NASA astronauts perform the 1st all-female spacewalk

The world's first female spacewalking team made history high above Earth on Friday, floating out of the International Space Station to fix a broken part of the power network.

As NASA astronauts Christina Koch and Jessica Meir emerged one by one, it marked the first time in a half-century of spacewalking that a woman floated out without a male crewmate.

America's first female spacewalker from 35 years ago, Kathy Sullivan, was delighted. She said It's good to finally have enough women in the astronaut corps and trained for spacewalking for this to happen.

"We've got qualified women running the control, running space centres, commanding the station, commanding spaceships and doing spacewalks," Sullivan told The Associated Press earlier this week. "And golly, gee whiz, every now and then there's more than one woman in the same place."

NASA leaders, Girl Scouts and others cheered Koch and Meir on. Parents also sent in messages of thanks and encouragement via social media. NASA included some in its TV coverage. "Go girls go," two young sisters wrote on a sign in crayon. A group of middle schoolers held a long sign reading "The sky is not the limit!!"

At the same time, many expressed hope this will become routine in the future.

Tracy Caldwell Dyson, a three-time spacewalker who watched from Mission Control, added: "Hopefully, this will now be considered normal."

NASA originally wanted to conduct an all-female spacewalk last spring, but did not have enough medium-size suits ready to go until summer. Koch and Meir were supposed to install more new batteries in a spacewalk next week, but had to venture out three days earlier to deal with an equipment failure that occurred over the weekend. It was the second such failure of a battery charger this year, puzzling engineers and putting a hold on future battery installations for the solar power system.

NASA Administrator Jim Bridenstine watched the big event unfold from NASA headquarters in Washington.

"We have the right people doing the right job at the right time," he said. "They are an inspiration to people all over the world including me. And we're very excited to get this mission underway."

Speaker of the House Nancy Pelosi sent congratulations to Koch and Meir "for leaving their mark on history" and tweeted that they're an inspiration to women and girls across America.

The spacewalkers' main job was to replace the faulty 19-year-old old charge-regulating device the size of a big, bulky box for one of the three new batteries that was installed last week by Koch and Andrew Morgan. A preliminary check showed everything to be good 250 miles (400 kilometres) up, but several more hours were needed to confirm that.

"Jessica and Christina, we are so proud of you," said Morgan, one of four astronauts inside. He called them his "astrosisters."

Spacewalking is widely considered the most dangerous assignment in orbit. Italian astronaut Luca Parmitano, who operated the station's robot arm from inside during Friday's spacewalk, almost drowned in 2013 when his helmet flooded with water from his suit's cooling system.

"Everyone ought to be sending some positive vibes by way of airwaves to space for these two top-notch spacewalkers," Dyson said early in the spacewalk.

Meir, a marine biologist making her spacewalking debut, became the 228th person in the world to conduct a spacewalk and the 15th woman. It was the fourth spacewalk for Koch, an electrical engineer who is seven months into an 11-month mission that will be the longest ever by a woman. Both are members of NASA's Astronaut Class of 2013, the only one equally split between women and men.

Pairing up for a spacewalk was especially meaningful for Koch and Meir; they're close friends. They're also both former Girl Scouts.

It took two decades for women to catch up with men in the spacewalking arena.

The world's first spacewalker on March 18, 1965, Soviet cosmonaut Alexei Leonov, died last week. NASA astronaut Ed White became the first U.S. spacewalker less than three months after Leonov's feat. Women did not follow out the hatch until 1984. The first was Soviet cosmonaut Svetlana Savitskaya. Sullivan followed three months later.

Friday's milestone spacewalk was the 421st for team Earth.