An aircraft flying roughly twice the speed of sound could take off in New York City and land in Los Angeles in just two hours. The technology to travel at this speed exists, but in 1973 the Federal Aviation Administration (FAA) issued a complete ban on civil supersonic aviation over all US land and territorial waters, a ban that remains in effect to this day.
The issue is noise. As an airplane reaches the speed of sound (Mach 1 or 660 mph at high altitude, air waves produced at the plane's nose are compressed, generating a shock wave that is known as a sonic boom because of the explosive noise it creates in the planes wake.
The Concorde, the supersonic passenger jet developed in the 1960s by the United Kingdom and France, for example, produced a sonic boom as loud as 135 decibels when it reached land, comparable to the noise level 100 feet from a jet engine. Many decades have passed since the Concorde's milestone transatlantic flight in 1969.
A new generation of supersonic plane designs takes advantage of 50 years of advances in materials science, aerospace engineering, and computer simulation techniques to substantially reduce the loudness of the sonic boom.
In 2012, for example, a team of NASA-funded researchers reported results from wind tunnel tests in which scale model aircraft produced sonic booms perceived to be as quiet as 79 decibels, similar to the noise created by a car passing 10 feet away. |