In the second of two planned spacewalks to upgrade the International Space Station’s (ISS) power system, two astronauts finished the process of replacing 12 nickel-hydrogen batteries with new lithium-ion units. The spacewalking duo worked so fast, they had time to complete all of the assigned get-ahead tasks.
Expedition 50 Commander and NASA astronaut Shane Kimbrough with Flight Engineer and European Space Agency astronaut Thomas Pesquet switched their spacesuits to battery power at 6:22 a.m. EST (11:22 GMT) on Jan. 13, officially starting Extravehicular Activity (EVA) 39. Not long afterward, the two ventured outside the Quest airlock to begin their six-hour-long spacewalk.
Kimbrough was the lead spacewalker, EV-1, and wore the suit with red stripes. Pesquet was EV-2 and wore the suit with no stripes.
The primary task for this EVA was installing the final battery adapter plates on the starboard 4 (S4) truss segment where the 1A power channel is located.
The 356-foot (109-meter) long truss assembly for the ISS has eight large Solar Array Wings. Each is attached to a power channel with three strings of batteries. Originally, each of those strings included two nickel-hydrogen batteries in series.
To complete the upgrade to lithium-ion batteries, which are lighter and more efficient, only one battery per string is needed. To complete the connection, an adapter plate is placed where the second nickel-hydrogen battery was situated. A data link cable connects the battery with the plate.
The first part of the spacewalk was a near-duplicate of the first, which occurred last Friday, Jan. 6, 2017. It was performed by Kimbrough as well as NASA’s Peggy Whitson.
Just like last week, the EVA comes after the ground-based robotics team finished remotely swapping out batteries that were brought to the outpost by the Japanese Kounotori 6 spacecraft last month.
The job of Kimbrough and Pesquet was to install the three remaining adapter plates and connect the data cables to complete the power circuit. That involved grabbing two of the plates from the Exposed Pallet attached to the nearby Mobile Base System (MBS) and moving them to the S4 truss segment to attach to the empty spots on the 1A power channel.
The lone nickel-hydrogen battery remaining on the 1A channel was then removed from its slot and placed on an adapter plate for long-term storage.
The two astronauts went back to the EP to grab the final adapter plate and installed it on the 1A channel and connected its data cable with the corresponding lithium-ion battery.
This primary task was completed more than two hours ahead of schedule, allowing for various get-ahead tasks to be completed before heading back inside the space station.
The first of these tasks saw the two astronauts work to replace a failed Camera/Light Pan/Tilt Assembly (CLPA). The CLPA was robotically removed from Canadarm2 and stowed on the MBS. A new one will be robotically installed at a later date.
It took a little more work than expected to reach the CLPA location with a foot restraint. However, eventually, Kimbrough used the Pistol Grip Tool to release the unit and put in its place the spare one.
The next task was to replace a Worksite Interface Adapter on Latching End Effector A of Canadarm2. The interface allows spacewalkers to install foot restraints and ride the arm to hard-to-reach locations around the outpost.
Next, Pesquet was tasked with taking pictures of the bundling of cables called the “rat’s nest” between the Z1 truss and S0 truss on top of the Destiny laboratory. This pictures will help plan future spacewalks in the area.
Meanwhile, Kimbrough began removing handrails on Destiny for future antennas to be installed.
The last task saw the duo take a bundle of thermal shields at the airlock and stored them near the Tranquility node. They will eventually be installed on the port Common Berthing Mechanism when it is vacated later this year when Pressurized Mating Adapter 3 is moved from that location to be placed on the space-facing port of Harmony.
After everything was completed, the two made their way back to Quest. The spacewalk officially ended at 11:20 a.m. EST (16:22 GMT) when the hatch was closed and re-pressurization began. The total time for EVA-39 was 5 hours, 58 minutes.
Over the weekend, some post-EVA robotics will work to move the last four nickel-hydrogen batteries from Dextre Special Purpose Dexterous Manipulator to the EP. A total of nine of the 12 replaced units will be placed on the pallet for disposal when the Kounotori 6 spacecraft leaves later this month.
The 3A power channel was checked out last Friday and is fully operational. The 1A channel was activated as soon as the final ground-based checkouts were completed, which occurred just before the end of the EVA-39.
This spacewalk was Kimbrough’s fourth and Pesquet’s first. Kimbrough’s total EVA time is now at 25 hours, 22 minutes.
Today’s spacewalk was the 197th spacewalk in assistance of space station assembly and maintenance for the ISS over the last 18 years, bringing the total to 51 days, 6 hours, and 4 minutes.
Written by: Derek Richardson
Original source: spaceflightinsider.com