Ultra-low orbit satellite configuration and layout design method

Abstract

The invention discloses an ultra-low orbit satellite configuration and layout design method, which comprises the following steps of: firstly, determining layout constraint characteristics of equipment carried on each satellite according to task requirements; under the layout constraint characteristics, different satellite body configurations are adopted to carry out preliminary layout on equipment carried on each satellite, preliminary windward surface areas and crosswind surface areas of the different satellite body configurations are obtained, and a final satellite body configuration is determined by comparing effective surface-to-volume ratios; on the basis, the final windward side area is determined by comparing the windward side design area with the theoretical optimal windward side area; and carrying out specific layout on the on-satellite carrying equipment to obtain a final on-satellite carrying equipment layout form and a final satellite body configuration length. According to the method, a feasible guidance method is provided for key design characteristics such as selection of low-resistance configuration and determination of the optimal windward side from related characteristics of equipment, so that the configuration and layout of the ultra-low orbit satellite which can most effectively adapt to actual task requirements are designed.

Description

Technical Field

[0001] The present invention relates to the field of spacecraft design, and in particular to a method for designing a configuration and layout of an ultra-low-orbit satellite. Background Art

[0002] Ultra-low orbit is located at the near-earth end of the thermosphere. Spacecraft will face many severe space environment problems when operating in ultra-low orbit. Among various space environment problems, the higher atmospheric density of ultra-low orbit has a significant impact on the overall structure of the satellite platform. In ultra-low orbit, the gas collides with the outer surface of the satellite in a free molecular flow state, causing aerodynamic drag on the satellite platform that cannot be ignored. Aerodynamic drag is one of the main sources of disturbance for ultra-low orbit satellites, directly affecting the life and operation attitude of the satellite. How to reduce aerodynamic drag, create a good configuration, and even whether aerodynamic drag can be used is one of the key points in the overall structural design of ultra-low orbit satellites. In the design of ultra-low orbit satellites, although aerodynamic drag reduction design is important, it needs to meet the basic requirements and functions of the satellite as a bearing platform, that is, to meet the strength and stiffness requirements of the main structure of the satellite, meet the requirements of the rationality of the equipment layout, meet the basic design requirements such as the reliable installation surface requirements. Under the influence of the harsh space environment, combined with various design requirements, using engineering thinking, how to achieve the Pareto optimization of the configuration and layout design of ultra-low orbit satellites is a common problem to be solved in the design of ultra-low orbit satellites.

[0003] The current ultra-low orbit satellite design methods, such as CN116842628A "Ultra-low orbit satellite low-drag configuration and layout design method and system", only provide a general design method, and do not provide corresponding solutions for the design methods of some key features; or such as CN115730537A "Ultra-low orbit satellite aerodynamic drag reduction method by coupling geometric configuration and surface characteristics" and CN113591214A "Ultra-low orbit satellite configuration parameter design method", are only based on rarefied aerodynamics, and in principle optimize the drag reduction configuration of the ultra-low orbit satellite configuration's windward surface shape, satellite aspect ratio, diffuse scattering coefficient, etc., and are not combined with engineering practice. They are not regular, systematic and practical design methods. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art and provide a method for designing the configuration and layout of an ultra-low-orbit satellite, combining theory with engineering application, and gradually forming a complete satellite drag reduction configuration and layout plan with engineering implementation conditions from limited known conditions.

[0005] The technical solution of the present invention is: a method for designing a configuration and layout of an ultra-low-orbit satellite, characterized in that it includes:

[0006] S1. Determine the layout constraint characteristics of the equipment on board each satellite according to the mission requirements;

[0007] S2. Under the layout constraint characteristics of the onboard equipment, different satellite body configurations are used to preliminarily layout the onboard equipment, obtain the preliminary windward surface area and crosswind surface area of ​​different satellite body configurations, calculate the effective surface area ratio of different satellite body configurations, and determine the final satellite body configuration by comparing the effective surface area ratios;

[0008] S3. Determine the final windward surface area based on the satellite body configuration;

[0009] S4, according to the satellite body configuration determined by S2 and the windward surface area determined by S3, the onboard equipment of each satellite is specifically arranged to obtain the final onboard equipment layout form and the final length of the satellite body configuration;

[0010] S5. Design the layout of solar panels according to energy demand;

[0011] S6. Determine the outer wall material of the satellite body based on the fitness of free molecules.

