cnn
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If you've heard a sonic boom recently, you probably remember it. The loud, explosion-like bang caused by a plane flying faster than the speed of sound can be startling and even shatter windows.
Sonic booms are part of the reason there are no supersonic airliners flying today, and one of the limiting factors to the success of the Concorde, which last flew in 2003. The supersonic airliner was restricted to subsonic speeds when It flew over land or near the coast. , and current international regulations still limit the speed of commercial land transportation to below Mach 1, or the speed of sound, to avoid disruption from sonic booms over inhabited areas.
Now, NASA is working to change those regulations by transforming the boom into a “hit,” paving the way for a new generation of quieter supersonic aircraft. The agency is doing this through a program called Questt, which is the result of decades of research and focuses on a new aircraft called the X-59, which debuted Friday.
The X-59 is the latest in a series of experimental aircraft that include the X-1, which in 1947 became the first manned aircraft to exceed the speed of sound, and the fastest ever built. manned flight, set in 1967 at Mach 6.7.
The new spacecraft was designed and built by prime contractor Lockheed Martin Skunk Works in Palmdale, California, under a $247.5 million NASA contract. Once the factory launch is completed, the X-59 will undergo integrated systems testing, engine performance and taxiing tests in preparation for first flight. It is scheduled to take off for the first time later this year, ahead of its first silent supersonic flight.
“In just a few years we have gone from an ambitious concept to a reality. “NASA’s X-59 will help change the way we travel, getting us closer in much less time,” NASA Deputy Administrator Pam Melroy said in a statement.
“It will be significantly quieter than Concorde or any other supersonic aircraft that exists today,” Craig Nickol, senior advisor at NASA Headquarters, told CNN in 2022. “It is extremely long and thin: it is almost 100 feet long ( 30.5 meters), but It has a wingspan of only about 29 feet. The nose is a distinctive feature of this aircraft: it measures approximately one-third of its length.”
The sleek shape plays a key role in making the aircraft much quieter when traveling supersonically.
But how is a sonic boom produced? When an airplane travels at subsonic speeds, the sound waves it normally creates can travel in all directions; However, at supersonic speeds, the plane will leave its own sound behind and the sound waves will be compressed and merged into a single shock wave that originates in the nose and ends in the tail.
When this highly compressed shock wave reaches the human ear, it produces a loud boom, which is not produced when the plane breaks the sound barrier, but is a continuous effect that can be heard by anyone in a shaped area. cone under the plane. as long as it exceeds the speed of sound.
The shape of the X-59 is designed to prevent shock waves from coalescing. Instead, they expanded with the help of strategically placed aerodynamic surfaces. The single engine is also at the top rather than the bottom of the plane, to maintain a smooth bottom profile that prevents shock waves from reaching the ground.
As a result, NASA believes the X-59 will produce only 75 decibels of sound when traveling at supersonic speeds, compared to the Concorde's 105 decibels.
“What that means is that this plane can sound like distant thunder on the horizon, or like someone closing a car door around the corner,” Nickol says. “It may even be that people won't hear the boom at all, and if they do hear it, they certainly won't be surprised, because it will be low and widespread, and not that loud at all.”
The expectation is that the X-59 will fly at 1.4 times the speed of sound, or 925 mph. Before that, the Quest team will conduct several flight tests at Lockheed Martin Skunk Works before transferring the aircraft to NASA's Armstrong Flight Research Center in Edwards, California, which will serve as its base of operations.
The crucial part of the program will begin later in 2024, when a series of test flights will be conducted in a half-dozen residential communities across the United States, selected to offer a diverse mix of geographic and atmospheric conditions: “It's going to be fun. part of the project, because we are going to engage with the public and generate a little citizen science,” Nickol said.
The plan is reminiscent of an experiment conducted by the Federal Aviation Administration (FAA) in 1964, when supersonic fighter jets repeatedly flew over Oklahoma City to test the impact of sonic booms on the public.
It didn't go well: up to 20% of people opposed the booms and 4% filed complaints and claims for damages. “Of course, we don't want to repeat that, so first we're going to test this aircraft in a restricted range, measuring all the feathers,” Nickol says. “Only when we are satisfied with the performance will we go into the communities and continue to carefully monitor the level of sonic booms.”
Once X-59 flies over selected areas, NASA will interact with communities on the ground to evaluate their response to noise. The goal is to confirm the theory that a 75-decibel boom will be acceptable.
The data collected in this way will then be presented to the US Federal Aviation Administration and international regulators.
NASA believes a change in regulations would open the skies to a new generation of supersonic planes, which would be allowed to fly on routes that are not allowed now, such as from New York to Los Angeles, and would reduce flight time by about to the half.
However, we do not know what those aircraft will be like and who will build them, because the X-59 is not a prototype but simply a technology demonstrator.
“Any future design of a low-boom commercial airliner for supersonic flight will certainly be different from this one, although some of the design elements could be carried over directly,” Nickol said, pointing to the extended nose, some of the flight control systems and the The X-59's unique external vision system, which provides the pilot with high-definition displays showing what's ahead, in the absence of an actual forward-facing window due to the aircraft's streamlined nose.
Several companies are currently developing supersonic airliners and plan to fly them within a decade 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 Questt program, which will likely serve as the basis for the next generation of supersonic aircraft.
Nickol believes that this type of aircraft, with the ability to fly anywhere, would democratize supersonic travel, marking a marked difference from the luxury status of the Concorde: “If you look back 100 years, many of the advanced mobility technologies, including railways and airplanes, started out as premium experiences, but as technology advanced and costs dropped, 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 it can't happen.”
