I'm inclined to agree with Einstein that "God does not play dice with the Universe."
In the same way, it seems intrinsically obvious that we will not be able to get "something for nothing." If the Universe is organized the way the Newtonian world is, that becomes true.
I wouldn't mind seeing some form of propulsion which did not depend on action-reaction. But I would expect to have to pay for it.
The idea that energy is out there, just waiting for a signal or catalyst of some nature to release it, seems untenable.
On the other hand, if one were a god, just giving the command, "Let There Be Light!" might be enough of a catalyst for such a reaction.
But we are not gods, yet.
Recent experiments regarding Quantum gravity, Gauge Theory, and M-theory all point to gravity being a lot closer to Magnetism than we've though. It's just that in 7- or 11-D space/time, only one part of gravity "extends" into Einsteinian 4-D space/time with 3 or 4 other dimensions its effects extends through. If a couple of these experiments shake out the way I think they will, then gravity is just another force like electro/magnetism and can be generated, shielded against, and go through all the other energy state transformations that all other types of energy do.
This means control of inertia as well. Without inertia, Light speed, relative to local space/time reference frame, is entirely possible without violating General Relativity. Special Relativity is already on shaky ground and even Newton didn't want to theorize as to what actually causes gravity.