[0012] Furthermore, in S2, the effective surface area ratio includes the effective surface area ratio of the windward surface and the effective surface area ratio of the sidewind surface; the effective surface area ratio of the windward surface is the ratio of the windward surface area to the total volume of the equipment carried inside the satellite, and the effective surface area ratio of the sidewind surface is the ratio of the sidewind surface area to the total volume of the equipment carried inside the satellite.

[0013] Furthermore, the effective area ratio is set to: effective area ratio = windward effective area ratio + sidewind effective area ratio / η, where η is the drag coefficient ratio of the windward surface and the sidewind surface; each satellite body configuration is calculated according to the above formula to obtain an effective area ratio, which is compared and the satellite body configuration with the smallest effective area ratio is taken as the final satellite body configuration.

[0014] Further, the S3 includes:

[0015] S31, based on the satellite body configuration and corresponding preliminary layout determined in S2, the windward surface design area is obtained according to the size of the largest profile equipment in the satellite in the windward surface projection direction;

[0016] S32, comparing the designed windward surface area and the theoretical optimal windward surface area of ​​the satellite body configuration, and taking the larger windward surface area between the two as the final windward surface area;

[0017] Furthermore, based on the final satellite body configuration and the correlation between the total aerodynamic drag and the total drag of the satellite instrument, the positive pressure aerodynamic drag, and the shear aerodynamic drag, the correlation between the total aerodynamic drag and the windward surface area of ​​the satellite body configuration is derived and transformed. The windward surface area when the total aerodynamic drag reaches the minimum value in the transformed correlation is taken as the theoretical optimal windward surface area.

[0018] Further, in S3, after performing step S31, step S32 is not performed, and step S4 is performed directly; in S4, according to the satellite body configuration determined in S2 and the windward surface design area determined in S31, the onboard equipment of each satellite is specifically laid out to obtain the layout form of the onboard equipment and the design length of the satellite body configuration; then the design slenderness ratio is calculated according to the design length of the satellite body configuration, and the design slenderness ratio is compared with the theoretical optimal slenderness ratio of the satellite body configuration. If the design slenderness ratio is greater than the optimal slenderness ratio, the windward surface area is enlarged and the design length is reduced under the constant volume condition to achieve the optimal slenderness ratio; if the design slenderness ratio is less than the optimal slenderness ratio, the design slenderness ratio is selected; after determining the slenderness ratio, the final windward surface area and the length of the satellite body configuration are determined; the slenderness ratio is the ratio of the length of the sidewind surface to the characteristic diameter of the windward surface.

[0019] Furthermore, based on the final satellite body configuration and the correlation between the total aerodynamic drag and the total drag of the satellite instrument, the positive pressure aerodynamic drag, and the shear aerodynamic drag, the correlation between the total aerodynamic drag and the slenderness ratio of the satellite body configuration is derived and transformed. The slenderness ratio in the transformed correlation that makes the total aerodynamic drag reach the minimum value under constant volume conditions is taken as the theoretical optimal slenderness ratio.

[0020] Furthermore, in S6, the outer wall surface of the windward side is made of a material with a free molecular fitness of σ1, and the outer wall surface of the lateral side is made of a material with a free molecular fitness of σ2, where σ1≥σ2.

[0021] Furthermore, it also includes S7, simulating and optimizing the design results; the specific method is: verifying through simulation whether the aerodynamic force and aerodynamic moment of the design results meet the design requirements; if they meet, the design is completed; if not, the layout of the onboard equipment is adjusted until the simulation verification results meet the design requirements; among them, if the aerodynamic force does not meet the requirements, the final layout of the onboard equipment is adjusted by increasing the internal effective volume ratio, reducing the exposed area of ​​the satellite surface equipment, locally adding inclined surfaces, and adding conical surfaces; if the aerodynamic moment does not meet the requirements, the final layout of the onboard equipment is adjusted by changing the center of mass position, adding aerodynamic rudders, and adding balance wings.

[0022] Further, in S2, the satellite body is configured as a single prism or a combination of prisms.

