Abstract: To address the in-flight trajectory generation and the guidance of reusable launch vehicles in the terminal phase of area energy management, a three-dimensional predictor-corrector guidance algorithm that does not rely on on-line integral prediction and aerodynamic identification is studied based on the parameterized trajectory description. Firstly, the dynamic pressure envelope consisting of the upper and lower dynamic pressure boundaries and the maximum energy boundary is designed, and the dynamic pressure profile generated in the envelope is described by a single parameter. By using the pre-calculation method, the relationship of flight range with the dynamic pressure profile parameter, the bank angle and the energy height is obtained and saved as a three-dimensional data table. Then, according to the current state and ground track parameters, the ground track range of each flight stage is calculated. In the prediction of the range-to-go, to address the range loss of the lateral maneuver and the influence of model deviation, the more accurate value of the range-to-go is obtained by combining the subsection look-up table method and the on-line estimation of the range correction coefficient. Lastly, to ensure the fitness of trajectory while eliminating the range deviation, the continuous updating strategy of multiple trajectory parameters under constraint conditions is studied The simulation results show that the method is insensitive to the initial position and energy distribution, and the accuracy of the terminal position is kept at the meter level. One cycle of trajectory prediction and correction takes no more than 2.3 ms on a PC, indicating a high efficiency of the on-line guidance method. The test for the failure mode illustrates a strong adaptability of the proposed algorithm.

Key words: reusable launch vehicle, terminal area energy management, in-flight trajectory generation, parameterized trajectory, predictor-corrector guidance, look-up table method