Portable EMP gun

[J]

I'm thinking about making a portable EMP gun. This was inspired by the radio at work playing incredibly shite music all day long, driving me crazy. It would be nice to have a permanent off switch ;-) I probably won't get round to building it in time though :-(

I'm thinking about simply getting a 400v, 1000uf cap charged upto 380v (to give a margin, wouldn't want to waste a £15 cap), and discharging this using an SCR into a coil of around 8 to 12 turns of fairly thick wire. By my calculations, this would be discharging just over 70J into the coil, and this would create an EM pulse when the field collapsed.

Does anybody know if this would be powerful enough to destroy an electronic device at about 10 to 15 feet? Also, I'd like to make it directional by perhaps using Al foil to shield the back part of the gun. Any comments?

From the limitted things I've read about EMP weapons, it seems a small number of turns is required. Does 8 to 12 sound reasonable?

The weapon must be fairly quiet, so no spark gaps can be used either in place of the SCR or the antenna.

J

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[Mr Cool]

I think a spark gap surrounded in foam to reduce noise would be the way to go, with a HV cap (10-20kV, a few dozen nF), forming an LC resonant circuit like a Tesla coil primary. I still haven't tested my version of this yet http://theforum.virtualave.net/ubb/smilies/frown.gif.
Obviously this couldn't be done with semiconductors.
Just imagine how fun it'd be to zap S-club 7 music http://theforum.virtualave.net/ubb/smilies/smile.gif

[simply RED]

I've heard of a design when a high amperage current passes through a coil that is round arround cylinder of explosive. The coil ends with antenna. When the current is passed the explosive is detonated, it destroys the coil and that produces a EMP pulse that is transmitted through the antenna.
Have you got reliable sources of info about EMP? Are the antenna and the coil destroyed by the capacitor discharging?

[Mr Cool]

You're talking about bomb-type designs (Explosively-pumped magnetic flux compression generators IIRC), in the thing J's talking about it'd be totally re-usable, but the one you describe is single use as they contain large amounts of HE which blast the thing to pieces.
I don't have much info, just a fairly basic knowledge in electronics.

[J]

Simply Red, the type you're thinking of was discussed in New Scientist last year (I think). I had a quick look through someone else's copy, if anyone has this article I'd be really greatful for a scan :-)

It was as you described, with the wire wrapped around an Al tube, not touching. A high power capacitor is connected to the tube and wire, which closes the circuit when the explosive is detonated, due to the tube expanding into the wire (the explosive is contained in the tube). As the shockwave propagates, the coil is destroyed, forcing the magnetic field to collapse. This causes an enormous EM pulse, which will apparently destroy all electronic devices within a several hundred meter radius.

Only 1 or 2 pounds of high explosive (I think it was TNT in the article) is needed, but design is critical and I think there is charge shaping. Unless the article left something major out, I think one of these would be within the capability of many people here, with some experimentation.

Mr Cool, generating more than a thousand volts or so will be difficult in a portable device that can fit in a small bag. The cap would have to be huge, and an ignition coil or other large transformer would be needed unless very slow charging was acceptable. If it was to be vehicle mounted though...

I think 70J would be enough to do some damage, because my stun gun (homemade) causes my monitor to flicker when it's within a foot or two. It only puts out 0.2 to 0.3 joules per pulse, and the EM energy is released through the spark gap.

J

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[Mr Cool]

The design I've seen uses an HMX-based PBX. The device will be a metre long at least, and I'm guessing that the tube in the middle would be at least 10cm in diameter. That'd be about 12kg of explosives, but they come in all sorts of sizes I expect.
The cap bank is just connected to the wire - when the tube hits it, it shorts it out thus shortening the length of the coil and the number of turns. I suppose VoD of the explosive used determines the pulse characteristics.
The HE is a plain cylinder, but it's important that the detonation wave has a uniform front, and that the coil is shorted more or less perpendicular to the axis of the coil.
I was thinking that one shouldn't be too hard to make, with a suitably sized cap bank.

