Bringing Back Supersonic Flight

Throughout history, humans have always strived to go faster and break barriers. The sound barrier is marked by the speed of sound at sea level—about 767 miles per hour. During World War II, pilots reported that their aircrafts tore apart approaching the speed of sound—as if they were hitting an invisible barrier. This led to multiple attempts to break the barrier—one such example with the development of the Bell X-1. Piloted by Chuck Yeager, the X-1 surpassed the speed of sound in 1947 and demonstrated that going beyond the sound barrier was possible. This milestone—along with advances in jet engine technology—paved the way for larger and faster aircraft. 

 In flight, an airplane pushes aside the air molecules in front of its nose—much like how the bow of a boat pushes water to create waves. As the plane’s speed increases, shockwaves occur closer together. These shockwaves move away from the plane at the speed of sound. Therefore, as the aircraft surpasses the speed of sound, the waves are unable to catch up with their point of origin at the nose. This causes the shockwaves to trail behind the plane, forming a cone shape known as a “Mach cone”. The collision of this cone and the ground creates sonic booms, which can reach approximately 110 decibels in intensity—similar to the noise made by jackhammers. The intensity is great enough to lead to permanent hearing damage in humans and animals.

The breaking of the sound barrier caused the emergence of a competition to design and produce a supersonic passenger aircraft. Russian company Tupolev manufactured the first supersonic transport—the Tupolev-144 (TU-144). The TU-144 first flew on December 31, 1964. Shortly after, the British Aircraft Corporation and Sud Aviation—a French state-owned aircraft manufacturer—designed the Concorde, which took its first flight on March 2, 1969.

Design and production of supersonic transports by multiple companies designing raises the question of why there are none implemented in service today. The TU-144 was retired in 1999 due to a lack of market for supersonic passenger planes in the Soviet Union. The Concorde achieved temporary success and was flown by both British Airways and Air France. However, due to the auditory intensity of sonic booms, the U.S. government and other countries issued a ban on civilian supersonic flights over land. This significantly limited flyable routes and confined airlines operating the Concorde to only flying over the Atlantic Ocean. The Concorde remained in service until 2003 when it was retired because of expensive operation costs since it consumed 32.5 liters of fuel per second. 

In recent years, NASA and Lockheed Martin have begun to design the supersonic experimental aircraft X-59 QueSST. The goal of the QueSST is to achieve a lower shockwave intensity of 75 PLdB—perceived level decibels—comparable to the sound of closing a car door. NASA aims to reverse the U.S. government ban on supersonic flight over land by demonstrating that supersonic flight can be quiet. Its design features a 38 foot nose and slim body that spreads out the shockwave it generates, which lowers the shockwave’s strength. By smoothing the underbelly and placing features like the engine intake and cockpit on top, these features can direct shockwaves upward and further reduce the intensity of the shockwave. Due to the need for such a smooth nose, the QueSST cannot have a front windshield. Instead, the plane utilizes a high-definition camera system that is integrated seamlessly into the cockpit. Additionally, the QueSST’s unique T-shaped tail creates a shockwave that interferes with and cancels out the primary shock, diminishing its strength. While the QueSST is not designed for commercial use, elements such as its high-definition camera system, T-tail, and nose can be implemented into future supersonic transports.

As companies such as Boom Aerospace forge ahead with the development and testing of supersonic airliners such as the XB-1 demonstrator and the upcoming Overture supersonic airliner, the prospect of bringing back supersonic commercial travel is becoming a reality. Plans for the Overture to enter service as early as 2029 and partnerships with major airlines including United Airlines and American Airlines make the resurgence of supersonic air travel seem imminent.