Patent Publication Number: US-2022219802-A1

Title: Aircraft wing control

Description:
FIELD 
     The present disclosure relates to the design of vehicles, such as unmanned aerial vehicles, and in particular to the structure and control of wings for such vehicles. 
     BACKGROUND 
     Many types of vehicles use aerodynamic elements to improve their performance, for example to generate downforce or other desirable forces on the vehicle. For example high performance cars can comprise spoilers which may be moveable. High speed boats such as catamarans and trimarans may employ multiple hulls for greater hydrodynamic performance in comparison to mono-hull vessels. 
     Additionally, aircraft such as unmanned aerial vehicles (UAVs) are used in a range of different environments, such as for reconnaissance purposes or for the delivery of a payload. Moreover, these vehicles may be operated by a variety of different users. For example, private individuals may use them for their own recreational use, they may be deployed by military organisations to achieve a strategic goal, and increasingly commercial business are looking to utilise the capabilities that they provide. 
     The potential dangers posed by the use of UAVs, militarily or otherwise, has also lead to the development of Counter-UAV technology and systems. These systems predominantly rely on ground-based apparatus for the detection and disruption or destruction of UAVs that are deemed to pose a threat. 
     Conventional varieties of such vehicles typically use wings with fixed aerofoils, or alternatively moving rotors, to provide lift to the vehicle; and the positioning and/or movement of these and other conventional aerodynamic components may be controlled in order to control and manoeuvre the aircraft itself. 
     However, depending on the desired implementation, it may be the case that these conventional aircraft do not have a high enough level of aerodynamic performance, and conventional aerodynamic features and mechanisms may not provide the level of control and manoeuvrability required of the aircraft. 
     Improved manoeuvrability is also desirable for other types of vehicles, such as boats and underwater vessels, and land vehicles. 
     SUMMARY 
     Aspects and examples of the invention are set out in the appended claims, and aim to address at least some of the above mentioned problems and/or related problems. 
     In one aspect there is provided a vehicle comprising a morphing wing and a body, wherein the vehicle is configured to transform from a first configuration into a second configuration for ascent or descent of the vehicle, wherein the drag force and lift force on the vehicle in the second configuration are less than in the first configuration; wherein transforming from the first to the second configuration comprises: contracting the wing within a geometric plane defined by the wing; and rotating the outer edge of the wing downwards, out of the geometric plane. 
     This may enhance the manoeuvrability of the vehicle, and may enable the vehicle to have different aerodynamic properties in different flying modes, e.g. it may provide a high speed yet stable configuration of the vehicle as it rapidly ascends and/or descends, in addition to a lower speed gliding configuration, and may enable the vehicle to transition between the two. It will be understood that the terms high/low lift and drag configurations mean that during operation of the vehicle, the second low lift, low drag configuration the vehicle has a both a lower drag and lower lift force acting upon it than in the first high lift, high drag configuration. 
     The vehicle may be an aircraft, for example an unmanned aerial vehicle (UAV). Alternatively or additionally, the vehicle may be a submarine or submersible vehicle. 
     The vehicle may be configured to hold the wing in the second configuration for the ascent or descent, for example for the duration of the ascent or descent. 
     Contracting the wing within the geometric plane may comprise at least one of: reducing the angle in the geometric plane between the outer edge of the wing and the body; and retracting the outer edge towards the body in the geometric plane. Contracting the wing within a geometric plane defined by the wing may comprise reducing the area of the wing. 
     The area of the wing may be maintained during rotation downwards out of the geometric plane, for example the total surface area of the wing may remain constant, e.g. rotation may be performed without extension, retraction or rotation of the wing in the geometric plane may occur as the outer edge is rotated downwards. This may be done by providing a rotations means, such as a hinge which is operable independently from the extension mechanism of the wing. 
     Rotating the outer edge downwards out of the geometric plane may comprise forming a fluid channel bounded on a first side by an under-surface of the wing and, on a second side opposite the first side, by the body. The width of the channel is less than or equal to the width of the body. In the second configuration, the height of the channel may be at least one of: less than or equal to the height of the body; and more than or equal to ¼ the height of the body. 
     Transforming the vehicle from the first configuration to the second configuration may comprise transforming the vehicle into an intermediate configuration in which the outer edge of the wing is in a retracted position in the geometric plane. For example in this configuration the wing may be substantially planar, as in the first configuration, but may have a reduced area in comparison to the first configuration. 
     The vehicle may be further configured to transform from the second configuration into the first configuration. For example, transforming from the second configuration into the first configuration may comprise transforming the vehicle into the intermediate configuration. 
     The wing may be connected to the body by a joint, such as a hinge, about which the wing is pivotable, for example pivotable out of the geometric plane of the wing, e.g. downwards and upwards towards an under surface or top surface of the body of the vehicle respectively . The wing may comprise an extension mechanism that itself comprises an extendable frame, that for example is connected to the body by the joint. The outer edge of the extendable frame may be rotatable from the body in the geometric plane of the wing. 
     The vehicle may further comprise an actuator for moving the wing, wherein the actuator may be connected at a first end to the body, and at a second end to the extendable frame. The actuator may be configured to rotate the outer edge of the extendable frame towards the body, retract the outer edge of the wing towards the body, and rotate the outer edge of the wing downwards, out of the geometric plane, to transform the vehicle from the first configuration to the second configuration. 
     The extendable frame may comprise a plurality of longitudinal beams connected to one another by connecting beams, for example each longitudinal beam may be connected to an adjacent longitudinal beam by a pair of connecting beams. The connecting beams may be pivotably connected to the longitudinal beams to enable the longitudinal beams to be brought together and moved apart so as to extend and contract the extendable frame in the geometric plane of the frame, for example in the direction perpendicular to the orientation of the longitudinal beams. 
     The connecting beams may be of equal length such that the extendable frame is configured to extend without rotation of the outer edge of the frame. Alternatively each pair of connecting beams may comprise one beam that is longer than the other, such that the frame is to splay as it extends, to rotate the outer edge of the wing in the geometric plane of the wing, as the extendable frame expands and contracts. 
     In the second configuration, the downward span of the wing towards the outer edge may be arc shaped. For example the arc may have a curvature of at least 30 degrees. 
     The wing may be attachable and/or detachable from the body. 
     At least a portion of a leading edge of the wing may be swept forward. For example as the front edge of the wing extends away from the body it may extend towards the front of the vehicle, e.g. the outermost point of the front edge of each wing may be further forward than the point at which it connects to the body. This may provide an upstream tip of the wing which may channel air towards the body when the vehicle is in flight. For example this may direct air into the fluid channel provided between wing and the body. 
     The vehicle may further comprise at least one fan configured to provide thrust for the vehicle. For example the at least one fan may be arranged in at least one additional channel within the body (e.g. channels provided in addition to the fluid channels formed between the wings and the body), the at least one channel extending from a front surface of the body to a rear surface of the body. The fan may be a ducted fan for example an electric ducted fan, or alternatively a propeller. 
     The vehicle may further comprise at least one compartment or cavities, for example for receiving a payload (e.g. for delivery to a target site). For example the vehicle may comprise two such compartments. At least one of the compartments may comprise a compartment for a net, for example in which a net can be stored and deployed from, and then subsequently retracted to capture an object from a target site. 
     The vehicle may further comprise a controller, for example for controlling operations of the actuators and fans. The controller may be arranged in the body of the vehicle, and may be powered by a battery also arranged within the body. The vehicle may also comprise a camera for example for viewing the external environment around the vehicle. The camera may be connected to transmitter means for transmitting the images it captures to an operator on the ground and/or storage means for storing the image data it obtains. The controller may control operation of the camera and/or obtain image data from it. 
     The vehicle may be an unmanned aerial vehicle. 
