Design And Optimization Of Mars Exploration Orbit Based On High/low Thrust

Up to now humans have launched spacecraft to all nine planets in the solar system(including Pluto).Among these deep-space targets,Mars has attracted the most attention due to its good geographic location and exploration value.However,it is worth noting that in order to make the spacecraft reach Mars successfully,researchers have to design a suitable transfer orbit in advance via the orbit design and optimization technology.According to the type of propulsions,the technology can be divided into two forms: the first is the high-thrust orbit design technology based on chemical fuel propulsion,and the second is the low-thrust orbit design technology represented by electric propulsion.The former has been demonstrated through many flight tests and has become the preferred design method for the initial stage of deep space exploration in various countries.Although the latter has a very high degree of difficulty in design and control,compared with the former,it can significantly reduce the fuel cost and become a state-of-art technology for future orbit transfer.This article has conducted a comprehensive research on these two design methods,and the content is as follows:First,under the two-body model,a preliminary design of the high-thrust Earth to Mars transfer orbit is made.Then,based on Lambert’s theory,a simulation analysis of the Earth to Mars transfer trajectory of the UAE,the United States,and China has been carried out,and their fuel consumption is compared.In particular,for the period from2020 to 2023,a global launch window has been searched using the contour map method to determine the most fuel-efficient launch date and arrival date of the spacecraft to Mars.In the end,based on the conical splicing method and Lambert theory,the preliminary design of the three-segment orbits of the earth escape segment,heliocentric cruise segment,and Mars capture segment has been completed.Second,for the optimization problem of the high-thrust Earth to Mars transfer trajectory,an accurate dynamic model has been constructed,and the initial state quantity(perigee and velocity)is integrated to obtain the terminal state quantity,which was depicted with the B plane parameters and compared with the target B plane parameters and the initial velocity of the Earth to Mars transfer orbit perigee was corrected using the differential correction method,and the precise design of the Earth to Mars transfer orbit in July 2020 was completed.Furthermore,considering the shape-based method,a low-thrust Earth to Mars transfer track is quickly designed.First,a method based on the inverse sixth-order polynomial is given.This method can meet the boundary conditions of the spacecraft’s initial and final position and velocity,and the calculation speed is very fast.Then,the thrust limit and dynamic equation constraints are added,and a Fourier series-based orbit design method is given: the initial value of the Fourier coefficient is fitted by a cubic polynomial,and then the sequential quadratic optimization algorithm is used to complete the solution.Finally,the Gauss pseudo-spectrum method,which is more popular in recent years,is introduced to complete the optimization of the low-thrust Earth to Mars transfer trajectory.This method discretizes the optimal control problem of low-thrust orbit transfer and transforms it into a nonlinear programming problem.The thesis uses the pseudo-spectral method package GPOPS to solve this problem.The results show that the orbit requirements obtained by Gauss pseudo-spectrum method obviously better than the orbit obtained by the shape method,which provides a reference for orbit optimization.