Is a Mach-5 passenger aircraft actually the goal of this project?
Seems more likely that Japan is designing this engine for a hypersonic cruise missile program, and the passenger aircraft concept is somewhat of a cover.
IMO, there is no point in a Mach-5 Aircraft (other than cruise missiles). There is potentially some point in Mach 2-3 aircraft, (not that we have ever made them commercially viable) but at the boundary to hypersonic, you might as well just switch to a suborbital hop concept.
A suborbital hop gets you to anywhere in the world within ~90min, avoids issues of supersonic overflight and you don't need to worry about the massive engineering issues caused by sustaining hypersonic flight. And as a bonus, the passengers get a hour of weightlessness.
Seems more likely that Japan is designing this engine for a hypersonic cruise missile program, and the passenger aircraft concept is somewhat of a cover.
IMO, there is no point in a Mach-5 Aircraft (other than cruise missiles). There is potentially some point in Mach 2-3 aircraft, (not that we have ever made them commercially viable) but at the boundary to hypersonic, you might as well just switch to a suborbital hop concept.
A suborbital hop gets you to anywhere in the world within ~90min, avoids issues of supersonic overflight and you don't need to worry about the massive engineering issues caused by sustaining hypersonic flight. And as a bonus, the passengers get a hour of weightlessness.