Micrometeoroid Impact Damage on Thin Ceramic Component for Interplanetary Probe

抄録

A new ceramic thruster for an interplanetary probe is currently under development. Monolithic silicon nitride (Si₃N₄) , which has good heat resistance and high fracture toughness among conventional structural ceramics, is a promising material for a high performance thruster. However ceramics are brittle compared to metallic materials. In order to evaluate reliability of the ceramic thruster as a space-use component, fracture behavior against micrometeoroid impacts was investigated. First the risk probability of the meteoroid impacts which may occur during a mission was estimated based on impact energy which may cause failure of the material. Second, damage of the silicon nitride ceramics by a possible micrometeoroid impact was investigated experimentally. Hypervelocity impact tests were carried out on the silicon nitride ceramic samples with a two-stage light-gas gun. Impacts at various velocities ranging from 1.0 km/s up to 4.5 km/s brought about three types of failure. However no shattering occurred by the hypervelocity impact with a possible energy. The experimental results together with the risk evaluation considering the flight mission conditions show that the Si₃N₄ ceramic thruster for the interplanetary probe would have no serious problems caused by a meteoroid impact during the flight mission even with local damage.