The change trend of state variables,such as flight speed,velocity angle,longitudinal range,altitude,for hypersonic glide vehicle under the condition of skip glide are studied.The numerical solutions of the vehicle state variables are obtained with the fourth-order Runge-Kutta method.The numerical solutions of state variables are fitted with different order orthogonal polynomials,and the analytical solutions representing the variation trend of the state variables are solved.The simulation results show that the mean difference of the root mean square error (RMSE) of the three analytic solutions of flight speed,velocity angle and altitude is 20 m/s,0.1° and 1.5 km respectively,so the variation trend of flight speed,velocity angle and altitude under the skip glide condition can be expressed by the first order orthogonal polynomial.The RMSE of the first order analytic solution of the flight longitudinal range is obviously larger than that of the second order analytic solution and the third order analytic solution,so the flight longitudinal range under the skip glide condition can be expressed by the second order or the third order orthogonal polynomial.

Aiming at trajectory prediction of unpowered gliding hypersonic vehicle and its application requirements, a trajectory prediction algorithm is proposed based on kinetic model. The difficulties of unpowered gliding hypersonic vehicle defense and the function of trajectory prediction are expounded providing a basis for trajectory prediction. The simplified kinetic model is acquired on the basis of force analysis and reasonable shortcutting. The analytical trajectory equations are derived from kinetic model. The framework of trajectory prediction algorithm and the evaluation index are designed. To test and verify the efficiency of the trajectory prediction algorithm, simulation experiments are performed, and the main reasons causing prediction error are analyzed.