[Fathom Zero]

Also, isn't gravity, even as weak a force as it is, stronger than this quantum propulsion business? The article talks about probes being tossed off course by the effects of the particles, but if that was what it was using to begin with, then I'd imagine it could be greatly affected by a number of conditions. You could account for the effects of gravity and such and plot a course through space in such a way that it could probably use the effects of gravity to propel itself, even, but there's no way something like this would be able to stand on its own two mediocre thrusting feet.

At least, to my astronomical knowledge.