NASA intends to break the sound barrier in a new way that is free of the negative effect of the sonic boom. If successful, this would pave the way for the return of faster-than-sound passenger planes.
Seventy-five years ago, the sound of breaking the sound barrier was heard for the first time over the California desert. On October 14, 1947, the X-1 team, consisting of engineers and pilots from NASA, the United States Air Force, and Bell Aircraft Corporation, broke the sound barrier – an invisible wall in the sky that some said was impossible to overcome. Aerospace innovators from NASA’s Quesst mission are ready to break the sound barrier entirely differently. Their success could lead to the widespread adoption of technology that would one day allow us to travel by plane at supersonic speeds (1.5 times faster than the famous Boeing 737).
NASA will demonstrate and test the X-59 aircraft as part of the Quest mission. It should be capable of flying at supersonic speeds without generating typical loud sonic booms that led to the ban on supersonic flights over land in 1973. The plan includes flying the X-59 over several communities to study how people react to the aircraft’s quieter “sonic thumps” generated – if they can hear them at all. Their responses will be reported to regulatory agencies, which will consider lifting the ban based on collected data. If the plan succeeds, it will be another historic milestone in aviation, potentially ushering in a new era in air travel where airline passengers can board a supersonic jet for breakfast in Los Angeles and make lunch reservations in New York.
Commercial supersonic aircraft have already had their moment in history. The most famous of these was the Concorde. Reaching a cruising speed of 2.02 Mach (approximately 2150 km/h) allowed for a more than 50% reduction in travel time on the transatlantic route! The Concorde reached a maximum speed of 2.04 Mach: about 2270 km/h. In 1973, the cost of operating the Concorde aircraft became too high, making their use unprofitable, and they were retired in 2003. Nevertheless, research on supersonic flights continued, planes pushed the speed limit more elevated, and increasingly sophisticated computers, measurement systems, and research tools in wind tunnels enriched scientists’ knowledge. As a result, researchers better understood how planes created sonic booms and developed a methodology to reduce their intensity by manipulating the shape of the aircraft.
„Remember that the pain threshold for humans is 120dB, and previous technology generated over 100dB of noise during supersonic flight. Polish regulations from the Ministry of Environment from October 15, 2013, regarding permissible environmental noise levels caused by takeoffs, landings, and aircraft overflights cannot exceed a maximum of 60 dB. For comparison, a vacuum cleaner generates a noise level of 60dB during household cleaning. Each increase of 3dB on a logarithmic scale means doubling sound intensity. Therefore, the difference between the noise from a vacuum cleaner and a supersonic aircraft is as much as 40dB, which means it is 10,000 times louder.”
Paweł Cała CAE-EM Engineer Endego
Currently, the biggest obstacle to supersonic flight is the need to limit speed due to the negative effect of sonic noise. Silencing the boom was tested in flight as part of the NASA Shaped Sonic Boom Demonstration program from 2003-2004. It used the Northrop F-5E jet, which was modified to minimize the volume of sonic booms based on research and simulation results regarding the shape of the fuselage. It was successful, and the technology was improved and implemented in the X-59 aircraft. Knowledge gained since the X-1 first proved that exceeding the speed of Mach 1, which is about 1225 km/h (approximately 340m/s!), is possible. NASA hopes that with the X-59 and its quiet supersonic technology, it will be possible to provide the aviation industry and passengers worldwide with the technology and capabilities for flight faster than sound. The first flight of the X-59 is planned for early 2023. We are eagerly awaiting it.
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