Phugoid dynamic characteristic of hypersonic gliding vehicles (Q543262)

This paper focuses on the phugoid dynamics of high lift-to-drag ratio vehicles gliding at hypersonic speed; it is assumed that the vehicle motion takes place at a non-rotating, spherical, homogeneous earth with a static atmosphere, and the slip angle is zero. Then the dynamic equations are simplified and the force function equation is deduced. When the initial states do not satisfy the equilibrium glide condition or a perturbation occurs, the dynamic characteristic is analyzed through linearization and generalized multiple scales methods. Linearization theory is applied to analyze the characteristic of the motion, and the phugoid mode is found to be stable. An analytical solution of flight path angle as a function of speed is derived based on general multiple scale theory. The analytic solutions for the equilibrium glide of hypersonic reentry is found to be in good agreement with the numerical simulation. It yields the following conclusions: When the initial states do not satisfy the equilibrium glide condition or a perturbation occurs, a damped oscillation along the equilibrium glide trajectory would occur. The damping diminishes as the speed decreases. The number of oscillations is decided by the lift-to-drag ratio, the initial altitude and the initial/final speed.