A new approach to probabilistic risk analysis in concurrent and distributed design of aerospace systems

NASA's space exploration vehicles, like any other complex engineering system, are susceptible to failure and ultimately loss of mission. Researchers, therefore, have devised a variety of quantitative and qualitative techniques to mitigate risk and uncertainty associated with such low-volume high-cost missions. These techniques are often adopted and implemented by various NASA centers in the form of risk management tools, procedures, or guidelines. Most of these techniques, however, aim at the later stages of the design process or during the operational phase of the mission and therefore, are not applicable to the early stages of design. In particular, since the early conceptual design is often conducted by concurrent engineering teams (and sometimes in distributed environments), most risk management methods cannot effectively capture different types of failure in both subsystem and system levels. The current risk management practice in such environments is mostly ad-hoe and based on asking "what can go wrong?" from the team members. As such, this paper presents a new approach to risk management during the initial phases of concurrent and distributed engineering design. The proposed approach, hereafter referred to as Risk and Uncertainty Based Integrated Concurrent Design (or RUBIC-Design), provides a solid rigor for using functional failure data to guide the design process throughout the design cycle. The new approach is based on the functional model of space exploration systems (or any other mission-critical engineering system for that matter) and has the capability of adjusting in real-time as the overall system evolves throughout the design process. The application of the proposed approach to both single-subsystem and multi-subsystem designs is demonstrated using a satellite reaction wheel example.