Spacecraft deflection asteroid maximum speed variation estimation method and equipment

Abstract

The invention relates to a spacecraft deflection asteroid maximum speed variation estimation method and equipment. The method comprises the following steps: acquiring related parameters of a target asteroid; according to the orbital intersection condition of the target asteroid and the earth, carrying out interception task planning, and determining related parameters of a task spacecraft; obtaining an asteroid absolute speed and a spacecraft absolute speed during collision according to the interception task plan; based on the determined momentum transfer coefficient threshold expression, the target asteroid related parameters, the task spacecraft related parameters, the asteroid absolute speed and the spacecraft absolute speed, estimating the spacecraft deflection asteroid maximum speed variation; wherein the momentum transfer coefficient threshold expression is determined by combining the energy conservation law and the momentum conservation law. Compared with the prior art, the method has the advantages of high accuracy and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of asteroid defense, and in particular relates to a method and device for estimating the maximum velocity change of asteroid deflected by a spacecraft. Background Art

[0002] The frequent occurrence of asteroid hazards has made the issue of asteroid defense more and more important to scientific researchers. Correspondingly, asteroid defense missions are also being actively carried out at home and abroad. Limited by the maturity of technology and the applicability of scenarios, the asteroid defense method currently used in asteroid defense missions is mainly the kinetic impact method, that is, by launching a spacecraft to collide with the target asteroid at high speed to achieve the purpose of deflection defense. In the process of a spacecraft and an asteroid at high speed, the momentum change of the asteroid is the sum of the momentum of the spacecraft and the momentum of the permanently ejected splash produced during the impact. From the results of a large number of ground and simulation tests, the momentum of the splash is usually many times the momentum of the simulated spacecraft, which results in the momentum change brought to the asteroid by the impact being many times the momentum of the spacecraft. The momentum transfer coefficient β is generally used to represent this multiple.

[0003] Since the velocity change of the target asteroid is affected by the momentum transfer coefficient β, β can be used to evaluate the impact deflection effect. The relationship between β and the velocity change of the target asteroid is deduced as follows:

[0004] m ast v ast +m sc v sc =(m ast +m sc -∑m * )v′ ast +p ej

[0005] ∑m * <<m ast +m sc

[0006] (m ast +m sc )(v ast -v′ ast )=p ej +m sc (v ast -v sc )

[0007] Δv=v ast -v′ ast

[0008] u=v ast -v sc

[0009]

[0010]

[0011] In the formula, m ast is the mass of the target asteroid, m sc is the mission spacecraft mass, v ast is the absolute velocity of the asteroid, v sc is the absolute velocity of the impactor, ∑m * is the mass of the escaped splash produced by the hypervelocity impact, v′ ast is the absolute velocity of the asteroid after impact, p ej is the momentum carried by the escaping splashes, Δv is the change in velocity before and after the impact of the target asteroid, and u is the relative impact velocity between the spacecraft and the asteroid.

[0012] As can be seen from the above formula, the size of β directly affects the change in the velocity of the asteroid after being deflected by the impact. Therefore, the threshold analysis of β plays a great role in designing the indicators of asteroid defense missions and analyzing the applicability of the kinetic impact method. At present, the analysis methods of β can be mainly divided into two categories: dimensionless analysis based on point source theory and ground test data fitting. These methods mainly focus on analyzing the relationship between β and elements such as relative impact velocity and target porosity, and ignore the study of the β threshold part.

