How does a submarines sonar work?

John

How does a submarines sonar work?

I recently watched some submarine movies, such as the hunt for the red October, and crimson tide; and have subsequently become interested in submarines. However my understanding of sonar is very limited; and I don’t understand how it works. I understand that active sonar, involves emitting sound from the submarine, and that the characteristics of the echoes which you get from this, are then used to compile data related to other submarines. And that passive sonar involves listening for the sounds of other vehicles-that’s all I know.

I don’t’ understand -firstly:

1. The types and quantity of data which you can get from sonar, such as the distance of objects, their density, speed, shape etc.


And secondly:


2. How whatever data you get is interpreted by the ships sonar operator (or whatever their called) in a useful way.


I am aware that echo cardio scans can use sound to get a 3D image of organs in the body- so can a submarines sonar do this? And then display this on a computer screen; so that 3D images of vehicles, shoals of fish, the contours of land on the coast, icebergs etc can be seen that way? Presumably you would definitely need all of that kind of information displayed in that form, to navigate a submarine through the ocean and hit moving targets. However all you see in the movies is a guy wearing headphones, whilst looking at a screen with blips on it - this doesn’t make sense.
How can a guy tell things such as vehicles or even a whale or something’s shape, distance, speed, density etc just from listening to it? And what about things which are not moving and making sound, such as the land or icebergs? The only thing which you seem to get from active sonar is blips on a screen. How does that tell you something’s shape, speed, distance density etc?
I would greatly appreciate it if you can answer this question for me.

Answer
Submarines receive sounds from many hydrophones. Hydrophones are acoustic transducers. Today, sonar officers rarely listen sounds in order to make a decision. Computers analyze sounds( generally cavitation noise and machinery noise) and compare them with their library and display targets speed, distance, bearing, course, type, if pinging, active sonar type and power that reaches to submarine and etc.
Navy submarines (generally) don't show shapes and density because it is unnecessary. However, almost all submarine active sonars can make sea floor scan etc. to see shapes.

Lastly, submarines have active sonars but, unlike action films, they don't use them. Because if they send only single ping, enemy can easily track from miles away and destroy the submarine. Sound in water can travel huge distance.

Rangers and submarines?

mr marine

So I was watching the military channel earlier and they were talking about submarines the US use and they mentioned "the ability to send and extract SEALS and Rangers" through these I guess you can say 'underwater compartments'. The Ranger/submarine part surprised me because I was not aware that Rangers conducted missions through submarines like that. I thought that was for SF, SEALS, MARSOC, etc. but not Rangers. I'm not trying say that TV is always right, but I'm just curious if that's true.
Post 1. Not what I'm asking. Do ARMY RANGERS conduct missions where they are required to E&E through submarines?

Answer
SEALS aboard a submarine are not sitting around waiting for a mission. They are more likely to have a 'real" job aboard the sub. The SEAL team might have one guy who works on the bridge, another in the engine room, and yet another in the torpedo section.

You'll see in the Virginia Class Submarine, there is a mini sub for the SEALS. http://www.sublant.navy.mil/Graphics/VA-1.jpg

As for the Rangers, believe it or not, SF, SEALS, Rangers, Marine Recon, AF Search and Rescue attend many of the same courses, and a Ranger unit might use the sub.

They all go to the same Army Jump School.
They all go to Underwater Demolition through the Navy.
They used to all go to the Air Forces SERE before each branch opened their own.
SEALs who pick the medic career field have to go through the Armys Special Forces Medic Q Course.

One of the lessons of WWII is that the rival branches can not always rely on the others' expertise to help.
Therefore, the Air Force isn't the only branch with pilots, the Navy isn't the only branch with divers, and I believe this could be what you're looking for:
"Submarines are part of five aircraft carrier battle groups the Navy is operating in the Eastern Mediterranean or Persian Gulf area. Others are operating independently. One of the new post-Cold War duties for nuclear submarines is to serve as floating bases for a variety of special operations missions, launching Navy SEAL teams, Army Rangers, Marine Corps reconnaissance units and other special warfare forces." http://www.jcs-group.com/military/appointed/subreturn.html

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