The Research On Characteristics Of Shield Structure Under Light Brittle Projectile Hypervelocity Impact

The spacecraft encounter threats from hypervelocity impact of space debris and micrometeoroid while moving in obit, and micrometeoroid is the only threat for deep space probe especially. In contrast to space debris, micrometeoroid has several features, such as complex component, high speed and low average density. Damage characteristics of spacecraft shield structure under micrometeoroid hypervelocity impact are not clear. It becomes necessary to study the damage characteristics of spacecraft shield structure under micrometeoroid impact, in order to improve shield structure design, enhance the ability against micrometeoroid impact. According to the feature of low average density of micrometeoroid, two kinds of low density and brittle material, polypropylene and ice, are chosen to be the imitation material of micrometeoroid.First of all, launch technology of brittle and low melting point material is studied. In the range of 1km/s to 3km/s, brittle projectile is launched successful by adopting bumper, cavity and aluminum diaphragm; liquid nitrogen dewar cooling system is confirmed useful to resolve the problem that ice projectile melts.Then, experiment and numerical simulation of polypropylene projectile hypervelocity impacting spacecraft shield structure are conducted. Tear is found when the projectile velocity is lower than 1.5km/s in experiment study; numerical simulation is confirmed validity by comparison between experiment and simulation results, and is used to extend the range of study. Found in simulation study, bumper hole diameter, the largest velocity of debris cloud and scattered radius of crater increase with increasing of projectile velocity and diameter; ballistic limit curve and empirical formula are fitted for polypropylene projectile hypervelocity impact whipple shield structure; the damage caused by polypropylene projectile is smaller in contrast with aluminum projectile with same velocity and diameter.At last, the damage characteristics of shield structure under ice cylinder impact are studied, the critical velocity, empirical formula of height and thickness of bulge are acquired by experiment and numerical simulation. The damage characteristics of Whipple shield structure under ice projectile hypervelocity impact are studied by numerical simulation, Bumper hole diameter, the largest velocity and scattered radius of crater are found increase with the increase of projectile velocity and diameter; ballistic limit curve and empirical formula of aluminum projectile are fitted; in contrast to aluminum ballistic limit curve, damage caused by ice projectile impact is more serious than aluminum projectile when velocity of projectile is over 6km/s.In this paper, preliminary study of damage characteristics of shield structure under two kinds of typical light projectile hypervelocity impact are conducted, the data and rule of damage acquired in this study may have some reference value on shield structure optimum design.