Re: starship-design: Stellar drive?

[T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)]

>At 9:09 AM 10/16/96, Steve VanDevender wrote:
>>[description of reactionless drive deleted]
>>
>>No one has ever built a _working_ reactionless drive that would work in
>>zero-g and a vacuum.  People have built gizmos that depend on the
>>presence of air or friction to cause the appearance of a reactionless
>>drive, but these gizmos only work when sitting on tables.
>>
>>The problem with a reactionless drive is that it would violate a lot of
>>principles that physicists are pretty attached to, like conservation of
>>momentum.  A lot of the specious reasoning used in the explanation of
>>so-called reactionless drives tends to ignore things like the momentum
>>of electromagnetic radiation or the finite speed of light.
>
>
>
>I know, it sounds like a dean drive or some such nonsence.  The authors
>reply to that is that net momentum of is conserved globally, but not
>locally.  I.E. the magnetics fields will cause a balencing counter force in
>general space, but not in the ship.  (Authors clip added below.)  So total
>energy would be conserved, just not locally.   Using your box analogy.  Its
>a big box, and other things in the box are accelerated with a balencing
>counter force.  But that happens at a distence that needn't concern the
>ship.  (He does by the way consider the finite speed of light, its a major
>element in the description.)
>
>So again, where is the hole in the concept?

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
momentum".

>P.S.
>Is momentum always conserved?  If you mix a mater and anti-mat
>partical, is their momentum carried over to the resulting photons?

Yes, not a tiny bit of momentum gets lost.


Timothy