Ducted fan VTOL vehicles

1. A ducted fan vehicle comprising:

a forward duct and an aft duct disposed in a fuselage and defining a center body between said ducts;

at least two lift-producing propellers, each disposed in one of said ducts; and

means for introducing auxiliary airflow into at least said aft duct to cause an airflow portion close to said center body inside said aft duct to separate from said center body.

2. A ducted fan vehicle according to claim 1 and further comprising at least one slot formed in a forward-facing wall of said aft duct.

3. A ducted fan vehicle according to claim 2 wherein said at least one slot comprises a plurality of said slots arranged circumferentially along said forward-facing wall of said aft duct.

4. A ducted fan vehicle according to claim 1 wherein said means is operative to cause said air flow inside said aft duct to exit said duct at a direction that is generally similar to the direction it had prior to contacting the vehicle's surface.

5. A ducted fan vehicle according to claim 1 wherein said means for introducing auxiliary air flow is a turbine engine compressor of said vehicle.

6. A ducted fan vehicle according to claim 1 wherein said means for introducing auxiliary air flow is either of an air pump and a compressor.

7. A ducted fan vehicle according to claim 1 wherein said means for introducing auxiliary air flow is at least one air scoop connected to said aft duct.

8. A ducted fan vehicle according to claim 2 wherein said at least one slot is located between a plane containing said lift-producing propellers and an outlet end of said aft duct.

9. A ducted fan vehicle according to claim 3 wherein said plurality of slots are located between a plane containing said lift-producing propellers and an outlet end of said aft duct.

10. A ducted fan vehicle according to claim 1 wherein said means for introducing auxiliary air flow is at least one air scoop connected to said aft duct and wherein said at least one air scoop can employ varying cross sectional areas such as to cause related air flow to accelerate and exit said aft duct at higher velocity than the free stream velocity of said air when entering said at least one scoop.

11. A ducted fan vehicle according to claim 1 wherein an aperture is formed in a rearward-facing wall of said aft duct.

12. A ducted fan vehicle according to claim 1 wherein an aperture is formed in a forward-facing wall of said forward duct.

13. A ducted fan vehicle according to claim 1 wherein a first aperture is formed in a rearward-facing wall of said aft duct, and a second aperture is formed in a forward-facing wall of said forward duct.

14. A ducted fan vehicle according to claim 1 wherein the bottom of said fuselage is concavely curved forward of said aft duct.

15. A ducted fan vehicle according to claim 1 and further comprising a curved cutout employed by the lower forward facing body section of said vehicle and configured to affect air flow thereat to assume a general direction that is similar to the direction it had prior to contacting said forward facing body section.

16. A VTOL vehicle comprising:

a fuselage defining a center body with lower part reshaped to affect airflow in favor of enhancing forward flight by reducing momentum drag; and

at least one lift-producing propeller disposed in an open-ended duct next to the center body, said duct comprising a duct wall having at least one aperture therein, and a curved barrier enclosing at least portion of said propeller, said curved barrier moveable between open and closed position to thereby control airflow through said aperture into said open-ended duct.

17. A vehicle according to claim 16 wherein said at least one barrier is moveable along curved slides.