A super-large flexible fairing buffer recovery system and a design method thereof

Abstract

This invention discloses an ultra-large flexible fairing buffer and recovery system. The system includes: an exhaust-type airbag, a closed-loop airbag, and a pressure closed-loop control system. The exhaust-type airbag includes an outer skin, an inner partition, an exhaust system, and an intake pipe. The exhaust-type airbag and the closed-loop airbag are stacked vertically and integrated into one unit. The design method involves first determining the initial design values ​​of the main parameters of the buffer and recovery system, then obtaining the corresponding curves after the fairing lands using analytical equations and finite element calculations, and optimizing the parameters. Finally, equivalent tests are conducted to verify the effectiveness of the system. The system and design method provided by this invention are applicable to low-stiffness composite material products, including ultra-large flexible fairings. They can provide optimization guidance for simulation analysis, effectively reduce the number of simulation calculations, shorten the design cycle, and reduce computational costs. This invention has strong versatility in aerospace product applications such as booster separation tests and interstage separation tests.

Description

Technical Field

[0001] This invention belongs to the field of spacecraft separation test technology, specifically relating to an ultra-large flexible fairing buffer recovery system and its design method. Background Technology

[0002] The fairing must separate safely and promptly during the later stages of a launch vehicle's flight to ensure rapid communication between the spacecraft and the ground control system, allowing for precise attitude adjustment and entry into orbit. The fairing's ability to withstand airflow loads and separate normally determines the success or failure of the launch mission. Therefore, to avoid anomalies during fairing separation, such as collisions between the fairing and the satellite or failure to detach properly from the rocket body, multiple ground separation system verification tests must be conducted during the fairing development phase. These tests verify the correctness of the separation system design, obtain the motion trajectory parameters of the separation structure system, and provide a basis for revising the separation calculation theoretical model. Currently, the fairings of new-generation medium-lift launch vehicles are mainly made of composite materials, with a structure of paper honeycomb + fiberglass panels, forming an ultra-large open flexible structure in the separated state. For such large-mass, low-stiffness products as ultra-large flexible fairings, the lack of effective load control during separation and landing can easily lead to uncontrollable dangerous behaviors such as excessive recovery overload or equipment rebound, resulting in product damage and significant economic losses. Therefore, a buffer recovery system design method is needed to safely recover the fairing during ground separation. Before performing computer simulation calculations on the buffer recovery system, this design method can determine certain initial parameter design values ​​through analytical equations, thereby providing optimization guidance for simulation analysis, reducing the number of simulation analysis calculations, shortening the design cycle, reducing computational costs, and simultaneously achieving the goal of safely recovering the test products. Summary of the Invention

[0003] The technical problem solved by this invention is to address the shortcomings of existing design methods for buffer recovery systems of large-mass, low-stiffness products such as ultra-large flexible fairings. This invention provides a recovery system and a corresponding design method. This system design method has the characteristics of wide applicability, fewer simulation analysis calculations, short design cycle, and low computational cost, meeting the needs of ensuring the safety of test products in the fields of boost separation test and interstage separation test.

[0004] To address the aforementioned technical problems, this invention discloses an ultra-large flexible fairing buffer and recovery system; The buffer recovery system includes an exhaust airbag, a closed airbag, and a pressure closed-loop control system. The venting airbag and the closed airbag are stacked on top of each other and combined into one unit. The venting airbag is used to dissipate the landing energy of the fairing, and the closed airbag is used to prevent the fairing from colliding with the ground after the air inside the venting airbag is emptied. The exhaust-type airbag includes an outer skin, an inner partition, an exhaust system, and an intake pipe; The inner partition wall divides the exhaust airbag into multiple air chambers, each air chamber being equipped with an exhaust system; The exhaust system is normally closed and is opened by the pressure closed-loop control system.

[0005] Furthermore, the exhaust system is arranged on the side of the exhaust-type buffer airbag, and the pressure closed-loop system is connected to an external pressure sensor. When the pressure inside the buffer airbag reaches the preset pressure, the exhaust system is controlled to keep the exhaust port open. The exhaust-type airbag is made of aramid fiber material, and the closed airbag is made of PVC material.

