Session: 10-05-01: Applied Mechanics, Dynamic Systems, Experimental and Computational Methods, Modeling and Virtual Simulations of Dynamic Structures, Advanced Materials and Testing

Paper Number: 166485

Ensuring Nuclear Containment: Impact and Stress Analysis of Multi-Mission Radioisotope Thermoelectric Generators 

A Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) is a highly reliable power system designed to provide continuous electrical energy for space missions operating in both planetary atmospheres and deep space environments. By utilizing the decay heat of a radioisotope fuel source, MMRTGs convert thermal energy into electricity via thermoelectric modules, making them essential for long-duration missions where solar power may be impractical. These systems must function efficiently for up to 14 years without maintenance while enduring extreme environmental conditions, including the mechanical stresses of launch, the vacuum of space, thermal cycling, and the dynamic loads associated with planetary landings and rover-based mobility. Given that MMRTGs contain radioactive materials, their structural integrity is of paramount importance, not only to ensure mission success but also to prevent the release of nuclear material in the event of mission failure, such as re-entry into Earth’s atmosphere or an unplanned impact event.

The primary objective of this study is to assess the structural integrity and resilience of an MMRTG under a variety of impact scenarios through finite element analysis (FEA). Specifically, this work evaluates the MMRTG’s ability to withstand gravitational forces during launch and descent, direct drop impacts that may occur during planetary landing failures, and vibrational stresses experienced during long-term rover traversals over Martian terrain. By simulating these conditions, the study aims to identify potential failure points and optimize the MMRTG’s structural design for enhanced safety and reliability.

This research employs a computational approach using COMSOL Multiphysics to develop a high-fidelity 3D model of an MMRTG, incorporating realistic material properties and boundary conditions based on publicly available data from sources such as NASA and the U.S. Department of Defense. The finite element model simulates time-dependent shock loads, vibrational responses, and stress distributions across critical structural components, including the heat source containment shell, thermoelectric modules, and outer protective casings. To ensure accuracy, the analysis considers a range of impact velocities and angles representative of worst-case failure scenarios. The study also evaluates different material compositions to determine the most resilient configurations capable of withstanding extreme mechanical and thermal loads while maintaining containment integrity.

Preliminary results indicate that the structural performance of the MMRTG is highly dependent on impact orientation and external casing material properties. High-stress concentrations were observed in specific regions of the generator under direct drop impact conditions, suggesting that reinforcement in these areas could significantly enhance durability. Additionally, vibrational analysis revealed that certain frequencies could induce resonance effects, potentially leading to long-term fatigue failure if not properly mitigated. These findings provide valuable insights into the optimization of MMRTG design, allowing for the selection of improved materials and structural configurations that enhance both safety and operational longevity.

The contributions of this research are twofold. First, it provides a comprehensive computational framework for evaluating the mechanical resilience of MMRTGs, offering a methodology that can be extended to other space power systems. Second, it informs future design modifications that could enhance mission reliability and nuclear material containment, reducing risks associated with potential failures. By improving the structural integrity of MMRTGs, this study contributes to advancing the engineering of space power systems, ultimately supporting more robust and safer long-duration space missions. Future work will expand the analysis to include experimental validation and additional mission-specific failure scenarios to further refine the predictive capabilities of the computational model.

Presenting Author: Christopher Brown University of New Haven

Presenting Author Biography: Christopher Brown is a graduate student in the Department of Mechanical and Industrial Engineering at the University of New Haven. His research focuses on the shock and impact resilience of Multi-Mission Radioisotope Thermoelectric Generators (MMRTGs) during Martian landings, ensuring their structural integrity and reliable power generation. This work is part of a Nuclear Regulatory Commission (NRC)-funded project aimed at enhancing the safety and performance of radioisotope power systems for space exploration. Christopher is a recipient of the prestigious NRC Fellowship, recognizing his academic excellence and contributions to advancing nuclear energy applications in space technology.

Authors:

Christopher Brown University of New Haven
Sumith Yesudasan University of New Haven