Good-bye nasty tear gas. So long risky rubber bullets. Welcome to the wonderful world of electromagnetic weaponry. In March, the PR-conscious Pentagon proudly unveiled what is supposed to be the perfect nonlethal crowd control device--a high-powered energy beam that can disperse an unruly mob without killing, maiming or harming anyone. Military brass are touting it as the biggest breakthrough in war technology since the nuclear bomb.

Known officially as a "Vehicle-Mounted Active Denial System," this new weapon is said to be more humane and more effective than other methods of controlling a large crowd or stopping aggressive intruders dead in their tracks. Here's how it works. A special transmitter fires two-second bursts of focused microwave energy that causes a burning sensation on the skin of people up to 700 yards away. But no one gets fried and no telltale burn marks linger on the body because the beam only penetrates just beneath the skin's surface at a depth of 1/64th of an inch. Targets of this concentrated electromagnetic pulse briefly experience intense pain and confusion. "It's safe, absolutely safe," said Col. George Fenton, who demonstrated the new gadget in March at the Pentagon's nonlethal weapons center in Quantico, Virginia. "You walk out of the beam and the pain goes away. There are no lasting effects."

The actual zapper, which looks something like a backyard satellite dish mounted on top of an armored car, is still in the experimental phase. Handheld and aircraft-mounted applications are also on the drawing board.

Thus far, 10 years of research and $40 million have been devoted to this project, which critics have likened to a militarized version of a microwave oven. Developed by the Raytheon Corporation and several other Defense Department contractors, it is currently being field-tested on soldiers at the Kirkland Air Force Base in New Mexico. But it is not expected to be ready for deployment by troops for at least five years.

Zap-happy Pentagon strategists envision using the "Active Denial System" in various operational settings where a small number of American troops or military police might be confronted by a horde of angry civilians. Border patrols, "peacekeeping" missions, urban riots and domestic disturbances have been flagged as situations in which such a device could prove handy. Best of all, it won't result in bloody television images of people shot and mutilated by conventional arms.

But before you start feeling warm and fuzzy all over at the prospect of a benign alternative to guns and bombs, consider the fact that past attempts by the U.S. military to create so-called nonlethal weapons have resulted in some monumental fiascos. During the late '50s, Major Gen. William Creasy, chief officer of the U.S. Army Chemical Corps, waxed enthusiastic about a new kind of "psychochemical" weapon that would revolutionize combat. He imagined aircraft swooping down over enemy territory, releasing clouds of hallucinogenic "madness gas" that would disorient people and dissolve their will to resist. According to Creasy, a nonlethal incapacitating agent such as LSD could subdue a foe without inflicting permanent injury.

Testifying before Congress, Creasy maintained that psychochemical warfare was not only feasible but tactically advantageous for certain difficult operations, such as dislodging enemy soldiers from a city inhabited by an otherwise friendly population--a busy industrial center, for example, with numerous museums and cultural landmarks. Why blow everything to smithereens with an old-fashioned artillery barrage if you can spike the city's water supply with LSD or disseminate an aerosol hallucinogen? Those under the spell of madness gas would become helplessly giddy, spaced-out, and incapable of fighting back while U.S. troops established themselves on once-forbidden turf. Victory would be a foregone conclusion. Just blow their minds, move in and take over.