Rocket motor nozzle flow geometry is considered through its influence on the thrust vector control (TVC) performances. Extensive research is conducted using theoretical and software simulations and compared with experimental results. Cold and hot flow test equipments are used. The main objective of the research is to establish the methodology of flow geometry optimisation on the TVC hardware system. Several geometry parameters are examined in detail and their effects on the system performances are presented. The discovered effects are used as guidelines in the TVC system design process. A numerical method is presented for the determination of dynamic response time upper limit for the TVC system based on the gas flow dynamics performances.