A major task of engineering is the creation of innovative systems to solve societal problems. Yet many major corporations miss the delivery dates of their newly developed systems and exceed the originally estimated development cost. The likely reason for this is excessive reliance on experience and detailed analyses of sub-systems while ignoring the system-level design issues, especially the coupling of functional requirements (FRs) in the system architecture. A rigorous construction of system architecture and the use of a more formal, theory-based approach have led to systematic development and deployment of large complex systems at minimum cost within the allotted development time. In this paper, three case studies involving large, highly innovative systems are presented to demonstrate the power of rational design and system development: On-Line Electric Vehicle (OLEV), Mobile Harbor (MH), and Mixalloy. The three systems presented in this paper were designed and developed based on axiomatic design theory. OLEV and MH were designed and deployed in two years at KAIST. Mixalloy, a dispersion-hardened Cu/TiB2 alloy, was developed and commercialized in less than four years by MIT-connected colleagues near Boston; we created materials-processing techniques for the alloy, constructed the equipment and the factory for mass production, and sold the product. These three innovative systems were developed and deployed at minimum cost and on time because in each case the entire system was designed based on a firm theoretical foundation for system development and rigorous checking of the system architecture.