[0013] Most of the current research on momentum transfer coefficient is based on theoretical analysis and fitting the relationship between β and relative impact velocity, porosity and other elements through ground test data. The literature "mentum transfer in asteroid impacts.i.theory and scaling" (Holsapple KA, Housen K R.Icarus, 2012, 221(2):875-887) established the sputtering scaling theory of sputtering velocity and mass distribution through point source theory and dimensionless analysis, provided a theoretical description of the sputtering mass, velocity and position distribution, and gave an expression for β based on this. The paper "Hypervelocity cratering and disruption of the northwest africa 869ordinary chondrite meteorite:Implications for crater production,catastrophic disruption,momentum transfer and dust production on asteroids" (Flynn GJ,Durda DD,Patmore EB,et al.Planetary and Space Science,2018,164:91-105) conducted a hypervelocity impact experiment on asteroid analogs. The typical evolution of the splashback is shown in the figure below. Figure 1 As shown in the literature, it is found that the plume on the surface of the asteroid analog will form a projection cone when colliding, and the angle between the projection cone and the surface of the asteroid analog is about 45°. F, Hupfer J, et al. Procedia Engineering, 2015, 103: 197-204) found that the angle between the ejecta cone and the surface of the asteroid analogue decreases as the porosity of the analogue increases, which means that the velocity component of the splash parallel to the impact direction decreases, p ejDecreases, β decreases. Moreover, the literature "Ejecta velocity distribution for impact cratering experiments on porous and low strength targets" (Michikami T, Moriguchi K, Hasegawa S, et al. Planetary and Space Science, 2007, 55 (1-2): 70-88.) found that the mass and velocity of splashes will decrease when impacting asteroid analogs with higher porosity. Based on the above derivation and research, it can be concluded that β increases with the increase of impact velocity and body bonding strength, and decreases with the increase of asteroid porosity. Unfortunately, the above-mentioned prior art focuses on the relationship between β and the properties of asteroids and the relative impact velocity when studying and analyzing β, ignoring the qualitative analysis of the β threshold, which affects the accuracy of the determination of asteroid defense missions. Summary of the invention

[0014] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a method and device for estimating the maximum velocity change of asteroid deflected by a spacecraft with high accuracy.

[0015] The purpose of the present invention can be achieved by the following technical solutions:

[0016] A method for estimating the maximum velocity change of a spacecraft deflecting an asteroid comprises the following steps:

[0017] Obtain relevant parameters of the target asteroid;

[0018] According to the intersection of the target asteroid and the Earth's orbit, interception mission planning is carried out to determine the relevant parameters of the mission spacecraft;

[0019] Obtaining the absolute velocity of the asteroid and the absolute velocity of the spacecraft at the time of impact according to the interception mission plan;

[0020] Based on the determined momentum transfer coefficient threshold expression and the target asteroid related parameters, mission spacecraft related parameters, the asteroid absolute velocity and the spacecraft absolute velocity, the maximum velocity change of the asteroid deflected by the spacecraft is estimated;

[0021] The momentum transfer coefficient threshold expression is determined by combining the law of conservation of energy and the law of conservation of momentum.

[0022] Furthermore, the target asteroid related parameters include six orbital numbers of the asteroid and the mass of the target asteroid.

[0023] Further, the relevant parameters of the mission spacecraft include the mass of the mission spacecraft and the number of mission spacecraft.

[0024] Further, the upper limit of the momentum transfer coefficient is determined by the lower limit of twice the kinetic energy E ej carried by the splashes.

[0025] Further, the acquisition of the kinetic energy carried by the splashes includes:

[0026] Estimating the velocity distribution and mass distribution of the splashes generated when the spacecraft impacts the asteroid according to the interception mission plan, and estimating the kinetic energy carried by the splashes.

[0027] Further, the expression of the momentum transfer coefficient threshold is:

[0028]

[0029] In the formula, C is a constant, and 0 < C < 1, u is the relative impact velocity, E ej is twice the kinetic energy carried by the splashes, E ej ∝u n means that E ej is proportional to the nth power of u, β is the momentum transfer coefficient, m ast is the mass of the target asteroid, m sc is the mass of the mission spacecraft, ∑m ej is the mass of the escape splashes generated by the hypervelocity impact, and → means approaching.

[0030] Further, when the power exponent n satisfies n ≤ 2, the estimation formula for the maximum velocity change of the spacecraft deflecting the asteroid is:

[0031]

[0032] In the formula, Δv is the velocity change of the target asteroid before and after the impact, m ast is the mass of the target asteroid, m sc is the mass of the mission spacecraft, C is a constant, and u is the relative impact velocity.

