The ray gun, long a mainstay of science-fiction tales, may actually enter the American war-fighting arsenal in a few years. Engineers at several defense firms have conducted successful tests of key prototype components of truck-size "laser cannon" systems capable of firing a beam from aircraft, naval ships or armored vehicles to zap targets many kilometers away--even through intervening dust or fog.

High-power lasers--measured in hundreds to thousands of kilowatts--offer several advantages over conventional projectile weapons, according to Mark Neice, director of the Department of Defense's High-Energy Laser Joint Technology Office in Albuquerque, N.M. "They could provide ultraprecise, speed-of-light strike capabilities that could leave little or no collateral damage," he says.