Aerodynamic and radar reflection reduction structure for a payload having a protruding lug well, and a method for designing the same

Abstract

The objective of the present invention, which is to solve the aforementioned conventional problems, is to provide a payload with an aerodynamic and radar reflection reduction structure for a protruding lug well and a design method thereof, which has a structure such that the rate of change in cross-sectional area is formed smoothly while maintaining the continuity of the external shape, in order to minimize the degradation of aerodynamic performance caused by a lug well protruding from the outer surface of the payload body. To achieve the above objective, the payload of the aerodynamic and radar reflection reduction structure for a protruding lug well according to the present invention comprises, in a payload externally mounted on an aircraft, a fuselage skin forming the outer surface of the fuselage skin, a lug well protruding from the outer surface of the fuselage skin and including a fastening portion inside, a lug formed in the lug well for coupling with the aircraft, and a fairing structure formed on the outer circumference of the fuselage skin to surround the lug well, wherein the fairing structure is formed within a range that does not exceed the maximum protrusion height of the lug well, and the lug is configured to remain exposed to the outside.

Description

Technology Field

[0001] The present invention relates to a payload with an aerodynamic and radar reflection reduction structure for a protruding lug well and a design method thereof, and more specifically, to a payload with an aerodynamic and radar reflection reduction structure for a protruding lug well and a design method thereof that suppresses aerodynamic performance degradation and reduces radar reflection through a fairing structure that surrounds the protruding lug well. Background Technology

[0002] Payloads externally mounted on an aircraft generally include a lug structure for coupling with an aircraft or guided missile, and these lugs are formed to have a specific thickness and shape to ensure mechanical strength for fastening. In particular, the lugs have a structure that protrudes a certain portion from the outer surface of the fuselage to perform external mounting and detachment functions, and often a lug well or threaded fastening section is formed in conjunction with this for insertion or fastening of the lugs. While this structure is advantageous for ensuring mechanical coupling reliability, it acts as a factor that impedes the continuity of the aircraft's external shape.

[0003] In conventional technology, various attempts have been made to minimize the degradation of aerodynamic performance caused by such protruding structures. For example, methods have been applied to insert the protruding structure into the fuselage as much as possible or to limit the size or shape of the lugs to reduce external protrusion. Additionally, some technologies have attempted approaches to form a smoother exterior by installing simple covers around the protruding structure. However, such simple cover structures often involve abrupt changes in shape or fail to sufficiently ensure curvature continuity with the fuselage's exterior, which can lead to problems such as flow separation or turbulence during high-speed flight.

[0004] In particular, under supersonic or high-speed flight conditions, the rate of change in the cross-sectional area of ​​the fuselage shape significantly affects aerodynamic performance. Protruding lug well structures form regions where the cross-sectional area increases rapidly locally, becoming a major cause of increased wave drag. This increase in local cross-sectional area can induce shock wave formation and boundary layer instability, which consequently not only reduces flight efficiency but also causes problems by increasing the aerodynamic loads acting on the structure. Furthermore, such protruding structures can affect flight stability as well as simply increasing drag, and there is a possibility that they may induce abnormal flow patterns under certain conditions.

[0005] Meanwhile, in military aircraft or systems requiring stealth performance, radar reflection characteristics are also considered a very important factor. However, conventional lug well structures often form right-angled corners or closed-surface internal structures, acting similarly to corner reflectors that generate strong reflected signals when radar waves are incident. This leads to an increase in the radar cross-section (RCS), which acts as a factor that increases the detectability of the aircraft. In particular, if the shape of the protruding structure is asymmetric or undergoes abrupt changes in shape, the scattering characteristics of radar waves appear non-uniform, and there is a problem of strong reflection occurring in specific directions.

[0006] Furthermore, in conventional technology, designs that simultaneously consider aerodynamic performance and radar reflection characteristics have often not been sufficiently implemented. Some technologies have applied streamlined covers to focus on improving aerodynamic performance, but such covers may not provide sufficient effectiveness in reducing radar reflection or may instead result in concentrating reflection at specific angles. Conversely, applying an angular structure to reduce radar reflection may lead to a decrease in aerodynamic performance. In other words, aerodynamic performance and stealth performance often act as conflicting design elements, and structural design that satisfies both simultaneously has remained an unresolved challenge in conventional technology.

[0007] Furthermore, structures that form lug wells or fasteners within the fuselage present problems in terms of internal space utilization. In particular, where space for propellant storage is required, the presence of internal fastener structures can lead to reduced propellant fill density or uneven internal flow. Additionally, internal structures can cause stress concentration or uneven heat distribution, potentially resulting in reduced structural stability and reliability. For these reasons, there has been a continuous demand for structures that can maintain external coupling capabilities while maximizing internal space continuity.

[0008] As such, conventional external mounting structures for aircraft utilize lug and lug well designs to ensure mechanical coupling reliability, thereby simultaneously incorporating various problems such as reduced aerodynamic performance, increased radar reflection, and hindered internal space utilization. Furthermore, while attempts have been made to address these issues individually, an integrated design solution capable of maintaining internal spatial continuity while simultaneously considering aerodynamic performance and radar reflection characteristics has not yet been sufficiently presented.

[0009] Therefore, measures are needed to address the aforementioned problems. Prior art literature

[0010] Korean Patent Publication No. 10-2866621 (Published July 5, 2022) The problem to be solved

[0011] The objective of the present invention, which is to solve the aforementioned conventional problems, is to provide a payload with an aerodynamic and radar reflection reduction structure for a protruding lug well and a design method thereof, which has a structure such that the rate of change in cross-sectional area is formed smoothly while maintaining the continuity of the external shape, in order to minimize the degradation of aerodynamic performance caused by a lug well protruding from the outer surface of the payload body.

[0012] In addition, the objective of the present invention is to provide a payload of an aerodynamic and radar reflection reduction structure for a protruding lug well having a shape structure capable of dispersing the reflection direction of radar waves and suppressing corner reflections in order to reduce radar reflection signals generated around the protruding lug well, and a method for designing the same.

[0013] And, the objective of the present invention is to provide a payload with an aerodynamic and radar reflection reduction structure for a protruding lug well and a design method thereof, which simultaneously satisfies structural functionality and aerodynamic and stealth performance through external shape optimization so as to maintain a lug structure for external mounting without infringing upon the internal propellant storage space. means of solving the problem

[0014] To achieve the above objective, the payload of the aerodynamic and radar reflection reduction structure for a protruding lug well according to the present invention comprises, in a payload externally mounted on an aircraft, a fuselage skin forming the outer surface of the fuselage skin, a lug well protruding from the outer surface of the fuselage skin and including a fastening portion inside, a lug formed in the lug well for coupling with the aircraft, and a fairing structure formed on the outer circumference of the fuselage skin to surround the lug well, wherein the fairing structure is formed within a range that does not exceed the maximum protrusion height of the lug well, and the lug is configured to remain exposed to the outside.

[0015] In addition, in the payload of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention, the fairing structure is formed such that its curvature continuously matches the outer surface of the fuselage skin, thereby being configured so that no radial step difference occurs in the outer shape.

