Weapons: Taking the Night from Charlie

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The faint moonlight barely penetrated the foliage as 15 U.S. infantrymen groped through black Vietnamese jungle near Lai Khe. But the night hid few secrets from 2nd Lieut. Robert Hibbs, 25, of Cedar Falls, Iowa. Although his own patrol was all but invisible in the dark, he had no trouble spotting the Viet Cong company approaching on his flank. Before he could withdraw, he picked up another group of V.C. moving in on him. Caught between two larger enemy forces, Hibbs ordered his men to fire a few rounds at the second Communist unit. Its gunners returned the fire, though they obviously could not see their targets, and the first V.C. company, convinced that it was under attack, also opened up—right at its buddies.

That jungle firefight took place more than two years ago, but it is still remembered as one of the first successful combat tests of the "starlight scope"—one of the prying electronic gadgets developed by the Defense Department "to take the night away from Charlie." Lieut. Hibbs was well briefed on the scope's importance; though mortally wounded, he smashed it against a tree rather than let it fall into the hands of the enemy. He won a posthumous Medal of Honor for his performance on that night patrol. Since then, thousands of starlight scopes have been shipped to Viet Nam; jungle-wise infantrymen are so impressed by their versatility that they use almost any G.I. dodge to pick up extra scopes for their outfits.

Last week the Army finally revealed some of the technical wizardry that makes the scopes work. Unlike the World War II infantry sniperscope that illuminated its target with an infra-red beam, the starlight scope needs no light of its own. Thus it is undetectable by enemy sensors. It uses only natural light, no matter how dim—moonlight, starlight, even the faint luminescence of decaying jungle foliage. Capable of amplifying light up to 40,000 times, it literally treats the darkest night as day.

Heart of the starlight scope is its image-intensifier tube, a sturdy combination of the home TV screen and miniaturized space-age electronics. Focused sharply by the scope's front lens, the slightest flickers of light are directed against a chemical film, causing it to discharge electrons. Boosted along by a 15,000-volt electrostatic field, those electrons smack into a phosphorcoated screen whose light then jars loose still another flock of electrons. The process is repeated three times, and the high-voltage electron acceleration, or energy buildup, produces a progressively brighter image. Besides the light, the only other power source is a tiny built-in battery for the electric field.