mb@camcon.uucp (Mike Bell) (03/22/88)
Aw hell! Haven't you guys heard that F*rd have been working for years on the so-called `stealth car' for the DoD. It features ultra-smooth body contours to reduce reflection and minimise drag, a low radar cross-section engine using specially-developed ceramics, glass fibre for the bodywork, glass for the windows, etc. It is painted with this really special paint which not only absorbs radar electro-magnetic emissions, but also the visible spectrum as well. You can have it in any colour you like, so long as it's black:-) -- --------------- UUCP: ...!ukc!camcon!mb | Cambridge Consultants Ltd -- Mike Bell -- or: mb@camcon.uucp | Science Park, Milton Road --------------- Phone: +44 223 358855 | Cambridge CB4 4DW ENGLAND [These opinions are not necessarily my company's, or even my own!]
floyd@brl-smoke.ARPA (Floyd C. Wofford) (03/24/88)
In article <1342@titan.camcon.uucp> mb@camcon.uucp (Mike Bell) writes: >Aw hell! Haven't you guys heard that F*rd have been working for years >on the so-called `stealth car' for the DoD. It features ultra-smooth >body contours to reduce reflection and minimise drag, a low radar >cross-section engine using specially-developed ceramics, glass fibre for >the bodywork, glass for the windows, etc. It is painted with this >really special paint which not only absorbs radar electro-magnetic >emissions, but also the visible spectrum as well. > >You can have it in any colour you like, so long as it's black:-) Actually there is another color, Seafoam Green. Black though is infinitely preferrable. In a more serious, if not more speculative, mind I have a question for thought. I am intrigued by passive means of countermeasure. They are or can be cheaper (chicken wire, flares, chaff, compost heaps, etc. etc.) and more fun. They are usually legal. Ok, for those of you in the IEEE's digital signal processing society (ASSP), the Jan. '88 issue of the ASSP Magazine (not the Transactions) has a somewhat provocative article. I am referring to the Schroeder article. Mr. Schroeder seems to be a quixotic character, an APPLIED number theorist. His article seems to be quite interesting with perhaps some utility to the passive ECM arguement here. Mr Schroeder builds "diffraction gratings" with depths and spacings derived from results in number theory (powers of primitive roots to construct reflection coefficients pg.8). The pattern attenuates the zeroeth diffraction order (reduced "radial" return). The energy is effectively scattered everywhere except the direction from which it came. Note, this is my interpretation of the paper, and not necessarily what Mr. Schroeder said. Since effectively, no energy travels back to the detector, the man does not see you. I believe Corvettes and Fiero bodies are made from composite materials. Are these invisible at X-band? Are there others (no resonant dipoles in polymer chains, etc.) suited to make car bodies! If so, the inner surface could be molded to an appropriate pattern (passive ECM-diffraction grating) and painted with a reflective paint. If my train of thought is clear, the outer surface would be attractive (black or seafoam green) and the inner surface would be interesting. Ok, you groovy guys and gals. Chew this idea up. It came from reading the article and the recent discussion on the net. Why will it not work? Why will it work? If it can work, it is probably being worked on right now. The article implied as much. In another vein, I was serious in my follow-up posting a few weeks ago about an absorbing paint. A couple of years ago a friend of mine saw an article in the trade magazines (the same ones you guys saw all your active devices) for a can of spray for your car. It had all the usual hype about how it beat everything that radiated. The follow up was that the person who ran the article wound up in court. He had no product. He got an incredible response from the article (a can was ~$17) and was going to pay someone to invent the product. Many of us chuckled about the article. All of us would have bought a case of the stuff if it was legitimate. So put on your thinking caps. Can we beat 'em at their game? Remember, they started it (none of my friends have radar guns to check if they are speeding)! floyd@brl.arpa
il01+@andrew.cmu.edu (Ihor Andrew Lys) (04/04/88)
I found your post on diffration grating interesting. Its not a bad idea, and I
thought I'd take some time to comment. The principles behind the technology
seem sound. Its great for airplanes. No echo, no see, and you are
essentially invisible. Traffic radar is a different story. Lets look at the
principles behind each for the reason.
I think you will agree that in principle the beam of a scanning radar
system looks at only one spot at a time. It measures the amount of time it
takes for a signal to reach the target and return. Traffic radar illuminates
the road with a wide beam, and monitors the frequency shift due to the doppler
effect of the returned signal.
