Method for calculating landing impact load of launch vehicle

Abstract

The application provides a launch vehicle landing impact load calculation method, comprising the following steps: obtaining design parameters of a landing buffer device assembly; obtaining parameters required for landing impact load calculation; based on the design parameters and the calculation required parameters, establishing a finite element simulation analysis model of the landing impact load, wherein an elastic-plastic spring-damping unit of the finite element simulation analysis model is used to simulate mechanical parameters of the buffer; using a dynamic analysis method to simulate and calculate a landing impact process of the finite element simulation analysis model; extracting time histories of axial force loads and bending moment loads of each component of the landing buffer device in the simulation calculation result, and determining the landing impact load of the landing buffer device. The application establishes a combined finite element model of a rocket body and a landing buffer device, and provides reliable basis for optimization design and strength verification of the buffer device and related structures of the rocket body.

Description

Technical Field

[0001] This invention belongs to the field of launch vehicle technology, and in particular relates to a method for calculating the landing impact load of a launch vehicle. Background Technology

[0002] In the aerospace field, such as in the development of rockets for commercial spaceflight, landing buffer systems are crucial for the successful recovery of launch vehicles. During the rocket's ascent phase, they adhere closely to the rocket body surface and are housed within the fairing to reduce aerodynamic drag. During recovery, they deploy and lock via a drive mechanism, absorbing the landing impact load and cushioning energy to ensure the rocket structure and landing buffer system are not damaged, allowing for reuse in subsequent launch missions. The landing impact load is a design input for the landing buffer system and the tail section of the rocket structure, playing a vital role in the reusability of rockets in reusable rocket technology.

[0003] There are two main existing methods for calculating landing impact loads: 1) Based on design experience, the landing impact overload is given, and then the landing impact load on each component is calculated through geometric relationships. 2) The rocket body and landing buffer device are simplified into a simulation model composed of rigid bodies and buffer units, and the load on each component is calculated through kinematic and dynamic analysis.

[0004] In implementing this embodiment, the inventors discovered the following problems with existing methods: 1) They rely on design experience, lack theoretical calculations and simulation analysis, and their accuracy cannot be verified; 2) The rocket body and landing buffer device are usually simplified as rigid bodies, and only axial force load is considered; 3) The main loads of the landing buffer device include axial force and bending moment, and bending moment has a greater impact on the strength assessment of the landing buffer device. Reasonable bending moment load is the key to designing the landing buffer device. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides a method for calculating the landing impact load of a launch vehicle.

[0006] This disclosure provides a method for calculating the landing impact load of a launch vehicle, including: Obtain the design parameters of the landing buffer device components, which include main outriggers, auxiliary outriggers, and buffers. The design parameters include the geometric parameters of each component, the material properties of each component, the connection relationships between each component, and the types of kinematic pairs between each component. Obtain the parameters required for calculating the landing impact load. These parameters include the mass characteristics of the rocket body at the moment of landing, kinematic parameters, the coefficient of friction between the footpads of the auxiliary legs and the ground, and the mechanical properties of the ground material. Based on the design parameters and the parameters required for calculation, a finite element simulation analysis model of the landing impact load is established, in which the elastoplastic spring-damping element of the finite element simulation analysis model is used to simulate the mechanical parameters of the buffer. The landing impact process of the finite element simulation analysis model was simulated and calculated using dynamic analysis methods. Extract the time histories of axial force and bending moment loads of each component of the landing buffer device from the simulation calculation results to determine the landing impact load of the landing buffer device.

[0007] Optionally, the establishment of a finite element simulation analysis model for landing impact load based on design parameters and required calculation parameters includes: The rocket body structure is simulated as a rigid body, and the main and auxiliary support leg structural components in the landing buffer device are simulated as flexible units. The connection and contact relationships between the components are established.

[0008] Optionally, the flexible unit is a beam unit or a shell unit.

[0009] Optionally, the buffer includes at least one of a compressible energy-absorbing buffer, an oil buffer, a pneumatic buffer, a mechanical spring buffer, and an electromagnetic damping buffer.

[0010] Optionally, the main support leg includes a retractable multi-stage sleeve structure and an internal locking mechanism, wherein each two stages of the multi-stage sleeve structure can move axially to enable the deployment and retraction of the landing buffer device. When the sleeve moves to the travel position, the multi-stage sleeve structure is locked by the internal locking mechanism.

[0011] Optionally, the secondary support leg includes a strut, a skin, and a foot pad; the foot pad is located at the bottom of the strut, and the skin wraps around the outside of the strut.

[0012] Optionally, the mass characteristics of the rocket body at the moment of landing include mass, center of mass position, and moment of inertia about the center of mass; the kinematic parameters include the velocity vector, angular velocity vector, and attitude angle of the center of mass.