The cap in my design would not have to be huge. I have a load of 60nF 20kV caps 20cm long, and 4cm in diameter. Charging would be slow, but you wouldn't need a rapid fire device. Commercial stun guns can produce several hundred kV in a device about 8" long from a 9V battery. So although it wouldn't be hand-held, it'd certainly fit in a small bag! Hey, I did see a program on non-lethal weapons a while back, where they demonstrated a HPM device in a caravan or something. A big Marx bank pulsed power to a magnetron with superconducting magnets, it was pretty cool! Apparently it could be used to cause enemy planes to fall out the sky (remember: the WEAPONS aren't lethal, but they didn't make any claims about the crash!)
My design would be much more efficient I think, since the circuit is allowed to resonate. This produces a decaying burst of RF, but in your design there would be one spike and it wouldn't be allowed to resonate, so the rest of the energy would go into heat (I think). Also you'll need some sort of protection for that SCR so that the CEMF doesn't zap it. And a lower voltage, higher uF cap will produce a lower peak power due to the longer discharge time. Sorry, but I think a HV cap is the way to go!
But I would like to be proven wrong, as I've got a lot of flash caps here doing absolutely nothing at the moment! So please try it and tell me the results!

[Anthony]

I remember hearing that high current rather than high voltage was better at producing EMF?

If so, Hawker Technology make a 12v 14ah dry cell lead acid battery (around 6kg) that will produce 5000amps on short circuit, presuming it could sustain this for 1 second that'd be around 60Kjhttp://theforum.virtualave.net/ubb/smilies/smile.gif

[c0deblue]

J:
Don't want to discourage you, but I seriously doubt you'll get what you would call a destructive EMP out of a device that size - and certainly it wouldn't be quiet if you could. A better solution to the annoying radio might be to just zap it directly with the stun gun and blow the detector or tuner front end (for example, a shot right through the insulation of a computer cable will invisibly fry a motherboard by blowing any MOS junctions that get in the way). Waste of time though - the radio would probably be replaced in a day or so and you might wind up having to use the stun gun on the radio's owner or whoever saw you. http://theforum.virtualave.net/ubb/smilies/frown.gif

Seriously though, even the most impressive capacitor discharge circuits like the so-called can-crushers use an awful lot of power to produce relatively puny mechanical results, let alone EMP. As for the monitor flicker you observed, that's probably caused by a combination of the EM field of the output transformer's open core and the electrostatic deflection effects of the HV driving the image off-screen or simulating a blanking pulse. It doesn't take much to disrupt a monitor, as can be seen by bringing a magnet near the case (you'll probably have to degauss afterward).

That isn't to say you couldn't generate some pretty strong magnetic fields, but EMP is a whole 'nother ball game.

As far as the high discharge batteries are concerned, the discharge rate is way too slow. This is also true of higher-value capacitors unless they're very specially designed for rapid discharge. In this respect, a large number of very small-value capacitors in parallel are vastly superior to one large one of the same total capacitance. If you could dump 60 KJ in a nanosecond or two you might just start to approach a measurable EMP output, but even this wouldn't be enough to cause any serious area disruption. If you're going after electronics, a tuned HERF thingy would be the more efficient way to go, but even these require pretty bulky power supplies to produce worthwhile results.

Any system you use, the propagation effects will be determined to a large degree by the inverse square law (even with a "focused" device), so you'll have to have some pretty hellacious forces to begin with in order to achieve destructive effects at a measurable distance.

[This message has been edited by c0deblue (edited August 15, 2001).]

