"Fly" implies aerodynamic forces. There is no air in a vacuum. Ergo, a frisbee can't fly in a vacuum. Should it be launched in a vacuum, it will contiue on a path determined by launch direction and gravitational forces until it hits something, like a roof. Well, i don't see the "funnin'" icons, so I'll jez have to hope youall recognized funnin' when you read it.