Early German torpedoes, or eel (Aal=eel) as it was popularly known were a combination of two worlds. They were both technologically sophisticated, and yet unreliable. During the First World War, standard U-boat torpedoes were driven by an alcohol fueled engine which possessed good characteristics of speed and range. The contact detonators used on these torpedoes were also of simple design, making them mechanically reliable. 

 

All the U-boat commander had to do was to calculate the right torpedo firing solution, and if he fired it right, then he could count on it that the eel would run true to its course.

However, two main drawbacks existed from the World War One torpedoes. First, the alcohol fuel engine left a telltale trail of bubbles on its way to its target. This could alert a watchful lookout and give the enemy time to perform evasive maneuvers. Second, the contact detonator, although mechanically reliable, was designed for the torpedo to explode on impact with the side of the ship. Often it would take more than one torpedo to sink its target, and if the opportunity did not present itself, then the ship often managed to limp back to port.

http://www.uboataces.com/images/torpedo_trail.jpg" alt="Torpedo wake" border="1" height="156" width="350" />	http://www.uboataces.com/images/torpedo_service.jpg" alt="Torpedo being serviced" border="1" height="156" width="211" />
The torpedo wake not only left a telltale sign of the attack, but also gave away the position of the attacking U-boat.	World War 2 torpedoes were quite fickle. They had to be pulled from their tubes and serviced every two or three days.

Between the wars, German scientists worked to improve their torpedoes, so that it would not leave a visible trail of bubbles and where it would take just one torpedo to sink a ship. The solution was a highly classified and sophisticated torpedo ? the wakeless electrically powered G7e torpedo, armed with a completely new magnetic detonator. Even the Allies had no knowledge that the Germans had successfully developed a wakeless electrically powered torpedo until remnants of it were found at the wreck site of HMS Royal Oak, sunk in the daring attack of Scapa Flow. The new battery powered motor meant that no exhaust gases were expelled, and the magnetic detonator was designed to travel under the keel of a ship and then detonate. Such underbelly explosions could break a ship?s hull in two, sinking it with just one torpedo. Not only the propulsion system and firing mechanisms were new, in fact almost every part of the G7e torpedo was redesigned.

When war broke out in September 1939, Germany was poised to strike at the western powers with new weapons and technologies. For the U-boat Force, it was their new submarines and the newly developed torpedoes. Although it sounded promising, but when the U-boats began the offensive, the results of the new torpedo was disappointing. Many commanders began to relate accounts of torpedo failures.

In fact, one of the earliest torpedo failures took place on September 14 during an encounter with the Ark Royal. Gerhard Glattes of the U-39 chanced upon the most formidable and modern aircraft carrier of the Royal Navy, sailing alone and into the crosshairs of his periscope. She had turned into the wind to launch aircraft and as a result, had fallen four miles astern of her destroyers. Glattes fired a fan of three torpedoes at the carrier. All three detonated prematurely. Now alerted of the presence of a U-boat, her destroyers rushed to the scene and depth charged and sank U-39 through a series of coordinated attacks. The U-39 w