Two NASA astronauts ventured outside the 20-year-old International Space Station to replace aging nickel-hydrogen batteries with fresh lithium-ion units.
Floating outside the Quest airlock to begin the 6.5-hour-long U.S. EVA-52 was NASA’s Anne McClain and Nick Hague, both Expedition 59 flight engineers. Their task was to make their way to the P4 truss segment located on the port side of the outpost before beginning work to install three adapter plates and shuffle several batteries.
This is expected to make way for ground-based robotics teams to continue work using the 17.6-meter-long Canadarm2 and Dextre robotic “hand” to do the heavy lifting of moving and installing most of the 136-kilogram batteries.
A total of 12 nickel-hydrogen units are being replaced with six lithium-ion batteries. A two spacewalks are required to finish the process of swapping the devices out—the first on the 4A power channel and the second on the 2A channel.
These batteries are used to power the ISS during each 45-minute orbital night and are charged by the station’s giant solar arrays during the 45-minute orbital day.
Originally 48 nickel-hydrogen batteries were used when the truss was first assembled in the 2000s. Since 2017, NASA has been in the process of replacing these with newer, more efficient lithium-ion units. The first of four sets was brought to the outpost in 2017 aboard Kounotori 6 and installed on the S4 truss.
Last fall, Kounotori 7 brought six more batteries and adapter plates for the P4 truss. They attached to an external pallet and stored on the truss when the cargo ship left in November 2018.
U.S. EVA-52 officially began at 12:01 UTC March 22, 2019, when McClain and Hague switched their suits to battery power. McClain was designated EV 1 and was wearing the spacesuit with red stripes, while Hague was EV 2 and wearing a suit with no stripes.
After gathering tools at the beginning of their outing, the two made quick work to reach their work site at the P4 truss. Their primary task was to install three 34-kilogram adapter plates needed to complete circuits on the outposts electrical grid. After all, one lithium-ion unit is replacing two of the older batteries.
The plates also double as a mount for two of the old batteries as the pallet meant to hold the nickel-hydrogen units for disposal can only carry nine.
When Kounotori 8 launches to the ISS in the fall, it will bring another pallet of batteries, this time for the P6 truss. The pallet from Kounotori 7 will be loaded in Kounotori 8 for disposal at the end of its mission. In 2020, Kounotori 9 is expected to bring the batteries for the S6 truss.
McClain and Hague worked fast, quickly getting about a half-hour ahead of the timeline. This allowed McClain to perform one get-ahead task at the back-end of the spacewalk—inspecting and removing a small piece of debris on the Earth-facing port of the Unity module.
Once the astronauts completed all their tasks, they made their way back to Quest to re-enter the outpost. The airlock began repressurising at 18:40 UTC, officially concluding the 6-hour, 39-minute spacewalk.
“You’ve made lots of people happy here; I see smiles on the ground,” said European Space Agency astronaut Thomas Pesquet, who served as the spacewalk communicator in Houston for this EVA. “This is a day you will remember for a long time. Repress safely, the EVA is not over until you are out of the [airlock] and your suits are stowed. But congrats on [completing] all the objectives and more.”
This was the 214th spacewalk in support of space station assembly and maintenance since 1998, bringing the total time spent outside to 55 days, 21 hours and 39 minutes. It was the first for both McClain and Hague.
Next week, McClain will once again exit the ISS, this time with NASA astronaut and Expedition 58 Flight Engineer Christina Koch. Together, the two will perform a nearly-identical set of tasks on the opposite side of P4 to facilitate the installation of three more battery adapters and lithium-ion devices.
This is expected to be the first all-female spacewalk ever performed. Additionally, McClain was the 13th woman to perform an extravehicular activity while Koch will be the 14th.
NOTE: While this article was written by Derek Richardson, it was originally published at SpaceFlight Insider.