Patent ID: 12227291

DETAILED DESCRIPTION OF THE INVENTION

While the system of the present application is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the present application to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present application as defined by the appended claims.

To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as “a”, “an” and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.

Illustrative embodiments of the present application are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

As used herein, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present application, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction.

In aerospace technology, distributed propulsion is defined as distributing the airflows and forces generated by the propulsion system about an aircraft in a way that improves the vehicle's aerodynamics, propulsive efficiency, structural efficiency, and aeroelasticity. While designs have been proposed in which airplanes include a series of small engines or motors along the surfaces and on vertical lift platforms by the assembly of a matrix of small engines or motors. However, the complexity and weight of installing large numbers of conventional turbine or internal combustion engines to achieve distributed propulsion is impractical for all but very large aircraft. For example, mechanically interconnecting multiple propellers using gearboxes and shafts to achieve distributed propulsion can reduce weight, but it sacrifices the ability to independently control propellers or fans to provide thrust vectoring for control and aerodynamic efficiency.

While many applications of electric motors to achieve practical distributed propulsion has attracted major interest by NASA, DARPA, and the aerospace industry, the power density necessary to attain and maintain flight using electric motors and batteries has simply not been feasible. While higher energy density batteries are in development, pure electric propulsion in combination with distributed propulsion, while attractive, has not been attained for anything except small drones and toys.

For example, current Li-ion battery technology is capable of achieving an energy density that would require an impractically heavy Li-ion battery. Thus, using current battery technology, electric distributed propulsion development requires the application of electric generators driven by turbo shaft engines. Replacing battery technology with generators driven by turbo shaft engines reduces system weight only marginally.

With the adoption of generators driven by turbo shaft engines in place of battery technology, the remaining major obstacle to achieving practical electric distributed propulsion is electric motor and associated controller technology. However, current electric motor technology and performance falls short of meeting the requirements for supporting practical application of distributed electric propulsion. As electric motor power and torque output is increased beyond the requirements of small drones to levels suitable for larger aircraft, the issues of power density (Watts of shaft power generated per kilogram of weight), cooling and lubrication lead to impractical increases in weight. Further, even when analyzing the performance of the most advanced electric motors the additional weight for cooling systems, lubrication systems, or required electric power controllers that regulate motor speed and torque are impractical or lead to no significant improvements in overall aircraft performance.

The present invention can use variable displacement hydraulic motors, with the advantage that speed and torque are controlled by changing the displacement of the motor. This is equivalent to having a variable speed transmission in a gearbox or being able to instantly change the size of an electric motor to suit required power demands. Changing the motor displacement requires very little power and can be achieved using servo valve adding very little weight. This added weight to control the hydraulic motor is independent of the rated power on the motor. When the added weight for the hydraulic motor controllers is added to the motor weight a significant improvement was obtained. Further, no additional weight for hydraulic motor lubrication or motor and controller cooling is required for hydraulic motors, as these are already part of the motor weight.

Further, when one compares the weight and volume of hydraulic tubing versus electrical cable required for transmission of power at the magnitudes required for larger aircraft, a benefit is also obtained, or, the values are basically equivalent. Thus, the hydraulic distributed propulsion system of the present invention is lighter than the most efficient, equivalent electric system.

Thus, the present invention takes advantage of the best cost-to-benefit ratio for use of hydraulic and electric motor propulsion. For example, the present invention uses the best of the possible high power systems performance aspects, including but not limited to, weight motor and controller, envelope for motor and controller installation, supplemental motor cooling required, supplemental motor lubrication required, high motor torque and low rotational inertia, motor reliability (not including controller), weight for transmission of power, and total system efficiency using engine.

The invention addresses the limitations of electric motor, generator and battery technology as applied to the field of distributed propulsion for aircraft. By using variable displacement hydraulic pump and motor technology, distributed propulsion for larger aircraft is practical. In variable displacement hydraulic motors, speed and torque is controlled by changing the displacement of the motor. This is equivalent to having a variable speed transmission in a gearbox or being able to instantly change the size of an electric motor to suit required power demands. Compared with controlling electric motor speed using Pulse Width Modulation, changing hydraulic motor displacement requires very little power and negligible weight.

