Shape Memory Alloy Torsional Actuators Enabling Autonomous Thermal Control in Small Satellites

The aim of this study is to investigate the integration of Shape Memory Alloy (SMA) torque tubes into SmallSats’ thermal management systems to passively deploy radiator panels in an autonomous manner. Specific aspects of the investigation are related to material production, thermomechanical characterization, structural integration, and assessment of overall prototype functionalities. Implementation feasibility was evaluated through a 12U CubeSat test case. Starting with NiTi tubes (50.8% at Ni.) intended for pseudoelastic applications, a combined aging and shape-setting heat treatment process was selected to achieve both SME characteristics and an S-shaped geometric configuration. Comprehensive material characterization was conducted using differential scanning calorimetry (DSC) and mechanical testing to evaluate post-treatment phase transformation temperatures (PTTs) and torsional load response. Experimental results demonstrated the actuator’s capacity to fully recover imposed rotations exceeding 90° against resisting torques up to 0.1 Nm. Material cyclic stability analysis revealed rapid stabilization after four cycles, with maintained performance through 80 cycles. The experimental validation culminated in benchtop prototype testing, which achieved an 85° deployment rotation, evidencing the viability of the proposed mechanism.