It’s interesting to speculate how far you can go with just compressor stages as essentially big ducted fans and MHD transfer and augmentation… with no heating stage per se…
… perhaps fast enough (mach 2+?) to go directly to a beam-heated ram duct for the slog from there to mach 8-10, which seems to be an optimal velocity to launch to orbit from…
… of course with FF one might well launch to orbit from mach 2-3 @ 60-70k ft…
edit: garbled “optimal”
