Aerocapture Orbital Optimization And Orbital Keeping For Mars Explorers

Because the explorer have various constraints when crossing the Martian atmosphere,if the constraints are not met during aerocapture,the explorer will be destroyed.In addition,the different capture orbits will have a significant impact on the final capture results during aerocapture.After the explorer is successfully captured and enters the orbit,the orbit will continue to drift due to various perturbations.Without orbital keeping,the explorer will be seriously affected.Even the explorer falls to the surface of Mars.This dissertation studies the optimization of aerocapture orbit and the orbital keeping.The main contents are as follows:For the aerocapture of the Mars explorer,an improved pigeon algorithm is proposed to optimize the aerocapture orbit.Aiming at some shortcomings of the original pigeon algorithm,a more practical improved algorithm is proposed,and the parameter values of the improved algorithm are analyzed.Considering the terminal constraints and process constraints required for successful aerocapture,the energy optimal performance index for the acquisition orbit optimization is proposed based on the speed increment required for the orbital transfer from the post-acquisition orbit to the target orbit.Finally,the improved pigeon algorithm is used to optimize the aerodynamic capture orbit.The optimization results show that the proposed improved pigeon group algorithm can effectively optimize the aerodynamic capture orbit.In view of the orbital keeping problem of Mars orbit,considering the influence of various perturbation factors on the orbit around the Martian environment,the influence of the dominant Martian shape perturbation on the eccentricity and the perigee angle is analyzed.A method for orbital eccentricity and perigee angle is proposed based on the small thrust without changing the number of other orbits.The stability range that can be achieved when the eccentricity is maintained by a small thrust is used when the initial values of the orbital roots are different.For the case where the eccentricity of the orbit and the initial value of the perigee angle are far from the equilibrium point,a orbital controller is designed to ensure that the eccentricity and the perigee angle can quickly converge to the equilibrium point atany initial value.Finally,the theoretical analysis of eccentricity oscillation and perigee amplitude drift caused by Mars shape perturbation is verified by numerical simulation,and the proposed method of small thrust for orbital maintenance and the effectiveness of the designed orbit controller are proved.