Method for determining the shielding coefficient of spacecraft micrometeoroid impact

Abstract

The present invention discloses a method for determining the shielding effect of a spacecraft micrometeoroid impact. Based on the micrometeoroid environment model Grün model, a spacecraft triangular surface mesh is established based on a spacecraft three-dimensional model using the Ansys system; the spacecraft orbit and attitude parameters are input; a calculation coordinate system is established, the micrometeoroid relative impact velocity is calculated for each grid unit, the initial position of the ray is sampled and it is determined whether the ray intersects with other triangular units. In order to accelerate the calculation of whether there is an intersection, a space partitioning structure such as an octree is used to calculate the increment ΔF. i until all triangular unit calculations are completed and the shielding coefficient F of each triangular unit is calculated. The present invention is helpful to improve the accuracy of spacecraft micrometeoroid impact analysis, improve the efficiency of spacecraft development, and reduce the cost of spacecraft development.

Description

Technical Field

[0001] The present invention belongs to the field of aerospace technology, aircraft design, and space environment engineering technology. Specifically, the present invention relates to a method for determining a spacecraft micrometeoroid impact shielding coefficient. Background Art

[0002] During the operation of spacecraft in orbit, the impact of micrometeoroids may cause the performance of subsystems or spacecraft to degrade, or even the mission cannot be completed. Therefore, it is necessary to evaluate the impact flux so that accurate protection can be made. However, due to the complex structure of the spacecraft and the mutual shielding of its own components, it is necessary to accurately calculate it in order to achieve more accurate impact protection.

[0003] The main body of a typical spacecraft structure is generally a rectangular parallelepiped with solar arrays on both sides. The length of the solar array is much larger than the size of the spacecraft body. Since micrometeoroids may come from all directions, the solar array and the spacecraft body can shield each other from some micrometeoroid impacts. Due to the relative position relationship between the solar array and the celestial body, the solar array has a shielding effect on some areas of the celestial body.

[0004] At present, there are some methods for analyzing impact flux, such as [1], Han Zengyao, Zheng Shigui, Yan Jun, Fan Jingyan, Qu Guangji. Development, verification and application of space debris impact probability analysis software. Journal of Astronautics, 2005, 26(2): 228-231. [2], WANG Hai-fu, YU Qing-bo, LIU You-ying, WANG Hui. M / OD Risk Assessment System and Its Applications. Journal of Beijing Institute of Technology, 2009, 18(1): 6-10. However, the above literature adopts the overlapping judgment method, that is, if the projections of the spacecraft surface units overlap, it is considered that the two are mutually blocked. This calculation method has poor calculation accuracy and takes a long time for large and complex spacecraft structures such as space stations.

[0005] As an example Figure 1a , Figure 1b As shown in the figure, two surface units 1 and 2 overlap along the x-axis projection. It is believed that surface unit 1 blocks surface unit 2, so surface unit 2 is not hit by micrometeoroids. But in fact, surface unit 2 is only partially blocked, so the calculation error is large. If the calculation accuracy needs to be improved, it is necessary to divide the surface units more finely, resulting in a large amount of intersection judgment calculation and a long time consumption. Moreover, due to the limitations of the calculation method, the calculation accuracy and time are difficult to estimate in advance. Summary of the invention

[0006] To solve this problem, the present invention proposes a method for determining the shielding effect of a spacecraft micrometeoroid impact, which can accurately calculate the shielding effect of a micrometeoroid impact. The technical solution adopted by the present invention is as follows:

[0007] A method for determining the occlusion effect of a spacecraft micrometeoroid impact comprises the following steps:

[0008] (1) Based on the Grün model of the micrometeoroid environment model, the spacecraft triangular surface mesh is established based on the spacecraft three-dimensional model using the Ansys system; the spacecraft orbit and attitude parameters are input; and a calculation coordinate system is established: the earth is located at the origin of the coordinate system and the spacecraft is located on the +Z axis;

[0009] (2) For each grid cell:

[0010] (a) Sampling the flight direction of a micrometeoroid;

[0011] (b) sampling a micrometeoroid velocity value in the flight direction according to the micrometeoroid environment model;

[0012] (c) Calculation of relative impact velocity of micrometeoroids if is the surface normal vector of the triangular mesh unit, then the micrometeoroid hits the triangular mesh unit, and continue to (d). Otherwise, determine whether the number of ray sampling of the triangular mesh unit is sufficient. If not, continue to execute (a).

