A method for optimizing a multi-layer space shielding material based on uniform design

Abstract

Step 1: Determine radiation shielding parameters; Step 2: Analyze and determine radiation shielding materials; Step 3: Determine space radiation environment; Step 4: Geometric design and material result analysis; Step 5: Optimization of multilayer shielding materials based on uniform design; Step 6: Simulation result analysis; Step 7: Comparative analysis and verification. It uses particle transport analysis to study multilayer space shielding materials, analyzes the process itself, analyzes the failure mode, impact and hazard, and finds the key control parameters that affect the radiation shielding performance in the optimization design of multilayer shielding materials. Experimental design of key parameters is carried out through uniform design to determine the optimal design of key parameters. With the help of particle transport software MCNP6, the obtained key factors are simulated and analyzed to obtain the dose equivalent distribution of multilayer materials under different thicknesses, and the simulation model is verified and corrected by FLUKA code. Finally, the multilayer space radiation shielding materials are summarized in combination with the optimization model, so as to provide a theoretical basis for the optimization of multilayer material shielding of spacecraft.

Description

(1) Technical Field:

[0001] The present invention relates to a method for optimizing a multi-layer space shielding material based on uniform design. It uses particle transport analysis to conduct research on multi-layer space shielding materials. Starting from the shielding material itself, it analyzes the key shielding parameters such as shielding performance and dose equivalent, and finds the key control parameters that affect the radiation shielding performance in the optimization design process of multi-layer shielding materials. Through uniform design, the experimental design of key parameters is carried out to determine the optimized design of key parameters. With the help of the particle transport software MCNP6, the obtained key factors are simulated and analyzed to obtain the dose equivalent distribution of multi-layer materials under different thicknesses, and the simulation model is compared and verified through the FLUKA code. Finally, the multi-layer space radiation shielding material is summarized in combination with the optimization model, and the visualization result of the multi-layer radiation shielding material is given, so as to provide a theoretical basis for the optimization of the multi-layer material shielding of spacecraft. (2) Background Art:

[0002] Space radiation effectively damages humans and electronic devices. Solar particle events (SPEs), galactic cosmic radiation (GCR), and the Van Allen radiation belts are the main types of space radiation. Shielding can reduce the overall exposure of personnel and electrical equipment. One of the strategies being studied to help reduce the harm caused by radiation exposure to the human body and electrical equipment is radiation shielding. The radiation hazards in space increase with protons and high atomic number, high-Z and E particles (HZE). Elements with the highest charge-to-mass ratio are the best shielding materials against HZE particles. Neutrons, gamma rays, and X-rays generated by particle collisions increase the radiation hazard. Research on space shielding methods must be carried out to improve the reliability of system radiation exposure.

[0003] Over the years, a large number of radiation dose estimation studies have been conducted for manned and unmanned space missions. The initial research on radiation shielding used radiation transport codes to determine the amount and type of radiation transmitted through the shield at different depths and material properties. However, there is little research on multi-layer shielding materials, which are substances that shield radiation exposure by using multiple different Z values (atomic numbers). This brings new optimization technologies for the next generation of deep space vehicles and space stations. Currently, the research on the radiation shielding of the walls of space vehicles is more limited to aluminum material shielding. Secondly, the research on multi-layer composite materials of aluminum - polyethylene - aluminum is in the laboratory stage, and the optimized design of multi-layer radiation shielding materials is an emerging research hotspot.

[0004] Therefore, this method takes multi-layer radiation shielding materials as the research object, aiming at the problems of insufficient multi-layer design of current multi-layer space radiation shielding materials and lack of innovation in existing optimization methods. A method for optimizing multi-layer space shielding materials based on uniform design is designed and established. First, by analyzing the space particle environment, the particle energy spectra under different radiation environments (SPE, GCR, Van Allen radiation belt) are determined, and 15 shielding materials are selected for shielding performance analysis to determine the shielding efficiency of the materials. Subsequently, a multi-layer material shielding performance analysis model based on uniform design is proposed. In this model, the width, number of layers, and material distribution of the shielding materials are defined as control parameters. By using experimental simulation data, a regression model is established to clarify the relationship between the control parameters and the dose equivalent, so as to identify the optimal combination of control parameters. Through radiation shielding experiments with the MCNP6 particle transport software, the optimal design of multi-layer materials is determined, and verification and comparative analysis are carried out through the FLUKA code to verify the effectiveness of the proposed multi-layer radiation shielding optimization model. Thus, it provides a theoretical basis for the optimal design of multi-layer space radiation shielding materials. (III) Summary of the Invention:

