> To the extent the costs result from legislative mandates, and are not inherent in building supersonic aircraft, you obviously can
The problems with cost are real, but it's more from flight restrictions than drag (subsonic flight over mainland to final destination using a supersonic-optimized engine is going to be very inefficient).
We can just look at the Concord as a prime example. Barred from supersonic flight over mainland, it became economically infeasible to continue to operate only trans-oceanic flights (I believe all 3 operators ran it as a loss-leader, of sorts, due to the novelty). Even then, when approaching the destination, the Concord had to revert to subsonic speeds, and ditch the shock wave while still out at sea. Unless there's some magical way to generate only minute shock waves from large passenger aircraft (I'm highly skeptical here), you're going to break people's windows etc, or you're going to burn up a bunch of fuel and wind up with the same issues all over again.
The other lesson learned from the Concord is, there's very few cases where people need to be somewhere that quickly, and are willing to pay the high ticket prices to do so. One can almost always book an earlier flight, for a substantial savings (I'm also highly skeptical there's any fuel cost savings with supersonic flight as the article seems to claim).
No one is arguing that that isn't the case; as the article points out, the legislation addresses both the flight restrictions and the noise rule that the article claims functionally requires engine designs which increase drag.
Noise rules are there for good reason (nobody likes broken windows)... and I'm sure there's military applications for quieter supersonic engines, but we don't have any (either because we haven't tried, or, more likely, because it can't be).
I suppose I'm just highly skeptical they can do both, or either, in reality. Sort of, having their cake and eating it too.
I'd love to be proved wrong here though, so I guess we'll have to wait and see.
The engine noise rule at issue has nothing to do with broken windows, and the change is to use the same engine noise level restrictions as subsonic aircraft, rather than stricter rules for supersonic aircraft.
> So, any new legislation only needs to target lifting the over mainland restrictions
Which the legislation does...
> but you can't legislate-away the enormous costs involved in building and operating supersonic aircraft.
To the extent the costs result from legislative mandates, and are not inherent in building supersonic aircraft, you obviously can.