[0023] Furthermore, the satellite body is configured as a single prism and is a regular prism.

[0024] The advantages of the present invention compared with the prior art are:

[0025] 1) Through the technical solution of the present invention, the ultra-low-orbit satellite configuration and layout can be systematically designed. Through the easy-to-count related features of the satellite platform's required equipment that restricts the on-board layout, the overall configuration and layout design of the ultra-low-orbit satellite can be gradually completed, which has strong operability. This technical solution not only provides a complete design idea, but also starts from the relevant characteristics of the equipment to find the ultra-low-orbit satellite configuration and layout that can most effectively adapt to the actual mission requirements.

[0026] 2) The present invention provides practical guidance methods for key design features, such as the selection of low-drag configuration, the relationship between equipment layout and configuration, and the determination of the optimal windward surface. For configuration selection, it is proposed to determine the satellite body configuration by comparing the effective surface area ratio, where the effective surface area ratio can be regarded as the relationship between the layout and resistance of equal equipment under the same installation requirements in different configurations, and can also be regarded as the drag reduction efficiency of different configurations under specific mission requirements; for determining the windward surface area, it is proposed to obtain the windward surface design area according to the size of the largest contour equipment in the satellite in the windward surface projection direction, and then compare it with the optimal windward surface area to determine the final windward surface area; the design method is more regular.

[0027] 3) The present invention not only designs the theoretically optimal aerodynamic resistance configuration from the appearance, but also considers the correlation between the satellite body configuration and the equipment characteristics. Through analysis, the theoretical optimal configuration such as a cylinder often limits the installation of the equipment and cannot provide an effective direct installation surface. The increase in the transition installation surface will increase the invalid mass and invalid volume, resulting in that although the volume resistance of the theoretical optimal configuration is better, when the same amount of equipment is installed in engineering applications, the volume or surface area increases due to the large invalid volume, which is not as good as the theoretical non-optimal configuration. By reasonably comparing different configurations to form a design scheme with high applicability, this technical scheme embodies a complete engineering design method from initial design and detailed design to design verification and design optimization, and is more systematic. It can more effectively obtain a more optimal configuration and layout in practice, rather than just a theoretically optimal configuration and layout. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 , a flow chart of the ultra-low-orbit satellite configuration and layout design method of the present invention;

[0029] Figure 2 , schematic diagram of the configuration layout of the regular quadrangular prism body in an embodiment of the present invention;

[0030] Figure 3 , schematic diagram of the configuration layout of the regular hexagonal prism body in an embodiment of the present invention;

[0031] Figure 4 , schematic diagram of the configuration layout of the regular octagonal prism body in an embodiment of the present invention;

[0032] Figure 5 , a schematic diagram of the configuration layout of the cylindrical body in an embodiment of the present invention;

[0033] Figure 6 , the relationship between the aerodynamic drag and the cross-sectional characteristics of the windward surface under the condition of constant volume of the regular tetrahedral body configuration;

[0034] Figure 7 , the relationship between the aerodynamic drag and the slenderness ratio of the regular tetrahedral body configuration;

[0035] Figure 8 , Relationship between resistance coefficient and free molecular fitness at different ambient temperatures.

[0036] Reference numerals:

[0037] 1. Propulsion system related equipment; 2. Payload related equipment; 3. Attitude and orbit control related equipment; 4. Energy and control related equipment; 5. Electronic equipment related to onboard processors; 6. Antenna control related equipment; 7. Filter related equipment. DETAILED DESCRIPTION

[0038] The method provided in this embodiment is as follows: Figure 1 As shown, it mainly includes:

[0039] Step 1: Determine the layout constraint characteristics of the equipment on board each satellite according to the mission requirements

[0040] Ultra-low-orbit satellites need to carry different onboard equipment due to different mission requirements. It is impossible to list all situations one by one. In order to better explain the technical solutions, reasonable and universal settings are made for the design requirements.

[0041] In this embodiment, the onboard equipment includes propulsion system related equipment 1, payload related equipment 2, attitude and orbit control related equipment 3, energy and control related equipment 4, onboard processor related electronic equipment 5, antenna control related equipment 6, and filter related equipment 7. The above equipment does not cover all the necessary equipment on the satellite, but because of their significant size differences in outer contour size characteristics, they have different technical requirements for installation and have certain layout representativeness, so as to explain the configuration and layout method of ultra-low orbit satellites under different mission requirements.

