Skip Reenty Trajectory Planning And Guidance For Lunar-return Vehicle

The reentry speed of lunar-return vehicle is close to the second cosmic velocity, thevehicle fly in this speed will be faced with high overload and heat flux. The lunarsample return mission in the third phase of China’s lunar exploration program as well asthe USA’s next-generation Orion Crew Exploration Vehicle (CEV) lunar exploremission are both going to adopt skip reentry trajectory in order to enhance the ability ofadjusting a large downrange, and reduce the peak of overload and heat flux. Therefore,this thesis studied the reentry dynamic characteristics, reentry trajectory optimizationapproaches and reentry guidance based on lunar return missions. The main resultsachieved in this dissertation are summarized as follows:To simulate a spacecraft’s entry flight, the dimensionless equations ofthree-dimensional motion for a point mass about a rotating Earth are integrated. A largenumber of simulations were done to analyze the impacts of the initial reentry parameterand the control ones on the reentry trajectory, which provides a reference for theselection of reentry initial conditions;In considering of the complexity of constraints and difficulty of choosing the initialvalue, a serial optimization strategies “from feasible solution to optimal solution” basedon Gauss Pseudospectral Method (GPM) was adopted to approach a reentry trajectoryoptimization. Reentry trajectories in different scenarios with different optimizationobjectives were simulated, the simulation results has certain reference value forengineering;A numerical predictor-corrector (NPC) method for trajectory planning andclosed-loop guidance of low lift-to-drag (L/D) ratio vehicles during the skip entry phaseof a lunar-return mission is presented to adjust the large downrange and solve theproblem of. The strategy calls for controlling the trajectory by modulation of themagnitude of the vehicle’s bank angle. A number of issues are identified and addressedthat are critical in closed-loop implementations. Extensive3DOF dispersion simulationsare performed to evaluate the performance of the proposed approach, and the resultsdemonstrate very reliable and robust performance of the algorithm in highly stressfuldispersed conditions.