A free-loading endurance class solid engine shell structure and a preparation method thereof

Abstract

The application discloses a free-filling type endurance level solid engine shell structure and a preparation method, and relates to the technical field of engine structures. The method comprises a combustion chamber shell of a cylinder structure, a front end cover arranged at one end of the combustion chamber shell and a rear end cover arranged at the other end of the combustion chamber shell; the rear end cover is connected with the combustion chamber shell through threads; the material of the front end cover and the combustion chamber shell is carbon fiber-epoxy resin composite material; and the material of the rear end cover is metal material. The application uses part of composite material to replace metal material, effectively reduces the structure quality under the conditions of meeting the inner surface size requirement and the static strength requirement.

Description

Technical Field

[0001] This invention relates to the field of engine structure technology, specifically to a free-loading, endurance-grade solid rocket motor housing structure and its preparation method. Background Technology

[0002] The solid rocket motor casing structure mainly consists of a front end cap, a combustion chamber casing, and a rear end cap. For engines using free-fill propellants, the engine casing must be detachable, necessitating a segmented open structure. After the acceleration stage engine completes its operation, the sustaining stage engine starts, and a slanted nozzle needs to be installed on the rear end cap. Currently, free-fill engine casings are generally made of D6AC steel, with the open end of the combustion chamber casing threaded to the rear end cap via machining. This structural form is heavy and difficult to meet the design requirements for lightweight projectile structures. For engines using wall-mounted cast propellants, the engine casing structure is integral and does not require disassembly, achieving a fully composite material structure. Therefore, there is an urgent need to develop a lightweight free-fill sustaining stage solid rocket motor casing structure and its fabrication method to better meet the design requirements for lightweight structures and promote the advancement of rocket engine technology in my country. Summary of the Invention

[0003] To address the shortcomings of the aforementioned background technology, this invention provides a free-loading, endurance-grade solid rocket motor housing structure and its fabrication method, specifically addressing the design requirements for lightweight construction. The housing structure mainly comprises a front end cap, a combustion chamber housing, and a rear end cap. The front end cap and combustion chamber housing are made of T700 carbon fiber / E51 epoxy resin composite material, while the rear end cap is made of 7075 aluminum alloy. They are connected by threads. Based on the design requirements of the engine housing, an optimized design scheme and connection characteristics are determined, resulting in a lightweight, free-loading, endurance-grade solid rocket motor housing structure and its fabrication method that meet design requirements for internal dimensions, static strength, and lightweight construction.

[0004] The first objective of this invention is to provide a free-loading, endurance-class solid rocket motor housing structure for use in a solid rocket motor. The motor housing structure includes a combustion chamber housing with a cylindrical structure, a front end cap disposed at one end of the combustion chamber housing, and a rear end cap disposed at the other end of the combustion chamber housing.

[0005] The rear end cap is connected to the combustion chamber shell by a thread;

[0006] Both the front end cap and the combustion chamber shell are made of carbon fiber-epoxy resin composite material;

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

[0008] Preferably, the front end cap and the combustion chamber shell are integrally formed.

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

[0010] Preferably, the static strength requirement of the engine housing structure is that the structure does not fail under an internal pressure of less than 4 MPa, and the pressure drop does not exceed 0.5 MPa within 70 seconds of holding pressure at 4 MPa.

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

[0012] The second objective of this invention is to provide a design method for a free-loading, endurance-class solid rocket motor casing structure, comprising:

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

[0014] Based on the design requirements and weight reduction targets of the all-metal free-filling endurance solid rocket motor casing structure in the same operating environment, the design requirements of the lightweight free-filling endurance solid rocket motor casing structure are determined.

[0015] Based on experiments, the optimal winding tension of fiber winding, as well as the modulus and strength of composite materials, were determined; it was determined that composite materials should be used for the front end cap and combustion chamber shell, while metal materials should be used for the rear end cap.

[0016] Based on the design requirements of the lightweight, free-filling, endurance-grade solid rocket motor casing structure, the preliminary design of the composite material shell layup of the front end and combustion chamber, the preliminary thickness of the rear end, and the dimensions of the connection structure are determined based on grid theory, empirical formulas, and design standards.