[0006] The design method for an ultra-large flexible fairing buffer and recovery system includes the following steps: S1. Determine the structural characteristics of the fairing and the dynamic parameters for landing after separation; S2. Use analytical equations to determine the initial design values ​​of the main parameters of the buffer recovery system; S3. Use finite element simulation software to verify the correctness of the initial design values ​​of the main parameters of the exhaust airbag calculated by the analytical equation, construct the finite element model of the buffer recovery system, calculate the corresponding curve after the fairing lands, evaluate the response curve, and optimize the design parameters. S4. Equivalent test to verify the effectiveness of the buffer reclamation system design parameters.

[0007] Furthermore, the initial design values ​​for the main parameters of the buffer recovery system include: the initial height of the vented airbag. h Initial exhaust pressure of exhaust-type airbag ∆P and the exhaust port area of ​​the exhaust-type airbag A out .

[0008] Furthermore, the initial height of the vented airbag h The steps for determining the initial design values ​​using analytical equations are as follows: S1, based on fairing mass M Pre-landing speed of the fairing V 1 Speed ​​after fairing landing V 2 Determine the change in kinetic energy of the fairing during landing. E k :

[0009] S2. Based on the permissible overload during fairing landing. N To determine if the fairing can withstand the reaction force of the airbags. F :

[0010] S3. Based on the fairing's ability to withstand the airbag's reaction force. F airbag cushioning stroke s Determine the power applied by the airbag to the fairing. W F :

[0011] S4. Based on the change in kinetic energy E during the fairing landing process. k fairing quality M Airbag cushioning stroke s Gravitational acceleration g n Airbag cushioning efficiency η To determine the energy change of the airbag during landing. ∆E :

[0012] S5. Based on the law of conservation of energy, a preset airbag cushioning safety factor is established. f That is, the work done by the airbag. W F Energy change with fairing ∆E Equal to determine the height of the airbag. h : Furthermore, the initial exhaust pressure of the exhaust-type airbag ∆P The method for determining the initial design values ​​using analytical equations is as follows: based on the allowable overload of the fairing. N fairing quality M The area of ​​the fairing that does not contact the airbag at the moment of landing A 1 The area of ​​the fairing in contact with the airbag surface at the moment of landing. A 2 Determine the initial deflation pressure of the airbag. ∆P : .

[0013] Furthermore, the exhaust port area of ​​the exhaust-type airbag A out The steps for determining the initial design values ​​using analytical equations are as follows: S1, based on the fairing landward speed V 1 Gas flow efficiency K e According to the fairing's permissible overload N Determine the airbag buffer time t :

[0014] S2. Based on the volume of airbags that need to be deflated during fairing landing. V Exhaust time t , gas density inside the cushioning airbag ρ Determine the mass flow rate of the airbag exhaust port. W :

[0015] S3, based on the gas adiabatic index k and the initial exhaust pressure of the buffer airbag. ∆P Specific volume of flowing gas under absolute pressure V j Determine the area of ​​the air intake of the buffer recovery airbag. A out :

[0016] S4. Based on the size of the airbag and the expected number of exhaust ports n Determine the area of ​​a single exhaust port. B out : .

[0017] Furthermore, the method for constructing a finite element model of the buffer recovery system, evaluating the response curve, and optimizing the design parameters includes: S1. Based on the initial parameter design values ​​of the exhaust airbag determined by the analytical method, construct a finite element model of the buffer recovery system, including the elastic modulus of the aramid fiber material, the thickness of the aramid fiber material, the inner wall of the fairing, and the composition and temperature of the gas filled into the buffer airbag. S2. Construct an equivalent finite element model of the fairing, including the fact that the fairing can be equivalent to three parts: an inverted cone, a cylindrical section, the von Kármán main body, and a frame truss structure. S3. Construct a contact analysis model, including the contact between the fairing and the buffer recovery system, and the contact process between the buffer recovery system and the ground; S4. Use the fixed step size method and the variable step size center difference method to obtain the acceleration response curves after the fairing lands, evaluate the effectiveness of the initial parameter design values, and optimize the parameters.

