Simulation study of non-spherical, graphite-epoxy projectiles

The DebriSat hypervelocity impact experiment, performed at the Arnold Engineering Development Center, is intended to update the catastrophic break-up models for modern satellites. To this end, the DebrisSat was built with many modern materials including structural panels of carbon-fiber, reinforced-polymer (CFRP). Subsequent to the experiment, fragments of the DebrisSat have been extracted from porous, catcher panels used to gather the debris from the impact event. Thus far, one of the key observations from the collected fragments is that CFRP represents a large fraction of the fragments and that these fragments tend to be thin, flake-like structures or long, needle-like structures; whereas, debris with nearly equal dimensions is less prevalent. As current ballistic limit models are all developed based upon spherical impacting particles, the experiment has pointed to a missing component in the current approach that must be considered. To begin to understand the implications of this observation, simulations have been performed using cylindrical structures at a representative orbital speed into an externally-insulated, double-wall shield that is representative of shielding on the current International Space Station crew transport vehicle, the Soyuz. These simulations have been performed for normal impacts to the surface with three different impact angles-of-attack to capture the effect on the shield performance. This paper documents the simulated shield and the models developed to study the effect of fragments and derives the critical characteristics of CFRP impacting particles for the selected shield. This work gives a deployable form of a critical, non-spherical projectile ballistic limit equation for evaluating non-spherical space debris for orbital debris environment modeling.