[0017] Based on the preliminary design of the composite material shell layup of the front end and combustion chamber, the preliminary thickness of the rear end and the dimensions of the connecting structure, and in accordance with the design requirements of the lightweight free-loading endurance solid rocket motor shell structure, the finite element method was used to optimize the layup design and the rear end thickness design scheme, and the strength verification of the connecting structure dimensions was performed to determine the final lightweight free-loading endurance solid rocket motor shell structure.

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

[0019] The casing of the free-loading, endurance-class solid rocket motor adopts a segmented, large-opening structure.

[0020] An angled nozzle and heat shield are installed on the rear end cap of the endurance-grade solid rocket motor.

[0021] A virtual rear end cap is used to integrally wind and form the front end cap, combustion chamber shell, and virtual rear end cap. After curing, the rear end cap is machined and cut to form a composite material large-opening front end cap and combustion chamber shell.

[0022] The rear end cap is formed by metal machining.

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

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

[0025] A third objective of this invention is to provide a method for preparing the free-loading, endurance-grade solid rocket motor casing structure according to any one of claims 1 to 4, characterized by comprising the following steps:

[0026] Based on the internal shape of the engine housing structure, prepare a metal core mold and a metal filler sheet for the front end cap pole hole;

[0027] Apply release agent to the core mold surface, attach the insulation layer, attach a metal filler sheet to the outside of the insulation layer at the pole hole position of the front end, and then cover the insulation layer surface with a plastic film.

[0028] Carbon fiber and epoxy resin are wound onto a mandrel according to a certain pattern. After winding, the mandrel is cured and demolded to form a shell structure.

[0029] The rear end cap is machined off the shell structure, and external threads are machined according to the connection design to obtain a combustion chamber shell containing the front end cap;

[0030] The rear end cap is machined from metal and has internal threads machined.

[0031] By connecting the external threads on the combustion chamber housing with the internal threads on the rear end cap, a free-loading, endurance-grade solid rocket motor housing structure is obtained.

[0032] Preferably, when winding carbon fiber-epoxy resin onto the mandrel in a certain pattern, the process includes: impregnating a continuous carbon fiber yarn bundle with an epoxy resin matrix and then winding it onto the mandrel.

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

[0034] The rear end cap is equipped with a nozzle and a heat insulation component.

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] This invention provides a free-loading, endurance-grade solid rocket motor housing structure and manufacturing method. Compared with existing all-metal engine housings used in the same environment, this invention uses composite materials to replace some metal materials, effectively reducing the structural weight while meeting the requirements for internal dimensions and static strength. Attached Figure Description

[0037] Figure 1 This is a two-dimensional structural diagram of the engine casing.

[0038] Figure 2 This is a schematic diagram of the core mold structure;

[0039] Figure 3 This is a flowchart of the finite element calculation for a shell structure.

[0040] Figure 4 Schematic diagram of the engine housing connection structure. Detailed Implementation

[0041] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0042] This invention addresses the design requirements for lightweight solid rocket motor structures by providing a free-loading, endurance-grade solid rocket motor casing structure and its fabrication method. The motor casing structure mainly consists of a front end cap, a combustion chamber casing, and a rear end cap. The front end cap and combustion chamber casing are made of T700 carbon fiber / E51 epoxy resin composite material, while the rear end cap is made of 7075 aluminum alloy. All components are connected by threads. Based on the design requirements of the motor casing, an optimized design scheme and connection characteristics are determined, resulting in a lightweight, free-loading, endurance-grade solid rocket motor casing structure and fabrication method that meets design requirements for internal dimensions, static strength, and lightweight design.

[0043] To achieve the above objectives, a first aspect of the present invention provides a free-loading, endurance-grade solid rocket motor housing structure, see [link to previous section]. Figure 1 As shown, this engine is used in a solid rocket. The engine casing structure includes a combustion chamber shell with a cylindrical structure, a front end cap provided at one end of the combustion chamber shell, and a rear end cap provided at the other end of the combustion chamber shell.

[0044] The rear end cap is connected to the combustion chamber shell by a thread;

[0045] Both the front end cap and the combustion chamber shell are made of carbon fiber-epoxy resin composite material;

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

[0047] The free-loading, endurance-class solid rocket motor casing structure provided by this invention addresses the design requirements for lightweight solid rocket motor structures. It consists of three parts: a composite material front end cap, a combustion chamber casing, and a metal rear end cap. The structure is designed to meet the internal dimensional requirements, static strength requirements, and lightweight requirements of all-metal free-loading, endurance-class solid rocket motor casing structures operating in the same environment, focusing on the design of the casing's structural form, ply characteristics, and connection methods.

