Hypervelocity Impact Simulation

Space debris--items ranging from pieces of old spacecraft to the much more common rain of small meteors (rocks, pebbles, and dust)--is the enemy of working spacecraft like the International Space Station, the Space Shuttles, and orbiting observatories of all kinds. An encounter with space debris is generally a very high velocity impact, and even a tiny pebble can cause enormous damage when it hits an orbiting spacecraft at velocities of tens of kilometers per second. The problem is increasingly important as space missions of longer and longer duration are launched. While shuttle missions may last one or two weeks, some orbiting weather satellites have lifetimes longer than a decade, which greatly increase the chances of impact. In both cases, the design of adequate shielding to resist any impact rests on careful analysis of all possible impact scenarios.

Such analysis is the specialty of the laboratory of Professor Fahrenthold. While some experimental facilities permit testing of impacts that might be experienced at the lower end of the velocity range, computer simulation is required to extrapolate such results to the higher velocities that are possible for debris-spacecraft encounters. Fahrenthold's computational approaches include "hybrid" codes, in which both finite-element and particle representations of the material domain are used. In a hypervelocity impact, the material integrity of a debris shield may be breached and the material may melt or be ablated. The ability of Fahrenthold's codes to follow the entire process and switch from elements to particles has made his analyses particularly useful in the space science community.

For a detailed description of calculations Fahrenthold made as part of an examination of the fate of the shuttle Columbia, see "Understanding Impacts: One Researcher's Story."