ABSTRACT
In Chapter 7 on multiobjective optimization, a number of objective functions were simultaneously handled along with constraints for a given discipline. In multidisciplinary design optimization (MDO), two or more disciplines are simultaneously optimized. For example, in rocket design, the disciplines could be structures, aerodynamics, propulsion, control, and mission. Each of these disciplines can have separate optimal requirements. For example, the propulsion discipline can have a constraint on chamber pressure, the structural discipline can have constraints on stresses on the members, and the mission can have trajectory constraints such as on dynamic pressure and heat loads. Further, in MDO there are interactions among the disciplines. For example, the variable dynamic pressure in the trajectory discipline has an effect on load computation in the structural discipline. The idea of MDO is to optimize the design in a global sense. This has the following advantages:
• The time required in the design cycle can be significantly reduced. For example, a given aerodynamic shape will give a certain higher load distribution of certain structural members that may require reworking of these members, which in turn can change the aerodynamic shape. The cycle is iterative and time consuming if the individual disciplines are optimized sequentially. In addition, sequential optimization of disciplines may lead to a suboptimal solution for the whole system. For example, lift distribution along the wing span changes if the aerodynamic and structure disciplines are optimized together instead of considering the aerodynamic discipline alone (Figure 9.1).
