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"In the nineteen-nineties... the Pentagon demanded the impossible. They wanted a jet that could defy the laws of aerodynamics and the limits of metallurgy. An aircraft that could break the sound barrier... and then... stand perfectly on air. To the engineers at the time, these two requirements were a physical contradiction. Aviation experts said the math simply didn't add up. You could have a supersonic needle... or a hovering brick. But you couldn’t have both.