ALT NASA astronaut Christina Koch prepares to exit the crew lock portion of the Quest airlock into the vacuum of space. She and fellow NASA astronaut Jessica Meir (out of frame) conducted a spacewalk for seven hours and 17 minutes to swap a failed battery charge-discharge unit (BCDU) with a spare during the first all-woman spacewalk. The BCDU regulates the charge to the batteries that collect and distribute solar power to the orbiting lab’s systems.

ALT NASA astronaut Jessica Meir is pictured during a spacewalk with fellow NASA astronaut Christina Koch (out of frame). They ventured into the vacuum of space for seven hours and 17 minutes to swap a failed battery charge-discharge unit (BCDU) with a spare during the first all-woman spacewalk. The BCDU regulates the charge to the batteries that collect and distribute solar power to the orbiting lab’s systems.

ALT NASA astronauts Jessica Meir (left) and Christina Koch (right) to prepare to leave the hatch of the International Space Station and begin the historic first-ever all-female spacewalk. The astronauts replaced a faulty battery charge discharge unit (BCDU) that failed to activate following the Oct. 11 installation of new lithium ion batteries on the space station's exterior structure. The BCDUs regulate the amount of charge put into the batteries that collect energy from the station's solar arrays to power station systems during periods when the station orbits during nighttime passes around Earth. Though the BCDU failure has not impacted station operations or crew safety, it does prevent the new batteries from providing increased station power.

ALT NASA astronaut Jessica Meir takes an out-of-this-world "space-selfie" during the Oct. 18 spacewalk.