1947: Capt. Charles E. “Chuck” Yeager pilots the rocket-powered Bell X-1 to a speed of Mach 1.07, becoming the first person to fly faster than the speed of sound. In breaking the sound barrier, Yeager becomes the fastest man alive — and the legend of the X-Planes begins.
As airplanes flew faster and faster throughout the 1930s, pilots began to experience a number of problems associated with the increased airspeed. Aircraft such as the Lockheed P-38 and Republic P-47 flew just fine at ordinary speeds in level flight. But if pilots put them in a high-speed dive, they began to experience control problems that led to the deaths of several pilots.
The main problem facing these pilots was the aerodynamic condition known as compressibility. Simply stated, at speeds well below the speed of sound, most of the air molecules have time to get out of the way of an aircraft as it approaches, and the density of the air does not change.
However, as the speed of sound is approached, the air molecules can’t get out of the way, and more of them hit the aircraft. The impact compresses the air in front of the aircraft and increases the air density. Eventually shock waves form around the airplane, affecting the lift and drag. These changes were not well-understood and led to the loss of control in several aircraft.
Because the effects of compressibility are directly related to the speed of sound, a ratio is used to describe the speed of an aircraft. The Mach number is the speed at which an object is traveling relative to the speed of sound at a particular temperature. The name is in honor of physicist Ernest Mach, who studied high-speed gas dynamics.
The Bell X-1 was developed to research aerodynamics in the transonic region, or speeds just below and just above the speed of sound. After numerous flights with civilian test pilots, Capt. Yeager of the newly formed U.S. Air Force made his first powered flight in the X-1 on Aug. 29, 1947, high over the Mojave Desert of southern California.
The problem Yeager was experiencing was the ineffectiveness of the X-1’s pitch controls, as shock waves essentially created an aerodynamic shadow around the tail. Changes were made to the horizontal tail controls, allowing Yeager to control the airplane's ability to pitch up and down, and flights continued. This knowledge would lead to the all-flying tail, or stabilator, standard on all supersonic fighters today.
Yeager was nursing two broken ribs on the morning of Oct. 14, after being thrown from his horse on a ride the night before. He boarded the B-29 bomber that was to carry the Bell X-1 to altitude. The plan was to fly to Mach 0.97. But Yeager says the new moving tail boosted his morale, and he wanted to fly faster.
After climbing down into the X-1, which was carried like a bomb in the belly of the B-29, Yeager’s friend and fellow test pilot Jack Ridley handed him a short, sawed-off section of broomstick. Yeager would use it to close the canopy of the X-1, because his broken ribs prevented him from closing the latch normally.
People on the ground heard what sounded like distant thunder. It was the first sonic boom ever created by an aircraft. At age 24, Yeager had flown faster than the speed of sound.
The flight was kept secret, and the world wouldn’t know about the first supersonic flight until months later. The X-1 would fly more than a hundred more times, reaching a speed of Mach 1.45.
Subsequent X-1 models would fly more than twice the speed of sound. Later X-Planes would fly even faster, reaching hypersonic speeds where the density of the air wasn’t the only thing to change: They would fly so fast, the chemistry of the air would change.
Capt. Yeager would go on to become Gen. Yeager and the iconic test pilot. He was the first commandant of the Air Force’s test-pilot school and continued commanding fighter squadrons into the 1960s.
Now age 86, Yeager will return this Saturday to the skies over the Mojave desert. He'll make a now-routine supersonic flyby to kick off Edwards Air Force Base’s air show and open house.