[0042] The features of the equipment required to be carried by the satellite platform that restrict the onboard layout include the equipment's volume, shape, characteristic dimensions, installation requirements, installation surface size, field of view, magnetic compatibility distance, and other features related to the requirements for equipment layout on the satellite platform. These features are easier to obtain through analysis of mission requirements.

[0043] Step 2: Under the layout constraint characteristics of the onboard equipment, different satellite body configurations are used to preliminarily layout the onboard equipment, obtain the preliminary windward surface area and crosswind surface area of ​​different satellite body configurations, calculate the effective surface area ratio of different satellite body configurations, and determine the final satellite body configuration by comparing the effective surface area ratio.

[0044] First, based on the layout constraint characteristics of the onboard equipment obtained in step 1, different satellite body configuration schemes are selected for preliminary onboard layout, focusing on the layout of the onboard equipment.

[0045] This embodiment selects regular quadrangular prism, regular hexagonal prism, regular octagonal prism and cylindrical body configuration for preliminary layout, such as Figure 2 to Figure 5 It should be noted that, according to different task requirements, the body configuration can also be a non-regular prism; or it can be a combination of multiple prisms, and the present method is also applicable.

[0046] The total aerodynamic drag on a very low-orbit satellite in orbit is the sum of the drag on the windward side and the crosswind side, which can be further decomposed into the sum of the product of the satellite's dynamic pressure and the corresponding surface drag coefficient and area, that is:

[0047] F=F p +F τ =qC Dp S p +qC Dτ S τ

[0048] F is the total aerodynamic resistance, F p is the windward resistance (i.e. positive pressure aerodynamic resistance), F τ is the crosswind resistance (i.e. shear aerodynamic resistance), q is the dynamic pressure, C Dp is the positive pressure resistance coefficient, C Dτ is the shear resistance coefficient, S p is the windward surface area, C Dτ is the crosswind surface area.

[0049] In order to reduce the total aerodynamic drag of ultra-low-orbit satellites, the present invention proposes to use the effective surface area ratio as the basis for selecting the drag reduction of the body configuration. The effective surface area ratio includes the effective surface area ratio of the windward surface and the effective surface area ratio of the sidewind surface; the effective surface area ratio of the windward surface is the ratio of the area of ​​the windward surface to the total volume of the equipment carried inside the satellite, and the effective surface area ratio of the sidewind surface is the ratio of the area of ​​the sidewind surface to the total volume of the equipment carried inside the satellite.

[0050] The preliminary on-board layout of equipment with the same installation requirements for different body configurations is carried out, and the size characteristics of different body configurations that can accommodate the same equipment are compared to obtain the preliminary windward surface area and crosswind surface area of ​​different satellite body configurations, thereby calculating the effective surface area ratio of different satellite body configurations. By comparing the effective surface area ratios, the satellite body configuration is determined.

[0051] In this embodiment, the volumes of the parts, cables, connectors, and fixtures necessary for the installation and normal operation of the equipment are taken into consideration, and the parameters of different configurations are calculated as follows:

[0052] Table 1 Parameters of different body configurations

[0053]

[0054] The effective area ratio of the windward side of the regular quadrangular prism is the smallest, and the effective area ratios of other configurations relative to the regular quadrangular prism are: 17.8% (regular hexagonal prism), 18.5% (regular octagonal prism), 22.9% (cylinder); the effective area ratio of the sidewind side of the cylinder is the smallest, and the effective area ratios of other configurations relative to the cylinder are: 7.8‰ (regular octagonal prism), 18.8‰ (square column), 28.5‰ (regular hexagonal prism). Under the same environmental conditions, the four configurations have different effective areas. p Change ratio F τ The larger it is, the greater the impact on the aerodynamic drag of the main body. Therefore, it is judged that a regular tetrahedron can be selected as the main body configuration.

[0055] Preferably, the effective surface area ratio=windward surface effective surface area ratio+crosswind surface effective surface area ratio / η; η is the ratio of the positive pressure drag coefficient to the shear drag coefficient, which can be determined according to different working conditions.

