X-59: NASA’s quest to build a ‘quiet’ supersonic plane

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(CNN) — If you’ve heard Sonic Boom lately, you probably remember it. A loud, explosion-like blast — caused by a plane flying faster than the speed of sound — can be startling and even shatter windows.

The sonic boom is part of the reason no supersonic passenger planes fly today, and one of the limiting factors for Concorde’s success. Which last flew in 2003. Supersonic airliners were limited to subsonic speeds when flying over land or near coastlines, and current international regulations still limit the speed of commercial transport on land to Mach 1, or below the speed of sound, to avoid sonic boom disruption over populated areas. .

Now, NASA is working to change those rules by transforming the boom into a “thump,” paving the way for a new generation of quiet supersonic aircraft. The agency is doing so through a program called QUEST — for “quiet supersonic technology” — which is the result of decades of research and centers around a new aircraft called the X-59.

A distant roar

The X-59 is the latest in a series of experimental aircraft that includes the X-1, which in 1947 became the first manned aircraft. Exceeding the speed of soundAnd X-15which still holds the record for the fastest human flight ever, set in 1967 at Mach 6.7.
Designed and built by Lockheed Martin in Palmdale, California under $247.5 million NASA AgreementThe X-59 is currently undergoing ground tests in anticipation of first flight in 2022.

“It will be significantly quieter than Concorde or any other supersonic aircraft that exists today,” says Craig Nicol, project manager of the Quest program at NASA. “It is extremely long and thin: it is about 100 feet long (30.5 m), but its wingspan is only 29 feet. The nose is a distinctive feature of this plane: it is about a third of the length.”

The sleek shape plays a major role in making the aircraft quieter when traveling supersonically.

How the X-59 might look in flight.

How the X-59 might look in flight.

cr103.com/NASA

But how does a sonic boom happen? When an aircraft travels at subsonic speeds, the sound waves it normally creates can travel in all directions; At supersonic speeds, however, the aircraft will leave its own sound behind and the sound waves will compress and coalesce into a single shockwave that originates at the nose and ends at the tail.

When this highly compressed shockwave meets the human ear, it produces a loud boom, which does not occur when the plane breaks the sound barrier, but is a continuous impact that can be heard by anyone in the cone-shaped area below the plane, as long as it exceeds the speed of sound. go

The shape of the X-59 is designed to prevent the shock waves from collapsing together. Instead, they spread with the help of strategically placed aerodynamic surfaces. The single engine is also on the top rather than the bottom of the plane, to have a smoother lower profile that prevents shock waves from reaching the ground.

As a result, NASA estimates that the X-59 will produce only 75 decibels of noise when traveling at supersonic speeds, compared to the Concorde’s 105 decibels.

“That means this aircraft can sound like distant thunder on the horizon, or someone slamming a car door around the corner,” says Nicol. “It could also be that people don’t hear the boom, and if they do they certainly won’t be startled, because it will be low and spread out, and not that loud.”

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Changing rules

The critical part of the program will begin in 2024, when a series of test flights will be conducted over more than half a dozen residential communities in the US, chosen to provide a diverse mix of geographic and atmospheric conditions: “That will be the fun part. For the project, Because we’re going to connect with people and produce some citizen science,” says Nicole.

The scheme is reminiscent of an experiment conducted by the Federal Aviation Administration (FAA) in 1964, when a supersonic fighter jet Flew frequently to Oklahoma City to test the effect of sonic booms on people.
It did not go well with about 20% of the people opposition Boom and 4% to file complaints and damage claims. “We don’t want to repeat that, of course, which is why we’re going to test this aircraft on a restricted range first, measuring all the booms,” says Nicol. “We will only go into communities when we are satisfied with the performance, and still carefully control the level of sonic booms.”

Once X-59 flies over selected areas, NASA will connect with communities on the ground to gauge their response to the noise. The goal is to confirm the theory that a 75-decibel boom would be acceptable.

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The data thus collected will then be presented to the International Civil Aviation Organization (ICAO), which is responsible for aircraft noise regulations, to be persuaded to update it at an international meeting scheduled for 2028.

The first flight is planned before the end of the year.

The first flight is planned before the end of the year.

Darin Russell/NASA

A new generation

NASA believes the rule change will open the skies to a new generation of supersonic aircraft, allowing them to fly routes that are no longer allowed, such as New York to Los Angeles, and cut flight times by nearly half.

However, we don’t know what the aircraft will look like and who will build it, as the X-59 is not a prototype but only a technology demonstrator.

“Any future design of a low-boom commercial aircraft for supersonic flight will certainly be different from this, although some elements of the design may translate directly,” Nicol said, pointing to an extended nose, some flight control systems and flight control systems. The X-59’s unique external vision system provides the pilot with a high-definition display showing what lies ahead, in the absence of an actual forward-facing window due to the aircraft’s streamlined nose.

Several companies are currently developing supersonic passenger aircraft and plan to fly them within a decade or less, including Hermes, Boom And Spike. However, it is doubtful that any of them will be able to take advantage of the findings of the Quest program, which will potentially inform the next generation of supersonic aircraft.

Nicol believes that such an aircraft, with the ability to fly anywhere, would democratize supersonic travel, which contrasts starkly with Concorde’s luxury status: “If you look back 100 years, a lot of modern mobility technologies began, including railroads and airplanes. . as premium experiences, but as technology advanced and costs came down, they became available to the general public,” he says.

“One of the long-term goals is to make this form of high-speed travel available as a widespread application, and there’s really no reason why that can’t happen.”

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