[0016] In addition, in the payload of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention, the lug is exposed to the outside from the lug well, and is characterized in that an opening is formed in the fairing structure to perform a coupling function without interference with the outer surface of the fairing structure.

[0017] In addition, in the payload of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention, the fairing structure is formed such that the rate of change (dA / dx) of the cross-sectional area (A) according to the axial position (x) of the fuselage changes continuously in order to mitigate the increase in the local cross-sectional area caused by the lug well, and is designed such that the square integral of the rate of change of the cross-sectional area is minimized.

[0018] In addition, to achieve the above objective, the payload of the aerodynamic and radar reflection reduction structure for another protruding lug well according to the present invention is a payload externally mounted on an aircraft, comprising a fuselage skin, a lug well protruding from the outer surface of the fuselage skin, a lug formed in the lug well, and a fairing structure surrounding the lug well, wherein the fairing structure is formed such that its shape gradually changes from the front to the rear with respect to the flight direction, the front region is formed to gradually rise from the outer shape of the fuselage skin to match the maximum height of the lug well, and the rear region is formed in a tapered shape that gradually decreases from the maximum height, so as to minimize the rate of change in the cross-sectional area of ​​the fuselage skin.

[0019] In addition, in the payload of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention, the front region of the fairing structure is characterized by being formed as a curved surface in which the curvature gradually increases at the connection portion with the outer shape of the fuselage.

[0020] In addition, in the payload of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention, the rear region of the fairing structure is formed in a tapered shape that gradually decreases to maintain continuity with the outer shape of the fuselage.

[0021] In addition, in the payload of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention, the fairing structure is characterized by being designed so that the wave drag generated during flight is minimized according to the following Equation 1.

[0022] <Formula 1>

[0023]

[0024] (Here, D wave : Wave drag, A : Cross-sectional area, x : Position along the fuselage axis)

[0025] In addition, to achieve the above objective, a payload of an aerodynamic and radar reflection reduction structure for another protruding lug well according to the present invention comprises, in a payload externally mounted on an aircraft, a fuselage skin, a lug well protruding from the outer surface of the fuselage skin, a lug formed in the lug well, and a fairing structure surrounding the lug well, wherein the cross-section of the fairing structure is formed as an elongated ellipse or an asymmetrical ellipse, and the outer surface of the fairing structure is formed as a curved surface with a continuously changing curvature, so as not to cause right-angle corners or abrupt changes in shape.

[0026] In addition, in the payload of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention, the fairing structure is characterized by being formed continuously in the circumferential direction along the outer circumference of the lug well and configured so that the outer shape is integrated without local shape discontinuity.

[0027] In addition, in the payload of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention, the fairing structure is formed to have different curvature distributions at the front and rear corresponding to the protrusion direction of the lug well, so as to be configured to separate the acceleration and deceleration sections of the flow.

[0028] In addition, in the payload of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention, the fairing structure is designed such that its outer curvature is continuously adjusted in response to changes in the thickness of the boundary layer formed along the fuselage surface in order to minimize flow disturbances caused by the lug well, and is configured such that the occurrence of flow separation is suppressed.

[0029] In addition, to achieve the above objective, a payload of an aerodynamic and radar reflection reduction structure for another protruding lug well according to the present invention is a payload externally mounted on an aircraft, comprising a fuselage skin, a lug well protruding from the outer surface of the fuselage skin, a lug formed in the lug well, and a fairing structure surrounding the lug well, wherein the side of the fairing structure is formed to include a surface inclined at a predetermined angle with respect to the fuselage centerline so as to be configured to reflect radar waves incident from the outside in an off-axis direction and to suppress the corner reflector effect.

[0030] In addition, in the payload of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention, the side of the fairing structure is characterized by being formed in a flat or curved shape.

[0031] In addition, in the payload of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention, the fairing structure is characterized by including a curved surface structure with the corner shape removed.

[0032] In addition, in the payload of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention, the side of the fairing structure is characterized by including a surface inclined at a predetermined angle with respect to the centerline of the fuselage, so that incident radar waves are not concentrated in a specific direction upon reflection but are dispersed in an off-axis direction.

[0033] And, to achieve the above objective, the method for designing an aerodynamic and radar reflection reduction structure for a protruding lug well according to the present invention comprises, in a method for designing an aerodynamic and radar reflection reduction structure for a payload externally mounted on an aircraft, a step of defining the shape of a lug well protruding from the outer surface of the fuselage skin and a lug formed in said lug well; a step of forming a fairing structure that surrounds said lug well, wherein the front region of said fairing structure is formed to gradually rise from the outer shape of the fuselage and the rear region is formed in a tapered shape that gradually decreases; a step of setting the cross-sectional shape of said fairing structure to an elliptical or asymmetrical elliptical shape and forming the curvature of the outer surface to change continuously; and a step of tilting the side of said fairing structure so that the reflection direction of radar waves is dispersed in an off-axis direction, and is characterized in that the rate of change of the cross-sectional area of ​​the outer shape of the fuselage is minimized by said fairing structure.

[0034] In addition, in the payload of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention, the step of forming the fairing structure is characterized in that the outer surface of the fairing structure is formed such that the curvature is continuous with the outer surface of the fuselage skin.

[0035] In addition, in the payload of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention, the step of setting the cross-sectional shape of the fairing structure is characterized by setting the cross-sectional shape such that the cross-sectional area distribution according to the axial position of the fuselage changes continuously.

[0036] In addition, in the payload of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention, when designed so that the rate of change in the cross-sectional area of ​​the fuselage shape is minimized by the fairing structure, the shape is repeatedly corrected based on the results of fluid analysis or numerical analysis so that the square integral of the rate of change in the cross-sectional area of ​​the fuselage shape formed by the fairing structure is minimized.

[0037] Specific details of other embodiments are included in "Specific details for implementing the invention" and the attached "drawings".

[0038] The advantages and / or features of the present invention and the methods for achieving them will become clear by referring to the various embodiments described below in detail together with the accompanying drawings.

[0039] However, it should be understood that the present invention is not limited to the configurations of each embodiment disclosed below, but may be implemented in various different forms, and that each embodiment disclosed in this specification is provided merely to make the disclosure of the present invention complete and to fully inform those skilled in the art of the scope of the present invention, and that the present invention is defined only by the scope of each claim of the claims. Effects of the invention

[0040] The present invention can achieve the following effects through the combination and usage relationships of the embodiments of the present invention described above and the configuration described below.

[0041] According to the present invention, by ensuring continuity of the external shape through a fairing structure that surrounds a lug well protruding from the outer surface of the fuselage of a payload, the increase in wave drag caused by abrupt changes in cross-sectional area is suppressed and overall aerodynamic performance is improved.

[0042] In addition, according to the present invention, by dispersing the reflection of radar waves in an off-axis direction and suppressing the corner reflection effect through the continuous curvature shape and inclined surface configuration of the fairing structure, the radar reflection cross-section (RCS) is reduced, thereby improving stealth performance.

