Aerospace Colloquium

For a meteoroid undergoing break-up within the atmosphere, the high-speed aerodynamic interactions between fragments immediately following disruption play a critical role in determining the risks posed at the terrestrial surface. In this seminar, I will first describe experimental, computational, and theoretical studies of the interactions between two isolated bodies as a basis for understanding the more general separation problem, highlighting the importance of "shock surfing", where one body rides the shock of the other body downstream. I will then describe recent experiments in a hypersonic wind tunnel to determine the separation characteristics of an idealized fragmented meteoroid, consisting of an initially spherical cluster of up to 115 close-packed spherical bodies. For equal-sized fragments, the mean separation velocity follows a power law as a function of population with an exponent of ~0.4, while individual velocities are well-modeled by a single-parameter Rayleigh distribution. In unequal clusters, mass retention in sub-clusters decreases the mean separation velocity, but individual velocities again follow approximate Rayleigh distributions (with the governing parameter now radius-dependent). An examination of the most ejected bodies in the dataset also reveals that shock surfing can produce significant outliers and potentially explain a substantial portion of the discrepancy between airburst observations and previous predictions.