Germany’s unrestricted submarine campaign of 1917 was a major blow to the Royal Navy, and sonar, a technology that uses sound to detect the location and characteristics of enemies at sea, has played a major role in warfare and ocean exploration since World War I.
On February 1, 1917, Germany launched an unrestricted submarine campaign that changed the course of the First World War. During this operation, German submarines sank several merchant and warships, including three British armored cruisers, forcing the British into a corner. Germany was able to do this because the technology to detect objects underwater did not exist at the time. To overcome this disadvantage, the Royal Navy was forced to look for ways to defend against attacks, which led to the development of submarine detection technology. During World War I, scientists and engineers began researching ways to detect enemies under the sea. The result was a technology called sonar. This technology was so helpful in locating enemies hiding in the ocean that by World War II, it was mandatory for all warships and submarines.
When you’re deep underwater, there’s almost no light, making it absolutely impossible to detect enemies with the naked eye. On land, radar, which uses electromagnetic waves to detect enemies, can be used to detect enemies, but it cannot be used underwater because water reflects electromagnetic waves. To solve this problem, SONAR was invented to use sound instead of electromagnetic waves. Water is a very effective medium for transmitting sound, and the speed of sound in water reaches 1500 m/s, about four times faster than in air. Sonar is a technology that uses this to measure sound echoes and detect objects. Sonar stands for Sound Navigation and Ranging, and it is literally a device that detects objects by measuring distance and direction through sound.
There are two main types of sonar: active sonar and passive sonar. Active sonar shoots ultrasonic waves directly into the water to detect submarines or traps in the ocean. When these ultrasonic waves hit an object, they are reflected back to you, much like shouting from the top of a mountain and getting an echo back. Active sonar collects these reflected ultrasonic waves to detect objects in the ocean. Common examples of active sonar include acoustic sounders to measure depth, fish finders to detect schools of fish, and hull-mounted sonar to detect enemy vessels such as submarines.
The information you can get from active sonar isn’t just the location of an object. By analyzing the way ultrasonic waves bounce off objects and the time differences between them, you can get a precise picture of their size, shape, speed, and direction. For example, by firing multiple ultrasonic waves simultaneously and comparing the time it takes for each wave to bounce back from an object, you can measure not only the distance of an object, but also its motion and speed. You can also analyze the type and even the size of the object, as the ultrasonic waves bounce off the object in different ways. This makes active SONAR very useful for detecting and characterizing enemy vessels, such as submarines. However, active SONAR runs the risk of giving away its position to the enemy by directly emitting ultrasonic waves. It is not often used in real-world combat situations because enemy ships can track these ultrasonic waves back and determine the location of the ship using SONAR.
Passive sonar was developed to solve this problem. Unlike active sonar, passive sonar does not emit ultrasonic waves directly, but instead receives information by listening to sounds from the outside world. Just like listening to the inside of a person’s body with a stethoscope, passive sonar collects and analyzes the sounds in the ocean. In particular, it can detect the sound of engines, the churning of water, and the noise of propellers as a submarine or warship moves to determine the location and direction of an enemy. Passive sonar is excellent at detecting enemy ships, which is important for determining enemy ranges and military strategy. Typical passive sonar systems include acoustic surveillance systems installed on the seabed and array sonar systems used on warships.
In warfare, SONAR has become an indispensable tool, enabling the detection of enemy positions and movements and the planning of attacks. In particular, the development of SONAR has contributed to the strategic advantage in naval warfare. Even torpedoes were able to use SONAR to track enemy ships and target them for attack. Even today, SONAR is an indispensable technology for navies, and it continues to evolve. Sonar is not just used for military purposes, but also plays an important role in many other fields such as ocean exploration, underwater rescue operations, and environmental protection. As the eyes of the sea, sonar will continue to be an essential tool for naval tactics and marine research.
