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Old 05-24-2010, 06:55 PM
 
Location: Oklahoma City area
655 posts, read 1,689,329 times
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I know this isn't related to "life" or "issues" but I don't know where else to put it. It's definitely a military subject.

I'm a volunteer at the Naval Undersea Museum in Keyport, WA. My background is all Air Force. so I'm learning a whole new vocabulary. I've started cataloging a group of sub/torpedo computers and calculators (flat plastic, not electronic.) I won't be back at the museum for a few days, so I can't hunt up one of the submarine vets. I haven't been able to find what I need on the Internet, so I'm coming to you. Can you explain, in terms an old retired Air Force logistics broad can understand...

Bearing Rate Computer
Slip Rate Calculator
Figure of Merit Calculator
Towed Array D/E Range Finder

Thanks.
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Old 05-25-2010, 08:09 AM
 
Location: Forests of Maine
29,757 posts, read 47,613,863 times
Reputation: 17641
Quote:
Originally Posted by cindycat View Post
I know this isn't related to "life" or "issues" but I don't know where else to put it. It's definitely a military subject.

I'm a volunteer at the Naval Undersea Museum in Keyport, WA. My background is all Air Force. so I'm learning a whole new vocabulary. I've started cataloging a group of sub/torpedo computers and calculators (flat plastic, not electronic.) I won't be back at the museum for a few days, so I can't hunt up one of the submarine vets. I haven't been able to find what I need on the Internet, so I'm coming to you. Can you explain, in terms an old retired Air Force logistics broad can understand...

Bearing Rate Computer
Slip Rate Calculator
Figure of Merit Calculator
Towed Array D/E Range Finder

Thanks.
Submarines are equipped with lots of modern computers to do things for us. However lessons learned in blood have shown us again and again that if we allow the computers to operate the vessel, we die. Computers mess-up, if they manage to lock onto a false stream of input they will excrete a false stream of output [GIGO - garbage in gives garbage out], they do not allow for common sense, and it is better to maintain a high level of proficiency among the crew.

So with the exception of computers that monitor inertial components, calculate gravity vectors, or spacial references; we leave them in stand-by mode. Sub crews do the math for themselves whenever possible.

When doing calculus manually we use a wide assortment of hand held slide rule devices.

Passive sonar gives us the bearing to each target. We can commonly track hundreds of targets at a time.

Bearing Rate Computer - Commonly we will pick-up a target when it may be 1,000NM away from us. But at that time all the Intell we have is direction from us [relative bearing]. We still lack the target's distance, it's own heading, and it's speed thru water. Thus begins a long series of calculations, beginning with 'bearing rate'. This is simply the rate that a target's bearing changes relative to us over time.

Reading the above, I may need to slow down a bit, a bearing rate comp gives us like: "0.04 degree of bearing change to the left per minute".

You see, we are moving and the target is moving. Our movement defines our vector, the target's movement defines it's vector. Vectors are heading and relative speed. As we more accurately define both of these vectors; then calculus will give us the physical distance between both vectors, and it will also give us the proper heading and speed that a torpedo must travel to be properly introduced to the target.



Slip Rate Calculator - Imagine a wood screw being driven through wood. The pitch of the threads defines how far it goes with each turn. So it is with the vessel's screw. In a perfect world one full revolution of the screw should move you forward a predefined distance. But in the real world it ain't gonna. There is slippage.



Figure of Merit Calculator - The name sounds familiar but I do not recall what it does. Sorry. I know what a 'figure of merit' is, it is a quality factor, but I am spacing how we applied it.



Towed Array D/E Range Finder - We spool out behind us a 3,000 foot cable with a passive sonar array on the end, if we drive in a straight line, eventually the cable behind us will likewise be straight as will be the array.
These arrays are super sensitive to hearing sounds, partly because they are away from 'own ship'. But they can only hear in two directions [ie they can hear to the left and to the right], they can not hear ahead or astern.

Using a towed array you hear a lot of detail about a target, what equipment they are using, who manufactured each of their systems, how each of those systems are holding up to the strains the vessel is putting on them, etc. But you still have no idea how far away they are.

Most target vessels like to hold one heading for a long time. They draw a rhumb line on their chart, the shortest distance between where they left and where they are going. As they follow this line they will never turn. An automated helm can steer a target vessel clear across an ocean like this.

If we make multiple legs while tracking a target we will use this comp to help define the target's distance. It gives you an estimate on the target's distance. Though honestly I never used it for that purpose.

I most commonly used the D/E range finder for making recommendations to the Conn for a better headings to receive signals from Loran transmitters. But that was not really its proper function. Navigating a sub it is nice to have input from devices off ship, Loran is transmitted all around the world, if you can pick-up three of these transmissions at the same time a little math and you can determine your position. Along with a towed array we also like to spool out behind us a long wire antenna that can receive Loran signals and also VLF signals. However this antennas are not omnidirectional, they only receive from certain angles. So I would figure out which signals we had a chance of receiving and used that comp to determine what heading we need to steer before we could receive loran.



Your in Kitsap, very near to Subase Bangor. May I suggest that you contact the Bangor Public Affairs office and ask for their next tour date. They will give you a group tour of a boat. Where you will see these comps hanging from equipment all over the Control room, every crewman will gladly show you how to use them.
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Old 05-25-2010, 04:32 PM
 
Location: Oklahoma City area
655 posts, read 1,689,329 times
Reputation: 530
Thanks, Beekeeper. (I trust you didn't keep them on the sub with you.)

I found a definition of Figure of Merit. Now I gotta "figure" out where it fits in my collection. A figure of merit is a quantity used to characterize the performance of a device, system or method, relative to its alternatives. In engineering, figures of merit are often defined for particular materials or devices in order to determine their relative utility for an application.

I really appreciate all the great info. I've printed it and will study it with the parts in hand when I'm at the museum this week. I'll ask the exhibits manager if there are any similar instruments in the control room mock-up or other displays, so I can see where they were used.

One more question. What is "D/E" in the toad array range finder? (I know it's towed...I just have this vision a group of toads...
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Old 05-25-2010, 04:46 PM
 
Location: Forests of Maine
29,757 posts, read 47,613,863 times
Reputation: 17641
Quote:
Originally Posted by cindycat View Post
Thanks, Beekeeper. (I trust you didn't keep them on the sub with you.)

I found a definition of Figure of Merit. Now I gotta "figure" out where it fits in my collection. A figure of merit is a quantity used to characterize the performance of a device, system or method, relative to its alternatives. In engineering, figures of merit are often defined for particular materials or devices in order to determine their relative utility for an application.

I really appreciate all the great info. I've printed it and will study it with the parts in hand when I'm at the museum this week. I'll ask the exhibits manager if there are any similar instruments in the control room mock-up or other displays, so I can see where they were used.

One more question. What is "D/E" in the toad array range finder? (I know it's towed...I just have this vision a group of toads...
'Figure of Merit' I think is expressed as a reciprocal of 100%, I just do not recall what it was they were expressing the quality of. Does it say 'Kelvin' on it?

'D/E' maybe someone else will chime in. I wanted to say Distance Estimate but it sounded redundant, so I thought it wise to not say anything and hope you did not notice that I had skipped it. Alas you caught me. I have no idea, It has been too long since I had to use one.

I have a couple slide rules in my shadow box, and I have taught their usage. But I chose to burn most of my notes a few years ago, and my memory is slipping today.
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