At first it feels like a giant invisible hairdryer is blowing hot air on you. But a few seconds later you feel as though you are burning all over your skin. Welcome to the ‘pain ray’, or the ‘heat ray’, or to use the proper military term, ‘active denial’.
Active denial falls into the category of ‘non-lethal’ weapons. It was designed to control or subdue people in war zones, supposedly with little or no injury. It’s claimed to be less harmful than batons, rubber bullets or tasers. It’s basically just a super-powerful microwave beam.
We all know that a microwave oven warms up last night’s Thai takeaway leftovers by blasting them with microwaves. The food absorbs the microwaves, and the energy they carry gets turned into heat.
In your home, the power output of your microwave oven is about 1 kilowatt, and the microwaves usually have a frequency of around 2.45 gigahertz — which corresponds to a wavelength around 122 millimetres. Thanks to this long wavelength, the microwaves can penetrate deeply into your food.
Back in the late 1980s, the US military began thinking about how to use microwave energy as a non-lethal weapon. This research was done at the Air Force Research Laboratory at Kirtland Air Force Base in Albuquerque, New Mexico. The key was to use microwaves with a frequency of around 95 gigahertz, corresponding to a much shorter wavelength of around 3.2 millimetres. They also cranked up the power to around 1000 kilowatts. These microwaves penetrated the skin to a depth of only about 0.4 millimetres. Water in that thin layer of skin absorbs the microwave energy and turns it into heat.
Luckily for the military, we humans have a very sensitive heat receptor in that outer layer of our skin. It’s called a thermal nocioceptor.
From an evolutionary point of view, it’s very important that we are sensitive to heat, because our skin is so fragile. You can get a very nasty full-thickness burn from water at the surprisingly low temperature of only 55°C.
The first version of the active denial weapon was called ‘System O’ and was delivered in the year 2000. It worked, but it was seriously overweight at 7.5 tonnes. The current system is lighter, but still has to be carried by a truck. It looks like a large satellite dish and produces a beam about two metres across, and has a range of several hundred metres. It fires in repeated bursts, each about three to five seconds long.
In 2012, Spencer Ackerman, a reporter for Wired magazine, volunteered at a media event to stand in the beam of the pain ray. He says: “My shoulder and upper chest … felt like they were being roasted, with what can be likened to a super-hot tingling feeling”.
Most people can stand the beam for three seconds or less — and then their reflexes take over and they run away.
The active denial system was sent to Afghanistan in 2010, but for various reasons was never used. Raytheon (the fifth largest military contractor in the world) designed and built the active denial system, and has built a few smaller versions — for use in prison cells, as hand-held weapons, and to be fired from aircraft.
As well as being large and cumbersome at the moment, another problem is that the pain ray doesn’t work very well when it’s raining, snowing or whipping up a dust storm. Another problem is that it doesn’t turn on instantly like a light bulb — instead, it takes 16 hours to be fully operational from a cold start. You could keep it running all the time, but it would burn up a lot of fuel.
The heat delivered to the skin by the pain ray depends on the power produced, the distance to the victim, and the length of time for which the power was delivered.
So far in controlled trials, it appears to be relatively safe. There have been only eight burn injuries from the more than 11,000 volunteers who have been exposed to the beam in experimental tests. But in one of those, the power was accidentally reset to maximum, and the burns were so severe that the volunteer apparently needed skin grafts. Furthermore, a ‘controlled trial’ is very different from ‘out in the field’.
And what about permanent injuries?
Consider an oppressive government that wants to stop a legitimate peaceful demonstration or a workers’ strike — they could simply run the pain ray for 10 seconds, instead of five, causing severe burns.
What if the pain ray were used upon a crowd who simply could not leave the area, because the exits were blocked? In that case you would expect that some people would be zapped by the beam several times over — again causing a horrible disfiguring roasting of the skin.
And what about torture?
Overly enthusiastic police officers have been known to use tasers over and over again on people who were already restrained and who posed no threat. If you leave enough time between exposures, the pain ray will cause intense pain, but won’t leave any marks.
Will we be able to trust the authorities never to misuse the pain ray?
Maybe yes, maybe no.
But look on the bright side. When you’re next at a peaceful legitimate demonstration, take last night’s Thai leftovers, in case they pull out the pain ray …
- Active Denial System proves non-lethal maritime security capabilities (stratrisks.com)
- DoD’s Active Denial System (aconservativeedge.wordpress.com)
- DoD’s Active Denial System (misbehavedwoman.wordpress.com)