After postponing what would have been the first all-female spacewalk in March, NASA announced on Friday that it will finally make history this month by sending two women on an all-female excursion outside the International Space Station. NASA astronauts Christina Koch and Jessica Meir, who both currently live on the ISS, are set to perform the spacewalk on October 21st, marking the first time that only women have donned spacesuits to perform work on the outside of a spacecraft.

Originally, Koch was slated to do a spacewalk with her then-crewmate, Anne McClain, which would have been the first all-female spacewalk in the history of space travel. The week of the spacewalk, however, NASA announced that McClain would no longer be working with Koch but would be replaced by her male colleague, Nick Hague. NASA cited spacesuit availability as the culprit; McClain realized she needed a medium-sized spacesuit, but only one was available at the time, and that one went to Koch.

the first time that only women have donned spacesuits to perform work on the outside of a spacecraft

This perceived cancellation caused an uproar, with many decrying the lack of suits sized for women on the ISS. That wasn’t exactly the case, though. At the time, there were two medium-sized spacesuits on the station, but one wasn’t configured and ready for spacewalking. And unlike putting together an ensemble here on Earth, putting together a spacesuit for a spacewalk is an extremely time-consuming process that can take up to 12 hours. It entails piecing together all of the limbs to a torso cover and then attaching a life support system. The astronauts did not have time to reconfigure the second medium-sized suit, and one of the large-sized spacesuits was already available.

But this time around, NASA has the spacesuits ready. Another spacesuit was launched to the ISS this year, this one already in a medium configuration, according to Kirk Shireman, NASA’s program manager for the International Space Station. That means there are now two medium-sized spacesuits prepped for the spacewalk.

NASA claims the decision to launch this second medium-sized suit had to do with the number of spacewalks coming up and which crew members will be available in the months ahead. “We don’t do it for a specific crew member,” Shireman said during a press conference on Friday. “Actually, what we do is we look over the next two years, and look at all the crew members who are [spacewalk] certified, and say, ‘Okay, what’s the sweet spot?’” Shireman noted that over the next couple of years, a lot of “medium suit people” will be heading to the ISS.

Koch and Meir’s potentially history-making spacewalk is one of 10 spacewalks that NASA has planned for the rest of the year. “We have 10 now coming up really fast, so it’s kind of a spacewalk bonanza,” Megan McArthur, NASA’s deputy chief astronaut, said during the press conference. The agency set such an aggressive schedule in order to swap out aging nickel-hydrogen batteries on the ISS with newer lithium-ion ones, which are more powerful and capable than their predecessors. NASA astronauts started replacing these batteries in 2017, and they will be finishing up this year.

Once all of the batteries have been swapped out, astronauts will perform additional spacewalks to repair the Alpha Magnetic Spectrometer, a scientific instrument designed to look for dark matter and anti-matter.

“There are a lot of people that derive motivation from inspiring stories from people that look like them.”

The first of the 10 spacewalks occurred on Sunday, and the next is scheduled for Friday, October 11th. As is the case with all spacewalks, the assignments remain fluid, so it’s possible that things could change again, preventing Koch and Meir from going out together. McArthur noted that NASA tries to come up with its spacewalk pairings based on the experience of its crew members as well as the schedules of incoming and outgoing astronauts to make sure people are as ready as possible to do this work.

“We have to look at the arrival time of the crew members,” McArthur said. “We want to give folks that have just arrived time to get their space legs, if you will. We want to give folks that are about to depart time to prepare to depart. And so we sort of protect those people around those time periods.” Koch won’t be leaving the ISS until February 2020, while Meir is slated to come back to Earth in the spring of next year.

For now, the historic spacewalk is on, and the two astronauts are excited to perform such a big first. “What we’re doing now shows all of the work that went in for the decades prior, all of the women that worked to get us where we are today,” Meir said during an interview on the space station.

“There are a lot of people that derive motivation from inspiring stories from people that look like them,” Koch said in the same interview. “And I think it’s an important aspect of the story to tell.”