Low-velocity projectile impact on spacecraft

Various impact phenomena are encountered in space, among which debris impacts are of most concern. In terms of velocity range of the impacts, structural hazard at very large velocity of over a few km/s is much investigated. However, lower velocity impacts can also be encountered, with similar fatal effects to spacecraft. Examples are debris impacts in geostationary altitude and those onto rear side of spacecraft in low earth orbit. It should be pointed out that debris shield like Whipple bumper system is not effective at low velocities, and no other effective means are known to protect spacecraft from projectiles encounted at less than 1 km/s. A series of laboratory impact tests are conducted to find out characteristics of both structural damages and fragments created and released into space. The major items made clear are that characteristics of fragments are similar to those of hypervelocity impacts. Structural damage to honeycomb panels and mesh-type parabola dishes will be described as examples of debris impact in geostationary orbit. Another example to be investigated is impacts of rocks and steel projectile onto structure of sampling mechanism on a surface of an asteroid, a mission to fly in the year 2002.