[0033] Further, the method further includes:

[0034] Calculating the deflection distance of the asteroid after the velocity change based on the maximum velocity change of the spacecraft deflecting the asteroid, and determining whether it meets the mission requirements.

[0035] The present invention also provides a computer-readable storage medium, which is characterized in that it includes one or more programs for execution by one or more processors of an electronic device, and the one or more programs include instructions for executing the method for estimating the maximum velocity change of the spacecraft deflecting the asteroid as described above.

[0036] The present invention also provides an electronic device comprising one or more processors, a memory and one or more programs stored in the memory, wherein the one or more programs include instructions for executing the method for estimating the maximum velocity change of asteroid deflected by a spacecraft as described above.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention analyzes the threshold value of the momentum transfer coefficient, clarifies the relationship between the momentum transfer coefficient and the mass of the spacecraft and the target asteroid, and can accurately estimate the maximum velocity change caused by the deflected asteroid.

[0039] There is no research and analysis on the momentum transfer threshold in the prior art. The present invention fills a part of the gap in asteroid defense research. The method of the present invention can adapt to complex and changeable planetary defense missions, and can combine the imaging data (estimated asteroid mass) and the spacecraft asteroid velocity data in the mission to make a relatively accurate estimate of the momentum transfer coefficient after deflection, and then estimate the maximum velocity change caused by the deflected asteroid. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a typical evolution diagram of existing backsplash;

[0041] Figure 2 This is a schematic diagram showing the effect of the size of β on the final deflection effect when deflecting a target asteroid;

[0042] Figure 3 Flow chart of the method of the present invention. DETAILED DESCRIPTION

[0043] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0044] For a target asteroid of a certain size, the magnitude of the momentum transfer coefficient β will affect the final deflection effect when deflecting it. Figure 2 As shown in the figure, Δv A It refers to the change in the tangent direction of the target asteroid along its orbit when β=1. The B plane is defined as a plane perpendicular to the hyperbolic velocity of a near-Earth asteroid when it enters the Earth's sphere of influence and passing through the Earth's center of mass. It is often used to describe the relative position of an asteroid to the Earth.

[0045] In order to study the threshold of β, it is assumed that there is no energy loss during the hypervelocity collision, that is, the kinetic energy carried by the spacecraft is completely converted into the kinetic energy of the target asteroid and the kinetic energy of the splashing objects. Based on the law of conservation of energy, the formula is listed with the asteroid as the reference system:

[0046]

[0047] Among them, m ast is the mass of the target asteroid, m sc is the mission spacecraft mass, ∑m ej is the mass of the escaped splash produced by the hypervelocity impact, Δv is the velocity change of the target asteroid before and after the impact, u is the relative impact velocity between the spacecraft and the asteroid, and v eji is the relative velocity of the splash in the asteroid reference frame.

[0048] Since the mass of the spacecraft is much smaller than the mass of the target asteroid, m ast -∑m ej >>m sc , define twice the kinetic energy carried by the splash as By transforming formula (1), we can get formula (2):

[0049]

[0050] According to the law of conservation of momentum, we can get equation (3):

[0051] m ast v ast +m sc v sc =(m ast +m sc -∑m ej )v′ ast +p ej (3)

[0052] The newly added variable v in the formula ast is the absolute velocity of the asteroid, v′ ast is the absolute velocity of the asteroid after impact, v sc is the absolute velocity of the impactor, u=v ast -v sc , Δv=v ast -v′ ast , p ej is the momentum carried by the escaping splash, considering m sc and ∑m ej Much smaller than m ast , that is, there exists ∑m ej <<m ast +m sc , m sc +∑m ej <<m ast , substituting formula (2) into formula (3) yields:

[0053]

[0054] In the formula, |||| is the norm symbol, which can be understood here as taking the absolute value of a scalar and the modulus of a vector.

