Onboard generation of reentry drag profile using fuzzy logic

A novel method for fast design of reentry drag profile for reusable launch vehicle (RLV) is developed. A reference drag profile as a function of velocity is designed as a two-segment piecewise line subjects to given initial conditions, path constraints, and terminal conditions. The secant method is utilized to search for the turning point of the profile rapidly until the gliding range and the terminal velocity meet the desired values simultaneously. To ensure the convergence of the search, a fuzzy controller is designed to determine the initial value of the turning point in accordance with a specified gliding range. Numerical simulations for various reentry missions are implemented to demonstrate the effectiveness of the method. The results show that the proposed method could generate a drag profile within 1 second and is applicable to reentry cases with gliding range varying from 3000~15000 km.