Science: Snap III

On President Eisenhower's desk stood a domed metal gadget about half the size of a derby hat. Current flowing from it spun a small propeller. Named SNAP III (for System for Nuclear Auxiliary Power), the little gadget is an atomic battery small and light enough to go into a satellite and keep its instruments and radio voice going at least ten times as long as any chemical battery that the Russians or the U.S. have yet employed.

SNAP III's heart is a pinpoint one-hundredth of an ounce of radioactive polonium 210 encased in a molybdenum capsule. The polonium's entrapped radiation heats the...

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