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  #101  
Old 05-23-2008, 08:53 AM
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Originally Posted by Akula2ssn View Post
Towed arrays are actually kind of interesting. They aren't really deployed for the purpose of searching behind the sub although that is indeed something that they are capable of. The towed array actually serves as the primary tactical array. It has greater detection range resolution and other capabilities than the spherical array in the nose of a sub. Of course the main problem is that the towed array has a forward blind spot. The spherical array in the nose is mostly used for navigational purposes (basically making sure that you don't bump into something). So a lot of times, the sub has to do turns in order to bring the towed array around to search bearings that were in front of the sub.
*humbled*
I'm not sure if I understand that.
A tactical array?
The forward system is navigational and sees forward and the towed array is tactial and sees aft...I don't understand...

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Originally Posted by Akula2ssn View Post
Actually when you think about it, if we just look at the lateral sensor array, the Galaxy probably has better forward detection capabilities than the port, starboard, and aft arrays because of how wide the saucer section is which translates to a larger forward array. The Intrepid class lateral array probably has better detection abilities on the port and starboard sides than the forward and aft arcs, but the Intrepid can probably easily compensate on the forward arc depending on what kind of sensor packages are mounted in the deflector dish.

I'm not sure. I had to think for a moment about the comparison. Voyager has two partial forward arrays and one forward sensor pallete. It's hard for me to judge them on size because I can't exactly judge the surface area...however considering just the size of the Galaxy it's self I wouldn't doubt it.

My continued research reveals yet another intresting...and perhaps unexplected anomoly. While searching for the Phoenix the Enterprise just suddenly finds her. We are told that they are 16 hours to intercept at warp four...if we trust the warp speed chart (an really there isn't much choice) then the Etnerprise was only a scant 50 billion miles from the Pheonix after it blew Cardassian warship and supply ship! Isn't that like an eighth of a lightyear?!

What the heck! That's well inside sensor range! Two episodes confirm sensor range at 10 light years or several light years in bloodlines.
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  #102  
Old 05-23-2008, 09:05 AM
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The towed sonar array doesn't just see aft. It looks to the aft, port, starboard, and a little bit forward except it can't see past the sub that's towing it. So let's say that you were to draw a circle around a submarine to represent sonar coverage. If you cut out a slice in the circle where the forward quarter of the sub is like you would a pie, the remaining part of the circle represents the coverage of the towed array. So basically the coverage of the array will look like Pacman with his mouth open. Hopefully that makes more sense.
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  #103  
Old 05-23-2008, 09:18 AM
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Here's a quick diagram I made to illustrate what I mean.


The black area roughly represents the blind spot of the towed array and the yellow represents the coverage of the array.
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  #104  
Old 05-23-2008, 04:58 PM
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Yes it does...It didn't make sense to me the a tactical array could see only aft. So the range of sight is much larger.
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  #105  
Old 05-23-2008, 06:16 PM
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Not only larger range, but also greater resolution. Basically the towed array is setup like this. It's a long cable and let's say for example that the sub can stream out about 2000 feet of cable. And say every two feet, give or take, is a hydrophone. So if the arrays is fully deployed, the sub will be towing about 1000 hydrophones behind it. The longer the cable they have streamed out, the more hydrophones they have out and the greater the detection abilities are. The nice thing about this is that if you know the distance between the individual hydrophones then you can triangulate the targets range and determine course and speed of the target.

I believe the towed array does require a little bit of work if you only have the target detected on the towed array and not on any other array. The funny thing is that if I remember correctly, using the towed array itself you get ghost contacts that you have to work out either by confirming the target bearing by getting close enough to pick it up on the hull mounted sonars or doing some course changes. It's kind of confusing to understand, but what it means is this:

If you're sub is heading north (course 000) with the towed array streamed behind it and it picks up a contact that is on a bearing of 100 (which in this situation is both the true and relative bearing) then the towed array is also going to be showing the target as on a bearing of 260. The towed array doesn't have the ability to tell if the target is really 80 degrees to the right of the stern or 80 degrees to the left of the stern. In order to tell which is the true contact, you have to turn the sub a different direction. And as the towed array straightens out on the new heading, the false contact with change it's bearing while the real contact will remain steady.

And if you don't understand what I just said, I don't blame you. I didn't understand it until just a few minutes ago after almost 8 years of wrestling with that one. Even my naval weapons and engineering instructor who was a sub officer couldn't really explain it to me all that well.
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  #106  
Old 05-23-2008, 08:25 PM
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Quote:
Originally Posted by Akula2ssn View Post
Not only larger range, but also greater resolution. Basically the towed array is setup like this. It's a long cable and let's say for example that the sub can stream out about 2000 feet of cable. And say every two feet, give or take, is a hydrophone. So if the arrays is fully deployed, the sub will be towing about 1000 hydrophones behind it. The longer the cable they have streamed out, the more hydrophones they have out and the greater the detection abilities are. The nice thing about this is that if you know the distance between the individual hydrophones then you can triangulate the targets range and determine course and speed of the target.

I believe the towed array does require a little bit of work if you only have the target detected on the towed array and not on any other array. The funny thing is that if I remember correctly, using the towed array itself you get ghost contacts that you have to work out either by confirming the target bearing by getting close enough to pick it up on the hull mounted sonars or doing some course changes. It's kind of confusing to understand, but what it means is this:

If you're sub is heading north (course 000) with the towed array streamed behind it and it picks up a contact that is on a bearing of 100 (which in this situation is both the true and relative bearing) then the towed array is also going to be showing the target as on a bearing of 260. The towed array doesn't have the ability to tell if the target is really 80 degrees to the right of the stern or 80 degrees to the left of the stern. In order to tell which is the true contact, you have to turn the sub a different direction. And as the towed array straightens out on the new heading, the false contact with change it's bearing while the real contact will remain steady.

And if you don't understand what I just said, I don't blame you. I didn't understand it until just a few minutes ago after almost 8 years of wrestling with that one. Even my naval weapons and engineering instructor who was a sub officer couldn't really explain it to me all that well.

I heard that the towed array was actual..."towed" behind the sub. I had no idea it was in those numbers.

Unfortunantly any time I hear towed array I keep thinkin of a sonar dome in the the aft sail/rudder. I must have seen a bulg in a design and assumed that it was a rear sonar aray I had been hearing about. It wasn't untill I read...Silent Hunt by Charles D Taylor that began to clear up the misconception.
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  #107  
Old 05-23-2008, 08:31 PM
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You're not the only one. I used to think it was a pod that was towed behind the sub. Kind of like the pod that you see on the upper rudder on the Akula, Sierra, and Victor class subs. Later I realized that the pod was simply the housing that holds the array when it's stowed.
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  #108  
Old 05-23-2008, 10:22 PM
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You're not the only one. I used to think it was a pod that was towed behind the sub. Kind of like the pod that you see on the upper rudder on the Akula, Sierra, and Victor class subs. Later I realized that the pod was simply the housing that holds the array when it's stowed.
NOW that is the missing part of the puzzle.
That makes sense. I think I actally saw a diagram that said it was the towed array and I didnt't know that it had to be deployed with a cable.
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