Acoustic source calculations for nuclear bursts

Abstract

Research has been conducted on the source term for long-range underwater propagation of signals from nuclear explosions in and above the ocean, in support of CTB monitoring objectives. A suite of source-region simulations is reviewed to study the variation of wave properties and source-region energy partition as a function of height or depth of burst. The multistep calculation combines LLNL’s CALE hydrodynamics code in the strong shock region with NRL’s weak shock code, NPE, at intermediate ranges. The source term calculations are intended as a starter field for long-range linear propagation models to obtain signature estimates at normal observational ranges. Calculations are presented to examine the effect of sea ice below an air burst on acoustic coupling into the water column. The ice was modeled as a continuous elastic layer 5-m thick at the water surface, and the source as a 1-Kt explosion 50 m above the ice. Calculations with and without the ice layer predict a moderate, but noticeable reduction in coupled acoustic energy in signals observed at the 10<th>000-m range. [Work performed under the auspices of the U. S. Department of Energy by the Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48.]