[0055] Since the definition formula of β is: Substituting formula (4) into it, we can get:

[0056]

[0057] Assume that β has an upper limit and β 2 < k, then through further derivation of formula (5), we can get:

[0058]

[0059] It can be seen that the lower limit of E ej determines the upper limit of β. It is known that E ej ≥ 0. When E ej is 0, the upper limit of β is

[0060] It is also known that β generally increases with the increase of the relative impact velocity u. Considering different power-law relationships between E ej and u, when u approaches ∞, the threshold value of the momentum transfer coefficient β:

[0061]

[0062] In the formula, n represents the power exponent, C is a constant, and 0 < C < 1. The above is the threshold expression of β in general cases. → means approaching. In the case where E ej is proportional to various power exponents of u, the threshold value of the momentum transfer coefficient is discussed in different cases.

[0063] Considering that generally n ≤ 2 in general cases, we can further obtain the estimation formula of the maximum velocity change Δv of the target asteroid:

[0064]

[0065] In summary, it can be found that the threshold value of β is positively correlated with the mass ratio of the target asteroid to the impactor. The maximum velocity change caused by deflecting the asteroid can be estimated according to this value. Considering that in actual situations, the relative impact velocity u < 10 km / s, when the target asteroid is too large, the upper limit of β is extremely high. At this time, increasing the magnitude of β will not affect the subsequent deflection effect. This theoretically explains the scenario applicability of the kinetic impact technology in the field of planetary defense. The kinetic impact technology is generally applicable to asteroids with an equivalent diameter of dozens of meters to more than one hundred meters. At the same time, this also means that attention needs to be paid to the scale ratio between the impactor and the asteroid simulation target material during ground experiments and digital simulation tests. When formulating the planetary defense mission strategy, the optimization goal should not only be to increase β.

[0066] Through the above-mentioned threshold analysis process of the momentum transfer coefficient, we can more clearly understand the relationship between the momentum transfer coefficient and the mass of the spacecraft and the target asteroid. In practical applications, it can be used to estimate the maximum velocity change caused by deflecting the asteroid, design relevant mission indicators, such as deflection distance, mission spacecraft mass, number of mission spacecraft, interception orbit selection, etc., and confirm whether the kinetic impact technology is suitable for the defense mission.

[0067] Based on the above-mentioned threshold analysis of the momentum transfer coefficient, the present invention provides a method for estimating the maximum velocity change of asteroids deflected by a spacecraft, obtains the relevant parameters of the target asteroid, performs interception mission planning according to the orbital intersection of the target asteroid and the earth, determines the relevant parameters of the mission spacecraft, obtains the absolute velocity of the asteroid and the absolute velocity of the spacecraft at the time of impact according to the interception mission planning, and estimates the maximum velocity change of asteroids deflected by the spacecraft based on the determined momentum transfer coefficient threshold expression and the relevant parameters of the target asteroid, the relevant parameters of the mission spacecraft, the absolute velocity of the asteroid and the absolute velocity of the spacecraft. The specific steps of this method are as follows: Figure 3 As shown, including:

[0068] Step S1: Obtain relevant parameters of the target asteroid, such as the six orbital elements, m ast The six orbital elements are used to describe the six parameters necessary to determine the orbit of a celestial body (including asteroids) under the action of Newton's laws of motion and Newton's law of universal gravitation when it moves on its Kepler orbit, including semi-major axis, eccentricity, orbital inclination, ecliptic longitude of ascending node, perihelion angle and mean anomaly.

[0069] Step S2: Design an interception trajectory according to the intersection of the orbits of the asteroid and the Earth, and obtain a relative impact velocity u interval;

[0070] Step S3, conduct preliminary planning, determine the mission interception orbit, initial spacecraft mass, quantity, etc.;

[0071] Step S4: According to the mission plan, obtain the absolute velocity v of the asteroid at the time of impact ast , spacecraft mass m sc and the absolute velocity v sc And other parameters;

[0072] Step S5: Estimate the velocity distribution and mass distribution of splashes generated when the spacecraft collides with the asteroid, and estimate the kinetic energy and E carried by the splashes. ej ;

[0073] Step S6: Estimate the momentum transfer coefficient threshold value according to the above-mentioned momentum transfer coefficient threshold estimation method, and estimate the maximum velocity change of the target asteroid after the impact.

