2. Integrated Design Aspects of Space Transportation System

The design of a launch vehicle demands close involvement of many disciplines like propulsion, vehicle structures, aerodynamics, flight mechanics, navigation, guidance and control (NGC) systems, vehicle avionics, stage auxiliary systems, thermal systems, etc. It is essential to integrate the requirements of these systems to obtain the best design for the specified mission, and the design iterations are inevitable to arrive at a good design. The interfaces among disciplines are not always well defined. Design of a launch vehicle is essentially making suitable compromises to achieve a good balance between many conflicting requirements and interactions. The design process also has to depend a great deal on analyses, experimentation and simulations. To arrive at an optimum launch vehicle design, it is essential to apply systems approach involving various steps like: (a) mission definition, (b) requirements analyses, (c) subsystems definition, (d) concept analyses and definition and (e) design. Design iterations are necessary to understand the interaction among subsystems, interfaces between various disciplines and relation between various design functions to meet the specified requirements. There are severe dynamic coupling between various systems which further aggravates the complexity of the design process. The clear understanding of the interfaces between various disciplines and their functional interdependencies with respect to various operating conditions is a vital factor. Therefore, it is essential to integrate various subsystems through a structured multidisciplinary process. The complex design problem of a launch vehicle can be handled only by understanding the roles of each of the vehicle subsystems and by utilizing the systems engineering approach right from the concept stage. As space missions are expensive, the quality, reliability and cost should get maximum attention all through the design and development phases. Various aspects of integrated design of STS using systems approach, which are essential to arrive at an optimum, robust and cost effective design of STS are explained in this chapter. An integrated approach for STS design evaluation using suitable vehicle system models to arrive at robust and optimum design is also discussed in brief.