Dynamic Analysis And Orbit Design Of Perturbed Irregular Asteroids

The dynamics and control of the irregular gravitational field of asteroid is always the theoretical basis and the key problem to be solved.The asteroids in the solar system generally have the characteristics of small mass,irregular shapes,and different spin states,which makes the dynamic environment of the nearby spacecrafts very complicated.Therefore,a reasonable dynamic environment analysis of the spacecraft is very important for the design of the detection orbit.Similarly,for different types of asteroid exploration missions or different phases of missions,it is necessary to analyze the dynamics of each phase and then formulate the corresponding orbit design.Hovering orbit,that is,the spacecraft remains stationary relative to a point or an area of the asteroid surface,is widely used in the ground mapping and sampling of asteroids.From the perspective of the dynamic environment of the spacecraft,the irregular gravitational field of the asteroid,the gravitational perturbation of the sun or surrounding celestial bodies,and the perturbation of solar pressure are considered.Based on Newton's law of universal gravitation,the dynamic equation of the spacecraft is established.According to the characteristics of parameter excitation and external excitation embodied in the dynamic equation,a new resonant orbit family is obtained by using the method of nonlinear vibration,and a new design method of asteroid exploration orbit is proposed.The research content of the thesis is divided into the following parts:(1)Construction of perturbed irregular asteroid modelThe particle-linkage model is used to simulate the irregular gravitational field of asteroid.Considering the gravitational perturbations of the sun or the surrounding celestial bodies and solar pressure perturbations respectively,the dynamic equations of the spacecraft under different gravitational environments are obtained.The effects of gravitational environment on the number,position and stability of asteroid equilibrium points are studied.(2)Analysis of excitation resonanceBased on the dynamic equation of the spacecraft near the equilibrium point,the excitation form is analyzed.Through the nonlinear vibration theory,the relationship between the natural frequency of the system and the excitation frequency is compared.The parameter regions satisfying the main resonance,combined resonance,and internal resonance of the system are solved,and the occurrence conditions of the resonance orbit are obtained.The excitation resonance boundary of linear system is drawn respectively by multi-scale method and numerical simulation.(3)Resonance orbit and nonlinear characteristics of the asteroid spacecraftThe dynamic equations of different resonance types are solved by using multi-scale method.The steady solution of the system is analyzed and its stability is judged.Through numerical simulation,it can easily get the periodic resonance orbit of the asteroid probe.The amplitude-frequency response curve,force-frequency response curve,and phase diagram are plotted to analyze the nonlinear characteristics of the resonance orbit.