US military vehicle equipped with the Active Denial System (Photo: US Department of Defense)
Concern over the safety of a crowd control system in tests sparks fears about its use in operational situations
by David Hambling
Crowd control always presents a problem for the military and police. How do you keep people away from a site without direct physical confrontation, when someone is almost sure to get hurt? Tear gas has variable effects and depends on wind; rubber bullets have killed. But what about a system that inflicts pain at a distance, without contact?
That’s the idea behind the Active Denial System now being tested by the US military. It is designed to cause excruciating pain without injury by projecting a beam of energy about two metres across. Victims describe the sensation as like a giant hairdryer on maximum heat, and no human can withstand it for more than a few seconds. It’s certainly effective, but the report of how a test subject received second-degree burns raises doubts over how harmless it is.
The system, informally known as the “pain ray”, works by producing a beam of short-wavelength microwaves that only penetrate about 0.4mm into the skin, rapidly heating the epidermis. Tests have shown that the beam will not cause cancer, infertility or damaged eyeballs. Heating skin to 55C causes intolerable pain, but no injury – any higher could be hazardous.
The US Air Force says over-exposure shouldn’t occur: “While the intensity of the beam varies with range, the safety margin and effects calculations have taken the maximum beam intensity into account. The repel effect will be virtually identical at short or long ranges until the effects dissipate beyond the system’s effective range.” Dr Juergen Altmann, physicist with the Bochum Verification project, isn’t convinced. His calculations suggest a dangerously narrow safety margin.
In April, the system underwent field testing to determine its effectiveness in different situations. A report on a testing accident was obtained recently by Wired journalist Sharon Weinberger using the Freedom of Information Act. In one scenario the beam was to be used to prevent “Red Force” players from setting up an improvised explosive device “at a very far distance”. (The maximum range is classified, but thought to be about 750 metres.)
Earlier that day it had been used successfully at 75% power level and three-second duration. According to the report: “ADS Operator P4 set power to 100% for four-second duration, so as to be effective at the longer range.” A problem prevented the test from taking place – the system’s magnet requires supercooling and can be temperamental in hot weather. The commander decided to move on to the next scenario, which would test the beam by driving away Red Forces attempting to carry out surveillance at much closer range.
Unfortunately, the crew forgot to change the settings. When the system was fired, “Red Forces Role Player P3 immediately knew that he had received a stronger than usual shot from the ADS; he gave the quit signal and left the field.” The quit signal, raising one hand, has been used throughout Active Denial trials to indicate that a subject wishes to end testing.
The description of the injuries has been censored from the report: all we can see is that they are covered by 11 numbered points. An Air Force statement says: “the injury was classified as a second degree burn,” a type characterised by blistering. Local newspapers reported that the airman suffered burns on both legs and spent two days in the Joseph M Still Burn Centre in Augusta, Georgia. The official report puts the injury cost at $17,748.
Clearly the safeguards do not prevent operator error. “This document confirms my analysis that the intensity and dose to the target subjects is left to the discretion of the operator,” says Dr Altmann. “Not only can he or she re-trigger on the same person without giving appropriate cooling time, but also the strength of the beam and duration can be changed during action. Both lead to the possibility of second- and third-degree burn injury, which becomes life-threatening if more than 20% to 50% of body surface is affected.”
Steve Wright of Leeds Metropolitan University expresses similar concerns. “If this means that these parameters do not have automatic safety overrides in place, there is the option of using this weapon to facilitate maiming injuries or punitive incapacitation – and this was at four seconds. We do not know what injuries would emerge for longer than this because US authorities have seen fit to heavily censor the biomedical information from the public record.”
If the system were used in Iraq, Wright believes safety considerations might be overlooked. “In the fear-filled conditions of a live and hostile confrontation, the natural temptation would be to turn the weapon up to full power to be certain that people taken down by it stayed down.”
Altmann agrees that foreign use could be more dangerous. “In tests with their own personnel the US military are certainly relatively cautious,” he says. “It is not difficult to imagine, on the other hand, what can happen in an occupied country.”
Moreover, reports from previous tests show that reflections of the beam can cause hotspots more than twice as strong as the main beam. Software designed to check mobile phone signal strength has been used to predict where these might appear, but it is not part of the system.
Proponents argue that it is better to risk causing a few minor burns than to use live ammunition, often the only alternative. Opponents are worried that if Active Denial is deployed, it could be the start of a new form of high-tech oppression. “One day the manufacturer will sell it, perhaps to security forces of allies with less sensitive tendencies,” says Wright. “Can one imagine this weapon being turned on democratic forces in Pakistan, for example, and the authorities using restraint?”