So I've been told this is impossible before, and while I understand some of the reasoning as to why, I still can't wrap my head around how this wouldn't work, or rather, what it would do instead of working. So here's an image of what it looks like: Its function is this: Step 1: 'Forward' sphere rotates, flipping the whole panel and other sphere over. Step 2: Other sphere performs the same action. Result: Object changes position in space along a specific path. Now there may be other things needed, such as mass shifting from one sphere to the other (i.e. a pumped liquid) so that one has more mass than the other and the sphere doesn't spin like a tire stuck in the mud. But is it really completely impossible? While a mechanism like this would need to move very rapidly to be practical for space travel, it does seem like it could be much more practical in say, re positioning itself in orbit, without fuel, run solely on electricity without any need for gases to exhaust.