Free filling type endurance level solid engine shell structure and preparation method

Abstract

The invention discloses a free filling type endurance level solid engine shell structure and a preparation method, and relates to the technical field of engine structures. According to the method, a combustion chamber shell of a barrel structure, a front sealing head arranged at one end of the combustion chamber shell and a rear sealing head arranged at the other end of the combustion chamber shell are included; the rear sealing head is in threaded connection with the combustion chamber shell; the front sealing head and the combustion chamber shell are both made of a carbon fiber-epoxy resin composite material; and the rear sealing head is made of a metal material. A part of composite materials are used for replacing metal materials, and the structural mass is effectively reduced under the condition that the inner molded surface size requirement and the static strength requirement are met.

Description

Technical Field

[0001] The present invention relates to the technical field of engine structures, and in particular to a free-loading endurance-level solid engine casing structure and a preparation method thereof. Background Art

[0002] The casing structure of a solid rocket engine is mainly composed of a front head, a combustion chamber casing and a rear head. For engines using free-loading propellants, the engine casing is required to be detachable and must adopt a segmented open structure. After the speed-increasing engine has finished working and the endurance engine is started, an inclined nozzle needs to be placed on the rear head. At present, the casing of a free-loading engine generally uses the metal material D6AC steel. Through a machining process, the open end of the combustion chamber casing is threadedly connected to the rear head. This structural form is heavy and difficult to meet the design requirements of lightweight projectile structures. For engines using wall-mounted cast propellants, the engine casing structure is integral and does not need to be disassembled, and a fully composite material structure has been achieved. Therefore, it is urgent to develop a casing structure and preparation method suitable for lightweight free-loading endurance-level solid engines to better meet the design requirements of lightweight structures and promote the technological progress of my country's rocket engines. Summary of the invention

[0003] In view of the deficiencies existing in the above-mentioned background technology, the present invention provides a free-loading endurance-class solid engine casing structure and a preparation method for the design demand of lightweight structure. The engine casing structure is mainly composed of a front head, a combustion chamber casing and a rear head. The front head and the combustion chamber casing are made of T700 carbon fiber / E51 epoxy resin composite material, and the rear end cover is made of 7075 aluminum alloy, which are connected by threads. The optimized design scheme and connection form characteristics are determined based on the design requirements of the engine casing, and a lightweight free-loading endurance-class solid engine casing structure and preparation method that meet the design requirements such as inner surface size, static strength and lightweight are obtained.

[0004] The first object of the present invention is to provide a free-loading endurance-stage solid engine casing structure for a solid rocket engine, wherein the engine casing structure comprises a combustion chamber casing of a cylindrical structure, a front head provided at one end of the combustion chamber casing, and a rear head provided at the other end of the combustion chamber casing;

[0005] The rear head is connected to the combustion chamber casing via threads;

[0006] The front end cover and the combustion chamber shell are both made of carbon fiber-epoxy resin composite materials;

[0007] The rear end cover is made of metal.

[0008] Preferably, the front head and the combustion chamber casing are an integrally formed structure;

[0009] The rear end cap is formed by machining of metal material.

[0010] Preferably, the static strength requirement of the engine casing structure is that the structure does not break down under an internal pressure lower than 4 MPa, and the pressure drop does not exceed 0.5 MPa within a holding time of 70 seconds under an internal pressure of 4 MPa.

[0011] Preferably, the mass of the engine casing structure is m, and the mass satisfies (m0-m) / m0≥30%, wherein m0 is the mass of the all-metal free-loading endurance-class solid rocket engine casing structure.

[0012] The second object of the present invention is to provide a design method for a free-loading endurance-level solid engine casing structure, comprising:

[0013] Determine the molding scheme and structural form of the engine casing;

[0014] According to the design requirements and weight reduction indicators of the all-metal free-loading endurance-class solid motor casing structure in the same use environment, the design requirements of the lightweight free-loading endurance-class solid motor casing structure are determined;

[0015] Based on the test, the optimal winding tension of the fiber winding and the modulus and strength of the composite material were determined; composite materials were selected for the front head and combustion chamber shell, and metal materials were selected for the rear head;

[0016] According to the design requirements of the lightweight free-loading endurance-class solid engine casing structure, the preliminary design of the composite casing layer of the front head and the combustion chamber, the preliminary thickness of the rear head and the size of the connection structure are determined based on grid theory, empirical formulas and design standards;

[0017] According to the preliminary design of the composite shell layup of the front head and combustion chamber, as well as the preliminary thickness of the rear head and the dimensions of the connection structure, and in accordance with the design requirements of the lightweight free-loading endurance-class solid engine shell structure, the finite element method is used to optimize the layup design and the rear head thickness design scheme, and the strength of the connection structure dimensions is checked to determine the final lightweight free-loading endurance-class solid engine shell structure.

