Example – In *The Hunt For Red October*, Petty Officer Jones can tell where submarines are and what they’re doing just be listening to sonar. So how do submariners do this, especially since there aren’t any viewscreens or windows on the boat? Like how did Jones know that USS *Dallas* just inbetween *Red October* and the Soviet sub to distract the torpedo?
In: 0
>So how do submariners do this, especially since there aren’t any viewscreens or windows on the boat?
You already gave the answer: sonar. When the sonar pulse comes back, the information is relayed to a display screen and then you read it. It takes training to understand what the screen is showing you, but it’s all there.
They use sonar for active detection, but this reveals your presence to the enemy due to sending out a loud sound signal, so it is only used in certain situations.
When they need to conceal their presence or bearing, they use hydrophones, which is basically an array of microphones that provide the directional bearing. A trained hydrophone operator can tell what they are listening to and get other information apart from just the bearing. Hydrophones are passive, meaning that they only listen without emitting a signal that can reveal your presence. Unlike sonar, hydrophones do not provide range, although the operator may be able to tell if the object is moving closer or further away by changes in volume. Taking readings over time and plotting them can also tell you the direction the object is moving.
The answer is, most of the time they don’t.
They have charts to make sure that they don’t hit any underwater terrain feature, but most of the time, they just turn everything off because the ocean is a big place and the chances are ridiculously slim that you hit something.
Which was why everyone was surprised when [HMS Vanguard and Le Triomphant](https://en.wikipedia.org/wiki/HMS_Vanguard_and_Le_Triomphant_submarine_collision) hit each other.
When the submarine is looking for other submarines, then usually it just uses Sonar, like in Hunt for Red October. The listen for enemy subs.
Only very very very rarely do they make a sound to listen for how it bounces. That sound will tell everyone listening where your sub is, which is usually bad.
The front of the sub has an array of very sensitive underwater microphones (hydrophones). Just like you can hear where someone is walking around you with your eyes closed, they can use the sonar array to determine which direction the other sub or ship is. All subs make some noise, whether it’s the propeller, the machinery, the cooling pumps for the reactor, or just the crew talking. The sonor operator can try to pick up these sound.
*Dallas* and many other subs also have a towed sensor that allows them to hear behind them unhindered by the boat’s own propeller(s). Soviet subs at the time didn’t have that, and were essentially blind behind them. By staying behind *Red October* (“in their baffles”) *Dallas* was effectively hidden. The “Crazy Ivan” turn was so they could check this blind area behind the ship. It also risked running into any NATO sub that was shadowing them.
The above is referred to as passive sonar. Subs also have a powerful sound emitter, or active sonar. By emitting a pulse (“ping”) of sound, they can more accurately get direction to another sub. And by measuring the time the sound takes to return, they get the range as well. However, the sound can be detected a long way away, announcing the presence of the sub to anyone listening.
Submarine passive sonar can determine the direction a sound is coming from due to wave-form calculations done by computers onboard.
The submarine then uses how quickly the relative direction of the target changes, along with guesses of its speed, to estimate a range.
There is also a bunch of other techniques used to refine estimations regarding various estimations.
This kind of estimation all works together to give the submarine an imperfect idea of their surroundings, and is collectively known as “Target Motion Analysis.” On US submarines, there is a team of 2-3 fire controlmen on shift independent of the sonar team (typically 4 people in a shift) using specialized computers to combine the various data points and keep track of other vessels in the area.
Note: I am deliberately leaving out a lot of details because it’s unnecessary, I’ve forgotten it, and/or it’s classified, but it’s mostly creative uses of trigonometry.
I’m not the OP but this topic also interests me. I understand (I think) the use of passive sonar to “roughly” have a direction and range to another vessel. Someone mentioned trigonometry, but isn’t the submarine’s whole length insuficient to get a proper value especially at great distances?
Latest Answers