Propulsion system architecture

A method of operating a propulsion system, comprising the steps of:

• operating a first rotating fan assembly to produce a first stream of air;
• directing a portion of the first stream of air into a second ducted rotating fan assembly through an inlet positioned axially between the first rotating fan assembly and a stationary element, the stationary element including an array of vanes;
• operating the second ducted rotating fan assembly to produce a second stream of air;
• dividing the second stream of air into a core stream and a fan stream, the fan stream defined at least in part by a second duct;
• directing the core stream into the gas turbine engine core, wherein the gas turbine engine core comprises the booster, a combustor, and a turbine arranged in a serial flow relationship, and wherein the gas turbine engine core comprises a shaft that is coupled to the booster and the turbine;
• operating the booster, wherein the booster comprises a plurality of booster stages coupled to the shaft, each of the plurality of booster stages comprising booster airfoils, wherein the second ducted rotating fan assembly is a booster stage of the plurality of booster stages and all airfoils coupled to the shaft and positioned downstream from the first rotating fan assembly and positioned upstream from the combustor are booster airfoils, wherein dividing the second stream of air into a core stream and a fan stream comprises dividing the second stream of air into a core stream and a fan stream at a location downstream of the ducted rotating fan and upstream of the rest of the plurality of booster stages,
• wherein the propulsion system defines a bypass airflow stream radially outward of the inlet, and wherein the second duct is in airflow communication with the bypass airflow stream;
• operating the first rotating fan assembly through a first gearbox;
• and
• operating the second ducted rotating fan assembly through a second gearbox.