Experimental setup recreates wide temperature swings of space for heat transfer materials testing

In environments of temperature extremes, dynamic heat transfer through radiation is a crucial aspect of spacecraft design. Several novel variable-emittance coatings, whose infrared emittance can be tuned passively by temperature or actively by external stimuli, have been proposed, but lack a method to be thermally tested in a space-like environment.

Wang et al. developed an experimental setup that tests self-adaptive dynamic radiative heat transfer with variable-emittance coatings in a space-like thermal environment. They used a cold trap to hold samples in a vacuum cryostat. An absorptive black coating and highly reflective tungsten mirrors calibrated the energy consumed by auxiliary components, called the parasitic head load, and heat flux sensor sensitivity. The resulting device can detect coating temperature and variable radiative heat dissipation under different thermal loads in background temperature from 80 to 800 Kelvin.

“Our approach provides a way to directly demonstrate thermal homeostasis and thermal rectification, which are important for maintaining a spacecraft’s temperature within operational range with reduced power consumption,” said author Liping Wang. “We believe this will help experimentally test novel variable-emittance coatings before large-scale manufacturing and application for spacecraft thermal control.”

In a space-like thermal background of 80 K, the tunable vanadium dioxide coating showed a 6-fold enhancement in radiative thermal conductance with a reduced temperature swing by almost 20 degrees Celsius less than static emitters under the same heat loads.

When the thermal background is set to warmer temperatures than the coating, the vanadium dioxide coating suppresses heat transfer with thermal rectification effect.

The group looks to investigate how their testing platform can be used to develop other novel variable-emittance coatings for thermal control of spacecraft.

Source: “Reducing temperature swing and rectifying radiative heat transfer for passive dynamic space thermal control with variable-emittance coatings,” by Liping Wang, Neal Boman, Sydney Taylor, and Chloe Stoops, Applied Physics Letters (2025). The article can be accessed at https://doi.org/10.1063/5.0303297 .