 Unlike a Mach effect thruster instantaneously exchanging momentum with the distant cosmic matter through the advanced/retarded waves (Wheeler–Feynman absorber theory) of the radiative gravinertial field, White's "Q-thruster" would appear to violate momentum conservation, for the thrust would be produced by pushing off virtual "Q" particle/antiparticle pairs that would annihilate after they have been pushed on.However, it would not necessarily violate the law of conservation of energy, as it requires an electric current to function, much like any "standard" MHD thruster, and cannot produce more kinetic energy than its equivalent net energy input.Woodward and Fearn showed why the amount of electron-positron virtual pairs of the quantum vacuum, used by White as a virtual plasma propellant, cannot account for thrusts in any isolated, closed electromagnetic system such as the QVPT or the EmDrive.