Low Energy Trajectory Design And Optimization For Collinear Libration Points Missions

Libration points are not only ideal locations for observing the Sun and the environment, but also perfect gateways for the interplanetary exploration. In this dissertation, low energy trajectory design and optimization for collinear libration point missions is studied. The main contents of this dissertation are as follows:First, high precision ephemeris orbit dynamical model is established with the JPL DE 405 ephemeris model, the non-spherical gravity perturbation of the central body, the gravitational perturbation of the Sun and the planets, and the solar radiation pressure. The jacobian matrix is then derived with all the perturbations.Then, orbit design and station keeping control problem of quasi-periodic orbits near the collinear libration points is studied. The characteristics of quasi-periodic orbits are analyzed, and the orbit design methods are studied. Much effort is spent on the derivation of the position and velocity transformation relationship between the synodic frame in the circular restricted three-body problem and the inertial coordinate system in the ephemeris dynamical model. A simple station keeping control algorithm is given based on differential corrections, and numerical simulation shows that the algorithm is very effective.Transfer trajectory design and optimization for libration point missions is studied systematically. Free transfer trajectory is firstly studied with the invariant manifolds, with the emphasis on the low energy transfers in the ephemeris dynamical model. Free transfer trajectory for Halo orbit in the Earth-Moon system can be obtained by computation of invariant manifolds in the ephemeris dynamical model, which provides a new approach for the design of low energy trajectory for Halo orbit in the Earth-Moon system. Since the invariant manifolds of the middle and small amplitude Halo orbit could not approach the primary body, two-impulse transfer trajectory is studied extensively. By use of the least square principle, the differential correction equation is solved without reducing the freedom of the system, and the least square solution is also the fuel optimal solution in a single iteration. Since the convergence behavior of the differential correction method is insufficient, a novel method for transfer trajectory design using the eigenvector of the response matrix is proposed. The method has very good convergence behavior, and the design efficiency is improved remarkably by combining the method with the differential corrections. Since the local optimization method could not insure the global optimum of transfer trajectory, a hybrid intelligent method with the genetic algorithm and the differential correction method is proposed. The proposed method can approach the global optimum of transfer trajectory, and need no initial guess. Since previous studies on the optimization of manifold insertion problem tends to stop at the local optimal points, a method for the optimization of manifold insertion problem is proposed with the eigenvector of the responsive matrix, and the distribution of the optimal manifold insertion points is obtained. For the transfer between the libration points and the bigger primary in the three-body system, three-impulse transfer trajectory using the invariant manifolds and smaller primary flybys is proposed and studied extensively. The proposed transfer trajectory to lunar Halo orbit requires much lower maneuver velocity than that of direct transfer, and requires much shorter flight time than that of WSB transfer to lunar Halo orbit. The trajectory correction problem is transformed into the transfer trajectory design problem and solved by the differential correction method.Mult-objective exploration trajectory based on libration points is studied. The characteristics and types of mult-objective exploration trajectory are analyzed and summarized, and mult-objective exploration trajectory with the manifold connections, lunar flybys, and planetary flybys is studied respectively.Software for low energy trajectory design of libration point missions is developed. The software supports low energy trajectory design of libration point missions, data reports, and visualization. The software also has the user-friendly graphical user interface. Compared with the Satellite Tool Kit, the position error and the velocity error of the design results of the software is in the order of 1 m and is 10-6 m/s respectively, in a period of a Halo orbit (about 180 days for Sun-Earth L1 Halo orbit, and 15 days for Earth-Moon L2 Halo orbit).A novel lunar sample return scenario with the invariant manifolds and lunar flyby is proposed. Compared with previous scenarios of JPL, the proposed scenario requires much lower maneuver velocity than that of the conic scenario, and requires much shorter flight time than that of the interplanetary superhighway scenarios. The proposed scenario has very good prospect in future lunar exploration.