[jasonwatkinspdx]

It is combined cycle, but that does not mean it's equivalent to the RBCC design. There are several variations of combined cycle engines. RBCC is not a catchall. This is a refinement of the Liquid Air Cycle Engine concept that was researched by the US military in the 60's and the british in the 80's. The principal british investigator was Alan Bond, who is also the principal in Reaction.

It is appropriate to distinguish it from both jet engines and rocket engines because in the Brayton Cycle compression is adiabatic rather than diabatic in SABRE. I don't believe there is a formal term for this cycle, but the closest existing would be the Ericcson Cycle.

I do not understand your preoccupation with whether to categorize something as novel or not. The have a chiller that drops the temperature of a near supersonic air flow over 1000C in a fraction of a second. If that doesn't meet your standards of novel I don't know what would.