Texas Instruments knew nothing about designing bombs, so Word started with a standard-issue bomb—the 750-pound M-117, 638 of which already had been dropped unsuccessfully around the Thanh Hoa Bridge. He added a small set of wings that could direct the bomb’s flight as it fell from the sky. Finally, he installed a simple laser-guidance system that would control the wings. A small silicon wafer was divided into four quadrants and placed behind a lens. The laser reflecting off the target would shine through the lens onto the silicon. If the bomb veered off course, one quadrant would receive more
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