It sounds like science fiction a heat ray that can zap rioting protesters, forcing them to flee without inflicting injuries. But the U.S. military's Active Denial System which shoots a beam of electromagnetic radiation, causing its target to experience a burning sensation is just the latest attempt to make crowd control more effective yet less lethal. Unlike traditional brute-force methods of dispersal such as rubber bullets and batons, which can maim or even kill a new wave of hi-tech crowd-control gadgets promises to keep the peace without causing casualties.