Abstract: A novel on-line planning method is proposed based on the secant method for RLV reentry trajectory design. Constraints during reentry are analyzed, and the stagnation point heat flow, the normal load, the dynamic pressure and the equilibrium glide constraint are selected as the main path constraints, also the heights and the velocities of the initial and terminal points are specified, all of which are expressed in D-V forms. The reference trajectory is then designed as a two-segment piecewise fold line. The secant method is utilized to adjust the turning point of the trajectory rapidly until the gliding distance and the velocity of the terminal point meet the desired values simultaneously. Finally, simulations are conducted for 3 cases with different the gliding distances. Simulation results demonstrate that the proposed method could not only design the on-line reference trajectory in less than 1 second, but also be applicable to a certain range of the gliding distance.

Key words: RLV, Reentry, Reference trajectory, On-line design, Secant method