Two NASA astronauts took a 6.5-hour spacewalk today for some maintenance upgrades to the International Space Station. They replaced old nickel-hydrogen batteries for new lithium-ion ones.
The ISS uses solar arrays to convert sunlight into electrical energy. However, the solar arrays stop producing energy when in darkness and instead use batteries. Over time, the nickel-hydrogen batteries have lost their ability to stay fully charged.
The replacements will be lighter, more efficient, and smaller (the older batteries were about half the size of a refrigerator). A single lithium-ion battery can replace two nickel-hydrogen batteries.
Watch our video to see the astronauts in action.