Spacewalking astronauts replace batteries

Two NASA astronauts have ventured outside the International Space Station, although plans for the first all-female spacewalk had to be scrapped.

NASA astronauts Christina Koch and Nick Hague reached the International Space Station two weeks ago. (AAP)

Spacewalking astronauts are conducting more battery replacement work outside the International Space Station.

NASA astronauts Christina Koch and Nick Hague floated outside the station on Friday, a week after the first spacewalk to install new and stronger batteries for the station's solar power grid.

Koch was supposed to go out with astronaut Anne McClain, but there weren't enough medium suits readily available. So the first all-female spacewalk had to be scrapped.

A third spacewalk is planned for April 8, but that also will be mixed gender.

The space station's outdated nickel-hydrogen batteries are being replaced with lithium-ion batteries. These batteries store power collected by the solar wings and keep the outpost running when it's on the night side of Earth.

Hague and Koch arrived at the space station two weeks ago.