There is a need for environmentally-acceptable remediation techniques for underwater ordnance disposal where unexploded ordnance (UXO) cannot be moved to the surface and rendered safe. The current protocol calls for a blow-in-place (BIP) procedure where an explosive charge is utilized to detonate the UXO in place. During a typical BIP procedure, the resulting shockwave and bubble formation/collapse from the detonation of the UXO produces pressures and acoustic noise that is detrimental to marine life. Explosively generated plasma (EGP) technology provides a method to neutralize UXO with minimal environmental impact (no detonation) while using a minimal explosive donor charge.
EGPs are created by the focusing of a shock produced from an explosive driver via a conical waveguide. In the waveguide, the gases from the explosive along with the trapped air are accelerated and compressed (by Mach stemming) to such extent that plasma is produced. These EGPs have been measured in controlled experiments to travel at velocities as high as 21,000 km/s with temperatures of 20,000 K. Naval Surface Warfare Center Indian Head Division can be used to perforate the casing of the Naval 5” round and neutralize the explosive fill by initiating a low order or deflagratory process. The EGP couples with the high-explosive fill resulting in a high temperature chemical decomposition along non‑traditional kinetic pathways that results in rapid deflagration without detonation. The introduction of an EGP-based technology with a sealed waveguide for the remediation of underwater UXOs provides an innovative alternative to existing BIP operations with far less environmental impact. This technology provides the potential for rapid and near-complete consumption of the energetic fill without the associated shock and bubble formation/collapse from a detonating UXO.
In this effort, it was demonstrated that the designed EGP tool can perforate the steel cased Naval 5” round both on land and underwater. The tool initiates a slow burn of the explosive fill on land, resulting a burn completion time of between 10 and 20 minutes. Underwater, the reaction is quenched by inrushing water. A low-order solution was found that remediates underwater UXO. While this solution breaks the casing into several pieces, the solution does not detonate the munition. Cost of the parts for the designed solution is estimated under $500.00 and is constructed from machined acrylonitrile, butadiene and styrene plastic which minimizes fragmentation hazards.
Early designs under this effort used three-dimensional printed parts. It was found that these parts did not have the proper tolerancing to keep water from penetrating the inside of the device, which caused the devices to fail. This problem was solved by switching to a machined plastic solution.
McCarthy D., Giannuzzi P., Schweigert I., Elert M., Gosney G., Emery S., “Interaction of Explosives with Explosively Generated Plasma”, 16th International Detonation Symposium.