With new airframe designs being developed for the more powerful jet engines, the years following World War II became a Golden Age for the rocketplane. The epicenter of rocketplane research was Edwards Air Force Base, California. Unlike the strictly subsonic German rocket gliders, the new American vehicles were built for supersonic speeds and high-altitude research. Their goal was to test the limits of aeronautics at those speeds and altitudes, and to test the handling characteristics not only at those limits but throughout the entire flight envelope.
The Bell X-1 (1946-1958)
It took a rocketplane to break the sound barrier. The Bell XS-1 (Fig. 1.7), piloted by US Air Force Captain Chuck Yeager, accomplished this feat on October 14, 1947. His rocketplane, nicknamed Glamorous Glennis after his wife, was modeled
on a .50-caliber machine gun bullet, with stubby wings attached (Fig. 1.8). The X-1 program was a joint effort between the National Advisory Committee for Aeronautics (NACA) and the United States Air Force (USAF). The Experimental Sonic XS-1 burned ethyl alcohol and liquid oxygen (LOX) in its four-chamber 6,000-lb thrust (sea level static) XLR-11 rocket engine, but it could not take off by itself, which would have wasted precious propellant. Instead, a modified B-29 bomber (Fig. 1.9) carried the little rocketplane under its wing and released it at 21,000 ft, where it ignited its engines and flew into history. Other airplanes had flown faster than sound during high-speed dives, but the X-1 was the first to do so in level flight. Progressing through five different versions culminating in the X-1E, this rocket-powered pioneer made a total of 238 test flights from the mid-1940s until the late 1950s.67
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