(CNN) — Early Thursday, NASA astronauts Chris Cassidy and Robert Behnken began a spacewalk outside of the International Space Station to replace lithium ion batteries for one of the station’s power channels.
Thursday’s spacewalk began at 7:10 a.m. ET and is expected to last for seven hours.
Both astronauts are veteran spacewalkers. This was the ninth venture outside for both Cassidy and Behnken, according to NASA.
Behnken, along with NASA astronaut Doug Hurley, launched from the United States and joined Cassidy on the space station on May 31. They were aboard SpaceX’s Crew Dragon during the Demo-2 mission.
These spacewalks are the culmination of a series of power upgrades that began in January 2017 to replace nickel-hydrogen batteries with new lithium ion batteries.
This spacewalk, similar to ones the two astronauts have conducted recently, is focused on replacing batteries for one of the power channels on the far starboard truss of the station.
During their last spacewalk on July 1, the astronauts worked on tasks scheduled for later spacewalks, routed power and ethernet cables and laid the groundwork for future power system upgrades.
These cables will provide better views on future spacewalks, according to NASA.
These power system upgrades, however, are nothing like replacing batteries in your remote. The new batteries each have a mass of 428 pounds. The upgrades require 12 spacewalks in total, since January 2017, to replace the batteries.
Cassidy and Behnken will remove five of six older nickel-hydrogen batteries for the truss’ power system and install three new lithium-ion batteries and hardware.
During an upcoming spacewalk on July 21, the final battery will be removed and stowed during the 300th spacewalk for US astronauts. The first occurred when NASA astronaut Ed White left the Gemini 4 capsule on June 3, 1965.
For this spacewalk, Behnken is crew member I and wearing a spacesuit showing red stripes, while Cassidy serves as crew member II in a suit with no stripes. Hurley helped Cassidy and Behnken into their spacesuits and will support the astronauts from inside the space station.
The battery replacements, which will have a 20-year lifetime, will put the station in a much better configuration for the long term, said Kenneth Todd, deputy International Space Station program manager, during a recent NASA press conference.
Behnken recently discussed the spacewalk, and why it’s important to replace the batteries, during a call to the space station from CNN Innovation and Space Reporter Rachel Crane.
“When the space station is in the sun, it’s collecting energy and it needs to store for when it’s in the dark,” he said. “And so those batteries, as they’re cycled time and time again, they wear down and need to be replaced. And so periodically that maintenance is required.”
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