As will be described in more detail below, various embodiments of the present invention integrate a circular wing or ring wing configuration with a distributed a propulsion system to create a vertical takeoff and landing (VTOL) aircraft configuration with long range and high speed. These performance capabilities are achieved without increased aircraft complexity and cost normally incurred with this level of capability in a VTOL aircraft. No reconfiguration of the aircraft is required to transition between vertical hover and horizontal airplane mode flight. The “tail sitter” or “pogo” configuration allows transition without any physical configurations. However, in some embodiments, structural, aerodynamic or power plant adjustments and/or reconfigurations may be desirable. In some embodiments, the rotor blades of the closed wing mounted propellers can be folded either forward or back to further reduce drag and provide increased speed and duration.

Now referring toFIGS.1A-1J, various views of a closed wing aircraft100in accordance with one embodiment of the present invention are shown. More specifically,FIG.1Ais a perspective view,FIG.1Bis a front elevation view,FIG.1Cis a rear elevation view,FIG.1Dis right side elevation view,FIG.1Eis a left side elevation view,FIG.1Fis a top plan view, andFIG.1Gis a bottom plan view. This closed wing aircraft100features the following: 1) Tail sitter configuration provides for conversion to airplane mode without reconfiguration; 2) Circular wing optimizes propulsion, structural, aerodynamic, and center of gravity (CG) requirements; 3) Gearboxes and drive train are completely eliminated; 4) Rotor cyclic and collective controls are replaced by variable speed constant pitch propellers; and 5) Yaw in vertical flight and roll in hover mode are provided by trailing edge surfaces on the spokes connecting the closed wing to the fuselage.

The closed wing aircraft100utilizes the ring wing configuration to provide a symmetric matrix distribution of hydraulic or electric motor driven propellers to maximize controllability and provide safety in the event of a hydraulic or electric motor failure. The ring wing also reduces the effects of cross winds during takeoff and landing by minimizing the affected wing area and eliminating induced yaw. In airplane mode flight the ring wing allows the aircraft maintain any roll position in order to position sensors as required. For noise reduction the propellers within the ring provide an acoustic barrier. Structurally, the combination of distributed propulsion and the ring wing minimizes bending moments allowing for lighter and stiffer structure compared with distributed propulsion on straight wings. Engines or fuel/batteries can be housed in the base of the fuselage or at the intersection of the spokes to the ring wing for strength and minimization of weight. Landing gear is positioned at these points for similar reasons.

More specifically, the aircraft100can be manned or unmanned and is capable of vertical takeoff and landing, stationary flight and forward flight. The aircraft100includes a closed wing102, a fuselage104at least partially disposed within a perimeter of the closed wing102, and one or more spokes106coupling the closed wing102to the fuselage104. The closed wing102can be circular-shaped, oval-shaped (FIG.1H), triangular-shaped (FIG.1I), polygonal-shaped (FIG.1J) or any other shape suitable for the desired operational and aerodynamic requirements of the aircraft100. In addition, the closed wing can be made up of a plurality of wing segments102a,102b,102cand wing-spoke intersections or junctions108a,108b,108cconnected together. The cross-sectional profile of the closed wing102between the leading edge110and trailing edge112can be a symmetrical airfoil or any desirable aerodynamic shape. The number of spokes106can be determined, in part, by the shape and size of the closed wing102, and the shape, size and payload of the fuselage104. The cross-sectional profile of the spokes106between the leading edge114and the trailing edge116can be a symmetrical airfoil or any desirable aerodynamic shape. The closed wing102, the fuselage104and the one or more spokes106are preferably symmetrically shaped to provide transition between vertical takeoff and landing, stationary flight and forward flight in any direction. However, non-symmetrical shapes can be used. As a result, the shape of the closed wing102and number of spokes106shown in the figures is only one example and is not intended to limit the scope of the invention. The closed wing102may also include one or more doors or removable sections that provide access to the fuselage104when the aircraft100is in a landed position.

