A lot of engineers are dazzled by all that "free oxygen and reaction mass" you seem to get from such an approach.

The problem is, that it doesn't buy you that much when you've gotten the oxygen into a useful form to burn with whatever fuel you are using.

Also, the thermal problems of a Mach 30 airplane are completely different from those of a normal reusable rocket spacecraft. You have to hang in the atmosphere at high speeds for a long time to get the velocities you need, and that's a lot of heating.

My call is that you get your rear end out of the atmosphere as soon as possible and use rockets to get to orbital velocity.

A Mach 30 airplane is of technical interest, but much in the same way as a supersonic submarine would be.