WO2024099010A1 - Method and system for assessing risk of internal charging of dielectrics of spacecraft on synchronous orbit, and terminal - Google Patents

Abstract

The present invention belongs to the technical field of prevention of internal charging of dielectrics of spacecrafts. Disclosed are a method and system for assessing risk of internal charging of dielectrics of spacecraft on synchronous orbit, and a terminal. The method comprises: constructing a geosynchronous orbit (GEO) environment electron flux model; simulating an electron radiation process for a dielectric; calculating the two key factors internal charge deposition rate and dose rate of the dielectric under the GEO environment electron radiation with respect to different shielding; constructing a three-dimensional charge transport model, and, on the basis of a working voltage and the grounding mode of a sample, constructing a corresponding three-dimensional charge transport model equation set; then solving the corresponding three-dimensional charge transport equation set by using a finite element method so as to obtain the internal electric field intensity distribution of the dielectric under the corresponding working condition; judging whether there is an electrostatic discharge risk under the corresponding working condition; and obtaining an optimal shielding design solution having no electrostatic discharge risk. Therefore, a feasible calculation and verification method is provided for design and optimization of spacecraft shielding and doping modification of spacecraft dielectrics.

Description

Method, system and terminal for risk assessment of internal electrification in geosynchronous orbit spacecraft Technical Field

The present invention belongs to the technical field of spacecraft dielectric internal charging protection, and in particular relates to a method, system and terminal for assessing the risk of dielectric internal charging in a synchronous orbit spacecraft.

Background technique

At present, the interaction between high-energy electrons and spacecraft dielectrics in the space environment will cause the problem of dielectric internal charging. Dielectric internal charging will cause the insulation of polymer dielectrics to deteriorate or even fail. At the same time, the electrostatic discharge pulses generated by the dielectric internal charging will also cause abnormal operation or damage of sensitive electronic devices in the spacecraft, seriously threatening the operation safety of the spacecraft. With the development of high-power and high-voltage spacecraft, higher requirements are placed on the anti-internal charging performance of dielectric materials. At present, the research on the deep charge and discharge problem of dielectrics mainly adopts the method of numerical calculation. First, the interaction process between high-energy electrons and dielectrics in a set radiation environment is simulated to obtain data such as charge deposition rate and dose rate in the dielectric; then, the equation group is solved based on the charge transport model inside the dielectric to calculate the distribution of electric field intensity in the dielectric under the corresponding radiation time; finally, by comparing the maximum value of the electric field intensity in the dielectric with the dielectric electrostatic discharge breakdown threshold, it is evaluated whether the sample will have electrostatic discharge problems under the set radiation conditions. This will further guide the shielding design of spacecraft and select the optimal shielding thickness according to the calculation results to protect the deep charge and discharge of the dielectric.

However, there is a lack of research on the deep charge and discharge mechanism of dielectrics under the combined action of high-energy electron radiation and high working voltage. The corresponding charge and discharge mechanism and characteristics are unclear. It is still unknown how effective and applicable the traditional dielectric doping modification method is. There is currently no research in this area. Especially for spacecraft operating in geosynchronous orbit, it is urgent to develop an effective dielectric internal charge risk analysis method to guide the shielding design of spacecraft.

Currently, there is a lack of research on the deep charging and discharging mechanism of dielectrics under the combined effects of high-energy electron radiation and high operating voltage, especially in geosynchronous orbit. It is necessary to comprehensively consider actual working conditions such as spacecraft shielding factors, dielectric grounding methods, and operating voltage to comprehensively evaluate the internal charging performance of spacecraft dielectrics under electron radiation, which is lacking in current research.

technical problem

Through the above analysis, the problems and defects of the prior art are as follows:

The existing technology lacks a solution for analyzing the deep charge and discharge mechanism of dielectrics under the combined effects of high-energy electron radiation and high working voltage. The corresponding charge and discharge mechanism and characteristics are unclear, and the effectiveness and applicability of traditional dielectric doping and modification methods are unknown, and there is no feasible calculation method. Especially in geosynchronous orbit, it is necessary to comprehensively consider the actual working conditions such as spacecraft shielding factors, dielectric grounding methods, and working voltage to comprehensively evaluate the anti-internal charging performance of spacecraft dielectrics under electron radiation, which is lacking in current research.

Technical Solutions

In view of the problems existing in the prior art, the present invention provides a method for assessing the risk of internal electrification in a synchronous orbit spacecraft medium, and in particular, relates to a method for assessing the risk of internal electrification in a geosynchronous orbit spacecraft medium.

The present invention is implemented as follows: a method for assessing the risk of internal electrification of a medium in a synchronous orbit spacecraft, the method comprising:

First, a geosynchronous orbit (GEO) environmental electron flux model is constructed; then, the GEO electron flux calculated by the geosynchronous orbit environmental electron flux model is introduced into the Monte Carlo simulation software Geant4 to simulate the dielectric electron radiation process; the shielding factor is comprehensively considered to obtain the two key factors of the internal charge deposition rate and dose rate of the dielectric under different shielding under GEO environmental electron radiation; then, the dielectric parameters of the dielectric are measured, a three-dimensional charge transport model is constructed, and then the corresponding three-dimensional charge transport model equation group is constructed in combination with the working voltage and the grounding method of the sample; then, the finite element method is used to solve the corresponding three-dimensional charge transport equation group to obtain the internal electric field strength distribution of the dielectric under the corresponding working condition; by comparing the maximum value of the internal electric field strength with the breakdown strength field of the dielectric measured by the experiment, it can be judged whether there is an electrostatic discharge risk under the corresponding working condition; finally, according to the judgment result, the shielding layer material or thickness is adjusted and the calculation is repeated until the optimal shielding design scheme without electrostatic discharge risk is obtained.

