On Sunday, residents of the Washington D.C. area heard a sonic boom, a sound that has a long history in North American aviation. This sound was produced due to six fighter jets that the US military sent to catch up and intercept a business jet whose pilot was unresponsive. The civilian aircraft was flying in restricted airspace with a pilot and three passengers.
Sonic booms occur when an aircraft flies faster than the speed of sound, typically 760 mph (1,223 km/h) near sea level. As the aircraft accelerates, it pushes air molecules aside with great force, forming a shock wave, much like a ship’s wake on water. When this wave reaches the ground, a loud bang is heard.
Test pilot Charles “Chuck” Yeager became the first person to fly faster than sound in 1947 aboard an orange Bell X-1 rocket plane. Initially, interest in supersonic flight was primarily focused on military aircraft, but interest grew to include supersonic civilian aircraft in the 1960s.
NASA researched the effects of sonic booms and found that those who heard it were very unhappy with the noise, describing it as “annoying,” “irritating,” and “alarming.” The Federal Aviation Administration banned supersonic flight in 1973 based on the expectation that such flights would cause a sonic boom upon reaching the ground.
The Concorde, an Anglo-French supersonic airliner, was successful for several years but its sonic booms prompted restrictions on where the plane could fly. It was ultimately discontinued in 2003 due to profitability challenges and the restrictions.
Although sonic booms are still heard today due to military aircraft, there has been a resurgence of interest in supersonic jets. Startups are hopeful that new technology could make them quieter and more cost-effective. However, not all industry watchers believe they will be profitable.
NASA has claimed that its X-59 aircraft is capable of flying faster than sound but causing drastically reduced noise over the ground. People below would hear sonic “thumps” instead of explosions, if they hear anything at all, according to a publication from the aeronautics agency in a blog post in April.