[0056] In this embodiment, the working condition where η is 100 is used as the effective area ratio for calculation, and it can be obtained that the effective area ratio of the regular tetrahedron is 1.7272, the effective area ratio of the regular hexagonal prism is 2.0087, the effective area ratio of the regular octagonal prism is 2.0155, and the effective area ratio of the cylinder is 2.0843. Therefore, the regular tetrahedron is selected as the main body configuration.

[0057] In addition, considering the actual engineering applications, the equipment inside the satellite is generally in the shape of a prism, cylinder or sphere with a bracket, a disc, etc. From the perspective of reasonable layout, their common characteristics basically require a regular and flat installation plane. Under the conditions of fixed volume and fixed length, as the number of sides of the cross section increases, the characteristic scale of the installation plane provided by a single surface inside the spacecraft is relatively reduced, which will result in larger equipment being unable to be directly installed on the plane provided by the configuration. To install large equipment on a small installation plane, it is necessary to add a transition plane inside. The increase in transition planes not only increases the additional structural mass, but also increases the invalid volume caused by the need for reasonable installation, that is, the space that cannot be used inside the satellite due to installation. Therefore, the number of direct mounting surfaces and transition mounting surfaces can also be considered as the basis for selecting the body configuration.

[0058] Step 3: Determine the windward surface area based on the satellite body configuration

[0059] Step 3.1: Based on the satellite body configuration and corresponding preliminary layout determined in step 2, the windward surface design area is obtained according to the size of the largest profile equipment in the satellite in the windward surface projection direction.

[0060] The main body configuration is inseparable from the relevant features of the equipment on the satellite. Therefore, when deciding on the size features of the main body configuration, it is necessary to judge based on the relevant features of the equipment. After the initial layout of the equipment on the satellite, determine the maximum outline of the equipment projected on the windward surface as the limit of the design area of ​​the windward surface of the main body configuration. The maximum outline size does not only refer to the size of the characteristic direction of the windward surface of a certain equipment, but also includes the brackets, cables, and operating space reserved when the equipment is installed, as well as the necessary configuration area of ​​the characteristic direction caused by the necessary connection with other equipment.

[0061] In the embodiment, the maximum outline dimension of the propulsion system-related equipment 1 in the characteristic direction of the windward surface is regarded as the basis for limiting the design area of ​​the windward surface of the body configuration.

[0062] Step 3.2: Compare the designed windward surface area with the theoretical optimal windward surface area of ​​the satellite body configuration, and take the larger windward surface area as the final windward surface area.

[0063] The total aerodynamic drag of the body configuration of the regular quadrangular prism in this embodiment is the sum of the total drag of the satellite instrument and the drag of the windward and side wind surfaces of the body configuration:

[0064]

[0065] F0 is the total resistance of the satellite equipment, η is the ratio of the positive pressure resistance coefficient to the shear resistance coefficient, and V represents the volume that the body configuration can provide. Similar expressions can be listed for different body configurations, including combined body configurations.

[0066] According to the above formula, the total aerodynamic resistance F and the positive pressure aerodynamic resistance F can be obtained. p The windward surface area S of the main body configuration p and characteristic diameter d p Relationship curve, characteristic diameter refers to the diameter of the inscribed circle of a regular polygon. In this embodiment, the characteristic diameter of a regular quadrangular prism is the side length of its cross section. Figure 6 As shown, it can be seen that the positive pressure resistance F p The windward surface area S of the main body configuration p , characteristic diameter d p There is a positive correlation. If the body configuration is designed based on the positive pressure resistance alone, the windward surface area S should be minimized. p Or characteristic diameter d p However, from the total aerodynamic resistance F and the windward surface area S p , characteristic diameter d p The lowest point can be obtained on the curve relationship, that is, F min Point, corresponding to which we can get the theoretical optimal windward surface diameter, we can also get the theoretical optimal windward surface area. Therefore, by designing the body configuration based on the total aerodynamic resistance, we can get the basis for determining the optimal point.

