<p>Establishing permanent and sustainable human settlements outside Earth presents numerous challenges. The Resilient Extra-Terrestrial Habitat Institute (RETHi) has been established to advance the fundamental knowledge needed to enable and design resilient habitats in deep space, that will adapt, absorb, and rapidly recover from expected and unexpected disruptions without fundamental changes in function or sacrifices in safety.</p> <p>Future extra-terrestrial habitats will rely on several subsystems working synergistically to ensure adequate power supply, life support to crew members, manage extreme environmental conditions, and monitor the health status of the equipment. To study extra-terrestrial habitats, a combination of modeling approaches and experimental validations is necessary, but deep-space conditions cannot be entirely reproduced in a laboratory setting (e.g., micro-gravity effects). To this end, real-time multi-physics cyber-physical testing is a novel approach of simulating and evaluating complex system-of-systems (SoS) that has been applied to investigate the behavior of extra-terrestrial habitats under different scenarios (e.g., meteorite strikes). One of the most critical components which determines the success of the cyber-physical testbed is the transfer system serving as an interface between the physical and cyber substructures.</p> <p>Through this work, a dedicated thermal transfer system has been designed and constructed to provide realistic thermal boundary conditions to the physical habitat according to the real-time simulation results from cyber substructure of the habitat. The extreme temperatures to be found at the interface between the external protective layer of the habitat (cyber) and the interior structural elements (physical) are emulated by means of a cryogenic chiller and an array of cooled panels that cover a dome-style structure. Moreover, the overall architecture of the cyber-physical testbed, the partitioning of the virtual and physical environments, and interface schemes were also established. The experimental results obtained from the thermal transfer system prototype setup were analyzed and interpreted to generate meaningful recommendations for future development and application of the full-sized testbed.</p>

<p dir="ltr">To establish a long-term human presence on the Moon, it is necessary to have habitat systems that function effectively under challenging conditions and have sufficient autonomous technologies for fault detection and intervention. However, evaluating these habitats presents challenges due to their pervasive interdependencies and the harsh environmental conditions they must withstand. Thus, innovative testing techniques are vital to understanding and capturing the complexities these systems will encounter. </p><p dir="ltr">Thermomechanical real-time hybrid simulation (RTHS) provides unique opportunities to observe realistic behaviors and interdependencies, train models, test ideas, and validate methods. It is a cost-effective and accessible cyber-physical testing method that allows for the simultaneous experimental and computational modeling of systems, offering a comprehensive observation of their behavior under extreme dynamic conditions. This dissertation presents the development and experimental validation of a novel thermomechanical RTHS method to assess the multi-physics response of lunar habitat systems due to disruptive events. It outlines the conceptual framework, modeling approaches, and experimental considerations crucial to establishing the two-way coupling between a numerical and a physical subsystem through an innovative thermal transfer system. </p><p dir="ltr">The thermal transfer system utilizes a thermal actuator to impose distributed thermal loads on the experimental subsystem. The thermal actuator is identified considering switching-mode continuous dynamics for cooling and heating conditions. A switching control system is then developed to experimentally enforce the desired thermal conditions across different thermal cycles with minimum tracking error, adjusting the gains of the controller in response to varying temperature conditions. Furthermore, this dissertation demonstrates how to establish control and performance requirements for RTHS methods to effectively evaluate the realization of interface boundary conditions and determine acceptance criteria to perform RTHS tests with high confidence. </p><p dir="ltr">The RTHS method is experimentally implemented and validated through a series of scenario tests that simulate the cascading thermomechanical effects on a lunar habitat after a micrometeorite impact that damages its structural protective layer. These realistic tests aim to evaluate fault detection and decision-making methods in response to such disruptive events. Thus, using switching dynamic modeling, the RTHS problem formulation is designed to have numerical damage and repair capabilities, allowing interaction with these fault detection and intervention methods. The scenario results obtained through thermomechanical RTHS reveal behaviors and interactions that are not captured through purely numerical simulation or traditional experimental approaches. Through the experimental implementation of these scenario case studies, the thermomechanical RTHS method developed is the first of its kind to experimentally execute the effects of damage and repair intervention strategies in real-time on a numerical subsystem while simultaneously imposing the cascading effects on a physical specimen. </p><p dir="ltr">The findings of this dissertation advance our knowledge and offer insights into developing cost-effective and accessible cyber-physical methods to test novel ideas and technologies, thereby empowering and supporting space resilience and autonomy research. </p>

<p>Real-time hybrid simulation (RTHS) has demonstrated certain advantages over conventional large-scale testing. In an RTHS, the system that is under study is partitioned into a numerical and a physical substructure, where the numerical part is comprised of those elements that are easier to model mathematically, while the physical part consists of those that present a complex behavior difficult to capture in a numerical model. The most complex part of this study is the isolation system, a technology used to protect structures against earthquakes by modifying how they respond to ground motions. Unbonded Fiber Reinforced Elastomeric Isolators (UFREIs) are devices that can accomplish this task and have gained attention in recent years because of their modest but valuable features that make them suitable for implementation in low-rise buildings and in developing countries because of their low cost. Our end goal for this work is to enable the testing of scaled versions of these elastomeric isolators to understand their behavior under shear tests and realistic loading. </p> <p>A testing instrument was designed and constructed to apply a uniaxial compressive force up to 22kN and a shear force of 8kN simultaneously to the specimens. A testing program was conducted where four primary sources of signal distortion were identified as caused by the servo-hydraulic system. From these results, a mechanics-based model was developed to understand better the dynamics that the sliding table can introduce to the measured signals accounting for inertial and dissipative forces. Two Bouc-Wen models were implemented to simulate the behavior of the UFREIs. The first only accounts for the hysteretic behavior of the isolator, and the second accounts for the additional nonlinearities found in the isolator’s behavior. These models were assembled in a virtual RTHS which is available to users interested in learning the applications of RTHS of a base-isolated structure with a nonlinear component.</p> <p>An RTHS experiment was conducted in the IISL where the control system comprised a delay compensator and a proportional-integral controller, which exhibited a good tracking performance with minimal delay and low RMSE. However, it can increase the distortion of the oil-column resonance in the measured signals. The simulation captures the behavior of the isolated structure for small displacements. However, it underestimates the displacement of the full-scale specimen for large displacements. The RTHS showed a better approximation of the displacement of the full-scale structure than the theoretical behavior approximated by the Bouc-Wen models.</p>