In this paper, the relationship between the propulsion system and the vehicle structure is investigated. It appears that the structural behavior cannot be neglected when the propulsion sys tem is designed. This is so because the dynamic behavior and stability of l iquid propellant systems can be shown to be dependent on the structural characteristics of the vehicle i t is m o u n t e d in . A general analysis of the interaction between the propulsion sys tem and the vehicle structure is presented and also applied to a monopropel lant rocket-propelled vehicle. The rocket propulsion system and the vehicle structure are analyzed by servomechanism techniques . The complete vehicle sys tem is represented by a block diagram and appropriate transfer funct ions are est imated for the various portions of the sys tem. The complete sys tem is equivalent to a mult i loop servomechanism. The Satche diagram which is analogous to a Nyquist diagram is then used to evaluate the over-all stability. The results of the stability analysis are presented in terms of the natural frequency of the vehicle structure, the combust ion lag, and the distribut ion of mass between various portions of the vehicle.