Science: 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...