[0018] Furthermore, the method for the equivalent test includes: S1. Use equivalent simulation components to conduct drop tests to verify the airbag. The drop verification test includes two working conditions: energy consistency and kinetic energy consistency. S2. Based on energy consistency drop tests, the simulated component drop test energy is kept consistent with the actual fairing landing energy:

[0019] In the formula: E 1 For fairing landing energy, m 1 For fairing quality, c 1 For the fairing landing speed, m 2 To simulate the quality of the part, c 2 This simulates the drop speed of the component; S3. Based on kinetic energy drop tests, maintain consistency between the simulated component drop test kinetic energy and the actual fairing landing kinetic energy:

[0020] In the formula: E 2 To simulate the landing kinetic energy of the component, m 1 For fairing quality, c 1 For the fairing landing speed, m 2 To simulate the quality of the part, c 2 This is to simulate the drop speed of the component.

[0021] Furthermore, the verification of the effectiveness includes obtaining the acceleration response curve of the simulated component during the experiment and comparing it with the finite element simulation calculation to verify the credibility of the finite element simulation calculation.

[0022] The present invention has the following advantages: (1) The buffer recovery system proposed in this invention can safely recover weak stiffness composite material products, and is suitable for ground separation tests of large fairings, thereby improving the quality of test implementation; (2) Before performing computer simulation calculations on the buffer recovery system, the design method of the present invention can determine the design values ​​of certain initial parameters by means of analytical equations, thereby providing optimization guidance for simulation analysis, reducing the number of simulation analysis calculations, and achieving the effect of shortening the design cycle and reducing the calculation cost; (3) The design method of this invention can be applied to ground separation tests of aerospace products such as boost separation test and interstage separation test, and has strong versatility. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. It should be noted that, for clarity and ease of explanation, the drawings are not necessarily drawn to scale.

[0024] Figure 1 This is a schematic diagram of the ultra-large flexible fairing buffer recovery system of the present invention; Figure 2 This is a schematic diagram of the stress-displacement curve of the exhaust airbag material of the present invention; Figure 3 This is a schematic diagram of the finite element model of the buffer recovery system of the present invention; Figure 4 This is a schematic diagram of the finite element model of the exhaust airbag, airbag material, inner partition wall, and exhaust system of the present invention. Figure 5 This is a schematic diagram of the equivalent parameters of the fairing equivalent finite element model of the present invention; Figure 6 This is a schematic diagram of the contact analysis model of the buffer recovery system of the present invention with the fairing and the ground. Figure 7 This is a schematic diagram of the acceleration response curve of the fairing after landing obtained by the fixed step size method of the present invention; Figure 8 This is a schematic diagram illustrating the verification of the cushioning airbag using a drop test of the equivalent simulation component of the present invention. The diagram shows: 1-pressure closed-loop control system, 2-closed airbag, 3-exhaust airbag, 4-exhaust system.

[0025] The invention will now be further described with reference to the accompanying drawings.

[0026] In this embodiment, the overall structure of the ultra-large flexible fairing buffer recovery system is as follows: Figure 1 As shown, it includes a pressure closed-loop control system 1, a closed airbag 2, an exhaust airbag 3, and an exhaust system 4; The venting airbag 3 and the closed airbag 2 are stacked on top of each other to form a whole. The venting airbag 3 is used to dissipate the landing energy of the fairing, and the closed airbag 2 is used to prevent the fairing from colliding with the ground after the air inside the venting airbag 3 is emptied. The exhaust-type airbag 3 includes an outer skin, an inner partition, an exhaust system 4, and an intake pipe; The inner partition wall divides the exhaust airbag 3 into multiple air chambers, and each air chamber is equipped with an exhaust system 4. The exhaust system 4 is normally closed, and is opened by the pressure closed-loop control system 1. The exhaust system 4 is arranged on the side of the exhaust-type buffer airbag. The pressure closed-loop system is connected to an external pressure sensor. When the pressure inside the buffer airbag reaches the preset pressure, the exhaust system 4 is controlled to keep the exhaust port open. The exhaust-type airbag 3 is made of aramid fiber material, and the closed airbag 2 is made of PVC material.

