Washington (AFP)

US astronauts Christina Koch and Jessica Meir flew together Friday from the International Space Station (ISS) to make a repair, marking the first time in six decades of space history that two women are making an exit into space.

A first outing of two female astronauts, Christina Koch and Anne McClain, had been scheduled for March, but NASA had had to cancel it four days before, because they did not have two ready-made combinations of the right size.

Friday's release officially began at 11:38 GMT and is expected to last several hours, in order to change a battery charging unit that went down last weekend.

"Christina, you can get out of the airlock," Astronaut Stephanie Wilson announced from Houston's ground control center.

Then Christina Koch slowly came out floating. "PAH is dry," she confirmed after checking that the inside of her helmet was not leaking water.

"I'm moving ...", said Jessica Meir, who arrived last month aboard the ISS, before going out.

March's heck had provoked a volley of criticism, Hillary Clinton tweeting a lapidary "Make another combination".

NASA had planned everything this time and the two women were out as planned in their bulky combinations, 400 km above the Earth, shooting in orbit at a speed of 8 kilometers per second.

Since the beginning of the ISS in 1998, 220 space sorties have been made by astronauts of all nationalities, mostly Americans. But only 13 Americans, including Christina Koch, and a Russian had so far "walked" in a vacuum. Jessica Meir became the fifteenth.

- First woman on the moon -

Space has long been reserved for men. At NASA, all the first astronauts were military pilots, men. The first woman in space was the Russian Valentina Terechkova, in 1963.

For the Americans, the first to fly was Sally Ride in 1983.

But the latest Nasa astronaut promotion, selected in 2013 and starring Christina Koch and Jessica Meir, was half made up of women.

"We want the space to be accessible to everyone, and this day marks a new stage in this evolution," said the administrator of the American Space Agency, Jim Bridenstine, to the press early on Friday.

"I have an 11 year old daughter, I want her to have the same opportunities as me when I was young," he continued. "We want tomorrow's astronauts to represent the whole of America."

He confirmed that the first woman to walk on the moon was in the current active body of NASA astronauts, which includes 12 women. The Artemis 3 mission is scheduled for 2024, although the schedule has been delayed, and will see two astronauts descend and walk on the moon, for the first time since 1972.

Jim Bridenstine often says that "the next man and the first woman" to walk on the moon will be Americans.

Asked by AFP whether two women could compose this lunar crew, he replied: "It could very well be two women, there is no reason that it is not possible."

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