Without explosion Laser disarms old ammunition under water

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What should you do if you come across some of the 1.6 million tons of munitions from the two world wars in the North and Baltic Seas? The Laser Zentrum Hannover (LZH) has an answer.

Ammunition has been corroding in the oceans for over 100 years. If they rust through, toxic substances enter the water and at the same time the risk of bombs and grenades going off can increase. In order to defuse the dangerous remnants of war, targeted blasting has been carried out to date, which is known as "high order" detonation. But you can imagine that this is not exactly good for the maritime environment. The LZH has therefore developed a laser-based process that can disarm non-transportable, detonated ammunition under water more gently, as part of the "UnLowDet" project, according to information from Hanover. Read now what the laser experts have done

Anchor, drill through and torch ...

The method developed at the LZH is based on a two-stage process in which notches are first made in the explosive ordnance casing using a laser. This leaves approximately one third of the wall thickness intact. In the second step, the laser shines through the remaining material, the beam hits the explosive and triggers what is known as deflagration. This is a very fast combustion, also known as "low-order" conversion, but nothing explodes. The overpressure created by the combustion gases finally breaks open the shell of the ammunition and prevents high-order detonation, which is why no more pressure or sound waves occur. This would significantly reduce the previous damage to the marine environment. And the whole thing has already been tested.

Disarming successes with various munitions

This took place in the blasting lake at the Wehrtechnische Dienststelle 71 in Elpersbüttel. The LZH and its project partner Laser on demand carried out the final tests there. The researchers successfully validated the laser-based method: they triggered a controlled "low order" conversion under water - the shell broke open and the majority of the explosive remained intact. The method was tested on explosive devices containing 200 grams of TNT (trinitrotoluene), found ammunition from the Second World War (provided by the Schleswig-Holstein Explosive Ordnance Disposal Service) and mortar shells from the German Armed Forces, according to the report. It was crucial for safety that there was never a dangerous transition from deflagration to detonation. The process enabled controlled "low order" detonations of various intensities, whereby the ammunition casings partially ruptured or broke open completely, according to the report.

Laser deflagration protects the environment

The measurements of noise emissions have also proven that the process benefits the environment. This is because, according to the researchers, it significantly reduces underwater noise. In follow-up projects, the scientists now want to further deepen their knowledge of the ignition behavior and the breaking open of the shell of explosive devices and also transfer the process to other explosive ordnance. The aim is to further optimise the process so that it can be used quickly. In the long term, the aim is to reduce the impact on the marine environment and eliminate the need for expensive technology such as bubble curtains, which otherwise dampen the sound but also drive away animals.

(The joint research project was funded by the Federal Ministry for Economic Affairs and Energy under the funding code 03SX550B by the project management organisation Jülich. The project partners would like to thank WTD71 for its support during the demonstration tests).