LONDON  Stories of the soldiers who operate the Arctic radar stations and stand in front of the transmitter to get warm will surely be repeated now that the U.S. Department of Defense has gone public with plans to use the heating effect of millimeter waves within a weapon.

The U.S. Marine Corps says it has developed a 95-GHz system as an antipersonnel “heat ray” and is conducting tests on animals and volunteers.

The supposedly nonlethal weapon, called “active-denial technology,” has been in the works for the last 10 years at the Air Force Research Laboratory (Kirtland, N.M.), in tandem with the Marine Corps' Joint Non-lethal Weapons Directorate. About $40 million has been spent developing the weapon, according to the Air Force Research Laboratory (AFRL), although it could be nearly another decade before it is used in conflict. The earliest estimate for deployment is 2009.

The system includes a millimeter-wave energy source with waveguides to direct the energy to a dish antenna measuring about 3 x 3 meters, which forms a beam that can be swept across a battlefield or hostile crowd. The aim is to deter or drive off adversaries caught out in the open with a beam that inflicts pain without causing permanent damage.

According to an AFRL fact sheet, the 95-GHz energy penetrates 1/64 inch into the skin and produces an intense burning sensation that stops when the transmitter is switched off or when the individual moves out of the beam.

Top skin layer takes heat

“It works by heating the water molecules in the top 1/64-of-an-inch layer of the skin,” said Marine Corps spokesman Maj. David Andersen.

According to reports, a 2-second burst from the system can heat the skin to a temperature of 130° F. Elsewhere, the AFRL describes the sensation as similar to touching an ordinary light bulb that has been left on for a while. “Unlike a light bulb, however,” says the AFRL fact sheet, “active-denial technology will not cause rapid burning, because of the shallow penetration of the beam and the low levels of energy used.”

Beam size, whether it is a convergent, focused beam or a divergent beam, and its range are all classified information.

“This is a beam that is going to be directed. It's not harmful to internal organs because it doesn't penetrate the skin beyond 1/64 of an inch,” said Conrad Dziewulski, a spokesman for the directed-energy division of AFRL. “It will be swept across the battlefield or directed at an individual for a few seconds.”

Dziewulski said the system was intended to protect military personnel against small-arms fire, which is generally taken to mean a range of 1,000 meters. Elsewhere, the system is described as having a range of 700 yards.

While early tests have been carried out using a fixed antenna, the military now plans to develop a mobile version of the system, otherwise known as Vehicle Mounted Active Denial System, or Vmads.

AFRL said Vmads could be mounted on a High Mobility Multipurpose Wheeled Vehicle (more commonly referred to as a Humvee). Later it could be mounted on other vehicles such as aircraft, helicopters and ships, officials said.

However, countermeasures against the weapon could be quite straightforward  for example covering up the body with thick clothes or carrying a metallic sheet  or even a trash can lid  as a shield or reflector. Also unclear is how the active-denial technology would work in rainy, foggy or sea-spray conditions where the beam's energy could be absorbed by water in the atmosphere.

The technology was developed by two Air Force Research Laboratory teams: one from the laboratory's Directed Energy Directorate at Kirtland Air Force Base, and the other from the Human Effectiveness Directorate at Brooks Air Force Base, Texas.

The Air Force's Electronic Systems Center at Hanscom Air Force Base, Mass., will manage acquisition of the Humvee Vmads system.