From: u894793@bruny.cc.utas.edu.au (T. Little)
Subject: Re: Weapons systems?
Keywords: high-G space weapons
Organization: University of Tasmania, Australia.
Date: Sat, 21 Nov 1992 14:29:48 GMT

pksuk@mothra.syr.EDU (Peter K. Suk) writes:

>True, we're all pretty solidly limited by c and E=mc^2.  I was wondering
>if there were any _tighter_ upper bounds.  If you stipulate that your
>warship's drive systems be made from solid state matter, then you start
>to get some interesting dynamics.  

>A limit on the energy gradient of an accelerator interests me because
>it would bound the capability of ships of a given size.  We could say
>that a ship of length L would have thus and such max delta-V / mass
>efficiency.  For one thing, this would necessitate different roles
>for craft of different sizes.  If we make other assumptions about
>materials technology: for example -- that we will never make something
>with more tensile strength than a molecular bond -- then we get another
>limit on the rate of turn for craft of length L.  

>From that, we can get relationships for offensive capability versus
>manuverability versus range. A ship that capable of a certain acceleration 
>has a certain safe distance from which it cannot be hit _at all_, due to
>the fact that information doesn't propagate faster than light.  Given
>enough distance and accelerating ability, the ship can make sure that
>you will never know where it is precisely enough to hit.  

Err, this would require some *awesome* accelerations for practical
distances - if you have 100G accelation for a 10m craft, you need to be
at least 30 000 km away.

>If we place speed limits on our weapons much lower than light, then

... you need a good reason.  I can think of quite a few long-range
NAFAL weapons that are fairly efficient, so there must be some reason
why they won't work.

>interesting interactions take place.  Minimum safe distances and the 
>accelerations required to effect them start to get down to levels where
>they can play a role in space combat.

Yes, NAFAL weapons make the 'safe' distance (due to light delay) rather
extreme.

>Right now, I'm stuck.  I can get limits for electric field gradients.
>(From _Sci Am_, Amateur Scientist, Apr 1989: 10ev per 10E-8 cm.

Why this value?  It sounds about right for molecular disruption, but in
vacuum, this won't apply.  At *very high* gradients, you get production of 
electron-positron pairs.  (This doesn't actually preclude its use - you
could use the beam thus produced as propulsion or weapon).  The fields could
be produced by focussed high-intensity radiation ... I think.

(This depends upon what exactly you mean by 'solid state' drives.  Do you
allow ion drives, for example?  What about chemical rockets?  Lasers?)

>A hilarious article, if you haven't read it.)  However, B-fields look

I'll try to find the article.

>to be harder.  You can make the B-field in a solenoid arbitrarily 
>strong by adding more turns / length.  But eventually your wires get
>so thin that your current has to drop off.  (Remember we're dealing
>with solid state matter.)  So there seems to be a limit in there
>somewhere.  Can any one lend a hand?

B-fields are also able to be generated by radiation - I don't know of any
theoretical upper limit, but given the close relationship between B and E
fields, I expect that an limit on E should imply some limit on B.
(As an 'out-of-the-blue' guess, I'd say  B = E/c)

>Until your _craft_ becomes relativistic, momentum is momentum is
>momentum.  (And even when it does, it still might be -- I don't
>know.)  The photons hitting the vanes of a radiometer are
>'relativistic' but the thing will behave the same way in a light
>breeze (discounting air resistance, of course.)		]

True.  I just didn't consider that such a high exhaust velocity would be
useful except when the craft itself is expected to approach 'c'.
I see now that it could be required to make frequent velocity changes of
smaller magnitude.
--
T. Little   a.k.a.   u894793@bruny.cc.utas.edu.au
Newsgroups: rec.arts.sf.science