[0005] 1. Objective: The objective of the present invention is to provide a method for optimizing multi-layer space shielding materials based on uniform design, which considers the shielding performance analysis of single-layer materials under different radiation environments and the optimization modeling of multi-layer shielding materials based on uniform design. This method solves the problem that it is difficult to achieve the shielding efficiency of materials in the space particle environment due to the unclear control parameters of multi-layer shielding material modeling, and verifies the correctness of the established optimization model, making the particle transport results more valuable for reference, and providing a theoretical basis for the effective optimization of multi-layer radiation materials in the space environment.

[0006] 2. Technical Solution: The present invention is a method for optimizing multi-layer space shielding materials based on uniform design, which includes the following steps:

[0007] Step 1: Determine the radiation shielding parameters;

[0008] Determine the shielding parameters of the shielding materials, and the shielding parameters are used to describe the shielding performance of the materials. The stopping power and fragmentation cross-section of charged particles in the materials are selected as the parameters to describe the shielding performance of the materials.

[0009] Step 2: Analyze and determine the radiation shielding materials;

[0010] To screen and evaluate the radiation protection performance of shielding materials through simulation calculations, it is achieved by using particle transport codes. These particle transport programs usually rely on measured nuclear cross-section information. By measuring the Bragg curves of high-energy heavy ions. Examining the energy loss of the particle beam passing through the material is more informative than examining the path of individual particles. Use SRIM-2013 to simulate and calculate the Bragg depth position of heavy ion beams in different materials within the energy range of 1 GeV. The effect of the shielding material in blocking radiation can be determined. Fifteen shielding materials were mainly studied, and materials containing hydrogen, boron, and nitrogen effectively improved the shielding ability.

[0011] Step 3: Determine the space radiation environment;

[0012] The space radiation environment is mainly penetrated by the charged particle radiation of SPE, GCR, and the Van Allen belts. We established three different radiation environment energy spectra. For all studies, the GCR spectrum during the solar minimum in 2010 in the BO-2014GCR model was used. Comparing coronal mass ejections (CMEs), pulsed SPEs, and GCRs by comparing elemental abundances. Use omere to simulate the Van Allen belt proton and electron spectra. The energy spectra of single or combined particle fields with these spectra are generated according to a predetermined input and output format and used as the input for Monte Carlo simulations.

[0013] Step 4: Geometric design and material result analysis;

[0014] Adopt a spherical shell-like geometry to establish a shielding simulation model for particle energy spectrum shielding calculations. Use MCNP6 to analyze the shielding performance of different shielding materials using different energy spectra. Evaluate the exposure vs. spherical shielding thickness (depth) curves of various candidate shielding materials, thus balancing the preliminary quality requirements and radiation constraints with additional mission parameters.

[0015] Step 5: Optimization of multi-layer shielding materials based on uniform design;

[0016] To improve the shielding effect of multi-layer materials, a research on the combined optimization method of multi-layer materials is carried out. Based on the above research and actual requirements, the dose equivalent is selected as the main indicator to measure the shielding ability of the material. The structural parameters include the number of material layers, the material sequence, and the material combination. The surface density is the main control parameter. Considering cost limitations and time requirements, the uniform design method is used to reduce the number of experiments at high parameter levels. By exploring the dependence of four control parameters on the dose equivalent of shielding performance, a regression model is established and the optimal values of the parameters are solved.

