An aircraft propulsion system comprising: a single parallel propulsion unit positioned on a centerline of the aircraft, the single parallel propulsion unit comprising: a propulsor; a gas turbine engine configured to drive the propulsor; and an electrical machine selectively configurable to: generate, for output via one or more electrical busses, electrical energy using mechanical energy derived from the propulsor or the gas turbine engine; and drive the propulsor using electrical energy received via the one or more electrical busses; and a plurality of series propulsion units positionally mirrored across the centerline of the aircraft, each of the series propulsion units comprising: a propulsor of a set of propulsors; and an electrical machine selectively configurable to: generate, for output via the one or more electrical busses, electrical energy using mechanical energy derived from the propulsor or the gas turbine engine; and drive the propulsor of the set of propulsors using electrical energy received from the one or more electrical busses. a single parallel propulsion unit positioned on a centerline of the aircraft, the single parallel propulsion unit comprising: a propulsor; a gas turbine engine configured to drive the propulsor; and an electrical machine selectively configurable to: generate, for output via one or more electrical busses, electrical energy using mechanical energy derived from the propulsor or the gas turbine engine; and drive the propulsor using electrical energy received via the one or more electrical busses; and a propulsor; a gas turbine engine configured to drive the propulsor; and an electrical machine selectively configurable to: generate, for output via one or more electrical busses, electrical energy using mechanical energy derived from the propulsor or the gas turbine engine; and drive the propulsor using electrical energy received via the one or more electrical busses; and generate, for output via one or more electrical busses, electrical energy using mechanical energy derived from the propulsor or the gas turbine engine; and drive the propulsor using electrical energy received via the one or more electrical busses; and a plurality of series propulsion units positionally mirrored across the centerline of the aircraft, each of the series propulsion units comprising: a propulsor of a set of propulsors; and an electrical machine selectively configurable to: generate, for output via the one or more electrical busses, electrical energy using mechanical energy derived from the propulsor or the gas turbine engine; and drive the propulsor of the set of propulsors using electrical energy received from the one or more electrical busses. a propulsor of a set of propulsors; and an electrical machine selectively configurable to: generate, for output via the one or more electrical busses, electrical energy using mechanical energy derived from the propulsor or the gas turbine engine; and drive the propulsor of the set of propulsors using electrical energy received from the one or more electrical busses. generate, for output via the one or more electrical busses, electrical energy using mechanical energy derived from the propulsor or the gas turbine engine; and drive the propulsor of the set of propulsors using electrical energy received from the one or more electrical busses.