Furthermore, the method for assessing the risk of internal electrification of a geostationary orbit spacecraft medium includes the following steps:

Step 1: Construction of the geosynchronous orbit environment electron flux model;

Step 2: constructing a calculation model of the electric field in the medium under electron radiation;

Step 3: Risk assessment of dielectric electrostatic discharge under electronic radiation.

Furthermore, the construction of the geosynchronous orbit environment electron flux model in step 1 includes:

The FLUMIC3 (Flux Model for Internal Charging) model is used to construct the electron flux environment of the synchronous orbit:

The outer radiation belt model in the FLUMIC3 energy spectrum model is as follows: taking into account the solar cycle and annual variations, the outer radiation belt L > 2.5, and the electron flux will be a function of fsc , foy , L and E ;

Functions of the solar cycle: ;

Where fsc represents the normalized value of the solar activity cycle, which is 0 in the year of minimum solar activity.

Functions about seasons: ;

Where foy represents the normalized value of the date in a year, with January 1 as the starting point.

Functions about energy: ;

in, .

Functions about L: ;

Where L is the distance to the center of the Earth.

Furthermore, the construction of the calculation model of the electric field in the medium under electron radiation in step 2 includes:

(1) Simulation of electron radiation process: The electron radiation program developed based on Geant4 is used to simulate the interaction between high-energy electrons and samples;

(2) The process of calculating the electric field in the medium under electron radiation: including the construction of the charge transport equation in the medium and the calculation of the electric field in the medium.

Furthermore, the simulation of the electron radiation process in step (1) includes:

1) Construct the corresponding sample model and shielding layer model in Geant4;

2) Construct an electron radiation source model and calculate relevant radiation parameters;

The result calculated by the FLUMIC3 model is the integrated flux of electrons in the GEO environment. The electron integrated flux is converted to the vertical direction. During the analysis, the electrons are set to be incident perpendicular to the sample plane. The electron source is set to a circular plane source with a radius of 6 cm, which is placed 20 cm to the left of the sample and incident perpendicular to the sample surface from left to right. At the same time, the electrons are set to be emitted in the energy spectrum sampling mode. The number of simulated incident electrons is 3× ¹⁰⁶ .

3) Calculation result processing

After the calculation is completed in Geant4, the statistical charge deposition number En and energy deposition Eg are obtained _, which need to be converted into the charge deposition rate under the set electron beam current density _. and dose rate The conversion method is as follows:

When the number of incident electrons is N , the incident electron beam current density is J ₀ , A/m ² , and the electron source area is A ₀ , m ² , then the virtual radiation time T is: s;

Where, e _q is the electron charge, which is set to 1.6×10 ^-19 C; the charge deposition rate in the medium under the actual beam current is: C/m ³ ·s;

The dose rate in the medium is: rad/s;

Furthermore, the process of calculating the electric field in the medium under electron radiation in step (2) includes:

1) Construction of charge transport equation in medium

The charge transport equations inside the medium are as follows: ;

The charge transport equations are Poisson's equation, current continuity equation and Ohm's law from top to bottom. E is the electric field strength, V/m; is the net charge density in the medium, C/m ³ ; ε is the dielectric constant of the medium, F/m; J is the net current density, A/m ² ; is the charge deposition rate in the medium, C/m ³ ·s; is the conductivity related to the electric field, S/m.

Based on the nonlinear conductivity characteristics of the modified sample. According to the measured conductivity data, the conductivity of the sample is segmented and fitted according to the size of the electric field strength. From the test data, when the electric field strength is less than 1kV/mm, the conductivity does not change significantly with the electric field, and it is set as a low field area. In the low field area, the intrinsic conductivity of the sample is used; when the field strength is greater than 1kV/mm, the conductivity will increase with the increase of the electric field strength. The area is divided into two parts with the nonlinear conductivity threshold as the dividing point, where the electric field from 1kV/mm to the mutation point threshold is set as a low growth rate area, and after the mutation point is set as a nonlinear growth area.

The overall design is as follows: .

2) Calculation process of electric field in dielectric medium

The electric field calculation model adopts the charge transport model, and the conductivity of the sample is processed by segmented fitting based on the test data. The charge transport model is solved by COMSOL software based on the finite element method, and the partial differential equation interface in the mathematical module is used to customize the equations to be solved. The coefficients of this partial differential equation and Poisson's equation are modified according to the charge transport model equations; the partial differential equation is: ; .

During the simulation calculation process, the specific working conditions are analyzed, including the grounding state, grounding position, amplitude of the working voltage and the applied position factors of the sample, corresponding to the initial state and boundary conditions of the partial differential equation group. In COMSOL, various initial states are set by modifying the initial conditions of the custom equations and adding Dirichlet boundary conditions. Geant4 programming is used to simulate the electron radiation process according to the set radiation parameters, and then the charge deposition rate and dose rate at each position in the sample are introduced into the calculation model, and then imported into COMSOL using the interpolation method; the grounding conditions and working voltage are set according to the actual working conditions of the sample, and then the sample model is meshed and the radiation time is set; the MUMPS type solver based on LU decomposition is selected for solution calculation, and finally the internal electric field distribution of the sample within the set radiation time under the actual working conditions is obtained.

