Airship frame

Abstract

An airship frame comprises a fusiform supporting skeleton formed by a plurality of stiffening rings, longitudinal members and a keel girder, which are made up of composite tubes. The tubes of the stiffening rings have a triangular cross-section and contain a polyurethane foam core or filler, and the spaces described by the stiffening rings have tensioned diagonal cables arranged therein. The stiffening rings are arranged at a distance from one another that increases with distance from the centre of the airship, and the cross-sectional area of the tubes of the stiffening rings decreases with distance from the centre of the airship. The longitudinal members are connected to the stiffening rings and are curved throughout their entire length. One half of the longitudinal members is twisted in a clockwise direction and the other half is twisted in an anticlockwise direction, forming a lattice with diamond-shaped cells. The cross-sectional area of the tubes of the longitudinal members increases with proximity to the centre of the airship, and the ends of the longitudinal members are secured to the end stiffening rings. The keel girder is connected to the stiffening rings of the centre section of the airship. Spacers are installed at the junctions of the tubes, and the joints are glued and wrapped with prepreg, forming a monolithic exoskeleton. The result is that of increasing the structural reliability of the airship while simultaneously reducing the overall weight thereof.

Description

[0001] AIRSHIP FRAME

[0002] The claimed invention relates to the design of lighter-than-air aircraft, namely to manned and unmanned rigid-type airships (having a spatial frame / exoskeleton as a structure providing structural integrity and shape, cylinders with lifting gas with an internal pressure equal to the external atmospheric pressure, and not having a system of ballonets), equipped with a propulsion system and a control system, and can be used in airship construction.

[0003] Due to its large size and significant stresses (static and dynamic loads) during flight, an airship must be given a certain margin of safety. The static load is the result of the opposing action of gravity and gas lift. Much more complex and significant is the dynamic stress created as a result of the airship's flight, especially in adverse weather conditions. During translational motion, the airship experiences frontal resistance proportional to the cross-sectional area and the square of the speed of movement. In addition, during any maneuvering, additional loads of varying strength and direction arise in the airship's hull, as in an airplane. These additional loads increase especially when the airship encounters severe meteorological conditions; during strong gusts of wind, to which it is exposed, bending, twisting and other stresses arise in the airship's hull.In this regard, when designing an airship frame, it becomes necessary to combine exceptional structural strength with exceptional lightness (weight relative to the volume encompassed by the body).

[0004] The prior art discloses a frame for an airship (patent application FR2329509A1, Frame for rigid dirigible airship - has staggered polygonal frames with short struts to prevent buckling, published 27.05.1977), consisting of an assembly of rod or tubular sections which are assembled so as to form a lattice of a generally cylindrical shape, the cells of which are rhombuses with diagonals parallel and perpendicular to the longitudinal axis of the reinforcement, respectively, with each section constituting one side of the cell. Additionally, at least one polygonal frame is provided, located across the longitudinal axis, wherein this frame is formed by a circular assembly of rod or tubular sections, each of which is connected to the cell nodes. Two successive frames are separated by a selected number of circular rows of cells. A frame is provided for each annular row of cells.

[0005] An airship is known (patent application CN1087593A, The dirigible that is used for goods and passenger transportation, published 08.06.1994), intended for the transportation of goods and passengers, has a fuselage of a truss structure formed from nodal bodies, ring beams and spars inserted into fastening devices of the nodal bodies, and tension cables hooked onto the nodal bodies and tightening beams and spars on the nodal bodies, which form a spatial lattice structure with the fuselage of the truss structure. The ring beams and spars are made in the form of closed triangular hollow sections and are inserted into corresponding fastening devices extending in the longitudinal and circumferential direction of the fuselage of the truss structure or are put on them. The base of the triangular hollow sections is directed towards the outer side of the fuselage truss structure.The nodal bodies are formed as a single whole from fastening devices for triangular hollow sections, arranged in one plane at an angle equal to 90 degrees, and for ribs projecting beyond the inwardly directed corners with lugs for tension cables, as well as for ribs arranged approximately in the plane of the shell, connecting the zones of the corners of the base directed toward the outer side of the fastening devices for triangular hollow sections intended for lugs for tension cables. In the zone between the frame rings on the side members, couplings are located for installing pipe sections that form auxiliary rings.The fuselage of the truss structure consists of a parabolic nose section, occupying approximately more than 15% of the total length, smoothly adjoining it, expanding towards the tail with an opening angle of 1 to 8 degrees, a middle section, which has the shape of a truncated cone and occupies approximately more than 60% of the total length, adjoining it with a tear-off edge and tapering towards the tail at an angle of 12 to 28 degrees in the shape of a truncated cone of the tail section, occupying approximately more than 25% of the total length. The nodal bodies, ring beams, spars and tension cables consist of fiber-reinforced artificial material.

