All CO2 aircraft

1. An aircraft power and propulsion system, comprising:

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 power and propulsion system; and

a closed-loop s-CO 2 system having carbon dioxide as a working fluid, that receives power from the combustor and rejects heat via the heat rejection heat exchanger to a cooling stream, the closed-loop s-CO 2 system is configured to provide power to:

a fan that provides the cooling stream and thrust;

the air compressor; and

at least one auxiliary load;

wherein the closed-loop system further comprises:

a first s-CO 2 turbine coupled to an s-CO 2 compressor via a first shaft;

a second s-CO 2 turbine coupled to the air compressor via a second shaft; and

a third s-CO 2 turbine coupled to the fan via a third shaft; and

wherein the first shaft, the second shaft, and the third shaft are axially offset from each other.

2. The aircraft power and propulsion system of claim 1 , wherein the closed-loop s-CO 2 system provides power via the working fluid to the at least one auxiliary load by being configured to provide:

a first grade of energy to provide a first aircraft function; and

a second grade of energy to provide a second aircraft function.

3. The aircraft power and propulsion system of claim 2 , wherein the first and second grades of energy are extracted at different entropy levels and at different stages within the closed-loop s-CO 2 system.

4. The aircraft power and propulsion system of claim 3 , wherein one of the first and second grades of energy is extracted as one of:

output from the s-CO 2 compressor;

output from the combustor; and

output from the first s-CO 2 turbine and prior to entering the heat rejection heat exchanger.

5. The aircraft power and propulsion system of claim 2 , wherein the at least one auxiliary load includes one of a heating function, an actuation function, and a mechanical load.

6. The aircraft power and propulsion system of claim 2 , the closed-loop s-CO 2 system further comprising a recuperator positioned to exchange heat from the working fluid that exits the s-CO 2 compressor to the working fluid that exits one of the first, second, and third s-CO 2 turbines.

7. The aircraft power and propulsion system of claim 1 , wherein the closed-loop s-CO 2 system is operated as a condenser during cruise of the aircraft, changing from super-critical to a trans-critical operation.

8. A method of providing power via an aircraft power and propulsion system, comprising:

receiving compressed air from an air compressor as a core stream to provide thrust to the aircraft power and propulsion system;

providing power in a closed-loop s-CO 2 system, having carbon dioxide as a working fluid, to:

a fan that provides a cooling stream and thrust to the aircraft;

the air compressor; and

at least one auxiliary load; and

rejecting heat from the closed-loop s-CO 2 system via a heat rejection heat exchanger to the cooling stream;

wherein the closed-loop system further comprises:

a first s-CO 2 turbine coupled to an s-CO 2 compressor via a first shaft;

a second s-CO 2 turbine coupled to the air compressor via a second shaft; and

a third s-CO 2 turbine coupled to the fan via a third shaft; and

wherein the first shaft, the second shaft, and the third shaft are axially offset from each other.

9. The method of claim 8 , further comprising providing power via the working fluid of the closed-loop s-CO 2 system to the at least one auxiliary load by: providing a first grade of energy to provide a first aircraft function; and providing a second grade of energy to provide a second aircraft function.

10. The method of claim 9 , further comprising extracting the first and second grades of energy at different entropy levels and at different stages within the closed-loop s-CO 2 system, and further comprising extracting one of the first and second grades as one of:

output from the s-CO 2 compressor;

output from the combustor; and

output from the first s-CO 2 turbine and prior to entering the heat rejection heat exchanger.

11. The method of claim 9 , wherein the at least one auxiliary load includes one of a heating function, an actuation function, and a mechanical load.

12. The method of claim 9 , further comprising operating the closed-loop s-CO 2 system as a condenser during cruise of the aircraft, changing from super-critical to a trans-critical operation.

13. The method of claim 8 , further comprising recuperating heat of the closed-loop s-CO 2 system via a recuperator positioned to exchange heat from the working fluid that exits the s-CO 2 compressor to the working fluid that exits one of the first, second, and third s-CO 2 turbines.

14. A power-producing device for an aircraft, comprising:

an air compressor;

a heat rejection heat exchanger configured to reject heat from a working fluid of a closed-loop s-CO 2 system;

a combustor positioned to receive compressed air from the air compressor as a core stream and provide thrust to the aircraft; and

the closed-loop s-CO 2 system having carbon dioxide as the working fluid, that receives power from the combustor and rejects heat via the heat rejection heat exchanger to a cooling stream, the closed-loop system s-CO 2 configured to provide power to:

a fan that provides the cooling stream and thrust to the aircraft;

the air compressor; and

at least one auxiliary load;

wherein the closed-loop system further comprises:

a first s-CO 2 turbine coupled to an s-CO 2 compressor via a first shaft;

a second s-CO 2 turbine coupled to the air compressor via a second shaft; and

a third s-CO 2 turbine coupled to the fan via a third shaft; and

wherein the first shaft, the second shaft, and the third shaft are axially offset from each other.

15. The power-producing device of claim 14 , wherein the closed-loop s-CO 2 system provides power via the working fluid to the at least one auxiliary load by being configured to provide:

a first grade of energy to provide a first aircraft function; and

a second grade of energy to provide a second aircraft function.

16. The power-producing device of claim 15 , wherein the first and second grades of energy are extracted at different entropy levels and at different stages within the closed-loop s-CO 2 system.

17. The power-producing device of claim 16 , wherein one of the first and second grades of energy is extracted as one of:

output from the s-CO 2 compressor;

output from the combustor; and

output from the first s-CO 2 turbine and prior to entering the heat rejection heat exchanger.

18. The power-producing device of claim 14 , further comprising a cooling circuit having an additional compressor operable in a vapor cycle system (VCS).

19. The power-producing device of claim 14 , wherein the closed-loop s-CO 2 system is operated as a condenser during cruise of the aircraft, changing from super-critical to a trans-critical operation.