Furthermore, the risk assessment of dielectric electrostatic discharge under electronic radiation in step 3 includes:

(1) Calculate the maximum electric field intensity in the medium under the corresponding electron radiation scenario.

(2) Determine the DC breakdown field strength of the sample.

The modified sample was subjected to a DC withstand voltage test using a breakdown test platform. The test electrode was a ball-ball electrode placed in insulating oil. The test data was processed using the Weibull distribution method, and the formula is as follows: ;

Where P ( E ) is the probability of cumulative failure; E is the breakdown strength; α is the shape parameter, which is used to evaluate the dispersion of the breakdown voltage; Eb is the breakdown field strength when the breakdown probability is 63.28%, _which is called the characteristic breakdown field strength.

Taking the logarithm of both ends of the test data processing formula, we get: .

(3) Comparative evaluation

Compare the calculated maximum internal electric field value of the sample under the corresponding radiation scenario with the measured DC breakdown field strength of the sample. If the maximum internal electric field value of the sample is greater than the DC breakdown field strength, it is considered that there is an electrostatic discharge risk. If the maximum internal electric field value of the sample is less than the DC breakdown field strength, it is considered that there is no electrostatic discharge risk.

(4) Shielding layer design optimization

According to the results of the comparative evaluation in step (3), if there is an electrostatic discharge risk in the spacecraft medium, the shielding layer design is readjusted; in step 1, the shielding layer material or thickness is adjusted for simulation calculation, and then the electric field inside the medium is calculated, and finally the electrostatic discharge risk of the medium is evaluated; through multiple adjustments and repeated calculations until the maximum value of the internal electric field strength of the medium under the set electron radiation conditions is less than the breakdown field strength of the medium, the shielding design is taken as the safe shielding threshold, and the shielding layer thickness or shielding material density is taken as the minimum requirement.

Another object of the present invention is to provide a synchronous orbit spacecraft medium electrification risk assessment system using the synchronous orbit spacecraft medium electrification risk assessment method, the synchronous orbit spacecraft medium electrification risk assessment system comprising:

The dielectric electron radiation module simulation is used to build the geosynchronous orbit environment electron flux model. The calculated GEO electron flux is introduced into Geant4 to simulate the dielectric electron radiation process.

The electric field intensity distribution determination module is used to construct a three-dimensional charge transport model equation group, and use the finite element method to solve the corresponding three-dimensional charge transport equation group to obtain the electric field intensity distribution in the medium under the corresponding working conditions;

The electrostatic discharge risk assessment module is used to compare the maximum internal electric field strength with the breakdown strength field of the medium to determine whether there is an electrostatic discharge risk under the corresponding working conditions.

Another object of the present invention is to provide a computer device, which includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method for assessing the risk of electrical charges in a synchronous orbit spacecraft medium.

Another object of the present invention is to provide a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes the steps of the method for assessing the risk of electrical charges in a synchronous orbit spacecraft medium.

Another object of the present invention is to provide an information data processing terminal, which is used to implement the above-mentioned risk assessment system for the charged medium in a synchronous orbit spacecraft.

Beneficial Effects

In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

In view of the gap in the existing technology for analyzing the deep charge and discharge mechanism of dielectrics, the present invention proposes a dielectric internal charge risk assessment method suitable for geosynchronous orbit spacecraft. This method comprehensively considers the actual working conditions such as the synchronous orbit electron radiation environment, spacecraft shielding factors, and operating voltage to comprehensively evaluate the electrostatic discharge risk of spacecraft dielectrics and the modification effect of the doping modification scheme for its anti-internal charge performance, thereby providing a feasible calculation verification method for spacecraft shielding design and optimization and doping modification of spacecraft dielectrics.

The present invention aims at the problem of internal charge risk assessment of spacecraft media, especially spacecraft media operating in geosynchronous orbit, and comprehensively considers the current development needs of high-voltage and high-power spacecraft, and proposes a dielectric internal electric field calculation scheme and internal charge risk assessment scheme under the combined effect of working voltage and spacecraft electronic radiation environment. At the same time, this scheme takes into account the research needs of spacecraft dielectric doping modification, and provides a comparative evaluation calculation method for the modified dielectric's anti-internal charge performance. This patent provides a feasible solution for the internal charge risk assessment and shielding design of high-voltage and high-power spacecraft on geosynchronous orbit, and is also suitable for providing a feasible calculation verification scheme for the design of improving the dielectric's anti-internal charge performance from the perspective of dielectric material modification, which is technologically advanced.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

FIG1 is a flow chart of a method for assessing the risk of internal electrification in a geostationary orbit spacecraft medium provided by an embodiment of the present invention;

FIG2 is a schematic diagram of an overall technical solution of a method for assessing the risk of internal electrification in a synchronous orbit spacecraft medium provided by an embodiment of the present invention;

3 is a schematic diagram showing the variation of GEO electron integrated flux with fo y and fsc according to an embodiment of the present invention;