[0018] Preferably, the engine housing molding scheme and structural form include:

[0019] The free-loading endurance-class solid engine casing adopts a segmented, large-opening structure;

[0020] An inclined nozzle and heat insulation assembly are installed on the rear head of the endurance-class solid engine;

[0021] A virtual rear head is used to wind the front head, combustion chamber shell and the virtual rear head into an integrated form, and the rear head is machine-cut after curing to form a composite material large-opening front head and combustion chamber shell;

[0022] The rear head is formed by metal machining.

[0023] Preferably, the preliminary ply design includes the number, angle and sequence of plies;

[0024] The connection structure dimensions include the number of thread teeth, thread root width, thread working height, thread inner diameter and pitch.

[0025] The third object of the present invention is to provide a method for preparing a free-loading endurance-stage solid engine casing structure as described in any one of claims 1 to 4, characterized in that it comprises the following steps:

[0026] According to the inner profile of the engine casing structure, prepare the metal core mold and the metal filling sheet of the front head pole hole;

[0027] Brush the mold release agent on the surface of the core mold, paste the insulation layer, paste the metal filling sheet on the outside of the insulation layer at the position of the pole hole of the front head, and then cover the surface of the insulation layer with a plastic film;

[0028] The carbon fiber-epoxy resin is wound on the core mold according to a certain rule, and after the winding is completed, it is cured and demoulded to form a shell structure;

[0029] The shell structure is machined to cut off the rear head, and external threads are machined according to the connection design to obtain the combustion chamber shell including the front head;

[0030] Machine the metal rear head and machine the internal thread;

[0031] The outer thread on the combustion chamber casing is threadably connected with the inner thread of the rear head to obtain a free-loading endurance-class solid engine casing structure.

[0032] Preferably, when the carbon fiber-epoxy resin is wound on the core mold according to a certain rule, it includes: the continuous carbon fiber yarn bundle is impregnated with the epoxy resin matrix and then wound on the core mold.

[0033] Preferably, a sealing ring is installed at the connection between the combustion chamber shell and the rear head;

[0034] The rear end cover is provided with a nozzle and a heat insulation component.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention provides a free-loading endurance-class solid engine casing structure and a preparation method. Compared with the existing all-metal engine casing in the same use environment, the present invention uses part of the composite material to replace the metal material, thereby effectively reducing the structural mass while meeting the internal surface size requirements and static strength requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a two-dimensional structural diagram of the engine casing structure;

[0038] Figure 2 Schematic diagram of the core mold structure;

[0039] Figure 3 This is the flow chart of finite element calculation for shell structure;

[0040] Figure 4 Schematic diagram of the engine housing connection structure. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0042] The present invention aims at the design requirements of lightweight solid engine structure, and provides a free-loading endurance-class solid engine casing structure and preparation method. The engine casing structure is mainly composed of a front head, a combustion chamber casing and a rear head. The front head and the combustion chamber casing are made of T700 carbon fiber / E51 epoxy resin composite material, and the rear end cover is made of 7075 aluminum alloy, which are connected by threads. The optimized design scheme and connection form characteristics are determined based on the design requirements of the engine casing, and a lightweight free-loading endurance-class solid engine casing structure and preparation method that meet the design requirements such as inner surface size, static strength and lightweight are obtained.

[0043] In order to achieve the above-mentioned object, the first aspect of the present invention provides a free loading endurance-level solid engine casing structure, see Figure 1 As shown, the engine is used for a solid rocket, and the engine casing structure includes a combustion chamber casing of a cylindrical structure, a front head provided at one end of the combustion chamber casing, and a rear head provided at the other end of the combustion chamber casing;

[0044] The rear head is connected to the combustion chamber casing via threads;

[0045] The front end cover and the combustion chamber shell are both made of carbon fiber-epoxy resin composite materials;

[0046] The rear end cover is made of metal.

[0047] The free-loading endurance-class solid rocket engine casing structure provided by the present invention is oriented to the design requirements of lightweight solid engine structure, and is composed of three parts: composite material front head, combustion chamber casing, and metal rear head. The structure is designed for the engine casing structure form, ply characteristics, and connection method in accordance with the internal surface dimension requirements, static strength requirements, and lightweight requirements of the all-metal free-loading endurance-class solid rocket engine casing structure in the same use environment.

