CONTOUR Dust Shield Performance

Abstract

The Comet Nucleus Tour (CONTOUR) is one of NASA's Discovery series missions in which a single spacecraft will be launched in July 2002 to journey to the coma of comets Encke and Schwassmann-Wachmann-3 at velocities of 28.2 and 14 km/s, respectively. A multishock bumper dust shield with four ceramic fabric bumpers and a Kevlar-based rear wall, normally aligned to the dust velocity field vector, will provide the protection. Various configurations of the prototype shield were shot with surrogate nylon particles of various diameters at about 7 km/s to determine empirical ballistic limit equations. The performance is scaled to flyby velocities and comet dust particles using laws of momentum and kinetic energy and is related to the expected comets' dust fluence to determine flyby distances from the nuclei for a desired level of reliability. Empirical damage models to predict the size of the holes and mass loss of each layer are developed from measurements of the damage on the prototype targets. For small dust particles, a shield erosion model is assumed to only affect the first bumper. The damage and erosion models are incorporated into a Monte Carlo probabilistic simulation that predicts the shield damage and the probability of no penetration of the shield. This paper describes the methodology to evaluate the shield performance.