A method for determining the thickness of an sada slip ring shield against internal charging

Abstract

This invention discloses a method for determining the thickness of the shielding shell for internal charging of a spacecraft's SADA slip ring. First, the Monte Carlo method is used to simulate the transport of charged particles in a three-dimensional conductive slip ring under space radiation conditions. Then, three-dimensional statistics are performed on the charge and energy deposition inside the slip ring to calculate the three-dimensional distribution of dose rate and charge deposition density. Combining this with the radiation-induced conductivity-temperature relationship, the three-dimensional distribution of the electric field and potential inside the slip ring at different temperatures and shielding thicknesses is calculated, thereby assessing the risk of internal charging and determining the shielding shell thickness under different radiation environments. This invention eliminates the need for simplified complex structures before local simulation calculations, increasing the accuracy and universality of internal charging calculations. Furthermore, the combination of the Monte Carlo method and finite element time-domain calculations allows for obtaining the internal charging conditions and charging balance processes under different complex operating conditions, improving the comprehensiveness and effectiveness of the internal charging calculation results.

Description

Technical Field

[0001] This invention belongs to the field of spacecraft power system protection technology, specifically relating to a calculation method for determining the thickness of the anti-internal charged shielding shell of the SADA slip ring in a spacecraft. Background Technology

[0002] With the continuous development and progress of my country's aerospace technology, more and more spacecraft will be put into operation in orbit. The space environment is a complex and variable radiation environment, and spacecraft operating in orbit are subject to radiation damage from various particles. The power system is the energy source for spacecraft operation in orbit, and surface charging and discharging and deep charging and discharging effects occur under the irradiation of particles of different energies. Currently, it is generally believed that the deep charging and discharging effect of the medium is the main cause of malfunctions or anomalies in geosynchronous orbit spacecraft. The Solar Array Drive Assembly (SADA) is the actuator for the solar panel orientation of the spacecraft. It transmits power through internal slip rings and operates under high voltage, high current, and motion conditions. In a high-energy electron radiation environment, charged particles can pass through the shielding shell of the spacecraft's SADA slip ring and propagate and deposit inside the medium, thus establishing an internal electric field. When the electric field strength exceeds the breakdown threshold, discharge or breakdown will occur inside the medium, severely affecting the insulation performance of the dielectric material. Simultaneously, the electromagnetic pulse generated by the discharge can couple into the spacecraft's internal circuitry, interfering with data and command reading, and affecting the normal operation and safety performance of the spacecraft. Therefore, the anti-internal charging protection design of the spacecraft's SADA slip ring is crucial.

[0003] The main research methods for the deep charging and discharging effect of dielectric materials include on-orbit experiments, ground simulation experiments, and simulation calculations. Simulation calculations are widely used as an important tool for design evaluation and qualitative analysis. Many scholars have conducted extensive simulation studies on the deep charging effect, but most are one-dimensional and two-dimensional simulations, which can only obtain general laws governing the charging within the dielectric. Existing three-dimensional simulations simplify complex structures into cuboids or cylinders before performing localized deep charging simulations, lacking research on the electric field distortion characteristics within complex structures. This prevents a reasonable and comprehensive assessment of the deep charging level of special structures, thus limiting their application in guiding the design of spacecraft SADA shielding shells. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a method for determining the thickness of the shielding shell for the SADA slip ring of a spacecraft to resist internal charging. By obtaining the three-dimensional time-domain distribution of the electric potential and electric field intensity inside the conductive slip ring under different temperatures and shielding thicknesses, the risk of internal charging can be assessed based on the dielectric electric field breakdown threshold, and the shielding shell thickness under different radiation environments can be determined.

[0005] The method for determining the thickness of the internal charged shielding shell of the SADA slip ring in a spacecraft, as described in this invention, comprises the following steps:

[0006] A method for determining the thickness of the internal charged shielding shell of a spacecraft's SADA slip ring, characterized by the following specific steps:

[0007] Step 1: Conduct a simulation of the transport of high-energy particles inside the SADA slip ring structure medium.

[0008] Step 2: Use the irregular small grid statistical method to statistically analyze the physical quantities inside the medium and obtain the charge deposition number N in each small grid. G4 and deposition energy E G4 Save it as a .txt file and export it.

