Terrestrial accelerator facilities can generate ion beams which enable the testing of the resistance of materials and thin film coatings to be used in the space environment. In this work, a $$\hbox {TiO}_2$$ TiO 2 /Al bi-layer coating has been irradiated with a $$\hbox {He}^+$$ He + beam at three different energies. The same flux and dose have been used in order to investigate the damage dependence on the energy. The energies were selected to be in the range 4–100 keV, in order to consider those associated to the quiet solar wind and to the particles present in the near-Earth space environment. The optical, morphological and structural modifications have been investigated by using various techniques. Surprisingly, the most damaged sample is the one irradiated at the intermediate energy, which, on the other hand, corresponds to the case in which the interface between the two layers is more stressed. Results demonstrate that ion energies for irradiation tests must be carefully selected to properly qualify space components.

A lightsail accelerated via directed energy is a candidate technology to send a probe into the deep space in a time period compatible with human life. The light emitted by a ground-based large-aperture phased laser array is directed onto the lightsail to produce a thrust by transferring the momentum of the incident photons. Here we demonstrate that optimized multilayer structures allow ultralight spacecraft being accelerated by laser radiation pressure up to 20% of the light velocity, and eventually even above, as long as a compromise between efficiency and weight is achieved. Layer materials are selected to provide high reflectance in the Doppler-shifted laser wavelength range as well as high emissivity in the infrared, this last characteristic being required to survive to the temperature increase during the acceleration phase.

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