Stopping Cars With Microwave Radiation 522
Ponca City, We Love You writes "Researchers have created an electromagnetic system that can quickly bring a vehicle to a stop by sending out pulses of microwave radiation to disable the microprocessors that control the central engine functions in a car. A 200-pound unit attached to the roof of a police car can be used to stop fleeing and noncooperative vehicles. The average power emitted in a single shot is about 10 kilowatts at 100 hertz and since each radiated pulse lasts about 50 nanoseconds, the total energy output is 100 joules at a distance of 15 meters. One concern with the device is that it could cause an accident if a car is disabled and a driver loses steering control. The device could also disable other vehicles in the area so the most practical application may be for perimeter protection at remote areas. Criminals have a work-around too. Since electronic control modules were not built into most cars until 1972, the system will not work on automobiles made before that year."
Steering? (Score:4, Informative)
With that said, if the steering somehow could not be controlled with the PCM disabled, I smell lawsuit. This computer killer thing would also disable any other computerized device... like airbags.
Diesels (Score:4, Informative)
I've run diesel engines with NO electric power (dead/frozen battery, broken alternator belt). As long as the fuel is gravity-fed, it'll run.
Fat chance stopping someone who decided to take a front-end loader to make an "ATM withdrawal".
really? (Score:2, Informative)
Re:Faraday cage (Score:5, Informative)
Coaxial feed thru capacitors through a RF gasketed cover followed by a small RF choke and ferrite bead should do the trick.
Concerns are quite valid (Score:4, Informative)
However, steer-by-wire systems are quickly coming into play in America, especially on some of the lower-end GM products. Now I'm no GM engineer yet, but from what I gather the steering system is either on the GMLAN high speed bus or it has its own bus but still gets data off GMLAN.
Now suppose the ECM stops giving out speed information on the GMLAN bus. Hopefully there is a contingency plan in the steering logic so that you can still have some steering I/O even without the vehicle speed information, but if the output isnt on its own bus, I cant say I'd want to be in that car.
Re:Steering? (Score:3, Informative)
Faraday Cage won't necessarily stop this! (Score:5, Informative)
Lots of old school communications protocols are based on single-ended signaling, where one voltage represents a 0 or 1. This includes RS232, Parallel, and even ISA and PCI slots on your motherboard. However, almost everything new that's outside the computer is based on differential signaling -- reading the differential voltage between two wires. This includes 10/100/1000BaseT ethernet over twisted pair, USB, Firewire, etc.
Here's the key difference: when you get noise coupling onto your signal, whether it's a pulse from the engine ignition coil firing or from this car-stopping microwave device, it tends to be the case that the voltage of *both* of the differential wires is increased by the same amount -- so that when the voltages are subtracted, the effect of the noise cancels out.
However, this exploits the fact that no devices have an infinitely large common-mode range. That is, the average voltage of the differential pair must be within some predefined limit, or your circuit won't work. By putting in a big enough pulse, this microwave device might be able to move charges around on the outside of the car body (which happens to be the ground that most devices hook to) enough to move the voltages significantly. This would cause any devices (think an oxygen sensor or a tachometer) to act as though they were momentarily dead.
Thus, even with differential signaling (which cars already use), it's possible to break things by putting too much common-mode noise on top. See Wikipedia article [wikipedia.org].
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Re:What happens when... (Score:3, Informative)
I'm pretty sure the technology has been available to crafty criminals for some time now. This is an old story, as I remember reading about a homebrew project HERF gun, complete with a video of the guy stopping a car in its tracks, right here on Slashdot eight years ago [slashdot.org]. Although, the car-stopping video could be a misplaced memory that actually goes with this later story [slashdot.org]. This is the commercialization of that tech, but (and my memory may be fuzzy here) the one I remember was built with a bank of capacitors from the flash circuits of discarded one-time-use cameras.
BTW, I totally lucked out on this one, since "HERF" is such a rare term. Slashdot search tends to be abysmal for more common words.
Re:What happens when... (Score:4, Informative)
What's to stop it from killing the engine to the police car?