[0043] Furthermore, according to the present invention, the lug well is shaped externally so as not to infringe upon the internal propellant storage space, while simultaneously satisfying structural coupling functions and aerodynamic performance through an external fairing structure, thereby having the effect of improving internal space utilization efficiency and propellant stability. Brief explanation of the drawing

[0044] FIG. 1 is a cross-sectional view showing a payload of an aerodynamic and radar reflection reduction structure according to one embodiment of the present invention. FIG. 2 is a perspective view showing an example of the payload of FIG. 1. Figure 3 is a diagram showing the pairing structure of Figure 2 in more detail. Figure 4 is a conceptual diagram showing the interior of the payload of Figure 1. FIG. 5 is a flowchart of a design method for an aerodynamic and radar reflection reduction structure according to one embodiment of the present invention. And, FIG. 6 is a configuration diagram showing a combined system of aerodynamic and radar reflection reduction structures according to one embodiment of the present invention. This is a perspective view showing an example of a mount having a double circumferential welded joint structure based on an annular section according to another embodiment of the present invention. Specific details for implementing the invention

[0045] Before describing the present invention in detail, it should be understood that the terms and words used in this specification should not be interpreted as being limited to their ordinary or dictionary meanings, and that the inventor of the present invention may appropriately define and use the concepts of various terms to best describe their invention, and furthermore, that these terms and words should be interpreted in a meaning and concept consistent with the technical spirit of the present invention.

[0046] In other words, it should be understood that the terms used in this specification are used merely to describe preferred embodiments of the present invention and are not intended to specifically limit the content of the present invention, and that these terms are defined in consideration of various possibilities of the present invention.

[0047] In addition, it should be noted that in this specification, singular expressions may include plural expressions unless the context clearly indicates a different meaning, and that even if they are expressed in a similarly plural form, they may include a singular meaning.

[0048] Throughout this specification, where it is stated that a component "includes" another component, unless specifically stated otherwise, this may mean that it does not exclude any other component but may include any other component.

[0049] Furthermore, it should be noted that where it is stated that a component "exists inside or is installed in connection with" another component, this component may be installed in direct connection or contact with the other component, or it may be installed at a certain distance apart; in the case where it is installed at a certain distance apart, a third component or means for fixing or connecting the component to the other component may exist, and a description of this third component or means may be omitted.

[0050] On the other hand, where it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that a third component or means does not exist.

[0051] Likewise, other expressions describing the relationship between each component, such as “between” and “right between”, or “adjacent to” and “directly adjacent to”, should be interpreted as having the same intent.

[0052] In addition, it should be understood that in this specification, terms such as "one side," "other side," "one side," "other side," "first," and "second," if used, are intended to clearly distinguish one component from another component, and that the meaning of the component is not restricted by such terms.

[0053] In addition, position-related terms such as "up," "down," "left," and "right" used in this specification should be understood as indicating the relative position of the corresponding component in the drawing, and unless an absolute position is specified, these position-related terms should not be understood as referring to an absolute position.

[0054] Furthermore, in specifying the reference numerals for each component of each drawing in this specification, the same component has the same reference numeral even if it is shown in different drawings; that is, the same reference numeral throughout the specification indicates the same component.

[0055] In the drawings attached to this specification, the size, position, connection relationships, etc., of each component constituting the present invention may be described in a partially exaggerated, reduced, or omitted manner for the convenience of explanation or to sufficiently clearly convey the concept of the present invention, and therefore, the proportions or scale may not be strictly accurate.

[0056] In addition, in describing the present invention below, detailed descriptions of components, such as prior art and known technologies, that are deemed to unnecessarily obscure the essence of the invention may be omitted.

[0058] Preferred embodiments of the present invention will be described in detail below with reference to the drawings.

[0059] FIG. 1 is a cross-sectional view showing a payload of an aerodynamic and radar reflection reduction structure according to one embodiment of the present invention.

[0060] As illustrated in FIG. 1, the payload (100) of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention comprises, in a payload externally mounted on an aircraft, a fuselage skin (110) forming the outer surface of the fuselage skin (110), a lug well (120) protruding from the outer surface of the fuselage skin (110) and including a fastening portion inside, a lug (130) formed in the lug well (120) for coupling with the aircraft, and a fairing structure (140) formed on the outer circumference of the fuselage skin (110) to surround the lug well (120), wherein the fairing structure (140) is formed within a range that does not exceed the maximum protrusion height of the lug well (120), and the lug (130) is configured to remain exposed to the outside.

[0061] The outer shell (110) of the fuselage is a structure that forms a space for accommodating propellant or various equipment inside, and can be formed in a cylindrical shape or a tapered shape with a diameter that changes in the axial direction, and can be implemented in a metal material or a composite material to simultaneously secure lightness and structural strength. In addition, the outer shell (110) of the fuselage is formed to maintain the continuity of the internal space and can be configured so that a separate fastening space for accommodating a lug well inside is not formed as in the prior art.

[0062] The lug well (120) is formed as a structure protruding from the outer surface of the fuselage skin (110) and is configured to provide a space for fastening the lug (130). At this time, the lug well (120) is formed in an outward direction without encroaching on the internal space of the fuselage skin (110), thereby maintaining the continuity of the internal propellant storage space. Additionally, the shape of the lug well (120) can be implemented in various forms, such as a cylindrical, polygonal, or curved shape, and a threaded structure or a pin connection structure may be formed inside depending on the fastening method.

[0063] The lug (130) is formed in the lug well (120) to perform mechanical coupling with the aircraft and is formed to be exposed to the outside of the lug well (120). At this time, the lug (130) may be formed as a single structure, or may be composed of multiple parts arranged symmetrically or asymmetrically, and its shape may be varied depending on the mounting interface of the aircraft. In addition, the lug (130) may be formed of a high-strength material and designed to withstand repetitive loads and impact loads.

[0064] The fairing structure (140) is an external shape correction structure formed to surround the lug well (120), and can be formed to maintain external shape continuity with the outer surface of the fuselage skin (110). In particular, the fairing structure (140) can be configured to prevent unnecessary external shape protrusion and minimize the increase in the cross-sectional area of ​​the overall shape by being formed within a range that does not exceed the maximum protrusion height of the lug well (120). Additionally, the fairing structure (140) is formed such that the curvature changes continuously at the connection portion with the fuselage skin (110), thereby suppressing flow separation or the occurrence of turbulence caused by abrupt shape changes.

[0065] Additionally, the fairing structure (140) can be formed such that, in the forward region relative to the flight direction, it gradually rises from the outer shape of the fuselage skin (110) to match the height of the lug well (120), and in the rear region, it can be formed in a tapered shape that gradually decreases. Through this structure, the rate of change of the cross-sectional area of ​​the fuselage is maintained smoothly, and the wave drag generated, particularly during high-speed or supersonic flight, can be effectively reduced.

[0066] Furthermore, the cross-sectional shape of the fairing structure (140) may be formed as an elongated ellipse or an asymmetrical ellipse, and the outer surface may be composed of a curved surface with a continuously changing curvature. This eliminates right-angle corners or abrupt changes in shape, thereby improving not only aerodynamic performance but also radar reflection characteristics. Additionally, the side of the fairing structure (140) may be formed to be inclined at a predetermined angle with respect to the fuselage centerline as needed, so that incident radar waves are dispersed in an off-axis direction rather than being reflected in a specific direction.

