Rings my bell. I read that story for a class in high school. Neat writing. Too bad I can’t remember the author.
My opinion, they really were on a spaceship, but that of course is open to debate. 
A Google search found a 1953 science fiction short story by Rog Phillips called “The Yellow Pill.” It doesn’t seem to match the plot description you give though, so it’s probably not the same story.