NASA's new breakup model of evolve 4.0

Abstract

Analyses of the fragmentation (due to explosions and collisions) of spacecraft and rocket bodies in low Earth orbit (LEO) have been performed this year at NASA/JSC. The overall goals of this study have been to achieve a better understanding of the results of fragmentations on the orbital debris environment and then to implement this understanding into the breakup model of EVOLVE 4.0. The previous breakup model implemented in EVOLVE 3.0 and other long-term orbital debris environment models was known to be inadequate in two major areas. First, it treated all fragmentational debris as spheres of a density which varied as a function of fragment diameter, where diameter was directly related to mass. Second, it underestimated the generation of fragments smaller than 10-cm in the majority of explosions. Without reliable data from both ground tests and on-orbit breakups, these inadequacies were unavoidable. Recent years, however, have brought additional data and related analyses: results of three ground tests, better on-orbit size and mass estimation techniques, more regular orbital tracking and reporting, additional radar resources dedicated to the observation of small objects, and simply a longer time period with which to observe the debris and their decay. Together these studies and data are applied to the reanalysis of the breakup model. In this paper we compare the new breakup model to the old breakup model in detail, including the size distributions for explosions and collisions, the area-to-mass and impact velocity assignments and distributions, and the delta-velocity distributions. These comparisons demonstrate a significantly better understanding of the fragmentation process as compared to previous versions of EVOLVE.