[0017] Step 6: Analysis of simulation results;

[0018] Based on the uniform design, a combination scheme of different material plates was proposed. Of course, it is necessary to pay attention to ensuring that all calculations are carried out using exactly the same assumptions: the same radiation transport scheme, geometry, GCR radiation input boundary conditions, and damage assessment model. This is instructive for optimizing the results by changing the materials and thicknesses of different layers in the design. From the result analysis, it can be seen that aluminum can be used together with epoxy resin to minimize the dose equivalent. Through the combined design of multi-layer materials, it is found that Design 3 and Design 6 have the best shielding efficiency.

[0019] Step Seven: Comparative analysis and verification.

[0020] To evaluate the effectiveness of the optimal parameters, the test samples were verified based on the optimal parameter values. The optimal parameter values of the two designs were verified through the FLUKA code. The numerical simulation results of the multi-layer radiation shielding materials have a high degree of agreement, and the best optimization scheme was determined. Design 6 reflects relatively low levels of proton and electron fluxes at higher orbital altitudes. Therefore, the results of the verification test can clearly demonstrate the effectiveness of the proposed model. In addition to radiation shielding, meeting these material requirements can also reduce the weight savings predicted based on radiation shielding analysis. This indicates that a radiation protection design strategy with quantitative support may be used for future spacecraft habitats. (IV) Description of the Drawings:

[0021] Figure 1 Schematic diagram of the implementation step process

[0022] Figure 2 Comparison of the radiation protection performance of different materials based on the Bragg curve

[0023] Figure 3 Annual GCR energy spectra of ions with Z = 1, 2, 8, 26 and a solar modulation parameter of 475 MV

[0024] Figure 4 Van Allen belt energy spectra: (a) Proton energy spectrum during solar maximum (b) Electron energy spectrum during solar maximum

[0025] Figure 5 Design diagram of a spherical geometry exposed to isotropic radiation

[0026] Figure 6 Comparative dose equivalent analysis of single-layer radiation shielding materials (BON2010GCR model, ICRP-60)

[0027] Figure 7 Comparative dose equivalent analysis of single-layer radiation shielding materials (SPE related to the free-space Carrington event)

[0028] Figure 8Comparative Dose Equivalent Analysis of Single-Layer Radiation Shielding Materials (2023, Inclined 48.6°, Low Earth Orbit Environment) Figure 9 Comparative Dose Equivalent Analysis of Eight Multilayer Shielding Material Designs (BON2010GCR Model, ICRP-60)

[0029] Figure 10 Comparison of Design 3 Results Based on MCNP6 and FLUKA Codes

[0030] Figure 11 Comparison of Design 6 Results Based on MCNP6 and FLUKA Codes

[0031] Figure 12 Hard Shell Design Solution for Multilayer Radiation Materials of Spacecraft Hull (V) Specific Implementation Manner:

[0032] The stress damage simulation method for the through-hole insertion process of electronic components of the present invention will be further described in detail below with reference to the accompanying drawings. The specific steps are as follows:

[0033] Step 1: Determine the radiation shielding parameters for evaluating the multilayer shielding material;

[0034] First, determine the shielding parameters of the shielding material. The shielding parameters are used to describe the shielding performance of the material.

[0035] The basic particles of space radiation have shielding materials, and radiation shielding mainly realizes the energy loss of space radiation. The Bethe-Bloch and Bradt-Peters equations can be used to roughly estimate the energy loss:

[0036]

[0037] where S is the stopping power or linear energy transfer (LET). σ is the fragment cross-section, N A Avogadro's constant ρ is the density of the shielding material. e is the electron charge, m is the electron mass, c is the speed of light, β = c / v. I is the mean excitation energy, A p and A T are the atomic weights of the projectile and the shielding material target, Z p and Z T are the atomic numbers of the projectile and the shielding material target. r0 is the radius of the atomic nucleus, C(β) is the shell correction term, L1(β) is the Barkas correction term, L2(β) is the Bloch correction term, L3(β) is the Mott correction term, and the semi-empirical terms c1 and c2 are the energy-related geometric cross-section correction terms in Formula 2.