[0067] Meanwhile, the fairing structure (140) may be formed as a single member or implemented in a combined form of multiple segmented members, and may be joined to the fuselage skin (110) by welding, bonding, or mechanical fastening. Additionally, the material of the fairing structure (140) may be metal, composite, or radar-absorbing material, and, if necessary, heat resistance, corrosion resistance, and stealth performance may be further enhanced through surface coating.

[0068] In this way, the payload (100) of the present embodiment can maintain the usability of the internal space while simultaneously improving aerodynamic performance and radar reflection reduction performance by optimizing the external shape through the fairing structure (140) while forming the lug well (120) externally, and its shape and configuration can be expanded and changed according to various operating environments and design conditions.

[0069] More specifically, the fairing structure (140) can be designed to maintain curvature continuity by considering the manufacturing process and assembly precision, going beyond simply being geometrically connected to the outer surface of the fuselage skin (110). For example, a correction curved surface to absorb fine tolerances can be additionally formed in the joint section between the fairing structure (140) and the fuselage skin (110), thereby suppressing fine step differences that may occur during assembly. Furthermore, the aforementioned joint section can be designed considering surface roughness and coating thickness, so that the continuity of the exterior shape can be maintained even in actual operating environments. Moreover, the fairing structure (140) may be manufactured as a segmented structure and then joined to the fuselage skin (110), in which case the shape of the joint section can also be optimized so that the continuity of the exterior shape is maintained in the segmented section as well.

[0070] Additionally, the opening formed in the pairing structure (140) may be designed as an extended shape rather than a simple through-hole structure, taking into account the shape and coupling operation of the lug (130). For example, the opening may be formed in an asymmetrical shape depending on the insertion or coupling direction of the lug (130), and a streamlined guide surface may be formed at the edge of the opening to prevent abrupt changes in airflow. Furthermore, a reinforcing rib or a local thickness increase structure may be added to the inner side of the opening to compensate for the structural strength reduced by the opening. Moreover, a polyhedral shape or an inclined surface considering radar reflection characteristics may be formed around the aforementioned opening, thereby suppressing the concentration of reflected signals that may occur in the opening area.

[0071] Meanwhile, the cross-sectional area distribution of the pairing structure (140) may be designed as a non-linear function according to the axial position (x) of the body, rather than a simple linear change. For example, the change in cross-sectional area (A) may be defined in the form of a polynomial function, an exponential function, or a spline function, and may be designed so that the rate of change is maintained gradually in certain sections and gradually adjusted in other sections. In particular, by designing so that there are no sections where the rate of change in cross-sectional area (dA / dx) increases or decreases rapidly, shock wave formation and flow disturbance can be minimized.

[0072] In addition, the design to minimize the square integral of the rate of change of cross-sectional area is not limited to a single flight condition but can be performed using a multi-purpose optimization method by considering various operating conditions. For example, the cross-sectional area distribution for different Mach number, altitude, and attitude conditions can be evaluated, and a fairing structure (140) can be designed with a shape that simultaneously satisfies these conditions. To this end, an optimization algorithm that iteratively adjusts shape parameters based on numerical analysis results can be applied, and an artificial intelligence-based design technique may be utilized as needed.

[0073] Furthermore, the fairing structure (140) may have a shape that changes not only in cross-sectional area but also in the circumferential direction. For example, it may have a non-uniform distribution in which the cross-sectional area relatively increases in the area corresponding to the location of the lug well (120) and decreases in other areas, thereby further improving the aerodynamic performance of the entire structure. Additionally, the fairing structure (140) may be designed with an asymmetric shape to prioritize the improvement of aerodynamic performance or radar reflection characteristics in a specific direction.

[0074] FIG. 2 is a perspective view showing an example of the payload of FIG. 1.

[0075] As illustrated in FIG. 2, the payload (100) of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention is a payload externally mounted on an aircraft, comprising a fuselage skin (110), a lug well (120) protruding from the outer surface of the fuselage skin (110), a lug (130) formed in the lug well (120), and a fairing structure (140) surrounding the lug well (120). The fairing structure (140) is formed such that its shape changes gradually from the front to the rear with respect to the flight direction, the front region is formed to gradually rise from the outer shape of the fuselage skin (110) to match the maximum height of the lug well (120), and the rear region is formed in a tapered shape that gradually decreases from the aforementioned maximum height, so as to minimize the rate of change in the cross-sectional area of ​​the fuselage outer shape.

[0076] Here, the fairing structure (140) may be designed not merely as a cover covering the lug well (120), but to form a continuous streamlined shape extending from the front to the rear with respect to the flight direction. In particular, the aforementioned front region may be formed as a gently curved rising section to naturally connect with the shape of the fuselage skin (110), and this rising section may be configured to gradually increase in height over a certain section to match the maximum protrusion height of the lug well (120). At this time, the length and curvature of this rising section may be adjusted according to flight conditions, and a minimum radius of curvature may be set so as not to cause abrupt changes in shape.

[0077] In addition, the aforementioned fairing structure (140) is a wave drag (D) that occurs during flight. wave It can be designed so that ) is minimized, and to this end, the rate of change of the cross-sectional area (A) according to the axial position (x) of the fuselage can be formed to satisfy the following Equation 1.

[0078] <Formula 1>

[0079]

[0080] (Here, Dwave: wave drag, A: cross-sectional area, x: fuselage axial position)

[0081] More specifically, the fairing structure (140) is formed to distribute the increase in local cross-sectional area caused by the lug well (120) forward and backward, and can be designed to have a continuous function form so that the rate of change of cross-sectional area (dA / dx) does not change abruptly. In particular, by setting the shape so that the square integral of the rate of change of cross-sectional area is minimized, the increase in wave drag can be suppressed under various flight conditions, not limited to a specific flight speed.

[0082] In addition, the above design can be applied not only to a single lug well (120) but also to cases where multiple lug wells (120) exist as in FIG. 2, and the axial spacing and pairing shape can be integratedly optimized so that the increase in cross-sectional area caused by each lug well (120) does not interfere with each other.

[0083] Additionally, the central region of the fairing structure (140) is formed along the outer shape of the lug well (120), and may include an opening or cutout to account for the external exposure of the lug (130). In this case, such an opening may be formed to have a curved contour that extends gently forward and backward, rather than a simple rectangular shape, thereby suppressing flow separation and turbulence around the opening. Additionally, the edges of the opening may be rounded or have inclined surfaces formed to minimize aerodynamic resistance and prevent the concentration of radar reflection signals.

[0084] Meanwhile, the rear region described above is formed in a tapered shape that gradually decreases from the maximum height of the lug well (120), and this tapered section can be continuously connected to the forward rising section to form a smooth S-curve shape overall. This shape contributes to controlling the rate of change of cross-sectional area (dA / dx) so that it does not change abruptly, and has the effect of mitigating the intensity of shock waves, especially during high-speed flight. In addition, the length and angle of inclination of the rear taper can be adjusted according to the operating Mach number range of the aircraft, and can be implemented as a multi-stage taper structure if necessary.

