My recent pieces on the Active Denial System (ADS) or pain beam sparks discussions here and elsewhere on the web. One of the most common challenges to the device is that the beam of short-wavelength microwaves could easily be blocked with tinfoil.
Its not that easy.
Captain Jay Delarosa, spokesman for the Joint Non-Lethal Weapons Directorate told me:
"We have conducted extensive testing and have determined that most readily available materials are not effective as countermeasures against the ADS.
Few people appreciate the reasons behind this, and even John Pikes otherwise excellent GlobalSecurity site claims:
Countermeasures against the weapon could be quite straightforward for example covering up the body with thick clothes or carrying a metallic sheet or even a trash can lid as a shield or reflector.
As described previously, the beam is at least two meters in diameter, and the smallest skin exposure is enough to cause intolerable pain. A red hot poker does not need to be in touch with much skin to make you pull away, and the ADS causes as much pain on your nerve endings. A shield will not work unless it covers your whole body and them some, because the ADS beam diffracts. According to an article in Aviation Week & Space Technology last July -
actual tests show that the beams penetrate even minute openings or cracks, for example, and sometimes appear almost to wrap around corners to affect fingers and feet of those trying to hide behind or hold up protective devices.
"The radio frequency is hard to block," Booen says. "Some of the people tested against tried to hide by laying down behind some concrete traffic barriers and the beam went underneath [where there was uneven contact with the ground]."
What about that tinfoil? It will have to cover every square inch and any rips or tears will make it useless. Joints may be tricky; if you flex foil too many times holes start appearing. For vision you will need a metal mesh visor, like the kind they use on microwave oven doors. The problem is, the size of the mesh depends on the wavelength of the radiation - so short-wavelength ADS beam requires something much finer than normal microwave mesh. You also need to think about the effect on your breathing, body temperature and communication.
While it is theoretically possible to put together an anti-ADS armor suit, this is less of a spur-of-the-moment improvised undertaking and more of an elaborate workshop project taking some time and effort. (And by the same token, you could make yourself bullet-proof if you used quarter-inch steel plate instead of foil.)
Get your suit working and your problems are just beginning, as it will quickly identify you as a troublemaker rather than an innocent bystander. Separating tourists from terrorists is one of the ADSs main goals, and as Capt Delarosa says:
If an individual makes extensive efforts to counter the effect of a non-lethal system, then they are likely showing hostile intent and an escalation of force may be warranted based on existing rules of engagement.
The Marines will always ensure that non-lethals have lethal backup. Marine Corps Colonel Wade Hall is blunt about the use of ADS in a convoy protection scenario:
"If they try and deflect beams then we will kill them because we know what their intentions are"
There is another alternative. The Pulsed Energy Projectile (PEP), which I described in New Scientist (subscribers only) is a non-lethal weapon which fires an extremely short laser pulse, producing a plasma flash-bang at the target. This could be deployed on the same platform as the ADS, using the same power source. Many of the countermeasures that can be envisioned against the ADS could be nullified by the PEP by ablation of the defence according to a Navy study on the effects of plasmas. Such a laser could chew through a layer of foil with a few pulses.
A PEP might also negate foil without having to blast it away. Ultra-short pulses have recently been demonstrated that can turn metals pitch black , so that the surface absorbs incoming radiation and reflective foil is made useless. This technology was developed at Rochester's High Intensity Femtosecond Laser Laboratory ; they are funded by (among others) DARPA and the Air Force Office of Scientific Research. Well be looking more at short pulse lasers in 2007.
There are many questions still remaining around the Active Denial System and its effects. But we may safely assume that in the many years of its development the Air Force has taken possible countermeasures into account.
UPDATE 5TH JAN Some interesting responses in the Comments section.
Leather is no protection; wet leather, like any other wet material, will absorb the beam and heat up. This may sound like a good idea, until you look at the numbers and realise that it only gives you a few seconds extra, then you have extremely hot water/steam in contact with your skin...foil is a better idea. The issues around damp/wet cloth, sweat etc were investigated a few years back in FWR-2002-0016-H Effects of skin and environmental conditions on sensations evoked by MMW covered this). There was some concern about one subject wearing a sweater developing nettle rash (urticaria) which is mentioned in F-BR-2006-0018-H Effects of exposure to 400-W 95-GHz Millimetre Wave Energy on Non-stationary Humans , but this did not happen again.
To clarify one concern, as I understand it running away would not make you a target for escalated force (like getting shot at); turning up in a tinfoil bodysuit might do.
And as for Nicholas Weaver's request "Could you get zapped by it and tell us first hand?" - er, no thanks. It sounds painful. There's a good firsthand account by Eric Adams in Popular Science here:
"About a half-second after 'One,' I felt a warm spot on my back. A millisecond later the heat intensified dramatically, as though someone were pressing an electric burner hard on my back. I expected to hear sizzling, to smell burning flesh. The pain exploded to the point where I was no longer actually thinking, and certainly wasn't in any sort of control of my reactions. With a shout of "Yeow!" I involuntarily sprang out of the way."
-- David Hambling