[0067] Specifically, Figure 6 Medium FS p Curve (total aerodynamic resistance F and windward surface area S p The lowest point of the relationship curve is the theoretical optimal windward surface area; Figure 6 Medium Fd p Curve (total aerodynamic resistance F vs. characteristic diameter d p and the relationship curve), the lowest point on the curve, that is, F min The point is the theoretical optimal characteristic diameter, and then the theoretical optimal windward surface area can be obtained.

[0068] According to the comparison between the windward surface design area and the theoretical optimal windward surface area, if the windward surface design area is larger than the theoretical optimal windward surface area, the windward surface design area is selected; if the windward surface design area is smaller than the theoretical optimal windward surface area, the theoretical optimal windward surface area is selected.

[0069] Step 4: According to the satellite body configuration determined in step 2 and the windward surface area determined in step 3, the onboard equipment is specifically laid out to obtain the final onboard equipment layout and the length of the final satellite body configuration.

[0070] The specific layout of all equipment required for the mission requires the following factors to be considered: the design requirements for the relative positions of the center of pressure and the center of mass; the overall compact layout to increase the effective volume ratio of the configuration, that is, the ratio of the total volume of equipment carried inside the satellite platform to the total volume that can be provided. The increase in the effective volume ratio will reduce the area of ​​the outer wall of the configuration, which is helpful for aerodynamic drag reduction. The total volume of the equipment carried inside includes the volume of the necessary parts, cables, connectors, and fixtures for the installation and normal operation of the equipment.

[0071] In addition, the present invention also provides another design criterion:

[0072] In step 3.2 of step 3, the windward surface is not judged. Instead, after step 4 is executed, the slenderness ratio is used as the basis for judging the optimal aerodynamic resistance body configuration.

[0073] Specifically, after performing step 3.1, do not perform step 3.2 and directly perform step 4; in step 4, according to the satellite body configuration and windward surface design area determined in step 2, a specific layout of the onboard equipment is performed to obtain the layout form of the onboard equipment and the design length of the satellite body configuration.

[0074] The relationship between total aerodynamic drag and slenderness ratio is shown below.

[0075]

[0076] χ represents the ratio of the characteristic length of the side wind side of the configuration to the characteristic diameter (or side length) of the windward side, i.e., the slenderness ratio. Similar expressions can be listed for different body configurations, including combined body configurations.

[0077] According to the above formula, the total aerodynamic resistance F and the positive pressure aerodynamic resistance F under constant volume conditions and constant cross-section conditions can be obtained respectively. p The curve of the slenderness ratio of the body configuration, such as Figure 7 As shown. Figure 7 It can be seen from the figure that the slenderness ratio should be minimized when designing the body configuration under the condition of constant cross section. When designing the body configuration under the condition of constant volume, the lowest point can be obtained from the relationship between the total resistance F and the slenderness ratio curve, that is, F min Point, corresponding to which the theoretical optimal slenderness ratio can be obtained.

[0078] The design slenderness ratio is calculated according to the design length of the satellite body configuration, and compared with the design slenderness ratio and the theoretical optimal slenderness ratio of the satellite body configuration. If the design slenderness ratio is greater than the optimal slenderness ratio, the windward surface area is enlarged and the design length is reduced under the condition of constant volume to achieve the optimal slenderness ratio; if the design slenderness ratio is less than the optimal slenderness ratio, the design slenderness ratio is selected; after determining the slenderness ratio, the final windward surface area and the length of the satellite body configuration are determined.

[0079] Step 5: Design the layout of solar panels based on energy demand

[0080] According to the energy demand, the number of solar cell arrays and the total area of ​​solar wings are determined; according to the distribution requirements of the center of pressure and the center of mass, the layout of the solar wings is determined. The layout refers to the form of the solar wing after deployment, which can be overall downtilt, single-board downtilt, offset, swept, symmetrical, asymmetrical, etc.

[0081] Step 6: Determine the outer wall material of the satellite body based on the fitness of free molecules

[0082] The outer wall material is designed, and the material with high free molecular adaptability is selected as the outer wall material of the windward side, and the material with low free molecular adaptability is selected as the outer wall material of the sidewind side.

[0083] Different outer wall materials have different outer wall free molecule fitness (i.e. diffuse reflectance), which refers to the momentum fitness of free molecules in rarefied air after colliding with the outer wall of the satellite. The unfitness can be called the specular reflectance, which expresses the momentum change of gas molecules. The free molecule fitness of the outer wall is changed by selecting the structural plate material, surface processing accuracy control, surface treatment method selection, surface coating, and surface attachment material selection.

