NASA astronauts conduct second spacewalk for space station power upgrades

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 On July 1, 2020. In this photo, Cassidy is seen on July 9, 2013, during a six-hour, seven-minute spacewalk at the space station. By Ashley Strickland, CNN

(CNN) -- Early Wednesday, NASA astronauts Chris Cassidy and Robert Behnken conducted a spacewalk outside of the International Space Station to replace lithium ion batteries for one of the station's power channels.

Wednesday's spacewalk began at 7:13 a.m. ET and concluded at 1:14 p.m. ET. It lasted for six hours and one minute.

Both astronauts are veteran spacewalkers. This was the eighth 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 one that took place last Friday, was focused on replacing batteries for one of the power channels on the far starboard truss of the station. Because the astronauts accomplished some of the tasks for this spacewalk last week, they also 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.

For this spacewalk, Cassidy was crew member I and wore a spacesuit showing red stripes, while Behnken served as crew member II in a suit with no stripes. Hurley and Russian cosmonaut Ivan Vagner helped Cassidy and Behnken into their spacesuits. Hurley operated the station's robotic arm to support the astronauts outside the 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 NASA press conference last week.

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."

Behnken said he was looking forward to another spacewalk experience.

"I really look forward to the views of the Earth when we get a free moment," he said. "I think each astronaut, when they go out on their first spacewalk, they're really focused on trying to get all the activities accomplished and do a good job so that they can probably get a chance to do another one if the opportunity presents itself.

"But after you've done a couple and know what to expect as you go through it, it is important to, you know, take some mental photographs, some mental images, or remember what it was like to be outside."

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