FIG4 is a schematic diagram showing a comparison between the calculated value of the GEO orbit electron integrated flux calculated by the FLUMIC3 model provided in an embodiment of the present invention and the “worst case recommended by NASA”;

5 is a schematic diagram of a simulation of dielectric electron radiation in a GEO environment and a simulation diagram of an electron radiation process in Geant4 provided by an embodiment of the present invention;

6 is a calculation result of the charge deposition rate in a modified polyimide (PI) sample at different shielding thicknesses under a GEO environment provided by an embodiment of the present invention;

FIG7 is a fitting diagram of segmented conductivity test results of two polyimide (PI) samples provided in an embodiment of the present invention;

8 is a schematic diagram of the DC breakdown field strength test results (Weibull distribution) of micro- and nano-zinc oxide-modified polyimide samples provided in an embodiment of the present invention;

9 is a schematic diagram of a method for applying a working voltage to a polyimide (PI) sample provided in an embodiment of the present invention;

FIG. 10 is a calculation result of the maximum value of the internal electric field strength of a polyimide sample under a GEO electron radiation environment at different aluminum shielding layer thicknesses and different operating voltages provided by an embodiment of the present invention.

Embodiments of the present invention

In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

In view of the problems existing in the prior art, the present invention provides a method, system and terminal for assessing the risk of internal charging in a synchronous orbit spacecraft medium. The present invention is described in detail below with reference to the accompanying drawings.

In order to enable those skilled in the art to fully understand how to implement the present invention in detail, this section is an explanatory embodiment that expands and describes the technical solution of the claims.

As shown in FIG1 , the method for assessing the risk of internal electrification of a medium in a synchronous orbit spacecraft provided by an embodiment of the present invention comprises the following steps:

S101, construct the geosynchronous orbit environment electron flux model, and introduce the calculated GEO electron flux into Geant4 to simulate the dielectric electron radiation process;

S102, comprehensively analyze shielding factors and find out the key factors of internal charge deposition rate and dose rate of the medium under different shielding conditions under GEO environmental electron radiation;

S103, constructing a three-dimensional charge transport model according to the dielectric parameter measurement of the medium, and then constructing different three-dimensional charge transport model equation groups in combination with the working voltage and the grounding method of the sample;

S104, using a finite element method to solve the corresponding three-dimensional charge transport equations to obtain the electric field intensity distribution in the medium under the corresponding working condition;

S105, comparing the maximum value of the internal electric field strength with the breakdown strength field of the medium to determine whether there is an electrostatic discharge risk under the corresponding working condition.

As a preferred embodiment, as shown in FIG. 2 , the method for assessing the risk of internal electrification in a synchronous orbit spacecraft medium provided by the embodiment of the present invention specifically includes the following steps:

1. Construction of Geosynchronous Orbit (GEO) Environmental Electron Flux Model

In order to accurately calculate the internal electric field characteristics of polyimide samples in the GEO environment, a sufficiently accurate GEO environment electron flux model is first required. Since the occurrence of electrostatic discharge is usually related to the enhancement of the electron flux in the space environment, the standard average flux model AE8 is no longer applicable, and a model that takes flux enhancement into account is needed. The FLUMIC model was built to meet this demand. It is an empirical model built based on actual observational data and has been updated to the third generation, FLUMIC3. It updates the outer belt model based on observational data from satellites such as GEOS/SEM and STRV-1b/REM and models the electron flux in the inner radiation belt. It takes into account the seasonal and annual changes in the high-energy electron flux and constructs high-energy electron flux enhancement events. It is currently the most accurate model for describing the electron flux in the GEO environment.

The outer radiation belt model in the FLUMIC energy spectrum model is as follows:

Taking into account the solar cycle and annual variations, in the outer radiation belt ( L > 2.5), the electron flux will be a function of fsc , foy , L and E :

Functions of the solar cycle: (1)

Where: fsc represents the normalized value of the solar activity cycle, which is 0 in the year of solar minimum activity.

Functions about seasons:

(2)

Where: foy represents the normalized value of the date in a year, with January 1 as the starting point.

Functions about energy: (3)

in:

Functions about L: (4)

Where: L is the distance to the center of the Earth.

Based on the FLUMIC model, the present invention calculates the variation of electron flux greater than 2 MeV with foy and fsc in the GEO environment, and the results are shown in FIG3 .

The calculation results show that when fsc = 0.85, foy = 0.70, the electron flux has a maximum value of 8.05×10 ⁸ m ^-2 s ^-1 sr ^-1 . NASA observation results show that in the GEO environment, electrons with energy greater than 3MeV are not enough to cause the deep charge problem of the medium due to the small electron flux. Generally, the deep charge of the medium considers electrons with energy of 0.1~3MeV. Therefore, the present invention further calculates the electron flux with energy in the range of 0.1~3MeV in the GEO environment according to the FLUMIC3 model, and compares it with the worst case recommended by NASA. The results are shown in Figure 4.

By comparison, it can be seen that the GEO environmental electron flux calculated by the present invention is slightly smaller than the worst case recommended by NASA, but the distribution trend is basically the same.

2. Construction of calculation model of electric field in dielectric under electron radiation

(1) Simulation of electron radiation process

This scheme uses an electron radiation program developed based on Geant4 to simulate the interaction process between high-energy electrons and samples. The overall model is shown in Figure 5.

