Framework for measuring complexity of aerospace systems

We propose a framework for measuring the complexity of aerospace systems and demonstrate its application. A measure that incorporates size, coupling, and modularity aspects of complexity is developed that emphasizes the importance of indirect coupling and feedback loops in the system. We demonstrate how hierarchical modular structure in the system reduces complexity and present an algorithm to decompose the system into modules. The measure is tested and found to be scalable for large-scale systems involving thousands of components and interactions (typical in modern aerospace systems). We investigate the sensitivity of the measure and demonstrate the ability of the framework to identify incorrectness in system representation. The merits of the framework are exemplified through a case study comparing three spacecraft. The framework provides the designer with three key capabilities that can positively influence the aerospace (or other) design process: the ability to identify complex subsystems, the ability to classify misrepresentations, and the ability to trade-off commercially of the shelf (COTS) and non-COTS components.