German U-Boat Sea Mines - TMA, TMB, SMC

Mines were detonated by a passing ship either through contact, magnetic or acoustic signatures. German mines were of two basic types, the torpedo launched TM mines (Torpedomine) and the shaft launched SM mines (Schachtmine). The TM mines were launched from the standard 21 inch torpedo tube, making every attack boat a potential minelayer. Since they displaced mines, thus the torpedo capacity was reduced. The limited mines also meant that any minefield laid was very small. The SM mines were specialized mines designed for maximum effectiveness, and could be laid only by minelayers. They were launched from vertical mineshafts mounted at the foredeck. The minelayer carried many more mines and could lay a more dense pattern of minefield, but carried only a small number of torpedoes.

TMA

The TMA was a moored mine, which meant that it was secured by a heavy anchor and a cable attached to the mine. The mine floated above the surface, while the anchor secured its position in the sea. Two could be carried in each torpedo tube.

Length/Diameter: 11.1ft (3.38m)/21in (533mm)
Maximum Depth: 270m
Warhead: 215kg

TMB

The TMB was a ground mine, which meant it settled at the bottom of the seabed. It was detonated by the magnetic or acoustic signature of a passing ship. For maximum effectiveness, it could be laid only in shallow waters of up to 20 meters. Three could be carried in each torpedo tube.

Length/Diameter: 7.6ft (2.3m)/21in (533mm)
Maximum Depth: 20m
Warhead: 580kg

TMC

As with the TMB, the TMC is a ground mine, but with almost double the warhead. Due to the increased length, two could be carried in each torpedo tube.

Length/Diameter: 11.2ft (3.39m)/21in (533mm)
Maximum Depth: 20m
Warhead: 1000kg

SMA

The SMA is a moored mine, similar to its counterpart the TMA, but with a much larger explosive charge. It could be laid only by specialized minelayers with vertical shafts attached.

Length/Diameter: 7.1ft (2.15m)/4.4ft (1.33m)
Maximum Depth: 250m
Warhead: 350kg

EMS

The EMS could be fired from the standard torpedo tube and was a drifting mine. It floated on the surface and exploded on contact with a ship’s hull. It was armed 10 minutes after launching and was designed to stay afloat for 72 hours, after which it sank itself automatically.

EMS = Einheitsmine Sehrohr – Treidmine (Standard Drifting Mine)
Warhead: 14kg

MTA

The MTA was a ground mine developed to replace the TMB. It utilized the concept of a torpedo driven mine, in which the mine was carried by a torpedo to a certain pre-set distance. Once the distance had been reached, the torpedo switched off and sank to the bottom, acting as a ground mine. The distance could be programmed in 200 meter increments, up to a maximum of 7,000 meters. As with the TMB, it could be laid only in shallow waters up to 20 meters deep.

MTA = Minetorpedo A