[0084] The selection is based on the relationship between the drag coefficient of the windward and crosswind surfaces and the fitness of the free molecules:

[0085]

[0087] S is the unit gas molecule speed ratio, S r is the molecular velocity ratio after reflection from the wall.

[0088] The corresponding windward and crosswind resistance coefficients and the free molecular fitness change rules are as follows: Figure 8 As shown in the figure, the solid line represents the relationship between the positive pressure drag coefficient and the fitness of the free molecules on the outer wall of the windward side under various ambient temperature conditions, and the dotted line represents the relationship between the shear drag coefficient and the fitness of the free molecules on the outer wall of the crosswind side under the ambient temperature conditions of 600K, 900K, 1200K, and 1500K, respectively.

[0089] It can be seen from the curve relationship that the wall surface with large free molecule fitness should be selected as the windward wall surface, and the wall surface with small free molecule fitness should be selected as the crosswind wall surface. The size of the free molecule fitness here cannot be judged simply by whether the surface is smooth. It is necessary to consider the momentum change of the gas molecules on the wall surface, that is, the wall surface with a large momentum change of the gas molecules on the wall surface is selected as the windward wall surface, and the wall surface with a small momentum change of the gas molecules on the wall surface is selected as the crosswind wall surface.

[0090] Preferably, the outer wall surface of the windward side is made of a material with a free molecular fitness of σ1, and the outer wall surface of the crosswind side is made of a material with a free molecular fitness of σ2. In order to effectively reduce the total aerodynamic resistance, σ1≥σ2 should be designed.

[0091] Step 7: Simulate and optimize the design results

[0092] The overall configuration and layout formed by the above steps are retested by aerodynamic simulation to verify whether the aerodynamic force and aerodynamic moment meet the design requirements.

[0093] If it meets the requirements, the design is completed; if the aerodynamic force does not meet the requirements, the onboard equipment layout is adjusted.

[0094] If the aerodynamic force does not meet the requirements, increase the internal effective volume ratio or reduce the exposed area of ​​the satellite surface equipment. If it still does not meet the requirements after repeated adjustments, consider adding inclined planes or conical surfaces in the area with larger aerodynamic force to change the local aerodynamic characteristics. The drag reduction trend can be derived based on the aerodynamics of rarefied gas.

[0095] If the aerodynamic moment does not meet the requirements, change the center of mass position. If it still does not meet the requirements after repeated adjustments, consider adding aerodynamic rudders or balance wings.

[0096] Once the aerodynamic force and aerodynamic moment meet the design requirements, the configuration and layout design of the ultra-low orbit satellite will be completed.

[0097] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for designing a configuration and layout of a very low-orbit satellite, characterized in that: include: S1. Determine the layout constraint characteristics of the equipment on board each satellite according to the mission requirements; S2. Under the layout constraint characteristics of the onboard equipment, different satellite body configurations are used to preliminarily layout the onboard equipment, obtain the preliminary windward surface area and crosswind surface area of ​​different satellite body configurations, calculate the effective surface area ratio of different satellite body configurations, and determine the final satellite body configuration by comparing the effective surface area ratios; S3. Determine the final windward surface area based on the satellite body configuration; S4, according to the satellite body configuration determined by S2 and the windward surface area determined by S3, the onboard equipment of each satellite is specifically arranged to obtain the final onboard equipment layout form and the final length of the satellite body configuration; S5. Design the layout of solar panels according to energy demand; S6. Determine the outer wall material of the satellite body based on the fitness of free molecules.

2. The ultra-low-orbit satellite configuration and layout design method according to claim 1, characterized in that: In S2, the effective surface area ratio includes the effective surface area ratio of the windward surface and the effective surface area ratio of the sidewind surface; the effective surface area ratio of the windward surface is the ratio of the windward surface area to the total volume of the equipment carried inside the satellite, and the effective surface area ratio of the sidewind surface is the ratio of the sidewind surface area to the total volume of the equipment carried inside the satellite.

