Spin-Modulated Thermoelastic Response of a Flexible Spacecraft Appendage Under Attitude-Dependent Solar Radiation

Solar radiation can induce circumferential temperature gradients and thermoelastic bending moments in lightweight spacecraft appendages. For spinning spacecraft, this thermal excitation is periodically modulated by spin motion and may amplify flexible response when the modulation frequency approaches a structural frequency. This study investigates the spin-modulated thermoelastic response of a spacecraft with a circular thin-walled flexible appendage under attitude-dependent solar radiation. A reduced-order rigid-flexible-thermal model is formulated by coupling rigid-body attitude motion, assumed-mode appendage deformation, first-harmonic circumferential temperature perturbations, and the resulting generalised thermoelastic bending moment. Long-time simulations, spin-period response sampling, degraded-model comparisons and modal energy/work diagnostics are used to identify the dominant response mechanism. The results show that the post-transient flexible response is governed mainly by spin rate, while the initial solar-incidence angle modifies the local response classification in the sampled high-spin region. Representative high-spin loss-of-admissibility cases lie near the first bending-frequency region, where the retained structural energy and positive thermoelastic work input are concentrated mainly in the first bending mode. Removing deformation-dependent solar-incidence feedback does not eliminate these cases, whereas suppressing thermoelastic bending does. Thus, spin-modulated thermoelastic bending is the essential pathway by which attitude-dependent solar radiation amplifies appendage response.