In the deep, dark depths of space, electronics and fuel can still get hot — a lot. As plans are made for longer missions and more advanced technological systems, one of the key areas scientists want to better understand is what happens to ultracold cryogenic liquids when they boil. These liquids are used as rocket fuel and to cool electronic devices, for example, but at the moment, we don’t know enough about their boiling behavior in microgravity. A new study investigating just that, in a series of aerial experiments, has turned up some surprising results. The findings are published in npj Microgravity. We know that boiling liquids behave strangely in space; we have seen it happen before. With less gravity, convection does not circulate heat through liquids as easily. And bubbles don’t come off surfaces as easily; They are less buoyant, so they don’t float like they do on Earth. Boiling bubbles behaved differently in microgravity. (Reza et al., npj Microgravity, 2026) Therefore, one could reasonably assume that low gravity would also reduce the cooling capacity of those space bubbles because they cannot transport heat as quickly. But the researchers found the opposite: Reduced gravity improved heat removal under certain conditions. That is, until a heat threshold was exceeded and boiling became unstable. “What we found is that to some extent, boiling actually became more effective, which was the opposite of what we expected,” says mechanical engineer and lead author Youngsup Song of the University of Florida. “The problem is that the security limit drops sharply. Both halves are important if you are designing real hardware.” Here liquid nitrogen was used as a safe and reliable substitute for all cryogenic liquids, and experiments were carried out in parabolic flights. that simulate weightlessness. frameborder=”0″ enable=”accelerometer; autoplay; writing on clipboard; encrypted media; gyroscope; picture in picture; web-share” referrerpolicy=”strict-origin-when-cross-origin” enablefullscreen> The researchers compared the data from these experiments with equivalent tests conducted in the laboratory, on dry land under normal gravitational pull. “Because we lose buoyancy in reduced gravity, we expected boiling to become less effective across the board,” Song says. But that’s not what they found. Bubbles started forming earlier and heat transfer improved in near-gravity conditions. zero. “Our hypothesis is that the bubbles stop floating, so they stay on the surface,” Song says. “When the bubbles are on the surface, there is a small liquid gap between the bubble and the heater, and that liquid layer is so thin that it can improve heat transfer.” to bond, they dry out the surface faster and cause the cooling mechanism to collapse. Reduced gravity is an advantage for heat transfer, until it isn’t. There are limitations to consider here: only nitrogen was tested, and yet in short parabolic flights, the data collected will be useful for future models as researchers design equipment for a more efficient and safer space. Most importantly, in their experiments, Song and his colleagues used a silicon wafer coated with silicon dioxide as a surface. of heating, polished so that it is essentially free of microscopic defects and cavities. Previous experiments have relied on standard metal surfaces that have small imperfections, which affect the formation of bubbles, leading to contradictory results that cannot isolate the effects of gravity. Without MassWith fuel, for example, the further we want to explore beyond the Earth, the longer the propellant will need to stay below its boiling point, something that surface design could help with. to see if we can delay the boiling in the storage tank,” Song says. [tuning] Surface characteristics, such as structures and chemistry, to suppress boiling.” The research was published in npj Microgravity. This article was fact-checked by Rachel Garner and edited by Clare Watson. While we are proud of our process, we are only human. If you spot an error, please let us know.
