SOLAR-POWERED AIRCRAFT WITH ROTATING FLIGHT SURFACES

1 . An aircraft comprising:

a fuselage having a front and a rear and defining longitudinal axis of the aircraft;

a wing assembly coupled to fuselage including wing flight control surfaces;

at least one electric motor for powering the aircraft;

a tail assembly, rotatably coupled to the fuselage at about the rear of the fuselage, the tail assembly including:

at least two tail fins; and

a plurality of solar cells mounted on an upper surface of the at least two tail fins for powering the at least one electric motor;

a rear solar drive motor for rotating the tail assembly about the longitudinal axis during flight based on the position of the sun relative to the aircraft to increase exposure of the solar cells to sunlight.

2 . The aircraft of claim 1 , comprising a energy store electrically coupled to the solar cells and the at least one electric motor.

3 . The aircraft of claim 2 , wherein the energy store comprises a battery.

4 . The aircraft of claim 2 , wherein the energy store comprises a regenerative fuel cell.

5 . The aircraft of claim 1 , wherein the tail assembly includes two fins arranged in a V orientation.

6 . The aircraft of claim 1 , comprising a flight control processor for controlling control surfaces of the wing assembly and the tail assembly, wherein the flight control processor takes into account rotation of the tail assembly about the longitudinal axis in controlling the control surfaces.

7 . The aircraft of claim 6 , wherein the flight control processor controls the rear solar drive motor based on a time of day, a season of the year, a geographic location, and a direction of flight.

8 . The aircraft of claim 1 , wherein the tail assembly includes a third fin, wherein the angles between each of the at least two fins having solar cells mounted thereon and the third fin is equal and greater than 90 degrees.

9 . The aircraft of claim 1 , comprising:

a fore assembly, rotatably coupled to about the front of the fuselage, including:

at least two fins;

a plurality of solar cells mounted on upper surfaces of the fins; and

a front solar drive motor for rotating the fore assembly about the longitudinal axis during flight based on the position of the sun relative to the aircraft to increase exposure of the solar cells mounted on the fore assembly to sunlight.

10 . The aircraft of claim 9 , comprising a flight control processor for controlling control surfaces of the wing assembly, the tail assembly, and the fore assembly, wherein the flight control processor takes into account rotation of the tail assembly and the fore assembly about the longitudinal axis in controlling the control surfaces.

11 . A method of powering an aircraft having solar cells mounted on tail of the aircraft, comprising:

determining an elevation of the sun relative to a current bearing of the aircraft;

rotating the aircraft tail about a longitudinal axis of the aircraft based on the determined elevation of the sun and a bearing of the aircraft to increase exposure of the solar cells to the sun;

powering the aircraft using solar energy output by the solar cells; and

controlling flight surfaces of the aircraft based on the rotation of the aircraft tail to maintain the bearing.

12 . The method of claim 11 , comprising storing solar energy output by the solar cells in a energy store.

13 . The method of claim 12 , wherein the energy store comprises a battery.

14 . The method of claim 12 , wherein the energy store comprises a regenerative fuel cell.

15 . The method of claim 12 , comprising powering the aircraft in low-light conditions using energy stored in the energy store.

16 . The method of claim 11 , comprising rotating a fore assembly of the aircraft, having solar cells mounted thereon about the longitudinal axis of the aircraft to increase exposure of the solar cells to the sun.

17 . The method of claim 16 , wherein the flight surfaces of the aircraft are further controlled based on the rotation of the fore assembly.

18 . The method of claim 11 , comprising selecting a flight path to increase solar energy collection.

19 . The method of claim 11 , comprising selecting a flight path such that the aircraft tail need only be rotated during significant aircraft turns while still increasing solar energy collection.

20 . The method of claim 11 , wherein the elevation of the sun is determined based on a time of day, a season of the year, and a geographic location.