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Getting To Mach 6.07: A Look Into Testing the X-15 Rocket Plane


Getting To Mach 6.07: A Look Into Testing the X-15 Rocket Plane

Mach 6.70 is the top speed reached by the North American X-15. In fact, it’s the fastest manned rocket plane that has ever been. That’s 4,520 miles per hour, which was achieved by William Knight in 1967 while flying X-15A-2. To compare, the fastest air-breathing aircraft, a Lockheed SR-71 Blackbird, officially topped out at half that speed, and only unmanned test vehicles have exceeded that figure (the Boeing X-51 Waverider unmanned scramjet vehicle was able to push over Mach 5, while the DARPA HTV-2 hypersonic glide vehicle has seen Mach 20. But the X-15 deserves a closer look for two reasons: one, there was a human in the nose who was in control, and two, this is the closest thing to a manned Hellfire missile in existence. Over the course of ten years and 199 flights, the X-15 was utilized to understand and investigate piloted hypersonic flight, which was to be used in the space exploration programs up through current day. Twelve pilots flew the X-15…five came from NASA, five from the U.S. Air Force, one from the U.S. Navy, and one from North American. And all of them got an E-ticket ride to brag about.

The launch of an X-15 went like this: it would be connected to the wing of a Boeing B-52 Stratofortress and would be flown to about 45,000 feet in altitude and up to about 500 miles per hour. When dropped, the first minute or two was under powered rocket flight from a throttable Thiokol XLR-99 anyhydrous ammonia/liquid oxygen rocket that could push out 57,000 pounds of thrust and the remainder was glided down to a dry lake bed, where the X-15 landed on an unsteerable front bogey and skids in the back.  During flight, the X-15 would shed almost 20,000 pounds in weight as the fuel burned away. Once the flight was over, a section of the tail of the aircraft would drop away and parachute to the ground and the skids would extend.

Mach 6.7. And people thought the Concorde’s Mach 2.04 figure was impressive.


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