Determining Detection and Classification Potential of Munitions Using Advanced EMI Sensors in the Underwater Environment

Electromagnetic induction could be used to locate and characterize potentially dangerous sunken metallic objects.

Strategic Environmental Research and Development Program, Alexandria, Virginia

Hazardous ordnance items are present along coastlines and in rivers and lakes in waters shallow enough to cause concerns for human recreational and industrial activities. The presence of water makes it difficult to detect and remove these hazardous legacies induced from wars, military training and deliberate disposal. Various techniques have been proposed to detect and characterize Unexploded Ordnances (UXO) and discarded military munitions (DMM) in the underwater environment including acoustic waves, magnetometery, and electromagnetic induction (EMI).

In recent years, terrestrial munitions response has seen significant improvements in our capability to discriminate Munitions and Explosives of Concern (MEC) from benign metallic clutter. These advances have been primarily driven by the development of next-generation EMI sensors designed to interrogate small, near-surface targets. This research concerns underwater sensing using EMI which is distinct from the terrestrial setting in several respects including positioning requirements and techniques, noise environment, and practical constraints on deployment of sensor systems. In terrestrial settings, conduction currents can be ignored in most soil types (conductivity 0.01 S/m). The measured magnetic fields from a subsurface metallic object in the low-frequency EMI regime can be modelled as if the object were in free-space. In contrast, marine environments are generally highly conductive with an average seawater conductivity of around 4 - 5 S/m.