[0006] A frame for an airship with a supporting framework is known (patent application GB2300010A, Framework for eg airships, published 07.10.1998), consisting of longitudinal and transverse frames. Each of the individual supports consists of at least three longitudinal beams that run parallel to each other and form a polygonal body with struts, wherein these struts are located in planes formed in each case by two longitudinal beams, and these struts connect the longitudinal trusses to each other at the joints in the form of a framework. The joints consist of at least one main shell with recesses for accommodating the longitudinal beam and transverse struts and at least one protective shell that covers the longitudinal beam and transverse struts together with the main shell in the form of a bushing with a geometric closure. The longitudinal beam and cross posts are inserted into the recesses and glued flush to the recess surfaces.The main and protective shells contain protruding flanges on their contact parts for gluing to each other. The surfaces of the recesses of the main and protective shells are covered with glue applied in liquid form to the surfaces of the recesses. The glue can be applied in the form of an adhesive film. The airship frame consists of fiber-reinforced plastic, such as carbon fiber. The main and protective shells consist of fiber-reinforced plastic, such as fiberglass. The glue used can harden under the influence of heat.

[0007] The disadvantages of the designs of the specified technical solutions are the following:

[0008] 1) the presence of a large number of dry connections - riveted, bolted and clamped, as well as the presence of connection nodes, which are the main areas of structural risk, since they are mobile and, accordingly, have weaker load-bearing characteristics than other points of the frame;

[0009] 2) the use of metal (fully or partially) lattice / mesh trusses, including those of triangular cross-section, which make the structure heavier, which is critical in airship construction;

[0010] 3) the use of structural elements made of metals that are subject to corrosion from atmospheric conditions and embrittlement as a result of contact with hydrogen molecules;

[0011] 4) reduced rigidity and strength of the structure as a whole, which leads to a decrease in its reliability.

[0012] The closest technical solution to the claimed one is an airship (see patent US11396356B2, Method and apparatus for lighter-than-air airship with improved structure and delivery system, published 26.07.2022), consisting of an exoskeleton formed by a plurality of beams of different lengths and a plurality of nodes. Each beam is connected at opposite ends to one of the nodes, while the beams are connected to the nodes to form isosceles triangles between adjacent beams. Each beam, passing along the circumference of the airship, is connected through a connection to a node at opposite ends with beams of the same length passing along the circumference of the airship. Couplings are provided on each node. Moreover, each coupling is attached to the end of the corresponding beam, so that the corresponding beam can be located at an angle relative to the node.The airship is elliptical in shape and its exoskeleton has multiple regions: a front region, a rear region, and one or more central regions between the front and rear regions. The diameter of the front and rear regions is each smaller than the diameter of one or more central regions. The beams are made of carbon fiber and are defined by tubular walls, each beam having the same diameter and a wall thickness of 0.125 inches. The disadvantages of such an airship include the following:.

[0013] 1) It was originally intended that the entire exoskeleton would be formed from completely identical "Fuller" structures (of which the classic geodesic mesh dome is formed), which would make the entire structure very simple and technologically feasible from a manufacturing point of view; however, it is impossible to create the characteristic aerodynamic profile of an airship with beams of equal length, so the present patent assumes the use of beams of different lengths. This effectively negated the economic and technological value of the design.

[0014] 2) In addition, the nodes connecting the beams involve movable joints and bolted and clamped fastenings, which makes the entire structure susceptible to a decrease in rigidity as a result of long-term operation.

[0015] 3) Also, the dimensions of the exoskeleton required to build any effective rigid airship imply a significant load on these units, whereas the present patent does not imply the use of frames or similar systems that take on structural loads.

[0016] 4) The use of aluminum and steel elements in the creation of units creates a risk to the structural integrity of the body, since hydrogen is supposed to be used as a lifting gas - any leak creates a risk of embrittlement of critical metal elements.

[0017] The technical task facing the invention is to create a rigid monolithic exoskeleton of an airship without "dry" and / or movable joints from a material that does not lose its strength characteristics as a result of contact with gases that can be used as lifting gases (hydrogen, helium, their mixtures with inhibitors) or over time as a result of corrosion or embrittlement, while having the lowest weight with the best strength characteristics, the structure of which would simultaneously ensure uniform distribution of loads and shocks in compression and tension throughout the frame and would level out the flaws in the characteristics of the selected material (for example, such as the brittleness of carbon under impact loads along secant vectors and the much lower strength of carbon fiber under longitudinal compression loads compared to tensile loads).