3. The ultra-low-orbit satellite configuration and layout design method according to claim 2, characterized in that: The effective surface area ratio is set to: effective surface area ratio = windward surface effective surface area ratio + crosswind surface effective surface area ratio / η, where η is the drag coefficient ratio of the windward surface to the crosswind surface; each satellite body configuration is calculated according to the above formula to obtain an effective surface area ratio, and the comparison is performed, and the satellite body configuration with the smallest effective surface area ratio is taken as the final satellite body configuration.

4. The ultra-low-orbit satellite configuration and layout design method according to claim 1, characterized in that: The S3 includes: S31, based on the satellite body configuration and corresponding preliminary layout determined in S2, the windward surface design area is obtained according to the size of the largest profile equipment in the satellite in the windward surface projection direction; S32. Compare the designed windward surface area with the theoretical optimal windward surface area of ​​the satellite body configuration, and take the larger windward surface area between the two as the final windward surface area.

5. The ultra-low-orbit satellite configuration and layout design method according to claim 4, characterized in that: According to the final satellite body configuration and the correlation between the total aerodynamic drag and the total drag of the satellite surface equipment, the positive pressure aerodynamic drag, and the shear aerodynamic drag, the correlation between the total aerodynamic drag and the windward surface area of ​​the satellite body configuration is derived and transformed. The windward surface area when the total aerodynamic drag reaches the minimum value in the transformed correlation is taken as the theoretical optimal windward surface area.

6. The ultra-low-orbit satellite configuration and layout design method according to claim 4, characterized in that: In the step S3, after the step S31 is performed, the step S32 is not performed, and the step S4 is performed directly; in the step S4, according to the satellite body configuration determined in S2 and the windward surface design area determined in S31, the onboard equipment of each satellite is specifically laid out to obtain the layout form of the onboard equipment and the design length of the satellite body configuration; then, according to the design length of the satellite body configuration, the design slenderness ratio is calculated to obtain the design slenderness ratio, and the design slenderness ratio is compared with the theoretical optimal slenderness ratio of the satellite body configuration. If the design slenderness ratio is greater than the optimal slenderness ratio, the windward surface area is enlarged and the design length is reduced under the constant volume condition to achieve the optimal slenderness ratio; If the design slenderness ratio is less than the optimal slenderness ratio, the design slenderness ratio is selected; after determining the slenderness ratio, the final windward surface area and the length of the satellite body configuration are determined; the slenderness ratio is the ratio of the length of the sidewind surface to the characteristic diameter of the windward surface.

7. The ultra-low-orbit satellite configuration and layout design method according to claim 6, characterized in that: According to the final satellite body configuration and the correlation between the total aerodynamic drag and the total drag of the satellite surface equipment, the positive pressure aerodynamic drag, and the shear aerodynamic drag, the correlation between the total aerodynamic drag and the slenderness ratio of the satellite body configuration is derived and transformed. The slenderness ratio that makes the total aerodynamic drag reach the minimum value under constant volume conditions in the transformed correlation is taken as the theoretical optimal slenderness ratio.

8. The ultra-low-orbit satellite configuration and layout design method according to claim 1, characterized in that: In S6, the outer wall surface of the windward side is made of a material with a free molecular fitness of σ1, and the outer wall surface of the lateral side is made of a material with a free molecular fitness of σ2, σ1≥t2.

9. The ultra-low-orbit satellite configuration and layout design method according to claim 1, characterized in that: It also includes S7, simulating and optimizing the design results; the specific method is: verifying through simulation whether the aerodynamic force and aerodynamic moment of the design results meet the design requirements; if they do, the design is completed; if not, the layout of the onboard equipment is adjusted until the simulation verification results meet the design requirements; among them, if the aerodynamic force does not meet the requirements, the final layout of the onboard equipment is adjusted by increasing the internal effective volume ratio, reducing the exposed area of ​​the satellite surface equipment, locally adding inclined surfaces, and adding conical surfaces; if the aerodynamic moment does not meet the requirements, the final layout of the onboard equipment is adjusted by changing the center of mass position, adding aerodynamic rudders, and adding balance wings.

10. The ultra-low-orbit satellite configuration and layout design method according to any one of claims 1 to 8, characterized in that: In S2, the satellite body is configured as a single prism or a combination of prisms.

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