Dynamic Characteristics Analysis And Mission Orbit Design Of Binary Asteroid System

With the continuous development of space science and technology,the deep space exploration task in the world is advancing continuously.In the future,the deep space exploration will be the key development direction of China.The binary asteroid system will be one of the preferred targets for deep space exploration in the future because of its large number and unique scientific value.To detect the binary system in the solar system can obtain great research value.In order to further study the binary asteroid system,sampling and returning one or two celestial bodies of binary system will be the primary goal of future space missions.In this thesis,all studies are based on the potential engineering background of the binary system exploration and defense,respectively in the weak gravitational binary asteroid system gravity field modeling,dynamic characteristics of binary system,the positions and dynamical characteristics of artificial equilibrium points(AEPs)in the vicinity of a binary asteroid with continuous low-thrust,the periodic orbits and invariant manifolds of libration points in binary asteroid system and invariant manifolds and orbit design of the binary asteroid exploration mission.First of all,the shape-based ellipsoid-sphere model and ellipsoid-ellipsoid model of the binary asteroid system are established for the gravitational field modeling.An elliptical integral and second degree second order spherical harmonic function are adopted to calculate the gravitational potential energy of binary asteroid system,respectively.The effective potential function surfaces,the libration points and the zero velocity curves under different models are simulated and analyzed.Second,the positions and dynamical characteristics of artificial equilibrium points in the vicinity of a binary asteroid with continuous low-thrust are studied based on the ellipsoid-ellipsoid model which is calculated by the second degree second order spherical harmonic function.The motion equations of the spacecraft with continuous low-thrust are derived.The expression of the modified Jacobi's constant is proposed for the binary asteroid system with low-thrust and zero-velocity curves are used for analyzing the AEPs' feasible regions.The shapes of the sets of the AEPs are analyzed and concluded.The linearized equations of motion are derived for stability's analysis.Based on the characteristic equation of the linearized equations,the stability conditions are derived.The stable regions of AEPs are investigated by a parametric analysis.The effect of the mass ratio and ellipsoid parameters on stable region is also discussed.Next,the Lyapunov orbits and Halo orbits near the libration point are generated by a method of construction of flow functions.This method needs neither a starting analytic approximation nor the state transition matrix to be computed,so it can be conveniently implemented on a computer.Besides,this method is unaffected by the nonlinearity of the dynamical system,allowing a large set of periodic orbits which have x-z plane symmetry to be computed numerically.And the invariant manifolds corresponding to the periodic orbits are calculated by using the eigenvectors of the monodromy matrix.Finally,the phase space structure of the binary asteroid system is analyzed by Poincare maps.The transfer orbits between periodic orbits of libration points are constructed and the delta-V budget for low-cost transfer orbits is calculated.And the capture and escape orbits of libration points and the low-cost transfer orbits between libration points or two bodies are designed in planar and spatial cases,respectively.It provides a potential scheme for future binary asteroid explorations.