[0048] Wherein, the front head and the combustion chamber shell are an integrally formed structure.

[0049] The rear end cap is formed by machining of metal material.

[0050] The static strength requirement of the engine casing structure is that the structure will not be damaged under an internal pressure lower than 4Mpa, and the pressure drop will not exceed 0.5Mpa within 70 seconds of holding time under an internal pressure of 4Mpa.

[0051] The mass of the engine casing structure is m, and the mass satisfies (m0-m) / m0≥30%, wherein m0 is the mass of the all-metal free-loading endurance-class solid rocket engine casing structure.

[0052] The second aspect of the present invention provides a design method for a free-loading endurance-stage solid engine casing structure, comprising:

[0053] Determine the molding scheme and structural form of the engine casing;

[0054] According to the design requirements and weight reduction indicators of the all-metal free-loading endurance-class solid motor casing structure in the same use environment, the design requirements of the lightweight free-loading endurance-class solid motor casing structure are determined;

[0055] Based on the test, the optimal winding tension of the fiber winding and the modulus and strength of the composite material were determined; composite materials were selected for the front head and combustion chamber shell, and metal materials were selected for the rear head;

[0056] According to the design requirements of the lightweight free-loading endurance-class solid engine casing structure, the preliminary design of the composite casing layer of the front head and the combustion chamber, the preliminary thickness of the rear head and the size of the connection structure are determined based on grid theory, empirical formulas and design standards;

[0057] According to the preliminary design of the composite shell layup of the front head and combustion chamber, as well as the preliminary thickness of the rear head and the dimensions of the connection structure, and in accordance with the design requirements of the lightweight free-loading endurance-class solid engine shell structure, the finite element method is used to optimize the layup design and the rear head thickness design scheme, and the strength of the connection structure dimensions is checked to determine the final lightweight free-loading endurance-class solid engine shell structure.

[0058] The molding scheme and structure of the engine casing include:

[0059] The free-loading endurance-class solid engine casing adopts a segmented, large-opening structure;

[0060] An inclined nozzle and heat insulation assembly are installed on the rear head of the endurance-class solid engine;

[0061] A virtual rear head is used to wind the front head, combustion chamber shell and the virtual rear head into an integrated form, and the rear head is machine-cut after curing to form a composite material large-opening front head and combustion chamber shell;

[0062] The rear head is formed by metal machining.

[0063] Among them, the preliminary design of ply layup includes the number, angle and sequence of plies;

[0064] The connection structure dimensions include the number of thread teeth, thread root width, thread working height, thread inner diameter and pitch.

[0065] Exemplarily, a solid rocket engine structure design method includes:

[0066] A. Determine the molding scheme and structural form of the engine casing;

[0067] B. Based on the design requirements of the engine casing structure, determine the optimized design scheme and connection form characteristics of the structure to obtain an engine casing structure that meets the design requirements.

[0068] In step A, the free-loading endurance-class engine casing is a segmented, large-opening structure, and an inclined nozzle and a heat-insulating assembly are installed on the endurance-class engine rear head. A virtual rear head is used to wrap the front head, the combustion chamber casing, and the virtual rear head as a whole, and the rear head is machined and cut after curing to form a composite material large-opening front head and combustion chamber casing. The rear head has a complex structure and is formed by metal machining.

[0069] In step B, the specific implementation process is as follows:

[0070] (B1) Determine the design requirements for the lightweight free-loading endurance-class solid rocket engine case structure based on the design requirements and weight reduction indicators for the full-metal free-loading endurance-class solid rocket engine case structure in the same use environment; the design requirements for the full-metal free-loading endurance-class solid rocket engine case structure in the same use environment include internal surface dimension requirements, static strength requirements, and lightweight requirements; the internal surface dimension requirements refer to the internal surface dimensions of the lightweight free-loading endurance-class solid rocket engine case being the same as the internal surface dimensions of the full-metal free-loading endurance-class solid rocket engine case; the static strength requirements refer to the fact that the various parts of the lightweight free-loading endurance-class solid rocket engine case structure do not suffer damage at a pressure lower than the blasting pressure P0; the lightweight requirements refer to the weight reduction effect of the lightweight free-loading endurance-class solid rocket engine case structure compared with the full-metal free-loading endurance-class solid rocket engine case structure in the same use environment;