     In one aspect there is provided a method of morphing a wing of an vehicle, the vehicle also comprising a body, the method comprising transforming the wing from a first, into a second configuration for ascent or descent of the vehicle; wherein the drag force and lift force on the vehicle in the second configuration are less than in the first configuration; and holding the wing in the second configuration for the ascent or descent; wherein transforming from the first to the second configuration comprises: contracting the wing within a geometric plane defined by the wing; and rotating the outer edge of the wing downwards, out of the geometric plane. The method may further comprise holding the wing in the second configuration for the ascent or descent, for example for the duration of the ascent or descent. 
     Contracting the wing within the geometric plane may comprise at least one of: reducing the angle in the geometric plane between the outer edge of the wing and the body; and, retracting the outer edge towards the body in the geometric plane. 
     Transforming from the first to the second configuration may comprise steps of: first, reducing the angle in the geometric plane between the outer edge of the wing and the body and retracting the outer edge towards the body in the geometric plane; and then, rotating the outer edge of the wing downwards, out of the geometric plane. 
     In one aspect there is provided a method of controlling a wing for an vehicle, the method comprising moving the wing from a first, high lift, high drag configuration, into a second, low lift low drag configuration for ascent or descent of the vehicle, for example for performing a stooping dive; and holding the wing in the second configuration for the ascent or descent; and moving the wing comprises rotating the outer edge of the wing downwards and towards an under-surface of the body. For example, the method may comprise holding the wing in said second configuration for the duration of an ascent or descent, and may comprise transitioning the wing into a high lift high drag configuration, e.g. the first configuration, once the vehicle ascent/descent is completed. This may enable the vehicle to transition quickly between different flight modes with different aerodynamic properties. This may enhance the manoeuvrability of the vehicle, and may provide a high speed yet stable configuration of the vehicle as it rapidly ascends and/or descends. 
     The wing may comprise an inner edge connected to a body of the vehicle, and the outer edge is positioned externally of the body, to define a wingspan; and in the first configuration the wing may have a planar wingspan, such that moving the wing into the second configuration comprises rotating the outer edge of the wing out of the geometric plane of the wingspan. 
     Moving the wing into the second configuration may comprise forming a fluid channel bounded on a first side by an under-surface of the wing and, on a second side opposite the first side, by a portion of the body. This may reduce the drag on the vehicle. 
     The outer edge of the wing may be extendable and retractable from the body in the geometric plane, and moving the wing may comprise moving the outer edge of the wing within the geometric plane of the wingspan. Moving the wing from the first configuration to the second configuration may comprise moving the wing into an intermediate configuration in which the outer edge of the wing is retracted in the geometric plane of the wingspan. 
     The method may further comprise moving the wing from the second configuration into the first configuration, for example via the intermediate configuration. Moving via the intermediate configuration may enable the vehicle to remain stable while it transitions between the two other configurations with potentially large differences in aerodynamic properties, such as the drag and lift forces acting on the vehicle. 
     Moving the wing into the intermediate configuration may comprise moving a leading edge of the wing forward. 
     The vehicle may comprise an actuator connected between the body and the wing, and moving the wing may comprise causing the actuator to apply a force on the wing. 
     The vehicle may comprise a hinge, arranged between the inner edge of the wing and the body, about which the wing is pivotable. 
     The wing may comprise a frame that is extendable in the geometric plane. The actuator may be connected to the hinge and the extendable frame, and moving the wing may comprise causing the actuator to apply a force to rotate the wing and to extend the frame. 
     In the second configuration, the outer edge of the wing may be positioned down the height of the body relative to the inner edge. 
     In the second configuration, the wingspan between the inner and outer edges of the wing may be arc shaped, for example the arc may have a curvature of at least 30 degrees. 
     In the second configuration, the surface area of an inner surface of the wing may be at least 20% of the area of a side of the body connected to the wing. 
     The vehicle may be an unmanned aerial vehicle. 
     A controller for controlling a wing for an vehicle may be provided to perform the methods described herein. An vehicle, for example an unmanned aerial vehicle such as the vehicle described herein, may comprise the controller. 
     In one aspect there is provided an vehicle comprising a body and a wing, wherein the wing is connected to the body and wherein, in a low lift low drag configuration of the vehicle the wing comprises an inner edge connected to the body, and an outer edge positioned outwardly from the body to define a wingspan therebetween, and wherein the wing is shaped to define a fluid channel bounded on a first side by an under-surface of the wing and, on a second side opposite the first side, by a portion of the body; and wherein the fluid channel is arranged to provide a path for fluid to flow through the channel as the vehicle travels through the fluid to produce a lift force on the vehicle. 
     The present disclosure may provide a method of controlling such an vehicle, for example to dive or climb. The method may comprise controlling the wing of this vehicle by moving the wing from a first configuration (such as the high lift, high drag mentioned above) into a second configuration (in which the lift provided by the wing and or the drag provided by the wing may be lower relative to the first configuration). This second configuration may be used for the dive or climb, e.g. to provide rapid ascent or descent of the vehicle. The method comprises holding the wing in the second configuration for the ascent or descent and moving the wing comprises rotating the outer edge of the wing downwards, and towards an under-surface of the body. The wing of this vehicle may be controlled according to any one or more of the methods described or claimed herein. 
     In the second configuration, the wing may be cupped to provide the fluid channel. In the second configuration, the outer edge of the wing may be positioned lower than the inner edge (for example lower down the height of the body relative to the inner edge). In the configuration, the wingspan between the inner and outer edges may be curved, for example it may be arc shaped. The wing (e.g. the arc) may have a curvature of at least 30 degrees. 
     In the low lift low drag configuration, the area of the wing span between the inner edge and the outer edge may be greater than at least 20% of an area of a side of the body, for example of a side of the body connected to the wing. 
     To provide the rotating motion, the wing may be pivotable relative the body. For example, the vehicle may comprise a hinge, arranged between the inner edge of the wing and the body, about which the wing may be pivotable. 
     The wing may be extendable (e.g. to increase its length) thereby to move the outer edge of the wing away from the vehicle in the geometric plane of the vehicle&#39;s wings. One way to achieve this is that the wing may comprise an extendable frame. 
     The vehicle may comprise an actuator connected to the body and the wing, and the actuator may be configured to apply a force to the wing (e.g. by providing a moment about the hinge) to rotate the wing downward or upward relative to the body. 
     The actuator may be configured to adjust the position of the outer edge of the wing relative to the body. For example, the actuator may be configured to outwardly extend and/or inwardly retract the extendable frame. For example the actuator may be configured to expand and/or retract the frame. The frame may have a compressible structure, for example it may be articulated, for example it may comprise a plurality of interconnected rods that provide a folding structure. 
     The actuator may be connected to the hinge and the extendable frame, for applying said force to rotate the wing and to extend the frame. This may enable the same actuator to provide both the extending and rotating movement of the wing. 
     The wing may comprise a plurality of adjacent elements arranged between the inner and outer edges, and each element may be moveable relative to each other element. For example they may be mutually connected by pivoting couplings, such as in the manner of lazy-tongs. The adjacent elements may partially overlap with one another in the direction between the inner and outer edges of the wing. The elements comprise at least one of, feather-like elements, and plate-like elements. In one aspect there is provided a method of controlling a wing for a vehicle, wherein the wing is pivotably connected at an inner edge to a body of a vehicle, and further comprises an outer edge positioned outwardly from the body and down the body from the inner edge; wherein the method comprises rotating the wing between a low lift low drag configuration, in which the wing defines a fluid channel bounded on a first side by an under-surface of the wing and, on a second side opposite the first side, by a portion of the body; and the fluid channel is arranged to provide a path for fluid to flow through the channel as the vehicle travels through the fluid to produce a lift force on the vehicle; and a high lift high drag position in which the angle between the wing and the body is reduced in comparison to the first position. 
     In one aspect there is provided an apparatus for controlling the wing of a vehicle, wherein the wing is pivotably connected to a body of a vehicle, and the apparatus is configured to rotate the wing between a low lift low drag configuration, in which the wing defines a fluid channel bounded on a first side by an under-surface of the wing and, on a second side opposite the first side, by a portion of the body; and the fluid channel is arranged to provide a path for fluid to flow through the channel as the vehicle travels through the fluid to produce a lift force on the vehicle; and a high lift high drag configuration in which the angle between the wing and the body is reduced in comparison to the first position. 
