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starship-design: Re: Stellar Drive

At 8:48 PM 10/20/96, Nick Tosh wrote:
>Interesting idea. Is the physics really OK on this one? It sounds dodgy. I
>don't follow the author's attempt to keep Newton's third. What if there
>were no charged matter in the direction of the escaping fields? If there
>were charged matter, would it not make a difference if it was mainly
>negative or positive? The magnetic forces would be in opposite directions
>for opposite charges. If there were no charged matter moving relative to
>the electromagnets, there would again be no possibility of future magnetic
>forces making up lost momentum. Does the concept depend on the statistical
>distribution of charge and velocity throughout the universe surrounding the
>magic drive? Surely the principle of reaction is not statistical in the
>sense thermodynamics is.

There has to be charged matter out there sooner or later.  So the total
momentum of the system (I>E. the universe) is conseved.  Unfortunatly it
sounds like the bulk of the power would go to creating magnetic fields
blasting out into nowhere.  So we have a theoretically possible drive
system, thats not very usefully.  Pity, It could give Kevins MARS system a
big boost?  ;)

>I have a few other points. Timothy wrote:
>>Magnetic fields is just EM-radiation, usually magnetic fields are very low
>>frequency radiation, in some cases almost non-alternating. In any case
>>photons are exchanged.
>>So you  could just as well (even better) use a laser to generate "local
>How would you make a laser pull? Lasers, indeed all real photons, only
>push. The force on the target would be cancelled by the reaction to the
>laser emission in the emitter, and the system would experince no net force.
>With pulling virtual photons, the idea seems to imply an odd free lunch -
>the action and reaction are in the same direction. But we still pay for

The photon presure from the laser would push the ship.

>I think Kevin made a good point about the second electromagnet's field
>interacting with the first electromagnet by inducung a current in it. I
>don't think that shielding it with a superconductor would help - a current
>would be induced in the superconductor, and you would still have your
>unwanted reaction force. It would be like a bar magnet hovering over the
>eddy currents it produces in a superconductor.
>My final point is that if the system doesn't violate Newton's Third Law,
>what's the point of it? Its not really a 'stellar drive' (how did
>reactionless drives get that name?) at all. I assume the point of a
>reactionless drive is to save a starship from using up its energy on
>reaction mass - one would prefer that it convert all its stored energy into
>KE for itself. But if the magnetic fields created eventually do accelerate
>a distant 'reaction mass', no energy has been saved. So is the concept
>really helpful for us?
>Just out of interest, is there any way of focussing virtual photons to
>concentrate a magnetic field in one direction? I doubt it's possible
>without making the photons real first.


Kelly Starks                    Phone: (219) 429-7066    Fax: (219) 429-6859
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