With the rapid expansion of small satellite constellations in Low Earth Orbit (LEO), the demand for resilient computing and high-power electronics in telecom, surveillance, and scientific applications is rising. With increasing power densities, these systems face critical thermal challenges due to the absence of convective cooling and limited surface area for heat dissipation. Effective thermal management solutions are crucial for preventing overheating and ensuring mission longevity. This study presents a rare in-orbit performance assessment of an additively-manufactured triply periodic minimal surface (TPMS) heat sink with phase change material (PCM) for CubeSat thermal control. The University of Technology Sydney and Mawson Rovers’ payload Matilda, launched aboard Waratah Seed-1 satellite in August 2024, integrates a thermal management module comprised of a 3D-printed aluminium TPMS structure with paraffin wax PCM, leveraging both the TPMS’s high surface-area-to-volume ratio for enhanced heat transfer and the PCM’s latent heat storage capacity. To establish a performance baseline, the payload also includes a conventional heat sink with radial planar fins without PCM, representative of widely-used terrestrial cooling solutions, and fabricated with identical metallic mass to the IWP TPMS heat sink. A comprehensive experimental analysis compares the in-orbit thermal behaviour of both modules, while a reduced-order numerical model enables rapid predictions of thermal performance with low computational effort. Results demonstrate that the TPMS-PCM-based module increased the time required for the electronics to reach an 85 °C setpoint temperature by 77% relative to the finned reference module. This substantial operating time extension was reached with an additional 7.0 g of PCM, which corresponds to only 16% mass increase relative to the mass of the metallic heat sinks, highlighting the effective performance of the TPMS-PCM-based thermal management module as a lightweight, high-impact solution. In addition, the reduced-order numerical model reproduced the overall transient orbital response with good agreement. These findings validate TPMS-PCM heat sinks as a scalable, lightweight thermal management solution for CubeSats, offering a pathway to extended operating time and enhanced reliability in next-generation small satellite missions. • Waratah Seed-1: Rare in-orbit test for CubeSat thermal control. • Two thermal management modules in the payload: TPMS-PCM and Fins only. • TPMS-PCM module increased time to reach 85 °C by 77% with just 16% more mass. • Reduced-order numerical model matched in-orbit behaviour with ≤ 6.6°C deviation. • Low computational effort model enables rapid early-stage design of PCM-based CubeSat cooling.
Raffa et al. (Sun,) studied this question.