The Transfer Trajectory Desin And Optimization For Manned Asteroid Exploration

Manned asteroid exploration is a long-term interplanetary flight that is out of the influence of the earth, which cannot be replaced by manned lunar exploration. It can also become the forerunner of manned mars exploration in the future. Manned asteroid exploration has a very important research value. The design and optimization of the interplanetary transfer trajectory is one of the key technologies in the manned asteroid exploration mission. In this dissertation, the interplanetary transfer trajectory is investigated deeply based on the features of deep space transfer trajectories.Firstly, the pork chop plot of two-impulse transfer trajectory for Earth-Asteroid is created by solving the Gauss problem. According to the pork chop plot, the initial transfer trajectory and launch window of the spacecraft is determined. And then, the transfer trajectory selected by the pork chop plot is optimized by the sequential quadratic programming algorithm. The optimum two-impulse transfer trajectory for Earth-Asteroid is obtained. Finally, the launch window and optimum two-impulse transfer trajectory in 2018-2023 is given taking Nereus Asteroid as exploration target. The simulation results show that the aforementioned method is more suitable for impulse transfer trajectory design with a wide launch window.Secondly, the exponential sinusoid function approximation algorithm for design of low thrust transfer trajectory is investigated deeply. Next, the searching procedure of the launch window based on this algorithm is given. The step-size- and step-direction-controlled Newton method is used to solve the intersections of low thrust trajectory with projected trajectory in the reference plane. And then, the launch window and low thrust transfer trajectory in 2015-2025 is given taking Apophis Asteroid as exploration target. The simulation results show that the method is able to search out the initial design parameters of low thrust transfer trajectory quickly and accurately.Finally, the dissertation systematically studies the pseudo spectral method for its applications to low thrust trajectory optimization. The pseudo spectral scheme for low thrust trajectory optimization is first formulated. Next, the continuous trajectory optimization problem is transformed into a discrete nonlinear programming problem and the energy-optimal solution is obtained with the SNOPT solver. And then, the launch window and low thrust transfer trajectory is given taking Nereus Asteroid as exploration target by aforementioned method. The simulation results show that the method is able to solve the energy-optimal solution or fuel-optimal solution accurately.