The fuselage104may include one or more sections or modules that have a longitudinal axis117substantially parallel to a rotational axis118of the propellers120. The shape and length of the fuselage104will vary depending on the desired mission and flight characteristics. As a result, the shape and length of the fuselage104shown in the figures is only one example and is not intended to limit the scope of the invention. For example, the fuselage104may include a rear section or module122substantially disposed at a center of the closed wing102that provides a fuselage-spoke intersection or junction, a middle section or module124connected to the rear section or module122, a front section or module126connected to the middle module124, and a nose section or module128connected to the front section or module126. Sections or modules122,124,126,128can be removably connected to one another, which makes the aircraft100configurable for any desired mission or function. In other words, the closed wing102and one or more spokes106provide a stable flight platform any desired payload. Moreover, the middle124, front126and nose128sections or modules can detach, pivot, or retract at least partially into one or more of the other sections or modules for storage or transport of the aircraft100. The rear122, middle124, front126and nose128sections or modules can be individually configured to be a cockpit module, a cabin module, an escape module, a payload module, a sensor module, a surveillance module, a power source module, a fuel module, or any combination thereof. Note that the nose section or module128may contain one or more parachutes.

The aircraft100also includes three or more landing gear, pads or skids130operably attached to the closed wing102. Typically, the landing gear, pads or skids130will be disposed proximate to the wing-spoke intersections or junctions108a,108b,108cwhere there is more structural support. The landing gear, pads or skids130can be retractable.

One or more engines or motors132are disposed within or attached to the closed wing102, fuselage104or spokes106in a distributed configuration. Three or more propellers120are proximate to the leading edge110of the closed wing102or the leading edge114of the one or more spokes106, distributed along the closed wing102or the one or more spokes106, and operably connected to the one or more engines or motors132. In the embodiment shown, nine propellers120are disposed proximate to the closed wing102, and one propeller120is disposed proximate to each spoke106. The propellers120can be variable speed constant pitch propellers or other type of propeller. The distribution and number of propellers120are designed to provide stability during the failure of one or more propellers120, or engines or motors132.

In one embodiment, a source of hydraulic or electric power is disposed within or attached to the closed wing102, fuselage104or spokes106and coupled to each of the of hydraulic or electric motors132disposed within or attached to the closed wing102, fuselage104or spokes106. The source of hydraulic or electric power provides sufficient energy density for the aircraft to attain and maintain operations of the aircraft100. The source of hydraulic or electric power can be one or more batteries, a piston engine, or a turboshaft engine. A controller is coupled to each of the hydraulic or electric motors132, and one or more processors are communicably coupled to each controller that control an operation and speed of the plurality of hydraulic or electric motors132. Note that a single source of hydraulic or electric power can drive multiple hydraulic or electric motors132. For example, a source of hydraulic or electric power can be located in the wing-spoke intersections or junctions108a,108b,108cor the rear fuselage122where there is more structural support. Hydraulic or electric power distribution systems can be used to transmit the power to the hydraulic or electric motors132, which in turn drive the propellers120. The hydraulic or electric motors132are selected based on at least one of aerodynamics, propulsive efficiency, structural efficiency, aeroelasticity, or weight of the aircraft. Moreover, the propellers120, or the engines or motors132can be mounted to pivot to provide directional thrust. Similarly, additional thrusters can be disposed on the closed wing102, fuselage104or spokes106. Various examples of distributed power systems are shown inFIGS.2-5.

