The “X-15” on the back cover of the “American Space Digest” (1963), published by the Schick Safety Razor Company.

First flown in 1959, the North American X-15 bridged the gap between human flight in the atmosphere and spaceflight. It was the first winged aircraft to fly Mach 4, 5, & 6 and to operate at altitudes above 30,500 m (100,000 ft).

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