I’ll be super excited to have low-to-null-boom supersonic transcontinental flights! But if this becomes a passenger plane, what kind of fuel efficiency would that have? Are supersonic aircraft more or less efficient (oranges and apples I presume).
Surprisingly enough, supersonic planes have good fuel economy while supercruising - thanks to thin air at the high altitude, and speeds around Mach 2 ... 3 being good for turbojet engines.
Expect worse taxiing, take-off and climb fuel economy, due to dense air and also suboptimal (high) angle of attack. This means supersonic planes are best suited for longer routes.
Even the grandpa Concorde had good fuel economy in cruise, however it was overshadowed by atrocious fuel economy at low speeds, and the use of afterburners in transsonic region[1]. The designed but never built Concorde "B" would have notably better economy thanks to more advanced engines doing away with the afterburners.
[1] https://www.quora.com/How-fuel-efficient-was-the-Concorde-co...
And Concorde powerplant had at some point the highest overall thermal efficiency at max speed:
https://en.wikipedia.org/wiki/Rolls-Royce/Snecma_Olympus_593
The overall thermal efficiency of the engine in supersonic cruising flight (supercruise) was about 43%, which at the time was the highest figure recorded for any normal thermodynamic machine.
This reminds me, in the book "Skunk Works", SR-71 Blackbird pilots mentioned their schedule of mid-air refueling 20-30min after takeoff. After that they could make it 3-5hrs at high altitude before refueling again.
As for books, I wholeheartedly recommend the excellent https://www.barnesandnoble.com/w/sled-driver-brian-shul/1123... written by one of the pilots.
Concordes were wasting double digit of their fuel reserve while flying in the holding pattern if runways were not available for some reason.
Though note this was uncommon; they were typically cleared for a direct approach all the way from cruise to touchdown. Part of the reason why they rarely got put in the holding pattern was the fact that it would quickly turn into a low fuel emergency, and part was giving the SST preferential treatment.
You can compensate by cramming in seats closer or trying exotic designs. And there's some efficiency buy-back by operating at higher altitudes where the engine can expand to lower pressures (and thus increase the pressure ratio), but overall, roughly half as efficient is a decent guesstimate.
Then again, conventional aircraft are about double the efficiency they used to be, so supersonic aircraft today could conceivably be approximately the same efficiency as transonic aircraft of yesteryear.
I think exotic designs could enable decent range low supersonic electric flight (i.e. Mach 1.5 or something). Going to need good batteries, though, and extremely high aspect ratio wings.