Study of the shielding performance of a Whipple shield enhanced by Ti-Al-nylon impedance-graded materials

Abstract An improved meteoroid/debris shielding structure for spacecraft is presented, using a bumper constructed from impedance-graded materials. The hypervelocity impact performances of a shield enhanced by Ti-Al-nylon impedance-graded materials and an aluminum Whipple shield are investigated experimentally, using a two-stage light gas gun at velocities of 3.50 and 6.50 km/s. The impact characteristics, including debris clouds, penetration holes in the bumper, and damage patterns on the rear wall are studied. The results show that the shielding capability of a Ti-Al-nylon shield is greater than that of an aluminum Whipple shield where the bumper has the same areal density. A theoretical analysis and numerical simulation are performed to explore why Ti-Al-nylon shields achieve a better shielding performance. The results suggest that a Ti-Al-nylon bumper can generate higher shock pressures and induce a greater temperature increase, which is more effective for fragmenting a projectile. Furthermore, wave propagation in the projectile and bumper is discussed. It is found that the shockwave propagation is affected by the shock impedance mismatch in impedance-graded material bumpers, so that the shock heating effect and the expansion angle of the debris cloud are increased. Materials with lower melting and vaporization temperatures are helpful for improving the performance of a Ti-Al-nylon shield, thereby achieving a sharp increase in the protective capability for spacecraft meteoroid/debris shielding.