Jolly Roger wrote: A copy of the EM Drive theory paper is now available to be downloaded in pdf format at the New Scientist website http://tinyurl.com/npxv8
The paper looks very flawed to me. The forces on the end-walls of the cavity seem to be correctly calculated (and, of course, there is a mismatch which provides the motive force this system is supposed to provide). However, the longitudinal component of the force on the cavity imparted by reflections from the tapered walls seems to be entirely omitted. I believe that these forces sum up to exactly cancel the mismatch calculated just from including the ends of the cavity. This is a similar mistake to assuming that if the cavity where filled with a perssurized gas, the gas would exert more force on the larger end than on the smaller end and so provide a resultant force on the cavity towards the larger end. This doesn’t happen because the pressure of the gas on the tapered wall exerts a resultant force towards the narrower end, exactly cancelling the effect.
I believe that the author also makes an error in calculating the limiting velocity. The problem is a relativistic one and therefore the solution has to be frame independent. This means that the limiting velocity has to be quoted relative to something, but the author only refers to a stationary system. In any system operating in free space with no external forces, any thrust has to be frame independent, which means that the only limiting speed (to an external observer) is the speed of light itself, although someone sitting inside the cavity would continue to feel exactly the same acceleration for however long energy continues to be put into the system.