[0009] Step 3: Import the multiple .txt files obtained in Step 2 into MATLAB, perform physical quantity conversion calculations, and obtain the charge deposition rate Q within each irregular small grid. j and radiation dose rate The radiation-induced conductivity σ within each irregular small grid was further obtained. r Subsequently, using the center coordinates of each small grid as a representative, the three-dimensional distribution of charge deposition rate and radiation-induced conductivity inside the entire SADA slip ring can be obtained according to the irregular small grid number.

[0010] Step 4: Construct the three-dimensional structure of the SADA slip ring from Step 1 in COMSOL. Import the three-dimensional distribution of charge deposition rate and radiation-induced conductivity inside the slip ring obtained in Step 3, and import the conductivity-temperature relationship using an interpolation method. Set the corresponding temperature, operating voltage and grounding method, and perform time-domain calculations based on the current continuity equation to obtain the three-dimensional distribution of potential and electric field intensity inside the slip ring and the charging balance process.

[0011] Step 5: According to the requirements, change the shielding shell thickness in Step 1 and the temperature in Step 4, and repeat Steps 1-4 to obtain the three-dimensional distribution of electric potential and electric field intensity inside the SADA slip ring under different temperatures and shielding thicknesses. Combined with the breakdown threshold of the electric field intensity inside the medium, assess the risk of internal charging and determine the shielding shell thickness under different radiation environments.

[0012] The advantages of this invention are:

[0013] 1. In the technical solution of this invention, the irregular small grid statistical method is used to realize the statistical distribution of different physical quantities in the three-dimensional distribution inside the SADA slip ring of the spacecraft. Unlike the traditional simplified-local simulation calculation method, this invention can calculate the three-dimensional distribution of electric potential and electric field intensity inside the entire slip ring based on the three-dimensional distribution of physical quantities. At the same time, it can accurately obtain the electric field distortion characteristics inside the complex structure, thus improving the accuracy of the calculation of the charged structure.

[0014] 2. In the technical solution of this invention, the irregular small grid statistical method can be used to perform statistical and deep charging simulation calculations on any complex structure of a spacecraft. While improving the accuracy of the internal charging calculation, it also has strong universality. At the same time, the theory of combining radiation-induced conductivity and intrinsic conductivity-temperature is adopted, which can simulate the deep charging effect at different temperatures, further enhancing the universality of the internal charging calculation.

[0015] 3. In the technical solution of this invention, the finite element calculation adopts a three-dimensional time domain calculation method, which can obtain the charging balance process and electric field distortion characteristics at various locations inside the complex structure, thereby increasing the comprehensiveness of the internal charge risk assessment.

[0016] 4. In the technical solution of this invention, the Monte Carlo method and the finite element method are combined, which is different from the traditional radiation-induced conductivity model calculation method. This method can obtain the internal charge of the structure under different space radiation environments, thus improving the effectiveness of the internal charge calculation results. Attached Figure Description

[0017] Figure 1 A flowchart illustrating the calculation method for determining the thickness of the SADA slip ring anti-internal charged shielding shell of a spacecraft, provided by this invention;

[0018] Figure 2 A schematic diagram of the overall three-dimensional structure of the SADA slip ring of a spacecraft constructed for an example of the present invention;

[0019] Figure 3 The diagram shows the changes in electric potential and electric field strength at point A inside the slip ring.

[0020] Figure 4 The maximum electric field strength inside the sliding ring varies with different temperatures and shielding thicknesses in this invention example. Detailed Implementation Plan

[0021] The present invention will now be described in further detail with reference to the accompanying drawings.

[0022] The present invention provides a method for determining the thickness of the SADA slip ring anti-internal charged shielding shell of a spacecraft, such as... Figure 1 As shown, the specific steps are as follows:

[0023] Step 1: Use Geant4 to simulate the transport of high-energy particles inside the SADA slip ring structure medium.

[0024] A. Use G4DetectorConstruction to construct the 3D structure, material properties, and location and thickness of the shielding shell of the spacecraft's SADA slip ring. The constructed 3D structure of the SADA slip ring is as follows: Figure 2As shown, the inner diameter is 3mm, the outer diameter is 18mm, and the thickness is 6mm. The insulating medium is polyimide, the ring conductor is silver, and the width of the conductive ring is 1.8mm and the thickness is 1mm. The distance between the shielding shell and the upper edge of the conductive ring is 17mm, and the initial thickness is set to 1mm.