Referring now toFIG.2, a schematic of a hybrid turboshaft engine hydraulic distributed propulsion system200in accordance with one embodiment of the present invention is shown. In the hybrid turboshaft engine hydraulic distributed propulsion system200, a source of fuel202is connected to a fuel line204that feeds a turboshaft engine206that generates a mechanical force that is transmitted by a mechanical shaft208that is connected to a variable displacement hydraulic pump210. The variable displacement hydraulic pump210is connected to, and provides hydraulic power to, hydraulic lines212. The hydraulic fluid in hydraulic lines212is connected to hydraulic controllers214a-214f, which are connected mechanically by mechanical shafts215a-215fto the variable displacement hydraulic motors216a-216f, respectively, each of which is depicted being connected by mechanical shafts218a-218fto propellers120a-120f, respectively. Changing the displacement of the variable displacement hydraulic motors216a-216fcan control the speed and torque of the variable displacement hydraulic motors216a-216f. The variable displacement hydraulic motors216a-216fcan be self-cooling. This schematic shows the Hybrid Turboshaft Engine Hydraulic distributed propulsion system200as having six (6) hydraulic controllers214a-214f, and six (6) variable displacement hydraulic motors216a-216f. However, the skilled artisan will recognize that the present invention can include a smaller or larger number of variable displacement hydraulic motors and propellers, for example 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 or more. In this embodiment, the fuel is converted into mechanical power/energy via the turboshaft engine206, which provides the hydraulic power that drives the variable displacement hydraulic motors216a-216fand therefore the propellers120a-120f.

Now referring toFIG.3, a schematic of a hybrid internal combustion engine-engine hydraulic distributed propulsion system300in accordance with one embodiment of the present invention is shown. In this embodiment, the hybrid internal combustion engine-engine hydraulic distributed propulsion system300uses a source of fuel202that is connected to fuel line204that feeds an internal combustion engine302that generates a mechanical force that is transmitted by a mechanical shaft208that is connected to a variable displacement hydraulic pump210. The variable displacement hydraulic pump210is connected to, and provides hydraulic power to, hydraulic lines212. The hydraulic fluid in hydraulic lines212is connected to hydraulic controllers214a-214f, which are connected mechanically by mechanical shafts215a-215fto the variable displacement hydraulic motors216a-216f, respectively, each of which is depicted being connected by mechanical shafts218a-218fto propellers120a-120f, respectively. Changing the displacement of the variable displacement hydraulic motors216a-216fcan control the speed and torque of the variable displacement hydraulic motors216a-216f. The variable displacement hydraulic motors216a-216fcan be self-cooling. This schematic shows the Hybrid Internal Combustion Engine-Engine Hydraulic distributed propulsion system300as having six (6) hydraulic controllers214a-214f, and six (6) variable displacement hydraulic motors216a-216f. However, the skilled artisan will recognize that the present invention can include a smaller or larger number of variable displacement hydraulic motors and propellers, for example 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 or more. In this embodiment, the fuel is converted into mechanical power/energy via the internal combustion engine302, which provides the hydraulic power that drives the variable displacement hydraulic motors216a-216fand therefore the propellers218a-218f.

Referring now toFIG.4, a schematic of a hybrid electric hydraulic distributed propulsion system400in accordance with one embodiment of the present invention is shown. In this embodiment, the hybrid electric hydraulic distributed propulsion system400uses one or more batteries402that are connected to electrical cable404that directly powers a variable displacement hydraulic motor pump406. The variable displacement hydraulic motor pump406is connected to, and provides hydraulic power to, hydraulic lines212. The hydraulic fluid in hydraulic lines212is connected to hydraulic controllers214a-214f, which are connected mechanically by mechanical shafts215a-215fto the variable displacement hydraulic motors216a-216f, respectively, each of which is depicted being connected by mechanical shafts218a-218fto propellers120a-120f, respectively. Changing the displacement of the variable displacement hydraulic motors216a-216fcan control the speed and torque of the variable displacement hydraulic motors216a-216f. The variable displacement hydraulic motors216a-216fcan be self-cooling. This schematic shows the Hybrid Internal Combustion Engine-Engine Hydraulic distributed propulsion system400as having six (6) hydraulic controllers214a-214f, and six (6) variable displacement hydraulic motors216a-216f. However, the skilled artisan will recognize that the present invention can include a smaller or larger number of variable displacement hydraulic motors and propellers, for example 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 or more. In this embodiment, the electrical power is converted into mechanical power/energy via the variable displacement hydraulic motor pump406, which provides the hydraulic power that drives the variable displacement hydraulic motors216a-216fand therefore the propellers218a-218f.

