Two astronauts made history Friday by embarking on NASA's first all-female spacewalk.

Astronauts Christina Koch and Jessica Meir floated outside the International Space Station at around 7:50 a.m. ET for a planned hours-long excursion to repair the station's power system.

The duo was originally scheduled to perform a spacewalk on Oct. 21, but NASA changed the date to address an unexpected malfunction.

"@Space_Station update: our first all-female spacewalk with @Astro_Christina and @Astro_Jessica will be Thursday or Friday to replace a faulty battery charge-discharge unit," NASA chief Jim Bridenstine said Tuesday on Twitter.

.@Space_Station update: our first all-female spacewalk with @Astro_Christina and @Astro_Jessica will be Thursday or Friday to replace a faulty battery charge-discharge unit. We’ll have a telecon later today. More details: https://t.co/0T6OOfuQQc pic.twitter.com/zQ7cH4fIBg — Jim Bridenstine (@JimBridenstine) October 15, 2019

The astronauts replaced a “battery charge/discharge unit” that failed Oct. 11, after new lithium-ion batteries were installed during a previous spacewalk. The malfunction didn't jeopardize the safety of the crew, the space station or any of the onboard experiments, according to NASA.

The all-female spacewalk was the second of what NASA has called a “spacewalk bonanza,” with 10 outings scheduled through December. Three other spacewalks that were planned for this week and next week have been postponed, according to the agency.

Originally, NASA had planned an all-female spacewalk in March. But that outing — which was to have involved Koch and NASA astronaut Anne McClain — was scrapped because there weren’t enough spacesuits of the right size available on the station.

NASA caught flak for the circumstances surrounding that cancellation. "Gotta love the irony that because women have never spacewalked together before there aren't enough suits so the spacewalk can't happen," one Twitter user said at the time. "What a joke."

This was Meir’s first spacewalk and Koch’s fourth.

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