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Neonic

Wed Oct 10 2007, 06:28AM

Registered Member #1053 Joined: Wed Oct 10 2007, 06:24AM
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Posts: 1

I was reading about a new weapon that Raytheon was developing and I was just curious about some things. The frequency that the gun uses is 95GHz, making the wavelength around 2mm if I am correct. Is there any wiremesh that you can buy that is that thin? 2 mm or smaller? What would the feasability of creating a piece of clothing that would shield from this effect. I mean its a 100kW transmitter apparently, so could you block the wave by a few pieces of tin foil, or would you need a pretty good sized sheet of metal. I was just thinking that it would be funny that by using a commonly known principle of Electromagnetic waves you could defeat a future weapon that cost 40 million to complete...

ragnar

Wed Oct 10 2007, 08:45AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
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Posts: 1425

That's the problem -- if we could keep the darn weapons a secret, then we wouldn't need to worry about people wearing mesh... the first time.

Steve Conner

Wed Oct 10 2007, 09:49AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

They'll just make it an offence to wear a tin foil suit and flyscreen goggles while rioting

Seriously, I'm sure you could shield yourself quite effectively using things from the hardware store. But the weapon was probably just conceived as a gravy train for Raytheon, or a R&D project to push the boundaries of microwave technology, and I doubt anybody cares if it's actually any use in battle.

Having said that, war is all about looking good for the press nowadays. A less-than-lethal weapon like this would have some pretty potent PR advantages. It has been discussed here before, so you may turn up some interesting stuff by searching the archives.

Bored Chemist

Wed Oct 10 2007, 05:05PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

OK you are at a riot- perhaps just as a bystander who happened to be there anyway. The police ask everyone to disperse. You , for whatever reason, stay put. They turn on their new magic toy. Everyone else scatters in pain but you, with your tinfoil underwear, stand there looking at them*
OK now you have made them angry , they all have guns and they will all coroborate any story their friends put forward.
How do you imagine this story finishes?

* this would be a bad time to say "Don't taze me bro'"

Avalanche

Wed Oct 10 2007, 05:06PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

Microphone mesh, that's about right.

You might need a fair few microphones though!

Nik

Wed Oct 10 2007, 09:05PM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

I just watched a similar "weapon" demonstrated on tv. Neat idea but my first thought was also of tinfoil hats. Though you can bet that if their microwave beam doesn't get you there will be a bunch of riot police there to finish the job :S

Hazmatt_(The Underdog)

Thu Oct 11 2007, 02:39AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

If you wore a foil hat in that field, wouldn't there be enough gradients to cause a voltage differential along the hat, possibly shocking the hell out of your head?

Steve Conner

Thu Oct 11 2007, 09:32AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Bored Chemist: With an insane amount of hits on YouTube of course! Unless they shoot your buddy with the camera too. However, I'd wonder why they bothered bringing the thing along in the first place, if they were prepared to shoot anyway.

Hazmatt: Nice question, I have no idea of the answer. Please feel free to discuss it further, it may help people to understand how Faraday cages work. Tesla once claimed to be able to light a fluorescent tube inside a Faraday cage with a coil outside it.

Hazmatt_(The Underdog)

Thu Oct 11 2007, 09:10PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

My theory is just that the induced eddy currents will cause differential voltages throughout the surface, much like a CD in a microwave, and that's quite a spectacular failure!

I know I wouldn't want a sparking burning foil on my head. I just don't know if that can happen outside a resonant cavity or not.

sehrgut

Mon Oct 22 2007, 07:42PM

Registered Member #1017 Joined: Fri Sept 21 2007, 09:08PM
Location:
Posts: 24

One thing the erstwhile AFDB folk never think of (and which has bearing here) is that Faraday cages must be grounded to perform significantly in shielding capacity. Especially in high-dissipation service like this, an earth ground would be necessary. Otherwise, said arcing and such would occur. The reason the Faraday screen in a microwave window doesn't arc, but aluminum foil does, is that the wire mesh is grounded, but the foil isn't.

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