Abstract <p>Thermal energy storage is an efficient way for thermal control of near-earth and deep space detectors, but the melting rate is restricted by low heat transfer performance of phase change material (PCM) and disappearance or suppression of natural convection under micro/low gravity. To accelerate melting of PCM under micro/low gravity, graphene nanoplatelet (GNP)-enhanced PCM with fins are proposed. The effects of fin shape, GNP concentration and gravity level on dynamic melting characteristics considering thermocapillary convection are investigated. The results show that the improvement effect of rectangular fins on melting rate is higher than that of triangular fins under microgravity; with the decrease of gravity level, the melting rate is reduced. The presence of GNP significantly promotes the melting under micro/low gravity. At GNP concentration of 0.03 vol%, the reduction of melting time can reach 58.2%, 49.4% and 51.6% at microgravity, moon’s gravity of 1.625&#xa0;m&#xa0;s⁻² and Mars’ gravity of 3.711&#xa0;m&#xa0;s⁻², respectively.</p> Highlights <p>• Graphene nanoplatelet and fin are used to promote melting in micro/low gravity.</p> <p>•&#xa0;Effects of fin shape, GNP concentration and gravity level are analyzed.</p> <p>•&#xa0;Rectangular fins have higher improvement effect on melting rate.</p> <p>•&#xa0;Addition of graphene nanoplatelet can reduce melting time by 58.2%.</p>