NASA’s X-59 supersonic aircraft, capable of “quietly” breaking the sound barrier, will soon take off.

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The X-59 QueSST developed by NASA and Lockheed Martin (Quiet SuperSonic Technology) is a very special supersonic aircraft: as the name suggests, it is designed to break the sound barrier more quietly than any other existing supersonic craft. The first test flights should take place in the next few months; if successful, they could lead to supersonic commercial flights like Concorde from 1976 to 2003.

Sound is a wave of compressed air traveling from point A to point B at a speed of 340 meters per second. When a ship flies at subsonic speeds, it creates sound waves that propagate (longitudinally) in all directions. But when an airplane flies at supersonic speeds, it travels faster than the sound waves it creates; the air molecules can’t get out of their way fast enough, so the pressure waves combine to form a large shock wave that travels down to the ground, where it meets the human ear and creates the famous “bang.” This blast can sometimes exceed 100 decibels (about 105 dB for Concorde)!

This disturbing noise, which harms both humans and animals, is one of the reasons why supersonic commercial flights did not achieve the expected success – recall that Concorde, operated by only two companies, was influenced mainly to avoid exposure to transatlantic flights. affects the population a lot. To this day, international regulations still limit the speed of commercial transport over land to below Mach 1. The X-59 was designed to fly at Mach 1.4, but was specially designed not to make disturbing noise.

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Ready for “acoustic verification”.

Coupling of sound waves should be avoided to limit the sound boom. Any significant change in shape in the fuselage (usually the nose and tail of the aircraft) can generate a shock wave. Therefore, it was necessary to change the shape of the plane in order to “smooth out” these changes in shape as much as possible. ” we want to keep [les ondes de choc] parallel and separated from each other so that they do not combine into a loud boom “, explains CNET Larry Cliatt, technical manager of acoustic tests for the X-59 at NASA.

As a result, the machine is quite long and thin: its length is almost 30.5 meters, the wingspan is a little less than 9 meters. The nose is a distinctive feature of this aircraft: it is about a third of the length. As a result, thanks to two video cameras located above and below the plane and high-definition screens, the pilot can see what is in front of him (the nose is too long and rational to be equipped with a traditional cockpit window). A single engine, a General Electric Aviation F414-GE-100, sits in the rear; it contains 22,000 pounds of kinetic energy.

This special shape prevents the waves generated in the nose of the device from combining with the waves generated in the tail. Result: the explosion felt on the ground should not exceed 75 dB. According to NASA, that’s about as loud as slamming a car door on the street. ” People may not even hear the boom, and if they do, they certainly won’t be afraid, because it will be low and diffuse, not so loud. adds Craig Nicol, senior adviser at NASA Headquarters.

Purpose: to change the regulation

The X-59 is a simple technology demonstrator (not a prototype). In its current form, it cannot carry any passengers. “TAny future design of a low-boom supersonic commercial aircraft will undoubtedly differ from the X-59, although some design elements may be directly carried over. “, Nicole notes.

Once the X-59’s performance and “stealth” are confirmed, a series of test flights are planned for half a dozen residential areas in the United States by 2024. geographical and atmospheric conditions. The aim is to verify that a ceiling of 75 dB is considered acceptable by the population – a condition sine qua non to consider a return to supersonic passenger transport.

The collected data will then be submitted to the International Civil Aviation Organization, which is responsible for regulating aircraft noise. If NASA’s noise-cancellation measures are found to be effective, the rules could change at an international meeting scheduled for 2028. The X-59 could pave the way for a new generation of supersonic jets. A flight from Los Angeles to New York at Mach 1.4 will take only 2.5 hours (compared to 5 hours at standard speed).

And unlike the Concorde, which was designed for a fairly wealthy clientele, Nicole believes supersonic devices will soon be available to a wider audience. ” If you look back 100 years, many advanced mobility technologies, including railroads and airplanes, started out as high-end experiments, but as technology advanced and costs came down, they became available to the general public. he told CNN. According to David Richardson, director of Lockheed Martin’s X-59 program, general public flights could take place in 2035.

Source: NASA

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