[0025] B. Using G4GPS, the types, energies, positions, and incident modes of space radiation particles are defined. In this example, the particle source is a surface source, 10 cm from the shielding shell, and is incident isotropically from random positions within the surface source. The particle energy spectrum adopts a typical GEO worst-case electron flux model, with an energy range of 0.03–10 MeV. The electron flux decays exponentially with respect to the energy spectrum, and the actual beam current density is 8.832 pA / cm². 2 The number of incident particles is set to 1×10 7 indivual.

[0026] C. Use G4Physicslist to add the physical processes of particle-medium interaction. The specific physical processes added are related to the particles and the medium. This process is based on finding the interaction processes between the particles and the medium, and then adding them using G4Physicslist. In this example, the physical processes of electron-medium interaction include multiple scattering, ionization, and bremsstrahlung.

[0027] Furthermore, the transport and reaction of particles in the medium were simulated based on the Monte Carlo stochastic method.

[0028] Step 2: Statistically measure the physical quantities inside the medium.

[0029] Since the SADA slip ring is a ring structure, in cylindrical coordinates, it is divided along the radial distance r, azimuth angle φ, and height z directions using an irregular small grid statistical method, resulting in the following divisions: The irregular small grid is divided into 216,000 irregular small grids and numbered; in this embodiment, Δr is taken as 0.2. Take 6°, and Δz = 0.1 mm.

[0030] Subsequently, the physical quantity statistics functions of G4PSEnergyDeposit3D and G4PSCellCharge3D were used to statistically analyze the corresponding physical quantities within each irregular small grid, obtaining the charge deposition number N within each small grid. G4 and deposition energy E G4 Save it as a .txt file and export it.

[0031] Step 3: Calculation of physical quantity conversion;

[0032] Import the multiple .txt files obtained in step 2 into MATLAB, and calculate the charge deposition rate Q within each irregular small grid by performing physical quantity conversions according to the formulas. j and radiation dose rate The radiation-induced conductivity σ within each irregular small grid can then be calculated using the formula. r Using the center coordinates of each small grid as a representative, the three-dimensional distribution of charge deposition rate and radiation-induced conductivity inside the entire SADA slip ring can be obtained according to the irregular small grid numbering.

[0033]

[0034]

[0035] σ r =k r D λ (3)

[0036] In the formula, D is the radiation dose rate; e is the electron charge; ΔV is the volume of the small grid; ρ d The density of the medium; Δt = N / F e S is the incident time of N particles; S is the particle source area, F e k represents the actual electron beam current density in space. r λ and λ are the coefficients and exponents of radiation-induced conductivity related to the material.

[0037] Step 4: Based on the finite element method, calculate the three-dimensional distribution of electric potential and electric field intensity inside the medium;

[0038] In the finite element calculation software COMSOL, the three-dimensional structure of the SADA slip ring in step 1 is constructed. The three-dimensional distribution of charge deposition rate and radiation-induced conductivity inside the slip ring obtained in step 3 is imported into it. Formula (4) and the conductivity-temperature relationship of the formula are imported by interpolation. The temperature is set to 293K (room temperature), the working voltage is 100V and the grounding method is back grounding. Based on the current continuity equation, time domain calculation is performed to obtain the three-dimensional distribution of potential and electric field intensity inside the slip ring and the charging balance process at a point A (9.1,0,-3) on the insulating medium, such as Figure 3 As shown in the figure, the system basically reaches equilibrium after about 20 hours of charging, at which point the internal electric field strength reaches its maximum.

[0039]

[0040]

[0041] In the formula, σ T σ represents the conductivity of the medium as a function of temperature. ETThe dielectric conductivity of the medium under the combined effects of temperature and electric field; k is the Boltzmann constant; T is the temperature; E A β is the activation energy of the dielectric material's conductivity; A is a constant, which can be derived from the dielectric conductivity at room temperature (293 K); E represents the modulus of the electric field strength; e is the electron charge; β F =(e 3 / πε) 0.5 It depends on the dielectric constant of the material, where ε is the dielectric constant of the material and δ is the jumping distance of electrons between the dielectric lattice.

