SPR Ltd. Home Background Benefits Theory Development Applications Future FAQ FAQ Theory 1. Q. Is the thrust produced by the EmDrive a reactionless force? A. No, the thrust is the result of the reaction between the end plates of the waveguide and the Electromagnetic wave propagated within it. 2. Q. How can a net force be produced by a closed waveguide? A. At the propagation velocities (greater than one tenth the speed of light) the effects of special relativity must be considered. Different reference planes have to be used for the EM wave and the waveguide itself. The thruster is therefore an open system and a net force can be produced. 3. Q. Why does the net force not get balanced out by the axial component of the sidewall force? A. The net force is not balance...