The Active Denial System, listed on your link, causes pain by heating water in the skin.
What is the proposed system for getting microwaves past the skin into the brain without creating the same effect as the ADS?
What is the proposed system for getting microwaves past the skin into the brain without creating the same effect as the ADS?
Could it be there is some way to target a location with multiple radio beams such that the damaging effect occurs at the point of interference? Maybe just constructive interference from multiple weaker beams? Something like this would need to be aimed precisely of course.
I was further led to thinking about the way you can generate sound at a distance from beams of ultrasound. [0] Either the fluid within the beam or an object struck by the beam acts as a demodulator. I don't really know if something like this could apply with radio.
The other thing that I thought of was the way microwave ovens excite water molecules specifically. Maybe there is some other wavelength or combination of them which excites other specific molecules or structures present in the brain?
Yes, a phased array [1], which is likely what the GGP was referring to by "What is unproven though, is how one would ever shrink the size of an electronic weapon like this."
Advanced radars work by creating a concentrated beam of RF with constructive interference and scanning it across the sky, but the installations are huge. A smaller directed microwave weapon would be meters across, hard to hide, and noisy.
Phased arrays can be very small.
Note that just putting a couple of antennas close to each other to improve angular resolution on the radar isn't really a phased array in the sense that we're talking about.
Specifically, I believe the one on the 737 is the Rockwell Collins WXR-2100.
Surface of the skin has less water than tissue inside, so you would feel pain beneath the skin.
Microwaves attenuate as they penetrate a resistive or high-permittivity substance, because they deposit some of their energy as they pass through. In the limit of infinite depth, no radiation survives and there is no heating. Given a homogenous substance, the heating is always strongest at the surface, decaying exponentially (to a good approximation) as you go deeper.
However, heating is not the same thing as temperature. The surface of food in your microwave is exposed to room-temperature air and can therefore cool down by conducting its heat to that air. Food just under the surface can conduct its heat to the surface food, while deeper food cannot. It's easy to set up situations where this results in a reverse thermal gradient penetrating some distance into the food, or even all the way to the center. This is one of the most significant advantages of microwave heating in industrial material processing, because there are many cases where the normal thermal gradient produces cracking and microwave-induced reverse thermal gradients do not.
You can set up a forward thermal gradient with microwave heating by some combination of hot air, strong attenuation, short exposure times, shorter wavelengths, and great depth, although unless the air is actually hotter than the highest temperature reached within the food there will always be a reverse thermal gradient present at the surface, since the heat equation always produces a continuous temperature field at t ≠ 0. You may be able to get the reverse thermal gradient to be entirely outside the solid body if you work hard enough, but a much easier way is to only measure the temperature at intervals large enough that the entire reverse thermal gradient is smaller than the first interval. For example, if the thermal maximum is 8 mm under the skin, you could measure the temperature at the surface, 1 cm, 2 cm, 3 cm, 4 cm, and 5 cm.
The attenuation is dependent on the attenuating medium and on wavelength. As explained in https://en.wikipedia.org/wiki/Active_Denial_System the ADS uses 95-GHz radio waves with 0.4-mm penetration depth in human flesh, while your microwave oven used 2.4-GHz radio waves with 17-mm penetration depth in human flesh.
nabla9 has been downvoted for politely and straightforwardly, if briefly, explaining these perfectly correct and verifiable facts, facts which are central to the discussion. This makes it clear that the voting public at HN has extremely poor judgment and should not be permitted a vote on comments of decent people.
> When the radar transceiver is energized, it poses a microwave radiation hazard to personnel. The hazard distance for the Q-47 is much greater than the distance for the Q-37. The hazard distance for troops extends in front of the radar for 217 meters over the radars full 1600-mil area of scan. The radar also poses a hazard for electrically detonated explosives. Figure E-14 depicts the radar’s radiation hazard area.
https://web.archive.org/web/20141226051243/http://armypubs.a...
IIRC workers in front of radar antennas noticed chocolate bars melting in their pockets during WWII, and that observation inspired the development of microwave ovens. Not sure how long it took for people to realize that their internal organs were doing something similar to the chocolate bars...
Note to self: pay attention when trimming HF transmitters about where you keep stray digits and where the locations of the tops of trimmers are relative to those digits.
If they were tuned to water molecules, they’d be great at defrosting, and unable to do this: https://youtu.be/xwEQZw3KPWg
No. Microwave hot pockets are famous for coming out boiling on the outside, cold on the inside (if you don't let it sit for a couple minutes to equalize).