X-15 number 56-6670 flew 81 missions, including the last eight of the program. It reached a speed of 4,104 mph (Mach 6.06), and an altitude of 266,500 feet. Eric Long/NASM Inconel X, a ferociously ...

The X-24C was to take the lessons learned during the X-15 and X-24B projects, with the expectation that the X-24C would be ...