The QueSST (Quiet Supersonic Transport) is a project to create a more diffuse sonic boom in order to use supersonic flight commercially without the usual abrupt 1~2 psf pressure spike damaging the environment.

I understand that traditionally jets create 2 supersonic booms, at their tail and their tip, and I assume that the new quieter jet is spreading out that pressure change over the length of the plane.

I just don't understand why the sonic booms were happening at the tail and tip to begin with, or what changed to spread them out.

Why was this problem so hard to solve, and what did NASA change to solve it?

If it helps, here are a few of the links that I looked at before hitting a wall:

  • $\begingroup$ What do you know about supersonic and subsonic flow and Prandtl-Meyer expansion? $\endgroup$
    – Solar Mike
    Sep 18 '20 at 8:45
  • $\begingroup$ Probably better directed to the aviation SE site. $\endgroup$
    – Eric S
    Sep 18 '20 at 11:32
  • $\begingroup$ @SolarMike I have perhaps a high school physics student's knowledge; although I do know a fair bit about information theory and entropy, I haven't done fluid dynamics at a college level. I'm ultimately looking to develop an intuition for the problem, rather than become an expert, so a more geometric or intuitive explanation would be ideal, but I'll still happily take an answer that is above my current level but names the concepts that I'll need to look up to understand it! $\endgroup$
    – KryptofTen
    Sep 18 '20 at 16:11
  • $\begingroup$ Spreading out the pressure perturbations in a way that doesn't concentrate the shock waves is the key. Shock waves can dissipate quickly or be stubbornly stable and self reinforcing depending on the details of the thermodynamic properties of the air in front and behind the shock. If you can create a fuzzy shock wave that stays fuzzy, you should be able to dissipate the energy over a longer period of time. I assume this only works over an exceedingly narrow range of conditions though. Your highschool math isn't gonig to cut it though. The most basic approach is the method of characteristics. $\endgroup$
    – Phil Sweet
    Sep 18 '20 at 23:58
  • $\begingroup$ Here's a doc that introduces the method and actually talks about the sonic boom shock wave problem in terms of characteristics on p554. PDE method of characteristics $\endgroup$
    – Phil Sweet
    Sep 19 '20 at 0:00

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