Trajectory Design And Optimization For The Solar System Boundary Exploration Mission

The exploration of the solar system boundary is the forefront of international space science research and of the great significance to the breakthrough of major scientific issues such as dynamics of solar wind in the heliosphere,and the origin and evolution of stellar systems.Based on the mission objectives and constraints proposed for the mission of China's exploration of the solar system boundary,this paper combined the gravity assist technology,chemical propulsion technology and electric propulsion technology to optimize the design of the trajectory of the solar system boundary exploration mission.According to the solar system boundary exploration plan,the spacecraft will fly along the ecliptic plane to the place 100 AU away from the Sun around 2049,or towards the nose of heliosphere which directing to the celestial center of the galaxy,or to the heliosphere boundary in the tail direction that is towards the celestial area as away from the center of the galaxy.Additionally,during the flight,it is required to perform overflight detection on at least two large planets,Centaurs,and Kuiper belt objects.For the complex multi-constrain and multi-objective trajectory design problem,a novel design method is adopted: taking the Jupiter's flyby time window as a starting point,the orbit is divided into Earth to Jupiter segment and Jupiter to solar system boundary segment.Then the trajectory is optimized in segments to reduce the constraints in each segment so that the design diffulty is reduced.Finally,the optimal impulsive trajectories for different mission constraints are presented.The conversion conditions of impulsive trajectory into low-thrust trajectory were analyzed.The empirical parameters of whether the impulsive trajectory can be conversed into a low-thrust trajectory are obtained.Based on this conclusion,the feasibility of conversion between impulsive trajectory and low-thrust trajectory can be evaluated quickly,which improves the efficiency of the optimal design of low-thrust trajectory.It is concluded that the change of the initial mass within a certain range has little effect on the speed increment of the low-thrust trajectory after analysis.And based on the time and state of the obtained impulsive trajectories,low-thrust trajectories with minimum fuel are designed and optimized by Differential Evolution algorithm(DE).The calculation formula of minimum orbital intersection distance(MOID)of hyperbolic orbit is derived.In view of the problem of searching for the asteroid flyby detection targets near the nominal orbit,a method based on MOID calculation is proposed,which improves the search efficiency of asteroid detection targets.Finally,based on the low-thrust trajectories of VEEJN and EJ sequence,the optimal design of asteroid flyby detection orbit in the solar system boundary exploration mission was completed.