[0071] (B2) Determine the materials to be used for the segmented structure, and determine the optimal winding tension for fiber winding, as well as the modulus and strength of the composite material based on the test; select composite materials for the front head and the combustion chamber shell, and metal materials for the rear head; perform NOL ring tension tests and composite unidirectional plate tensile tests to determine the optimal winding tension for fiber winding, as well as the modulus and strength of the composite material;

[0072] (B3) According to the engine casing structural design requirements obtained in step B1, determine the preliminary design of the front head and combustion chamber composite casing layer, the preliminary thickness of the rear head and the connection structure dimensions based on grid theory, empirical formulas and design standards; the layer design includes the number, angle and sequence of layers, and the connection structure dimensions include the number of thread teeth, thread root width, thread working height, thread inner diameter and pitch; this is directly related to the load-bearing capacity and connection strength of the composite casing;

[0073] (B4) Based on the preliminary design of the engine casing structure in step B3 and the design requirements obtained in step B1, the finite element method is used to optimize the layer design and the rear head thickness design scheme, and the strength of the connection structure dimensions is checked to determine the final lightweight free-loading endurance-class solid rocket engine casing structure.

[0074] A second aspect of the present invention provides a method for preparing a free-loading endurance-level solid engine casing structure, comprising the following steps:

[0075] According to the inner profile of the engine casing structure, prepare the metal core mold and the metal filling sheet of the front head pole hole;

[0076] Brush the mold release agent on the surface of the core mold, paste the insulation layer, paste the metal filling sheet on the outside of the insulation layer at the position of the pole hole of the front head, and then cover the surface of the insulation layer with a plastic film;

[0077] The carbon fiber-epoxy resin is wound on the core mold according to a certain rule, and after the winding is completed, it is cured and demoulded to form a shell structure;

[0078] The shell structure is machined to cut off the rear head, and external threads are machined according to the connection design to obtain the combustion chamber shell including the front head;

[0079] Machine the metal rear head and machine the internal thread;

[0080] The outer thread on the combustion chamber casing is threadably connected with the inner thread of the rear head to obtain a free-loading endurance-class solid engine casing structure.

[0081] The method of winding the carbon fiber-epoxy resin on the core mold according to a certain rule includes: impregnating the continuous carbon fiber yarn bundle with the epoxy resin matrix and then winding the bundle on the core mold.

[0082] A sealing ring is installed at the connection between the combustion chamber shell and the rear head.

[0083] The rear end cover is provided with a nozzle and a heat insulation component.

[0084] Exemplarily, a method for preparing a free-loading lightweight solid rocket engine casing structure comprises the following steps:

[0085] (C1) According to the inner surface of the engine casing structure, a metal core mold and a metal filling sheet for the front end hole are prepared; wherein the metal filling sheet for the front end hole is mainly used to prevent yarn slippage at the front end hole during winding.

[0086] (C2) A mold release agent is applied to the surface of the core mold, and a heat-insulating layer is pasted. A metal filler sheet is pasted and fixed to the outside of the heat-insulating layer at the position of the front end hole. Then, a layer of plastic film is tension-coated on the surface of the heat-insulating layer, and the adhesive is allowed to stand and solidify.

[0087] (C3) Check the winding equipment, set the winding tension, input the winding code into the winding machine host computer, perform longitudinal and circumferential winding in sequence according to the layer design, and finally perform circumferential winding multiple times to reach the barrel thickness;

[0088] (C4) To prepare a step structure at the front head with a height higher than the barrel section, circumferential winding is performed at the corresponding position;

[0089] (C5) After winding is completed, curing, demoulding and cleaning are carried out;

[0090] (C6) Machine the cut-off rear head, machine the external thread according to the connection design, and machine the front head step;

[0091] (C7) Metal rear head is machined and cut, internal threads are machined, thermal insulation components are bonded and machined;

[0092] (C8) Install the sealing ring and connect the combustion chamber shell to the metal rear head through threads.

[0093] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0094] Example 1

[0095] An embodiment of the present invention provides a free-loading lightweight solid engine casing structure that can be applied to the endurance level of a certain type of missile, including a molding scheme for the engine casing and determination of the structural form, an optimized design scheme for the structure and a method for determining the connection form, a method for determining the form characteristics and the optimized design scheme for the layup design.

[0096] S1. Determine the molding scheme and structural form of the engine housing. The specific process is as follows:

[0097] like Figure 1 As shown in the figure, the engine casing structure can be divided into three parts: the front head, the combustion chamber casing and the rear head. The rear head has a complex structure and an inclined nozzle is placed on it. The fiber winding and laying process are difficult, so it is made of metal materials. Through the virtual rear head, the front head, the combustion chamber casing and the virtual rear head can be wound into a whole. After curing, the rear head is machined and cut to form a large opening structure to realize free loading of propellant. The composite combustion chamber casing is threadedly connected to the metal rear head to realize free disassembly of the engine structure.

