Predicting the sonic boom
Predicting the sonic boom
© Nasa

| Antony Angrand | Source : Air&Cosmos 379 mots

Predicting the sonic boom

In anticipation of the flight test campaign of the X-59 Quesst, Nasa carried out several simulations of the supersonic flight and the generated bang. As for the wind tunnel campaign, Nasa did not put all its eggs in the same basket and multiplied the simulations.

Computational Fluid Dynamics to Predict...

When the X-59 or Quesst (Quiet SuperSonic Transport) takes off and transforms the (very) loud sonic bangs into quieter "thuds," the flight through a rainbow will result in fantastic photos... Much like this dreamlike illustration, but created entirely by Nasa's state-of-the-art supercomputers. Before the X-59 took flight, Nasa researchers got a head start by using computational fluid dynamics to create what is, in effect, a virtual wind tunnel showing a series of aerodynamic details. This is not the first simulation carried out for this program, Nasa has chosen, in the same way as in the wind tunnel test campaign, to multiply the studies. This one is one of the latest to be carried out. 

...The extent of a sonic boom 

In this image, the parallel lines extending outward from the aircraft represent the acoustic shock waves that the X-59 is expected to create during supersonic flight and that will result in a quieter sonic "noise." Note that the aircraft's long, thin aerodynamic nose pierces the air, which is essential for dampening the bang. In the same vein, the position of the air intake and the fact that it is almost in the center of the wing will also help drastically reduce the number of decibels perceived on the ground, which logically should not exceed 75 EnpdB (Effective perceived noise in decibels). 

First flight expected 

These data, which researchers will use to create flight planning tools and software for the Quesst mission, were created at NASA's Advanced Supercomputing Facility at Ames Research Center in California using a tool called Cart3D, a program developed by Nasa. The Quesst program, which is not just a series of supersonic test flights, may allow the FAA to change the regulations and eventually allow flights over the U.S. continent and even North American cities at supersonic speeds. Until now, supersonic cruising as performed by Concorde could only be performed over the Atlantic Ocean. The reduction of the noise perceived on the ground when the Quesst will evolve beyond the speed of sound should make the sonic boom felt like a car door slamming. It is at least what the flight test campaign should confirm. In the meantime, the X-59 should make its first flight before the end of this year. 

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