[0013] Optionally, the mechanical parameters of the buffer include stroke, elastic properties, crush force curve, and damping characteristics.

[0014] Optionally, the connection relationship includes the connection structure between the main support leg and the rocket body, the connection structure between the main support leg and the auxiliary support leg, and the connection structure between the auxiliary support leg and the rocket body. The connection relationship is simulated using a hinge kinematic pair.

[0015] Optionally, the dynamic analysis method is an explicit dynamic algorithm or an implicit dynamic algorithm.

[0016] The method for calculating the landing impact load of a launch vehicle provided by this invention establishes a finite element model of the combined rocket body and landing buffer device, simulates the characteristics of the buffer using spring-damping elements, and performs calculations using finite element simulation analysis software. This overcomes the limitation of traditional methods that only consider axial forces, thereby enabling accurate calculation of the impact loads of each component of the landing buffer device (including bending moments). This provides a reliable basis for the optimized design and strength verification of the buffer device and related structures of the rocket body. Attached Figure Description

[0017] The above and other objects, features and advantages of this disclosure will become more apparent from the accompanying drawings, in which like reference numerals generally denote like parts.

[0018] Figure 1 This is a schematic diagram of the landing buffer device provided in an embodiment of the present disclosure; Figure 2 A schematic diagram of the finite element model of the landing buffer device and the rocket body structure provided in the embodiments of this disclosure; Figure 3 A schematic diagram of the landing impact load-time history provided for embodiments of this disclosure; Figure 4 This is a schematic diagram of the interface for setting the initial velocity and angular velocity parameters of the rocket body according to an embodiment of the present disclosure; Figure 5 This is a schematic diagram of the display dynamics calculation parameters and output settings interface provided in an embodiment of this disclosure. Detailed Implementation

[0019] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0020] It should be understood that the following specific examples illustrate the implementation of this disclosure, and those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0021] It should be noted that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice method. Furthermore, this device and / or practice method can be implemented using other structures and / or functionalities besides one or more of the aspects set forth herein.

[0022] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this disclosure. The illustrations only show the components related to this disclosure and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0023] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0024] This embodiment discloses a method for calculating the landing impact load of a launch vehicle, including: Step S101: Obtain the design parameters of the landing buffer device components, wherein the components include main outriggers, auxiliary outriggers and buffers, and the design parameters include the geometric parameters of each component, the material properties of each component, the connection relationship between each component and the type of kinematic pair between each component.

[0025] Specifically, the design parameters include the number of stages of the main outrigger multi-stage sleeve, the length, cross-sectional shape and material properties of each stage sleeve; the geometric model and material properties of the secondary outrigger; and the stroke, crushing force and damping characteristics of the buffer (depending on the type of buffer).

[0026] Step S102: Obtain the parameters required for calculating the landing impact load. The parameters required for calculation include the mass characteristics of the rocket body at the moment of landing, kinematic parameters, the friction coefficient between the footpads of the auxiliary legs and the ground, and the mechanical properties of the ground material; the friction coefficient is the sliding friction coefficient.

[0027] Specifically, the parameters required for calculating the landing impact load include the rocket's center of mass, mass, and moment of inertia at the moment of landing; and the velocity vector, angular velocity vector, and attitude angle at the moment of landing. The moment of inertia is the moment of inertia about the center of mass. The positions corresponding to the velocity vector and angular velocity vector are the center of mass.

[0028] Step S103: Based on the design parameters and the parameters required for calculation, establish a finite element simulation analysis model of the landing impact load, wherein the mechanical parameters of the buffer are simulated using the elastoplastic spring-damping element of the finite element simulation analysis model.

[0029] A landing impact load calculation model was established using finite element simulation software. The rocket body structure can be simulated using rigid bodies, while other structural components in the landing buffer device can be simulated using flexible elements such as beam elements or shell elements.

[0030] During the calculation process, it is necessary to accurately simulate the geometric features, mechanical properties, and mass characteristics of each component, as well as the connection and contact relationships between the components. The mechanical parameters of the buffer are simulated using elasto-plastic spring-damping elements in the finite element simulation analysis model, including stroke, elastic performance, crushing force curve, and damping characteristics. An elasto-plastic spring-damping element refers to a type of connection element in finite element simulation analysis software, such as the Busing element in Abaqus software. The simulation of key design parameters of the buffer can be achieved by adding and modifying the properties of the elements.

[0031] Step S104: Use dynamic analysis method to simulate the landing impact process of the finite element simulation analysis model; that is, use dynamic analysis method to simulate the landing impact process and output the calculation results such as nodal forces.