[0048] The front end cap and the combustion chamber shell are integrally formed.

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

[0050] The static strength requirement for the engine housing structure is that the structure will not be damaged under an internal pressure of less than 4 MPa, and the pressure drop will not exceed 0.5 MPa within 70 seconds of holding pressure at 4 MPa.

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

[0052] A second aspect of the present invention provides a design method for a free-loading, endurance-class solid rocket motor housing structure, comprising:

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

[0054] Based on the design requirements and weight reduction targets of the all-metal free-filling endurance solid rocket motor casing structure in the same operating environment, the design requirements of the lightweight free-filling endurance solid rocket motor casing structure are determined.

[0055] Based on experiments, the optimal winding tension of fiber winding, as well as the modulus and strength of composite materials, were determined; it was determined that composite materials should be used for the front end cap and combustion chamber shell, while metal materials should be used for the rear end cap.

[0056] Based on the design requirements of the lightweight, free-filling, endurance-grade solid rocket motor casing structure, the preliminary design of the composite material shell layup of the front end and combustion chamber, the preliminary thickness of the rear end, and the dimensions of the connection structure are determined based on grid theory, empirical formulas, and design standards.

[0057] Based on the preliminary design of the composite material shell layup of the front end and combustion chamber, the preliminary thickness of the rear end and the dimensions of the connecting structure, and in accordance with the design requirements of the lightweight free-loading endurance solid rocket motor shell structure, the finite element method was used to optimize the layup design and the rear end thickness design scheme, and the strength verification of the connecting structure dimensions was performed to determine the final lightweight free-loading endurance solid rocket motor shell structure.

[0058] Engine housing molding scheme and structural form, including:

[0059] The casing of the free-loading, endurance-class solid rocket motor adopts a segmented, large-opening structure.

[0060] An angled nozzle and heat shield are installed on the rear end cap of the endurance-grade solid rocket motor.

[0061] A virtual rear end cap is used to integrally wind and form the front end cap, combustion chamber shell, and virtual rear end cap. After curing, the rear end cap is machined and cut to form a composite material large-opening front end cap and combustion chamber shell.

[0062] The rear end cap is formed by metal machining.

[0063] The preliminary design of the ply layup includes the number, angle, and sequence of the ply layups;

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

[0065] An exemplary method for designing a solid rocket motor structure includes:

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

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

[0068] In step A, the free-loading extended-range engine casing is a segmented, large-opening structure. An angled nozzle and heat shield are mounted on the rear end cap of the extended-range engine. A virtual rear end cap is used, integrally winding the front end cap, combustion chamber casing, and virtual rear end cap together. After curing, the rear end cap is machined and cut to form a composite material large-opening front end cap and combustion chamber casing. The rear end cap has a complex structure and is formed by metal machining.

[0069] Step B is implemented as follows:

[0070] (B1) Based on the design requirements and weight reduction targets of the all-metal free-loading solid rocket motor casing structure for the same operating environment, the design requirements for the lightweight free-loading solid rocket motor casing structure are determined. The design requirements for the all-metal free-loading solid rocket motor casing structure for the same operating environment include internal surface dimension requirements, static strength requirements, and lightweighting requirements. The internal surface dimension requirements refer to the fact that the internal surface dimensions of the lightweight free-loading solid rocket motor casing are the same as those of the all-metal free-loading solid rocket motor casing. The static strength requirements refer to the fact that the lightweight free-loading solid rocket motor casing structure does not fail under a pressure lower than the burst pressure P0. The lightweighting requirements refer to the weight reduction effect of the lightweight free-loading solid rocket motor casing structure compared to the all-metal free-loading solid rocket motor casing structure for the same operating environment.

[0071] (B2) Determine the materials to be used for the segmented structure, and determine the optimal winding tension of fiber winding, as well as the modulus and strength of composite materials based on experiments; composite materials are selected for the front end and combustion chamber shell, and metal materials are selected for the rear end; NOL ring tension test and composite material one-way plate tensile test are carried out to determine the optimal winding tension of fiber winding, as well as the modulus and strength of composite materials.

