NASA presents evidence that microwave thrusters seem to work
The top comment (on the actual article) suggests that the effect may be a result of dark matter resonance:<p><a href="http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.111.231801" rel="nofollow">http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.111...</a><p>Which is way over my head, but interesting.