Directional antennas [wikipedia.org] are not exactly new technology. They work just fine for high-power microwave transmitters.
Re:Diesels (Score:3, Informative)
Re:Faraday Cage won't necessarily stop this! (Score:4, Informative)
A Faraday cage is only protective for wavelengths of electromagnetic radiation which are larger than the size of the gaps in the Faraday cage. The car's metal exterior has some pretty big gaps... and beyond that, the panels aren't even connected well to each other electrically. (RF people will put copper mesh down along all the edges of their devices to get everything.) For the microwave wavelengths, they'll come right in and induce all kinds of voltages on your car body.
Still, it's possible to defend against this kind of thing. I just think that the practical defense has more to do with optical isolation and circuit design rather than a Faraday cage shielding.
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100 Hz? (Score:3, Informative)
My '81 (Score:5, Informative)
Re:'67 AMC Rebel (Score:5, Informative)
Re:Steering? (Score:5, Informative)
Re:The real scoop on RFI suppression (Score:5, Informative)
RF on a wire can be shorted directly to the case with no way past due to lead inductance when coaxial feed through capacitors are used. They work well and are used on every microwave oven made. They are on the bottom of the magnitron. The fillimant leads come from the bottom inside a box. They then go through feed through capacitors to keep microwave energy from radiating out the wire.
http://www.freepatentsonline.com/7184256.html [freepatentsonline.com]
photos here at the bottom of the page..
http://www.samwha.co.th/capacitor.htm [samwha.co.th]
RFI suppression on motors..
http://www.freepatentsonline.com/6307344.html [freepatentsonline.com]
RFI protection for pacemakers.. PDF alert..
http://www.interferencetechnology.com/ArchivedArticles/medical/Article08web.pdf?regid= [interferen...nology.com]
A full filter often includes an inductor. Here is an example. PDF alert..
http://www.dearbornelectronics.com/pdf/EMIFilters.pdf [dearbornelectronics.com]
This shows performance curves of various filters. A 3 DB change is the half power point. To have the same effect on a device 3 DB less sensitive would require double the power. Many of these devices have more than 80 DB attenuation at 10 MHZ and above. This would provide a high degree of immunity as the RFI source would need to be very close and very powerful to overcome the attenuation compared to an unprotected device.
Info on ferrite beads is here...
http://www.google.com/search?hl=en&q=ferrite+bead+RFI [google.com]
Unlike a capacitor or inductor, a ferrite bead doesn't re-direct the RF current. It converts it to heat, and in the process, attenuates it. A capacitor on a wire, may make a tuned antenna at some frequencies. The ferrite bead is to prevent these tuned peaks by eating the power. Used in combination with a feed-through will prevent a tuned standing wave building on the wire.
A capacitor and inductor simply make a tuned circuit with a venurable frequency. Diodes, discharge tubes, resistors, and ferrite beads prevent a high Q tuned circuit.
http://en.wikipedia.org/wiki/Q_factor [wikipedia.org]
Re:What happens when... (Score:3, Informative)
Re:What happens when... (Score:3, Informative)
Military spec is even more extreme.
Not USB (Score:3, Informative)
USB doesn't use differential pairs. There are 4 lines - power, ground, transmit, receive. It was designed to replace RS232 and parallel ports - they weren't going for great speeds. I'm actually quite impressed that USB 2.0 works as well as it does as it is a bad design.
But 1394 does use differential pairs. There are either 4 or (more commonly) 6 lines. Power, ground, transmit+, transmit-, receive+, receive-. It is possible to omit the power and ground and thereby only use 4 lines - Sony likes to do this.
It is possible that I'm wrong as I have not done hardware design since the standards were introduced - but I believe I am correct on this one.
Crazy math (Score:3, Informative)
With that in mind it would not be difficult to imagine the beam missing or passing through. Think of how nasty it would be if you lock up cars in front of somebody evading police, or even in front of a persuing cop.
Re:Steering? (Score:1, Informative)
So? (Score:1, Informative)
Only cars with point-type distributors are immune.