[0085] Additionally, the fairing structure (140) may be formed continuously along the circumferential direction of the fuselage skin (110), or it may be formed locally only in the section where the lug wells (120) are formed, as shown in FIG. 2. For example, when a plurality of lug wells (120) are spaced apart in the axial direction, the fairing structure (140) corresponding to each lug well may be formed independently, or it may be extended into a structure that wraps adjacent lug wells with a single integrated fairing. Such an integrated structure is advantageous for further enhancing the continuity of the overall shape and further improving aerodynamic performance.

[0086] Furthermore, the outer surface of the fairing structure (140) is not limited to a simple axially symmetric shape and can be designed with an asymmetric shape as needed. For example, the curvature of one side can be set differently to reduce radar reflection in a specific direction, or an asymmetric shape can be applied according to the flow direction. In addition, the fairing structure (140) can be formed from a composite material with a radar-absorbing material or have a special coating applied to the surface to further enhance stealth performance.

[0087] Additionally, a hollow structure or a lattice structure for weight reduction may be formed inside the fairing structure (140), and internal reinforcing ribs may be added to ensure durability against external shocks or vibrations. Such internal structures may be designed to maintain structural rigidity without affecting the aerodynamic shape.

[0088] Specifically, the forward region of the fairing structure (140) can be designed to go beyond a simple curved rising section and consider the acceleration characteristics of the flow in the connection section with the fuselage outer shape. For example, the forward region can be formed to have a curvature distribution with a pressure gradient that changes gently to suppress an increase in the thickness of the boundary layer separated from the fuselage skin (110), thereby maintaining a stable flow without flow separation in low, subsonic, and transonic regions. Additionally, the curvature change of the forward region can be composed of multiple curvature sections rather than a single curvature, and can be designed so that there is a gentle increase in curvature in the initial section, a relatively large change in curvature in the intermediate section, and a gentle change in curvature again in the section adjacent to the lug well (120).

[0089] Meanwhile, the rear region of the fairing structure (140) is not limited to a simple linear tapered shape, but can be implemented as a non-linear tapered structure that takes into account flow reattachment and pressure recovery. For example, the rear region can be designed with a shape based on a logarithmic or polynomial function to minimize the generation of vortices in the wake region. In addition, the aforementioned rear tapered section may be formed as a structure in which the cross-sectional area is gradually reduced by dividing it into multiple segments rather than a single inclined surface, thereby minimizing aerodynamic loss under various flight conditions. Such a structure can contribute to improving wake flow stability, particularly in the subsonic and transonic regions.

[0090] In addition, the front and rear regions of the fairing structure (140) are not designed independently of each other, but can be integratedly optimized so that the total cross-sectional area distribution has a continuous functional form. At this time, the rate of change (dA / dx) of the cross-sectional area (A) is controlled so that it does not increase or decrease rapidly in a specific range, and can be designed in a multi-conditional optimization manner so that aerodynamic performance is not degraded for various flight speed conditions (subsonic, transonic, supersonic). In particular, the design that minimizes the square integral of this rate of change of cross-sectional area is not limited to a specific speed range, but can be applied to maintain aerodynamic efficiency over a wide range of Mach numbers.

[0091] Furthermore, the fairing structure (140) can be shaped not only by cross-sectional area distribution but also in the direction of the fuselage circumference. For example, an asymmetric distribution can be applied that allows for a relatively large increase in cross-sectional area in the upper region where the lug well (120) is located, while minimizing the increase in cross-sectional area in the side or lower region. This allows for the simultaneous satisfaction of overall aerodynamic performance and structural requirements.

[0092] In addition, the shape of the aforementioned fairing structure (140) can be corrected by reflecting wind tunnel test data or actual measurement data as well as computational fluid dynamics (CFD) analysis during the design process, and an artificial intelligence-based shape optimization technique may be applied as needed. This design method can be utilized to predict performance in various flight environments in advance and to derive an optimal shape through iterative shape correction.

[0093] Additionally, in one embodiment, the lugs (130) may be formed as two, in which case the lugs (130) may be arranged to be spaced apart from each other in the axial direction along the outer surface of the fuselage skin (110). In particular, the two lugs (130) may be arranged symmetrically or asymmetrically with respect to the fuselage centerline, and their position and spacing may be adjusted according to the coupling interface conditions with the aircraft.

[0094] At this time, a lug well (120) may be formed corresponding to each lug (130), and the pairing structure (140) may be formed as a plurality of structures that individually wrap each lug well (120), or as a single structure that wraps adjacent lug wells (120) in one integrated outer shape. For example, as shown in FIG. 2, when there are two lugs (130), the pairing structure (140) may be formed as independent streamlined protrusions centered on each lug well (120), or it may be formed as a continuous single pairing structure including the section between the two lug wells (120).

[0095] Additionally, when two lugs (130) are arranged at a certain distance apart in the axial direction, the pairing structure (140) can be designed to form an independent front rising portion and a rear tapered portion for each lug well (120), respectively, so that the change in cross-sectional area occurring at each lug position can be individually mitigated. On the other hand, when the distance between the lugs is relatively short, the increase in cross-sectional area formed by the two lug wells (120) can be integrated into a single smooth curved surface so that the overall rate of change in cross-sectional area is maintained more smoothly.

[0096] Furthermore, when the lugs (130) are composed of two, the fairing structure (140) may have an asymmetric shape in the circumferential direction as well. For example, when the lugs (130) are placed in the upper region, the fairing thickness and curvature of the upper region are formed relatively large, and the lower region is maintained in a shape similar to the outer shape of the fuselage, thereby optimizing the overall cross-sectional area distribution. In addition, since this structure can affect not only aerodynamic performance but also radar reflection characteristics, the shape of the fairing structure (140) can be adjusted according to the placement direction and number of the lugs (130).

[0097] Additionally, when the lugs (130) are composed of multiple lugs, the local thickness or internal reinforcement structure of the fairing structure (140) can be designed differently by considering the load distribution and coupling conditions acting on each lug (130). For example, if the load acting on the front lug and the rear lug is different, structural stability can be ensured by adding reinforcing ribs or increasing the thickness of the fairing structure (140) at the corresponding location.

[0098] In this way, in an embodiment in which two lugs (130) are formed as shown in FIG. 2, the pairing structure (140) can be designed to be expandable in various ways depending on the number of lugs, the spacing between them, and the load conditions, and thereby can be implemented to simultaneously satisfy aerodynamic performance, structural stability, and radar reflection reduction performance.

[0099] Figure 3 is a diagram showing the pairing structure of Figure 2 in more detail.

[0100] As illustrated in FIG. 3, the fairing structure (140) is formed to surround the lug well (120) and lug (130) protruding from the outer surface of the fuselage skin (110) of the payload, and can be configured to have a continuous outer shape along the axial direction overall. In particular, FIG. 3 (a) shows a planar or top projection shape and (b) shows a side shape, so the shape features of the fairing structure (140) are expressed more clearly.

