Why U.S. Bombing Is More Accurate Now

WITH uncanny accuracy, U.S. flyers are now selectively knocking out targets in North Viet Nam that defied destruction during the massive American bombing of four and five years ago. What makes the difference is a new generation of so-called "smart" bombs, with highly sophisticated electronic guidance systems, which can be launched a mile away from the target. As a result, despite the improvement of North Viet Nam's air defenses, the U.S. is losing fewer planes while destroying more targets. In the past two weeks alone, smart bombs have enabled U.S. flyers to take out a number of heavily defended targets in North Viet Nam with a loss of only six planes. Among the targets: the North Vietnamese air-combat communications center near Hanoi, six bridges on the northwest rail line, five petroleum pumping stations and a number of power stations.

There are two basic types of smart bombs--those guided by television and those led by laser beams. TV bombs, like the Navy's 3,000-lb. Walleye (so named for the glassy lens in its snout), can be dropped from an altitude of 30,000 ft., far above the reach of most antiaircraft artillery. As the bomb glides toward the target on a free-falling trajectory, the pilot, who monitors the flight on a television receiver, can adjust its course by remote control, or the bomb, having "memorized" the picture of the target with its built-in electronic brain, can aim itself for a direct hit. The Walleye is employed mainly against bridges and other large targets. An even more sophisticated "EO" (electro-optical) missile called the Maverick has a rocket booster, which enables it to maneuver, so that it can fly into caves where North Vietnamese have hidden artillery pieces and other essential military supplies.

Laser-directed bombs usually require the coordination of at least two aircraft: one circles above and trains a pencil-thin beam of laser light on the target, while the other drops its bombs in the general direction of the object. Responding to infra-red sensors mounted in their noses, the bombs ride the beam's reflections in a long glide pattern to the target. Sometimes they strike within a 5-ft. radius of the bull's-eye.

Some U.S. aircraft are now being outfitted with laser "projectors" that train the beam for the plane's own bombs to follow. There are also infra-red bombs that home in on the heat of tank or truck engines.

Dropped from high altitudes--rather than on the low-level runs that were necessary to ensure accuracy for unguided "dumb" bombs--the new armaments have made the war far less perilous for American pilots. They also have given flyers the assurance that they can eliminate military targets without the fear that their bombs may fall wide of the mark.

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