SOCIT4 collisional-breakup test data analysis: With shape and materials characterization

Abstract

In this paper we revisit the 1995 Kaman database of the SOCIT4 fragment characteristics with added analysis of a subset of the cataloged fragments from the test. This database was compiled from the last of a series of four hypervelocity impact tests conducted under a U.S. Department of Defense program in 1991–1992. This test targeted a flight-ready, U.S. Transit navigation satellite, yielding collision fragments in the size regime of sub-millimeter through tens of centimeters. Results in this database were used in the 1998 NASA Standard Breakup Model to represent characteristic length (size) and area-to-mass distributions of fragments smaller than 10 cm. In this analysis we explore, in detail, the tabulated fragment material and shape. What emerges is a clear distinction in fragment area-to-mass ratio between primarily metal and primarily non-metal fragments. Metal fragments, which are dominated by aluminum, follow the characteristic curve of increasing area-to-mass ratio with decreasing characteristic length: objects move from the character of large irregular bent shards to that of small solid spheroids. Non-metal fragments, dominated by phenolic/plastic, do not appear to move towards solid spheroids as easily as metals. Also unlike the metals, their area-to-mass ratio curve plateaus in the midsize region (smaller than 1 cm), coinciding with a peak in plate-like, non-metal fragments. The internal structure of the Transit payload, with its phenolic surface skin and packed arrays of plastic circuit boards, certainly governs this plateau behavior. In the small fragment regime (smaller than 4 mm) phenolic/plastic ellipsoidal ‘Nuggets’ dominate the population. They outnumber aluminum ‘Nuggets’ by over four to one. Through this study we gain a more detailed understanding of the collisional-breakup process of this particular payload, but also have begun to determine how these data may apply to other breakups. Our long-term goal is to apply this new understanding to future upgrades of the NASA Standard Breakup Model.