This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
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Sixty years ago, the Raytheon Company gave us the first microwave oven. Today, the company, perhaps better known for its missiles, is looking to sell the U.S. military a microwave-based weapon they say will help soldiers control crowds without the risk of seriously injuring anyone.
Raytheon calls its Active Denial System (ADS) technology a "revolutionary non-lethal protection system that employs millimeter wave technology to repel individuals without causing injury." Here’s how it works: Active Denial emits a focused beam of wave energy that travels at the speed of light, heating the water in a person's outer layers of skin and producing an "intolerable heating sensation that causes targeted individuals to flee." Translation: You feel intense pain, but you don’t get hurt, according to Raytheon, which claims that tests show the effects can reach through cracks in and around concrete walls and even through the glass of automobiles.
The U.S. Army plans to buy five truck-mounted Silent Guardians (a smaller version of the Active Denial System) for $25 million, ABC News reports. Raytheon describes its Silent Guardian weapon as roughly one-third the size and power of the Active Denial Systems. The bigger version has a range of 2,297 feet (700 meters), while the smaller one can reach 820 feet (250 meters). According to ABC, the combined weight of the truck-mounted gun and its Ford 550 truck it sits on is about 10,000 pounds (4,536 kilograms).
It's still unclear how such a weapon would be used, although Aviation Week reports that the funding is part of the "global war on terrorism."
Not everyone is sold. One researcher says the device could be quite dangerous. German physicist Jürgen Altmann has analyzed the physics of several directed energy weapons, including Active Denial, the Advanced Tactical Laser (used as a non-lethal weapon), the Pulsed Energy Projectile (a.k.a. "Maximum Pain" laser) and the Long Range Acoustic Device (a.k.a. "Acoustic Blaster"). He found that the Active Denial beam—6.6 feet (2 meters) in diameter—will not be completely uniform; anyone caught in the center will experience more heating than someone at the edge. When used, the device would cause burns on up to 50% of the skin is strikes. Altmann told ABC that second- and third-degree burns covering more than 20% of the body surface are potentially life-threatening due to "toxic tissue-decay products and increased sensitivity to infection" and require intensive care in a specialized unit.
There have been several reports of the ADS causing blistering, with the most serious accident taking place last April, when the Air Force revealed that an airman taking part in a test of ADS had been injured severely enough to be treated at a burn center, Wired reports.
(Image courtesy of Raytheon Company)