Re: Police prepare stunning end for high-speed car chases

[tcmay@got.net (Timothy C. May)]

At 4:43 AM 8/13/96, jim bell wrote:
>At 09:54 AM 8/12/96 -0700, Timothy C. May wrote:
>
>>
>>(And I'm not ignorant of such technologies, having attended several of the
>>Nuclear and Space Radiation Effects Conferences. I also played around with

>Why would you need an "EM Cannon" for this?  Just string a 1-car-sized loop
>of wire on the surface of a road, and off in the bushes hide a battery,
>DC-to-Hi voltage DC converter and 20kv+ capacitor, and a vacuum switch or
>some other switch arrangement.  When the car in question traverses the loop,
>short the switch and the car will be blasted with 20,000 volt-turns of
>induction.  Sure, most of it will pass harmlessly through the car's steel,
>but even iron has a limited "mu" which means that every electrical device in
>the car will be subjected to a certain amount of induced EMF, probably
>enough to at least reset a few microprocessors and possibly even destroy them.

Well, we're all operating based on speculation, as to intended modes of
operation, what the contracts may ask for, what may eventually get
delivered, etc.

Certainly the described mode, that of a police car _pursuing_ another car,
suggests a car-launched signal. Rewiring the nation's roads to include
buried cables in anticipation of a future use would be pretty expensive!

(And if the cops can plan for a suspect/fleeing car to pass a specific
location, low-tech solutions like laying a row of caltrops across the road
will do much the same thing as "zapping" (which may not even work.))

As to high-voltage zapping, on this I am _extremely_ skeptical, at least as
Jim's proposal above goes. Modern chips are equipped to deal with
high-voltage, having electrostatic discharge (ESD) provisions. Voltages a
lot higher than 20kv.

And getting this hv signal in to the interior of the engine compartment,
and past the various thermal and other shields would be a chore. Certainly
the rubber tires will provide an _awful_ lot of insulation!

No signal at the road level is going to get through the tires, at least not
until the dielectric breakdown of several inches of rubber and air is
achieved!

(And even then, what is the current path? Where does the current coming up
from the road surface go? Even lightning strikes, from above, where the
place for the current to flow is clearly down into the ground, have
virtually no effect on cars and especially not on the insides of cars.)

If cars routinely survive lightning strikes, involving hundreds of
thousands of of volts and fairly substantial currents, then I can't imagine
anything humans can plausibly do along the same lines having any effect.

I won't debate this further, though. I don't know just what the DARPA (or
whomever) contract is asking for. Maybe something can be built, maybe not.

--Tim May

Boycott "Big Brother Inside" software!
We got computers, we're tapping phone lines, we know that that ain't allowed.
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