Return Trajectory Design Of Cargo Spacecraft And Sample Return Capsule

This dissertation studies the reentry trajectory optimization of cargo spacecraft and characteristics sample return capsule, and reentry dynamic characteristics of six degrees of freedom based on the products returning to earth from space station missions. The main research results are as follows:The ballistic reentry dynamic characteristics of spacecraft are studied. 1) The differential equations of motion for the spacecraft are established in the polar inertial coordinates system and the rotating coordinate system. After that, the dynamic equations are normalized. 2) The reentry trajectory characteristics are analyzed under different initial conditions and drag coefficient.A reentry trajectory optimization approach using Two Point Boundary Value Method is studied. 1) Based on the optimal control theory, the necessary and sufficient conditions for the optimal trajectory are derived, and the optimal control problem to be resolved is transformed into two point boundary value problem. 2) The optimal control models for the shortest time of transition orbit and the minimum fuel consumption transition orbit under the fixed terminal time are established. 3) Genetic algorithm is applied with simplex algorithm to solve two point boundary value problem. 4) The trajectory optimization approach is applied to optimize the transition orbit, and then the minimum fuel consumption transition orbit under the fixed end-time and terminal constraints is found. 5) The reentry trajectories optimization of the sample return capsule and cargo spacecraft direct entry into earth atmospheres from the space station are studied.A reentry trajectory optimization approach using Multiple-phase Gauss Pseudospectral Method is studied. 1) The mathematical model of Multiple-phase Gauss Pseudospectral method is established. 2) The dissertation studies the theories and formulated the models for the spacecraft reentry trajectory optimization considered the path constraints and terminal constraint. 3) A pipelining and segmenting trajectory optimization approach based on Multiple-phase Gauss Pseudospectral method is applied to solve the optimal trajectory. 4) The reentry trajectory optimization of the sample return capsule entry into earth atmospheres by cargo spacecraft is studied.The dynamic characteristics of six degrees of freedom for sample return capsule are studied. 1) The equations of motion for six degree of freedom model are established, including the equations of parameters. 2) The influence of center mass position and rotation on the posture is studied based on two different configurations of sample return capsule.Some research has been done in cargo spacecraft and sample return capsule reentry. The models, calculation methods, the simulation results and conclusions can be references in sample return missions.