9. Advanced Features in Solar-Photon Sailing

Thrust acceleration models may be extended by taking the fluctuating interplanetary environment into account through different ways. TSI variations change the level of thrust directly, while ultraviolet spectral irradiance may alter the optical properties of the sail’s reflective material. Such modifications may be modeled as a function of the UV-energy absorbed by unit area of this layer as sailcraft moves. One says that UV-light causes an optical degradation. Solar wind ions, though representing a very small perturbation to sailcraft motion from the dynamical pressure viewpoint, however penetrate throughout the reflective layer, and may bring about some degradation if the absorbed dose is high during the flight. This has the twofold effect of lessening thrust and increasing sail temperature, which is an issue in general. Degradation may be induced by UV-light and ion bombardment at the same time. Though a detailed model is explained, however such topics are only hinted here. Further studies—devoted to a wide analysis of quantitative UV/solar-wind impact on sailcraft trajectories/orbits—are needed also in view of new materials for sail making.