NASA Astronauts perform spacewalk aboard the International Space Station

HOUSTON, Texas -- Change the batteries.

It's a task that sounds simple enough, unless you're floating in outer space.

Astronauts Chris Cassidy and Robert Behnken continued a mission Wednesday to replace aging nickel-hydrogen batteries outside the International Space Station.

The operation took six hours to complete. The batteries are part of the power system that's fed by eight solar arrays attached to the ISS.

Behnken arrived at the station on May 31 along with Doug Hurley aboard SpaceX's Crew Dragon. Cassidy is the commander of Expedition 63 and arrived in April.

It's the second spacewalk for the two after a successful spacewalk last week. Another spacewalk is planned to continue the project, which NASA says is halfway completed.
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