     The outer edge of the wing may be outwardly extendable from the body, and the apparatus may be further configured to at least one of extend and retract the outer edge of the wing, for example in the geometric plane defined by the wing in the high lift high drag configuration. 
     In one aspect there is provided an aircraft comprising a morphing wing and a body, wherein the aircraft is configured to transform from a first configuration into a second configuration for ascent or descent of the aircraft, wherein the drag force and lift force on the aircraft in the second configuration are less than in the first configuration; wherein transforming from the first to the second configuration comprises: contracting the wing within a geometric plane defined by the wing; and rotating the outer edge of the wing downwards, out of the geometric plane. 
     This may enhance the manoeuvrability of the aircraft, and may enable the aircraft to have different aerodynamic properties in different flying modes, e.g. it may provide a high speed yet stable configuration of the aircraft as it rapidly ascends and/or descends, in addition to a lower speed gliding configuration, and may enable the aircraft to transition between the two. It will be understood that the terms high/low lift and drag configurations mean that during operation of the aircraft, the second low lift, low drag configuration the aircraft has a both a lower drag and lower lift force acting upon it than in the first high lift, high drag configuration. 
     The aircraft may be configured to hold the wing in the second configuration for the ascent or descent, for example for the duration of the ascent or descent. 
     Contracting the wing within the geometric plane may comprise at least one of: reducing the angle in the geometric plane between the outer edge of the wing and the body; and retracting the outer edge towards the body in the geometric plane. Contracting the wing within a geometric plane defined by the wing may comprise reducing the area of the wing. 
     The area of the wing may be maintained during rotation downwards out of the geometric plane, for example the total surface area of the wing may remain constant, e.g. rotation may be performed without extension, retraction or rotation of the wing in the geometric plane may occur as the outer edge is rotated downwards. This may be done by providing a rotations means, such as a hinge which is operable independently from the extension mechanism of the wing. 
     Rotating the outer edge downwards out of the geometric plane may comprise forming a fluid channel bounded on a first side by an under-surface of the wing and, on a second side opposite the first side, by the body. The width of the channel is less than or equal to the width of the body. In the second configuration, the height of the channel may be at least one of: less than or equal to the height of the body; and more than or equal to ¼ the height of the body. 
     Transforming the aircraft from the first configuration to the second configuration may comprise transforming the aircraft into an intermediate configuration in which the outer edge of the wing is in a retracted position in the geometric plane. For example in this configuration the wing may be substantially planar, as in the first configuration, but may have a reduced area in comparison to the first configuration. 
     The aircraft may be further configured to transform from the second configuration into the first configuration. For example, transforming from the second configuration into the first configuration may comprise transforming the aircraft into the intermediate configuration. 
     The wing may be connected to the body by a joint, such as a hinge, about which the wing is pivotable, for example pivotable out of the geometric plane of the wing, e.g. downwards and upwards towards an under surface or top surface of the body of the aircraft respectively . The wing may comprise an extension mechanism that itself comprises an extendable frame, that for example is connected to the body by the joint. The outer edge of the extendable frame may be rotatable from the body in the geometric plane of the wing. 
     The aircraft may further comprise an actuator for moving the wing, wherein the actuator may be connected at a first end to the body, and at a second end to the extendable frame. The actuator may be configured to rotate the outer edge of the extendable frame towards the body, retract the outer edge of the wing towards the body, and rotate the outer edge of the wing downwards, out of the geometric plane, to transform the aircraft from the first configuration to the second configuration. 
     The extendable frame may comprise a plurality of longitudinal beams connected to one another by connecting beams, for example each longitudinal beam may be connected to an adjacent longitudinal beam by a pair of connecting beams. The connecting beams may be pivotably connected to the longitudinal beams to enable the longitudinal beams to be brought together and moved apart so as to extend and contract the extendable frame in the geometric plane of the frame, for example in the direction perpendicular to the orientation of the longitudinal beams. 
     The connecting beams may be of equal length such that the extendable frame is configured to extend without rotation of the outer edge of the frame. Alternatively each pair of connecting beams may comprise one beam that is longer than the other, such that the frame is to splay as it extends, to rotate the outer edge of the wing in the geometric plane of the wing, as the extendable frame expands and contracts. 
     In the second configuration, the downward span of the wing towards the outer edge may be arc shaped. For example the arc may have a curvature of at least 30 degrees. 
     The wing may be attachable and/or detachable from the body. 
     At least a portion of a leading edge of the wing may be swept forward. For example as the front edge of the wing extends away from the body it may extend towards the front of the aircraft, e.g. the outermost point of the front edge of each wing may be further forward than the point at which it connects to the body. This may provide an upstream tip of the wing which may channel air towards the body when the aircraft is in flight. For example this may direct air into the fluid channel provided between wing and the body. 
     The aircraft may further comprise at least one fan configured to provide thrust for the aircraft. For example the at least one fan may be arranged in at least one additional channel within the body (e.g. channels provided in addition to the fluid channels formed between the wings and the body), the at least one channel extending from a front surface of the body to a rear surface of the body. The fan may be a ducted fan for example an electric ducted fan, or alternatively a propeller. 
     The aircraft may further comprise at least one compartment or cavities, for example for receiving a payload (e.g. for delivery to a target site). For example the aircraft may comprise two such compartments. At least one of the compartments may comprise a compartment for a net, for example in which a net can be stored and deployed from, and then subsequently retracted to capture an object from a target site. 
     The aircraft may further comprise a controller, for example for controlling operations of the actuators and fans. The controller may be arranged in the body of the aircraft, and may be powered by a battery also arranged within the body. The aircraft may also comprise a camera for example for viewing the external environment around the aircraft. The camera may be connected to transmitter means for transmitting the images it captures to an operator on the ground and/or storage means for storing the image data it obtains. The controller may control operation of the camera and/or obtain image data from it. 
     The aircraft may be an unmanned aerial vehicle. 
     In one aspect there is provided a method of morphing a wing of an aircraft, the aircraft also comprising a body, the method comprising transforming the wing from a first, into a second configuration for ascent or descent of the aircraft; wherein the drag force and lift force on the aircraft in the second configuration are less than in the first configuration; and holding the wing in the second configuration for the ascent or descent; wherein transforming from the first to the second configuration comprises: contracting the wing within a geometric plane defined by the wing; and rotating the outer edge of the wing downwards, out of the geometric plane. The method may further comprise holding the wing in the second configuration for the ascent or descent, for example for the duration of the ascent or descent. 
     Contracting the wing within the geometric plane may comprise at least one of: reducing the angle in the geometric plane between the outer edge of the wing and the body; and, retracting the outer edge towards the body in the geometric plane. 
     Transforming from the first to the second configuration may comprise steps of: first, reducing the angle in the geometric plane between the outer edge of the wing and the body and retracting the outer edge towards the body in the geometric plane; and then, rotating the outer edge of the wing downwards, out of the geometric plane. 
     In one aspect there is provided a method of controlling a wing for an aircraft, the method comprising moving the wing from a first, high lift, high drag configuration, into a second, low lift low drag configuration for ascent or descent of the aircraft, for example for performing a stooping dive; and holding the wing in the second configuration for the ascent or descent; and moving the wing comprises rotating the outer edge of the wing downwards and towards an under-surface of the body. For example, the method may comprise holding the wing in said second configuration for the duration of an ascent or descent, and may comprise transitioning the wing into a high lift high drag configuration, e.g. the first configuration, once the aircraft ascent/descent is completed. This may enable the aircraft to transition quickly between different flight modes with different aerodynamic properties. This may enhance the manoeuvrability of the aircraft, and may provide a high speed yet stable configuration of the aircraft as it rapidly ascends and/or descends. 
     The wing may comprise an inner edge connected to a body of the aircraft, and the outer edge is positioned externally of the body, to define a wingspan; and in the first configuration the wing may have a planar wingspan, such that moving the wing into the second configuration comprises rotating the outer edge of the wing out of the geometric plane of the wingspan. 
     Moving the wing into the second configuration may comprise forming a fluid channel bounded on a first side by an under-surface of the wing and, on a second side opposite the first side, by a portion of the body. This may reduce the drag on the aircraft. 
     The outer edge of the wing may be extendable and retractable from the body in the geometric plane, and moving the wing may comprise moving the outer edge of the wing within the geometric plane of the wingspan. Moving the wing from the first configuration to the second configuration may comprise moving the wing into an intermediate configuration in which the outer edge of the wing is retracted in the geometric plane of the wingspan. 
     The method may further comprise moving the wing from the second configuration into the first configuration, for example via the intermediate configuration. Moving via the intermediate configuration may enable the aircraft to remain stable while it transitions between the two other configurations with potentially large differences in aerodynamic properties, such as the drag and lift forces acting on the aircraft. 
     Moving the wing into the intermediate configuration may comprise moving a leading edge of the wing forward. 
     The aircraft may comprise an actuator connected between the body and the wing, and moving the wing may comprise causing the actuator to apply a force on the wing. 
     The aircraft may comprise a hinge, arranged between the inner edge of the wing and the body, about which the wing is pivotable. 
     The wing may comprise a frame that is extendable in the geometric plane. The actuator may be connected to the hinge and the extendable frame, and moving the wing may comprise causing the actuator to apply a force to rotate the wing and to extend the frame. 
     In the second configuration, the outer edge of the wing may be positioned down the height of the body relative to the inner edge. 
     In the second configuration, the wingspan between the inner and outer edges of the wing may be arc shaped, for example the arc may have a curvature of at least 30 degrees. 
     In the second configuration, the surface area of an inner surface of the wing may be at least 20% of the area of a side of the body connected to the wing. 
     The aircraft may be an unmanned aerial vehicle. 
     A controller for controlling a wing for an aircraft may be provided to perform the methods described herein. An aircraft, for example an unmanned aerial vehicle such as the aircraft described herein, may comprise the controller. 
     In one aspect there is provided an aircraft comprising a body and a wing, wherein the wing is connected to the body and wherein, in a low lift low drag configuration of the aircraft the wing comprises an inner edge connected to the body, and an outer edge positioned outwardly from the body to define a wingspan therebetween, and wherein the wing is shaped to define a fluid channel bounded on a first side by an under-surface of the wing and, on a second side opposite the first side, by a portion of the body; and wherein the fluid channel is arranged to provide a path for fluid to flow through the channel as the aircraft travels through the fluid to produce a lift force on the aircraft. 
     The present disclosure may provide a method of controlling such an aircraft, for example to dive or climb. The method may comprise controlling the wing of this aircraft by moving the wing from a first configuration (such as the high lift, high drag mentioned above) into a second configuration (in which the lift provided by the wing and or the drag provided by the wing may be lower relative to the first configuration). This second configuration may be used for the dive or climb, e.g. to provide rapid ascent or descent of the aircraft. The method comprises holding the wing in the second configuration for the ascent or descent and moving the wing comprises rotating the outer edge of the wing downwards, and towards an under-surface of the body. The wing of this aircraft may be controlled according to any one or more of the methods described or claimed herein. 
     In the second configuration, the wing may be cupped to provide the fluid channel. In the second configuration, the outer edge of the wing may be positioned lower than the inner edge (for example lower down the height of the body relative to the inner edge). In the configuration, the wingspan between the inner and outer edges may be curved, for example it may be arc shaped. The wing (e.g. the arc) may have a curvature of at least 30 degrees. 
     In the low lift low drag configuration, the area of the wing span between the inner edge and the outer edge may be greater than at least 20% of an area of a side of the body, for example of a side of the body connected to the wing. 
     To provide the rotating motion, the wing may be pivotable relative the body. For example, the aircraft may comprise a hinge, arranged between the inner edge of the wing and the body, about which the wing may be pivotable. 
     The wing may be extendable (e.g. to increase its length) thereby to move the outer edge of the wing away from the aircraft in the geometric plane of the aircraft&#39;s wings. One way to achieve this is that the wing may comprise an extendable frame. 
     The aircraft may comprise an actuator connected to the body and the wing, and the actuator may be configured to apply a force to the wing (e.g. by providing a moment about the hinge) to rotate the wing downward or upward relative to the body. 
     The actuator may be configured to adjust the position of the outer edge of the wing relative to the body. For example, the actuator may be configured to outwardly extend and/or inwardly retract the extendable frame. For example the actuator may be configured to expand and/or retract the frame. The frame may have a compressible structure, for example it may be articulated, for example it may comprise a plurality of interconnected rods that provide a folding structure. 
     The actuator may be connected to the hinge and the extendable frame, for applying said force to rotate the wing and to extend the frame. This may enable the same actuator to provide both the extending and rotating movement of the wing. 
     The wing may comprise a plurality of adjacent elements arranged between the inner and outer edges, and each element may be moveable relative to each other element. For example they may be mutually connected by pivoting couplings, such as in the manner of lazy-tongs. The adjacent elements may partially overlap with one another in the direction between the inner and outer edges of the wing. The elements comprise at least one of, feather-like elements, and plate-like elements. 
     In one aspect there is provided a method of controlling a wing for a vehicle, wherein the wing is pivotably connected at an inner edge to a body of a vehicle, and further comprises an outer edge positioned outwardly from the body and down the body from the inner edge; wherein the method comprises rotating the wing between a low lift low drag configuration, in which the wing defines a fluid channel bounded on a first side by an under-surface of the wing and, on a second side opposite the first side, by a portion of the body; and the fluid channel is arranged to provide a path for fluid to flow through the channel as the aircraft travels through the fluid to produce a lift force on the aircraft; and a high lift high drag position in which the angle between the wing and the body is reduced in comparison to the first position. 
     In one aspect there is provided an apparatus for controlling the wing of a vehicle, wherein the wing is pivotably connected to a body of a vehicle, and the apparatus is configured to rotate the wing between a low lift low drag configuration, in which the wing defines a fluid channel bounded on a first side by an under-surface of the wing and, on a second side opposite the first side, by a portion of the body; and the fluid channel is arranged to provide a path for fluid to flow through the channel as the aircraft travels through the fluid to produce a lift force on the aircraft; and a high lift high drag configuration in which the angle between the wing and the body is reduced in comparison to the first position. 
     The outer edge of the wing may be outwardly extendable from the body, and the apparatus may be further configured to at least one of extend and retract the outer edge of the wing, for example in the geometric plane defined by the wing in the high lift high drag configuration. 
     The outer edge may be the edge of the wing positioned externally of the body, for example the edge of the wing not on the body and/or not directly connected to the body. 
     The outer edge of the wing may be the portion of the wing comprising the outermost point of the wing, e.g. the point furthest from the body, for example the point furthest from the inner edge of the wing connected to the body. The outer edge of the wing may be the portion of the wing comprising the outermost point of the wing in at least one of the first configuration, the second configuration, and the intermediate configuration. The outer edge of the wing may be the leading edge of the wing. The outer edge may be provided by a wing cover, for example an edge of a wing cover. 
     Each of the foregoing aspects may be further refined as set out in the examples described herein. Aspects of the disclosure may be provided in conjunction with each other, and features of one aspect may be applied to other aspects. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Embodiments of the disclosure will now be described with reference to the accompanying drawings, in which: 
         FIGS. 1A-B  illustrate an example aircraft having a pair of static wings; 
         FIGS. 2A-B  illustrate an example aircraft comprising a pair of moveable wings; 
         FIGS. 3A-C  illustrate the aircraft with wings in different configurations; 
         FIG. 4  illustrates several examples of the aircraft in use; 
         FIG. 5  gives cutaway side and top view of the interior of an example aircraft; 
         FIG. 6  illustrates an aircraft with wings at various stages of transformation between configurations; 
         FIG. 7  illustrates the airflow around an aircraft in a particular configuration; and 
         FIG. 8A and 8B  illustrate example frames for a wing of an aircraft. 
     
    
    
     In the drawings like reference numerals are used to indicate like elements. 
     SPECIFIC DESCRIPTION 
     Described herein with reference to the figures are vehicles having particular wing configurations and shapes, which may improve the aerodynamic efficiency and manoeuvrability of the vehicle. Also described herein are methods for controlling such wings, including altering the shape of the wing, e.g. whilst the vehicle is travelling, which may improve performance and provide different aerodynamic properties of the vehicle for different modes of operation of the vehicle. The enhanced manoeuvrability and aerodynamic properties of such aircraft may enable their use in fields such as counter-UAS technology, for example to aid in the disruption or destruction of other aircraft. 
       FIG. 1A  illustrates a cross-sectional front view of an example aircraft  10 , in particular an unmanned aerial vehicle.  FIG. 1B  gives a perspective view of the same aircraft  10 . Aircraft  100  comprises a body  12  that has a substantially tubular shape. The body  12  is connected at its back end to a tail section  16 , and at its front end to a nose section  18 . The body  12  narrows towards the tail section  16  and towards the nose section  18 , and is laterally symmetrical about its central axis. The body  12  has a top surface  22 , a bottom surface  24 , and  2  curved side surfaces  26  that connect the top surface  22  to the bottom surface  24 . The bottom surface  24  and top surface  22  are also curved. The body  12  also comprises a payload space  28  at the bottom surface which may receive a payload for example to deliver to a target. Such a payload may comprise, a pyrotechnic or other explosive device, a net deployer or a signal jamming payload. 
     The nose section  18  is arranged at the front of the aircraft  100  and is connected to the front of the body  22 . The nose section is substantially conically shaped with a rounded tip provided at the front end of the aircraft  10 . The tail section  16  is arranged at the rear of the aircraft  10  and is connected to the back of the body  22 . The tail section  16  comprises a pair of lateral fins  13  that extend either side of the body  12 , and each of the lateral fins  13  is connected at its respective outer edge to a vertical fin  15  that extends vertical upwardly from the outer edge of the lateral fins  13 . In operation, while the aircraft is flying, the tail section acts to stabilise the aircraft  100 . 
     The aircraft further comprises a pair of wings  14   a,    14   b,  connected to the body at a point along the side surfaces  26   a,    26   b.  The wings  14   a,    14   b  are fixedly connected to the body  12  at along the side of each side surface  26 . In particular the wings  14   a,    14   b  comprise an inner edge  17  that connects along its length to one of the side surfaces  26  of the body  12 . Each of the wings  14   a,b  also comprise an outer edge  19  that is positioned outwardly from the body  12  and which is positioned down the height of the body  12  from the inner edge  17 . A wingspan is thereby defined between the inner edge  17  and the outer edge  19 . This wingspan extends over at least 30% of the height of the side surface  26  of the body  12 , for example at least 40%, for example at least 50%. The wings  14  further comprise an under-surface  21  that faces towards the body  12 , and a top surface  23  facing away from the body  12 , wherein each surface connects the inner edge  17  to the outer edge  19  of the wing. The inner surface  21  of the wing is curved so as to provide an arc-shape to the wing  14 . This arc is shaped such that it has a curvature of at least 30 degrees. Due to the respective shapes of the wing  14  and the body  12 , a fluid channel  20   a,    20   b  is provided between each wing  14   a,    14   b  and the body. During operation of the aircraft  10 , that is, while the aircraft  10  is flying, the fluid channels  20  provide a path for air to flow through the channel. The flow of air through the channel  20  minimises the drag force experienced by the aircraft  10 , thereby enabling the aircraft  10  to travel stably at high speed, for example during a rapid ascent or descent (e.g. swooping) of the aircraft  10 . The air flow may also produce a lift force on the aircraft  10 . 
     The channels  20  defined between each wing  14  and the body  12  have a width, e.g. a greatest width, which is less than the total greatest width of the body. For example the channel may have a width less than half that of the body. This may enable each wing  14  to channel a flow of air close to the body  12  when the aircraft  10  is flying, thereby improving the aerodynamic efficiency of the aircraft  10  and further reducing drag. 
     The channels  20  are less than or equal to the height of the body. In examples other than that shown in  FIG. 1A , each wing  14  may extend from the top of the body  12 , such that a channel is defined down the entire height of the body. The wings  14  shown extend no lower than the lowest extent of the body  12 , for example to minimize the upstream edge of the wing and limit drag. However, the wings  14  may in some examples extend below the body  12 . The vertical extent of the wing, and thereby the height of the channel, may be at least ¼ the height of the body, for example at least ½ the height of the body. 
     It will be understood that the curvature, size and positioning of the wings  14  shown in  FIG. 1A  are merely exemplary, and that the wings and therefore the channels formed between the wings and the body may have many different shapes and sizes in different examples. 
     The aircraft may comprise one or more fans (not shown), such as a ducted fan, to generate thrust for the aircraft. The fans may be powered electrically from a power source arranged within the body  12  of the aircraft  10 , and may be arranged in channel(s) in the body  12  that extend from a front surface of the aircraft to a rear surface to provide an air flow path. For example two channels containing such fans may extend through the body  12  each having inlets at a front face of the body below the nose section  18 , and arranged symmetrically either side of the longitudinal axis of the aircraft  10 . Providing the fans in such an arrangement may enable thrust to be provided to the aircraft whilst maintaining the aerodynamic shape of the aircraft, and without interfering with the air flow through the channels  20  between the wings  23  and the body  12 . 
     The aircraft may alternatively comprise a propeller, or multiple propellers, that generate thrust for the aircraft  10 . The propeller can be connected either to the nose section  18  or the tail section  16  of the aircraft  10 . The propeller is connected to and powered by a power source contained within the body  12  of the aircraft  10 . The propeller may preferably be provided at the tail section  16  so as to minimize interference with the air flow through the fluid channels  20 . 
     The aircraft  10  also comprises a guidance system that comprises a system of cameras and avionics (not shown) that enable the aircraft  10  to be manoeuvred remotely. 
       FIGS. 2A and 2B  illustrate the component parts of an aircraft  100  that has a pair of moveable wings  114  and a mechanism for moving and/or altering the shape of the wings. The aircraft  100  comprises a body  112  with a structure substantially the same as the body  12  described with reference to  FIG. 1 . However, the body  112  of the aircraft  100  is formed of two connectable parts, fuselage  112   a  and cover  112   b.  The fuselage  112   a  extends from a nose section  18  to a tail section  16 , wherein the nose section  18  and tail section  16  are as described with reference to the aircraft  10  of  FIG. 1 . The fuselage  112   a  is substantially tubular in shape, but the width of a lower portion of the fuselage  112   a  is increased in a middle section between the nose  18  and tail  16  sections. The body  112  further comprises an aerodynamically shaped cover  112   b  for positioning over the fuselage  11   a.    
     The aircraft  100  comprises a moveable wing  114 , the structure of which is shown clearly in  FIG. 2B . The moveable wing  114  comprises an extension frame  120  and a support frame  122 . The extension frame  120  comprises an articulated structure of interconnected beams  121 . The extension frame  120  is extendable and compressible such that an outer edge of the wing is moveable towards and away from an inner edge of the wing and the body  112 . The extension frame  120  is connected to an actuator  128 , which is also connected to the body  112 . The extension frame  120  is further pivotably connected to the body via a 90 degree hinge  126 . The actuator  128  is a linear actuator, but in other examples the aircraft may comprise “rack and pinion” or piston type actuator. The actuator  128  is powered by an electrical machine (such as a motor) which may be located within the body (not shown). For example, a rod or other mechanical linkage may connect the actuator to the frame via an inlet in the body  112 . The actuator is operable to provide an outward force to the extension frame  120  to rotate the extension frame  120  about the hinge  126  and to extend the extension frame  120  (described in more detail with reference to  FIG. 3 ). As shown in  FIG. 2B  the actuator  18  is connected to the extension frame  120  at an underside of the extension frame  120 , and below the hinge. This enables a single actuator, upon application of an outward force to the frame  120 , to first fully rotate the wing  114  upwards, and, upon continuation of the application of the force, to then cause extension of the extension frame  120  itself. Furthermore, as described in more detail below, in extending the extension frame  120 , the actuator provides in-plane rotation of the outer edge of the wing  114 . 
     The wing  114  further comprises a support frame  122  and a wing cover  124 . The support frame  122  is connected to the extension frame  120  by connectors  127 , and is arranged to sit on top of the extension frame  120  in operation. The support frame  122  also comprises an articulated structure that comprises a plurality of adjacent longitudinal beams  123  that are connected together by connecting beams  125 . As such the support frame  122  is also extendable and compressible, and when connected to the extension frame  120  is configured to extend with the extension frame  120  as it is extended by the actuator  128 . The outermost longitudinal beam  123  is also rotatable in the geometric plane defined by the wing, such that upon full extension by the actuator  128 , that beam rotates (e.g. kicks or sweeps) outward relative to the other beams of the support frame  122  as shown in  FIG. 2A . The outer edge of the wing  114  provided by the wing cover  124  is thus rotatable away from and towards the body in the plane of the wing as the frame extends and retracts respectively, upon operation of the actuator  128 . The total area of the wing  114  is therefore variable, and can be increased and decreased due to the in-plane extension and retraction of the frame, and the rotation of the outer edge. 
     In some examples the actuator may have an in-built sensor that is configured to measure the forces applied by the actuator to the wing and/or the forces applied to wing or to the actuator itself. This information can be provided to a controller that controls operation of the actuators (described in more detail below), for example so that operation of the actuators may be controlled based on environmental conditions. For example, in different modes of flight the forces acting on the aircraft as a whole, and in particular on the wing and actuator may vary—e.g. based on the speed, acceleration, orientation of the aircraft, or the position of the wing. For example, during operation there may be times where operation of the actuator would be unsafe or would cause the aircraft to become unstable, due to the forces acting on the aircraft. 
     The wing cover  124  is configured so that it can be placed over the support frame  122 . In particular the wing cover is attached to the outer edge of the support frame  122 . The wing cover is shaped such that, when the wing  122  is fully rotated downwards on the hinge  126 , the shape of the wing is substantially the same as that described for the fixed wing  14  with reference to  FIG. 1 . That is, the curvature of the wing  114 , and the flow channels provided between each wing  114  and the body  112  are substantially as described above. 
     The aircraft  100  further comprises ducted fans powered electrically and arranged in fluid channels within the body substantially as described above with reference to aircraft  10  of  FIG. 1 . For example, the ducted fans may be positioned within the body  112  of the aircraft  100 , and may be arranged in channel(s) in the body  112  that extend from a front surface of the aircraft to a rear surface to provide an air flow path. Alternatively the aircraft may comprise a propeller arranged as described above with reference to  FIG. 1 . The aircraft  100  also comprises a payload space and guidance system as described above in relation to the aircraft  10  of  FIG. 1 . 
     The wing cover  124  may comprise a plurality of feather or plate like elements (not shown), arranged longitudinally along a length of the cover. Each element may overlap with its adjacent element(s). 
     The body  112  and the wing cover  124  are made of polystyrene. However, in other examples they may be made of carbon fibre, for example they could be provided as a carbon fibre shell, or other materials such as robust lightweight materials including plastic and cardboard could be used. The components may be manufactured using a laser cutting technique, for example they may be formed of a plurality of laser cut layers of the material. In other examples 3D printing is used to produce these components. 
     Similarly, the extension frame  120  and the support frame  122  may be made of a plastic material, for example laminated plastic, or other robust lightweight materials such as those mentioned above. 
     The aircraft  100  comprises a first wing and a second wing on either side of the body, and is substantially laterally symmetric about its central axis. Both wings have the structure and function as described above, and each actuator is operable independently such that the shape and position of each wing can be controlled independently. In this way the roll of the aircraft  100  can be controlled. 
     It will be understood that at least one controller (not shown) may be configured to operate the actuators  128  of the aircraft  100 . For example a single controller may control both actuators, or two separate controllers may control each actuator independently. The controller(s) may be arranged in the aircraft  100 , and may be powered by a power source contained in the aircraft  100 , and electrically connected to the actuators  128 . In other examples the aircraft may be controlled remotely, for example from the ground. The aircraft  100  may be configured to receive a signal from a controller on the ground, for example via a radio frequency antenna, and provide this signal to the actuators  128  to control their operation. The controller may be configured to control the aircraft  100  based on information received from the aircraft  100 , e.g. from sensors on the aircraft such as the avionics and actuator sensors described above. 
       FIGS. 3A-C  show examples of the different wing configurations that aircraft  100  described above can have and transition between. 
       FIG. 3A  shows the aircraft in a first, high lift, high drag configuration. In this configuration the extension frame  120  is fully extended outwards from the body  112  such that the wing cover is  124  is spaced from the body  112 . In this configuration the wing  114  is substantially planar, with a geometric plane defined between the inner edge of the wing connected to the body  112  and the outer edge of the wing provided by the wing cover  124 . It will be understood that the wing  114  in this configuration is not an entirely flat plane as the wing cover  124  has a degree of curvature. The wing  114  extends at substantially 90 degrees from the body  112  about the hinge  126 . In operation the exposed portion of the wing around the extension frame  120  may be covered by a foldable material connected to the either the extension frame  120  or the support frame  122 . In this configuration, the outermost longitudinal beam of the support frame is fully swept out such that the outer edge of the wing  124  is at an oblique angle to the body and extends outward from its front end to its rear end. In some examples in this configuration the outer edge of the wing is substantially perpendicular to the body  112 . 
     The aircraft  100  comprises a pair of motors  130  connectable to the actuators  128  of each respective wing  114  via an inlet in the side of the body  112 . For example the actuator may comprise a linear rod that is extendable and retractable by the motor  130 , or the actuator may comprise the rod and the motor  130 . Upon activation of the motor the actuator  128  retracts so as to exert an inward force on the wing  114  through its connection to the extension frame  122 . In response to this force the extension frame  128  folds inwards and retracts the outer edge of the wing  114  towards the body  112  in plane. Additionally, as the extension frame  128  is retracted the outer edge of the wing (attached to the outermost beam of the support frame—and thereby moveable in the plane of the wing as described above) rotates towards the body  112 , that is, the angle between the outer edge of the wing and the body is reduced in the plane of the wing. 
     Once the frame has been fully retracted it is in an intermediate configuration shown in  FIG. 3B . In this configuration the extension frame  120  is fully compressed, while the wing  114  still extends at substantially 90 degrees from the body  112  about the hinge  126 . 
     In this configuration, the aircraft  100  is in a substantially “M”-shaped formation, due to the curvature of the wing cover  124 . 
     Upon further retraction of the actuator  130  the wing is rotated downwards about the 90 degree hinge  126 , such that the outer surface of the wing is rotated out of the original plane of the wing and towards an under-surface of the body. Once the wing  114  has been rotated through 90 degrees, it is in a low lift low drag configuration, shown in  FIG. 3C . 
       FIG. 3C  shows the aircraft with both wings in a low lift low drag cupped configuration. In this configuration the extension frame is fully compressed, and, because the actuator  128  is fully retracted, the wing extends directly downwards from the hinge  126 . In this configuration, the shape of the aircraft  100 , in particular the shape of the wings  114  and the body  112  is substantially the same as that described above in relation to  FIG. 1 . In particular a fluid channel, such as is described above is provided between the inner surface of the wings  114  and the side surface of the body  112 . 
