I don't like this mockup (the moment I uploaded it to Skydrive I realised I'd gone way OTT with it) but I post it in reply to Monroville's comments in the hope it might spark something more subtle. I was trying for an energy propeller sort of idea (as if electricity could be spun in a centrifuge) the inside of the chamber always reminded me of the inside of a top loading washing machine or a candy floss machine (well it did until The Search For Spock came out then I kept expecting The Excelsior to come around the corner). If the walls couldn't spin why not the energy field?:
