I got the patent application for the EmDrive (GB 2493361). It describes a section of a sphere inside a superconducting chamber. I have attempted to find an analytical solution to the EM wave in the cavity. It consists of spherical bessel functions in radial direction and Legendre polynomials in polar angle. It is axially symmetric so there is no axial function. The patent application describes the inner radius as "cut off" and the outer radius as "free space" - the patent author appears to assume the cavity acts like a pipe rather than a cone. There is no description to the angle on the cone, but the solutions to the standing wave show that only specific angles will give non zero solutions. The argument the author gives is that the inner radius has group velocity zero and the outer radius has group velocity near c - but since it is a cavity it has a standing wave and that makes no sense. If anyone else has worked out the math I'd love to compare notes. Dr. mike
