Resilient Extra-Terrestrial Habitat Design Using a Control Effectiveness Metric
Abstract
Extra-terrestrial habitats will be embedded in challenging environments and involve complex and tightly coupled combinations of hardware, software, and humans. Such systems will be exposed to many risks, both known and unknown, and anticipating all failures and environmental impacts will not be possible. In addition, complexity and tight coupling in these systems means space habitats are likely to experience system accidents, which arise not only from the failure of individual components but also from the interactions among components. Therefore, we propose a control-theoretic approach to resilient space habitat design, which is grounded in system safety engineering and goes beyond event and component-centric failure models underlying conventional risk-based design. We model the system from a state-based perspective where the habitat is in one of four distinct types of states at a given time: nominal, hazardous, safe, or accident. The habitat transitions from a nominal state to a hazardous state via disruptions, and further to safe and accident states via triggers. We use safety controls to prevent the system from entering or remaining in a hazardous or accident state, or to transition the system into a temporary safe state or back to a nominal state. We develop a safety control option space, from which designers choose the best control strategy to meet resilience, performance, cost, and other system goals. We show the development of a control effectiveness metric, which is defined to assess how well safety controls address the hazardous state or disruption for which they are designed. The control effectiveness metric is one dimension of the overall hazard mitigation evaluation, which should also include aspects like cost and launch mass. We validate this approach by assessing individual safety controls in the Modular-Coupled Virtual Testbed (MCVT). This physics-based habitat simulation models complex disruption scenarios which include unique combinations of hazardous states and safety controls. The MCVT allows for the activation of individual (and sets of) safety controls of varying control effectiveness values to evaluate habitat resilience under different control architectures. Using this simulation, we evaluate the control effectiveness metric to determine whether the definition is appropriate to select safety controls that lead to desired habitat resilience. Completing the validation of this metric is the first step towards the validation of the overall control-theoretic approach to resilient space habitat design.
Degree
M.Sc.
Advisors
Marais, Purdue University.
Subject Area
Design|Aerospace engineering|Alternative Energy|Ecology|Energy|Planetology|Statistics|Systems science
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