Studies Of Reentry Guidance For A Reusable Launch Vehicle

Future Reusable Launch Vehicles (RLVs) pursue the advanced technologies for improved performance, so more improvements on guidance and control are needed. Even though working very satisfactory, the guidance and control method used in the Space Shuttle system for ascent and reentry flights, requires extensive pre-flight analysis to define the nominal trajectory profiles. It lacks the autonomy and adaptability to cope with non-nominal vehicles and mission conditions needed for future reusable launch vehicles.The guidance design methods may be classified into two main categories: nominal trajectory-based techniques and on-line trajectory prediction schemes. In the first approach, a reference trajectory is de- fined prior to the mission, and during the flight the differences between the desired and observed actual trajectory are input to a controller that keep the vehicle close to the nominal trajectory. The predictive guidance concepts propagate the future trajectory based on current flight states to calculate the control input during the remaining light. Taking advantage of the increased computational capabilities of advanced avionic systems, the predictive guidance concepts will act more superior performance.This paper addresses the study of reentry guidance for the reusable launch vehicle, which has done the following researches:1) The basic theories include the model, the constraints and the controls of the reentry guidance.2) The nominal trajectory-based techniques include the methods to compute the reentry flight corridor, the reference trajectory and the track law of the reference trajectory.3) The Evolved Acceleration Guidance Logic for Entry (EAGLE)is based on the nominal trajectory-based techniques, which transforms the problem into a one-parameter optimization problem.4) The Predictor-Corrector guidance is designed, considering the constraints of heating, pressure and over loading. And using parameter optimization theories the algorithm of designing and solving the parameters of reference profiles is studied.