Thrust Vector Control for Powered Flight of the Upper Stages

In the powered flight phase of a multistage rocket, a small deviation of the thrust direction will makes an extremely orbit transfer deviation from the target position. For an upper stage of rocket, a thrust vector control (TVC) is strongly affected by the center of mass owing to it is accomplished by a main gimbaled engine. In addition, the real location of the upper stage's mass center is hardly to be precisely obtained due to the limited identification accuracy of the identification system, which deteriorates the performance of the TVC system. To overcome this drawback, this paper develops a novel TVC strategy for the upper stage, making the thrust vector of the gimbaled engine aligns with its command direction. The direction can be obtained by the orbit design system with the center of mass uncertainty during the powered flight. The effects of the center of mass uncertainty on the TVC system, are derived, which include deviations in the command attitude and control torque. Then, a novel TVC strategy is developed for the upper stages to overcome these effects. The proposed method guaranteeing the thrust pointing accuracy under the center of mass uncertainty is verified by numerical simulations.