The dream of a quiet supersonic aircraft

NASA and Lockheed Martin are researching an aircraft that could revolutionize supersonic flight. It should not generate a bang and could therefore be of interest for civil aviation.

Older readers will certainly still remember the Concorde, the first and, at the same time, last supersonic aircraft that was previously in scheduled flight service. The Concorde made the distance between Paris and New York in just under three hours and was the symbol of the jet set par excellence when it launched commercially in 1976. But as loud as the start was, the farewell was so quiet. The Concorde took off for the last time in 2003, and civil supersonic flight has been suspended since then.

Supersonic planes are not only expensive, they are simply too loud. The so-called supersonic boom, which always occurs when the machines break through the speed of sound of around 1,235 km / h in dry air, is so loud that commercial supersonic flights over land are still banned in the USA to this day. And that although the actual bang only lasts 200 milliseconds.

To change that, various research institutions and manufacturers are now working on so-called low-boom aircraft. They should reach supersonic speed, but not be louder than conventional jets – if at all.

Nasa and Lockheed Martin are at the forefront of development. For several years now, both have been researching a model called X-59 QueSST, the QueSST stands for Quiet SuperSonic Technology. The prototype is now in the hot phase, the first test flights are planned for 2022, such as writes reporter Claire Reilly from Cnetwho was now allowed to take a look behind the scenes.

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The pilots rely on cameras

The X-59 has nothing in common with a passenger aircraft. The model is just 30 meters long, the wings have a wingspan of only 9 meters and there is space for exactly one passenger: the pilot, who sits so far behind the needle-shaped front fuselage that he cannot see what is happening in front of the aircraft and therefore relies on cameras.

That sounds a long way from an airplane that will one day transport several dozen people. Nevertheless, the technology could be groundbreaking, say the engineers. Their aim is to demonstrate in principle that a supersonic aircraft can fly quietly and, in so doing, to a certain extent outsmart the physics of sound. The X-59 is so streamlined that the sound waves “behave well,” as Larry Cliatt describes it from the nose. They should run as parallel as possible over the entire length of the aircraft and not overlap, because that is exactly what inevitably leads to a bang. The first tests in the simulator were very promising.

In order to test the principle in the air – and to measure the actual volume – the developers plan to send an F-15 fighter into the air with the X-59 and record the sound waves. On the ground in the Mojave Desert, microphones are said to record how loud the overflight is over a distance of 30 miles. In the best case scenario, the volume does not exceed 79 decibels, which is roughly the volume of a slammed car door.

If the simulations prove to be true, the engineers can take the findings and develop further, larger aircraft models based on them. In the best case scenario, one day a new generation of supersonic aircraft will actually emerge that will take us to distant places in half the time. Even if you can be sure that the tickets, as with the Concorde, will certainly be anything but cheap.

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