[0038] Durante and Cucinotta obtained the following approximate values of the stopping power and fragmentation cross-section of charged particles in the material per unit target mass using Formulas 1 and 2:

[0039]

[0040]

[0041] The target atomic weight A of the shielding material T It is also inversely proportional to the stopping power and fragmentation cross section of charged particles in the material. It can be deduced from the formula that light materials will have better effects in space radiation protection. Liquid hydrogen theoretically becomes the best shielding material. Due to the need for cryogenic storage and thermal insulation containers, liquid hydrogen has safety and reliability problems, which means that it still faces many challenges in the practical application of space radiation protection. For space radiation shielding, materials with high shielding characteristic values are preferred. Therefore, it is very necessary to study the radiation resistance performance of materials.

[0042] Step 2: Analyze and determine the radiation shielding material;

[0043] To screen and evaluate the radiation protection performance of shielding materials through simulation calculations, tools such as HZETRN, MCNP6, GEANT4, PHITS, and FLUKA are often used. These transport codes usually rely on measured nuclear cross-section information.

[0044] An efficient screening method for determining the effectiveness of a shielding material in blocking radiation is to measure the Bragg curve of high-energy heavy ions. Examining the energy loss of the particle beam passing through the material is more informative than examining the path of a single particle because the interaction between each incident particle and the material it passes through is random. Use SRIM-2013 to simulate and calculate the Bragg depth position of heavy ion beams in different materials within the energy range of 1 GeV. The number of heavy ions in a single simulation is 10 6 pieces, and the results are as Figure 2 .

[0045] Examining the characteristics of the initial slope of the Bragg curve is a useful screening method to determine the effectiveness of a shielding material in blocking radiation. If the shielding thickness is x, theoretically the radiation particles should not be damaged. The formula for the flux F(x) is:

[0046]

[0047] When the shielding thickness x is very small, the stopping power S can be considered a constant. If it is assumed that the radiation particles deposit energy completely through the incident projectile.

[0048] Through the above analysis, we focused on studying 15 shielding materials (see Table 1). Materials containing hydrogen, boron, and nitrogen effectively improve the shielding ability. Polymer fiber and fiber resin shielding materials are also comparable in reducing space radiation.

[0049] Table 1 Target materials used in the experiment and their physical parameters

[0050]

[0051] Step 3: Determine the space radiation environment;

[0052] The space radiation environment is mainly penetrated by charged particle radiations of SPE, GCR, and the Van Allen belts. Among them, GCR charged particles are dangerous to humans in spacecraft, while SPE may be dangerous to humans protected only by current spacesuits. For all studies, the GCR spectrum during the solar minimum in 2010 in the BO-2014GCR model is used, with a solar modulation parameter of 475 MV, assuming that GCR occurs at 1 AU in free space, as Figure 3 shown. All transport estimates in the energy range from 1 keV / n to 100 GeV / n include particles between Z = 1 and Z = 28. The GCR energy spectrum is directly collected for MC simulation without using any additional biasing methods.

[0053] Solar particle events (SPE) are proton masses accelerated by the solar magnetic field. For the photosphere, coronal mass ejections (CME), impulsive SPE, and GCR, by comparing elemental abundances, the proton flux accounts for more than 90% of the total, although their dose equivalent contribution rate only accounts for 8% of the total. Iron nuclei only account for 0.03% of the GCR flux, three orders of magnitude lower than the proton flux, but their dose equivalent contribution is 20%. Therefore, it is necessary to consider the radiation damage of heavy ions when studying the shielding performance characteristics of spacecraft materials.

[0054] Table 2 Elemental abundances of the photosphere, coronal mass ejections, impulsive SPE, and GCR

[0055]

[0056] The Van Allen belts are belts of charged particles trapped in the Earth's magnetic field. They pose a threat to spacecraft orbiting the Earth or leaving the Earth. The trapped proton model is calculated using the AP9-MIN and AP9-MAX proton flux models. We simulated the proton and electron spectra using omere, as Figure 4 . The energy of the outer belt of electrons is as high as 10 MeV, and the energy of protons is from 30 keV to 500 MeV, although protons with energies higher than 30 MeV will penetrate into the inner belt.

