X-15

The North American X‑15 was a rocket‑powered research aircraft built in the late 1950s as part of a joint program between the United States Air Force, the Navy, and NASA. Developed by North American Aviation, the sleek, wedge‑shaped vehicle measured 50 feet in length, had a wingspan of 22 feet and was constructed largely of stainless‑steel honeycomb to withstand the extreme heating of hypersonic flight. Powered by a Reaction Motors XLR99‑3 engine delivering 57,000 pounds of thrust, the X‑15 could climb to altitudes above 100 kilometers and reach speeds of Mach 6.7 (about 4,500 miles per hour). Between 1959 and 1968, twelve pilots performed 199 flights, gathering data on aerodynamic heating, control at near‑space conditions, and high‑speed propulsion. The program produced vital insights that shaped the design of later spacecraft, including the Mercury, Gemini, and Apollo capsules, and later influenced the Space Shuttle’s thermal‑protection system. The X‑15 remains the only piloted aircraft to have crossed the Kármán line, cementing its legacy as a bridge between atmospheric flight and space exploration. Its record‑setting flights demonstrated the feasibility of reusable, high‑mach, high‑altitude platforms, inspiring modern hypersonic programs worldwide.

North American Aviation

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