Geometrical projectile shapes effect on hypervelocity impact

All spacecraft confronts threat of space debris and meteoroids. Spherical projectiles are common shape used to study impact of space debris on spacecraft structures or shielding system. However, real space debris which is a threat to spacecraft is not likely to be spherical. There is a need to study the influence of projectile shape as non-spherical shapes may cause greater damage to spacecraft than spherical projectiles with same impact conditions. The aim of this research is to investigate the effect of projectile shapes focusing on impact velocity in hypervelocity range by numerical simulations. The geometrical shapes of projectiles that were simulated are sphere, cylinder and cube. Projectiles and targets are made of aluminium, 2024. All projectiles have equivalent mass hence equivalent impact energy The impact velocities are 3 km/s, 5 km/s, 7 km/s and 9 km/s. Smoothed particle hydrodynamics (SPH) is applied. The shapes of debris clouds, velocities of debris clouds, residual velocity of projectiles, dimension of target hole after impact, impact induced stress and target failure modes are investigated and compared between different projectile shapes. Shapes of debris clouds generated by impact of cylindrical and cubic projectiles have spike-like in frontal area of the debris clouds, which do not exist in that of spherical projectile. Velocities of debris clouds generated by the impacts of cylindrical and cubic projectiles are higher than that of spherical projectile in hypervelocity impact range, i.e. higher than 5 km/s. The conventional spherical projectile is not the most dangerous case of space debris. With equivalent mass, a cylindrical projectile, with length-to-diameter ratio equal to 1, is more lethal than a spherical projectile. A cubic projectile is more lethal than a spherical projectile and cylindrical projectile, with length-to-diameter ratio equal to 1 and with an equivalent mass.