia system, flight controllers will need to reconfigure a variety of systems to properly share the thermal load between loops A and B.
“It’s not going to be an immediate process, there’s not one switch we can flip, obviously,” said Flight Director Courtenay McMillan. “Folks are looking hard at what’s the right sequence of steps to take and what do we need to go back and do.”
But activating the new pump “will happen fairly quickly,” Suffredini said. “There’s a lot of work to do to reconfigure the ISS back to the normal configuration where we share loads across the two systems. That’s the part that will probably take us several days. We’ll know that the pump is healthy pretty early on after the EVA, assuming it’s all hooked up correctly.”
Leave a Reply