Elektroboot

An elektroboot ("electric boat" in German) was a submarine designed to operate entirely submerged, rather than as submersibles that could submerge as a temporary means to escape detection or launch an attack. Even before the Second World War the rocket designer Hellmuth Walter had been advocating the use of hydrogen peroxide (known as perhydrol) as a fuel. His engines were to become famous for their use in rocket-powered aircraft—notably the Me 163 Komet—but most of his early efforts were spent on systems for submarine propulsion. In these cases the hydrogen peroxide was reduced chemically and the resulting gases used to spin a turbine at about 20,000 rpm, which was then geared to a propeller. This allowed the submarine to run underwater at all times, as there was no need for air to run the engines. The system also used up tremendous amounts of fuel, and any boat based on the design would either have to be huge or have limited range. Thus the system saw only limited development even though a prototype was running in 1940. But when problems with the existing U-boat designs became evident in 1942, the work was stepped up. Eventually two engineers identified a solution to the problem. Instead of running the submarine entirely on the perhydrol, they used it just for bursts of speed. Most of the operations would then be carried out as with a normal boat, using a diesel engine to charge batteries. However while a conventional design would use the diesel as the primary engine and the batteries for short periods of underwater power, in this case the boat would run almost all the time on batteries in a low-speed cruise, turning on the perhydrol during attacks. The diesel was now dedicated entirely to charging the batteries, which it needed only three hours to do. The perhydrol design suffered from several design flaws which were not fixed before the end of the war. As an intermediate solution, the perhydrol propulsion system was dropped in favour of a conventional diesel/electric solution, but retaining the streamlined hull-shape.