Now referring toFIG.5, a schematic of a hybrid electric hydraulic with a piezo-electric pump distributed propulsion system500in accordance with one embodiment of the present invention is shown. In this embodiment, the hybrid electric hydraulic with a piezo-electric pump distributed propulsion system500uses one or more batteries402that are connected to electrical cable404that directly powers a piezo-hydraulic pump408. The piezo-hydraulic pump408is connected to, and provides hydraulic power to, hydraulic lines212. The hydraulic fluid in hydraulic lines212is connected to hydraulic controllers214a-214f, which are connected mechanically by mechanical shafts215a-215fto the variable displacement hydraulic motors216a-216f, respectively, each of which is depicted being connected by mechanical shafts218a-218fto propellers120a-120f, respectively. Changing the displacement of the variable displacement hydraulic motors216a-216fcan control the speed and torque of the variable displacement hydraulic motors216a-216f. The variable displacement hydraulic motors216a-216fcan be self-cooling. This schematic shows the Hybrid Internal Combustion Engine-Engine Hydraulic distributed propulsion system500as having six (6) hydraulic controllers214a-214f, and six (6) variable displacement hydraulic motors216a-216f. However, the skilled artisan will recognize that the present invention can include a smaller or larger number of variable displacement hydraulic motors and propellers, for example 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 or more. In this embodiment, the electrical power is converted into mechanical power/energy via the piezo-hydraulic pump408, which provides the hydraulic power that drives the variable displacement hydraulic motors216a-216fand therefore the propellers218a-218f.

Some of the benefits of the distributed hydraulic system of the present invention, in conjunction with electric propulsion, can be attained by the present invention, for aircraft of all sizes. For example, for use with Vertical Take-Off and Landing (VTOL) aircraft the advantages of the present invention include: (1) a reduction in aircraft propulsion installation weight through greater structural integration; (2) the elimination of (rotor cyclic) control through differential and vectoring thrust for pitch, roll, and yaw moments; (3) high production rates and easy replacement of motors or propulsors that are small and light; (4) in the case of turbine/IC engine electric power generation, reduced fuel consumption and emissions through independent control of engine and rotor speeds; and (5) using electric batteries provided for more efficient energy usage, reduced emissions, and lower noise.

Further advantages of the present invention include addressing certain road blocks to distributed electric propulsion for larger VTOL aircraft. The present invention provides one or more of the following benefits: (1) the elimination of electric motor and required controller power densities are low at required power levels (excessive weight); (2) eliminate electric motor torque capacity that is inadequate for speed changes required for thrust vectoring of larger rotors; (3) with increased power, electric motors require large diameters with ducted air or liquid cooling to prevent over heating (increased weight/envelope/complexity); (4) with increased power electric motor bearings require active lubrication (increased weight/complexity); and (5) current battery technology energy density insufficient for practical applications due to excessive weight.

Referring now toFIGS.6A-6C, the aircraft100is shown in stationary flight (hover mode including vertical takeoff and landing) (FIG.6A), transition from stationary flight to forward flight and vice versa (FIG.6B), and forward flight (FIG.6C). The closed wing102provides lift whenever the aircraft100is in forward flight. The three or more propellers120provide lift whenever the aircraft100is in vertical takeoff and landing and stationary flight, and provide thrust whenever the aircraft100is in forward flight. During forward flight, the propellers120can be selectively feathered or operated in a low power mode because the closed wing102and spokes106provide lift. One or more flight control surfaces are disposed on or extending from the closed wing102, spokes106or the fuselage104to provide improved control and flight characteristics. The one or more control surfaces may include one or more air foils, winglets, elevators or ailerons. For example and as shown inFIGS.1A-1G, winglets134mounted on the forward section or module126of the fuselage104. Note that the one or more airfoils or winglets can be retractable, removable, stowable or variable swept.