The dielectric electron radiation process in the GEO environment is shown in Figure 5.

Step 1: Construct the sample model and shielding layer model;

Construct the corresponding sample and shielding layer model in Geant4. In this example, a disc sample model with a diameter of 10 cm and a thickness of 1 mm is constructed based on the actual size of the polyimide (PI) sample. The whole is placed in a vacuum environment. Considering the actual situation, a shielding layer is constructed 10 cm to the left of the sample. The shielding layer material is aluminum, with a size of 15 cm × 15 cm, and the thickness can be parameterized and adjusted according to the actual situation.

Step 2: Construct an electron radiation source model and calculate relevant radiation parameters;

The result calculated by the FLUMIC3 model introduced in Scheme 1 is the integrated flux of electrons in the GEO environment. In this analysis, the electrons are set to be incident perpendicular to the sample plane, so the integrated flux of electrons needs to be converted to the vertical direction first. The electron source is set to a circular plane source with a radius of 6 cm, placed 20 cm to the left of the sample, and incident perpendicular to the sample surface from left to right. At the same time, the electrons are set to be emitted in an energy spectrum sampling mode; the number of simulated incident electrons is 3×10 ^6. During the electron radiation process, the circular lines in Figure 5 represent the trajectory of the incident electrons, and the square lines represent the trajectory of the photons excited during the collision process. The sample model is set as a detector and divided into 100*100*10 volume elements to collect and record the charge deposition and energy deposition data at each position during the radiation process.

Step 3: Calculation result processing

After the calculation is completed, the calculation result needs to be converted to a specific beam current density to obtain the corresponding charge deposition rate in the sample under the corresponding radiation conditions ( ) and dose rate ( )distributed.

The conversion method is as follows:

Assume that the number of incident electrons is N ; the incident electron beam current density is J ₀ , A/m ² , and the electron source area is A ₀ , m ² ; then the virtual radiation time T is: (s)

Where e _q is the electron charge (1.6×10 ^-19 C), which corresponds to the charge deposition rate in the medium under the actual beam current: (C/m ³ ·s)

The dose rate in the medium is: (rad/s)

Example:

In this example, the charge deposition rate in the sample with different aluminum shielding thicknesses in the GEO electronic environment was first calculated according to the above method. The calculation results are shown in Figure 6.

From the calculation results in Figure 6, it can be seen that increasing the shielding thickness can effectively reduce the amount of electron penetration and thus reduce the charge deposition rate in the medium. For example, when there is no shielding, the maximum charge deposition rate in the sample is 2.02× ^10-4 C/ ^m3 ·s; when the thickness of the aluminum shielding layer is 1mm, the maximum charge deposition rate in the sample is 1.83× ^10-5 C/ ^m3 ·s, which is a significant decrease; when the thickness of the aluminum shielding increases to 3mm, the maximum charge deposition rate in the sample is only 9.17× ^10-6 C/ ^m3 ·s, achieving an order of magnitude attenuation. At the same time, it can be seen that the charge deposition characteristics of the medium in the actual space radiation environment are quite different from the monoenergetic electron incidence results. It is no longer deposited at a specific depth, but is dispersed at different depths inside the medium. This is because the initial energy and beam density of the electrons contained in the actual environment are different. Electrons of different energies experience energy loss and transfer during the interaction with the dielectric material, and will eventually be deposited at different depths of the sample. In this way, the distribution of electrons in the sample appears to be more dispersed and random, and the charge accumulation may be more concentrated in some areas.

(2) Calculation process of the electric field in the medium under electron radiation

Step 1: Constructing the charge transport equation in the medium

The charge transport equations inside the medium are as follows:

The equations are Poisson's equation, current continuity equation and Ohm's law from top to bottom. E is the electric field strength, V/m (the quantity to be determined); is the net charge density in the medium, C/m ³ , (to be determined); ε is the dielectric constant of the medium, F/m, (using the test result in step 1); J is the net current density, A/m ² , (to be determined); is the charge deposition rate in the medium, C/m ³ ·s; is the conductivity related to the electric field, S/m.

In the numerical calculation model of deep charge and discharge of dielectrics, the Poole-Frankel effect is often used to simulate the conductivity related to the electric field, but there are also technical indicators that the Schottky effect and the Poole-Frankel effect in polyimide cannot perfectly explain its charge transport process. Based on this, this scheme proposes a segmented conductivity calculation method based on the measured data of the dielectric, mainly based on the nonlinear conductivity characteristics measurement data of the modified sample.

This scheme will perform segmented fitting of the conductivity of the sample according to the measured conductivity data and the size of the electric field strength. From the experimental data, it is found that when the electric field strength is less than 1kV/mm, the conductivity does not change significantly with the electric field, which is set as the "low field zone" here. The intrinsic conductivity of the sample measured is used in the low field zone; when the field strength is greater than 1kV/mm, the conductivity will increase with the increase of the electric field strength. This area is divided into two parts with the nonlinear conductivity threshold as the dividing point, where the electric field from 1kV/mm to the mutation point threshold is set as the "low growth rate zone", and the area after the mutation point is set as the "nonlinear growth zone". The conductivity related to the electric field is divided into three sections.

The overall design is as follows:

An example of conductivity fitting results is shown in Figure 7.