[0057] This section studies the energy spectra of the space environment, including GCR, SPE, and the Van Allen belts. The energy spectra of single or combined particle fields with these spectra are generated according to the predetermined input and output formats as the input for Monte Carlo simulation.

[0058] Step 4: Geometric design and material result analysis;

[0059] To simplify the problem and reduce the calculation time, a spherical shell-like geometry is adopted. Due to the isotropy of the particle energy spectrum in space, the spherical shell-like geometry provides a reasonable approximation for studying space radiation protection problems. The schematic diagram of the spherical shell geometry used for particle energy spectrum shielding calculation is as Figure 5 shown. The geometric structure used in this study is chosen to provide a reasonable connection for engineering design applications and ongoing experimental work, while allowing the MC simulation to approach convergence for low-energy light ions and heavy target fragments at a reasonable computational cost.

[0060] MCNP6 is used to analyze the shielding performance of different shielding materials with different energy spectra. It can evaluate the exposure-dose equivalent curves of various candidate shielding materials with respect to the spherical shielding thickness (depth), thus balancing the preliminary mass requirements and radiation constraints with additional mission parameters. Figure 6 Represents the multiple calculation results of MCNP6, simulating the dose equivalent behind different shielding materials at 1 AU for the solar minimum GCR in 2010. Figure 7 Comparative dose equivalent analysis of single-layer radiation shielding materials (SPE related to the free-space Carrington event). Figure 8 Comparative dose equivalent analysis of single-layer radiation shielding materials (for the inclined 48.6° low Earth orbit environment recorded in 2023).

[0061] Step Five: Optimization of multi-layer shielding materials based on uniform design;

[0062] In the material design process of multi-layer radiation shielding, the stopping power and total nuclear fragmentation cross-section of the materials are the main factors affecting the shielding performance of the materials. Therefore, in order to improve the shielding effect of multi-layer materials, it is necessary to study the combined optimization method of multi-layer materials. Based on the above research and actual requirements, the dose equivalent is selected as the main index to measure the shielding ability of the materials. The structural parameters include the number of material layers, material order, and material combination. The surface density is the main control parameter.

[0063] Table 3 lists the ranges of these main control parameters, which are obtained according to actual requirements, including the size, order, surface density, and number of layers of the shielding materials under operating conditions. Design the gradients of different parameters.

[0064] Table 3 Ranges of control parameter values in the experiment

[0065]

[0066] From a practical perspective, considering cost constraints and time requirements, the uniform design method is adopted to reduce the number of experiments at high parameter levels. To balance the experimental cost, fully explore the entire experimental field and consider practical needs, the number of parameter levels is set to 15 accordingly. The best columns should be selected from a specific uniform design table with the smallest deviation to represent the best uniform design of the experiment. Therefore, according to the principle of the smallest deviation, the first column, the fourth column, the fifth column, and the sixth column are selected from it to generate the experimental plan, and the specific arrangement is shown in Table 4.

[0067] Table 4 Uniform design table with four factors and fifteen levels

[0068]

[0069] Through stepwise regression analysis of the quadratic polynomial, the dependence of the four control parameters on the dose equivalent of the shielding performance was explored. The commonly used quadratic model is expressed as follows.

[0070]

[0071] Among them, a k b ij are unknown values that can be calculated based on the experimental data by the least squares method. y represents the value of the dose equivalent.

[0072] The dose equivalent can be calculated by numerical methods. However, those parameters shown in Equation 2 are difficult to obtain and calculate. Then, to simplify the numerical calculation, Equation 6 is given:

[0073]

[0074] Based on the experimental data, the stepwise regression method is applied to obtain the regression model. Based on Equation 6, the regression model can be expressed as follows.

[0075]

[0076] Among them,

[0077] To solve the optimal values of the parameters from the regression model, the partial derivatives of y with respect to the control parameters are taken according to Equation 7, and the results are shown in Equation 8.

