High Tech on the High Frontier

By Frederic Golden.

Scientists explore killer lasers and particle-beam weapons

Imagine a nuclear-tipped missile rising from a silo deep inside the Soviet Union, fixed on a target in the U.S. Almost immediately its fiery exhaust plumes trip warning sensors in satellites orbiting overhead. One of those satellites sends a powerful beam of light, or perhaps even a cascade of subatomic particles, bursting down from the heavens like a Jovian lightning bolt. The beam homes in on the ascending missile and fastens onto its nose cone. Burning through, the beam turns the electronic guidance system into silicon mush, sending the missile wobbling off course and totally immobilizing its nuclear warhead. As it plunges back into the atmosphere, no longer protected by the nose cone, most of the missile incinerates in the sizzling heat of reentry. Only a few harmless fragments reach the ground.

The Soviets fire off other missiles. But again and again, the killer beam appears almost miraculously out of the skies, destroying one rocket after another. The Kremlin is so frustrated that it calls off its multimegaton attack.

When President Reagan last week urged U.S. scientists to develop new high-tech defensive weaponry, this scenario was the sort of thing that he had in mind. It is called directed-energy weaponry and has two main forms: high-energy lasers (HEL) and charged-particle beams (CPB). In the current fiscal year, the Pentagon is spending $1 billion to test the feasibility of these weapons schemes. By all indications, the Soviets are spending even more, perhaps three to five times as much.

What makes these weapons so attractive to strategic planners, at least in theory, is that their "bullets" travel many times faster than even the highest-velocity conventional rockets. In the case of lasers, which send off beams of highly concentrated light of a single frequency (or color), the speed is that of Light itself, about 186,000 miles per second. That means the beam arrives at its target literally in a flash. If a missile were traveling at, say, six times the speed of sound (4,400 m.p.h. at sea level), it would have moved only nine feet before a laser beam arrived from 1,000 miles away. High-velocity beams of charged particles would be harder to create. Unlike the massless photons that make up light beams, charged particles (those parts of the atom that carry an electronic charge; electrons most likely would be used in a missile-killing beam) have weight. But, as in the beams used in atom smashers, they could be "energized" in strong magnetic fields to velocities approaching the speed of light.

Because beam weapons are largely unaffected by the tug of gravity, they could be aimed straighter than the proverbial arrow. In space, laser beams would have almost infinite range, as NASA showed when it bounced laser light off small mirrors left behind by the Apollo astronauts on the moon. (At lower altitudes, laser beams, like any light, are readily diffused by clouds and even fog.) Charged particles, on the other hand, would be influenced by the effects of the earth's magnetic field. But researchers are working on machines that shoot particles with no electrical charge, like simple hydrogen atoms, whose trajectory would be unaffected by magnetism.

Such "high frontier" weaponry, as its proponents like to call it, faces enormous technological obstacles. "The theoretical physics for all this is pretty sparse," concedes Robert McCrory, director of the Laboratory for Laser Energetics at the University of Rochester. Victor Weisskopf, professor emeritus at M.I.T., judges that it is a pipe dream.

A laser or particle beam must dwell on its speeding target for more than an instant before it can destroy it. Only a slight wavering in the beam will spread the energy sufficiently over the target so as to blunt the destructive impact. Hence, the beam must be aimed over thousands of miles with truly pinpoint accuracy. That may eventually be possible, thanks to high-speed computers and the spotting ability of new infrared (or heat) detectors. But to date, lasers have been consistently effective only on relatively slow-moving targets. For example, a laser was turned successfully on wire-guided antitank missiles, traveling at a relatively poky 500 m.p.h., as part of an experiment near San Juan Capistrano, Calif, a few years ago.

Another important obstacle is the relatively large power plant needed to generate laser beams. The San Juan Capistrano beam packed only 300 watts, hardly more powerful than a household appliance, yet it required a station as big as several freight cars. Even the space shuttle's large payload bay could not heft such a package into orbit.

No doubt lasers are becoming smaller and more efficient. U.S. Air Force researchers have carried a five-megawatt laser system aboard an aircraft and fired beams at air-to-air missiles speeding across the skies at several thousand m.p.h. Only a few of the targets, however, were downed. On the eve of the President's speech, Air Force officials told a House subcommittee about an unspecified "major breakthrough" in lasers of short wave lengths, possibly high-energy X rays or gamma rays.

Even if a laser weapon could be parked in space, it would not necessarily be an invulnerable Battlestar U.S.A. It would be susceptible to attack from even primitive antisatellite weaponry: at orbital speeds (17,000 m.p.h.), it could be demolished in a collision with an object only a fraction of its weight. The debris and electromagnetic storm from the detonation of a small nuclear weapon also could do the trick.

But even if laser and particle-beam weapons are distant long shots, they bear further examination. "If the potential is there," McCrory says, "we must in our own interests pursue it, if only to find out what our adversaries may be doing." --By Frederic Golden. Reported by Jerry Hannifin/Washington and Bruce van Voorst/New York

With reporting by Jerry Hannifin/Washington, Bruce van Voorst/New York This file is automatically generated by a robot program, so viewer discretion is required.