Test subjects can't see the invisible beam from the Pentagon's new, Star Trek-like weapon, but no one has withstood the pain it produces for more than three seconds.
People who volunteered to stand in front of the directed energy beam say they felt as if they were on fire. When they stepped aside, the pain disappeared instantly.
The long-range column of millimeter-wave energy is known as the "Active Denial System" for its ability to prevent an aggressor from advancing. Senior military officials, who plan to deliver the device for troop evaluation this fall, say years of testing has produced no sign it will lead to health effects beyond perhaps causing skin to temporarily redden.
It is among the most potent of a new generation of futuristic, "less-than-lethal" weapons being developed by the Defense Department - tools that could dramatically alter the way police control riots and soldiers fight wars.
Other nonlethal devices undergoing tests include "superlubricants" that could make a road or runway too slippery for car or airplane tires to gain traction; directed sound waves to drive people away from an area; and nets able to stop cars.
Marine Col. David Karcher, who heads the Pentagon's Joint Non-Lethal Weapons Directorate, says the energy beam is aimed at helping troops and police in confusing situations by offering options "between bullets and a bullhorn."
Marine Capt. Dan McSweeney, a spokesman for the Non-Lethal Weapons Directorate, pointed to "instances in Iraq where crowd situations have unfortunately ended in violence" and death.
Karcher and other military officials are trying to alleviate fears that the device might be misused to harm civilians or converted into a torture machine that leaves no marks.
In an attempt to anticipate how the world would greet the new weapon, the Air Force this month asked social science graduate students at the University of Minnesota and other colleges for help.
Researchers were offered $12,000 to spend the summer reviewing literature and assessing how Americans and other cultures might react to its use.
In the solicitation, Maj. Jonathan Drummond of the Air Force's Directed Energy Bioeffects Division noted that the Active Denial System could provide U.S. forces "with a nonlethal capability in military operations other than war." Among possible uses, he listed peacekeeping, humanitarian operations and crowd control.
Introduction of such a device in either noncombat or wartime situations could raise thorny questions: Would it be acceptable to inflict so much pain on unruly protesters? How would such a weapon be viewed if used on crowds in Third World countries? Would it violate international humanitarian principles if used in battle? Might it be used secretly during interrogations to torture suspected terrorists into cooperating?
Karcher said the Active Denial System "is absolutely not designed or intended or built" to be a torture device.
"To use this as any sort of torture device would be in direct violation of" the Pentagon's definition of nonlethal weapons, he said. "Nor, as professionals, would any of us sign up for it."