[0078]

[0079] The optimal values calculated according to Equation 8 are listed in Table 6, and the optimal combination of the control parameters is determined.

[0080] Table 6 Optimal parameter values for shielding performance

[0081]

[0082] Step 6: Simulation result analysis;

[0083] Based on the uniform design, combination schemes of different material plates were proposed. Of course, it is necessary to pay attention to ensuring that all calculations are carried out using exactly the same assumptions: the same radiation transport scheme, geometry, GCR radiation input boundary conditions, and damage assessment model. These 15 experiments were carried out according to the experimental plan in Table 4. Considering the characteristics of the radiation shielding materials and the weak shielding performance of Ta and W, cutting experiments were carried out. The radiation shielding experiments for No. 2 and No. 3 were cut. The experimental data are listed in Table 7.

[0084] Table 7 Complex multi-layer material design 1 to 8

[0085]

[0086] According to the experimental plan in Table 7, 8 experiments were carried out. Figure 9 Showing the dose equivalent analysis results of eight shielding designs, the final answer for the performance of each shielding design is 100 g / cm 2 The dose equivalent exposure rate after the shielding material, indicating the position inside the spacecraft. This is instructive for optimizing the results by changing the materials and thicknesses of different layers in the design. From the result analysis, the dose equivalent of single-layer Al is reduced to about 322.2 mSv / year. The combined design of hydrogen-rich shielding materials gradually reduces the dose equivalent to ~200 mSv / year. Epoxy resin is effectively used for neutron shielding. Aluminum can be used together with epoxy resin to minimize the dose equivalent. Through the combined design of multi-layer materials, it is found that Design 3 and Design 6 have the best shielding efficiency, and their dose equivalents are reduced to 101.9 mSv / year and 161.1 mSv / year.

[0087] Step 7: Comparative analysis and verification;

[0088] To evaluate the effectiveness of the optimal parameters, the test samples were verified based on the optimal parameter values. Based on the same particle energy spectrum and geometric boundary conditions, numerical analysis was carried out using the FLUKA program to verify the optimal parameter values of the two designs.

[0089] Figure 10 and Figure 11 Showing the dose equivalent comparison of the results generated by the MCNP6 and FLUKA deterministic codes for the 2010 solar minimum GCR. The numerical simulation results of the multi-layer radiation shielding materials are in good agreement.

[0090] In Design 6 (Al + C 14 H 14 N2O4 + C 21 H 25In (CIO5 + LiH + PBO + BN + Al), compared with MCNP6, the dose equivalent simulated by FLUKA is very close, with an error less than 5%. At 30 g / cm2, the result of FLUKA is slightly lower than that of MCNP6. The average energy values of neutrons and photons are 0.032 MeV / n and 0.0057 MeV / n, respectively.

[0091] The multi-layer composite shielding can be lighter than aluminum shielding, thus saving weight while meeting the required total dose level. Design 6 reflects a relatively low level of proton and electron fluxes at higher orbital altitudes. Therefore, the results of the verification tests can clearly demonstrate the effectiveness of the proposed model.

[0092] 100 g / cm made of Design 6 2 The design solution of the hard shell module with a thick radiation protection layer is visualized as Figure 12 shown. In the design of the multi-layer composite, a visual indication of the multi-layer material distribution and an estimate of the mass characteristics are provided. In addition to radiation shielding, meeting these material requirements can also reduce the weight savings predicted based on radiation shielding analysis. This indicates that radiation protection design strategies supported by quantitative data may be used for future spacecraft habitats.

