MAJ. WILLIAM (“PETE”) KNIGHT WAS in trouble, and he didn’t even know it. It was October 3,1967, and he had just set a world aircraft speed record of Mach 6.7 (6.7 times the speed of sound, or 4,520 mph) in a specially modified X-15 research plane flying at an altitude of 102,000 feet. As Knight approached the dry bed of Rogers Lake, at Edwards Flight Test Center in the Southern California desert, he found himself coming in fast and heavy. He was unable to jettison excess fuel, since the plane was carrying none, and he had no flaps to slow his touchdown speed. But X-15 pilots were used to tense situations. As Knight, today a California state senator, recalls, “I can probably count on one hand the number of flights we made where nothing happened in terms of an emergency, regardless of how big or small the emergency.”

But this time was different. During Knight’s highspeed run, shock waves had formed around a mockup of a “scramjet” test engine mounted on the X-15’s lower ventral fin. These shock waves had focused heat onto the undersurface of his airplane, raising its temperature to almost 3,000 degrees Fahrenheit. Despite the use of a special “ablative” paint designed to absorb heat and flake off, the heat had burned through the plane’s skin and spread up into the engine compartment, damaging vital components and leaving Knight seconds away from losing the hydraulic systems that operated his maneuvering controls. The aft end of the craft was severely weakened and in danger of disintegrating completely.

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