Contour dust shield performance

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 t he coma of comets Encke and Schwassmann-Wachmann-3 at velocities of 28.2 an d 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 v elocity field vector, will provide the protection. Various configurations o f 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 usi ng laws of momentum and kinetic energy and is related to the expected comet s' dust fluence to determine flyby distances from the nuclei for a desired level of reliability. Empirical damage models to predict the size of the ho les and mass loss of each layer are developed from measurements of the dama ge on the prototype targets. For small dust particles, a shield erosion mod el is assumed to only affect the first bumper. The damage and erosion model s are incorporated into a Monte Carlo probabilistic simulation that predict s the shield damage and the probability of no penetration of the shield. Th is paper describes the methodology to evaluate the shield performance.