As shown in FIG7 , the segmented conductivity fitting results of the 1 wt % micron zinc oxide/polyimide modified sample and the 3 wt % micron zinc oxide/polyimide modified sample are given respectively.

Step 2: Calculation process of the electric field inside the medium

The electric field calculation model adopts the charge transport model given in step 1, in which the conductivity of the sample is processed by segmented fitting based on the test data. The charge transport model is solved by COMSOL software based on the finite element method. Since the transport equation needs to be modified and reconstructed according to the fitting parameters, the present invention does not use the inherent module given in COMSOL to calculate the electric field, but uses the partial differential equation interface in the mathematical module to define the set of equations to be solved. The present invention uses a general form of partial differential equations, and its specific structure is as follows:

;

The coefficients of this partial differential equation can be modified according to the charge transport model equation group, and Poisson's equation can also be rewritten from this equation.

At the same time, the specific working conditions that need to be considered in the simulation calculation process of the present invention mainly include the grounding state and grounding position of the sample, the amplitude of the working voltage, the applied position and other factors, which correspond to the initial state and boundary conditions of the partial differential equation group. In COMSOL, various initial states can be set by modifying the initial conditions of the custom equations and adding Dirichlet boundary conditions.

It is necessary to first use Geant4 programming to simulate the electron radiation process according to the set radiation parameters, and then introduce the two key parameters of charge deposition rate and dose rate at each position in the sample into the calculation model. The present invention uses the interpolation method to import them into COMSOL. Then, the grounding conditions and working voltage are set according to the actual working conditions of the sample, and then the sample model is meshed, the radiation time is set, and the MUMPS type solver based on LU decomposition is selected for solution calculation, and finally the internal electric field distribution of the sample within the set radiation time under the actual working conditions can be obtained.

3. Risk assessment of dielectric electrostatic discharge under electronic radiation

Step 1: Calculate the maximum electric field intensity in the medium under the corresponding electron radiation scenario through schemes 1 and 2.

Step 2: Determine the DC breakdown field strength of the sample.

This scheme uses a breakdown test platform to carry out a DC withstand voltage test on the modified sample. The test electrode is a ball-to-ball electrode, which is placed in insulating oil to prevent surface flashover.

The test data was processed using the Weibull distribution method, and the formula is as follows:

Where: P ( E ) is the probability of cumulative failure; E is the breakdown strength; α is the shape parameter, which can be used to evaluate the dispersion of the breakdown voltage; E _b is the breakdown field strength when the breakdown probability is 63.28%, called the characteristic breakdown field strength. Taking the logarithm of both ends of the above formula can be obtained:

Example:

The test results of the micro-nano zinc oxide modified polyimide sample after DC breakdown field strength treatment are shown in Figure 8.

Step 3: Comparative Evaluation

Compare the maximum value of the internal electric field of the sample under the corresponding radiation scenario calculated in step 1 with the DC breakdown field strength of the sample measured in step 2. If the maximum value of the internal electric field of the sample is greater than the DC breakdown field strength, it is considered that there is an electrostatic discharge risk; if the maximum value of the internal electric field of the sample is less than the DC breakdown field strength, it is considered that there is no electrostatic discharge risk.

Step 4: Shielding design optimization

According to the results of the comparative evaluation in step 3, if there is an electrostatic discharge risk in the spacecraft medium, the shielding layer design needs to be readjusted. The shielding layer material or thickness can be adjusted in Scheme 1 for simulation calculation, and then the electric field inside the medium is calculated by the method in Scheme 2, and finally the electrostatic discharge risk of the medium is evaluated by the method in Scheme 3. Multiple adjustments and repeated calculations can be performed until the maximum value of the internal electric field strength of the medium is less than the breakdown field strength of the medium under the set electron radiation conditions. The shielding design at this time is taken as the safe shielding threshold, that is, the shielding layer thickness or shielding material density at this time is the minimum requirement.

The system for assessing the risk of internal electrification of a medium in a synchronous orbit spacecraft provided by an embodiment of the present invention comprises:

The dielectric electron radiation module simulation is used to build the geosynchronous orbit environment electron flux model. The calculated GEO electron flux is introduced into Geant4 to simulate the dielectric electron radiation process.

The electric field intensity distribution determination module is used to construct a three-dimensional charge transport model equation group, and use the finite element method to solve the corresponding three-dimensional charge transport equation group to obtain the electric field intensity distribution in the medium under the corresponding working conditions;

The electrostatic discharge risk assessment module is used to compare the maximum internal electric field strength with the breakdown strength field of the medium to determine whether there is an electrostatic discharge risk under the corresponding working conditions.

In order to prove the creativity and technical value of the technical solution of the present invention, this section provides application examples of the claimed technical solution on specific products or related technologies.

Taking polyimide, a typical spacecraft dielectric, as an example, the scheme of the present invention is used to calculate the maximum value of the electric field in the polyimide sample under the geosynchronous orbit electron radiation environment when the aluminum shielding thickness is 0 to 5 mm and the working voltage is 100 V, 500 V, 1000 V, 2000 V, 3000 V, and 5000 V, wherein the voltage application method is shown in FIG9 .

