It is true that the car will eventually come to a rest in its reference frame once its fuel is exhausted. But, observers in other frames will notice that it has kinetic energy and momentum gained during the acceleration period. They can all determine that the car mass and energy plus the energy that it imparted to other objects during its motion adds up to the beginning amount of mass and energy. This is clearly a different situation than that expected for an EM drive vehicle.
You should note that the car we are discussing is not capable of accelerating unless it is using a road or some electromagnetic force that is not terminated within the car itself. That other object acts as the reaction matter that replaces the exhausted fuel of the rocket concept. An EM drive operating in deep space does not have any tangible object to generate a force against. If someone can show that the EM drive interacts with the earth's gravitational field in a manner that generates a force then perhaps that might make sense. Of course, then the earth would act as the reaction mass. So far I do not recall that being seriously discussed. I suppose that an EM drive that generates gravitational waves and radiates them out the rear would offer a possibility. The recent detection of these waves from the black hole combination radiated an enormous amount of energy and thus mass into space. The radiation converted PE of the pair into radiation that is difficult to detect. But, at least the magnitude of the missing mass is accounted for in the energy of the radiation. I remain skeptical that EM drives are a reality but it does little damage to speculate upon some possible modes of operation. If they eventually are proven real then my bets are that some form of measurable reaction mass equivalent is involved. Dave -----Original Message----- From: mixent <mix...@bigpond.com> To: vortex-l <vortex-l@eskimo.com> Sent: Thu, Mar 17, 2016 4:26 pm Subject: Re: EXTERNAL: Re: [Vo]:Re: EM Drive(s) In reply to David Roberson's message of Thu, 17 Mar 2016 11:58:43 -0400: Hi, [snip] >Of course the EM drive ship that remains in this extreme case(actually nothing >at all if zero exhaust is present) is at rest which means it has zero kinetic >energy relative to itself. Again, this is not a problem for a normal rocket >that spits out reaction mass. In that case all the missing mass and energy >can be located by analyzing the exhaust stream. This is true regardless of >what reference frame you choose. A normal rocket obeys CoE and CoM whereas >the EM Drive ship does not. An electric car speeding down the road will also eventually exhaust all it's stored energy, while remaining motionless in it's own rest frame (BTW everything is always motionless in it's own rest frame, that's why it's called "rest"), nevertheless it has considerable kinetic energy relative to the road. I fail to see the difference between this and the EM drive vehicle. Note that the car used it's energy to change the relationship between it's own frame of reference and that of it's surroundings. So did the EM drive vehicle. Kinetic energy always depends on the frame of reference chosen. When either vehicle starts out with a full fuel load, the "correct" frame of reference is the initial frame in which the "fuel tank" was full. If we stick to that frame instead of swapping and changing when we feel like it, then the kinetic energy gained, as the fuel is used, becomes apparent. For the EM drive ship, the "exhaust" is the universe itself. Just think of spacetime as invisible "train tracks", and it all becomes clear. (Made beautifully visible in a Dr. Who episode about the Orient Express. :) ) Acceleration requires force, and all lines of force have two ends. If one end is attached to the EM drive, then the other end must be attached to something. The only thing that would make sense is the fabric of spacetime itself. In short IMO, if it works at all, then this is how it would have to work. Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
