Yep - but the BOMARC still required a boost phase with
conventional rockets to reach a speed where the ramjet would function. So will this baby.
And yes, a ramjet will function at sub-hypersonic speeds. But the exact configuration has to change with changing speed. Thus Concorde has moveable inlet doors, and the SR-71 (and others) have adjustable inlet cones, to keep changing the configuration of the intake shock waves as the Mach# increases, so that they don't collapse (unstart).
We haven't seen the full details of this engine, just "concepts." But it appears to try and do the same thing without benefit of mechanical aids, just aerodynamics.
I think this is as "real" as controlled and sustained
hot fusion - thermonuclear reactors. Which exist, but which the human race has been dicking around with for 63 years (since Tokamak*), without getting any to actually function
productively (output more energy than they use up).
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*or even 88 years, if one counts various small-scale preliminary experiments: Rutherford, George Paget Thomson, Fermi, Ulam.
https://en.wikipedia.org/wiki/Tokamak