According to ScienceAlert, researchers conducted atmospheric experiments to simulate weightlessness, using liquid nitrogen as a safe model for cryogenic liquids. The belief was that weak gravity would make boiling less effective at transferring heat, because bubbles would not rise and move away from the surface as they do on Earth.
But the result was partly the opposite. The researchers found that boiling became more effective in removing heat within certain limits, because the bubbles remained close to the hot surface, which kept a very thin layer of liquid between them and the surface, and helped improve heat transfer.
Researcher Youngseob Song from the University of Florida said that boiling appeared to be more effective up to a certain point, which is the opposite of what was expected. But the problem is that the safety limit drops quickly, which means that the system may work efficiently for a short period and then suddenly collapse if the temperature exceeds a certain level.
Under conditions of weak gravity, the maximum amount of heat that liquid nitrogen can handle was reduced by 65% compared to experiments on Earth. The reason is that the bubbles that remain on the surface may begin to contact each other, drying the surface quickly, leading to the collapse of the cooling mechanism.
The importance of the study is that it helps design safer systems for long space missions, where fuel and electronics must be maintained at appropriate temperatures. It also suggests that the design of the material surface itself may be a key factor in controlling boiling and cooling.
The researchers used a silicon surface coated with silicon dioxide and highly polished to reduce microscopic defects that might affect bubble formation. This allowed them to isolate the effect of gravity more clearly compared to previous experiments that used metal surfaces filled with fine details that might change the results.
The team believes that developing special surfaces may help in the future to delay the boiling of fuel inside spacecraft tanks, by modifying the surface structure and chemistry.
The bottom line is that boiling in space is not always weaker as was thought. It may improve cooling temporarily, but it reaches the point of danger much more quickly, which makes understanding it necessary before sending longer and more complex missions beyond Earth.
