Free Republic

Decades before the rumored SR-72 “Darkstar,” America had already conquered hypersonic flight with the X-15 rocket plane. In 1967, this remarkable experimental aircraft, developed by North American Aviation, reached a stunning speed of Mach 6.7, a record for a crewed, powered aircraft that remains unbroken to this day.

When Robert White shot through the sky in a rocket-powered X-15 airplane nearly 50 years ago, he earned a place in the development of America's space program that those in the field still talk about. First to break Mach 4 — four times the speed of sound. First to break Mach 5. First to break Mach 6 —more than 4,000 miles per hour. All in a few short months in 1961. Then in 1962 the young test pilot with Hollywood good looks nosed his airplane 59 miles above the earth to be the first to take a winged craft into...

In the cockpit of the sleek, black aircraft slung underneath the wing of the B-52 bomber, my interphone crackles. "Ah, Robert, it’s a lovely morning," says Jack Allavie, the commander of the B-52 launch aircraft. "Yes it is, Jack," I respond while running through the preflight checklist for our July 17, 1962 mission. The North American Aircraft X-15 was designed to investigate flight at hypersonic (Mach 5-plus) speeds and extremely high altitudes, and the effects of aerodynamic heating on aircraft surfaces. It was the first aircraft to fly Mach 4, Mach 5, and Mach 6—and I had the good fortune...