[0072] (B3) Based on the engine housing structure design requirements obtained in step B1, determine the preliminary design of the composite material housing layup for the front end and combustion chamber, the preliminary thickness of the rear end, and the dimensions of the connection structure based on grid theory, empirical formulas, and design standards. The layup design includes the number, angle, and sequence of the layups, and the dimensions of the connection structure include the number of thread teeth, the thread root width, the thread working height, the thread inner diameter, and the thread pitch. This is directly related to the load-bearing capacity and connection strength of the composite material housing.

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

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

[0075] Based on the internal shape of the engine housing structure, prepare a metal core mold and a metal filler sheet for the front end cap pole hole;

[0076] Apply release agent to the core mold surface, attach the insulation layer, attach a metal filler sheet to the outside of the insulation layer at the pole hole position of the front end, and then cover the insulation layer surface with a plastic film.

[0077] Carbon fiber and epoxy resin are wound onto a mandrel according to a certain pattern. After winding, the mandrel is cured and demolded to form a shell structure.

[0078] The rear end cap is machined off the shell structure, and external threads are machined according to the connection design to obtain a combustion chamber shell containing the front end cap;

[0079] The rear end cap is machined from metal and has internal threads machined.

[0080] By connecting the external threads on the combustion chamber housing with the internal threads on the rear end cap, a free-loading, endurance-grade solid rocket motor housing structure is obtained.

[0081] The process of winding carbon fiber-epoxy resin onto the mandrel according to a certain pattern includes: impregnating a continuous carbon fiber yarn bundle with an epoxy resin matrix and then winding it onto the mandrel.

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

[0083] The rear end cap is equipped with a nozzle and a heat insulation component.

[0084] An exemplary method for fabricating a free-filling lightweight solid rocket motor casing structure includes the following steps:

[0085] (C1) Based on the internal shape of the engine housing structure, prepare a metal core mold and a metal filler sheet for the front end cap pole hole; wherein, the metal filler sheet for the front end cap pole hole mainly prevents the yarn from slipping at the front end cap pole hole during the winding process.

[0086] (C2) Apply release agent to the core mold surface, attach the insulation layer, and attach a fixed metal filler sheet to the outside of the insulation layer at the front end cap pole hole position. Then, cover the insulation layer with a plastic film under tension and allow the adhesive to cure statically.

[0087] (C3) Check the winding equipment, set the winding tension, input the winding code into the upper computer of the winding machine, and perform longitudinal and circumferential winding in sequence according to the layup design. Finally, perform multiple circumferential windings to achieve the desired cylinder thickness.

[0088] (C4) To prepare a stepped structure at the front end cap with a height higher than the cylinder section, circumferential winding is performed at the corresponding position;

[0089] (C5) After winding, cure, demold, and clean;

[0090] (C6) After machining the end cap, according to the connection design, machine the external thread and machine the front end cap step;

[0091] (C7) Metal rear end cap is machined and formed, machined internal thread, bonded heat insulation components and machined;

[0092] (C8) Install the sealing ring and thread the combustion chamber shell to the metal rear end cap.

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

[0094] Example 1

[0095] This invention provides a free-loading lightweight solid rocket motor housing structure applicable to the endurance stage of a certain type of missile, including the determination of the engine housing forming scheme and structural form, the determination of the structural optimization design scheme and the connection form, and the determination of the optimization design scheme of the formal features and the layering design.

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

[0097] like Figure 1 As shown, the engine casing structure can be divided into three parts: the front end cap, the combustion chamber casing, and the rear end cap. The rear end cap has a complex structure and houses an angled nozzle, making fiber winding and laying processes difficult; therefore, it is made of metal. Through a virtual rear end cap, the front end cap, combustion chamber casing, and virtual rear end cap can be integrally wound and formed. After curing, the rear end cap is machined and cut to form a large opening structure, allowing for free propellant loading. The composite material combustion chamber casing is threadedly connected to the metal rear end cap, enabling free disassembly of the engine structure.

[0098] S2. Based on the engine casing structural design requirements, determine the optimized design scheme and connection characteristics of the structure. The specific process is as follows:

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

[0100] (1) Internal dimensions requirements: Combustion chamber diameter 164mm, length 304mm, front head height 52mm, major axis radius 82mm, minor axis radius 54mm; rear head height 44.6mm, major axis radius 87mm, minor axis radius 48.7mm.

