During 1990â2003, Pakistan sustained its historical lead as the second-most urbanized nation in South Asia with city dwellers making up 36% of its population. Furthermore, 50% of Pakistanis now reside in towns of 5,000 people or more.
Submarine Propulsion Systems. During World War II, most American submarines were powered by diesel-electric systems. This was a departure from earlier submarine power systems, which were direct drive types, little changed from the earliest boats. In this direct-drive power system, the diesel engine is directly connected to the propeller shaft.
The pictures to the right are of the same class of submarine (Ohio Class), and the second picture has two identical submarines, one on the pier and one in the water next to it. Types of Submarines - Fast Attacks (SSNs) There are 3 types of fast attack submarines in the U.S. Navy.