Research On Re-entry Guidance Method For Reusable Launch Vehicles

Compared with the conventional space transportation systems, the next generation Reusable Launch Vehicles (RLVs) possess higher reliability, lower launch cost, and less turnaround time. They have the ability to achieve rapid, reliable and affordable access to space and receive considerable attentions. To ensure flight safety and guidance precision, entry guidance encounters the huge challenges resulted form the extremely complex environment in entry phase. Thus, entry guidance method for RLVs needs to be researched comprehensively.The entry guidance method for RLV is investigated in this dissertation: First, mass-point dynamics of RLV is established and analysed. Entry guidance problem is proposed and the constraints are determined. The trajectory are divided into several parts according to the different objectives of entry guidance.Then, entry guidance problem is decomposed into three subproblems: longitudinal trajectory planning, longitudinal trajectory tracking and lateral guidance. The algorithm for longitudinal entry corridor computation is introduced, and the factors influenced the longitudinal entry corridor are listed. In longitudinal trajectory planning subproblem, two trajectory transition criterions are introduced, and a new method focused on planning both the angle of attack profile and the bank angle profile is proposed for constraints observance and trajectory smoothness. And in view of the range deficiency resulted from the approximations introduced in longitudinal trajectory planning, a trajectory tracking law is designed via LQR theory to follow the longitudinal reference trajectory and modify angle of attack profile and bank angle profile. In lateral guidance subproblem, a lateral guidance method with good compatibility is introduced and applied to the design of lateral guidance law for RLV.Finally, the above guidance method is demonstrated by numerical simulation under several typical entry scenarios, deflections and disturbances are taken into account.Analyses and conclusions are given at the end of this dissertation. The results of numerical simulation indicate that the entry guidance method researched in this dissertation provides robustness to some uncertainties and has adaptability to various entry missions. It has good potential for further applications.