Originally I was planning to have one "main" NewtonWorld object which is the scene and the station exteriors would belong to that world. The station interiors would be their own NewtonWorld objects and all inside them would belong to them, I think this would have solved the gravity problem, but I haven't actually tried it (for the reasons stated in my earlier posts ).

I'm still planning to have at least two interior scenes for every mission in the game to justify the FPS genre.