A sensation of unbearable, sudden heat seems to come out of nowhere -- this wave, a strong electromagnetic beam, is the latest non-lethal weapon unveiled by the US military this week.

"You're not gonna see it, you're not gonna hear it, you're not gonna smell it: you're gonna feel it," explained US Marine Colonel Tracy Taffola, director the Joint Non-Lethal Weapons Directorate, Marine Corps Base Quantico, at a demonstration for members of the media.

The effect is so repellant, the immediate instinct is to flee -- and quickly.