Electronic Duck Hunter

The Army's new Skysweeper antiaircraft gun, first shown last week, does not look human--but it acts human in a baleful way.

When no hostile airplanes are about, the gun squats quietly waiting, its 75-mm. tube projecting out of a mass of electronic equipment. On top, a small, dish-shaped radar antenna peers around, scanning the hemisphere of sky. It can see 15 miles through clouds or darkness.

Suddenly it stops and stares, and a little, tonguelike organ in the center of the dish vibrates with fierce excitement. Somewhere, far beyond human sight, it has spotted an enemy jet diving down from the edge of space at close to the speed of sound. It stares intently for a second or so; then with a roar of gears and motors, the gun springs to life. While its carriage whirls and its tube swings upward, the radar still stares at the target. It acts uncannily like a hunter who squats in his blind and watches the sky for ducks. When he glimpses one over his shoulder, he springs to his feet and trains his gun. The Skysweeper sees better than any human hunter, and it swings its ten-ton mass as nimbly as a shotgun.

All the Answers. Designed by the Sperry Gyroscope Co., the Skysweeper is the highest point so far in the development of radar-controlled guns. When the radar is locked to a target, an electronic computer figures out the target's distance, speed, direction and course. It knows all the answers and can swing the gun so that any shell fired from it will intercept the course of the target in midair. The actual firing can be done either automatically--at the rate of 45 rounds a minute--or by one of the crew. The shells have proximity fuses that explode them as soon as they feel hardware ahead.

Army Ordnance experts explain that the Skysweeper is not intended for knocking down high-altitude bombers. It was designed as a tactical weapon to protect troops and installations from fast, low-flying jets, which it can pick off at any altitude up to four miles.

Mechanical Falcons. Larger guns for use against high-flying bombers may eventually be equipped with the same sort of automatic control, but some antiaircraft experts believe that bombers flying eight miles up cannot be shot down dependably by any sort of gun. The shells take a long time to reach such heights. They may be deflected from their courses by unknown winds, or the target may turn.

What projectiles need for these long voyages is steerability and an opportunity to change their minds at the last moment. That means guided missiles "vectored" toward the targets by electronic signals, and equipped with homing devices that sense the target ahead and turn the projectile toward it in a collision course at several times the speed of sound. The domain of these mechanical falcons is the high, thin air above the sweep of the Skysweeper.

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