[0042] Step 5: Change the shielding thickness in Step 1 to 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, and 5mm. For each thickness, adjust the temperature to the operating temperature of the shielding shell for the calculated thickness. For example, in this embodiment, the shielding shell is used in a GEO environment with a temperature range of 253K-343K, so the temperature is adjusted to 253K and 343K. Then repeat steps 1 to 4 to obtain the three-dimensional distribution of potential and electric field intensity inside the SADA slip ring under different temperatures and shielding thicknesses. The maximum electric field intensity inside the slip ring changes with temperature and shielding thickness as follows: Figure 4 As shown in the figure, temperature has a significant impact on deep charging, and the maximum electric field strength inside the slip ring decreases with increasing thickness. Considering the influence of temperature, the shielding shell thickness must be less than or equal to the breakdown threshold of the electric field strength inside the slip ring's insulating medium at all set temperatures. In this embodiment, the insulating medium is polyimide, whose internal electric field strength breakdown threshold is 2 × 10⁻⁶. 7 V / m, according to Figure 4 It can be seen that when the shielding thickness is greater than or equal to 3.5 mm, even at a temperature of 253 K, the maximum electric field strength inside the SADA slip ring is not greater than the breakdown threshold. Therefore, considering the influence of temperature in the worst energy spectrum radiation environment of GEO used in this case, it is determined that the thickness of the shielding shell of the spacecraft SADA slip ring should be ≥3.5 mm. At this time, the risk of internal charging is low and discharge is not likely to occur.

Claims

1. A method for determining the thickness of the anti-internal charged shielding shell of a spacecraft's SADA slip ring, characterized in that: The specific steps are as follows: Step 1: Conduct transport simulations of high-energy particles within the SADA slip ring structure medium; Step 2: Use the irregular small grid statistical method to statistically analyze the physical quantities inside the medium and obtain the charge deposition number N in each small grid. G4 and deposition energy E G4 Save it as a .txt file and export it; Step 3: Import the multiple .txt files obtained in Step 2 into MATLAB, perform physical quantity conversion calculations, and obtain the charge deposition rate Q within each small grid. j and radiation dose rate : In the formula, denoted as radiation dose rate; e represents electron charge. For the volume of the small grid; The density of the medium; Let N be the incident time of the particles; S be the particle source area, and F be the incident time of the particles. e This represents the actual electron beam current density in space. Further, the radiation-induced conductivity within each small grid was obtained. : s r =k r D λ In the formula, λ and λ are the coefficients and exponents of radiation-induced conductivity related to the material; Subsequently, using the center coordinates of each small grid as a representative, the three-dimensional distribution of charge deposition rate and radiation-induced conductivity inside the entire SADA slip ring can be obtained according to the small grid number. Step 4: Construct the three-dimensional structure of the SADA slip ring from Step 1 in COMSOL, import the three-dimensional distribution of charge deposition rate and radiation-induced conductivity inside the slip ring obtained in Step 3, and import the conductivity-temperature relationship using an interpolation method. Set the corresponding temperature, operating voltage and grounding method, and perform time-domain calculations based on the current continuity equation to obtain the three-dimensional distribution of potential and electric field intensity inside the slip ring and the charging balance process. Step 5: According to the requirements, change the shielding shell thickness in Step 1 and the temperature in Step 4, and repeat Steps 1-4 to obtain the three-dimensional distribution of electric potential and electric field intensity inside the SADA slip ring under different temperatures and shielding thicknesses. Combined with the breakdown threshold of the electric field intensity inside the medium, assess the risk of internal charging and determine the shielding shell thickness under different radiation environments.

2. The method for determining the thickness of the internal charged shielding shell of a spacecraft's SADA slip ring as described in claim 1, characterized in that: The specific steps are as follows: The specific method in step 1 is as follows: A. Construct the three-dimensional structure and material properties of the spacecraft's SADA slip ring, as well as the location and initial thickness of the shielding shell; B. Define the types, energies, positions, and incident forms of space radiation particles; C. Add the physical processes of particle-medium interaction, and simulate particle transport and reaction in the medium based on the Monte Carlo stochastic method.

3. The method for determining the thickness of the anti-internal charged shielding shell of the SADA slip ring in a spacecraft as described in claim 1, characterized in that: The specific steps are as follows: Step 3 The constructed SADA slip ring is divided into sections along the radial distance r, azimuth angle φ, and height z using an irregular small-grid statistical method. Irregular small grid.

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