ROCKET-TRIGGERED LIGHTNING STUDIES FOR THE PROTECTION OF CRITICAL ASSETS

Lightning protection systems (LPS's) for explosives handling and storage facilities have long been designed similarly to those used for more conventional facilities, but their overall effectiveness in controlling interior electromagnetic (EM) environments has still not been rigorously assessed. Frequent lightning-caused failures of a security system installed in earth-covered explosives storage structures prompted the U.S. Army and Sandia National Laboratories to conduct a program to determine quantitatively the EM environments inside an explosives storage structure that is struck by lightning. These environments were measured directly during rocket-triggered lightning (RTL) tests in the summer of 1991 and were computed using linear finite-difference, time-domain (FDTD) EM solvers. The experimental and computational results were first compared in order to validate the code and were then used to construct bounds for interior environments corresponding to severe incident lightning flashes. The code results were also used to develop simple circuit models for the EM field behavior-a process that resulted in a very simple and somewhat surprising physical interpretation of the structure's response that has significant practical and economic implications for design, construction, and maintenance of such facilities.