Biosmart Radiator: An Innovative Solution for Energy Efficiency in Space Systems

In the frame of an ASI co-founded research project (CUP F89J20000970005) an advanced radiator with an innovative biomimetic surface was developed for new-generation satellites and pressurized modules. The project involved Thales Alenia Space in Italy, University of Roma Tre, CNR and C.R.E.O. and ran for 36 months starting in 2021. The research aimed to design and test a novel radiator with embedded a fully passive power saving feature. Main goal was to reach a radiator turn-down ratio lower than 1:4, to tune thermal rejection depending on satellite/module needs. The biomimetic surface enables passive thermal control features by covering the radiator at low temperature (closure at 0°C, exposing a low thermal emitting surface, ε≈0.1) and discovering it at high temperature (opening at 20°C, exposing a white coating, with low solar absorbance α≈0.1, and high thermal emittance ε≈0.8) in a purely passive way. In this way the power budget is reduced and the on-board computer is simplified, especially saving energy during long transient phases. Once on orbit the radiator maximizes heat rejection when fully exposed. Following the definition of requirements, technological specimens, bio-mimetic surface samples and, finally, a full-scale radiator demonstrator were developed and tested. Samples representative of bio-mimetic surface key technologies were optimized, manufactured to a full scale model and subjected to environmental tests, including exposure to protons, electrons radiation and atomic oxygen, to verify their compatibility with space conditions. A full-scale demonstrator was finally built to validate the system. During thermal vacuum testing, the bio-mimetic surface successfully demonstrated petals-like opening and closing based on radiator panel temperature. Thermalization was achieved using a heating fluid (ethylene glycol-water mixture) circulated through 4 mm internal diameter radiator piping. This project demonstrates the feasibility of an efficient radiator for space applications, with significant potential for future thermal control systems.