Universe Today
Heat dissipation is one of the unsung engineering challenges of space exploration. Electronics, chemical reactions, and even the Sun’s rays all generate heat on a spacecraft that could potentially damage it if not dealt with. However, the most common way of eliminating heat - convection - isn’t available in a vacuum as it requires material around the object to whisk away the heat. A team of researchers from the University of Illinois and the University of Technology Sydney, as well as their corporate sponsor Mawson Rovers, have produced a series of papers, ground experiments, and a functional CubeSat test, to prove an idea of how to deal with the problem of heat dissipation in space. Their solution uses what in engineering terms is known as a Phase Change Material (PCM), but which has been known to humans for thousands of years as wax.
Their work all starts with the humble heat sink. These hunks of metal are a common sight to any computer gaming fan. Essentially they use the high thermal conductivity of metal (in the case of the papers, 316 Steel) to take some of the heat from whatever is generating it and increase the amount of surface area that heat is being dissipated on. On Earth, that works for both convection (since the fins of heat sinks provide more area for air or water to interact with), but also radiation, as hot things emit infrared light, which also uses up some of their thermal energy.
For a typical heat sink on Earth, the effects of convection far outweigh the effects of radiation. However, in space, there literally is no convection due to the vacuum surrounding the parts, so engineers have to rely entirely on radiation to cool their systems. However, there haven’t been many studies looking at the differences in cooling efficiency between heat sinks under atmospheric pressure and in a vacuum. That’s where the latest paper from the researchers comes in.
Video explaining how heat sinks work. Credit - Advanced Thermal Solutions, Inc. YouTube ChannelIn the paper, published in the International Journal of Heat and Mass Transfer in April, they ran an experiment as well as did some basic numerical modeling. In the experiment, they monitored the temperature of a specially designed electric heater through a variety of different atmospheric conditions, ranging from atmospheric pressure to “high-grade vacuum”, and then ran the heater at two different duty cycles. Unsurprisingly, the temperatures in the vacuum got to be much hotter (up to 66% higher) than those at atmospheric conditions, primarily due to the lack of convection. This trend could be seens as they scaled the pressure from atmospheric down to vacuum, confirming the theory that electronics would be much more prone to overheating in the vacuum of space.
In addition to the experiment, they also developed a simplified numerical model that can calculate what the expected temperature of a system would be based on a few system parameters, and the environmental values surrounding the system (such as pressure). Importantly, this model was computationally simple, allowing it to potentially be utilized on the embedded system of a satellite without contributing too much to the overheating problem it is trying to solve.
A second paper, published back in November 2024, looked at how using a PCM (in this case, paraffin wax) could affect the heat transfer away from the electronics and other critical components. They decided to add the wax directly to the fins of the heat sink through a few holes drilled into the outside of their 3D printed housing. Paraffin wax has a melting point around 55 C, and once it is melted, it will help to add some convection by moving around the fins, allowing heat to distribute more evenly. Critically, it also acts as a heat repository itself, by allowing more thermal energy to be stored in itself rather than keeping it locked up in the heat sink.
Thermal management is a key design consideration for spacecraft, as discussed in the CubeSat Workshop presentation. Credit - CubeSat Workshop YouTube Channel / Boris Yendler, Dr. Benjamin K Malphrus, Nathan FiteThe results from this paper were promising - the experimenters didn’t go all the way to a high-grade vacuum this time, but the heat shrink with the wax performed better than one without at every pressure and at every duty cycle. Even better, the PCM actually worked more effectively in the low-grade vacuum used in this experiment, reducing the temperature of the hot plate by 18 C in vacuum rather than 12.3 C in atmospheric conditions. It also almost doubled the time the heater could run before hitting a high point beyond the reach of most electronics, when compared to a system without a PCM between the heat sink fins. Similarly to the other paper, they also came up with a thermal model describing the operation of the PCM and heat sink together, and again made it usable with a satellite’s on-board computing power.
Those modeling algorithms have already come in handy, because an experiment using the PCM to cool a set of electronics already launched on a 6U CubeSat mission last year. As part of the Waratah Seed Mission, Australia’s first ride-sharing CubeSat mission, it joined other ride-sharing payloads when the mission launched in August 2024. According to the mission’s webpage, it was operational for about 6 months, with the last data coming from a satellite tracking service on February 6th 2025.
Neither of the papers contain any data collected during that mission, but according to a pressure release, Dr. Mickey Clemon, one of the researchers at the University of Illinois, was thrilled that the mission even got to orbit in the first place. Given the pace of innovation in this space, it’s only a matter of time before we see published results from the successful CubeSat mission, and possibly even more innovative ways to keep spacecraft cool during their journeys in the vacuum of space.
Learn More:
UI - Researchers take heat sink experiments to space
UT - Specialized Materials Could Passively Control the Internal Temperature of Space Habitats
UT - Student Led Mission Designs Highlight The Challenges Of Engineering In Space