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

(CNN) — If you’ve heard a soundtrack recently, you probably remember it. A loud bang like an explosion — caused by an airplane flying faster than the speed of sound — can be startling, even through windows.

Sonic shocks are one of the reasons why supersonic jets do not fly today, and one of the limiting factors in the success of Concorde, which last flew in 2003. Supersonic flight is limited to subsonic speed when flying over land and near coastlines. , and international regulations still limit ground-carrying speeds below Mach 1, or the speed of sound, to prevent sonic booms over space. stay

Now, NASA is working to change those rules by changing the boom to a “thump,” paving the way for a new generation of quiet supersonic jets. The company is working through a project called Quesst — for “Quiet SuperSonic Technology” — which is the result of many years of research and has been installed on a new aircraft called X- 59.

Thunder in the distance

The X-59 was the latest in a series of experimental aircraft including the X-1, which in 1947 became the first manned aircraft to exceed the speed of sound, and the X -15, which still holds the record for fastest. Human flight, set in 1967 at Mach 6.7.
Designed and built by Lockheed Martin in Palmdale, California, under a $247.5 million NASA contract, the X-59 is undergoing tests on the ground, awaiting a first flight later in 2022.

“It will be quieter than Concorde or any supersonic aircraft that exists today,” said Craig Nickol, program manager of the Quest program at NASA. “It’s very long and thin: it’s almost 100 feet long (30.5 meters), but has a wingspan of only about 29 feet.

The sleek design plays an important role in making the aircraft quieter when traveling supersonically.

How the X-59 looks in flight.

How the X-59 looks in flight.


But how does the soundtrack come about? When an airplane travels at subsonic speeds, the normally generated sound waves can travel in all directions; at supersonic speeds, however, the aircraft leaves its own sound behind and the sound waves merge into a single wave that radiates from the nose to the tail.

When this high frequency shock wave meets the human ear, it produces a loud sound, which does not occur when an airplane breaks the sound barrier, but is always an effect that can be heard by others. in a cone shape below the plane, although it is faster than the speed of sound.

The shape of the X-59 is designed to prevent shock waves from colliding. But they spread, with the help of carefully arranged aerodynamic layers. The single engine is located on the top rather than the bottom of the plane, to maintain a quiet low profile to avoid ground shock waves.

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

“What that means is that this plane might sound like distant thunder in the sky, or like someone slamming a car door in the corner,” Nickol said. People may not have heard the hill, and if they did, they would not be shocked, because it would be low and flat, not very big.

Change the rules

The most important part of the project will begin in 2024, when a series of test trips will be carried out in over half of the residential communities in the middle of the US, chosen to provide a unique combination of land and climate conditions: “It’s going to be a fun part of the project, because we’re going to engage with the public and stimulate citizen science,” said Nickol.

The design is reminiscent of an experiment conducted by the Federal Aviation Administration (FAA) in 1964, when supersonic fighter jets flew repeatedly over Oklahoma City to test the effects of sound waves. to the public.
It didn’t go well, with up to 20% of people protesting the booms and 4% filing complaints and damage claims. “We don’t want to do that again, of course, that’s why we’re going to test this plane at the first limit, to measure all the booms,” said Nickol. “Only when we are satisfied with the work, we will go out to the communities, and keep the level of sonic booms.”

When the X-59 flies over the designated areas, NASA will meet with communities in the country to see their response to the noise. The goal is to prove that a 75-decibel boom is acceptable.

The data collected in this way will be presented to the International Civil Aviation Organization (ICAO), which is in charge of the air traffic regulations, to persuade it to update them in an international conference organized scheduled for 2028.

A launch is planned before the end of the year.

A launch is planned before the end of the year.

Darin Russell/NASA

A new generation

NASA proposes a change in the rules to open the sky for a new generation of supersonic aircraft, allowed to fly over routes that are not currently allowed, such as New York to Los Angeles, and cut in flight time in half.

We still don’t know what those planes will be or who will build them, because the X-59 is not a prototype but just a technical demonstrator.

“Any future design of a low-altitude aircraft for supersonic flight will be very different from this one, although some of the design elements can be directly translated,” Nickol said, pointing to the long nose, one of the flight control systems, and the X-59’s unique external visual system, which provides the pilot with high-definition displays that show what is coming, including lack of a forward-facing window due to the nose of the aircraft.

Several companies are developing supersonic jets and plan to fly them within a year or less, including Hermeus, Boom and Spike. However, it is doubtful that any of them will be able to take advantage of the findings of the Quest project, which may lead to a new generation of supersonic aircraft.

Nickol believes that such planes, with the ability to fly anywhere, will set apart supersonic travel, marking a stark contrast with the glory of Concorde: “If you look back 100 years, Many advanced mobility technologies, including railways and airlines, started out as premium experiences, but as technology advanced and costs decreased, they became available to the public, “he said.

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

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