Selective power distribution for an aircraft propulsion system

1. An assembly for an aircraft propulsion system, comprising:

a compressor section, a combustor section, a turbine section and a flowpath extending sequentially through the compressor section, the combustor section and the turbine section;

a rotating structure comprising a turbine rotor, the turbine rotor within the turbine section;

a propulsor rotor, the turbine rotor configured to rotatably drive the propulsor rotor;

a geartrain, the rotating structure coupled to the propulsor rotor through the geartrain; and

an auxiliary turbine comprising an auxiliary turbine rotor, the auxiliary turbine rotor configured to rotatably drive the propulsor rotor with the turbine rotor, the auxiliary turbine configured to receive bleed gas from the flowpath, and the auxiliary turbine rotor operatively coupled to the propulsor rotor independent of the geartrain.

2. The assembly of claim 1 , wherein the auxiliary turbine is configured to receive bleed air from the compressor section.

3. The assembly of claim 1 , wherein

the compressor section comprises a low pressure compressor section and a high pressure compressor section; and

the auxiliary turbine is configured to receive bleed air from the high pressure compressor section.

4. The assembly of claim 1 , wherein the auxiliary turbine comprises an air turbine.

5. The assembly of claim 1 , wherein the auxiliary turbine is configured to increase a rotational speed of the propulsor rotor.

6. The assembly of claim 1 , further comprising a brake configured to brake rotation of the propulsor rotor.

7. The assembly of claim 6 , wherein the brake comprises a disk brake.

8. The assembly of claim 1 , further comprising a lock device configured to lock rotation of the propulsor rotor.

9. The assembly of claim 8 , wherein the lock device comprises a splined coupling.

10. The assembly of claim 1 , further comprising

a second propulsor rotor coupled to the rotating structure through the geartrain, the turbine rotor configured to rotatably drive the second propulsor rotor; and

a second auxiliary turbine comprising a second auxiliary turbine rotor, the second auxiliary turbine rotor configured to rotatably drive the second propulsor rotor with the turbine rotor.

11. The assembly of claim 10 , further comprising a brake configured to brake rotation of the second propulsor rotor.

12. The assembly of claim 11 , wherein, during a transition from driving rotation of the second propulsor rotor to driving rotation of the propulsor rotor with the rotating structure, the brake is configured to brake rotation of the second propulsor and the auxiliary turbine is configured to speed up rotation of the propulsor rotor.

13. The assembly of claim 10 , further comprising a lock device configured to lock rotation of the second propulsor rotor.

14. The assembly of claim 10 , wherein a rotational axis of the propulsor rotor is angularly offset from a rotational axis of the second propulsor rotor.

15. An assembly for an aircraft propulsion system, comprising:

a compressor section, a combustor section, a turbine section and a flowpath extending through the compressor section, the combustor section and the turbine section;

a turbine rotor within the turbine section, the turbine rotor configured to rotate about an axis;

a geartrain;

a propulsor rotor, the turbine rotor configured to rotatably drive the propulsor rotor through the geartrain;

an auxiliary turbine comprising an auxiliary turbine rotor, the auxiliary turbine rotor configured to rotatably drive the propulsor rotor, the auxiliary turbine disposed to a first side of the geartrain, and the turbine section disposed to a second side of the geartrain that is axially opposite the first side of the geartrain along the axis; and

a brake configured to brake rotation of the propulsor rotor.

16. The assembly of claim 15 , further comprising:

a second propulsor rotor, the turbine rotor configured to rotatably drive the second propulsor rotor;

a second auxiliary turbine comprising a second auxiliary turbine rotor, the second auxiliary turbine rotor configured to rotatably drive the second propulsor rotor; and

a second brake configured to brake rotation of the second propulsor rotor;

wherein the second auxiliary turbine and the brake are configured to operate together to stop rotation of the propulsor rotor while the turbine rotor remains rotating; and

wherein the auxiliary turbine and the second brake are configured to operate together to stop rotation of the second propulsor rotor while the turbine rotor remains rotating.

17. The assembly of claim 15 , further comprising a lock device configured to lock rotation of the propulsor rotor.

18. The assembly of claim 15 , wherein the auxiliary turbine is configured to receive bleed gas from the flowpath and drive rotation of the propulsor rotor.

19. An assembly for an aircraft propulsion system, comprising:

a compressor section, a combustor section, a turbine section and a flowpath extending through the compressor section, the combustor section and the turbine section;

a rotating structure comprising a turbine rotor within the turbine section;

a geartrain coupled to the rotating structure;

a first propulsor rotor coupled to the geartrain;

a second propulsor rotor coupled to the geartrain; and

a control system configured to switch between a first mode and a second mode, the rotating structure configured to drive rotation of the first propulsor rotor through the geartrain during the first mode, the rotating structure configured to drive rotation of the second propulsor rotor through the geartrain during the second mode, and the control system including an air turbine and a brake.

20. The assembly of claim 19 , wherein a rotational axis of the first propulsor rotor is angularly offset from a rotational axis of the second propulsor rotor by an angle between sixty degrees and ninety degrees.