A hybrid electric propulsion system comprising: a gas turbine engine comprising at least one compressor section and at least one turbine section operably coupled to a shaft; an electrical power system comprising an electric motor (212A,212B) configured to augment rotational power of the shaft of the gas turbine engine a mechanical power transmission (150A, 150B) comprising a gearbox operably coupled between the shaft and the electrical power system; and a plurality of hybrid electric system control effectors operable to control a plurality of states of one or more the gas turbine engine and the electrical power system; and a controller operable to: determine an estimate of a plurality of hybrid electric propulsion system parameters based on a composite system model and a plurality of sensor data; determine a model predictive control state and a prediction based on the hybrid electric propulsion system parameters and the composite system model; determine a model predictive control optimization for the plurality of hybrid electric system control effectors based on the model predictive control state and the prediction using a plurality of reduced-order partitions of the composite system model; and actuate the hybrid electric system control effectors based on the model predictive control optimization. a gas turbine engine comprising at least one compressor section and at least one turbine section operably coupled to a shaft; an electrical power system comprising an electric motor (212A,212B) configured to augment rotational power of the shaft of the gas turbine engine a mechanical power transmission (150A, 150B) comprising a gearbox operably coupled between the shaft and the electrical power system; and a plurality of hybrid electric system control effectors operable to control a plurality of states of one or more the gas turbine engine and the electrical power system; and a controller operable to: determine an estimate of a plurality of hybrid electric propulsion system parameters based on a composite system model and a plurality of sensor data; determine a model predictive control state and a prediction based on the hybrid electric propulsion system parameters and the composite system model; determine a model predictive control optimization for the plurality of hybrid electric system control effectors based on the model predictive control state and the prediction using a plurality of reduced-order partitions of the composite system model; and actuate the hybrid electric system control effectors based on the model predictive control optimization. determine an estimate of a plurality of hybrid electric propulsion system parameters based on a composite system model and a plurality of sensor data; determine a model predictive control state and a prediction based on the hybrid electric propulsion system parameters and the composite system model; determine a model predictive control optimization for the plurality of hybrid electric system control effectors based on the model predictive control state and the prediction using a plurality of reduced-order partitions of the composite system model; and actuate the hybrid electric system control effectors based on the model predictive control optimization.