Model Investigations on Electric Discharges over Balloon-Borne Stratospheric VLF Antennas

Abstract

Long linear antennas for very low frequency radio transmissions, supported by aerostats, unanchored, and raised to high altitudes, present themselves as slow-moving, highly conductive disturbances in cloud layers, acquiring an electrical charge and being subjected to intense coronae. High electric field strength values around those objects increase the risk of lightning strikes, which could be disastrous to the mechanical structures of the balloon mission (both the antenna and the balloon) and the radio transmitter. This paper aims to investigate the inception of lightning strikes over two essential elements of such missions: a talc-covered latex (balloon material) and the model of the linear antenna, made of different materials. Based on the high-voltage experiments with the recorded electrical discharges, the properties, functions, and possible ameliorations of the talc cover are presented, as well as the basic characteristics of lightning forms around the very long antenna system, with a proposition of design requirements and constraints reflecting the safety of the balloon missions employing a VLF antenna from lightning strikes.