     The actuator can further be operated in reverse to provide an outward force to the extension frame  120 . In this case, when the aircraft is in the  FIG. 3C  configuration, the actuator can apply an outward force to the frame  120  to rotate the frame upwards 90 degrees about the hinge  126  such that the aircraft returns to the intermediate configuration. Upon further extension of the actuator, the extension frame  120  is expanded to extend the frame such that the outer edge of the frame  120  moves away from the body  112  of the aircraft  100 , and the outer edge of the wing is rotated outwards in the plane of the wing, away from the body. The extension frame  122  can be fully extended in this way, such that the wing is moved into the high lift high drag configuration. 
     In each of these configurations, the aircraft  100  has different aerodynamic properties, which may each be preferable for particular different modes of operation or activities that the aircraft is required to perform. For example the high lift high drag configuration may enable the aircraft to operate in a low speed gliding mode, at a stable altitude. The low lift low drag configuration may enable the aircraft to operate at high speeds, and to increase its speed rapidly whilst remaining stable. For example it may enable the aircraft  100  to perform high speed manoeuvres such as ‘swooping’ rapidly, or performing a stooping dive, for example towards a target. The intermediate configuration may enable the aircraft  100  to remain stable as it transitions between the first and third configurations. For example it may help to prevent the aircraft  100  from stalling as it transitions out of a high speed manoeuvre in the third configuration into a low speed glide in the high lift high drag configuration. 
     In each of the configurations described above, the wings  114  are ‘forward-swept’. That is, following the shape of the front of the wing as it extends away from the body, the front or leading edge of the wing extends forward so as to provide a front ‘tip’ of the wing, and curves backwards thereafter. This forward sweep thus provides an upstream tip as the aircraft  100  is in flight, which may channel air towards the body  112 , for example into the fluid channel provided between wings  114  and the body  112  when the aircraft  100  is in the low-lift low-drag configuration. 
     The controller (not shown) is configured to actuate the controller to transition the aircraft between the different configurations as described herein. In one example mode of the operation the controller is configured to cause the actuator to retract and thereby to transition the aircraft  100  from the high drag configuration to the low drag configuration, via the intermediate configuration. The controller may then pitch the nose  18  of the aircraft  100  down to initiate a dive, for example the aircraft  100  may dive towards a target with a payload. In other examples the aircraft may complete the dive, and the controller may then pitch up the nose  18  of the aircraft, at which point the controller further causes the actuator to extend and thereby to transition the aircraft  100  from the low drag to the high drag configuration, via the intermediate configuration. 
       FIG. 4  illustrates some examples of the various potential uses of the aircraft  100 , in particular within a military environment. In particular it shows example operational capabilities that may be enabled or enhanced by the aircraft&#39;s wing modalities: 
     1—Ground launch. Example applicable launch methods: The aircraft  100  may be hand launched or catapulted with wings deployed, that is such that the aircraft  100  is in the high lift high drag configuration. Alternatively the aircraft can be launched via catapult or compressed air from a tubular vessel with contracted wings, e.g. as it is in the low lift low drag configuration. Alternatively the aircraft  100  can be released by being affixed to a lighter-than-air balloon. Launch control can be autonomous, semi-autonomous or manual. 
     2—Air launch. Applicable for launch from altitude via various platforms such as manned aircraft, unmanned air vehicles (UAVs), high altitude long endurance (HALE) vehicles, and release from balloon. 
     3—Direct interceptions with no or minimal use of loitering and extended wing mode (e.g. minimal use of the first configuration). Interceptions may conclude in sacrificial impact or effecting the target during close flypast with a ranged effector payloads, or single use capture systems like net or entanglement payloads. 
     4—Launch to loitering operation (remaining at altitude with extended wing mode (high lift high drag configuration)) before interception target selection or return to collection point. 
     5—Flypast operation with a ranged effector payload, such as Electronic Countermeasures, then return to collection point. Method suitable for sequentially engaging multiple targets such as swarms of micro air vehicles (MAVs). 
     6—Ground target precision impact/flypast. Wing Modality switching enables erratic or extreme approach vector and velocity change. Examples include targeted delivery of vehicle mobility disruption payloads, or controlled delivery of items to personnel in remote, urban or forested locations. 
       FIG. 5  gives cutaway side and top views of an example aircraft  200 . The aircraft  200  comprises a body  112 , having a nose  18  and tail  16 , as well as wings  114  arranged substantially as described above with reference to  FIGS. 2 and 3 . The aircraft further comprises two compartments  216   a,    216   b,  which comprise a cavity into which for example a payload can be placed for delivery to a target site. The first compartment  216   a  is arranged proximal to an upper surface of the body between the two wings. The second compartment  216   b  is arranged proximal to an under surface of the body between the two wings. In the example shown the second compartment  216   a  comprises a compartment for a net  217 , for example in which a net can be stored and deployed from, and then subsequently retracted to capture an object from a target site. Both compartments  216  are symmetric about the central axis of the aircraft and extend for substantially the length of the wings along the upper and lower surface of the body  112  respectively. 
     The aircraft further comprises a flight controller  218  arranged substantially at the centre of the aircraft, for example between the wings and below the first compartment  216   a.  The controller  218  is electrically connected to, and powered by, a battery  220  arranged forward along the central axis of the aircraft  200  from the controller  218 . The controller is further electrically connected to a pair of actuators  222   a,b,  one for each wing  114 , and to a pair of ducted fans  224   a,b.  Each actuator  222   a,b  is connected to a wing mechanism  226 , for example an extension frame, and the controller is configured to control operation of the actuators  222   a,b  to move the respective wing  114 , for example as described above with reference to  FIGS. 2 and 3 . 
     The pair of ducted fans  224   a,b  are each arranged in a respective pair of additional channels  228   a,b  that extend from a front surface of the aircraft, for example the front of the curved under-surface of the aircraft below the nose  18 , to a rear surface of the aircraft, for example the front of the curved under surface of the aircraft below the tail  16 . The pair of channels  228   a,b  are parallel to one another and each extend through the body  112  below the first compartment  216   a,  controller  218  and battery  220 , and above the second compartment  216   b.  The fans  224   a,b  are configured to generate a flow through the channels  228   a,b,  and thereby to generate thrust for the aircraft  200 . The controller  218  is configured to control operation of the fans  224   a,b,  e.g. their speed of rotation, to control the thrust force that they generate. 
     The aircraft further comprises a camera  225  arranged in the nose  18  of the aircraft  200 , for viewing the external environment in front of the aircraft  200 . The camera  225  may be connected to transmitter means (not shown) for transmitting the images it captures to an operator on the ground and/or storage means for storing the image data it obtains. In some examples the camera is further electrically connected to the controller  218 , for example such that the controller may control operation of the camera and/or obtain image data therefrom. 
       FIG. 6  illustrates front and plan views of an aircraft  300 , substantially as described above, and in particular shows the wings  114  of the aircraft  300  at successive stages of the transition between the high lift high drag configuration, and the low lift low drag configuration. The aircraft  300  has a structure substantially as described above with reference to  FIG. 5 , and comprises a pair of channels  228   a,b  within the body and a pair of ducted fans  224   a,b  arranged within the channels  228   a,b,  as described therein. When the aircraft is in the high lift high drag configuration, each wing is fully extended, and the outer edge of the wing ‘kicks’ outwards, e.g. as described above, such that the width of the wing is greater at its back edge than at its front edge, as shown at  601 . Upon operation of the actuator to exert an inwards force on the wings, as shown at  602 , the entire outer edge of the wing is retracted and brought closer to the body, and concurrently the outer edge is rotated in the plane of the wing, towards the body—i.e. so as to reduce the angle between the outer edge of the wing and the body. This retraction is continued until the wing is fully retracted in the plane into the intermediate position, as shown at position  603 . Upon further operation of the actuator, the outer edge of the wing is rotated downwards out of the plane, for example about a hinge, and into a low lift low drag configuration, as shown at  604 , in which a channel is formed between the wing and the body as described above. The wing may be rotated still further towards the body, into a closed configuration, as shown at  605 , in which the wing is positioned tight against the body such that the channels between the wing and the body are substantially closed. It will of course be understood that upon reverse operation of the actuator the wing is also configured to transition between the positions described above in the opposite direction, that is, from the closed configuration  605  into the high lift high drag configuration  601 . 
