Flying together over the California desert one day last week were two Delta-wing jet fighters (above), both called F-102 and both powered by the J 57 engine. One looks straight and trim, the other oddly pinched in the middle. One has a short nose, the other a long one. But their dif-ferences are not mere differences of shape. The F-102 at left, though planned to go faster than sound. cannot. The F-102A at right can, and with a top speed of more than 900 mph is fast becoming a mainstay of U.S. air defense. How it got that way is the story of the greatest advance in aviation since man first broke the sound barrier. That advance, a discovery only recently disclosed, is called the Area Rule which, in effect, puts an airplane's bumps and indentations in the right places. Its effect is to change the shapes of planes like the F-102 and push them smoothly through the sound barrier, the dangerous wall of shock waves which jets ordinarily cannot penetrate without great bursts of extra power. How it works is described on the next page. Area Rule literally saved the F-102. After turning out what they were convinced would be a supersonic fighter, Convair designers discovered it would not even reach the speed of sound. Gambling on the then unproved theory of Richard Whitcomb, 34-year-old engineer of the National Ad-visory Committee for Aeronautics, the designers reworked the F-102 to give it a pinched waist, longer nose and a bulged tail. On its first try the new F-102A slipped smoothly into supersonic speed while still climbing.
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