As shown, the closed wing102, fuselage104and spokes106are not substantially reconfigured for transition between vertical takeoff and landing, stationary flight and forward flight. However, in some embodiments it may be desirable to have the one or more spokes106operable to change a position of the closed wing102with respect to the fuselage104or vice versa. In other words, the spokes106would selectively pivot the closed wing102to act like a giant flap in horizontal mode and/or assist in transition to/from vertical mode.

The aircraft100provides a stable platform for one or more sensors or surveillance packages disposed on, disposed within or attached to the closed wing102, spokes106or fuselage104. In fact, the configuration of the aircraft100allows the placement of the one or more sensors or surveillance packages to provide a 360 degree view. Moreover, the extension of the fuselage104from the engines or motors132provides a wide unobstructed view for the one or more sensors or surveillance packages.

As shown inFIG.6CandFIGS.7A-7G, the propellers120can be selectively folded in a forward direction. The propellers120could also be folded in a backward direction. In the embodiment having the forward folding propellers700, each propeller700includes two or more rotor blades702, each rotor blade702in mechanical communication with a hub704and pivotable about an axis of rotation118. A fold linkage mechanically couples a rotating portion of a bearing plate to the rotor blade702. An actuator is coupled to a non-rotating portion of the bearing plate and is operable to reposition the bearing plate from a first position to a second position such that the folding links pivot the rotor blades702from a deployed position to a folded position. The folded position can be a forward direction, which extends past the hub704with the first position of the bearing plate is closer to the hub704than the second position of the bearing plate. A tip of all the rotors702can be preloaded together in the forward folded position such that a vibration of the rotors702is minimized.

Alternatively and as shown inFIG.8, the folded position can be a backward direction, which extends away from the hub704, and the first position of the bearing plate is closer to the hub304than the second position of the bearing plate. The angle or distance that the rotors702can fold will depend on the relative size and shape of the closed wing with respect to the pivot point and size of the rotors. For example,FIG.8shows the rotors702folded in a backward position, but not against the surface of the closed wing102or substantially parallel to the rotational axis118of the rotors702. Some embodiments of the present invention will have the rotors702resting against or close to the surface of the closed wing102and/or substantially parallel to the rotational axis118of the rotors. An example of backward folding rotor blades is disclosed in U.S. Pat. No. 9,156,545 which is hereby incorporated by reference in its entirety.

Now referring toFIGS.9A-9G, various views of a closed wing aircraft900having a sinusoidal-shaped circular wing in accordance with one embodiment of the present invention are shown. More specifically,FIG.9Ais a perspective view,FIG.9Bis a front elevation view,FIG.9Cis a rear elevation view,FIG.9Dis right side elevation view,FIG.9Eis a left side elevation view,FIG.9Fis a top plan view, andFIG.9Gis a bottom plan view. As shown, the leading edge902and trailing edge904of the closed wing906are sinusoidal-shaped. Instead of the circular wing being a constant height around the center fuselage104as previously shown, the wing rises and falls to create three sinusoidal humps908a,908b,908c. The humps908a,908b,908care at their highest between the three spokes106and lowest where the wing906attaches to the spokes106. The advantages of this configuration are as follows: 1) Additional wing ground clearance to the circular wing when landing. With the flat circular wing landing must be close to perpendicular to avoid damaging the wing or the landing gear must be made much longer. 2) Improved access to center fuselage. With the flat circular wing access to the center fuselage is restricted by the height of the wing. 3) Improved stability by moving the wing center of pressure closer to the aircrafts center of gravity. The same benefits are achieved but to a lesser degree with four sinusoidal humps and four spokes and two sinusoidal humps with two spokes. With more than four sinusoidal humps the benefits are negligible. Alternatively, only one of the leading edge902or the trailing edge904of the closed wing906is sinusoidal-shaped. Moreover, other wing shapes can be used.

