What do high powered non-heating microwaves feel like?

The event in Quantico, Virginia, was to be a rare public showing for the US Air Force's Active Denial System: a prototype non-lethal crowd-control weapon that emits a beam of microwaves at 95 gigahertz. Radiation at that frequency penetrates less than half a millimeter into the skin, so the beam was supposed to deliver an intense burning sensation to anyone in its path, forcing them to move away, but without, in theory, causing permanent damage. However, the day of the test was cold and rainy.

The water droplets in the air did what moisture always does: they absorbed the microwaves. And when some of the reporters volunteered to expose themselves to the attenuated beam, they found that on such a raw day, the warmth was very pleasant. A demonstration of the system on a sunny day this March proved more successful.

But that hasn't changed a fundamental reality for the Pentagon's only acknowledged, fully developed high-power microwave (HPM) weapon: no one seems to want it. Although the Active Denial System works (mostly) as advertised, its massive size, energy consumption and technical complexity make it effectively unusable on the battlefield. The story is much the same in other areas of HPM weapons development, which began as an East–West technology race nearly 50 years ago.