PROPULSION SYSTEM

Provided is a propulsion system, including: a gas turbine mounted to an airplane; a generator connected to the gas turbine; a battery that stores power generated by the generator; a motor that is driven by power supplied from the generator and/or power supplied from the battery; a rotor that is driven by the motor; a first flow path that allows first fluid discharged from the gas turbine to flow; a second flow path that allows second fluid flowing near the battery to circulate; a heat exchanger that causes the first fluid and the second fluid to exchange heat; a controller that controls opening/closing of a flow path opening/closing valve provided in the first flow path; and a temperature detector that detects a temperature of the battery, in which, when the temperature is equal to or lower than a first temperature, the controller opens the flow path opening/closing valve.