by David Noland
Experimental and Spy Planes: Bell X-1
A plane that went faster than the speed of sound
On October 14, 1947, legendary test pilot Chuck Yeager became the first man to fly faster than Mach 1, the speed of sound. He was piloting the Bell X-1, a bullet-shaped rocket plane that was the first in a series of secret high-speed research aircraft. The X-planes came to symbolize the danger and glamour of test flying at California's Edwards Air Force Base in the late 1940s and 50s.
Originally known as the XS-1, the X-1 was powered by a Reaction Motors XLR11-RM3 rocket engine. Its four chambers each produced 1,500 pounds of thrust. At full power, the engine burned up its 600-gallon supply of liquid oxygen and alcohol fuel in less than three minutes.
Ferried by a B-29 Bomber
Because of its limited endurance, the X-1 had to be lifted to an altitude of 20,000 feet under the belly of a converted B-29 bomber. It then dropped free and fired its rocket engine. After running out of fuel, the X-1 would glide down for a dead-stick landing on Muroc Dry Lake.
The advantages of swept wings for supersonic flight were as yet unknown, so the X-1 had straight, very thin wings. The shape of its fuselage was modeled after a .50 caliber machine-gun bullet. To maintain its bullet shape, the X-1's cockpit canopy was flush with the fuselage, which severely limited visibility.
An unusual design feature of the X-1 was its all-moving horizontal tail, which could be adjusted up and down, or "trimmed." This turned out to be critical when Yeager found that the X-1's elevator control became useless above Mach 0.94. The trimmable tail served as an impromptu backup pitch control as the X-1 flew through the sound barrier and into the history books.
During 157 test flights from 1946–51, the X-1 achieved a maximum speed of Mach 1.45 (957 mph) and an altitude of 71,902 feet, both world bests at the time. The X-1A, a later version with larger fuel tanks and an improved cockpit, reached 1,650 mph and 90,000 feet.
Three X-1s were built. The Mach-busting aircraft, which Yeager named "Glamorous Glennis" after his wife, is currently on display in the National Air & Space Museum in Washington D.C. The No. 2 aircraft, which was later modified and renamed the X-1E, can be seen at Edwards AFB. The third aircraft exploded on the ground in 1951 and was destroyed.
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