[0027] For the selected fairing model, the structural characteristics of the fairing and the dynamic parameters of the landing after separation are obtained. The initial design values ​​of the main parameters of the exhaust airbag 3 are determined using analytical equations. These initial design values ​​include the initial height h of the exhaust airbag 3, the initial exhaust pressure ∆P of the exhaust airbag 3, and the exhaust port area A of the airbag. out design: Preferably, based on the mass M of a certain type of fairing ( 1500kg ), Fairing landing speed V 1= 10m / s Speed ​​after fairing landing V 2= 1m / s Determine the change in kinetic energy of the fairing during landing. E k ：

[0028] Based on the permissible overload during fairing landing. N To determine if the fairing can withstand the reaction force of the airbags. F In the formula, N= η=60%, g=9.81m / s 2 The reaction force of the airbag can be obtained: =52974N Based on the fairing's ability to withstand the airbag's reaction force F airbag cushioning stroke s Determine the power applied by the airbag to the fairing. W F :

[0029] Based on the change in kinetic energy during the fairing landing process E k、 fairing quality M Airbag cushioning stroke s Gravitational acceleration g n Airbag cushioning efficiency ηTo determine the energy change of the airbag during landing. :

[0030] Based on the law of conservation of energy, a preset airbag cushioning safety factor is established. f That is, the work done by the airbag. W F Energy change with fairing Equal to determine the height of the airbag. h : =2.1m Preferably, the initial design values ​​of the main parameters of the vented airbag 3, including the initial venting pressure of the airbag, are determined using the analytical equation method. design: Based on the fairing's allowable reduction ratio (10) and fairing mass... (1500kg), the area of ​​the fairing that does not contact the airbag at the moment of landing. A 1 (70m) 2 The area of ​​the fairing in contact with the airbag surface at the moment of landing. A 2 (5m) 2 Determine the initial deflation pressure of the airbag. : =4800Pa Preferably, the initial design values ​​of the main parameters of the exhaust airbag 3, including the airbag exhaust port area, are determined using the analytical equation method. design: Based on the fairing landward speed V 1 Gas flow efficiency K e According to the fairing's permissible overload N Determine the airbag buffer time t : =0.4s Based on the volume of airbags that need to be deflated during fairing landing. V Exhaust time t , gas density inside the cushioning airbag ρ Determine the mass flow rate of the airbag exhaust port. W :

[0031] According to the gas adiabatic index k , initial deflation pressure of the buffer airbag Specific volume of flowing gas under absolute pressure V jDetermine the area of ​​the air intake of the buffer recovery airbag. : =1620532mm 2 Based on the size of the airbag and the expected number of exhaust ports n (12), determine the area of ​​a single exhaust port. : =108631mm 2 like Figure 2 The stress-displacement curve of the material of the vented airbag 3 is shown in the schematic diagram. The correctness of the initial design values ​​of the main parameters of the vented airbag 3 calculated by the analytical equation is verified by finite element simulation software. Preferably, by conducting tensile tests on Kevlar fiber materials of different thicknesses, data characterizing the stiffness of Kevlar materials of different thicknesses can be approximately obtained, providing parameters for subsequent experimental simulation and predictive research.

[0032] like Figure 3 Schematic diagram of the finite element model of the buffer recovery system and Figure 4 The finite element model of the exhaust airbag 3, airbag material, inner partition wall, and exhaust system 4 is shown in the figure. Based on the initial parameter design values ​​of the exhaust airbag determined by the analytical method, the finite element model of the buffer recovery system is constructed, including the elastic modulus of Kevlar fiber material, the thickness of Kevlar fiber material, the inner partition wall of the fairing, the gas composition and temperature of the gas filled into the buffer airbag.

[0033] like Figure 5 The equivalent parameters of the fairing equivalent finite element model are shown in the schematic diagram. The equivalent finite element model of the fairing is constructed, including the fairing being equivalent to three parts: an inverted cone, a cylindrical section, and the von Kármán main body and frame truss structure.

[0034] like Figure 6 Schematic diagram of the contact analysis model of the buffer recovery system in contact with the fairing and ground. Figure 7 The fixed-step method was used to obtain the acceleration response curve of the fairing after landing. As shown in the schematic diagram, a contact analysis model was constructed, including the contact between the fairing and the buffer recovery system, and the contact process between the buffer recovery system and the ground. Preferably, the acceleration response curves after fairing landing are obtained using the fixed step size method and the variable step size center difference method to evaluate the effectiveness of the initial parameter design values ​​and optimize the parameters.

