Trajectory optimization of ramjet missile using pseudo-spectral method

Abstract

This paper deals with ramjet-powered missile system. A ramjet-powered system has very complicated and incoherent thrust characteristics with respect to outer and inner environment during operation. For this reason, ramjet missile has many maneuver constraints and is allowed to be operated within more narrow flight envelope. In this paper, trajectory optimization of ramjet missile is accomplished. The trajectory optimization problem is formulated as a discrete parameter optimization problem. For this formulation, Legendre Pseudo-Spectral method is introduced. This method is based on calculating the state and control variables on Legendre-Gauss-Lobatto (LGL) points. To find the parameterized state and control variables, CFSQP (C code for Feasible Sequential Quadratic Programming) is used as an optimization tool (or algorithm). It is shown that, for this trajectory optimization, trend analysis is performed from thrust characteristics on various conditions and, finally, the trajectory optimization is accomplished with fine initial guess with these results.