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Commercial supersonic aircraft could return to the skies.

Flying faster than the speed of sound still sounds futuristic to normal people, more than 15 years after the last commercial supersonic flights ended. The planes that made those trips, the 14 planes known collectively as Concorde, that is, from 1976 to 2003. They traveled three times faster than regular passenger planes, but the airlines made no profit on their trips.

The reason why the Concorde was not profitable was, in fact, a side effect of its speed. When the plane spits out the speed of sound, at about 760 mph, the shock waves created in the air hit the ground with a loud and sudden noise: a "sonic boom". It is as alarming for people on the ground as the United States. Federal regulations prohibit all commercial aircraft from flying faster than the speed of sound on land.

Those rules, and the amount of fuel the plane could carry, effectively limited the Concorde to transatlantic flights. Operating the plane was so expensive that a one-way ticket between London and New York could cost more than $ 5,000. And the Concorde flew often with half of its seats empty.

The main benefit of supersonic travel is the reduction in flight time. A three-hour flight across the Atlantic could make a one-day trip possible from the US. UU To London or Paris, essentially a saving of a whole day. As an aerospace engineer studying high-speed air vehicles, I believe that recent advances in technology and new trends in commercial air travel could make supersonic flight economically viable. But regulations will have to change before civilians can cross the skies faster than sound.

<div data-thumb = "https://3c1703fe8d.site.internapcdn.net/newman/csz/news/tmb/2019/1-commercialsu.jpg" data-src = "https: //3c1703fe8d.site.internetcdn. net / newman / gfx / news / 2019/1-commercialsu.jpg "data-sub-html =" As an airplane accelerates, it accumulates a front of air pressure by pushing the air in front of it. behind the wake of a ship, forming a sonic sound wave. Chabacano / Wikimedia Commons, CC BY-SA">

<img src = "https://3c1703fe8d.site.internapcdn.net/newman/csz/news/800/2019/1-commercialsu.jpg" alt = "Commercial supersonic aircraft could return to the skies” title=”As an airplane accelerates, it accumulates a front of air pressure pushing the air in front of it. When the speed of sound passes, the pressure follows behind the wake of a ship, forming a sonic sound wave. credit: Chabacano / Wikimedia Commons, CC BY-SA“/>

As an airplane accelerates, it accumulates a front of air pressure pushing the air in front of it. When the speed of sound passes, the pressure follows behind the wake of a ship, forming a sonic sound wave. Credit: Chabacano / Wikimedia Commons, CC BY-SA

Overcoming the boom

When a plane flies through the air, it creates pressure disturbance waves that travel at the speed of sound. When the aircraft is flying faster than sound, the disturbances are compressed into a stronger disturbance called a shock wave. The shock wave patterns around supersonic aircraft were recently photographed in NASA experiments. When a supersonic airplane flies overhead, some of the shock waves can reach the ground. This is the sonic boom, which is experienced as a dull thud.

Commercial flights are regulated in the United States. by the Federal Aviation Administration. To protect the public from sonic explosions, current FAA regulations prohibit the flight of any commercial aircraft at supersonic speed.

However, NASA is working to significantly reduce the sonic boom in its X-59 program. With careful configuration of the aircraft, the objective is to weaken the shock waves or prevent them from reaching the ground.

The sonic sounds can be quite strong.

With flight demonstrations scheduled to begin in 2021, success in the NASA project could eliminate an important barrier to supersonic flight.

Noisy on the floor, too

My father took me to see that the Concorde took off in the early 1970s, and what I remember after all these years is noise. Today, I recognize that the noise of landing and takeoff at airports is a second barrier for supersonic aircraft. Airport noise is also regulated in the United States. by the FAA, and the current rules require supersonic aircraft to meet the same airport noise standards as subsonic aircraft. The Concorde was so strong, however, that it had to be given an exception to those rules.

The latest subsonic aircraft use very large jet engines that offer high fuel efficiency. These engines also reduce airport noise by accelerating to larger volumes of engines lower than smaller engines. The new engines are so quiet that regulators have been able to reduce the amount of noise aircraft can make since Concorde stopped flying.

A promotional video from NASA shows the first images of a supersonic airplane that produces a much quieter sonic boom than the Concorde.

Those standards are now much harder to measure for supersonic aircraft. This is because supersonic aircraft can not use large new engines, which considerably increases the resistance at high speed. That, in turn, requires more fuel to be transported by the plane and burned in flight, which is both heavy and expensive. Essentially, in the design of supersonic plans, a compromise must be found between noise and efficiency.

Positive developments

However, some recent innovations for airport noise reduction in subsonic aircraft will also result in reductions for supersonic vehicles compared to the 1960s design of the Concorde. These advances include the use of chevrons in jet engine nozzles to reduce jet noise by more effectively mixing engine gas with external air flow.

In addition, with the improved speed and accuracy of computer simulations, it is now easier to explore new fuselage designs that reduce noise.

In addition to the technological advances since the Concorde was withdrawn, there have also been important changes in the patterns of commercial air travel. Specifically, there has been a significant increase in the use of commercial businesses and their ownership by wealthy individuals. Therefore, a promising approach for the reintroduction of supersonic commercial aircraft is the development of small business aircraft. This is the approach that Aerion is taking.

Updating the rules.

Technology and market forces are making supersonic aircraft more acceptable and more affordable, but the relevant aviation rules have changed since the Concorde era. In its 2018 Reauthorization Act, the FAA must review regulations for supersonic aircraft in the sonic boom and airport noise.

Commercial supersonic aircraft could return to the skies.

The Chevron shapes around the engine exhaust nozzles reduce aircraft noise. Credit: John Crowley / Wikimedia Commons, CC BY-SA

Recently, the current U.S. The administration indicated that it wishes to change the rules to facilitate the supersonic commercial flight. An important first step is for the FAA to simplify the process for testing supersonic aircraft.

In my opinion, the current total ban of any flight over land at a supersonic speed is too restrictive. Airplanes flying at low supersonic speeds do not generate a significant boom. And, the NASA X-59 project can result in supersonic aircraft with many more booms. Instead of completely banning booms, it would be better to set maximum boom levels, to balance the benefits of supersonic flight with noisy detractors.

Aerion is developing a supersonic business in collaboration with Boeing and Lockheed Martin.

In addition, I believe that the current airport noise rules, which require supersonic aircraft no more than subsonic aircraft, impose an unreasonable burden on the developers of supersonic aircraft. First, as mentioned above, the Concorde provides a precedent for making a special case for supersonic aircraft. Second, for many years after its initial reintroduction, the total number of supersonic aircraft leaving any airport will be a small fraction of all traffic. For example, a study conducted for Aerion indicated potential sales of 30 supersonic aircraft per year for 20 years in the small business market. Regulations must adapt to what supersonic aircraft technology can reasonably offer and what airport communities will tolerate.

The momentum is building up through changes in technology and the market that can return the supersonic commercial flight, if the regulations are maintained. While at first it may be affordable for only a few, the experience gained in the development and operation of these aircraft will inevitably lead to new innovations that will lower ticket prices and open up the opportunity faster than the speed of sound to a wider section of society.

NASA captures unprecedented images of supersonic shockwaves

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