[0098] S2. Determine the optimal design scheme and connection form characteristics of the structure based on the design requirements of the engine casing structure. The specific process is as follows:

[0099] 2.1 As shown in step B1, the design requirements for the free-loading endurance-class all-metal engine casing are as follows:

[0100] (1) Inner surface dimension requirements: combustion chamber diameter 164 mm, length 304 mm, front head height 52 mm, major axis radius 82 mm, minor axis radius 54 mm; rear head height 44.6 mm, major axis radius 87 mm, minor axis radius 48.7 mm

[0101] (2) Static strength requirements: withstand internal pressure of not less than 4 MPa without structural damage; the pressure drop within 70 seconds under 4 MPa internal pressure shall not exceed 0.5 MPa;

[0102] (3) Lightweight requirements: Compared with an all-metal engine casing structure of the same size and performance, the weight reduction index shall be no less than 30%.

[0103] 2.2 As shown in step B2, the front head and combustion chamber shell are made of T700 / epoxy resin, and the rear head is made of 7075 aluminum alloy. The optimal winding tension is 30N, the modulus is 8.78GPa, and the strength is 81.79MPa.

[0104] 2.3 As shown in step B3, based on the design requirements (1) of B1, the winding core mold is designed and the core mold structure is prepared using low carbon steel, such as Figure 2 As shown. Based on the grid theory, the shell wall thickness is designed to be 2.05mm, and the preliminary winding parameters of the engine shell are determined. The thickness of the spiral winding layer and the circumferential winding layer are 0.35mm and 0.2mm respectively. The number of spiral winding layers is 3, and the number of circumferential winding layers is 5. According to the empirical formula, the thickness of the metal rear head is 3.0mm.

[0105] 2.4 As shown in step B4, adopt Figure 3 The calculation process is to perform finite element calculation of the shell structure, optimize the winding angle parameters, and obtain the optimal winding angle of the engine shell. Based on the size optimization, the optimal thickness of the metal back cover is 2.5mm. According to the thread design standard, the cohesive force model is used to calculate the failure process of the connection structure thread delamination and debonding, and it is determined that the thread top angle pitch is about 3.7mm, and the number of teeth of the connection structure thread is designed to be 9 teeth, such as Figure 4 shown.

[0106] S3. Determine the method for preparing the engine housing, the specific process is as follows:

[0107] (C1) Based on the requirements of the internal surface dimensions of the engine casing structure in 2.1, prepare the metal core mold and the metal filling sheet of the front head pole hole;

[0108] (C2) A mold release agent is applied to the surface of the core mold, and a heat-insulating layer is pasted. A metal filler sheet is pasted and fixed to the outside of the heat-insulating layer at the position of the front end hole. Then, a layer of plastic film is tension-coated on the surface of the heat-insulating layer, and the adhesive is allowed to stand and solidify.

[0109] (C3) Check the winding equipment, set the winding tension to 30N, enter the winding code on the winding machine host computer, and follow the layer design According to the predetermined linear path, the carbon fiber yarn bundle impregnated with epoxy resin is reciprocated longitudinally and hoop-wound in sequence, and finally hoop-wound twice to achieve a barrel thickness of 2.05 mm;

[0110] (C4) The step height at the front head is higher than that of the barrel section, and circumferential winding is performed at the corresponding position;

[0111] (C5) After winding, cure at 180°C for 6 hours, and demould and clean after natural cooling;

[0112] (C6) Machine the cut-off rear head, machine the external thread according to the connection design, and machine the front head step;

[0113] (C7) Metal rear head is machined and cut, internal threads are machined, thermal insulation components are bonded and machined;

[0114] (C8) Install the sealing ring and connect the combustion chamber casing to the rear head through threads.

[0115] The free-loading lightweight solid rocket engine casing structure provided in this embodiment has a mass of 1832g, which is more than 30% lighter than the all-metal casing structure, and can withstand the design requirement of 4MPa working pressure.

