A Brayton-cycle rotary ramjet engine (10) operated within the confines of a helically elongated pass-through duct formed between a preferably stationary radially outward surface (14) and an outer rotating flow channel (36). The flow channel (36) is contoured between its inlet (34) and outlet (38) to include a supersonic diffuser (40), a combustor (42) and an expansion nozzle (44). Gaseous fuel, or liquid fuel atomized by a fuel slinger (58) within a housing (46), or solid fuel in the form of fine particulates, is inter-mixed with an oxidizer prior to being directed to the flow channel inlets (34). The air and fuel are combusted in the flow channels (36) and exhausted through the rear of the housing (46). A generator (22) can be coupled to a power shaft (18) to convert net shaft power into electricity. Preferably, the rotor (24) and stator (12) are fabricated from a ceramic or other high-temperature material so that combustor exit temperatures (T3) can be operated at highly efficient levels.