Future Weapons: The Active Denial System (ADS)

The Active Denial System (ADS) is a non-lethal, directed-energy weapon developed by the U.S. military. It is a strong millimeter-wave transmitter used for crowd control (the "goodbye effect"). Informally, the weapon is also called pain ray. Raytheon is currently marketing a reduced range version of this technology.

The ADS is currently being considered for deployment in the Iraq war. ADS has also been present at various public events in the United States. It is unclear if the government has sought any authorization to deploy the weapon at home or did so without public input.

The ADS works by directing electromagnetic radiation at a frequency of 95 GHz (a wavelength of 3.2 mm) toward the subjects. The waves excite water molecules in the epidermis to around 55°C (130 degrees Fahrenheit), causing an intensely painful sensation of extreme heat. While not actually burning the skin, the burning sensation is similar to that of a light bulb being pressed against the skin. The focused beam can be directed at targets at a range of just under half a kilometer, or 500 yards. The device can penetrate thick clothing, although not walls. Active Denial utilizes high frequency microwave radiation.

Electromagnetic radiation cannot pass through a conductor, so an effective way to shield yourself from the beam is a Faraday cage, a type of electromagnetic shielding made from a conductive mesh or foil. In the case of a mesh the openings in the weave must be smaller than the wavelength of the radiation, and due to the very high frequency of the ADS (95 GHz) it would be necessary to use a very tightly woven conductive fabric, so thin metallic foil would be more suitable. Any type of metallic foil will easily absorb and deflect the beam.

At 95 GHz, the frequency is much higher than the 2.45 GHz of a microwave oven. This frequency was chosen because, due to the stronger absorption of water at those frequencies, they penetrate the skin to a depth of less than 1/64 of an inch (0.4 mm)," which is where the nerve endings are located. A spokesman for the Air Force Research Laboratory described his experience as a test subject for the system: "For the first millisecond, it just felt like the skin was warming up. Then it got warmer and warmer and you felt like it was on fire.... As soon as you're away from that beam your skin returns to normal and there is no pain."

The ADS is currently only a vehicle mounted weapon, however, U.S. Marines and police are both working on portable versions.

A fully operational and mounted system was demonstrated Wednesday, January 24, 2007, at Moody Air Force Base, Georgia. A Reuters correspondent who volunteered to be shot with the beam during the demonstration described it as "similar to a blast from a very hot oven - too painful to bear without diving for cover."

While the effects can be unpleasant, ADS has undergone extensive testing since its inception more than 12 years ago. Research into whether or not the device will cause long term health effects has been inconclusive. Many aspects of the research are classified making independent evaluation impossible. The beam is designed only to affect an individual for a short moment due to safety presets and features but these setting can be overridden by the operator. According to public release, there have been over 10,700 "shots" by ADS. At least eight people have been seriously injured by the ADS system and several of those were hospitalized with second dgree burns. It is unclear how many injuries may have actually occurred since the program is secretive and witholds much of its data from public.