Operating Environment

Abstract

The space transportation systems and their subsystems have to perform normally under all kinds of adverse environments during their operation in flight. The vehicle experiences very severe external environments during atmospheric regime of flight and subsequent to that faces steady and dynamic loads during the remaining phases of flight till injection of satellite. The vehicle structure has to withstand all these extreme flight environments to achieve the mission successfully. To counteract the disturbance and to achieve the intended function, the various subsystems have to stretch their functional limits. The additional response caused by such efforts influences the performance of other related subsystems. Similarly, performance dispersions of a particular system have functional impact on other subsystems. Therefore, there is a strong coupling between environment and performance of subsystems in the vehicle. The disturbances are originated either from the external source to the vehicle or from a specific system within the vehicle which acts on the vehicle. The vehicle and subsystems have to be designed to operate against the expected environment disturbances. Typical external operating environments are gravity, atmosphere and aerothermodynamics. Atmospheric wind has specific characteristics and has major influence on the performance vehicle systems. The full understanding of the thermal environment which can cause severe effect on the performance of the subsystems is essential. Dynamic environments experienced by the vehicle systems, by both external and vehicle internal sources have the potential to induce the coupling between subsystems which can cause severe degradation in performance and at times failure too. This chapter describes in detail all such external, internal and dynamic operating environments experienced by the vehicle subsystems. How to deal with all such hostile environments during the design phase and how to enhance the robustness of the systems to work in such environments are discussed. Methodologies for understanding the vehicle operating environments thoroughly, predicting them accurately and utilizing those values in the design and qualification process are explained. The various parameter dispersions to be considered for the vehicle design and overall mission are also discussed.