[0035] like Figure 8 The equivalent simulation drop test is shown in the schematic diagram for verifying the cushioning airbag. After the initial parameter design values ​​are verified to be valid by finite element simulation, the equivalent test is carried out. The equivalent test method is as follows: The airbag was validated by drop tests using an equivalent simulation component. The drop validation tests included two conditions: one based on energy consistency and the other based on kinetic energy consistency. Based on consistent energy drop tests, the simulated fairing drop tests maintain the same landing energy as the actual fairing:

[0036] In the formula: E 1 For fairing landing energy, m 1 For fairing quality, c 1 For the fairing landing speed, m 2 To simulate the quality of the part, c 2 This simulates the drop speed of the component; S3. Based on kinetic energy drop tests, maintain consistency between the simulated component drop test kinetic energy and the actual fairing landing kinetic energy:

[0037] In the formula: E 2 To simulate the landing kinetic energy of the component, m 1 For fairing quality, c 1 For the fairing landing speed, m 2 To simulate the quality of the part, c 2 This is to simulate the drop speed of the component.

[0038] Preferably, the acceleration response curve of the simulated component is obtained during the equivalent test and compared with the finite element simulation calculation to verify the credibility of the finite element simulation calculation.

[0039] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make possible variations and modifications to the technical solutions of the present invention using the disclosed methods and techniques without departing from the spirit and scope of the invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, are all within the protection scope of the present invention. Content not described in detail in this specification is common knowledge to those skilled in the art.

Claims

1. A super-large flexible fairing buffer and recovery system, characterized in that: The buffer recovery system includes a vented airbag, a closed airbag, and a pressure closed-loop control system, wherein: The venting airbag and the closed airbag are stacked on top of each other and combined into one unit. The venting airbag is used to dissipate the landing energy of the fairing, and the closed airbag is used to prevent the fairing from colliding with the ground after the air inside the venting airbag is emptied. The exhaust-type airbag includes an outer skin, an inner partition, an exhaust system, and an intake pipe; The inner partition wall divides the exhaust airbag into multiple air chambers, each air chamber being equipped with an exhaust system; The exhaust system is normally closed and is opened by the pressure closed-loop control system.

2. The ultra-large flexible fairing buffer and recovery system as described in claim 1, characterized in that: The exhaust system is located on the side of the exhaust-type buffer airbag. The pressure closed-loop system is connected to an external pressure sensor. When the pressure inside the buffer airbag reaches the preset pressure, the exhaust system is controlled to keep the exhaust port open. The exhaust-type airbag is made of aramid fiber material, and the closed airbag is made of PVC material.

3. A design method for an ultra-large flexible fairing buffer and recovery system, applied to the ultra-large flexible fairing buffer and recovery system as described in claim 1 or 2, characterized in that, The method includes the following steps: S1. Determine the structural characteristics of the fairing and the dynamic parameters for landing after separation; S2. Use analytical equations to determine the initial design values ​​of the main parameters of the buffer recovery system; S3. Use finite element simulation software to verify the correctness of the initial design values ​​of the main parameters of the exhaust airbag calculated by the analytical equation, construct the finite element model of the buffer recovery system, calculate the corresponding curve after the fairing lands, evaluate the response curve, and optimize the design parameters. S4. Equivalent test to verify the effectiveness of the buffer reclamation system design parameters.

4. The design method of an ultra-large flexible fairing buffer recovery system as described in claim 3, characterized in that, The initial design values ​​of the main parameters of the buffer recovery system include: the initial height h of the vented airbag, the initial exhaust pressure ∆P of the vented airbag, and the exhaust port area A of the vented airbag. out .

