[creer]

There has not been supersonic civil aviation but "supersonic" is not the interesting point here. "Supersonic" is easy and solved often in aviation. The question is what else can they do to make it work. And there is no aircraft yet, just a scale model. Progress sure but not because "supersonic". The new engine would be more interesting.

And how is this a civilian aircraft? It is a cool one-off single seater with three military engines (oops, civilian engines derived from military and used in business jets - still not cheap for a one-seater). Two-seater for some definition of "technically". But perhaps they can sell a few of these to private pilots and then it would be a supersonic civilian aircraft. One pilot and one passenger if we insist on making it a business jet.

[adastra22]

Supersonic is “easy” in the sense that rocket design is “easy.” Orbital rockets were still out of reach of non-government-funded efforts until SpaceX, and supersonic flight is still the sole domain of government contractors now. Boom is changing that.

[creer]

Easy of course in the sense that that many aerospace engineers and aircraft have done it all over the world for many years. And most "government contractors" in the capitalist world are civilian private companies, many of which build both military and civilian aircraft and started small.

Which means, for example, that even this small private company knew pretty well what to look for in wind tunnel tests and other materials work. Their first transonic and supersonic flight was stable, did not destroy the aircraft, did not kill the engines, etc. Even, presumably, broke through the sound barrier the first time they tried - and was fully expected to.