The process of condensation as we know it here on Earth behaves differently in the extreme conditions of space. Now, European researchers aboard the International Space Station (ISS) are investigating its fundamental nature to mitigate potential hazards to spacecraft electronics.
The microgravity environment of space significantly alters how heat moves through liquids and gases, yet remains poorly understood. Understanding how those changes may affect spacecraft that need to cool down is essential to ensuring the safety of crewed spaceflight, and the recent research offers potential new insights that could pave the way toward such improvements.
Aboard the ISS
The Condensation on Fins experiment is currently underway inside the Heat Transfer Host 2 facility, installed by Northrop Grumman in the European Columbus laboratory at the end of September.
At the center of the project is a fin-shaped piece of metal designed to give researchers the clearest possible view of each fundamental aspect of condensation. The first tests focus on how capillary pressure—the ability of liquid to move through narrow spaces—affects film condensation in the absence of gravity.
Beyond refining the mathematical models that describe condensation, the team envisions practical applications for their findings. These range from improving cooling systems for electronic devices to optimizing industrial coating processes. In the context of spaceflight, their ultimate goal is to increase the efficiency of heat exchangers that maintain spacecraft electronics and life-support systems at safe operating temperatures.
The Shape for Condensation
“We are looking for the best fin shape to maximise heat transfer,” said Brice Saint-Michel, ESA project scientist for this experiment.
Fin-shaped designs have long been used in home appliances—such as refrigerators, air conditioners, and radiators—to enhance heat exchange between gases and liquids. However, the fins used aboard the ISS are larger, standing about one centimeter tall.
“Microgravity conditions allow us to use a large fin without being disturbed by gravity drainage and vapour convection. It is then much easier to see if liquid films take a different shape,” explained Balazs Toth from ESA’s low Earth orbit payload team.
ISS Experiment Design
The fin used in the study is made from an aluminum alloy and soaked in a low-surface-tension refrigerant that can evaporate or condense with minimal heat input. On Earth, this fluid typically pools at the bottom of the fin. In microgravity, however, it distributes evenly across the entire surface. A spongelike material and pump then draw the liquid to the fin’s base, where it is removed and re-evaporated in a closed loop.
“The liquid seems to be attracted to cold surfaces as a safe place to go, unlike what happens with heat transfer on Earth,” said senior researcher Andrey Glushchuk from the Centre for Research and Engineering in Space Technologies at the Université Libre de Bruxelles, Belgium.
“Any thermal system designed with ground standards won’t work in microgravity. We need to create new designs with novel concepts in mind,” he adds.
Two objects made of a thermally stable nickel-iron alloy serve as calibration reference objects for the experiment.
Observing Condensation
Earlier experiments on heat transfer in microgravity over the past two decades provided the baseline information needed to develop the team’s liquid film distribution measurement technique. Using a high-precision interferometer, the researchers can now measure temperature, liquid thickness, and vapor concentration with unprecedented accuracy.
“We needed the constant microgravity conditions of the International Space Station; nowhere else could we have achieved this level of stability, accuracy, and high resolution in our measurements,” says Andrey.
The ultimate aim of the research is to advance the understanding of condensation for real-world applications. Currently, several theoretical models are needed to calculate condensation rates based on variations in liquid film thickness. The team hopes their findings will help unify these into a single, comprehensive model.
“We want a formula that applies to all,” concluded Carlo Saverio Iorio, head of CREST at the Université Libre de Bruxelles, adding that “this is the first time we have had a wealth of data to consolidate it.”
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.