German robots scour the seabed for WWII-era shells

A new generation of underwater robots is helping to find and defuse unexploded bombs that are still on the seabed. A pilot project supported by the German government will use the technique and other technologies in a Baltic Sea bay this summer to test a rapid, industrial-scale collection process. sunken ammunitionpolluting the seabed.

Where do the bombs come from?

Until sometime in the 1970s, a common method of disposing of unwanted ordnance was to simply dump it overboard. This meant that a variety of weapons, from grenades to chemical weapons, were languishing along Europe’s coastlines in large quantities, alongside other types of unexploded ordnance (UXO).

Experts estimate that more than 1.6 million tons of unexploded ordnance are littering the North and Baltic Seas. Remotely controlled bottom crawlers and robots with “smart grippers” are now collecting everything that people threw away decades ago.

The problem is that in every sea zone where there has been or is a war, ammunition remains in the sea. And when they are there for a long time, they begin to rust and release more and more carcinogenic and other toxic substances, traces of which have been found in fish and mussels. The longer the ammunition lies on the bottom, the more it rusts, and the concentration of harmful substances in the water increases. So now is the time to figure out what to do with these ammunition while you can try to catch them.

The problem of buried ordnance goes far beyond the ecology and safety of the seabed. Children and beachgoers have occasionally picked up pretty rocks that turn out to be explosives, or chunks of Baltic amber that turn out to be leached white phosphorus from incendiary bombs, capable of igniting when heated in a hand or trouser pocket. Hikers, divers, and fishing crews in Europe also continue to find old military ordnance.

Having collected and analysed scientific data on the disposed munitions, Germany decided it was time to try to remove them from the sea on a large scale. The long-term goal is to build an offshore platform where the munitions could be destroyed in a detonation chamber after being retrieved from the sea by a robot.

Faster and safer

Until recently, scientists were slow to work with sunken ordnance. They had to first survey potential hazardous areas for individual bombs and mines (and sometimes even actual munitions graveyards, where everything was lying around all mixed up), and then mark the area as dangerous or try to find a way to retrieve them from the seabed.

In order not to endanger human divers, robots were involved in this work: swimming and crawling. At the same time, unmanned devices are used for environmental monitoring. These devices are remotely controlled using a deep-sea cable connected to the vessel. Deep-sea tracked devices, rolling along the bottom, are equipped with many sensors and cameras, and are controlled remotely.

The fundamental difference of the new approach of the Germans is the use of improved technologies and the increase in the coverage of the cleared areas. Now the robots are not just engaged in the extraction of individual shells, but quickly clear the area of ​​the territory from a large number of densely lying simple and chemical ammunition.

The current method requires about 150 years of continuous work to extract all hazardous objects from the seabed. If the new project is successful, the period will be reduced to 30 years.

How robots survey the seabed

The underwater surveillance vehicles are equipped with several cameras to inspect the seabed. Experts, studying the recordings, can see and identify the discovered munitions.

The tracked vehicle will roll along the seabed and pick up small-caliber ordnance using small grapples. All grapples are equipped with cameras, allowing specialists on the vessel to examine the ordnance in real time.

“Smart grippers” located on the ship's deck will also be used. They are submerged in the water and gently or firmly grab the ammunition, depending on its condition. For example, a crumbling box filled with ammunition can be lifted using a cup-shaped grip. And a single mine – with a more conventional grip.

Once the munitions are recovered from the seabed, they are placed in underwater metal baskets, sorted into roughly one or two types per basket. The vessel will be manned in shifts and will operate 24 hours a day. The crew is simply required to identify the munitions and load them into the baskets.

Sorting the ammunition at the stage of retrieving it from the bottom is done for a reason. Later, they will be placed in a detonation chamber on a sea platform, where they will be burned. They will burn it, because it is considered a more environmentally friendly method of disposal. Mixing different types of ammunition was considered dangerous. So first, all the grenades will be sent to the furnace, for example, because mines and so on.

We will find out this fall whether scientists will be able to achieve the desired result.