When two guys self masturbate while seated in a back to back position. This practice stems from the astronaut practice of masturbating back to back to avoid being shot backwards after climax in zero-gravity space
Lieutenant McRae was hoping Commander Bolton would join him in a space crank so the two could safely jack off aboard the ISS without fear of flying backwards into the control panels.
A guy who has a preference for fucking people best described as "space cadets" ie incredibly stupid.
"That Barry, he is such a space invader. He prefers stupid partners."
"Probably because most folks are too smart to let him fuck them."