5. The design method of an ultra-large flexible fairing buffer recovery system as described in claim 4, characterized in that, The steps for determining the initial design value h of the exhaust-type airbag using the analytical equation method are as follows: S1. Based on the fairing mass M, the fairing velocity V1 before landing, and the fairing velocity V2 after landing, determine the change in kinetic energy E of the fairing upon landing. k : S2. Based on the permissible overload N during fairing landing, determine the reaction force F that the fairing can withstand from the airbags: S3. Based on the reaction force F that the fairing can withstand from the airbag and the buffer stroke s of the airbag, determine the work W applied by the airbag to the fairing. F : S4. Based on the change in kinetic energy E during the fairing landing process. k , fairing mass M, airbag cushioning stroke s, gravitational acceleration g n η is the airbag buffer efficiency, which determines the change in airbag energy ∆E during landing. S5. Based on the law of conservation of energy, a preset airbag cushioning safety factor f is established, which is the work W done by the airbag. F The height h of the buffer airbag is determined to be equal to the energy change ∆E of the fairing: 。 6. The design method of an ultra-large flexible fairing buffer recovery system as described in claim 4, characterized in that: The method for determining the initial design value of the exhaust pressure ∆P of the exhaust-type airbag using analytical equations is as follows: Based on the allowable overload N of the fairing, the mass M of the fairing, the area A1 of the fairing that does not contact the airbag at the moment of landing, and the area A2 of the fairing that contacts the airbag surface at the moment of landing, the initial exhaust pressure ∆P of the buffer airbag is determined. 。 7. A design method for an ultra-large flexible fairing buffer recovery system as described in claim 4, characterized in that, The exhaust port area A of the exhaust-type airbag out The steps for determining the initial design values ​​using analytical equations are as follows: S1, based on the fairing landward velocity V1 and gas flow efficiency K e Based on the fairing's allowable overload N, determine the airbag buffer time t: ； S2. Based on the volume V that the airbag needs to vent during fairing landing, the venting time t, and the gas density ρ inside the airbag, determine the mass flow rate W of the airbag vent: ； S3. Based on the gas adiabatic index k, the initial exhaust pressure ∆P of the buffer airbag, and the specific volume V of the flowing gas under absolute pressure. j Determine the area A of the air vent of the buffer recovery airbag. out : ； S4. Based on the size of the airbag and the expected number of exhaust ports n, determine the area B of a single exhaust port. out : 。 8. A design method for an ultra-large flexible fairing buffer recovery system as described in claim 3, characterized in that, The method for constructing a finite element model of the buffer recovery system, evaluating the response curve, and optimizing the design parameters includes: S1. Based on the initial parameter design values ​​of the exhaust airbag determined by the analytical method, construct a finite element model of the buffer recovery system, including the elastic modulus of the aramid fiber material, the thickness of the aramid fiber material, the inner wall of the fairing, and the composition and temperature of the gas filled into the buffer airbag. S2. Construct an equivalent finite element model of the fairing, including the fact that the fairing can be equivalent to three parts: an inverted cone, a cylindrical section, the von Kármán main body, and a frame truss structure. S3. Construct a contact analysis model, including the contact between the fairing and the buffer recovery system, and the contact process between the buffer recovery system and the ground; S4. Use the fixed step size method and the variable step size center difference method to obtain the acceleration response curves after the fairing lands, evaluate the effectiveness of the initial parameter design values, and optimize the parameters.

9. A design method for an ultra-large flexible fairing buffer recovery system as described in claim 3, characterized in that, The method for the equivalent test includes: S1. Use equivalent simulation components to conduct drop tests to verify the airbag. The drop verification test includes two working conditions: energy consistency and kinetic energy consistency. S2. Based on energy consistency drop tests, the simulated component drop test energy is kept consistent with the actual fairing landing energy: ； In the formula: E1 is the fairing landing energy, m1 is the fairing mass, c1 is the fairing landing velocity, m2 is the simulated component mass, and c2 is the simulated component drop velocity; S3. Based on kinetic energy drop tests, maintain consistency between the simulated component drop test kinetic energy and the actual fairing landing kinetic energy: ； In the formula: E2 is the landing kinetic energy of the simulated component, m1 is the mass of the fairing, c1 is the landing velocity of the fairing, m2 is the mass of the simulated component, and c2 is the drop velocity of the simulated component.

10. A design method for an ultra-large flexible fairing buffer recovery system as described in claim 3, characterized in that: The validity verification includes obtaining the acceleration response curve of the simulated component during the test and comparing it with the finite element simulation calculation to verify the credibility of the finite element simulation calculation.

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