Speaker
Description
In the PDC25 scenario at initial assessment, the asteroid may impact nearly vertically over Cape Town or at increasingly shallow angles moving north over Africa and Europe. This presentation will compare the predictions for blast and thermal damage from coupled radiation-hydrocode simulations using the ALE3D hydrocode and the NERO thermal radiation transport code.
For height-of-burst blast damage models, the PDC25 scenario is in an interesting size range where different asteroid sizes within that range could cause similar worst-case blast damage depending on their airburst altitude. A more likely smaller asteroid if airbursting near its optimal height of burst can cause similar blast damage to a less likely larger object that hits the ground, below its higher optimal burst height. For evacuation planning and potential damage cost comparison, we will consider the 1 in 1000 risk level, close to a worst case scenario. For both steep and shallow entry scenarios we will examine both large ground impacts and smaller sizes bursting near optimal height.
For thermal radiation damage predictions, hydrocode simulations using the ALE3D hydrocode have been coupled with NASA’s radiation transport code NERO. Previous diffusive approximations of heat transfer are only valid for optically thick and opaque media. NERO calculates in full 3D the spectral line radiation transfer through optically variable materials and is scalable to large domains like these scenarios. This allows calculation of the heat transfer from the hot asteroid entry corridor and fireball after ground impact through cool transparent air to objects on the ground at large distances from the impact. This enables accurate prediction of heat loads on the ground and in particular wildfire ignition. It will also allow calculation of the effective luminous efficiencies, hopefully narrowing the currently wide range of estimates that dominates the uncertainty in estimates of thermal damage. In particular we will compare the luminous efficiencies of ground impacts and airbursts.