Trajectory Optimization For Mars EDL And Research On The Entry Guidance

Current Mars exploration mission are developed for the future manned landingon Mars on account of the great significance of Mars exploration.The EDL process is a very important segment of the entire Mars explorationmission, which determines if the vehic le could land safely in a pre-defined location.Mars landers before Phoenix used a ballistic entry, which lead to a landing error ofhundred kilometers. Future manned Mars landing require the accuracy less than100m. Advanced entry guidance algorithm and control technology reduce theparachute deployment position error; in addition, the fuel amount of land ing processdetermine if the vehic le could landing safely。In this paper, trajectory optimization is simulated in entry segment and landingsegment based on the Gauss Pseudo-spectral Method while make the Mars ScienceLaboratory as a model, then traces the entered optimal reference trajectory based onthe predictor-corrector guidance in route. The specific research composes asfollows:Firstly, we set up the environment model of the Martian atmosphere and thevehic le model. Then the dyna mic model of entry segment and landing segme nt isestablished; Fina lly Gauss Pseudo-spectral Method algorithm is studied.Then Gauss Pseudo-spectral Method is used to solve the entry optimaltrajectory which has the features of maximum parachute deployment height. Duringoptimization process, the control variable is bank angle, and meet the initial stateconstraints, termina l state constraints, control constraints, dynamic pressureconstraint and the stagnation point heat flux density constraint.In addition, put the optima l trajectory as reference trajectory,Predictor-Corrector guidance in route is used to trace the reference trajectory. Thenumerical simulation indicates that this guidance algorithm is not sensitive to initia lerrors. And the corrected time is short so that the guidance has the potential foron-line imple mentation.Finally, Gauss Pseudo-spectral Method is used to solve the landing optimaltrajectory which has the features of minimum fuel. During optimization process, thecontrol variable is thrust force angle and thrust force ratio, and meet the initia l stateconstraints, terminal state constraints and control constraints.