Achieving Supersonic Flight
By Anthony Mohr
Before 1947, many experts thought it was impossible to fly an airplane faster than the speed of sound. However, they were proven wrong when Chuck Yeager, a young pilot from West Virginia, blasted the rocket engines on his X-1 aircraft, and—with an enormously loud sonic boom—broke the sound barrier.
To understand how impressive this accomplishment was, we need to answer an important question: why is it called the sound “barrier” in the first place? First of all, think about an airplane that’s motionless on the ground. As its engine rumbles, it produces sound waves. These waves travel outward from the engine in all directions.
How fast do these waves move? While sound waves move faster in solid objects than in the air, the speed of sound in the air is nothing to laugh at. At room temperature, it’s around 760 miles per hour! It’s hard enough to build an aircraft that can accelerate to a speed anywhere near that. However, if you’re a pilot and you manage to fly close to the speed of sound, an extra challenge awaits you: you start to catch up with the sound waves that your own plane has created! Now you’re flying at nearly the same speed as your own sound waves, and as a result, the waves push on your plane and make it harder to control and accelerate. This is why the speed of sound is called a barrier.
While many experts doubted that any aircraft could push past this wall of sound, a group of determined engineers at Bell Aircraft Company believed they could design the right airplane for the job. They started with the shape of a .50-caliber bullet, an object that was clearly capable of breaking the sound barrier. They applied this shape to aircraft designs. The result was the X-1, their new rocket-powered airplane that they believed could achieve supersonic flight.
Flying the X-1 past the sound barrier was not a simple task. It needed a pilot that was calm, skilled, and not afraid to take risks. The rising star Chuck Yeager volunteered to be the test pilot. Yeager came from humble beginnings: he grew up in a tiny and poor town in West Virginia, and he lacked any college education. However, he had proven his natural talents in World War II, where he was a pilot in the Army Air Forces. He was skilled in dogfights and emerged victorious in many difficult situations. One time, he even survived being shot down and having to evade enemy forces in German-occupied France! Yeager’s training and experiences made him the perfect test pilot. On October 17, 1947, he performed the special flight—the flight where he broke the sound barrier and became the fastest pilot in history.
When Yeager broke the sound barrier, observers below heard and felt a giant boom. It was the first major sonic boom in human history. A sonic boom is not a singular blast of noise. It’s actually a continuous shock wave that lasts as long as the plane is flying above the speed of sound. Its effects can be severe: the sound is thunderously loud, and it can even shatter windows! This is why the US government has banned supersonic flights over populated areas. However, some organizations like NASA and United Airlines have proposed designs for supersonic airplanes that could have less impactful sonic booms. Maybe in the future, you will be able to board an airplane and travel above the speed of sound between continents. If that’s the case, you will have Chuck Yeager and the X-1’s engineers to thank for leading the way.