CAPE CANAVERAL, Fla. — NASA has nixed the first all-female spacewalk over a spacesuit sizing issue.

Astronaut Anne McClain was supposed to float out of the International Space Station this Friday with newly arrived Christina Koch, to replace old batteries. But McClain pulled herself from the lineup because there’s not enough time to get two medium suits ready for them. Koch will go out with a male crewmate, Nick Hague.

NASA spokeswoman Brandi Dean said Tuesday that McClain trained before flight in both medium and large spacesuits. She wore a medium when she went out on her first spacewalk last Friday and was supposed to switch to a large this week. But after last week’s spacewalk, she decided that a large would be too big.

It would have taken 12 hours to get another medium spacesuit ready and potentially compromised safety, according to Dean. These spacewalks are months late, and with cargo deliveries coming up, NASA wants to keep everything on track.

In 54 years of spacewalking, women have only gone outside with men. That’s because men have always outnumbered women in space. As women continue to make up a greater percentage of the astronaut corps, more gender records will be set and not just in spacewalking, Dean noted.

McClain, Koch and Hague are part of NASA’s Astronaut Class of 2013, the only time there have been the same number of women accepted as men. NASA chose four women and four men that year.

Koch and Hague will continue the battery-swapping work that McClain and Hague began last Friday outside the space station. Old nickel-hydrogen batteries in the solar power grid are being replaced with new, powerful lithium-ion batteries.

McClain will get another shot at spacewalking April 8 when she ventures outside with Canadian astronaut David Saint-Jacques. There are six U.S. spacesuit tops on the station — or hard upper torsos, as NASA calls them — with two considered spares. Both Hague and Saint-Jacques take large.

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