[0018] The technical result of the claimed invention is to increase the reliability of the airship design while simultaneously minimizing its overall weight.

[0019] The technical result is achieved in that the airship frame contains a spindle-shaped supporting framework formed by a plurality of frames, longitudinal elements and a keel truss consisting of pipes made of composite materials. The cross-section of the frame pipes has the shape of a triangle, the apex of which is directed inside the frame, and inside the frame pipes there is a foamed polyurethane core or filler. Inside the spaces described by each frame, systems of diagonal cables are stretched, each of which consists of at least three cables. The frames are located from each other at a distance that increases with the distance from the central cross-section of the airship to its edges. In this case, the cross-sectional area of ​​the frame pipes is different and decreases with the distance from the central cross-section of the airship to its edges in proportion to the decrease in the area of ​​the space described by the frame.At least six longitudinal elements are connected to all frames and have a bend in the longitudinal centerline along their entire length, with one half of the longitudinal elements twisted clockwise and the other half counterclockwise, forming a grid with diamond-shaped cells. The ends of the longitudinal elements are fixed to the end frames of the smallest diameter and cross-section. The cross-sectional area of ​​the pipes of each longitudinal element increases as it approaches the central cross-section of the airship. The keel truss is connected to the frames of the central section of the airship. Profiled spacers are installed at the points where the pipes of all structural elements of the airship frame adjoin each other, ensuring the maximum contact area of ​​the fastened surfaces, and the nodes of these connections are glued and wrapped crosswise with tape or a bundle of prepreg, forming, after the prepreg hardens, a single monolithic exoskeleton of the airship.

[0020] The joints can be glued with polymer-based material.

[0021] The keel truss pipes can have a triangular, rectangular or circular cross-section.

[0022] The pipes of the longitudinal elements can have a triangular, rectangular or circular cross-section and are formed by winding.

[0023] The tubes of the frames, longitudinal elements and / or keel trusses can be reinforced with polymer material.

[0024] Spacers can be made using the 3D printing method from carbon fiber reinforced polymer.

[0025] Frames with internal filling or core can be produced by vacuum infusion method.

[0026] The claimed invention is explained by illustrations. Figure 1 shows the device of prestressed ring frames and their assembly, Figure 2 shows the device of the keel truss, Figure 3 shows the "keel truss - frames" system, Figure 4 shows the geometry of the longitudinal elements and the general view of their assembly, Figure 5 shows the device of the monolithic connection unit of the longitudinal elements and frames, Figure 6 shows the general view of the airship frame.

[0027] The numbers indicate the following:

[0028] 1 - frame;

[0029] 2 - longitudinal element;

[0030] 3 - keel truss;

[0031] 4 - connection unit; 5 - spacer.

[0032] The external spatial frame of the airship (exoskeleton) has a spindle-shaped form and is formed from a set of frames 1, a set of longitudinal elements 2, a keel truss 3 and joints between them 4. The main structural elements of the frames 1, longitudinal elements 2 and keel truss 3 are pipes made of composite materials (for example, carbon fiber or fiberglass), which can be reinforced with a polymer.

[0033] Frames 1 are rings, in cross-section having the form of a composite triangular tube (preferably an equilateral triangle with rounded corners), consisting of a core made of lightweight foam material (acting as the "male" form in a "female-male" connection) and a main carbon fiber surface formed by the vacuum infusion method. As a result, the frame tube is solid, seamless, has no hollow spaces inside - it is filled with a polyurethane foam filler or core, providing additional rigidity and load-bearing capacity of the frame. In this case, one of the vertices of the cross-section triangle is directed strictly inward, described by the frame, and the base of the triangle opposite to it is directed outward. Each frame is prestressed using a system of cables, consisting of at least three (see Fig. 1).The use of filler and a system of cables allows to reduce the material consumption and weight of the frame by almost 2.5-3 times compared to similar frames made of carbon fiber, while maintaining the same strength and load-bearing characteristics. Frames 1 conventionally divide the airship frame into sections: tail, central and bow. The frames of the central section are distinguished by the largest diameter of the inscribed circle and have the largest cross-sectional area. The frames of the tail and nose sections are distinguished by the smallest cross-sectional area and a smaller diameter of the inscribed circle. Frames 1 in the set are located from each other at a distance that increases as you move from the central cross-section of the airship to its nose and tail. The distance between the frames is calculated using the formula:.

