Granted Patent B2

US 12,570,394 · App. 18/535,340 · Granted Mar 10, 2026

Inventor: David Thomas Birkenstock (Herndon, VA)

B64C21/04B64C21/02B64C21/06B64C21/01B64C2230/20

Abstract

Claims (49)

1 . A method of optimizing boundary layer control in an aerodynamic body, the aerodynamic body comprising:

an enclosing structure having a leading edge, a trailing edge, a first body portion extending between the leading edge and the trailing edge, and a second body portion extending between the leading edge and the trailing edge and disposed opposite the first body portion;

an inner cavity defined within the enclosing structure;

at least one bellows assembly disposed in the inner cavity and including at least one primary bellows and at least one secondary bellows;

wherein the at least one bellows assembly is spaced apart from inner surfaces of the leading edge, the trailing edge, the first body portion, and the second body portion so as to define a void between the at least one bellows assembly and the inner surfaces;

a first boundary control inlet defined in the first body portion and in communication with the void;

a second boundary control inlet defined in the second body portion and in communication with the void;

wherein the method comprises:

sequentially operating the at least one primary bellows and the at least one secondary bellows.

2 . The method of claim 1 , wherein the aerodynamic body further comprises a wake-immersed propulsion exhaust duct disposed proximate the trailing edge and in communication with the void, and wherein the method further comprises venting air from the inner cavity via the wake-immersed propulsion exhaust duct into the void.

3 . The method of claim 1 , wherein the aerodynamic body comprises at least one further boundary control inlet defined in the first body portion and in communication with the void.

4 . The method of claim 3 , wherein, in the aerodynamic body, the at least one further boundary control inlet is arranged rearwardly of the first boundary control inlet and aligned, in a chord-wise direction of the aerodynamic body, with the first boundary control inlet.

5 . The method of claim 1 , wherein the aerodynamic body further comprises a series of boundary control inlets defined in the first body portion and in communication with the void, said series of boundary control inlets aligned in a chordwise direction of the aerodynamic body.

6 . The method of claim 5 , wherein the series of boundary control inlets is arranged rearwardly of the first boundary control inlet and aligned, in a the chordwise direction of the aerodynamic body, with the first boundary control inlet; and

wherein the boundary control inlets of the series of boundary control inlets are arranged in a front-aft direction of the aerodynamic body.

7 . The method of claim 1 , wherein the aerodynamic body is one of: an airfoil or a fuselage.

8 . The method of claim 1 , wherein at least one surface imperfection is defined on an outer surface of the enclosing body.

9 . The method of claim 8 , wherein the at least one surface imperfection is sized to prevent laminar flow on a flat plate.

10 . The method of claim 1 , wherein the method further comprises generating static pressure thrust (SPT) over the aerodynamic body.

11 . The method of claim 1 , wherein sequentially operating the at least one primary bellows and the at least one secondary bellows comprises:

maintaining an area of below-ambient pressure adjacent to the at least one primary bellows and the at least one secondary bellows by sequentially contracting the at least one primary bellows and the at least one secondary bellows.

12 . The method of claim 1 , wherein the method further comprises:

after sequentially operating the at least one primary bellows and the at least one secondary bellows, increasing drag by one of: ceasing or reversing sequential operation of the at least one primary bellows and the at least one secondary bellows.

13 . The method of claim 12 , wherein the method further comprises performing an emergency descent.

14 . The method of claim 1 , wherein the aerodynamic body is an aerodynamic body of a solar powered High-Altitude Long Endurance (HALE) aircraft comprising at least one photovoltaic element, wherein the at least one primary bellows and the at least one secondary bellows comprise a plurality of primary bellows and a plurality of secondary bellows, wherein the plurality of primary bellows and plurality of secondary bellows are defined over an entire airframe of the HALE aircraft.

15 . The method of claim 1 , wherein the aerodynamic body is an aircraft wing of an aircraft having a cockpit, the wing having a proximal side closer to the cockpit and a distal side further from the cockpit;

wherein the at least one primary bellows and the at least one secondary bellows comprise a plurality of primary bellows and a plurality of secondary bellows, wherein the plurality of primary bellows and plurality of secondary bellows are distributed to mitigate a thicker boundary layer on the distal side of the aircraft wing.

16 . The method of claim 1 , wherein the at least one primary bellows and the at least one secondary bellows comprise a plurality of primary bellows and a plurality of secondary bellows, wherein the method further comprises:

venting the plurality of primary bellows and plurality of secondary bellows via at least one shared plenum and valve.

17 . A method of optimizing boundary layer control in an aerodynamic body, the aerodynamic body comprising:

an enclosing structure having a leading edge, a trailing edge, a first body portion extending between the leading edge and the trailing edge, and a second body portion extending between the leading edge and the trailing edge and disposed opposite the first body portion;

an inner cavity defined within the enclosing structure;

at least one bellows assembly disposed in the inner cavity and including at least one primary bellows and at least one secondary bellows;

wherein the at least one bellows assembly is spaced apart from inner surfaces of the leading edge, the trailing edge, the first body portion, and the second body portion so as to define a void between the at least one bellows assembly and the inner surfaces;

a first boundary control inlet defined in the first body portion and in communication with the void;

a second boundary control inlet defined in the second body portion and in communication with the void;

wherein the method comprises:

maintaining an area of below-ambient pressure adjacent to the at least one primary bellows and the at least one secondary bellows by sequentially contracting the at least one primary bellows and the at least one secondary bellows.

18 . A method of optimizing boundary layer control in an aerodynamic body, the aerodynamic body comprising:

an enclosing structure having a leading edge, a trailing edge, a first body portion extending between the leading edge and the trailing edge, and a second body portion extending between the leading edge and the trailing edge and disposed opposite the first body portion;

an inner cavity defined within the enclosing structure;

at least one bellows assembly disposed in the inner cavity and including at least one primary bellows and at least one secondary bellows;

wherein the at least one bellows assembly is spaced apart from inner surfaces of the leading edge, the trailing edge, the first body portion, and the second body portion so as to define a void between the at least one bellows assembly and the inner surfaces;

a first boundary control inlet defined in the first body portion and in communication with the void;

a second boundary control inlet defined in the second body portion and in communication with the void;

wherein the method comprises:

sequentially operating the at least one primary bellows and the at least one secondary bellows; and

after sequentially operating the at least one primary bellows and the at least one secondary bellows, increasing drag by one of: ceasing or reversing sequential operation of the at least one primary bellows and the at least one secondary bellows.

19 . The method of claim 18 , wherein the method further comprises performing an emergency descent.

Continuity (4)

References Cited (25)