[0101] (2) Static strength requirements: The structure shall withstand an internal pressure of not less than 4 MPa without being damaged; the pressure drop shall not exceed 0.5 MPa within 70 seconds of holding the pressure at 4 MPa.

[0102] (3) Lightweight requirements: Compared with an all-metal engine casing structure of the same size and performance, the weight reduction target shall not be less than 30%.

[0103] 2.2 As shown in step B2, the front end cap and combustion chamber shell are made of T700 / epoxy resin, and the rear end cap 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 of B1, (1) complete the design of the winding mandrel, and use low carbon steel to prepare the mandrel structure, such as... Figure 2 As shown. Based on grid theory, the shell wall thickness is designed to be 2.05 mm. The initial winding parameters for the engine shell are determined: the thicknesses of the helical winding layer and the circumferential winding layer are 0.35 mm and 0.2 mm, respectively; the number of helical winding layers is 3, and the number of circumferential winding layers is 5. According to empirical formulas, the thickness of the metal rear end cap is 3.0 mm.

[0105] 2.4 As shown in step B4, adopt... Figure 3 The calculation process involves finite element analysis of the shell structure, optimization of the winding angle parameters, and obtaining the optimal winding angle for the engine shell. Based on size optimization, the optimal thickness of the metal back end cap was determined to be 2.5mm. According to thread design standards, the cohesive force model was used to calculate the delamination and debonding failure process of the thread in the connection structure, determining the thread pitch at the point angle to be approximately 3.7mm. The thread tooth count for the connection structure was designed to be 9 teeth. Figure 4 As shown.

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

[0107] (C1) Based on the dimensional requirements of the inner surface of the engine housing structure in 2.1, a metal core mold and a metal filler sheet for the front end cap pole hole were prepared;

[0108] (C2) Apply release agent to the core mold surface, attach the insulation layer, and attach a fixed metal filler sheet to the outside of the insulation layer at the front end cap pole hole position. Then, cover the insulation layer with a plastic film under tension and allow the adhesive to cure statically.

[0109] (C3) Check the winding equipment, set the winding tension to 30N, input the winding code into the winding machine's host computer, and follow the layup design. According to the predetermined linear path, the carbon fiber yarn bundles impregnated with epoxy resin are wound longitudinally and circumferentially in sequence, and finally wound circumferentially twice to achieve a cylinder thickness of 2.05mm.

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

[0111] (C5) After winding, cure at 180℃ for 6 hours, then demold and clean after natural cooling;

[0112] (C6) After machining the end cap, according to the connection design, machine the external thread and machine the front end cap step;

[0113] (C7) Metal rear end cap is machined and formed, machined internal thread, bonded heat insulation components and machined;

[0114] (C8) Install the sealing ring and thread the combustion chamber shell to the rear end cap.

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

[0116] This invention describes preferred embodiments and their effects. However, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to include both the preferred embodiments and all changes and modifications falling within the scope of this invention.

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

Claims

1. A free-loading, endurance-grade solid rocket motor casing structure, characterized in that, The engine is used in solid rockets. The engine casing structure includes a combustion chamber casing with a cylindrical structure, a front end cap at one end of the combustion chamber casing, and a rear end cap at the other end of the combustion chamber casing. The rear end cap is connected to the combustion chamber shell by a thread; Both the front end cap and the combustion chamber shell are made of carbon fiber-epoxy resin composite material; The rear end cap is made of metal. The front end cap and the combustion chamber shell are integrally formed structures; The rear end cap is formed by machining metal material. The static strength requirement for the engine housing structure is that the structure will not be damaged under an internal pressure of less than 4 MPa, and the pressure drop will not exceed 0.5 MPa within 70 seconds of holding pressure at 4 MPa. The mass of the engine casing structure is m The quality satisfies ,in, m 0 represents the structural mass of the all-metal free-loading, endurance-class solid rocket motor casing; The free-loading, endurance-grade solid rocket motor housing structure is manufactured according to the following steps: Based on the internal shape of the engine housing structure, prepare a metal core mold and a metal filler sheet for the front end cap pole hole; Apply release agent to the core mold surface, attach the insulation layer, attach a metal filler sheet to the outside of the insulation layer at the pole hole position of the front end, and then cover the insulation layer surface with a plastic film. Carbon fiber and epoxy resin are wound onto a mandrel according to a certain pattern. After winding, the mandrel is cured and demolded to form a shell structure. The rear end cap is machined off the shell structure, and external threads are machined according to the connection design to obtain a combustion chamber shell containing the front end cap; The rear end cap is machined from metal and has internal threads machined. By connecting the external threads on the combustion chamber housing with the internal threads on the rear end cap, the free-loading, endurance-grade solid rocket motor housing structure is obtained. Free-loading, endurance-grade solid rocket motor casing structure; When carbon fiber-epoxy resin is wound onto a mandrel in a certain pattern, it includes: passing a continuous carbon fiber yarn bundle through an epoxy resin matrix and then winding it onto the mandrel. A sealing ring is installed at the connection between the combustion chamber shell and the rear end cap; The rear end cap is equipped with a nozzle and a heat insulation component.

