Picking up where they left off last week, two space station astronauts ventured back outside the outpost Wednesday and completed the replacement of aging batteries in one of the lab's eight electrical power channels. A final power circuit will be equipped with new batteries during two more spacewalks later this month, wrapping up a complex multi-year upgrade.
The battery replacement work Wednesday was completed in short order and the astronauts were able to press ahead with a few lower-priority "get-ahead" tasks. The only one that did not get accomplished was the planned removal of a ground handling fixture on one of the canisters anchoring a set of solar arrays.
After unbolting the fixture,was unable to pull it free, despite using a pry bar and a bit of elbow grease. Flight controllers finally told him to bolt it back down, deferring the removal to a future spacewalk. NASA plans to remove several such no-longer-needed fixtures to clear the way for a planned power system upgrade.
Otherwise, the six-hour one-minute spacewalk went off without a hitch and engineers reported the newly installed batteries were working normally.
Behnken and station commander, floating in the Quest airlock, switched their spacesuits to battery power at 7:13 a.m. to kick off their second spacewalk in five days, the 229th in station history and the eighth overall for both astronauts.
After checking safety tethers and collecting their tools, the astronauts floated outside and headed to the far right end of the space station's power truss for another round of battery replacement work.
The space station is equipped with four huge solar array wings, each one feeding electricity into two circuits, or power channels. Each of the eight power channels originally included six nickel-hydrogen batteries — 48 in all — to provide electricity when the station is in orbital darkness.
But the original batteries are wearing out, and NASA is in the process of replacing all 48 with 24 more powerful lithium-ion power packs and circuit-completing adapter plates to take the place of batteries that were removed but not replaced.
During spacewalks in 2017, 2019 and in January this year, 36 old batteries in three of the four sets of solar arrays were replaced. Cassidy and Behnken are working to replace a final set in the station's right-side outboard arrays.
, they removed five of the six nickel-hydrogen batteries in one of the outboard power channels and installed two of three lithium-ion batteries and two of three adapter plates in their place.
During Wednesday's work, they finished upgrading power channel 1B and loosened bolts securing batteries in power channel 3B to save time during the first of two spacewalks later this month to finish the battery replacement work. Before calling it a day, they routed power and data cables for a new wireless communications system and attempted to remove the handling fixture. Engineers will troubleshoot that issue to come up with a fix for a downstream spacewalk.