[0032] Step S105: Extract the time history of the axial force load and bending moment load of each component of the landing buffer device from the simulation calculation results, and determine the landing impact load of the landing buffer device.

[0033] Specifically, the axial force / bending moment load-time history of each component is extracted in the post-processing analysis module to determine the landing impact load of each component.

[0034] Landing buffer devices such as Figure 1 As shown, it includes the arrow body 1, main support leg, secondary support leg 5, buffer 6, connection structure 8 between the main support leg and the arrow body, connection structure 9 between the main support leg and the secondary support leg, and connection structure 10 between the secondary support leg and the arrow body; the main support leg includes the first main support leg 2, the second main support leg 3, and the third main support leg 4.

[0035] The main outrigger consists of a retractable multi-stage sleeve structure and an internal locking mechanism. Each pair of sleeves can move axially, enabling the deployment and retraction of the landing buffer device. The internal locking mechanism locks the multi-stage sleeve structure in place when the sleeve reaches its travel position. The secondary outrigger 5 includes a strut, a skin, and foot pads 7. The foot pads 7 are located at the bottom of the strut, and the skin covers the outside of the strut. The secondary outrigger serves to cover the landing buffer device to form a better aerodynamic shape when retracted, and to assist in supporting the rocket body structure when deployed.

[0036] For example, a buffer may include compressible energy-absorbing buffers, oil buffers, pneumatic buffers, mechanical spring buffers, electromagnetic damping buffers, and other devices used to buffer and absorb energy during landing impacts.

[0037] The connection relationship is simulated using hinge kinematic pairs. The dynamic analysis method can be either an explicit dynamic algorithm or an implicit dynamic algorithm.

[0038] The design of the landing buffer device in this embodiment is not limited to... Figure 1 The inverted triangle-shaped retractable landing legs can be designed as fixed or retractable, and can include one or more buffers; there are no restrictions on the installation location of the buffers. The simulation of the landing buffer structure is not limited by the element type; any suitable finite element type can be used as needed.

[0039] In a specific application scenario, the calculation method for the landing impact load of a launch vehicle includes: This embodiment uses an inverted triangular deployable landing buffer device as an example for illustration. The design scheme of the landing buffer device is determined. The main outrigger consists of three-stage sleeves, and the auxiliary outrigger consists of two struts and a fairing skin. The cross-sectional shape, length and material of each stage of the sleeves of the main and auxiliary outriggers are shown in Table 1 below.

[0040] Table 1. Cross-sectional shape, length, and material dimensions of the sleeves for each stage of the main and auxiliary outriggers. In this embodiment, the buffer type is a multi-stage cellular buffer. The key design parameters for each stage of the buffer are determined, including stiffness, stroke, and crushing force, as shown in Table 2.

[0041] Table 2. Buffer Design Parameters The parameters required for dynamic simulation analysis of the landing impact process are determined, including the rocket's mass, center of mass position, moment of inertia, velocity vector, angular velocity vector, attitude angle, friction coefficient between the landing pad and the ground, and the types of kinematic pairs between various components at the moment of landing impact. The rocket's mass characteristics are shown in Table 3.

[0042] Table 3. Rocket Body Mass Characteristics The kinematic parameters of the rocket's center of mass during landing are shown in Table 4. The coefficient of friction between the footpads and the ground is taken as 0.4. The main and auxiliary legs are connected to the rocket body by bearings, and the kinematic pair type is hinge.

[0043] Table 4. Kinematic parameters of the arrow's center of mass Based on the above design parameters, a finite element simulation analysis model is established, such as... Figure 2 As shown. Input the kinematic parameters for the initial calculation step into the load module, such as... Figure 4 As shown. An explicit dynamics method is used for calculation, with settings for calculation duration, stable iteration step size, and output result type, such as... Figure 5 As shown. Then submit the calculation.

[0044] After the calculation is completed, the axial force / bending moment-time history curves of each component are obtained using the post-processing module, such as... Figure 3 As shown, the envelope load or a reasonable combination of cross-sectional loads is selected for the structural design, strength evaluation, and experimental verification of the landing buffer device.

[0045] This embodiment establishes a combined finite element model of the rocket body and landing buffer device, uses spring-damping elements to simulate the characteristics of the buffer, and performs calculations using finite element simulation analysis software, thus solving the problem that existing technologies cannot consider the bending moment load of the landing buffer device.

[0046] The basic principles of this disclosure have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this disclosure are merely examples and not limitations, and should not be considered as essential features of each embodiment of this disclosure. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the scope of this disclosure to the necessity of employing the aforementioned specific details for implementation.