[0101] More specifically, the cross-section of the fairing structure (140) may be formed as an elongated ellipse or an asymmetrical ellipse, so that the shape transition from the cylindrical cross-section of the fuselage skin (110) to the lug well (120) portion may be gradual rather than abrupt. In this case, the elongated elliptical cross-section may be configured with the fuselage axial direction (x-axis direction) as the major axis and the radial direction as the minor axis, and in the case of an asymmetrical ellipse, the curvature of the upper and lower portions may be formed differently depending on the location of the lug well (120) or aerodynamic requirements. Through this, flow characteristics or radar reflection characteristics in a specific direction can be controlled more precisely.

[0102] In addition, the outer surface of the pairing structure (140) is formed as a curved surface with a continuously changing curvature, and is configured so that right-angled corners or abrupt changes in shape do not occur. That is, the pairing structure (140) can be implemented in a form in which multiple curved surfaces having different radii of curvature are smoothly connected, and the rate of change of curvature can also be designed to be continuously maintained. This configuration induces airflow to flow naturally along the outer shape, thereby suppressing flow separation and the generation of vortices, and at the same time has the effect of dispersing the reflection of radar waves.

[0103] Meanwhile, the pairing structure (140) can be formed continuously in a circumferential direction along the outer circumference of the lug well (120), and accordingly, the entire outer shape can have an integrated structure without local shape discontinuity. As shown in FIG. 3(a), the pairing structure (140) can be extended symmetrically or asymmetrically around the location where the lug well (120) is formed, and aerodynamic continuity can be secured by being formed continuously over a certain angle range in the circumferential direction. In addition, the structure may be formed as a single pairing, or it may be expanded in a manner in which a plurality of divided segments are combined to form the entire outer shape.

[0104] Additionally, the pairing structure (140) may be formed to have different curvature distributions in the front and rear corresponding to the protrusion direction of the lug well (120). That is, as shown in FIG. 3(b), the front region may have a relatively gentle increase in curvature to induce acceleration of the flow, while the rear region may be formed to have a gradually decreasing curvature considering pressure recovery and flow reattachment. By differentiating the curvature distributions in the front and rear in this way, the acceleration and deceleration sections of the flow are clearly separated, and overall flow stability can be improved.

[0105] Furthermore, the fairing structure (140) can have its external curvature adjusted in response to changes in the thickness of the boundary layer formed along the fuselage surface to minimize flow disturbances caused by the lug well (120). For example, in sections where the boundary layer is thick, the change in curvature can be made gentle to prevent flow separation, and in sections where the boundary layer is thin, a relatively large change in curvature can be allowed to secure the freedom of shape control. Through this, the occurrence of flow separation is suppressed under various flight conditions, and stable aerodynamic characteristics can be maintained.

[0106] In addition, the pairing structure (140) is not limited to the embodiment shown in FIG. 3 and can be modified into various forms depending on the number of lug wells (120), spacing between them, protrusion height, etc. For example, when a plurality of lug wells (120) are arranged in close proximity, they can be formed into a single integrated elongated oval pairing, and when they are arranged apart, independent pairing structures can be formed. In addition, if necessary, the pairing structure (140) may be designed with a left-right asymmetrical shape to further improve aerodynamic performance or radar reflection characteristics in a specific direction.

[0107] As such, the embodiment illustrated in FIG. 3 integrates an elongated or asymmetric elliptical cross-section, a continuous curvature surface, a continuous structure in the periphery direction, a differentiation of front and rear curvature distribution, and a boundary layer corresponding shape design, thereby suppressing aerodynamic performance degradation and improving radar reflection characteristics, while providing scalability capable of responding to various design conditions.

[0108] Figure 4 is a conceptual diagram showing the interior of the payload of Figure 1.

[0109] As illustrated in FIG. 4, the payload (100) of the present embodiment is characterized by being designed so that the internal space of the fuselage skin (110) is not encroached upon by an external fastening structure. That is, the lug well (120) is formed to protrude outward from the outer surface of the fuselage skin (110), and is configured so that a threaded fastening space that sinks into the fuselage is not formed as in the conventional method. Accordingly, as illustrated in FIG. 4, a state of “no lug well (threaded fastening) space” is maintained inside the fuselage skin (110), and the internal space can be formed as a continuous structure.

[0110] More specifically, the internal space of the outer shell (110) is an area for accommodating propellant or functional equipment, and can be formed continuously without interruption in the axial direction. At this time, as the lug well (120) is formed as an external protruding structure, there are no protrusions or depressions for separate fastening in the internal space, and accordingly, the propellant filling density is improved and non-uniformity of internal flow can be minimized. In addition, as the internal structure is simplified, the possibility of stress concentration is reduced, and the heat distribution can also be maintained more uniformly.

[0111] In addition, even when multiple lugs (130) are formed as shown in FIG. 4, each lug well (120) is configured to protrude outward, and no corresponding recessed structure is formed in the internal space. Accordingly, the continuity of the internal space is maintained despite the existence of multiple fastening structures, and this can be applied equally to a mount having a multi-mount structure. For example, even when the number of lugs (130) is expanded to two or more, the internal space can be maintained as an integrated structure by forming all lug wells (120) outward.

[0112] Meanwhile, the fairing structure (140) encloses the externally protruding lug well (120) and simultaneously performs the function of correcting only the external shape without interfering with the internal structure. That is, the fairing structure (140) is a structure additionally formed on the outer surface of the fuselage skin (110), and is designed to improve only the external aerodynamic shape and radar reflection characteristics without affecting the internal space. In addition, the interior of the fairing structure (140) may be formed as a hollow structure or may include reinforcing ribs as needed, but since this is also formed only on the outer side of the fuselage skin (110), it maintains a structure separated from the internal propellant space.

[0113] Furthermore, this structure can be extended to various embodiments. For example, it can be applied in the same way even when electronic equipment, fuel, or a composite functional module, rather than a propellant, is placed inside the outer shell (110), and the shape of the internal space can be implemented in various ways, such as a cylindrical shape, a multi-diameter structure, or a tapered structure. In addition, the externally protruding lug well (120) structure can be applied to various fastening methods (pin connection, clamp connection, etc.), and accordingly, the shape and size of the lug (130) can also be varied.

[0114] FIG. 5 is a flowchart of a design method for an aerodynamic and radar reflection reduction structure according to one embodiment of the present invention.

[0115] As illustrated in FIG. 5, the method for designing an aerodynamic and radar reflection reduction structure for a protruding lug well according to the present invention is a method for designing an aerodynamic and radar reflection reduction structure of a payload (100) externally mounted on an aircraft (200), comprising the steps of: defining the shape of a lug well (120) protruding from the outer surface of a fuselage skin (110) and a lug (130) formed in the lug well (120) (S100); forming a fairing structure (140) that surrounds the lug well (120), wherein the front region of the fairing structure (140) is formed to gradually rise from the outer shape of the fuselage and the rear region is formed in a tapered shape that gradually decreases (S102); setting the cross-sectional shape of the fairing structure (140) to be elliptical or asymmetrical elliptical and forming the curvature of the outer surface to change continuously (S104); and tilting the side of the fairing structure (140) so that the reflection direction of radar waves is dispersed in an off-axis direction (S106). It is characterized by being designed such that the rate of change in the cross-sectional area of ​​the fuselage shape is minimized by the fairing structure (140).

