Solar sail structural analysis via improved finite element modeling

Abstract

Despite the existence of many studies about the structural analysis of a square solar sail, the need for obtaining reliable numerical results still poses a number of practical issues to be solved. The aim of this paper is to propose a new method that improves the existing analysis techniques. In this sense, the solar sail is modeled using distributed sail-boom connections, and its structural behavior in free flight is studied, using the inertia relief method, at different incidence angles of the incoming solar radiation. The proposed approach is able to circumvent the onset of numerical convergence problems by means of suitable strategies. A nonlinear analysis is carried out starting from an initial geometrical configuration in which the whole solar sail is perturbed using a linear combination of the first global buckling modes, obtained with a static eigenvalue analysis. Key points of the procedure are the application of a correct sail pre-stress, a clever choice of the type of elements to be used in the finite element analysis and the use of a suitable mesh refinement. The performance of the new approach have been successfully tested on square solar sails with side length varying from relatively small to medium-to-large sizes, in the range of 10-100 m. A detailed analysis is presented for a reference 20 m  20 m square solar sail, where the paper shows that the suggested procedure is able to guarantee accurate results without the need of additional stabilization technique. In particular, the vibration global mode shapes and frequencies of the solar sail are correctly described even in presence of unsymmetrical loading conditions. In other terms, the numerical analysis is completed without any convergence problem and any disturbing local modes.

Finite element analysis of solar sail force model with mission application

“…Finally, the distribution of residual compressed regions after pretensioning is estimated in Boni et al. 20…”

“…The results have been obtained using software ABAQUS V 6.11 21 with the procedure discussed in Boni et al. 20 and assuming a perfectly reflecting sail film. In fact, a specular reflection model guarantees a simple validation of the numerical data with the results available from the literature.…”

“…In this context, Boni et al. 20 have recently proposed a technique for the deformation analysis of a square solar sail under realistic loading conditions, with the aid of the commercial software ABAQUS V 6.11. 21 In particular, the model of Boni et al.…”

“…21 In particular, the model of Boni et al. 20 is representative of the whole square sail structure, and has been used to investigate the sail structural response in presence of pretensioning, surface, and inertial loads, while the external loads are balanced in accordance with the inertia relief principle. 22…”

“…The aim of this paper is to use the model discussed in Boni et al. 20 to calculate, as a function of the spacecraft attitude, the components of forces and moments acting on a solar sail placed at a sun-sail distance equal to one astronomical unit (this situation is representative of a sail deployment just outside the earth’s sphere of influence). In particular, the FE analysis 20 is used to predict the loads acting on a 20 m × 20 m square solar sail for different values of the angle of incidence of the solar radiation, where the incident and the reflected photons are taken into account with separate contributions.…”