At Mach 6 it's just too hot and energetic to compress and stabley combust, as I understand. Recall that stagnation temperature is a function of the square of ve

At Mach 6 it's just too hot and energetic to compress and stabley combust, as I understand. Recall that stagnation temperature is a function of the square of velocity. The reddit article says the compressor 'puts heat back in' but that's a byproduct rather than the aim. The aim of the compressor in this engine is to get enough moles of oxygen in the combustion chamber with enough moles of hydrogen to combust and produce enough thrust. You couldn't compress the air sufficiently to squeeze it into the combustion chamber if you didn't cool it a bit first. This is my understanding based on reading what's publically available on the net anyway.