A gas turbine engine, comprising: a nacelle comprising an inner surface at least partially defining a fan bypass duct (B); a fan configured to drive a bypass air along the fan bypass duct; a low speed shaft configured to rotate about a longitudinal axis of the gas turbine engine; and an electric propulsion system , comprising: an electric motor comprising a rotor, the electric motor disposed within the nacelle of the gas turbine engine, the electric motor is disposed radially outward from the fan bypass duct (B), and the electric motor is configured to drive the low speed shaft of the gas turbine engine; a drive shaft coupled to the rotor, wherein the drive shaft is configured to extend through the fan bypass duct (B), wherein the electric motor is in operable communication with the low speed shaft via the drive shaft ; a motor cooling duct comprising an outlet at the inner surface of the nacelle ; wherein the electric motor is configured to receive the bypass air from the fan bypass duct (B) for cooling the electric motor ; and the motor cooling duct is configured to receive the bypass air from the electric motor and direct bypass air back into the fan bypass duct (B). a nacelle comprising an inner surface at least partially defining a fan bypass duct (B); a fan configured to drive a bypass air along the fan bypass duct; a low speed shaft configured to rotate about a longitudinal axis of the gas turbine engine; and an electric propulsion system , comprising: an electric motor comprising a rotor, the electric motor disposed within the nacelle of the gas turbine engine, the electric motor is disposed radially outward from the fan bypass duct (B), and the electric motor is configured to drive the low speed shaft of the gas turbine engine; a drive shaft coupled to the rotor, wherein the drive shaft is configured to extend through the fan bypass duct (B), wherein the electric motor is in operable communication with the low speed shaft via the drive shaft ; a motor cooling duct comprising an outlet at the inner surface of the nacelle ; wherein the electric motor is configured to receive the bypass air from the fan bypass duct (B) for cooling the electric motor ; and the motor cooling duct is configured to receive the bypass air from the electric motor and direct bypass air back into the fan bypass duct (B). an electric motor comprising a rotor, the electric motor disposed within the nacelle of the gas turbine engine, the electric motor is disposed radially outward from the fan bypass duct (B), and the electric motor is configured to drive the low speed shaft of the gas turbine engine; a drive shaft coupled to the rotor, wherein the drive shaft is configured to extend through the fan bypass duct (B), wherein the electric motor is in operable communication with the low speed shaft via the drive shaft ; a motor cooling duct comprising an outlet at the inner surface of the nacelle ; wherein the electric motor is configured to receive the bypass air from the fan bypass duct (B) for cooling the electric motor ; and the motor cooling duct is configured to receive the bypass air from the electric motor and direct bypass air back into the fan bypass duct (B). <EOS>