Silent running (submarine)

Jog is an operating state of submerged military submarines. The aim is to reduce the likelihood of detection by acoustic detection by the enemy (passive sonar ). During the slow speed all the unnecessary noises are avoided on board. Installations whose operation is not absolutely necessary, are turned off. The crew is stopped to rest. The travel speed is sharply reduced in order to minimize the propeller noise.

The propellers have a characteristic velocity / speed band in which anströmungsbedingt incur no cavitation. Since the rotation speed is relatively low, as a rule, the first electric submarines special slow speed engines, which had at correspondingly reduced set speed a better efficiency, needed less active cooling and bearings (no " ball bearing Crackle " possessed, but very much lower shelf were equipped at too low speed). These engines were also decoupled by their acoustic suspension from the body, which of course also included their Transmission: V-belt or timing belt transferred the engine power to the propeller shaft.

In modern nuclear submarines such as those of the Ohio class, the pumps, the reactor cooling system can be turned off at slow speed to drive even quieter. The reactor is then cooled only by natural convection of the water. However, this is only possible at very low speeds.