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Watch the first of two spacewalks this month to swap out batteries on the outside of the space station

The long process of switching to lithium-ion continues

This morning, two astronauts will spacewalk on the outside of the International Space Station, in order to replace the vehicle’s aging nickel-hydrogen batteries with newer lithium-ion ones. NASA astronauts Anne McClain and Nick Hague are set to work for 6.5 hours today on the ISS’s exterior. Their work will continue the years-long process of upgrading the station’s eight main power channels, which are crucial for keeping the ISS functioning.

NASA first started replacing batteries on the ISS in 2017. The original nickel-hydrogen batteries have become less capable of holding a charge over time. “Just like your rechargeable batteries at home, eventually over time, they’re not going to recharge as well,” Kenny Todd, the missions operations manager for the ISS, said during a press conference. “They’re not going to hold as much charge when it comes to putting loads on them.” NASA has always known that the batteries would need to be replaced eventually, so the agency purchased the newer more efficient lithium-ion batteries a few years ago.

Just like here on Earth, lithium-ion has become the battery technology of choice for NASA. These new ISS batteries are preferred as they’re more light-weight and more efficient than their nickel-hydrogen predecessors. As a result, just one lithium-ion battery is needed to replace two of the nickel-hydrogen ones. Originally, each of the eight power channels had six nickel-hydrogen batteries — equalling 48 batteries in total. But once all the upgrades are done, there will only be 24 lithium-ion batteries powering the ISS.

The relative size of the new lithium-ion batteries and their adapter plates, as seen during a press conference
Image: NASA

This battery swap operation still has a long way to go, though. In 2017, astronauts successfully installed six of the lithium-ion batteries on one side of the station. Another six will be installed both today and during a spacewalk set for next week. That means NASA will still have half the process left after this month. The agency isn’t sure yet when the next battery-swap spacewalks will take place, as the ISS still needs to get a new shipment of lithium-ion units. Those should arrive during a Japanese cargo launch later this year.

NASA has already done a lot of work robotically to prepare for today’s spacewalk. The station’s robotic arm maneuvered some of the batteries around to make it easier for McClain and Hague to complete the installation. The two are also tasked with installing adapter plates to the outside of the ISS, which are needed to help connect the lithium-ion batteries to the station’s channels. Once they’re done, a spacewalk next Friday will repeat today’s work on another side of the ISS, and that event will definitely be one to watch. McClain and astronaut Christina Koch are tasked with doing the upgrades, marking the first time a spacewalk will be conducted by only women.

But before that can happen, today’s installation needs to go smoothly. McClain and Hague left the ISS around 8AM ET this morning, and NASA will be showing live views of their spacewalk throughout the day. End your work week by watching astronauts doing their work in the vacuum of space.