Session: SYMP 4-8: Shape Memory Alloy Applications

Paper Number: 140402

140402 - Shape Memory Alloy Torque Tube Based Thermosyphon for Passive Thermal Control 

Spacecraft tailored for missions beyond low Earth orbit face difficult thermal control challenges. Lunar missions call for systems that can survive the extreme surface temperature differences between the lunar day (400K) and night (100K), meaning the thermal control system may need to reject higher operational heat loads to warm environments during the lunar day when systems are in use and lower heat loads to cold environments during sub-system hibernation at night. Fuel cell power and energy storage systems are pivotal components in the blueprint for future lunar surface infrastructure as they can provide energy storage to delivery power in locations near humans where nuclear power is not an option. However, despite their critical role, fuel cells introduce complexities and raise questions about the long-term viability of the system. Challenges arise from factors like the presence of moving parts and intricate control mechanisms, necessitating solutions to ensure the durability and dependability of the system in the harsh lunar environment.

An innovative solution that addresses the aforementioned challenges includes the utilization of shape memory alloy torque-tube based thermosyphons. Shape memory alloy torque tube-based thermosyphons allow conventional flat plate radiators to be autonomously rotated from a full view of space to a limited view of space based on the temperature of the SMA torque tube alone. By enabling a compact vapor cycle, the shape memory alloy tube harnesses the temperature contrast between the hot and cold regions of the system to act as a heat pump driven by the vaporization and condensation of a working fluid. The radiator actuates as shape memory alloy torque tube takes its austenitic twist angle when the fluid is hot, orienting the radiator panel to maximize its view to space therefore maximizing heat rejection; it takes its trained martensitic twist angle when the fluid is cold, orienting the panels to minimize heat rejection.

Coupled with a fuel cell system, the passive two phase thermosyphon facilitates heat transport while the passive shape memory actuating radiator allows for temperature management, effectively replacing the pumped thermal management system of traditional fuel cell setups. This improves the reliability and operating life of the system by removing pumps and electronics from thermal management, reduces control and complexity through the temperature dependent material behavior and improves mission flexibility by allowing the system to survive the harsh lunar night.

This work considers development of a computational model created to integrate the thermal, mechanical, and advective components of the shape memory alloy torque tube thermosyphon system. This model is used to evaluate the thermal regulation of a fuel cell system operating in a lunar surface setting. Testing results of the shape memory alloy torque tube radiator system will also be reviewed, contributing to advancements in lunar surface operations and thermal management technologies.

Presenting Author: Darren Hartl Texas A&M University

Presenting Author Biography: Dr. Hartl has held joint appointments at the Air Force Research Laboratory as a contracted Research Scientist in the Materials and Manufacturing Directorate and as a Visiting Researcher in the Aerospace Systems Directorate. His work has bridged the topics of advanced multifunctional material systems and their integration into aerospace platforms using genotype–phenotype topological approaches. He has spent five years as TEES Research Assistant Professor in the Department of Aerospace Engineering at Texas A&M and has recently accepted a traditional tenure-track Assistant Professor appointment. His team works on projects ranging from self-folding origami-based structures to self-regulating morphing radiators for spacecraft to advanced actuators for avian-inspired aircraft. Darren has over 15 years of experience working with Shape Memory Alloys (SMAs) and morphing structures. His efforts have included both experimental and theoretical studies and he has worked collaboratively with both governmental and industrial sponsors considering medical, oil exploration, aeronautical, and space-related applications. In his previous appointment as Assistant Director of the Aerospace Vehicle Systems Institute, he has also served the world’s major airframe and propulsion companies in collaboration with governmental agencies to develop novel joint research and development programs benefitting from a common industry voice, including the first ever effort to establish aerospace standards toward the flight certification of shape memory alloys.

Authors:

Darren Hartl
Priscilla Nizio