Supersonic flight is possible without an audible sonic boom

The main project page[1] contains links to various papers used to investigate this, including a 3D acoustic ray tracer[2] developed for this.

[1]: https://ascent.aero/project/acoustical-model-of-mach-cut-off...

[2]: https://etda.libraries.psu.edu/catalog/18490zfh5044

The test flight was commented on at the time, 12 days ago: https://news.ycombinator.com/item?id=42853633

Including the obligatory scepticism from the peanut gallery that "Supersonic flight without an audible sonic boom" was even possible.

How does fuel usage compare to mainstream aeroplanes?