Running in the atmosphere, the electric field created between a small conductor like a wire or point charge and the larger foil is asymmetric, meaning that the field strength on the surface of the wire is stronger than the electric field holding the electrons to the atoms of the gas molecules. The molecules become ionized and get accelerated by the electric field to the large conductor. This would ordinarily cause no net force, because the action and reaction of the molecules bouncing off the large conductor are exactly balanced. However, the molecules drag on the order of 100 other molecules in the air along with them, creating a frictional force against the air and propelling the craft forward. The most efficient lifter uses pulsed DC and is about on par with a helicopter:
However for near-vacuum, the electric field would have to be strong enough to separate virtual pairs, which would then be sent in opposite directions. There would probably be no interaction with other virtual pairs, so there should be no frictional force and no propulsion:
My best guess is that if they aren’t running the experiments inside Helmholtz Coils, then they are actually creating a homopolar motor that interacts with Earth’s magnetic field by way of the Lorentz force, or possibly resonances set up in the surrounding metal that create small magnetic fields:
The big question is, if one of these drives eventually does work, then why is the force stronger than light pressure? I just mean that it’s straightforward to build an accelerator that creates photons with high enough energy that they oscillate between waves and say electrons/positrons, then separate the pairs and fire them out the back like an ion drive. But the momentum delivered by the energy to do that that should be less than or equal to light pressure.
I suppose if a way can be found to pull virtual pairs from the vacuum that takes less energy than splitting photons, then a Q-thruster might work. It would work by creating mass at one location, propelling the engine against it, and returning the borrowed mass to the vacuum.
I know there’s a lot about quantum mechanics that I don’t understand, and there’s probably a specific reason this won’t work (probably because virtual pairs are created randomly and can’t be coerced into existence?) so if anyone knows, please explain. I’ve tried to write this as scientifically as I can because I dislike psuedoscience.
http://en.wikipedia.org/wiki/Quantum_vacuum_plasma_thruster