[Mr Cool]

High voltage means you can have a shorter discharge for the same amount of energy. This means you can have much higher peak powers, which is what you want unless you're trying to melt the circuit rather than damage the componenets. I suppose it depends what kind of EMP device you want, the TED variety I made needs high voltage, low uF capacitors but fairly short discharges to get high currents and high peak powers. I suppose it depends on what you mean by low voltage, I've never seen any designs using less than a few kV, mainly because the high voltage allows a higher current to flow.
That battery sounds fun, but I bet it's expensive!!
codeblue: of cousre it'd be quite if it's all solid-state, and your wires didn't vapourise! There'd be a bit of noise from the capacitor expanding when it discharges because the plates aren't being pulled together I guess, the coil and wires will heat up, causing a little bit of noise, and they might repel themselves due to the magnetic field, but it definitely wouldn't be loud.
Can crushers don't produce EMP because they're not designed to. If you had a cap bank that big you could make a GOOD EMP device if you designed it right.
The flickering of a TV screen by a spark is caused purely by radio waves and other EM waves, and can be focussed greatly with a reflector.
60kJ in a nS would produce VERY, VERY, VEEERRRY measurable results IF YOU DESIGN THE CIRCUIT CORRECTLY and DIRECT IT. That's 60,000,000,000,000 watts - an INCREDIBLE amount of power!
HF devices will produce beams that are fairly easy to focus, but with LF devices (like a simple capacitor discharging once through a coil) refraction will be too much of a problem, and it will basically follow the inverse square law.

[Anthony]

I had a suspicion that the energy was required to be over a very short amount of time.

What about a magnatron? The power supply could fit into a back pack and the magnatron itself would be in a handheld unit. Could somekind of "reflector" be used to create a narrow beam of MW? What affect would it have on a radio?

If it failed ot kill the radio then you could at least use it on people who sing along to the radiohttp://theforum.virtualave.net/ubb/smilies/smile.gif

[Mr Cool]

Yeah, it'd work. A car battery or two could supply the power, and you could use short bursts so cooling wasn't a problem.
It'd induce currents in the components of the radio and fry them. The only trouble is that I think the focussing device would need to be quite big - it couldn't be a nice, sneaky attack on the pop music.

[Anthony]

A car battery would be a bit OTT (and heavy!)

1200watt mains inverter, 12v dc input, 250x120x120mm 1.5kg 90% efficient - £219...

Assumbing a 1000w magnatron, 1000w @ 12v = 83A + 10% (efficiency) = 91A

I've got some sealed 12v 7ah lead acid batts which in parallel would easily support those kind of currents (2.5kg each)

Dunno how much space/weight the electrics required to run the magnatron will take up though.

Do you think we're getting a tad too overly complicated? You could just take the fuse out of the plug for the radio...
Or if it's high up (like on a shelf) run a tripwire from the lead to across a door so that the radio gets pulled down and smasheshttp://theforum.virtualave.net/ubb/smilies/smile.gif

Or, what about a plasma canon...?

[c0deblue]

Or a .38 http://theforum.virtualave.net/ubb/smilies/smile.gif

[Mr Cool]

A hammer would work quite well, or perhaps thermite.

[J]

Well, I'm only going to be working there for another few days anyway, since I'm going away for a week (next week) and after that my second year at uni will begin. I think I can just about put up with it for now, but thanks for the suggestions ;-)

I think I'll persue this project though, since the uses would be endless. Speed cameras, electronics in police cars, security guards radios, boy racer's stereo pumping out shite garage music, all valid targets :-)

Does anyone have any more info on how to concentrate the EM into a narrow, powerful beam? If I could get a very tight beam, surely the inverse square law would be overcome at relatively short distances?

I think high voltage is probably the way to go, but I might try the original idea anyway, perhaps very close to a device.

c0deblue, what exactly do you mean by a HERF device?

J

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[Mr Cool]

High Energy Radio Frequency I believe.
Not very sure how you'd get a narrow beam... but I know it'd be easier with a high frequency.

[Machiavelli]

You might want to ask people here
http://www.plans-kits.com
and here
http://www.svbxlabs.com/

[J]

Thanks for those links, the second site in particular is very interesting. It has some notes about a coil gun operating on only 2J, which has sparked my interest.

