The role of mission requirements, vehicle attributes, technologies and uncertainty in rotorcraft system design

Decisions made during the early stages of design have significant impact on the ultimate success of a system yet are made at a time when design information is least certain. Recent work addressed this concern by propagating design uncertainty to the system-level attributes through probabilistic design techniques. This work addressed uncertainty associated with system concepts (vehicle attributes) and technologies. However, it fell short of addressing the key element, which drives system design, namely the mission requirements. Addressing mission requirements alone and in conjunction with vehicle attributes and technologies, along with the uncertainty associated with this design element, is a needed step in making more educated decisions during the system design phase. The research presented in this dissertation proposed two appropriate design environments to address this gap in probabilistic design methods. The first environment, called the Mission Space Model (MSM), concentrated on mission requirements exclusively and established the feasibility of capturing this design element with a metamodeling approach to probabilistic system design. The MSM established the ability to model multiple missions and capture their impact on the system. The second environment, called the Unified Tradeoff Environment (UTE), provided a design environment that integrated the mission requirements with vehicle attributes and technologies. It established the ability to capture the three design elements in one design environment that is amenable to probabilistic techniques. It further allowed assessment of their simultaneous impact on the system under deterministic and probabilistic scenarios. Design guidance was given for constructing and implementing these design environments. In this work, a helicopter variant of the Future Transport Rotorcraft (FTR) was used as the application vehicle for constructing all design spaces and conducting all proof-of-concept studies. A baseline FIR was identified and all Mission Space Models and Unified Tradeoff Environments were constructed around this baseline. These environments were used to investigate the impact of mission requirement, vehicle attribute, and technology changes on the FTR for both deterministic and probabilistic studies. These environments provide the framework for making more educated decisions during early design stages by addressing the key design elements and the uncertainty associated with them.