The electric field calculation results are shown in Figure 10. The following conclusions can be drawn:

When the working voltage is in the range of 100 V to 5000 V and the four voltage application methods in this example are applied, if the electrostatic discharge threshold is set to 2×10 ⁷ V/m, the minimum required aluminum shielding thickness should be 2 mm; for more demanding environments, if 1×10 ⁷ V/m is used as the assessment threshold, the minimum required aluminum shielding thickness should be 4 to 5 mm.

It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. It can be understood by a person of ordinary skill in the art that the above-mentioned devices and methods can be implemented using computer executable instructions and/or contained in a processor control code, such as a carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. Such code is provided on the carrier medium. The device and its modules of the present invention can be implemented by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, and can also be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims (10)

1. A method for assessing the risk of internal electrification of a synchronous orbit spacecraft medium is characterized in that the method comprises: constructing a geosynchronous orbit environment electron flux model, then introducing the GEO electron flux calculated by the geosynchronous orbit environment electron flux model into Geant4 to simulate the medium electron radiation process, and comprehensively considering the shielding factor to obtain the key factors of the internal charge deposition rate and dose rate of the medium under different shielding under the GEO environment electron radiation; constructing a three-dimensional charge transport model according to the dielectric parameter measurement of the medium, and then constructing different three-dimensional charge transport model equation groups in combination with the working voltage and the grounding method of the sample; using the finite element method to solve the corresponding three-dimensional charge transport equation group to obtain the distribution of the internal electric field strength of the medium under the corresponding working condition; comparing the maximum value of the internal electric field strength with the breakdown strength field of the medium to judge whether there is an electrostatic discharge risk under the corresponding working condition.
2. The method for assessing the risk of internal electrification of a medium in a synchronous orbit spacecraft according to claim 1, wherein the method for assessing the risk of internal electrification of a medium in a synchronous orbit spacecraft comprises the following steps:

   Step 1: Construction of the geosynchronous orbit environment electron flux model;

   Step 2: constructing a calculation model of the electric field in the medium under electron radiation;

   Step 3: Risk assessment of dielectric electrostatic discharge under electronic radiation.
3. The method for assessing the risk of internal electrification of a geosynchronous orbit spacecraft medium according to claim 2, wherein the construction of the geosynchronous orbit environment electron flux model in step 1 comprises:

   The FLUMIC3 (Flux Model for Internal Charging) model is used to construct the electron flux environment of the synchronous orbit:

   The outer radiation belt model in the FLUMIC energy spectrum model is as follows:

   Taking into account the solar cycle and annual variations, for the outer radiation belt L > 2.5, the electron flux will be a function of fsc , foy , L and E :

   Functions of the solar cycle: ;

   Where fsc represents the normalized value of the solar activity cycle, which is 0 in the year of minimum solar activity;

   Functions about seasons: ;

   In the formula, foy represents the normalized value of the date in a year, with January 1 as the starting point;

   Functions about energy: ;

   in, ;

   Functions about L: ;

   Where L is the distance to the center of the Earth.
4. The method for assessing the risk of internal electrification of a medium in a synchronous orbit spacecraft according to claim 2, wherein the construction of a calculation model for the internal electric field of the medium under electron radiation in step 2 comprises:

   (1) Simulation of electron radiation process: The electron radiation program developed based on Geant4 is used to simulate the interaction between high-energy electrons and samples;

   (2) The process of calculating the electric field in the medium under electron radiation: including the construction of the charge transport equation in the medium and the calculation of the electric field in the medium.
5. The method for assessing the risk of internal electrification in a geostationary orbit spacecraft medium according to claim 4, wherein the simulation of the electron radiation process in step (1) comprises:

   1) Construct the corresponding sample model and shielding layer model in Geant4;

   2) Construct an electron radiation source model and calculate relevant radiation parameters;

   The result calculated by the FLUMIC3 model is the integrated flux of electrons in the GEO environment. The integrated flux of electrons is converted to the vertical direction. During the analysis, the electrons are set to be incident perpendicular to the sample plane. The electron source is set to a circular plane source with a radius of 6 cm, which is placed 20 cm to the left of the sample and incident perpendicular to the sample surface from left to right. At the same time, the electrons are set to be emitted in the energy spectrum sampling mode. The number of simulated incident electrons is 3×10 ⁶ .

   3) Calculation result processing

   After the calculation is completed in Geant4, the statistical charge deposition number En and energy deposition Eg are obtained _, which need to be converted into the charge deposition rate under the set electron beam current density _. and dose rate , the conversion method is as follows:

   When the number of incident electrons is N , the incident electron beam current density is J ₀ , A/m ² , and the electron source area is A ₀ , m ² , then the virtual radiation time T is: s;

   Where, e _q is the electron charge, which is set to 1.6×10 ^-19 C; the charge deposition rate in the medium under the actual beam current is: C/m ³ ·s;

   The dose rate in the medium is: rad/s;

   The process of calculating the electric field in the medium under electron radiation in step (2) includes:

   1) Construction of charge transport equation in medium

   The charge transport equations inside the medium are as follows:

   ;

   The charge transport equations are Poisson's equation, current continuity equation and Ohm's law from top to bottom; where E is the electric field intensity, in V/m; is the net charge density in the medium, in C/m ³ ; ε is the dielectric constant of the medium, in F/m; J is the net current density, in A/m ² ; is the charge deposition rate in the medium, in C/m ³ ·s; is the conductivity related to the electric field, unit S/m;

   Based on the nonlinear conductivity characteristics of the modified sample, the conductivity of the sample is segmented and fitted according to the electric field strength according to the measured conductivity data. It is found from the test data that when the electric field strength is less than 1kV/mm, the conductivity does not change significantly with the electric field, and it is set as a low field area. In the low field area, the intrinsic conductivity of the sample is used. When the field strength is greater than 1kV/mm, the conductivity will increase with the increase of the electric field strength. The area is divided into two parts with the nonlinear conductivity threshold as the dividing point, where the electric field from 1kV/mm to the mutation point threshold is set as a low growth rate area, and the area after the mutation point is set as a nonlinear growth area.