[0116] First, in the above step (S100), the shapes of the lug well (120) and the lug (130) are not limited to simple geometric definitions but can be set by simultaneously considering the coupling conditions with the aircraft (200), load transfer characteristics, and external protrusion height limit conditions. For example, the position, number, and spacing of the lug (130) are defined according to the aircraft mounting interface, and accordingly, the shape of the lug well (120) can also be optimized into an external protruding structure. In addition, at this step, the basic external shape data of the fuselage skin (110) is defined together and can be used as a standard for ensuring shape continuity in subsequent steps.

[0117] Next, in the above step (S102), the front and rear shapes of the fairing structure (140) may be formed as curve-based shapes that reflect aerodynamic requirements, rather than simple linear changes. In particular, the outer surface of the fairing structure (140) may be formed so that the curvature is continuous with the outer surface of the fuselage skin (110), and is designed so that no radial step difference occurs in the connection section. To this end, a mathematical interpolation technique (e.g., spline interpolation) may be applied to the connection section so that the radius of curvature and the rate of change of curvature change gradually, and a correction shape that takes into account actual manufacturing tolerances may be included.

[0118] Additionally, in the above step (S104), the cross-sectional shape of the pairing structure (140) may be set to go beyond a simple elliptical shape, so that the distribution of the cross-sectional area (A) according to the fuselage axial position (x) changes continuously. This is a key step for controlling the cross-sectional area change rate (dA / dx) so that it does not change abruptly. For example, the cross-sectional area distribution may be defined by a polynomial, an exponential function, or a freeform-based function, and may be optimized so that the cross-sectional area increase rate is maintained gradually in a specific section. Furthermore, the cross-sectional shape may be set to an elongated ellipse or an asymmetrical ellipse, and may be adjusted non-uniformly in the circumferential direction as needed.

[0119] Furthermore, in the above step (S106), the side shape of the fairing structure (140) may be designed considering radar reflection characteristics. Specifically, the side of the fairing structure (140) may be formed to include a surface inclined at a predetermined angle with respect to the centerline of the fuselage, so that incident radar waves are not concentrated and reflected in a specific direction but are dispersed in an off-axis direction. At this time, the inclination angle may be set as a single value, may be extended to a polyhedral structure having multiple angles, or may be implemented as a composite shape combining a curved surface and a flat surface.

[0120] In addition, the above design method can be iteratively optimized so that the rate of change in the cross-sectional area of ​​the fuselage shape is minimized by the fairing structure (140). In particular, the process may include iteratively correcting the shape based on the results of fluid analysis (CFD) or numerical analysis so that the square integral of the rate of change in cross-sectional area formed by the fairing structure (140) is minimized. In this process, after setting the initial shape, an iterative optimization loop may be performed to evaluate the aerodynamic performance and pressure distribution through analysis and adjust the shape parameters based on this. In addition, this optimization process can be extended to a multi-purpose optimization method that simultaneously considers various flight conditions (subsonic, transonic, supersonic).

[0121] Meanwhile, the above design method can be applied not only to a single lug well structure but also to cases where multiple lug wells exist. For example, when two or more lugs (130) are formed, a pairing structure (140) corresponding to each lug well (120) may be designed individually or designed to wrap multiple lug wells into a single integrated pairing structure, in which case the cross-sectional area distribution and curvature distribution may be integratedly optimized based on the overall structure.

[0122] In addition, the above design method can be extended in various ways depending on the application target. For example, design variables and optimization goals can be adjusted according to the type of aircraft (200), operating speed, level of radar avoidance requirements, etc., and artificial intelligence-based shape optimization techniques or data-based design techniques can be applied as needed.

[0123] And, FIG. 6 is a configuration diagram showing a combined system of aerodynamic and radar reflection reduction structures according to one embodiment of the present invention.

[0124] As illustrated in FIG. 6, the payload (100) of the aerodynamic and radar reflection reduction structure for the protruding lug well of the present invention is coupled to an aircraft (200) and comprises a fuselage skin (110), a lug well (120) protruding from the outer surface of the fuselage skin (110), a lug (130) formed in the lug well (120), and a fairing structure (140) surrounding the lug well (120). The side of the fairing structure (140) is formed to include a surface inclined at a predetermined angle with respect to the fuselage centerline, configured so that radar waves incident from the outside are reflected in an off-axis direction and are formed to suppress the corner reflector effect.

[0125] In addition, the coupling system of the present embodiment may be configured such that a mechanical coupling structure between the aircraft (200) and the payload (100) and an aerodynamic and radar reflection reduction structure are integrally implemented. In particular, the aforementioned payload (100) is detachably coupled to the aircraft (200) through a lug well (120) and a lug (130) protruding from the outer surface of the fuselage skin (110), and the lug (130) may be coupled by being inserted into or fastened to a corresponding coupling part (e.g., a mount bracket, a rail, or a pin coupling structure, etc.) provided on the aircraft (200).

[0126] More specifically, the lug (130) can be formed to conform to the specifications of the coupling interface of the aircraft (200) and can be implemented, for example, as a pin insertion type, a bolt fastening type, or a clamp fastening type structure. In this case, since the lug well (120) is formed to accommodate the fastening portion of the lug (130) in an outward direction, the internal space of the fuselage skin (110) can be maintained continuously without being encroached upon by the fastening structure. Accordingly, the placement efficiency of the propellant or internal equipment is improved, and structural stability can also be secured due to the simplification of the internal structure.

[0127] Additionally, the fairing structure (140) is formed to surround the lug well (120) and the lug (130), so as to maintain the continuity of the external shape even when combined with the aircraft (200). In particular, the side of the fairing structure (140) is formed to include a surface inclined at a predetermined angle with respect to the centerline of the fuselage, so as to induce radar waves incident from the outside to be reflected in an off-axis direction. At this time, the inclined surface may be formed as a single plane, or may be formed in a form in which a plurality of planes or curved surfaces are combined.

[0128] Meanwhile, the side of the pairing structure (140) can be formed in a flat or curved shape; in the case of a flat structure, it is easy to control reflection in a specific direction, and in the case of a curved structure, it is advantageous for dispersing reflected waves in multiple directions. Additionally, the pairing structure (140) is formed to include a curved structure with corner shapes removed, thereby suppressing the corner reflector effect that may occur due to right-angle corners or abrupt changes in shape. This structure prevents the phenomenon of radar reflection signals returning in the direction of incidence, thereby contributing to reducing the radar reflection cross-sectional area of ​​the entire system.

[0129] Additionally, the fairing structure (140) can be designed to maintain aerodynamic performance while coupled with the aircraft (200). For example, the fairing structure (140) can be formed such that the curvature changes continuously at the connection point with the outer shape of the aircraft (200), thereby minimizing flow disturbance at the connection point. Additionally, the fairing structure (140) can be designed so that the rate of change in cross-sectional area does not increase rapidly in the boundary region between the payload (100) and the aircraft (200), thereby suppressing the increase in drag that may occur at the connection point.