Claims

1. A method for optimizing multi-layer space shielding materials based on uniform design, characterized in that: Based on the theory of particle physics, the shielding performance and combination optimization of multi-layer shielding materials in multi-layer space environment are studied; by comprehensively analyzing the radiation resistance of various shielding materials, the dose equivalent is minimized, and the relationship between parameters and dose equivalent is established, and a multi-layer material shielding performance analysis model based on uniform design is established; in this model, the width, number of layers and material distribution of the shielding material are defined as control parameters; through experimental simulation data, a regression model is established to clarify the relationship between control parameters and dose equivalent, so as to identify the best combination of control parameters and determine the best multi-layer radiation shielding scheme; by analyzing the results using particle transport code, the effectiveness of the optimal parameters and regression model is confirmed; finally, the multi-layer space radiation shielding material is summarized in combination with the optimization model, so as to provide a theoretical basis for the optimization of multi-layer material shielding of spacecraft; the specific steps of this method are as follows: Step 1: Determine radiation shielding parameters; The key shielding parameters are selected as the description of the energy loss of the material in space radiation; the estimated particle energy loss calculation is realized according to the Bethe-Bloch and Bradt-Peters equations: The key shielding performance description parameters S and σ are selected; S is the stopping power or linear energy transfer (LET), σ is the fragment cross section, and N A Avogadro constant ρ, the density of the shielding material, e, the electron charge, m, the electron mass, c, the speed of light, β = c / v, I, the average excitation energy, A p and A T Atomic weight of projectile and shielding material target, Z p and Z T The atomic number of the projectile and the shielding material target, r0 the radius of the nucleus, C(β) the shell correction term, L1(β) the Barkas correction term, L2(β) the Bloch correction term, L3(β) the Mott correction term, the semi-empirical terms c1 and c2 are the energy-dependent geometric cross-section correction terms in Equation 2, and the following approximate values ​​of the stopping power and fragmentation cross section of the charged particle per unit target mass material are derived from Equations 1 and 2: Target atomic weight of shielding material A T It is also inversely proportional to the stopping power and fragmentation cross section of the charged particles in the material; through the description of key shielding parameters, the main reference basis for material selection is determined; Step 2: Analyze and determine radiation shielding materials; Based on the descriptive parameters of key shielding materials, the material selection method for aerospace radiation shielding is determined. That is, measuring the Bragg curve of high-energy heavy ions and checking the energy loss of particle beams passing through materials is more informative than checking the path of individual particles. Several shielding materials are analyzed and determined, providing a basis for the subsequent optimization design of multi-layer material shielding. Step 3: Determine the space radiation environment; First, the particle energy spectrum of the space environment, the charged particle environment of SPE, GCR and Van Allen belt, is determined to analyze the impact of space shielding of different radiation environments; secondly, the particle energy spectrum is determined; finally, the energy spectrum of the space environment, including GCR, SPE and Van Allen belt, is passed; the energy spectrum of single or combined particle fields with these spectra is generated according to the predetermined input and output format as the input of Monte Carlo simulation; Step 4: Geometric design and material results analysis; A quasi-spherical shell geometry was used for the analysis, and different shielding performances of different shielding materials were analyzed using different energy spectra through MCNP6. The exposure and spherical shielding thickness curves of various candidate shielding materials were evaluated to balance the preliminary quality requirements and radiation constraints with additional mission parameters, and comparative dose equivalent analysis of GCR, SPE and Van Allen belt single-layer radiation shielding materials was simulated. Step 5: Multi-layer shielding material optimization based on uniform design; Dose equivalent is selected as the main indicator to measure the shielding ability of materials. Structural parameters include the number of material layers, material sequence and material combination. Surface density is the main control parameter. Different gradients are designed within the control parameter range. The uniform design method is used to reduce the number of experiments at high parameter levels. A four-factor fifteen-level test table is designed. According to the minimum deviation principle, several columns are selected to generate the experimental plan. Then, the regression model of the key control parameters of the multi-layer shielding material is established, and the regression model is obtained by applying the stepwise regression method. Step 6: Simulation results analysis; On the basis of uniform design, a combination of different material panels is proposed to select the best design; Step 7: Comparative analysis and verification; In order to evaluate the effectiveness of the optimal parameters, the test samples were verified based on the optimal parameter values; based on the same particle energy spectrum and geometric boundary conditions, numerical analysis was performed using the FLUKA program to verify the optimal parameter values ​​for the best design.

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