[0116] The present invention describes preferred embodiments and their effects. However, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0117] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A free-loading endurance-level solid engine casing structure, characterized in that: The engine is used for a solid rocket, wherein the engine casing structure includes a combustion chamber casing of a cylindrical structure, a front head provided at one end of the combustion chamber casing, and a rear head provided at the other end of the combustion chamber casing; The rear head is connected to the combustion chamber casing via threads; The front end cover and the combustion chamber shell are both made of carbon fiber-epoxy resin composite materials; The rear end cover is made of metal.

2. The free-loading endurance-level solid engine casing structure according to claim 1 is characterized in that: The front head and the combustion chamber shell are an integrally formed structure; The rear end cap is formed by machining of metal material.

3. The free-loading endurance-level solid engine casing structure according to claim 1 is characterized in that: The static strength requirement of the engine casing structure is that the structure will not be damaged under an internal pressure lower than 4Mpa, and the pressure drop will not exceed 0.5Mpa within 70 seconds of holding time under an internal pressure of 4Mpa.

4. The free-loading endurance-level solid engine casing structure according to claim 1 is characterized in that: The mass of the engine casing structure is m, and the mass satisfies (m0-m) / m0≥30%, wherein m0 is the mass of the all-metal free-loading endurance-class solid rocket engine casing structure.

5. A design method for a free-loading endurance-level solid rocket engine casing structure according to any one of claims 1 to 4, characterized in that: include: Determine the molding scheme and structural form of the engine casing; According to the design requirements and weight reduction indicators of the all-metal free-loading endurance-class solid motor casing structure in the same use environment, the design requirements of the lightweight free-loading endurance-class solid motor casing structure are determined; Determine the optimal winding tension of fiber winding and the modulus and strength of composite materials based on experiments; Determine that the front head and combustion chamber shell are made of composite materials, and the rear head is made of metal materials; According to the design requirements of the lightweight free-loading endurance-class solid engine casing structure, the preliminary design of the composite casing layer of the front head and the combustion chamber, the preliminary thickness of the rear head and the size of the connection structure are determined based on grid theory, empirical formulas and design standards; According to the preliminary design of the composite shell layup of the front head and combustion chamber, as well as the preliminary thickness of the rear head and the dimensions of the connection structure, and in accordance with the design requirements of the lightweight free-loading endurance-class solid engine shell structure, the finite element method is used to optimize the layup design and the rear head thickness design scheme, and the strength of the connection structure dimensions is checked to determine the final lightweight free-loading endurance-class solid engine shell structure.

6. The design method of the free-loading endurance-level solid rocket engine casing structure according to claim 5 is characterized in that: The molding scheme and structure of the engine casing include: The free-loading endurance-class solid engine casing adopts a segmented, large-opening structure; An inclined nozzle and heat insulation assembly are installed on the rear head of the endurance-class solid engine; A virtual rear head is used to wind the front head, combustion chamber shell and the virtual rear head into an integrated form, and the rear head is machine-cut after curing to form a composite material large-opening front head and combustion chamber shell; The rear head is formed by metal machining.

7. The design method of the free-loading endurance-level solid rocket engine casing structure according to claim 5 is characterized in that: The preliminary layup design includes the number, angle and sequence of the plies; The connection structure dimensions include the number of thread teeth, thread root width, thread working height, thread inner diameter and pitch.

8. A method for preparing a free-loading endurance-level solid engine casing structure according to any one of claims 1 to 4, characterized in that: The following steps are involved: According to the inner profile of the engine casing structure, prepare the metal core mold and the metal filling sheet of the front head pole hole; Brush the mold release agent on the surface of the core mold, paste the insulation layer, paste the metal filling sheet on the outside of the insulation layer at the position of the pole hole of the front head, and then cover the surface of the insulation layer with a plastic film; The carbon fiber-epoxy resin is wound on the core mold according to a certain rule, and after the winding is completed, it is cured and demoulded to form a shell structure; The shell structure is machined to cut off the rear head, and external threads are machined according to the connection design to obtain the combustion chamber shell including the front head; Machine the metal rear head and machine the internal thread; The outer thread on the combustion chamber casing is threadably connected with the inner thread of the rear head to obtain a free-loading endurance-class solid engine casing structure.

9. The method for preparing the free-loading endurance-level solid engine casing structure according to claim 7, characterized in that: When the carbon fiber-epoxy resin is wound on the core mold according to a certain rule, it includes: the continuous carbon fiber yarn bundle is impregnated with the epoxy resin matrix and then wound on the core mold.

10. The method for preparing the free-loading endurance-level solid engine casing structure according to claim 7, characterized in that: A sealing ring is installed at the connection between the combustion chamber shell and the rear head; The rear end cover is provided with a nozzle and a heat insulation component.

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