Based On Sun–earth Lagrangian Point Capturing Small Asteroids Trajectory Design And Optimization

The asteroids are of great concern to scientists, because they are considered as the residues in the early solar system which contain rich information about the formation, evolution and composition of the solar system. Capturing asteroids to the vicinity of Earth, not only can obtain the primitive materials for scientific research, but also provides an opportunity to explore and utilize abundant resources on asteroids. Therefore, under the background of asteroids capture, this dissertation studies the optimization of capturing asteroids trajectory based on Sun-Earth Lagrangian points. The details are summarized as follows:Firstly, for the target selection of asteroids capture, this dissertation comprehensive analyzes the physical and orbital characteristic of Near-Earth Asteroids(NEAs), in terms of the orbit characteristics, spectral type and size distribution. Accordingly, the selection criteria of asteroid capture is given and the alternative targets are presented with the energy demand.Secondly, the asteroid capture trajectories based on impluse thrust are discussed in this dissertation adopting two- and multiple- impluse transfer combined with the three-body trajectory dynamics system manifold theory, the weak stability boundaries theory and the moon gravity-assisted theory. The trajectories designs for capture asteroids to the Sun-Earth Lagrangian points, the Sun-Earth weak stability boundaries and lunar orbits are investigated, respectively. The characteristics of trajectories and fuel consumptions in those three schemes are compared and analyzed.Thirdly, this dissertation studies the low-thrust transfer trajectories for asteroid capture, on the basis of homotopy optimization algorithm. the transfer trajectories contain the out bound trajectories from Earth to the target asteroids and in bound trajectories from the asteroid orbits to three kinds of destinations, the stable manifolds of periodic orbits around Sun-Earth Lagrangian points, the temporally stable regions defined by Sun-Earth weak stability boundaries and the high lunar orbit. The mission parameters of three schemes, such as fuel consumption are evaluated and analyzed with different operation modes and thrust values.In the fourth part of this dissertation, the designs of asteroid capture trajectories for the situation in which the spacecraft departs from the parking orbits around the Sun-Earth Lagrangian points and returns back to them are discussed. The stable and unstable manifolds are utilized to escape form and capture into the parking orbits. The impluse thrust and low-thrust are considered simultaneously. The fuel consumption and flight time of the two methods are compared with and analyzed.Finally, taken asteroid 2006RH120 as the alternative target, this dissertation provides a complete mission design for asteroid capture mission, including low-thrust transfer, capture and de-spin operations. Some key parameters such as system scale, mission duration and fuel consumption are evaluated and analyzed.