2. A design method for the free-loading, endurance-class solid rocket motor casing structure as described in claim 1, characterized in that, include: Determine the engine housing molding scheme and structural form; Based on the design requirements and weight reduction targets of the all-metal free-filling endurance solid rocket motor casing structure in the same operating environment, the design requirements of the lightweight free-filling endurance solid rocket motor casing structure are determined. The optimal winding tension of the fiber winding, as well as the modulus and strength of the composite material, were determined based on experiments. The front end cap and combustion chamber shell were selected from composite materials, while the rear end cap was selected from metal materials. Based on the design requirements of the lightweight, free-filling, endurance-grade solid rocket motor casing structure, the preliminary design of the composite material shell layup of the front end and combustion chamber, the preliminary thickness of the rear end, and the dimensions of the connection structure are determined based on grid theory, empirical formulas, and design standards. Based on the preliminary design of the composite material shell layup of the front end and combustion chamber, the preliminary thickness of the rear end and the dimensions of the connecting structure, and in accordance with the design requirements of the lightweight free-loading endurance solid rocket motor shell structure, the finite element method was used to optimize the layup design and the rear end thickness design scheme, and the strength verification of the connecting structure dimensions was performed to determine the final lightweight free-loading endurance solid rocket motor shell structure.

3. The design method for the free-loading, endurance-class solid rocket motor casing structure according to claim 2, characterized in that, Engine housing molding scheme and structural form, including: The casing of the free-loading, endurance-class solid rocket motor adopts a segmented, large-opening structure. An angled nozzle and heat shield are installed on the rear end cap of the endurance-grade solid rocket motor. A virtual rear end cap is used to integrally wind and form the front end cap, combustion chamber shell, and virtual rear end cap. After curing, the rear end cap is machined and cut to form a composite material large-opening front end cap and combustion chamber shell. The rear end cap is formed by metal machining.

4. The design method for the free-loading, endurance-class solid rocket motor casing structure according to claim 2, characterized in that, Preliminary ply design includes the number, angle, and sequence of plies; The dimensions of the connection structure include the number of thread teeth, the width of the thread root, the working height of the thread, the inner diameter of the thread, and the pitch.

5. A method for preparing the free-loading, endurance-grade solid rocket motor casing structure as described in claim 1, characterized in that, Includes the following steps: Based on the internal shape of the engine housing structure, prepare a metal core mold and a metal filler sheet for the front end cap pole hole; Apply release agent to the core mold surface, attach the insulation layer, attach a metal filler sheet to the outside of the insulation layer at the pole hole position of the front end, and then cover the insulation layer surface with a plastic film. Carbon fiber and epoxy resin are wound onto a mandrel according to a certain pattern. After winding, the mandrel is cured and demolded to form a shell structure. The rear end cap is machined off the shell structure, and external threads are machined according to the connection design to obtain a combustion chamber shell containing the front end cap; The rear end cap is machined from metal and has internal threads machined. By connecting the external threads on the combustion chamber housing with the internal threads on the rear end cap, the free-loading, endurance-grade solid rocket motor housing structure is obtained. When carbon fiber-epoxy resin is wound onto a mandrel in a certain pattern, it includes: passing a continuous carbon fiber yarn bundle through an epoxy resin matrix and then winding it onto the mandrel. A sealing ring is installed at the connection between the combustion chamber shell and the rear end cap; The rear end cap is equipped with a nozzle and a heat insulation component.

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