Predicted thermal response of a deployable high-strain composite telescope in low-Earth orbit

Abstract

In recent years, in parallel to Earth Observation (EO) consolidating its role in space applications, spacecraft miniaturisation has been gaining increasing popularity. Smaller satellites represent the ideal platform for cost-effective and relatively quicker technology demonstrations. Furthermore, the perspective of high-volume production would simplify the design of constellations made of identical spacecraft in order to improve the revisit time. Optical payloads could be enhanced by using deployable systems based on carbon fibre-reinforced polymer (CFRP) tape-springs, which are very compact before deployment and highly stable in their extended configuration. In a previous work by the authors, an engineering model of a telescope intended for CubeSats was fabricated and tested. In this paper, the coefficients of thermal expansion (CTE) found experimentally by the authors were implemented in the Finite Element (FE) model via the mathematical framework of the Classical Laminated Plate Theory (CLPT). Thermally-induced distortions of the deployed telescope were analysed numerically for different illumination conditions in low-Earth orbits. The orientation of the assembly with respect to the radiation was found particularly critical. An uncertainty analysis that took into account composite material properties errors was carried out. The results indicated that the predicted response lies in a wide range of uncertainty, which can be detrimental regarding the fulfilment o mission requirements. The impact of different thermal control finishes was evaluated, and the overall response over the spacecraft lifetime was heavily affected by absorptivity degradation. Alternative cross-sections rather than semi-circular tape-springs were implemented in the model, although the increased bending stiffness mainly affected the temperature distribution and showed only a minor impact on the deformations.