Columbus debris shielding experiments and ballistic limit curves

Abstract

An extensive Light Gas Gun test campaign has been performed to develop a high resistance shielding to protect the Columbus module - the European laboratory attached to the International Space Station - against the threat posed by orbital debris. In a 3-year period — from Summer '95 to Summer '98 — more than 100 hypervelocity impact tests have been made on a 3-wall shield system, based on an aluminium Whipple Shield plus an intermediate bumper made of Nextel fabric and a Kevlar™-Epoxy™ plate. Two shielding configurations have been selected, which both reported excellent ballistic performance against aluminium spherical projectiles impacting with velocities between 3 and 7 km/s and angles between 0 and 60 degrees. The results showed that the response of a 3-wall system to hypervelocity impacts is more complex than expected. For instance - in the test range - the shielding resistance does not increase linearly with the velocity but shows non-monotonic variations; the ballistic limit shows little oscillations with the increase of the impact angle in the 0 – 45 degrees range as well. The projectile fragmentation level is shown to play a key role in the target failure process. A thorough analysis of the impacted target is on going to gain insight into the complex damage mechanism with particular attention paid to the X-ray pictures taken of the debris cloud formation and evolution. The present paper summarizes the activities performed and the results obtained so far, focusing on the more recently performed experiments.