Thermoelastic optimisation of fibre-steered composite mirrors for space-based laser communication systems

Abstract

Lightweight, dimensionally stable mirrors are essential for space-based laser communication, requiring concurrent optimisation of mass, stiffness, and environmental stability. This study presents a novel design–manufacture–validation framework that explicitly links variable-stiffness laminate design, manufacturing-induced effects, and experimentally validated optical performance under identical conditions. The novelty lies in providing the first experimentally validated, like-for-like comparison between conventional straight-fibre and Rapid Tow Shearing (RTS) laminates for precision composite mirrors under identical geometry, loading conditions, manufacturing assumptions, and validation procedures. The framework combines finite-element structural, thermoelastic, and hygroscopic analyses with Cure Hardening Instantaneously Linear Elastic (CHILE)-based process modelling and demonstrator-level validation for a 0.50 m composite mirror. Both designs satisfy the > 140 Hz fundamental frequency requirement and exhibit large safety margins. The straight-fibre laminate achieves ∼ 153 Hz and ∼ 69 µm RMS, while the RTS laminate achieves ∼ 145 Hz with comparable deformation and ∼ 11% lower mass. Hygroscopic effects are modest, and cure-induced distortion is dominated by low-order modes. The results demonstrate that RTS enables mass-efficient stiffness tailoring without degrading first-order thermoelastic performance and establish a validated methodology linking modelling predictions, manufacturing variability, and measured surface figure for next-generation lightweight space optics.