Re: Police prepare stunning end for high-speed car chases
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
At 02:15 PM 8/12/96 -0700, Timothy C. May wrote: 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!
Yes, it would be rather impractical for _that_ particular application.
(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.))
The one place where this might be practical is on highways where these units can be placed fairly sparsely and still have a Even so, I think that non-police applications are more "interesting."
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.
That's based on a certain source model. You know, a specific capacitor in series resistance to limit the current. However, if the current was induced from a low-impedance circuit, damaging currents might flow even if the EMF within a certain shielded loop in the car never exceeded a few tens of volts.
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, Tim, remember that I'm postulating an _inductively_ coupled system. Loop on ground, loops in the car, etc. Magnetic coupling. Conduction through car tires would be irrelevant the the functioning of this system. Wouldn't hurt it; wouldn't help it. (Side note: BTW, car tires are not non-conductive. Check it out someday with a ohmmeter.) Jim Bell jimbell@pacifier.com
Whoa there, speederpunks! I've let a couple of these messages go past me without comment, but I think I'd like to throw in a couple cents on this one. 1) I'd like to assure y'all, as someone who has had a run in with a couple bad alternators, that loosing electrical power will not cause you to go careening off the side of the road. Granted, you might be a in fix if your a nine year old kid running from the cops in a '64 volvo, or some other arian super-car, and the power steering went out. But if that were to ever happen, it would be because you ran over a few curbs at ludicrus speed -- not because Johnny Flatfoot hosed ya down with an EM cannon. 2) Someone was curious why they don't just throw some high voltage cables across road and wait for the fire works. Well, this is a no-brainer too. In order for that to work, you sorta have to get me to do two things 1) drive down your street and 2) drive over your wires. Assuming that I have a reson for not being caught, I might not be too cooperative at doing that either. And of course the last consideration is that the guy putting down the wires might not get out of the way fast enough -- y'all come down to texas and ask the armadillo's why thats a problem. 3) It is really pointless to bicker about this. To quote from a not so popular Mark Hamel flick, "Radio, kid. Faster then rubber." Use the force, luke. 4) I would think that y'all would be happy that someone is doing all the tough work of constructing these devices. I think we all know that the first space cadet to haul one of these things into Kabrini Park is gonna loose it. From there its just a matter of time until every speed racer has one of these "inventions" mounted on his car and junior is wanting to order one from the 'Amazing Devices' ad in the back of Popular Science (in fact, I think you already can). From there, I think that a practical and portable EM cannon could become the HOT urban warfare weapon of the next decade. Bonnie and Clyde are going to look like amateurs when any rank and file with a mortage can buzz the bank and take them off-line for a day. Not to mention what you could do to a hospital, police station, air plane, traffic signal, grocery store, U-FO, and anything else that uses 1s and 0s. All safely and anonymously I might add -- a concealed EM cannon isn't gonna draw any attention, even when you fire it. Thats my two cents, Bye y'all. Christopher
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