A supersonic commercial plane could go back in the air

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Beat the boom

When an airplane is flying in the air, it creates pressure disturbance waves that propagate at the speed of sound. When the aircraft flies itself faster than sound, the disturbances are compressed into a stronger perturbation called shock wave. Shock wave patterns around supersonic aircraft have recently been imaged during NASA experiments. When a supersonic aircraft flies over, some of the shock waves can reach the ground. That's the sound boom, which is felt like a deafening noise.

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

However, NASA is working to dramatically reduce the sonic boom of its X-59 program. By carefully shaping the aircraft, the goal is to weaken shock waves or prevent them from reaching the ground.

Flight demonstrations to begin in 2021, the success of the NASA project could eliminate a significant obstacle to supersonic flight.

Noisy on the floor too

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

The latest subsonic aircraft use very large reactors with very high energy efficiency. These engines also significantly reduce airport noise by accelerating a larger volume of air at a lower speed than smaller engines. The new engines are so quiet that regulators have twice been able to reduce the noise that aircraft have been allowed to make since Concorde stopped flying.

These standards are now much more difficult to meet for supersonic aircraft. Indeed, supersonic aircraft can not use the new large engines, which greatly increases the drag at high speed. In turn, this requires transporting more fuel on board the aircraft and burning it in flight, which is both cumbersome and expensive. In the design of supersonic aircraft, a compromise must be found between noise and efficiency.

Positive developments

However, some recent innovations in subsonic aircraft noise reduction at airports will also reduce the number of supersonic vehicles compared to the 1960s Concorde design. These advances include the use of chevrons on jet nozzles of jet engines. to reduce jet noise by more efficiently mixing the engine gas with the outside air flow.

In addition, with the improved speed and accuracy of computer simulations, it is now easier to explore new designs of noise-reducing cells.

In addition to the technological advances made since the Concorde's retirement, significant changes have occurred in commercial air transport models. In particular, there has been a significant increase in the use of commercial business jets and their property by high net worth individuals. Thus, a promising approach for the reintroduction of a supersonic commercial aircraft is to develop small business jets. This is the approach adopted by Aerion.

Update rules

Technology and market forces make supersonic aircraft more acceptable and affordable, but aviation rules have not changed since the Concorde era. In its 2018 Reauthorization Act, the FAA is required to review the regulation of supersonic aircraft on aircraft noise and airport noise.

The current US administration has recently announced its intention to change the rules to facilitate supersonic commercial flights. An important first step is to simplify the FAA's testing of supersonic aircraft.

In my opinion, the current total ban on flying over the ground at a supersonic speed is far too restrictive. Aircraft flying at low speed supersonic do not generate a big boom. In addition, the NASA X-59 project could lead to the creation of supersonic devices with much weaker arrows. Rather than completely prohibiting booms, it would be better to set maximum boom levels, in order to counterbalance the benefits of supersonic flight with noisy annoyances.

In addition, I believe that the current airport noise rules, which require supersonic aircraft to be no stronger than subsonic aircraft, impose an unreasonable burden on supersonic aircraft developers. First, as mentioned earlier, the Concorde sets a precedent for the creation of a special case for supersonic aircraft. Secondly, for many years after their initial reintroduction, the total number of supersonic aircraft departing from an airport will represent only a small fraction of all traffic. For example, a study conducted for Aerion shows potential sales of 30 supersonic aircraft per year for 20 years in the small business market. The regulation should take into account both what supersonic aircraft technology can reasonably provide and what airport communities will tolerate.

The momentum is accelerating through technology and market changes that could bring supersonic commercial flight back if regulation continues. Although, initially, it may be affordable for a small number of people, the experience gained in the development and operation of these devices will inevitably lead to new innovations that lower the price of tickets and allow you to fly faster than your company.

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