Schneier on Security

Clive Robinson • January 17, 2021 1:11 AM

@ vas pup,

That NIJ report is a joke, basically it’s a request for a couple of million USD very loosely wrapped in a précis of previous carried out and notably incompleate work.

For instance the use of what are “radiant energy devices” for neural stimulation or overload just mentioned sound and light, which known organisms have aclimated to for longer than than humans have existed[1]. Thus humans have at best a logrithmic response to[2] and therefore have very distinct issues with the energies involved.

There are other radiant energy deterant devices that work in the lower ends of both EM and sonic spectrums which organisms are either not well acclimateed to or that induce flinch or startle responses. This includes heat energy (IR( and heat inducing energy (Microwave HERF) and subsonic devices that cause “gut churning” and similar responses.

But what the report failed to mention is not only are all radiant energy devices problemattic for close in work due to the nueral logrithmic response, but they have significant power issues requiring impractical power storage and delivery issues.

These two reasons are why radient energy nonlethal deterants have only realy been developed for “long range” use from protected positions with clear fields of operation which friendly forces can easily determin and stay out of, and opposition forces have to cross (think World War One tactics developed around the machine gun with kill zones and safe corridors).

But directed energy weapons also have another issue, to get the desired narrow field of projection needs the emitter to be part of a collimating device. Which are the equivalent of a large lenses, parabolic reflector or phased array antennas. That are not just physically large as they are inversely proportional to the frequency in use, they also tend to be quite fragile thus highly susceptible to kinetic weapons such as hand guns or rifles or even stones from catapults, that have effective ranges many times that of equivalntly usable directed energy weapons.

But there are more disadvantages, with few exceptions the generator system tend to be quite inefficient lasers for instance tend to be in the low percent range, RF generators are better at upto 60% with some microwave generators up above 80% which with power levels in the kilowatt region and above makes heat a very significant problem as well as shielding for the opperator.

Which is why most usable less than leathal weapons tend to be kinetic in nature, in effect a gun/cannon with a low velocity large diameter often high mass but low density projectile to deliver high energy in a non penetrating way. The need for large diameter puts a significant range limitation or operational exclusion zone around all less than or non leathal weapons.

Some thinking in this area is to use feedback mechanisms to minimise exclusion zones and maximise range. However if the feedback mechanism becomes known to a potential opponent they can design methods to interfere with the feedback mechanism making it either compleatly ineffective or significantly aproaching lethal depending on the opponents aims and objectives.

You can co-opt the laws of physics to a certain extent. Kinetic weapons have a 1/r range, radiant weapons have a 1/(r^2) range and volumetric weapons a 1/(r^3) range.

So if you then consider an active payload you can seperate it into a delivery system and a payload system. So if you consider a gas grenade it’s delivery mechanism has a 1/r range but the payload only has a 1/(r^3) range. If it were not for other factors such as wind, density, humidity effects on the payload deployment they would be considered to have ideal precision non leathal weapon characteristics. Then if you go on and consider a “flash bang” grenade these likewise have a 1/r delivery range but a 1/(r^2) payload range but the energy levels are very high and there have been fatalities with them. As for fragmentation grenades they have a 1/r delivery range and a 1/r payload range, which is not very desirable from an operators perspective.

[1] It’s not known when creatures first started to respond to sound below 30kHz or light in what we call the visable spectrum, but it was long before “the fish came on land”.

[2] The neural system is difficult to saturate and safe energy levels between effective debilitating and permenent physiological, injury or lethality are quite small. Thus unless very highly directed are more likely to cause significant harm to those close to any emitter (own forces) than to those in the longer distance (opposing forces). In the main such devices are more a “movie plot” device to get around a scripting issue such as the Startrek “stun setting” and “transport”.

Clive Robinson • January 17, 2021 12:02 PM

@ JonKnowsNothing, ALL,

There have been reports and studies over a number of years that link US Navy Sonar pulses with mass beaching of whales and dolphins.

Yes active “SOund NAvigation and Ranging” (SONAR) uses one heck of a lot of “peak power” like RADAR it can be thousands of times the mean power emitted. Such energy over such a short duration can do quite a bit of damage when it transitions from a near imcompressible medium like salt water into a quite compressible thus energy storing medium like the organs of living creatures.

Some may not remember but the crew capsules of early US space missions carried what was in effect a sound bomb[1].

So sound energy trapped in various salt water layers hardly attenuates and travels immense distances the energy initially diminiting at 1/(r^2) untill trapped by the layer boundries then effectively diminishing as a spreading circumfrance of a circle 1/(Wr).

As can be appreciated such a shock wave is not going to play nicely with organics.

The SOFAR bomb was developed during WWII to help locate downed pilots, later it was used so that underwater vessels could at a prearanged time set of such a device so that their position could be reported without having to surface to send radio communications.

But the US Navy amongst others use “towed arrays” which are basically syrings of sensors and emitters upto 2kM long like a Very Long Base Line telescope system the array using different phases and amplitudes can transmit and receive from very narrow angle disks/beams.

What the peek and mean powers are I guess is still classified but approximations can be made based on commercialy available parts.

I don’t have sufficient data to hand to do so but if other people want to have ago it’s not exactly difficult OSINT.

[1] The purpose of the “Sound Fixing And Ranging” (SOFAR) bomb was if the capsule sank it would explode and send out an underwater pulse that could be picked up upto 4800kM away. The only capsule that did sink was Gus Grissoms Liberty Bell 7, which was eventually recovered and brought to the surface in 1999 on the 30th anniversary of the lunar landing, extra care had to be excercised as the SOFAR bomb had not gone off as intended, thus the whole capsule had to be treated as unexploded ordinance untill it was removed.

https://en.m.wikipedia.org/wiki/Sofar_bomb