German Magnetic Mine

[Gildwiller1918]

In WW2 the Germans used magnetic naval mines to inflict damage on the Royal Navy and more importantly cripple the life blood of raw materials flowing to England. These mines used the Earth's magnetic field as the trigger, when a ship passed within 10 meters of the mine, it caused a disturbance in the magnetic field, tripping the mine. At first the English were quite confused at what was causing the damage, then a magnetic mine was found in the Thames Estuary mudflats in November of 1939. The British quickly studied the device and came up with countermeasures, such as degaussing which ships used coils to reduce the electromagnetic signature of the vessel to avoid tripping the mines, however this was expensive and time consuming. Another method called wiping or deperming used long electrical cables with 200 amps to hide the vessels signature, this worked for awhile, until the Germans upgraded their mines with better fuses and detection equipment. Typically these mines were dropped by aircraft or laid by submarines or other vessels. 

The Germans got the mine warfare lead again later in 1940 when they introduced acoustic mines. However, Admiral Raeder employed them before they were available in large numbers. The British recovered one in August 1940, and one month later put a mechanical acoustic sweep into service that could defeat the German acoustic mine. Unfortunately, sound dampening the equipment on British ships proved too expensive to implement during the war, although they did do it in minesweeping units. The Germans countered by producing a combined acoustic/magnetic mine, but the British soon developed minesweeping tactics to counter it as well.

The Allies were not idle in mine development, Great Britain developed magnetic mines in World War I and employed them again beginning in April 1940. The Germans countered by developing their own magnetic influence sweeps. They also built a specific class of magnetic sweep ships, called Sperrbrecher. Equipped with huge electric coils in their bows to project a strong magnetic field ahead of them, these specially reinforced ships had shock-mounted equipment and other damage reducing features to survive mine detonations. The Germans used these units to lead coastal convoys through suspected and likely enemy minefields. They became increasingly important in the war’s final two years, as the Western Allies, in particular, laid more and larger minefields.

By 1943, the Germans employed 60% of their naval strength to combat mines, while the allies used over 1,100 ships for the same purpose. 

Both the Germans and Western Allies had combined acoustic/magnetic mines with ship counters and variable arming delays in service by late 1943, when the Germans introduced their latest technical innovation, the bottom pressure or “oyster” mine. These mines were detonated by the pressure wave a ship generated as it moved through the water. No minesweeper could simulate that wave since each pressure wave was unique to the size and speed of a ship.

Determined not to repeat Raeder’s mistakes from earlier in the war, Grand Admiral Karl Dönitz waited until the Allied Normandy landings to employ oyster mines. By then, however, he lacked the means to lay the mines in the invasion area. Only a handful could be deployed. Had they been laid in the invasion fleet’s assembly areas, they would have had a devastating effect. As it was, after some nasty surprises, the Allies easily avoided the few areas where these mines were laid. A few were recovered and the technology incorporated into Allied mines used against the Germans in the war’s closing months.

Aircraft were employed to help detonate mines as well. The first photo shows a Vickers Wellington with the ring around the plane, this was used to detonate the mines, however the plane had to fly very low to the water to do so, which may also result in its own destruction. The second picture shows a German version, the Blohm & Voss BV 138, third picture is the JU-52. Last photo is the German Mark I Magnetic Mine ('Type GA').

 

 

 

 

[Fritz]

Junkers 52 "Mausi"