How Submarines Work

Lightdoes not penetrate very far into the ocean, so submarines must navigate through the water virtually blind. However, submarines are equipped with navigational charts and sophisticated navigational equipment. When on the surface, a sophisticatedglobal positioning system(GPS) accurately determines latitude and longitude, but this system cannot work when the submarine is submerged. Underwater, the submarine usesinertial guidance systems(electric, mechanical) that keep track of the ship's motion from a fixed starting point by usinggyroscopes. The inertial guidance systems are accurate to 150 hours of operation and must be realigned by other surface-dependent navigational systems (全球定位系统(GPS),radio,radar,satellite). With these systems onboard, a submarine can be accurately navigated and be within a hundred feet of its intended course.

To locate a target, a submarine uses active and passiveSONAR(soundnavigationandranging).Active sonaremits pulses of sound waves that travel through the water, reflect off the target and return to the ship. By knowing the speed of sound in water and the time for the sound wave to travel to the target and back, the computers can quickly calculate distance between the submarine and the target. Whales, dolphins and bats use the same technique for locating prey (echolocation).Passive sonarinvolves listening to sounds generated by the target. Sonar systems can also be used to realign inertial navigation systems by identifying known ocean floor features .