[0013] (d) The initial position of the sampling ray;

[0014] (e) Determine whether the ray at the initial position intersects with other triangular mesh units. To speed up the calculation of whether there is an intersection, an octree space partitioning structure is used. If it intersects, determine whether the number of ray samples at the initial position is sufficient. If not, return to (a); if not, continue to (f);

[0015] (f) Calculate the increment ΔF i ; Where g(Vm) is the probability function corresponding to the micrometeoroid velocity value Vm when the Grün model is used; It is to calculate the relative impact velocity of micrometeoroids;

[0016] (g) Repeat (a)-(f) until the specified number of rays is reached;

[0017] (3) Loop (2) until all triangular mesh units are calculated;

[0018] (4) Calculate the occlusion coefficient F of each triangular mesh unit,

[0019]

[0020] Where N is the number of rays traced.

[0021] The calculation method of the present invention can accurately analyze the shielding effect of micrometeoroid impact, which is helpful to improve the accuracy of spacecraft space environment effect analysis, improve spacecraft development efficiency, and reduce spacecraft development costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1a-1b It is a schematic diagram of the projection occlusion of the spacecraft surface unit;

[0023] Among them, 1 and 2 are spacecraft surface units.

[0024] Figure 2 It is a schematic diagram of the division of surface units of the spacecraft body. DETAILED DESCRIPTION

[0025] The test method and the test system of the present invention are described in detail below with reference to the accompanying drawings, but the description is merely exemplary and is not intended to limit the protection scope of the present invention in any way.

[0026] The present invention is further described below in conjunction with the accompanying drawings.

[0027] Reference Figure 2 , Figure 2 It is a schematic diagram of the division of surface units of the spacecraft body.

[0028] According to the spacecraft orbit and attitude parameters, the micrometeoroid environment model Grün model is selected, and the spacecraft three-dimensional model is divided into triangular surface meshes using the Ansys system; the spacecraft orbit and attitude parameters are input, which should at least include the six orbital elements and pitch, yaw, and roll angle parameters; a calculation coordinate system is established: the earth is located at the origin of the coordinate system, and the spacecraft is located on the +Z axis; first, the initialization work is completed, including using existing software with a meshing function to divide the surface triangular mesh of the spacecraft three-dimensional geometric model, and setting the number N of micrometeoroid directions that need to be calculated for each triangular mesh unit, for example, to 100.

[0029] Enter the orbital velocity of the spacecraft relative to the center of the Earth For example, [7.8,0,0]. Figure 1b The origin of the coordinate system is at the center of the Earth, the X axis passes through the Greenwich meridian, and the Z axis passes through the geographic North Pole. The spacecraft is located on the +Z axis.

[0030] For each triangular mesh element:

[0031] (a) Calculate the direction of the micrometeoroid Ri = [x, y, z], where i ranges from 1 to N. The calculation method is as follows:

[0032] x=cosφcosθ, y=sinφcosθ, z=r0

[0033] θ=cos -1 (r0), φ=2πr1(1) (1)

[0034] Where r0 and r1 are uniformly distributed random numbers in the interval [0,1]. For example, r0 = 0.23, r1 = 0.74. Then θ is 1.3387, φ is 4.65. Then x = -0.014, y = -0.23, z = 0.23.

