Robust thrust estimation for aerospace vehicle reaction control systems

This paper considers the problem of estimating the thrust from multiple jets firing from the reaction control systems (RCS) used by reusable launch vehicles (RLVs). The thrust estimates can be used for monitoring the health of the RCS, i.e. detecting jet failures. For accurately known state-space dynamics, the Kalman filter provides the optimal estimate in the least-squares sense for the jet thrust. During reentry, however, plant model uncertainties are a major problem for the filter as the vehicle´s aerodynamics vary widely. Consequently, the Kalman filter estimate degrades severely. Transient, robust H_∞ or game-theoretic estimators are shown to give promising estimation and detection performance results for a wide range of Mach numbers and angles of attack when tried on a simulation of the Space Shuttle Orbiter´s RCS