[0130] Furthermore, the coupling system can be extended to various embodiments. For example, when two or more lugs (130) are formed, the lugs may be spaced apart in the axial direction or dispersed in the circumferential direction, and accordingly, the pairing structure (140) may be formed individually corresponding to each lug position or formed as a single structure that integrally encloses multiple lugs. In addition, the coupling method and shape design may be changed depending on the type of aircraft (200) (aircraft, unmanned aerial vehicle, guided missile, etc.), and design variables may be adjusted to respond to various operating conditions.

[0131] Additionally, the pairing structure (140) can be implemented in an expandable manner in terms of material. For example, in addition to metal materials, it can be formed from a composite material to which a radar-absorbing material (RAM) is applied, and an electromagnetic wave-absorbing coating is applied to the surface to simultaneously achieve reflection reduction due to the shape and absorption effect due to the material.

[0132] Although various preferred embodiments of the present invention have been described above with some examples, the descriptions of various embodiments described in the "Specific details for carrying out the invention" section are merely illustrative, and those skilled in the art to which the present invention pertains will understand that the present invention can be modified in various ways or equivalent embodiments can be carried out based on the above description.

[0133] In addition, since the present invention can be implemented in various other forms, the present invention is not limited by the description above. The above description is provided merely to make the disclosure of the present invention complete and to fully inform those skilled in the art of the scope of the present invention, and it should be understood that the present invention is defined only by each claim of the claims. Explanation of the symbols

[0134] 100 : Payload 110: Fuselage skin 120 : Rugwell 130 : Rug 140 : Pairing Structure

Claims

Claim 1 A payload externally mounted on an aircraft, comprising: a fuselage skin forming the outer surface of the fuselage; a lug well protruding from the outer surface of the fuselage skin and including a fastening portion inside; a lug formed in the lug well for coupling with the aircraft; and a fairing structure formed on the outer circumference of the fuselage skin to surround the lug well, wherein the fairing structure is formed within a range not exceeding the maximum protrusion height of the lug well, and the lug is configured to remain exposed to the outside, and wherein the fairing structure is formed such that the rate of change (dA / dx) of the cross-sectional area (A) according to the fuselage axial position (x) changes continuously in order to mitigate the increase in local cross-sectional area caused by the lug well, and is designed such that the square integral of the rate of change of cross-sectional area is minimized. Claim 2 A payload of an aerodynamic and radar reflection reduction structure for a protruding lug well, characterized in that, in claim 1, the fairing structure is formed such that the curvature of the outer surface of the fuselage skin continuously matches the curvature, thereby preventing a radial step difference from occurring. Claim 3 A payload of an aerodynamic and radar reflection reduction structure for a protruding lug well, characterized in that, in claim 1, the lug is exposed to the outside from the lug well, and an opening is formed in the fairing structure to perform a coupling function without interference with the outer surface of the fairing structure. Claim 4 delete Claim 5 A payload externally mounted on an aircraft comprises: a fuselage skin; a lug well protruding from the outer surface of the fuselage skin; a lug formed in the lug well; and a fairing structure surrounding the lug well, wherein the fairing structure is formed such that its shape gradually changes from front to rear with respect to the flight direction, the front region is formed to gradually rise from the outer shape of the fuselage skin to align with the maximum height of the lug well, and the rear region is formed in a tapered shape that gradually decreases from the maximum height so as to minimize the rate of change in the cross-sectional area of ​​the fuselage outer shape, and wherein the fairing structure is configured such that the wave drag generated during flight is [according to] the following Equation 1, <Equation 1> (Here, D wave A payload with an aerodynamic and radar reflection reduction structure for a protruding lug well, characterized by being designed to minimize (A: cross-sectional area, x: axial position of the fuselage). Claim 6 A payload of an aerodynamic and radar reflection reduction structure for a protruding lug well, characterized in that, in claim 5, the forward region of the fairing structure is formed as a curved surface with a gradually increasing curvature at the connection portion with the fuselage outer shape. Claim 7 A payload of an aerodynamic and radar reflection reduction structure for a protruding lug well according to claim 5, characterized in that the rear region of the fairing structure is formed in a tapered shape that gradually decreases to maintain continuity with the fuselage shape. Claim 8 delete Claim 9 A payload externally mounted on an aircraft, comprising: a fuselage skin; a lug well protruding from the outer surface of the fuselage skin; a lug formed in the lug well; and a fairing structure surrounding the lug well, wherein the cross-section of the fairing structure is formed as an elongated ellipse or an asymmetric ellipse, and the outer surface of the fairing structure is formed as a curved surface with a continuously changing curvature so as not to cause right-angle corners or abrupt changes in shape, and wherein the fairing structure is formed to have different curvature distributions in the front and rear corresponding to the direction of protrusion of the lug well so as to separate the acceleration and deceleration sections of the flow. Claim 10 A payload of an aerodynamic and radar reflection reduction structure for a protruding lug well, characterized in that, in claim 9, the fairing structure is formed continuously in the circumferential direction along the outer circumference of the lug well and is configured so that the outer shape is integrated without local shape discontinuity. Claim 11 delete Claim 12 A payload of an aerodynamic and radar reflection reduction structure for a protruding lug well, characterized in that, in claim 9, the fairing structure is designed so that the outer curvature is continuously adjusted in response to changes in the thickness of the boundary layer formed along the fuselage surface to minimize flow disturbance caused by the lug well, and is configured so that flow separation is suppressed. Claim 13 delete Claim 14 delete Claim 15 delete Claim 16 delete Claim 17 A method for designing an aerodynamic and radar reflection reduction structure for a payload externally mounted on an aircraft, comprising: defining the shape of a lug well protruding from the outer surface of a fuselage skin and a lug formed in said lug well; forming a fairing structure that surrounds said lug well, wherein the front region of said fairing structure is formed to gradually rise from the outer shape of the fuselage and the rear region is formed in a tapered shape that gradually decreases; and setting the cross-sectional shape of said fairing structure to be elliptical or asymmetrical elliptical and forming the curvature of the outer surface to change continuously. A method for designing an aerodynamic and radar reflection reduction structure for a protruding lug well, comprising the step of tilting the side of the fairing structure to form the reflection direction of radar waves to be dispersed in an off-axis direction, wherein the fairing structure is designed to minimize the rate of change in the cross-sectional area of ​​the fuselage shape, and when the fairing structure is designed to minimize the rate of change in the cross-sectional area of ​​the fuselage shape, the shape is repeatedly corrected based on the results of fluid analysis or numerical analysis so that the square integral of the rate of change in the cross-sectional area of ​​the fuselage shape formed by the fairing structure is minimized. Claim 18 A method for designing an aerodynamic and radar reflection reduction structure for a protruding lug well, characterized in that, in the step of forming the fairing structure, the outer surface of the fairing structure is formed such that its curvature is continuous with that of the outer surface of the fuselage skin. Claim 19 A method for designing an aerodynamic and radar reflection reduction structure for a protruding lug well, characterized in that, in the step of setting the cross-sectional shape of the fairing structure, the cross-sectional shape is set such that the cross-sectional area distribution according to the axial position of the fuselage changes continuously. Claim 20 delete

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