[0035] (b) According to the micrometeoroid environment model Grün model, the micrometeoroid velocity value v corresponding to Ri is calculated by the rejection sampling method. m , and calculate its probability g(v m )(This is the prior art). vm=22.922, g(vm)=0.1619.

[0036] (c) Calculate the relative impact velocity of the micrometeoroid:

[0037]

[0038] is a vector, vm = [-0.321, -5.27, 5.27]

[0039] Compute vector dot product is the surface normal of the triangular mesh unit. If If the micrometeoroid hits the surface unit, continue to (d). Otherwise, determine whether i is less than N. If so, continue to (a).

[0040] For example, if n =

[100] , then Since it is < 0, continue with (d).

[0041] (d) Calculate the initial position of the ray as follows:

[0042] Assume that the coordinate vectors of the three vertices of the triangular mesh unit are A, B, and C, then the starting point P of the ray is:

[0043]

[0044] Where r2 and r3 are uniformly distributed random numbers in the interval [0,1]. If r2+t3>1, then let r2=1-r2, r3=1-r3.

[0045]

[0046] For example, A=[0 0 0], B=[0 1 0], C=[0 0 1]. Then r2=0.43, r3=0.32. Then P=[0 0.43 0.32].

[0047] (e) Determine whether the ray intersects with other triangular mesh units (this is a prior art in computer graphics). If so, determine whether the ray number is less than N. If so, return to (a). If not, continue to (f).

[0048] Assume disjointness.

[0049] (f) Calculate the increment ΔF i .

[0050]

[0051] Here the value is 0.052.

[0052] (g) The occlusion coefficient of the triangular grid unit is:

[0053]

[0054] Where N is the number of rays traced.

[0055] Repeat (a)-(g) until the specified number of rays is reached.

[0056] For example, suppose it is 0.56.

[0057] (4) Repeat (3) until all triangular mesh unit calculations are completed.

[0058] Although the specific embodiments of the present invention are described and illustrated in detail above, it should be pointed out that various equivalent changes and modifications can be made to the above embodiments based on the concept of the present invention. As long as the functional effects produced do not exceed the spirit covered by the specification and drawings, they should all be within the protection scope of the present invention.

Claims

1. A method for determining the occlusion effect of a spacecraft micrometeoroid impact, comprising the following steps: (1) Based on the Grün model of the micrometeoroid environment model, the spacecraft triangular surface mesh is established based on the spacecraft three-dimensional model using the Ansys system; the spacecraft orbit and attitude parameters are input; and a calculation coordinate system is established: the earth is located at the origin of the coordinate system and the spacecraft is located on the +Z axis; (2) For each grid cell: (a) Sampling the flight direction of a micrometeoroid; (b) sampling a micrometeoroid velocity value in the flight direction according to the micrometeoroid environment model; (c) Calculation of relative impact velocity of micrometeoroids if is the surface normal vector of the triangular mesh unit, then the micrometeoroid hits the triangular mesh unit, and continue to (d). Otherwise, determine whether the number of ray sampling of the triangular mesh unit is sufficient. If not, continue to execute (a). (d) The initial position of the sampling ray; (e) Determine whether the ray at the initial position intersects with other triangular mesh units. To speed up the calculation of whether there is an intersection, an octree space partitioning structure is used. If so, determine whether the number of ray samples of the triangular mesh unit is sufficient. If not, return to (a); if not, continue to (f); (f) Calculate the increment ΔF i ; Where g(Vm) is the probability function corresponding to the micrometeoroid velocity value Vm when the Grün model is used; is the relative impact velocity of the micrometeoroid calculated in step (c); (g) Repeat (a)-(f) until the specified number of rays is reached; (3) Loop (2) until all triangular mesh units are calculated; (4) Calculate the occlusion coefficient F of each triangular mesh unit, Where N is the number of rays traced.

2. The method according to claim 1, wherein: The parameters should at least include the number of six tracks and the pitch, yaw and roll angle parameters.

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