Smart inflatable radiator for autonomous, temperature-driven heat dissipation

• A smart inflatable radiator deploys and retracts with temperature changes. • Radiative cooling and a thermosyphon heat pipe demonstrated passive heat dissipation. • The deployed envelope held itself under Earth’s gravity without support. • On the Moon, dissipation reached 253 W/m 2 at 30 °C (86 % of theoretical maximum). Radiative cooling is the only viable heat dissipation method in vacuum environments such as the lunar surface, yet the size of radiator panels is constrained by launch mass and stowage volume. This study presents a smart inflatable radiator that autonomously modulates its radiative area in response to waste-heat temperature changes without active control or power input. The system comprises a leak-proof fluorinated ethylene propylene (FEP) film envelope, a compact water-filled heat exchanger, and a constant-force spring. As the heat transport medium (water) temperature rises, internal vapor pressure overcomes the spring force to deploy the envelope and enlarge its radiative surface; conversely, cooling causes retraction. A gravity-assisted phase-change mechanism passively transports heat from the exchanger to the FEP surface with high thermal conductivity. Under vacuum testing, the inflatable radiator autonomously deployed when the vapor temperature exceeded 34 °C and retracted when it fell below 23 °C. At a heat transport medium temperature of 34 °C, the deployment increased heat dissipation from 26.6 W to 40.2 W (+13.6 W), in good agreement with Stefan–Boltzmann law predictions. Based on the measured overall thermal resistance of 0.037 K/W and the heat transport medium temperature of 30 °C, the radiator is projected to achieve 253 W/m 2 on the lunar surface (86 % of the theoretical maximum). These results demonstrate a fully passive, structurally self-supporting radiator that autonomously deploys and retracts, thereby enabling high-efficiency thermal management for future lunar and deep-space missions.