       FIG. 7  illustrates the air flow around the aircraft  300  when it is in flight in the low lift low drag configuration (as at  604  in  FIG. 6 ). As shown, the wings  114  are shaped so as to direct air around the outside of the wing  114  and also into channels  330  that are formed between the outer edge of the wings  114  and the body of the aircraft. The leading edges  331  of the wings are swept forward, that is, the outermost point of the front edge of each wing is further forward than the point at which it connects to the body, so as to direct air into the channels  330 . In flight, air is also sucked through the inner channels  228  that are provided within the body of the aircraft, in which the ducted fans  224  are positioned, thereby generating thrust for the aircraft. 
       FIGS. 8A and 8B  both show an extendable wing support frame for a wing of an aircraft, each having a structure different to that the support frame  122  described above with reference to  FIG. 2 .  FIG. 8A  illustrates a support frame  80  comprising a plurality of longitudinal beams  82  arranged parallel to one another, wherein each longitudinal beam is connected to adjacent beams by a pair of connecting beams  84 . More specifically, each connecting beam  84  extends from the front end of one longitudinal beam  82  to a point along the length of an adjacent longitudinal beam  82 , such that adjacent longitudinal beams  82  are connected together by two connecting beams  84  that cross one another. The connecting beams  84  are pivotably connected to their respective longitudinal beams  84  such that the longitudinal beams  82  may be brought together and moved apart so as to extend and contract the frame  80  in the plane of the frame  80  in the direction perpendicular to the orientation of the longitudinal beams  82 . In  FIG. 8A  the connecting beams  84  are all of equal length such that upon extension of the frame the longitudinal beams  82  remain parallel to one another and there is no rotation of the outer edge of the frame  80 . 
       FIG. 8B  shows another extendable frame  80 ′ comprising a plurality of longitudinal beams  82  arranged parallel to one another and connected together with connecting beams  84   a,    84   b  substantially as described above with reference to  FIG. 8A . However, in this example the connecting beams  84   a,    84   b  are not of equal length. Instead each pair of connecting beams that connects adjacent longitudinal beams  82  comprises a first connecting beam  84   a,  that connects the front end of the respective outer longitudinal beam  82 ′ to a point along the length of the respective inner longitudinal beam, which is shorter than the other connecting beam  84   b  in the pair. As such, as the frame  80 ′ is extended it splays such that the longitudinal beams  82  rotate relative to one another in the plane of the frame  80 ′, as shown, with the degree of relative rotation between the beams  82 ′ increasing with distance between them. In this way the outer edge of the wing is rotated in the plane of the wing as the frame  80 ′ expands and contracts. 
     Alternative aircraft structures and methods of operation are also envisaged. 
     Although the aircraft  100  was described as having a single hinge connecting the body to an extendable frame of the wing, in other examples a hinge may be provided on the wing itself. For example a hinge may be provided between two parts of the wing such that they can pivot relative to one another. An actuator may also be provided on the wing such that the shape of the wing can be varied by pivoting one part of the wing relative to the other. The actuator may be connected between each part of the wing, for example it may be connected to at least one extendable frame. Such a hinge and/or actuator may be used in addition to or as an alternative to the hinge and actuator described above. 
     In some examples the support frame and the extension frame may be combined, for example the wing cover may be mounted directly onto an expandable frame and there is no need for an additional support frame. 
     In some examples the aircraft may not comprise an extendable frame. Instead the wing may simply pivot from a first configuration in which the wing is in a first plane, into another configuration in which the outer edge of the wing is rotated downwards out of the plane towards an undersurface of the body, without there being any extension or retraction of the wing in the plane. 
     Although the hinges have been described herein as simple 90 degree hinges, in other examples the connection between the wing and the body may be provided by a ‘ball and socket’ type joint. For example, a ball-type connecting element may be provided on the wing that can rotate within a socket of the body. In some examples the wing may be biased into a particular configuration. Additional, flexible, ‘tendon’-like connecting elements may be provided to connect the wing to the body in such examples. Such tendons may be extendable and may bias the wing into a particular configuration, e.g. one of the configurations described above. For example, the tendons may act to bias the wings into the low lift, low drag configuration, and the actuator may be configured to apply a force against the bias of the tendons to transition the wing into the high lift, high drag configuration (or vice versa). 
     In some examples the connection between the wing and the body may be bistable. For example the wing may be biased into one configuration, such as the low-lift low-drag configuration, and upon extension of the actuator beyond a certain point—the wing may be biased into another configuration, such as the high-lift high-drag configuration. 
     In other examples the outer edge of the wing may be configured to rotate towards the body further than described above, that is, further than the low lift low drag ‘cupped’ configuration, so as to be ‘tucked’ under the body of the aircraft. This may be provided via a hinge that allows greater than 90 degree rotation, or by a static or moveable curving element of a frame of the wing or the wing cover. Such a configuration may provide lower drag still than the third configuration described herein, and may provide a reduced effective volume of the aircraft, which may enable the aircraft to fit into a tube for a tubular vessel launch as described above. 
     In some examples the wing may be attachable and detachable from the body. For example complimentary mating elements may be provided on the inner edge of the wing and the body respectively in order to couple and decouple them. 
     Although the aircraft has been described has been described as comprising a fan or propeller, in other examples different means of propulsion may be provided, for example a jet. 
     Furthermore, although the ducted fans and propellers have been described above as being positioned in channels within the aircraft, in other example they may be positioned at other locations about the aircraft. For example, the fans may be arranged externally to the body, for example two fans may be provided with one positioned either side of the body, e.g. each attached to a side face of the body. In some examples the fans may be positioned in the channels formed between the wing and the body, such as the channels provided by the aircraft of  FIG. 1  or those provided by the aircraft in the cupped low lift low drag configuration shown in  FIG. 3C , and at position  604  in  FIG. 6 . Positioning the fans external of the body in this way may offer easier access for maintenance, replacement and product assembly. Such an arrangement may also provide a greater internal volume of the body, in comparison to the examples described above, for example so as to provide more space for payloads. 
     In the methods described above, the wing transforms from the high lift high drag configuration into the low lift low drag configuration by first retracting and rotating inwards towards the body in the plane, and subsequently rotating downwards out of the plane (for example about the hinge)—e.g. rotation about the hinge is inhibited until the wing is in a fully retracted state. However, in other examples hinge rotation may be concurrent to in-plane extension and retraction of the extension frame. For example a compliant or flexible attachment may be provided between the actuator and the extension frame such that some out of plane downward rotation about the hinge is provided before the extension frame is fully retracted. Similarly, in such examples, when transitioning the wing from the low lift low drag configuration to the high lift high drag configuration, some in-plane extension may be provided before the wing is fully rotated upwards into the intermediate configuration. 
     Although the above examples have been described in relation to an aircraft, alternative types of vehicles are envisaged. For example, in some embodiments the vehicle may be a submarine or submersible vehicle, rather than an aircraft. Such examples may be employed without departing from the scope of the invention, which is defined in the accompanying claims. 
     In certain examples a controller described herein may be configured to perform any of the methods, or particular steps of said methods. The activities and apparatus outlined herein may be implemented using controllers and/or processors which may be provided by fixed logic such as assemblies of logic gates or programmable logic such as software and/or computer program instructions executed by a processor. Other kinds of programmable logic include programmable processors, programmable digital logic (e.g., a field programmable gate array (FPGA), an erasable programmable read only memory (EPROM), an electrically erasable programmable read only memory (EEPROM)), an application specific integrated circuit, ASIC, or any other kind of digital logic, software, code, electronic instructions, flash memory, optical disks, CD-ROMs, DVD ROMs, magnetic or optical cards, other types of machine-readable mediums suitable for storing electronic instructions, or any suitable combination thereof. 
     The above embodiments are to be understood as illustrative examples. Further embodiments are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims. 
     Other variations and modifications of the apparatus will be apparent to persons of skill in the art in the context of the present disclosure.