[0047] In this disclosure, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The block diagrams of devices, apparatuses, devices, and systems involved in this disclosure are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as "comprising," "including," "having," etc., are open-ended terms meaning "including but not limited to," and are used interchangeably with them. The terms "or" and "and" as used herein refer to the terms "and / or," and are used interchangeably with them unless the context clearly indicates otherwise. The term "such as" as used herein refers to the phrase "such as but not limited to," and is used interchangeably with it.

[0048] Additionally, as used herein, the "or" used in a list of items beginning with "at least one" indicates a separate list, such that a list of, for example, "at least one of A, B, or C" means A or B or C, or AB or AC or BC, or ABC (i.e., A and B and C). Furthermore, the word "exemplary" does not imply that the described example is preferred or better than other examples.

[0049] It should also be noted that in the systems and methods of this disclosure, the components or steps can be decomposed and / or recombined. These decompositions and / or recombinations should be considered as equivalent solutions to this disclosure.

[0050] Various changes, substitutions, and modifications can be made to the techniques described herein without departing from the teachings defined in this embodiment. Furthermore, the scope of this embodiment is not limited to the specific aspects of the processes, machines, manufacturing processes, events, means, methods, and actions described above. Currently existing or later-developed processes, machines, manufacturing processes, events, means, methods, or actions that perform substantially the same function or achieve substantially the same result as the corresponding aspects described herein can be utilized. Therefore, this embodiment includes such processes, machines, manufacturing processes, events, means, methods, or actions within its scope.

[0051] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0052] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this disclosure to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A method for calculating the landing impact load of a launch vehicle, characterized in that, include: Obtain the design parameters of the landing buffer device components, which include main outriggers, auxiliary outriggers, and buffers. The design parameters include the geometric parameters of each component, the material properties of each component, the connection relationships between each component, and the types of kinematic pairs between each component. Obtain the parameters required for calculating the landing impact load. These parameters include the mass characteristics of the rocket body at the moment of landing, kinematic parameters, the coefficient of friction between the footpads of the auxiliary legs and the ground, and the mechanical properties of the ground material. Based on the design parameters and the parameters required for calculation, a finite element simulation analysis model of the landing impact load is established, in which the elastoplastic spring-damping element of the finite element simulation analysis model is used to simulate the mechanical parameters of the buffer. The landing impact process of the finite element simulation analysis model was simulated and calculated using dynamic analysis methods. Extract the time histories of axial force and bending moment loads of each component of the landing buffer device from the simulation calculation results to determine the landing impact load of the landing buffer device.

2. The method for calculating the landing impact load of a launch vehicle according to claim 1, characterized in that, The finite element simulation analysis model for landing impact load, based on design parameters and required calculation parameters, includes: The rocket body structure is simulated as a rigid body, and the main and auxiliary support leg structures in the landing buffer device are simulated as flexible units. The connection and contact relationships between the components are established.

3. The method for calculating the landing impact load of a launch vehicle according to claim 2, characterized in that, The flexible unit is a beam unit or a shell unit.

4. The method for calculating the landing impact load of a launch vehicle according to claim 1, characterized in that, The buffer includes at least one of a compressible energy-absorbing buffer, an oil buffer, a pneumatic buffer, a mechanical spring buffer, and an electromagnetic damping buffer.

5. The method for calculating the landing impact load of a launch vehicle according to claim 1, characterized in that, The main support leg includes a retractable multi-stage sleeve structure and an internal locking mechanism. In the multi-stage sleeve structure, each two sleeves can move axially to enable the deployment and retraction of the landing buffer device. When the sleeves move to the travel position, the internal locking mechanism locks the multi-stage sleeve structure.

6. The method for calculating the landing impact load of a launch vehicle according to claim 1, characterized in that, The secondary support leg includes a strut, a skin, and a foot pad; the foot pad is located at the bottom of the strut, and the skin covers the outside of the strut.

7. The method for calculating the landing impact load of a launch vehicle according to claim 1, characterized in that, The mass characteristics of the rocket body at the moment of landing include its mass, center of mass position, and moment of inertia about the center of mass; the kinematic parameters include the velocity vector, angular velocity vector, and attitude angle of the center of mass.

8. The method for calculating the landing impact load of a launch vehicle according to claim 1, characterized in that, The mechanical parameters of the buffer include stroke, elastic properties, crush force curve, and damping characteristics.

9. The method for calculating the landing impact load of a launch vehicle according to claim 1, characterized in that, The connection relationships include the connection structure between the main support leg and the rocket body, the connection structure between the main support leg and the auxiliary support leg, and the connection structure between the auxiliary support leg and the rocket body. The connection relationships are simulated using hinge kinematic pairs.

10. The method for calculating the landing impact load of a launch vehicle according to claim 1, characterized in that, The dynamic analysis method is either an explicit dynamic algorithm or an implicit dynamic algorithm.

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