An aircraft power and propulsion system includes an air compressor, a heat rejection heat exchanger, a combustor positioned to receive compressed air from the air compressor as a core stream and provide thrust to the aircraft, and a closed-loop s-CO2 system. The closed-loop s-CO2 system includes carbon dioxide as a working fluid, receives power from the combustor, and rejects heat via the heat rejection heat exchanger to a cooling stream. The closed-loop system s-CO2 configured to provide power to a fan that provides the cooling stream and thrust, and power to the air compressor and at least one auxiliary load.