Two American astronauts took a spacewalk Friday to replace aging batteries on the International Space Station.
NASA's Anne McClain and Nick Hague are scheduled to work in space for several hours to swap out three old nickel-hydrogen batteries with more powerful lithium-ion batteries.
The duo overcame minor struggles in their first task, which involved attaching a tool bag on one of the station's trusses for possible future use.
The station's robotic arm did much of the heavy work already, but the astronauts still have to lug 300-pound adaptors the size of a large coffee table and reconnect attachments.
Even when the chore is complete, there will still be more of the 20-year-old station's original batteries to replace. NASA is about halfway through replacing 48 batteries with ones that are expected to last the remainder of the station's life.
The space station uses solar panels to generate power but the batteries are used when it's in the dark and not getting power from the sun.
Friday's spacewalk is the first of three planned excursions to replace batteries and perform other maintenance. Next week's spacewalk will include the first all-female crew, including McClain.