Research On Reentry Guidance Method For Reusable Launch Vehicle

To ensure the safety of the flight and complete the mission, the Reusable Launch Vehicle (RLV)entry guidance system encounters the huge challenges resulted from the extremely complexenvironment in reentry phase. Thus, reentry guidance method for RLV needs to be researchedcomprehensively in this paper.This paper builds up a spherical three degrees of freedom motion model to describe the stateparameters of motion for RLV in reentry phase. Additionally, the aerodynamic characteristic andlift-to-drag ratio characteristic of RLV are also analyzed.According to the influence of flight constraints caused by angle of attack, the angle of attackprofile is designed. The method of reentry corridor planning is researched and the robustness ofreentry corridor is analyzed. The trajectory design method basing on drag acceleration vs. velocity isformed. Due to the difference of task and characteristics in reentry phase, the nominal trajectory isdivided to five phases. The shape and size of trajectory profile depends on reentry flight range. Thealgorithm of trajectory parameters is researched and the robustness of nominal trajectory is analyzed.To guide the RLV to the Terminal area energy management interface, a guidance logic which is acombination of longitudinal guidance and lateral guidance is designed. The longitudinal entryguidance uses roll angle modulation to track the nominal trajectory. The roll angle direction isreversed to reduce the heading deviation in lateral entry guidance. To minimize the effect of the rollangle reversals, a modulation in angle of attack from normal profile is commanded. Depending on therange to flight, the range adjusting logic can choose a corresponding transition trajectory to track.At last, the reentry guidance system simulation environment is built in Matlab/Simulinkenvironment to simulate the RLV entry flight phase. According to uncertainties and constant, theguidance robustness is assessed. The results show that the nominal trajectory and guidance scheme isreasonable, the guidance law is robust.