Submarine

**Submarine** is a type of sea-going vessel that is capable of surface and underwater travel. It is considered a potential weapon against surface ships and other ocean targets.

## Overview

The main differences between a submarine and a normal surface ship are the facts that a submarine can control its buoyancy and is designed to operate underwater for extended periods of time. The hull of a submarine is composed of two sections; the pressure hull and the outer hull. The pressure hull contains the engines, crew quarters, weapons, control systems, communication systems and control centers. The outer hull is normally coated in sound suppression material to avoid sonar detection. The space between the two hulls are the ballast tanks, which allow the craft to control its buoyancy and either sink or rise.

The top of the sub is where the main command center is located. This is the conning tower or sail bridge. Near the rear are a pair of hydroplanes to see the ship as well as the impeller blades for propulsion. Some submarines have additional hydroplanes for added maneuverability.

## How a Submarine Functions

With the exception of nuclear submarines, most are equipped with two engines. The first is an air-breathing engine, normally a diesel engine, that is used when the submarine is traveling on the surface. The second is an electric motor when submerged. When a submarine dives, the ballast tanks fill with water in order to lower the vessel's buoyancy. When the ship wants to surface, the water is pumped out of the tanks.

The ship's submersion time depends on the technology.

Due to the crushing weight of deep-sea travel, a submarine cannot rise too quickly to the surface. The sudden change in pressure will put stress on the ship as well as the crew, causing them to suffer decompression sickness or the bends. Furthermore, a sudden rise to the surface will be detected on sonar.

When the submarine was first developed, the only way to see where one was going while submerged was either to surface or look through a periscope. However, this can give away the submarine's position and can result in getting sunk. Modern submarines now rely on inertial guidance systems, active sonar, and GPS.

## Weapons

During World War I and II, submarines were built more like surface ships and were armed with deck guns to sink other vessels. Of course, these were meant to be used against unarmed merchant vessels and were no match against an armed cruiser or battleship. Modern submarines now rely on torpedoes, mines and sub-launched missiles like the Harpoon Missile.

## Anti-Submarine Tactics

Normally, to defend against the submarine, surface ships deploy passive and active sonar systems to detect them. Patrol planes and helicopters also use these methods to detect them. Once located, the ship or plane has the option of firing torpedoes or depth charges to sink the submarine.

Submarines must also be equipped for the possibility of engaging enemy submarines. Normally, the first to spot the other would have the advantage. Therefore submarines are normally using active sonar.

To counter Anti-Submarine Tactics, the crew must be trained to 'running silent' as a slight sound can give away their position by sonar.

## Known Users

### Japan

Japanese submarines include the Soryu-class and the Oyashio-class. There are plans on making 5 nuclear-powered submarines in the near future. All of them are capable of launching torpedoes, anti-ship missiles, cruise missiles, and sea-mines. Additionally, with sound-suppression technology, the crews of the submarines were also trained to conduct 'running silent' tactics while diving to ensure their positions are not detected by the sonar.

Additionally, Soryu-class uses AIP (Air Independent Propulsion), which allows the submarine to stay submerged for weeks.

### Gra Valkas Empire

The workhorse of the Gra Valkas Empire is the Cetus-class, which is equipped with 3 scout planes, unguided torpedoes, and an escape pod. However, they do not possess stealth capabilities as the sound of their submarines already expose their location far before they know it. Additionally, the crews are not trained to conduct 'running silent' tactics to prevent anti-submarine warfare.

The Gra Valkas did not have any Air Independent Propulsion technology, which limits their submerging time.

## Awareness in the New world

### Third and Outside Civilization

The existence of submarines are absolutely unknown to the New Worlders with the exception of the Riem Kingdom, which their officials have discovered in the bookstores magazines during their visit to Japan. In the aftermath of the Japanese-Parpaldian war, King Bank were briefed by his prime minister that they do not have any countermeasures against submarines attack which caused him to be fearful.

### Second Civilization

Like the 3rd and outside civilization, it is also unknown to them while only aware by Mu through their observers. Apparently despite having the capabilities to build battleships, the concept and notions of submarines are an alien concept to them. Myrus even stated that Mu does not have the capabilities to build even one submarine even if they devote all their technological resources.