The EMP section of the plans and kits message board is pretty dead. The second site has a link to the Powerlabs board, which I couldn't access through the powerlabs.org site the last time I tried. It is definitely not dead :-)

J

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[Ezikiel]

Guys I have a small coil gun and I think it does probably put out an EMP but I haven't yet been able to shut off a calculator even when its placed on the coil.
But I am working on the magnetron version, it seems more promising as if u place a wire made of Al foil in side a microwave and turn it on .... one of the ends ignites.
So I am trying the magnetron.
And to narrow the beam down I will probably use a plastic conduit with Magnetron Donuts to guide the microwave.

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[c0deblue]

J: The Powerlabs message board gave me trouble too - repeatedly made the Netscape browser stop responding. Got in just fine using Opera 5.1 though.

Ezikial: The "donuts" will work as a simple waveguide if packed closely together, but so would a plain piece of pipe with diameter greater than 1/4 wavelength of the magnetron's resonant frequency. If you want any kind of gain you'll have to build a horn radiator. There are programs floating around to do these calculations - do a Google search for "microwave horn calculator" or some such.

[DoH BoY]

LOL imagine setting some sort of high power EMP device in the middle of a math exam. The results would be horrifying.

[SawedOff8gaugeman]

<font face="Verdana, Arial" size="2">Originally posted by Machiavelli:
You might want to ask people here
http://www.plans-kits.com
and here
http://www.svbxlabs.com/</font>

Has anyone ordered anything from plans&kits?

I think some of their products sound like crap:

"BIO-ELECTRONIC STIMULATOR

CONTROVERSIAL DEVICE IS SAID TO HAVE BEEN USED AND TESTED IN FOREIGN COUNTRIES TO
CURE INDIVIDUALS OF AIDS, HERPES, AND VARIOUS OTHER VIRAL INFECTIONS THROUGH SPECIAL
ELECTRONIC SIGNALS INTRODUCED INTO THE BODY. U.S DOCTORS WILL NOT ENDORSE IT
BECAUSE THERE IS NO MONEY IN IT FOR THEM. THIS IS A VERY SIMILAR DESIGN THAT IS VERY COST
EFFECTIVE TO BUILD. THEY SELL ON THE INTERNET FOR HUNDREDS OF DOLLARS. UUE SELLS
PARTIAL KITS, PLEASE EMAIL US TO INQUIRE. THEY REALLY WORK, CAN KILL THE FLU OR A COLD IN
SECONDS. PLANS COST $4.00."

"MIND STIMULATOR/BRAIN ENHANCER

THIS DEVICE IS BASED AFTER THE NEUROPHONE CONCEPT. YOU WILL SEE AND HEAR WITHOUT
USING YOUR SENSES. INDUCES SCALAR WAVES IN NERVES THROUGH SIGNAL VECTOR
MANIPULATION IN THE SKIN. $4.00 FOR COMPLETE PLANS/SCHEMATICS."

"SadM...Small Atomic Demolition Munition

STEP BY STEP INFORMATION OBTAINED THROUGH SPECIAL SOURCES. TEACHES YOU HOW TO
MAKE A 6 INCH DIAMETER ATOMIC MUNITION DEVICE. DESIGN USES LESS THAN A COUPLE GRAMS
OF PLUTONIUM OR URANIUM 238. USES ONLY A COUPLE POUNDS OF EXPLOSIVES TO INITIATE.
VERY DETAILED INSTRUCTIONS. PLANS COST $3.00."

[Mr Cool]

They sound like shit. Especially the last one. If they want a fission explosion and not just to poison people, they'll need more than a few grams. And U238 isn't even fissionable.

The first one might be based in truth, athlete's foot and other microbial diseases can be killed with regular treatments using negatively ionised air (connect a pin to the -ve output of a 30kV DC PSU, yo will feel a wind of ionised air coming off the point of the pin).

[J]

Some of those projects do sound like a pay-per-view version of the crapbook. I'd never buy any of those plans, since they're probably adapted from patents and other free information. You'll never know if the plans were actually tested or not (my guess would be no) especially with the illegal devices since they can't admit it if they did.

Anything that claims to cure illnesses is also very suspect, since there's no way of proving it's effectiveness one way or the other.

J

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