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Supersonic flight is not a novel concept, but it has piqued a certain interest over the past few years thanks to new developments from NASA. Dubbed as ‘low-boom’ - their new X-59 QueSST aircraft promises to deliver speeds up to Mach 1 .4 with significantly reduced acoustic disturbance. The affectionately named “boomlets” should be no more audible than a quiet thump; compared to the hugely explosive sound of a traditional sonic boom.
What is Supersonic Flight?
The term “supersonic” refers to any object which travels faster than the speed of sound. In air, this is a whopping 760 mph. When an aircraft exceeds this speed, it is traveling faster than the sound waves it produces, forcing them to coalesce into a single shock wave traveling at the speed of sound - Mach 1. The intensity of the sonic boom depends on various factors, but some have been recorded over 200 dB. Supersonic flight has been around since the 1960s and is generally associated with military aircraft. Due to the noise impact of such aircraft, there are heavy restrictions on overland flight paths making them an unpopular candidate for commercial use. Concorde operated for just under three decades as a commercial airliner but was eventually discontinued due to concerns over safety, and the high costs associated with meeting environmental restrictions; amongst other things.
Lockheed Martin X-59 QueSST
In April 2018, NASA awarded aviation corporation Lockheed Martin a $250 million contract to design, build and deliver the new ‘Low-Boom’ jet. At first glance, the aircraft looks decidedly unconventional. The body is shy of 97 feet in length, with a wingspan of just 29 feet. Thanks to significant developments in computational fluid dynamics, each aspect of this aircraft has been designed to produce a jet so aerodynamically balanced that observers at ground level should hear nothing more than a soft thump, as the aircraft surpasses Mach 1. The clunky droop-nose of Concorde is to be replaced by external sensors and 4K camera for the pilot, to keep the body as streamlined as possible. The long, narrow airframe and canards are designed to keep the shockwaves from coalescing, and should theoretically produce a boom of no more than 75 PLdB (Perceived Level decibel) - similar to the closing of a car door.
Early “Low-Boom” Simulations
In November 2018, NASA test pilots flew F/A-18 fighter jets over a designated area off the coast of Texas. Performing a special dive maneuver, the sonic boom produced was louder at sea, but significantly reduced over land. Although the results from the resident survey are still being collated, NASA hopes that these early simulations will help to give the green light to their 2021 projected flight date. With these early flight demonstrations, NASA has been able to feed useful data to U.S. and international aviation regulators surrounding supersonic travel over land. It is hoped that this data could help to lift certain bans and regulations; should they be able to prove that minimal disturbance is perceived in residential and built-up areas.
Is the Future of Commercial Air Travel?
In short - no. Or at least - not yet. The X-59 QueSST is a one-seater aircraft; designed only to demonstrate the possibility of Low Boom Flight. NASA project that supersonic craft such as this could reduce flight time from Houston to Dubai from 15 hours to just 8.5 hours in total. The X-59 itself is still being manufactured, and although this model will never carry passengers; it could indeed give rise to a new generation of commercially viable supersonic aircraft.
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