   The overall design is as follows: ;

   2) Calculation process of electric field in dielectric medium

   The electric field calculation model adopts the charge transport model, and the conductivity of the sample is processed by piecewise fitting based on the test data; the charge transport model is solved by COMSOL software based on the finite element method, and the partial differential equation interface in the mathematical module is used to customize the equation group to be solved. The coefficients of this partial differential equation and Poisson's equation are modified according to the charge transport model equation group; the partial differential equation is: ; ;

   During the simulation calculation process, the specific working conditions are analyzed, including the grounding state, grounding position, amplitude and application position factors of the working voltage of the sample, corresponding to the initial state and boundary conditions of the partial differential equation group; various initial states are set in COMSOL by modifying the initial conditions of the custom equations and adding Dirichlet boundary conditions; Geant4 programming is used to simulate the electron radiation process according to the set radiation parameters, and then the charge deposition rate and dose rate at each position in the sample are introduced into the calculation model, and then imported into COMSOL using the interpolation method; the grounding conditions and working voltage are set according to the actual working conditions of the sample, and then the sample model is meshed and the radiation time is set; the MUMPS type solver based on LU decomposition is selected for solution calculation, and finally the internal electric field distribution of the sample within the set radiation time under the actual working conditions is obtained.
6. The method for evaluating the risk of charged dielectric in a synchronous orbit spacecraft according to claim 2, wherein the risk evaluation of dielectric electrostatic discharge under electron radiation in step 3 comprises:

   (1) Calculate the maximum electric field intensity in the medium under the corresponding electron radiation scenario;

   (2) Determine the DC breakdown field strength of the sample;

   The modified sample was subjected to a DC withstand voltage test using a breakdown test platform. The test electrode was a ball-ball electrode placed in insulating oil. The test data was processed using the Weibull distribution method, and the formula is as follows: ;

   Where, P ( E ) is the probability of cumulative failure; E is the breakdown strength; α is the shape parameter, which is used to evaluate the dispersion of the breakdown voltage; E _b is the breakdown field strength when the breakdown probability is 63.28%, which is called the characteristic breakdown field strength;

   Taking the logarithm of both ends of the test data processing formula, we get: ;

   (3) Comparative evaluation

   Compare the calculated maximum value of the internal electric field of the sample under the corresponding radiation scenario with the measured DC breakdown field strength of the sample. If the maximum value of the internal electric field of the sample is greater than the DC breakdown field strength, it is considered that there is an electrostatic discharge risk. If the maximum value of the internal electric field of the sample is less than the DC breakdown field strength, it is considered that there is no electrostatic discharge risk.

   (4) Shielding layer design optimization

   According to the results of the comparative evaluation in step (3), if there is an electrostatic discharge risk in the spacecraft medium, the shielding layer design is readjusted; in step 1, the shielding layer material or thickness is adjusted for simulation calculation, and then the electric field inside the medium is calculated, and finally the electrostatic discharge risk of the medium is evaluated; through multiple adjustments and repeated calculations until the maximum value of the internal electric field strength of the medium under the set electron radiation conditions is less than the breakdown field strength of the medium, the shielding design is taken as the safe shielding threshold, and the shielding layer thickness or shielding material density is taken as the minimum requirement.
7. A system for assessing the internal electrification risk of a synchronous orbit spacecraft medium using the method for assessing the internal electrification risk of a synchronous orbit spacecraft medium according to any one of claims 1 to 6, characterized in that the system for assessing the internal electrification risk of a synchronous orbit spacecraft medium comprises:

   The dielectric electron radiation module simulation is used to build the geosynchronous orbit environment electron flux model. The calculated GEO electron flux is introduced into Geant4 to simulate the dielectric electron radiation process.

   The electric field intensity distribution determination module is used to construct a three-dimensional charge transport model equation group, and use the finite element method to solve the corresponding three-dimensional charge transport equation group to obtain the electric field intensity distribution in the medium under the corresponding working conditions;

   The electrostatic discharge risk assessment module is used to compare the maximum internal electric field strength with the breakdown strength field of the medium to determine whether there is an electrostatic discharge risk under the corresponding working conditions.
8. A computer device, characterized in that the computer device includes a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method for assessing the risk of internal charging of a synchronous orbit spacecraft medium as described in any one of claims 1 to 6.
9. A computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the processor executes the steps of the method for assessing the risk of internal charging of a medium in a synchronous orbit spacecraft as described in any one of claims 1 to 6.
10. An information data processing terminal, characterized in that the information data processing terminal is used to implement the synchronous orbit spacecraft medium charge risk assessment system as described in claim 7.