[0034] Ь( П+ 1) = b n *q n (next b (n+2 ) = b n *q n+1) where b is the distance between two frames forming the central (largest diameter) section, n is the frame number (with frame numbering starting from the central frame) towards the bow or stern from the central frame, which has the number 1, q is the distance coefficient (selected based on a set of factors such as the target load and its placement, the material used and the tectonics of the hull itself), for example, 1.3, however, the formula may have a different form.

[0035] The cross-sectional area of ​​frames 1 changes proportionally to the change in the area of ​​space described by the frame itself - the larger the frame, the larger the area of ​​its cross-section and vice versa.

[0036] The longitudinal elements 2 are hollow round tubes made of composite materials (e.g. carbon fiber), formed into segments by winding. The set of longitudinal elements 2 consists of at least six. At the same time, depending on the dimensions of the airship and the tasks it performs, the number of longitudinal elements 2 can vary. The longitudinal elements 2 have a smooth bend of their longitudinal axis, providing a rotation around the longitudinal axis of the airship of about 180 degrees. In this case, half of the longitudinal elements are twisted clockwise, and the other half - counterclockwise, forming a two-layer lattice structure with diamond-shaped cells.This arrangement ensures the highest rigidity of the structure with its lower weight, minimizes the risk of twisting the airship frame, ensures optimal distribution of loads from oncoming air flows, possible collisions and fastening of cargo on the external suspension, and optimizes the distribution of loads from the outer shell and internal lifting cells (since the compression and tension loads with a vector along the longitudinal axis of the airship (with a deviation of + / - 10 degrees) are always approximately (deviation of + / - 10 degrees) parallel to the vectors of at least half of the longitudinal beams; this ensures the highest efficiency of carbon fiber tubes of standard diagonal layout). The cross-sectional diameter of each longitudinal element 2 is variable: the largest in the central section of the airship and significantly smaller in the nose and tail sections.

[0037] The keel truss 3 is a rigid frame (see Fig. 2) made of hollow pipes of rectangular or round cross-section made of composite materials formed by the winding method. The keel truss 3 consists of parts, its length is equal to the length of the central section of the airship itself, and the fastening is carried out to the frames 1. The joints of the pipes of the keel truss 3 are made by gluing and are additionally monolithized with layers of carbon fiber and winding with prepreg bundles. Epoxy resin, for example, can be used as glue. The keel truss performs a dual function: it connects the frames of the central section of the airship, ensuring their precise and constant positioning relative to each other (eliminates torsion); as an element to which cargo is fastened, it ensures uniform distribution of point loads over the entire frame when installing the gondola and fastening the cargo.The design of the connection nodes 4 of all the main elements (frames 1, longitudinal elements 2 and keel truss 3) of the airship frame allows them to be combined into a single monolithic exoskeleton. For this purpose, profiled spacers 5 (see Fig. 5) are used in the design of the connection nodes 4, ensuring an increase in the area of ​​the fastened surfaces. Spacers 5 are made by the 3D printing method from a polymer material and are reinforced with carbon fibers.The monolithization of the connection nodes 4 is carried out as follows: during the assembly of the airship frame, spacers 5 with glue previously applied to their surfaces, identical to the material of the matrices of the main parts made of carbon fiber (for example, epoxy resin), are placed at the intersections of its main elements (frame-keel truss, frame-longitudinal element, keel truss-longitudinal element, longitudinal element-longitudinal element), after which each connection node 4 is wrapped with prepreg bundles, laying them out “criss-cross”, after which the prepreg hardens, forming a strong monolithic connection.

[0038] The use of a rigid monolithic exoskeleton of an airship without “dry” and / or movable joints made of a material that does not lose its strength characteristics and has the lowest weight is based on the following principles:

[0039] 1. The diameters of frames 1, the distance between them, the length and attachment points of longitudinal elements 2 ensure the preservation of the geometry of the airship exoskeleton.

[0040] 2. The mesh structure formed by twisted longitudinal elements 2 primarily takes on "area" loads (directed to the entire or a significant part of the surface of the conditional space closed in the exoskeleton contour). These loads include those formed by air flows from the outside, exerting pressure on the outer soft shell, which in turn presses on the exoskeleton, as well as the lifting force of the cells with lifting gas inside the exoskeleton.