[0074] Furthermore, whether the kinetic impact technology is suitable for the current defense mission can be judged according to the maximum velocity change of the asteroid deflected by the spacecraft, and the method further includes:

[0075] Step S7: further calculate the deflection distance after the asteroid velocity changes to determine whether it meets the mission requirements. If so, end; if not, return to step S3.

[0076] If the above method is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0077] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for estimating the maximum velocity change of a spacecraft deflecting an asteroid, characterized in that: The following steps are involved: Obtain relevant parameters of the target asteroid; According to the intersection of the target asteroid and the Earth's orbit, interception mission planning is carried out to determine the relevant parameters of the mission spacecraft; Obtaining the absolute velocity of the asteroid and the absolute velocity of the spacecraft at the time of impact according to the interception mission plan; Based on the determined momentum transfer coefficient threshold expression and the target asteroid related parameters, mission spacecraft related parameters, the asteroid absolute velocity and the spacecraft absolute velocity, the maximum velocity change of the asteroid deflected by the spacecraft is estimated; The momentum transfer coefficient threshold expression is determined by combining the law of conservation of energy and the law of conservation of momentum.

2. The method for estimating the maximum velocity change of asteroid deflected by a spacecraft according to claim 1, characterized in that: The target asteroid related parameters include the six orbital numbers of the asteroid and the mass of the target asteroid.

3. The method for estimating the maximum velocity change of asteroid deflected by a spacecraft according to claim 1, characterized in that: The mission spacecraft related parameters include the mission spacecraft mass and the mission spacecraft quantity.

4. The method for estimating the maximum velocity change of a spacecraft deflecting an asteroid according to claim 1, characterized in that: The upper limit of the momentum transfer coefficient is twice the kinetic energy E carried by the splash ej The lower limit of .

5. The method for estimating the maximum velocity change of asteroid deflected by a spacecraft according to claim 4, characterized in that: The acquisition of the kinetic energy carried by the splashing objects includes: The velocity distribution and mass distribution of splashes generated when the spacecraft collides with the asteroid are estimated according to the interception mission plan, and the kinetic energy carried by the splashes is estimated.

6. The method for estimating the maximum velocity change of asteroid deflected by a spacecraft according to claim 1, characterized in that: The momentum transfer coefficient threshold expression is: Where C is a constant and 0 < C < 1, u is the relative impact velocity, E ej is twice the kinetic energy carried by the spall, E ej ∝ u n means that E ej is proportional to the nth power of u, β is the momentum transfer coefficient, m ast is the mass of the target asteroid, m sc is the mass of the mission spacecraft, ∑m ej is the mass of the escape spall produced by the hypervelocity impact, and → means approaching.

7. The method for estimating the maximum velocity change of asteroid deflected by a spacecraft according to claim 1, characterized in that: When the power n satisfies n≤2, the estimation formula for the maximum velocity change of the asteroid deflected by the spacecraft is: Where Δv is the velocity change of the target asteroid before and after the impact, m ast is the mass of the target asteroid, m sc is the mass of the mission spacecraft, C is a constant, and u is the relative impact velocity.

8. The method for estimating the maximum velocity change of asteroid deflected by a spacecraft according to claim 1, characterized in that: The method further includes: The deflection distance of the asteroid after the speed change is calculated based on the maximum speed change of the asteroid deflected by the spacecraft to determine whether it meets the mission requirements.

9. A computer-readable storage medium, characterized in that: The method comprises one or more programs for execution by one or more processors of an electronic device, wherein the one or more programs include instructions for executing the method for estimating the maximum velocity change of asteroid deflected by a spacecraft as described in any one of claims 1-8.

10. An electronic device, characterized in that: The method comprises one or more processors, a memory and one or more programs stored in the memory, wherein the one or more programs include instructions for executing the method for estimating the maximum velocity change of asteroid deflected by a spacecraft as described in any one of claims 1-8.

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