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X-Ray Energy Deposition Modeling for Nuclear Mitigation Missions

Presentation #303.07 in the session “Planetary Defense: Avenging the Dinosaurs”.

Published onOct 03, 2021
X-Ray Energy Deposition Modeling for Nuclear Mitigation Missions

In the event of an imminent Near-Earth Object (NEO) impact, a mitigation mission could be launched to divert the object’s orbit or destroy it entirely, provided sufficient warning time and depending on the size. Though a non-nuclear technology, such as a kinetic impactor, is the preferred mitigation strategy within the planetary defense community, a range of threat scenarios exist for which a nuclear device is the only approach capable of preventing an Earth impact. However, the details of asteroid response to a nuclear mitigation mission would depend on the NEO’s physical properties, such as size, shape, mass, composition, and structure. Especially if the warning time is limited, all of these properties may be poorly constrained before a mission is launched. The resolution requirements for a simulation of this system span many orders of magnitude and the required physics packages are complex. However, having an efficient and accurate way of modeling an NEO’s response to the radiation emitted by a nuclear device (mostly x rays) is necessary for exploring the various NEO properties and their resulting sensitivities. We present a two-part approach for simulating a NEO deflection/disruption via x-ray radiation. The first simulation component includes x rays penetrating into the NEO surface and depositing energy, which happens immediately after the device is detonated and before the heated material has time to move. For this process, we use the Kull multiphysics code, which is a fully-coupled radiation hydrodynamics simulation with Implicit Monte Carlo (IMC) transport to capture an angle-dependent time slice of the energy deposition. The deposition profile can then be used to initialize the second simulation component: a hydrodynamics model. For this process, we utilize the Adaptive SPH code, Spheral, which is well suited for modeling shock propagation and damage in asteroid-like materials. Spheral can be used to track the NEO’s response to the device’s x rays at long timescales while collecting information on the deflection velocity and any potential fragmentation. We will present an update on the latest x-ray ablation modeling methodology advances.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-824641


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