Numerical investigation on the standard catastrophic breakup criteria

Hypervelocity collisions are predicted to be the dominant space debris source in the mid-term future, when a critical spatial density of satellites is reached. The NASA Standard Satellite Breakup Model (SSBM) has been adopted by major space agencies for characterizing hypervelocity spacecraft breakups for debris environment modeling. The SSBM is an empirical model based on data from ground tests and observations of on-orbit events. We propose to enhance this database by numerical simulations including a wide range of collision conditions and complex spacecraft models. We established the software tool PHILOS-SOPHIA for systematically studying the effects of on-orbit hypervelocity collisions. A particular focus was laid on the breakup criteria of the SSBM, which defines an energy-to-mass-ratio of 40 J/g being the collision condition for catastrophic fragmentations. We simulated six different scenarios of a complex spacecraft colliding with a small satellite. In the detailed fragmentation analysis, we find both good agreements and clear deviations between the hydrocode results and the SSBM predictions. Particularly, the collision geometry strongly influences the fragmentation damage and the area-to-mass distributions. Depending on the collision vector, impacts on the outer parts of a spacecraft may result in both higher and lower fragmentation in comparison with impacts on the center of mass. The simple breakup criteria does not reflect this complexity and we recommend performing more research. Numerical simulations, thoroughly backed by advanced experiments, can make a significant contribution to improve the accuracy of breakup models.