Space-based experiments show wax-filled heat sinks keep electronics cooler for longer

An interdisciplinary research team including mechanical science and engineering professor Mickey Clemon from the Grainger College of Engineering at the University of Illinois Urbana-Champaign is investigating cooling methods for heat sinks by performing experiments onboard a satellite currently orbiting Earth.

“University-sponsored satellites have a very low success rate of making it into space, so we’re very happy that we made it into space and that our system works,” Clemon said.

The team has published the recent findings from their ongoing study, “Investigating the performance of a heat sink for satellite avionics thermal management: From ground-level testing to space-like conditions,” in the International Journal of Heat and Mass Transfer.

Thermal management of electronics in space poses a unique set of challenges due to high waste heat generation and the lack of convective cooling in a vacuum. Thus, systems operating in space must either effectively release heat through radiation, or more prohibitively, limit computing.

To address these challenges, the team developed heat sinks that contain a wax-based phase change material that melts within the normal operating temperature range of the electronics. The melting wax is able to store energy more rapidly and keep the electronics cooler for longer.

“We’re testing different duty cycles and cooling regimes with the fixed heat sinks that we’ve put up there,” Clemon said. “The idea is for this to inform the design and operating sequences for other electronics and computing in space.”

The team deployed their test rig onboard a CubeSat, a miniaturized satellite comprised of cubic modules measuring 10 cm per side. The satellite launched in August 2024 (see its operational dashboard here) with several payloads, including the heat sinks, as part of the Waratah Seed Mission.

“We alternate our experiments with those of the other payloads,” Clemon said.

The team’s results thus far are promising—for one, the melting wax significantly increases the time that the electronics can operate within a safe temperature range. Furthermore, the microgravity environment does not impact the orientation of the wax on the heat sinks.

“We’ve developed some simplified models to predict the performance of these heat sinks that may provide a first direction for designers to test their designs against rather than having to build something and test it physically,” Clemon said.

With more experiments planned, the team’s explorations in space will continue.

“Our orbit is about 90 minutes, and because of that we have some sun exposure time and non-sun exposure time,” Clemon explained. “There’s an underlying heating profile from the sun itself, and we want to explore the effect of that on the computing time that’s available for the electronics.”

First author Laryssa Sueza Raffa, studying at the University of Technology Sydney, is Clemon’s Ph.D. student. Second author Matt Ryall represents Mawson Rovers, the team’s industry partner. Additional authors include Professor Iver Cairns at the University of Sydney and Associate Professor Nick Bennett at the University of Technology Sydney.