[0041] 3. The fastening of loads and additional elements (for example, gondolas, pylons with engine rockers) is carried out to the keel truss 3 and / or frames 1, after which the load is evenly distributed on the longitudinal elements 2. Thus, the entire exoskeleton of the airship works as a single whole, accepting and distributing loads, shocks and stresses of different classes, arriving at different sections and elements of the structure.

[0042] 4. The twisted geometry of each longitudinal element 2 and the connection of all longitudinal elements 2 into a single mesh structure ensure the transfer of vertical loads not only through the frames 1, but also directly through the system of longitudinal elements itself. The main task of the exoskeleton is to transfer the lifting force of the cells with gas (which is transferred primarily to the mesh structure of the longitudinal elements 2) to the payload moved by the airship without losing structural integrity under environmental influences and the design operational speed and maneuverability of the airship.

[0043] 5. This is the reason for the number of longitudinal elements 2 - it is significantly larger, and their thickness and load-bearing capacity are lower, while the keel truss 3 and especially the frames 1 are designed in such a way as to ensure maximum load-bearing capacity and strength of the airship frame.

[0044] 6. The maximum number of connection nodes 4 of the longitudinal elements 2 with the keel truss 3-frames 1 system is provided, and the connections themselves are monolithic by gluing with epoxy resin through special spacers 5, which expand the contact area, and wrapping the connection nodes 4 with prepreg bundles.

[0045] The use of the claimed airship frame design allows achieving the following advantages:

[0046] - the complex structure of the frame has high rigidity, without moving or “dry” (bolted, riveted or clamped) joints and without the use of metals (aluminum, steel, etc.) in its composition, which allows the general characteristics of rigidity and strength of the frame to be brought closer to the characteristics of a carbon fiber monocoque;

[0047] - the combination of the "criss-cross" layout of the prepreg fibers and the use of longitudinal elements with bends in the center lines minimizes the problem of significant differences in the strength characteristics of composites depending on the load vector and fiber layout for the entire structure;

[0048] - minimization of the risk of weakening the rigidity of the structure during long-term operation under conditions of vibrations and loads along different vectors due to the monolithization of all connections by gluing and winding with prepreg;

[0049] - obtaining a rigid structure of the “exoskeleton” type with a minimum weight per unit volume and a virtually ideal distribution of both compression and tension loads applied to any part of the structure, due to the spindle-shaped installation of longitudinal elements and the presence of powerful ring frames of triangular cross-section.

Claims

CLAUSE OF INVENTION 1. An airship frame comprising a spindle-shaped supporting framework formed by a plurality of frames, longitudinal elements and a keel truss consisting of tubes made of composite materials, the cross-section of the frame tubes having the shape of a triangle, the apex of which is directed inside the frame, and inside the frame tubes there is a foamed polyurethane core or filler, wherein inside the spaces described by each frame, systems of diagonal cables are stretched, each of which consists of at least three cables, the frames are placed from each other at a distance increasing as they move away from the central cross-section of the airship to its edges, wherein the cross-sectional area of the frame tubes is different and decreases as they move away from the central cross-section of the airship to its edges in proportion to the decrease in the area of the space described by the frame,longitudinal elements in an amount of at least six are connected to all frames and have a bend in the longitudinal centerline along their entire length, wherein one half of the longitudinal elements is twisted clockwise, and the other half is twisted counterclockwise, forming a grid with diamond-shaped cells, wherein the cross-sectional area of the pipes of each longitudinal element increases as it approaches the central cross-section of the airship, and the ends of the longitudinal elements are fixed to the end frames of the smallest diameter and cross-section, the keel truss is connected to the frames of the central section of the airship, profiled spacers are installed at the points where the pipes of all structural elements of the airship frame adjoin each other, ensuring the maximum contact area of the fastened surfaces, and the nodes of these connections are glued and wrapped crosswise with tape or a bundle of prepreg, forming a single monolithic exoskeleton of the airship after hardening of the prepreg.

2. An airship frame according to item 1, characterized in that the connection nodes are glued with a polymer-based material.

3. The airship frame according to item 1, characterized in that the keel truss pipes have a triangular, rectangular, or circular cross-section.

4. The airship frame according to item 1, characterized in that the pipes of the longitudinal elements have a triangular, rectangular, or circular cross-section.

5. The airship frame according to item 1, characterized in that the tubes of the frames and / or longitudinal elements and / or keel truss are reinforced with material using the winding method.

6. The airship frame according to item 1, characterized in that the spacers are made by the 3D printing method from a polymer reinforced with carbon fibers, a polymer 7. An airship frame according to item 1, characterized in that the frames with an internal filler or core are manufactured using a vacuum infusion method.

Images