The fundamental difference is that traffic radar dosent care from where
the signal came. Position radar does. The effect is that smokey will get some
reflected energy from the car, that which bounces off of some other reflective
object. The absence of a direct reflection does not prevent detection. It
does severely decrease the range in certain situations. The vehicle does not
have nearly as high a radar profile as it did before.
The ultimate trick would be to absorb, not reflect the microwaves. It is
a well known fact that this is possible, but again it is difficult. Water
absorbs certain frequencies of microwaves, and this principle is used in the
microwave oven. All you need to do is to find the appropriate molecule and
paint it on the inside of your fiberglass body. Good luck.
-il01 @andrew.cmu.edu -Ihor LysScott_Lawrence_Statton@cup.portal.com (04/05/88)
A simple way to eliminate radar detection is to just xmit a signal
that obliterates that of your fascist opressor [ :-) ] ...
Notably -- a small Gunnplexer type frob mounted on the front of your car
being electrically swept across the band in question (Several will
provide 100% coverage) .... you'll be about a zillion dB stronger
than your reflection, and his gun will register absolute gazbage...
The TRICK is fiting with FCC about the under 100mW rule ... Does that
apply at uWave where 100mW is a LOT of power? (Ok, not THAT much, but
onsiderable!)
(Of course I don't ACTUALLY use this, nor have I tested it, and this
is for informational prposes only :-)
pretty-boy@cup.portal.com ( I hope )
The views presented herein should in no way be mistaken for
reality.doug_rands_merritt@cup.portal.com (04/20/88)
pretty-boy@cup.portal.com says: >A simple way to eliminate radar detection is to just xmit a signal >that obliterates that of your fascist opressor [ :-) ] ... >The TRICK is fiting with FCC about the under 100mW rule ... Just as a technical exercise, mind you, it occurs to me that *the* maximum sizzleage at the least possible power would be achieved using a "phase conjugate active mirror" (see Sci. Amer. Dec '86 and also Jan '87; I also have a ton of other research references if anyone wants more). You need two horizontal masers that form a standing wave in a nonlinear material (nonlinear in terms of an acoustical response in the microwave region of interest; the acoustical waves match the maser standing wave pattern to form a diffraction grating). Into this material you get the radar beam from the cops. By interaction with the standing wave diffraction grating you form a virtual image (the complex conjugate of the incoming object wave pattern). There's a real image too, but you ignore that. Then you amplify the holy s**t out of the virtual image (you know, a maser amplifier rather than an oscillator), and the resulting return beam is 100% directed back at the image of the original transmitter, with effectively no loss. It is furthermore perfectly phase-matched to the resonant frequency of the transmitter, regardless of any passive distorting mediums along the beam path (e.g. reflection from a metal shed alongside the road), resulting in maximum efficiency of absorption. This kind of stuff is usually discussed in terms of optical frequencies and lasers, e.g. SDI plans to use it to spot and burn missles, but you can bet your last penny that the Air Force already uses the scheme I outline above for knocking out enemy radar. And that by now there are ways the military has of hardening radars to defend against it. But the cops don't have that advantage...with sufficient power their radar transducer would explode. Not very nice. It might hurt them. As to how much power...well, how much do you think needs to be absorbed in order to destroy a transducer? The output beam is close to 100% efficient in terms of target absorption, so that'll give you your answer. Note that the phase conjugating amplification step is probably only 10% efficient in use of input energy, though. Doug Merritt sun.com!cup.portal.com!doug-merritt
john@anasaz.UUCP (John Moore) (04/23/88)
In article <4623@cup.portal.com% doug_rands_merritt@cup.portal.com writes:
%pretty-boy@cup.portal.com says:
%%A simple way to eliminate radar detection is to just xmit a signal
%%that obliterates that of your fascist opressor [ :-) ] ...
%%The TRICK is fiting with FCC about the under 100mW rule ...
What 100mw rule???
It is a no-no to intentionally cause interference, NO MATTER WHAT THE
POWER LEVEL!
--
John Moore (NJ7E) hao!noao!mcdsun!nud!anasaz!john
(602) 870-3330 (day or evening)
The opinions expressed here are obviously not mine, so they must be
someone else's.