But the first women-only venture outside of the confines of the space station will have to happen on another day. “After consulting with McClain and Hague following the first spacewalk, mission managers decided to adjust the assignments, due in part to spacesuit availability on the station,” NASA said in a statement.

Stephanie Schierholz, a spokeswoman for NASA, said in an interview on Monday that there were already two medium-size hard upper torsos — “essentially the shirt of the spacesuit,” according to NASA — at the space station.

But there were a couple of issues. One was that Ms. McClain had thought she would be able to work in a large-size torso, but after her spacewalk last Friday, she wore a medium-size torso and learned that it fit her better. Ms. Koch also uses the same size.

And of the two medium-size torsos available, one has yet to be properly configured for a spacewalk. It would take hours of crew labor — not to mention some additional risk — to fix that in time for Friday. Instead of doing that, NASA decided to simply switch out the astronauts.