Hypervelocity perforation of thin films applicable to debris detection in low earth orbit

The growth in the number of satellites in Low Earth Orbit, coupled with the possibility of their catastrophic disruption, may lead to more orbital debris, which in turn has increased the risk of damage to spacecraft arising from impacts by small pieces of debris. There is thus an urgent need to monitor the small particle population in Low Earth Orbit, using a new generation of dust detectors. Various designs are in preparation, and several use the principle of observing particles via their impact penetration of thin films. Previously, most laboratory studies of penetration of thin films have used spherical impactors for ease. However, these are not representative of the shapes of orbital debris. Accordingly, here, impacts are reported at 5 km s-1, by various shaped projectiles (sizes typically 0.5 – 2 mm) on thin (12.5 μm thick) Kapton films. The shapes used were spheres, rods, cubes and platelets, and represent a selection of the shapes present in the orbital debris population that arises from catastrophic disruption of spacecraft. The size and shape of the holes in the Kapton arising from the impacts, are shown to reflect the size and cross-sectional area of an impactor as it passes through the film; even the presence of angular corners in the impactors can be seen in the holes. However, due to the variable aspect of an individual impactor presented to the film during an impact, identification of the exact 3-dimensional shape cannot be obtained from the 2-dimensional hole. Nevertheless, with minor exceptions it is possible to separate more spherical (i.e., natural dust) impactors from the other shapes (i.e. variously shaped anthropogenic debris).