An apparatus for a rotary internal combustion engine. The engine has three rotating members that orbit about the center of a three-armed rotor as the rotor rotates within a housing with three lobes. The tips of the rotating members engage the lobes and a circular cutout in the rotor as the rotor rotates. A back plate includes inlet and exhaust ports that are sequentially opened and closed by the rotating members and rotor as they move within the housing. A front plate rotates with the rotor and separates the combustion chambers from a planetary gear assembly that ensures the alignment of the rotating members as they orbit the rotor shaft. Fuel is injected after the compression cycle is initiated.