A plane can indeed break the sound barrier. While not all aircraft possess this capability, certain specialized planes are engineered to exceed the speed of sound.
What the Sound Barrier Is
The sound barrier is not a physical wall, but a set of aerodynamic challenges an aircraft faces as it approaches and exceeds the speed of sound. The speed of sound, also known as Mach 1, is approximately 767 miles per hour (1,235 kilometers per hour) at sea level, though it varies with temperature and altitude. As an aircraft moves through the air, it creates pressure waves, similar to how a boat creates waves in water.
At subsonic speeds, these pressure waves travel ahead of the aircraft, “warning” the air of the plane’s approach. As the aircraft accelerates and nears Mach 1, it begins to catch up to its own pressure waves. These waves compress and pile up in front of the aircraft, forming a single, intense shock wave. This compression leads to a sharp increase in aerodynamic drag, turbulence, and changes in air pressure, temperature, and density around the aircraft.
The Sonic Boom Explained
When an aircraft travels faster than the speed of sound, it continuously generates shock waves that extend outward and rearward in a cone-shaped pattern, similar to a boat’s wake, resulting in a sonic boom, an impulsive noise comparable to thunder, heard on the ground as the shock waves reach an observer. The characteristic “boom” is caused by the sudden onset and release of pressure after the buildup from these shock waves.
The intensity and path of a sonic boom are influenced by several factors, including the aircraft’s physical characteristics, altitude, and flight path. A higher altitude results in a lower overpressure on the ground, making the boom less intense, though it will spread over a wider area. The size and shape of the aircraft also play a role, with larger aircraft creating stronger shock waves. Observers on the ground hear the boom as a brief, sudden event.
Why Some Planes Can and Others Cannot
Achieving and sustaining supersonic flight demands specific design principles that differentiate supersonic aircraft from their subsonic counterparts. Supersonic planes, such as military fighter jets and the retired Concorde, feature long, slender bodies with sharp, pointed noses and swept-back or delta-shaped wings. This streamlined design minimizes air resistance, particularly a strong form of drag that significantly increases as an aircraft approaches and exceeds the speed of sound. These aircraft also require powerful engines to generate the substantial thrust needed to overcome this increased drag and accelerate through the transonic regime.
Conversely, most commercial airliners and general aviation aircraft are designed for fuel efficiency and optimal performance at subsonic speeds. Their blunter noses, larger fuselages, and broader, less swept wings are optimized for lift and economy, not for piercing the sound barrier. The structural integrity and materials of subsonic aircraft are not built to withstand the extreme pressures, temperatures, and aerodynamic stresses encountered during supersonic flight. Civil supersonic flight over land has been restricted in many areas, including the United States, primarily due to the disruptive noise of sonic booms, making such designs impractical for widespread commercial use.