The Terminal Area Energy Management Trajectory Designe And Guidance For A Reusable Launch Vehicle

This paper discusses the trajectory design and the guidance strategy for the return flight of a Reusable Launch Vehicle (RLV). Studies were confined to the Terminal Area Energy Management flight phase, which follows the atmospheric entry phase and precedes the landing phase. The paper has done the following researches.1. Two kind of three-dimensional spirals are used to describe the trajectory of the Heading Alignment Phase (HAP) and spiral parameters calculating formulas are deduced. Prediction of ground track range to runway threshold, which is an essential part of the energy-range guidance concept, is presented.2. According the geometric characteristics of the three-dimensional spiral, a formula was deduced to show the relation of the start point and the terminal point of the trajectory of the HAP. The formula lays a foundation of creating the Heading Alignment Cone (HAC) dynamically in order to increase or decrease the energy-range ratio. So the S-turn flight phase, which is used when the ratio is above the energy-range profile up limit, can be replaced under the condition of that the energy-range ratio is not too large.3. A solution of trajectory re-construction of the HAP has been deduced, under the condition of that a height error exists after the HAC turn phase starts.4. The tangential acceleration formula has been deduced and lateral guidance law has been given when the RLV flies along the trajectory of HAC.5. Two kind of horizontal plane trajectories of the Acquisition Phase (AP), Tangential Trajectory and Arc Trajectory, are discussed and predictors of ground track range are given, respectively. Two kind of vertical plane trajectories of the AP are also discussed: (1) the height of the RLV is a function of the ground range; (2) the height is free. For the second, a guidance law is provided.6. The lateral guidance law of the Prefinal Phase and a predictor of ground track range of the S-turn phase are presented.7. A three Degree-Of-Freedom simulator was built in a Matlab/Simulink environment to confirm the trajectory design and guidance strategy.8. In brief the abort Glide Return to Launch Site of the shuttle is discussed.