A method for distributed propulsion of aircraft capable of vertical takeoff and landing and stationary flight includes the steps of determining at least one of aerodynamics, propulsive efficiency, structural efficiency, and weight of the aircraft, selecting a number, size and type of hydraulic or electric motors necessary to provide distributed propulsion for powered operations of the aircraft, selecting a power source having sufficient energy density to power the hydraulic or electric motors connected to propellers to operate the aircraft, and providing a distributed propulsion system. The distributed propulsion system includes a closed wing, a fuselage at least partially disposed within a perimeter of the closed wing, and one or more spokes coupling the closed wing to the fuselage. A plurality of hydraulic or electric motors are disposed within or attached to the closed wing, fuselage or spokes in a distributed configuration. A propeller is proximate to a leading edge of the closed wing or the one or more spokes, operably connected to each of the hydraulic or electric motors and provides lift whenever the aircraft is in vertical takeoff and landing and stationary flight. A source of hydraulic or electric power is disposed within or attached to the closed wing, fuselage or spokes and coupled to each of the of hydraulic or electric motors disposed within or attached to the closed wing, fuselage or spokes, wherein the source of hydraulic or electric power provides sufficient energy density for the aircraft to attain and maintain operations of the aircraft. A controller coupled to each of the hydraulic or electric motors, and one or more processors communicably coupled to each controller that control an operation and speed of the plurality of hydraulic or electric motors.

It will be understood that particular embodiments described herein are shown by way of illustration and not as limitations of the invention. The principal features of this invention can be employed in various embodiments without departing from the scope of the invention. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, numerous equivalents to the specific procedures described herein. Such equivalents are considered to be within the scope of this invention and are covered by the claims.

All publications and patent applications mentioned in the specification are indicative of the level of skill of those skilled in the art to which this invention pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.” Throughout this application, the term “about” is used to indicate that a value includes the inherent variation of error for the device, the method being employed to determine the value, or the variation that exists among the study subjects.

As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps. In embodiments of any of the compositions and methods provided herein, “comprising” may be replaced with “consisting essentially of” or “consisting of”. As used herein, the phrase “consisting essentially of” requires the specified integer(s) or steps as well as those that do not materially affect the character or function of the claimed invention. As used herein, the term “consisting” is used to indicate the presence of the recited integer (e.g., a feature, an element, a characteristic, a property, a method/process step or a limitation) or group of integers (e.g., feature(s), element(s), characteristic(s), propertie(s), method/process steps or limitation(s)) only.

The term “or combinations thereof” as used herein refers to all permutations and combinations of the listed items preceding the term. For example, “A, B, C, or combinations thereof” is intended to include at least one of: A, B, C, AB, AC, BC, or ABC, and if order is important in a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB. Continuing with this example, expressly included are combinations that contain repeats of one or more item or term, such as BB, AAA, AB, BBC, AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan will understand that typically there is no limit on the number of items or terms in any combination, unless otherwise apparent from the context.

As used herein, words of approximation such as, without limitation, “about”, “substantial” or “substantially” refers to a condition that when so modified is understood to not necessarily be absolute or perfect but would be considered close enough to those of ordinary skill in the art to warrant designating the condition as being present. The extent to which the description may vary will depend on how great a change can be instituted and still have one of ordinary skilled in the art recognize the modified feature as still having the required characteristics and capabilities of the unmodified feature. In general, but subject to the preceding discussion, a numerical value herein that is modified by a word of approximation such as “about” may vary from the stated value by at least ±1, 2, 3, 4, 5, 6, 7, 10, 12 or 15% from the stated value.

All of the methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims.