Generally speaking, there are three types of ASW platforms:
1. Airborne, which includes helicopters and planes.
2. Surface units such as frigates, destroyers and coastal submarine hunters (BN has a couple of these).
3. Submerged units like diesel-powered submarines and nuclear-powered ones. Nuclear-powered ones are more for strategic use. Many nuclear armed states store and hide their nuclear arsenal in those things. What's better than keeping them in a hard to find place and a mobile fortress and knowing you can pawn whatever asshole whenever you want to? Diesel-electric ones are more tactical, and swifter than nuclear ones.
Now, the most important and difficult thing about hunting down a submarine is detecting it. It requires a considerable amount of time and resources to do so. It can also be a risky one depending on the assets you use. But once it is detected, hitting and sinking it becomes easy.
Airborne ASW platforms are the most popular means for submarine hunting. Some submarines have MANPADS installed, but such methods are thought to be ineffective.
No, radar cannot be used to detect a submerged submarine. Available technologies are based around means through sound waves and magnetic deviations. Submarine designers have worked hard to make them ever more silent in response.
A submerged submarine is a "hard" target. It's swift, stand still, dive through different temperature layers of the water in order to hide, strike down any noise make, use the bottom of the sea to hide and find another target. Yes, it is an extremely potent weapon.
As mentioned before, ASW aircraft are the most popular means to submarine hunting. They include both helicopters and aircraft. The reason for their popularity is speed. This advantage also gives the aircraft a quicker response time than the submarine.
Helicopters are slower and have much lower endurance than aircraft. But their chief advantage is that they can complete the job in a more methodical fashion. They can also hover above an area (something that ASW aircraft cannot do). Additionally, they can be carried on board by small ships.
On sensors, ASW helicopters are typically equipped with Magnetic Anomaly Detectors (MADs), dipping sonar, and sonobuoys. The latter two can come in both active and passive modes. MADs can detect submarines in a limited area, whereas dipping sonar and sonobuoys can enable the crew to listen to underwater sounds for long periods of time.
MADs are typically used as a probe and towed behind the helicopter or aircraft. Submarines underwater do cause slight deviations in the Earth's magnetic fields. This is based on the fact that a submarine is basically a large mass of steel and alloys concentrated in a primarily water environment.
Such deviations can be detected with the use of MAD. But this method can be very problematic given the increasing number of shipwrecks under the sea. Technology can help solve this given that the information being displayed can present very precise maps of such deviations.
The key drawback of MAD is range. The aircraft or helicopter must fly very low and slow to use it over an area where a submarine is suspected. This method may also require prior intelligence.
Sonar on the other hand is based around sound. The sonar device is basically an advanced microphone which is supported by a variety of emitters and receivers. These can additionally be supported by computer hardware and software to make them more potent. They can be used in both active and passive modes. Active means that the sonar device sends out its own beam, and listens for echos. Passive means that it only receives sounds from the target.
Now, detecting sound underwater depends on four main factors: 1) Salinity, 2) Pollution, 3) temperature and 4) pressure (which increases with depth).
It is these factors that can affect sound waves underwater such as bending them, bouncing them back or even slow them down.
Typically, a sound wave can bounce back from any smooth surface. Be it from an enemy submarine or rocks. Rocks can send sound waves in several directions.
Differences in water temperatures can also affect sound waves. Also called "thermal-layers". Some parts of the oceans have thermal layers so big, that entire nuclear submarines can hide in them. These also bounce back any sounds from any kind of sonar device, or even completely block the sounds from ever reaching the passive sonar.
However, there are layers of the oceans that are perfectly capable of transporting sound waves. This particular layer of the water has a top layer that has too high temperature and hence bounces back the sound waves. The layer at the bottom has a pressure too high and bounces the sound waves as well. By this manner, sound waves will be bounced back from one water layer to another over long distances. This is how whales communicate and travel over long distances. These layers typically lie from a depth of 800-2000 meters, but this ultimately depends on temperature and pressure (the two most key factors in submarine detection).
So how do they go about sound waves? It is measure by "gain" strength of the emission and frequency.
Simple rule of thumb: The higher the frequency, the closer the target. This enables the frequency easier to concentrate and hence a more accurate position fixation on the target.
For low frequencies, it's the opposite. Submerged targets are mostly identified through low frequency means. Meaning that the crew would get an approximate position of the target, not a very accurate one.
But "gain" is very important. Too much gain is never good since it can give off double targets as a result of bouncing back too strongly due to the signal going back down and up again. This may also give irrelevant targets such as fish, rocks and stupid people swimming.
Aircraft are much faster than helicopters. And have superior range and endurance. Unfortunately, their speed does not allow them to use a dipping sonar. When it comes to detection, it is limited to sonobouys and MADs. All ASW aircraft must take off from land unlike helicopters, except the E-3 Viking which is not longer used in ASW operations.
In terms of armament, ASW helicopter can carry guided torpedoes and dept charges. Some can carry light anti-ship missiles. ASW aircraft can carry a much higher payload of munitions and sonobuoys.
So what do all these imply for BN or even Myanmar Navy? It'd require one to know their environment and the assets they are operating very well. Now that is a lot of homework. Submarine hunting is a very complex operation where timing is everything. On one hand, the threat posed by a submarine cannot be ignored.
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