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Submarines Discussion Board
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Subject: Corrosion Currents Causing ELF Radiation on a Submarine Hull
CardEE    4/26/2007 6:22:40 PM
I was reading some articles that mention corrosion mechanisms can cause strong currents to form on the hull of an ill maintained vessel. Apparently, these currents radiate most of their energy in the ELF band (1 ? 100 Hz) and are enough of a problem that some platforms have devised cancellation schemes (I?m not talking about degaussing).

Does anyone know anything about these currents and possible detection methods? I can?t imagine that they are strong enough to detect from more than a few hundred yards? It also seems that corrosion would generate a random statistical set of currents that would produce incoherent radiation, which is impossible to integrate out of background noise.

Am I missing something obvious here?

CardEE
 
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Show Only Poster Name and Title     Sort in Reverse Order Posted
VelocityVector       4/26/2007 7:21:33 PM

I believe your conclusion is correct.  The environment exhibits true random activity.  Special bins might be evaluated though where it's worthwhile to analyze the bin against other sampled data.  Cites?

v^2
 
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gf0012-aust       4/26/2007 7:39:18 PM

Apparently, these currents radiate most of their energy in the ELF band (1 – 100 Hz) and are enough of a problem that some platforms have devised cancellation schemes (I’m not talking about degaussing).

that doesn't make sense.  its cheaper to clean and re-paint the hull than it would be to "attend" to dealing with emissions using signature management.
somethings missing in the story.
 


 
 
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CardEE       4/26/2007 7:53:48 PM

VelocityVector,

Most of the links just mention ELF or (ELFE) mitigation in passing.  The journal article at the bottom seems more directed, but I do not have a journal subscription and none of my electronic subscriptions cover it.  If you have the patience to look through the first two links, they seem like the best open sources I could find. 

It seems like a good deal of effort has been expended to mitigate ELF response of hull degradation.  I’m just wondering what kind of detection distances one could expect from an ill maintained hull without cancellation technology?

CardEE

h**p://www.jcse.org/Volume9/Preprints/V9Preprint17.pdf

h**p://www.ultra-pmes.com/downloads/Research_Papers/Choice%20of%20Electric%20Field%20Sensor%20Type.pdf 

h**p://www.qinetiq.com/home_us/aboutus/defense/maritime/submarine_concepts_and_designs.html

h**p://www.fnc.co.uk/services_electro.shtml 

Avera, W.; Development Of An Electrical Conductivity Model With Application To A Submarine ELFE Signature (U). Published in The Journal of Underwater Acoustics, July 1999. 
 
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CardEE       4/26/2007 8:08:15 PM
gf0012-aust, 

I agree with you, something is missing from the story. 

The reason that I’m barking up this tree is that I read a non-classified proposal for the USN that specifically mentions building a device to detect these corrosion currents on “ill-maintained” submarines.

As an engineer, I keep my eyes open for people that want to pay me to do work!  However, before pitching a proposal, I’d like to have some confidence that the product I’m building has a practical purpose and isn’t just dead-end research (I’ve done enough of that in this lifetime). 

After spending the last two days reading about electrochemical noise measurements of steel in salt water solution (exciting stuff), I’m not convinced that the noise produced by a corroding hull will be detectable at any tactically useful distance.  The power density spectrum of the noise produced does not seem to exhibit any useful signatures, other than a dull background hiss that is going to be incoherent and nearly impossible to detect.  I must be missing something?

CardEE
 
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gf0012-aust       4/27/2007 12:43:26 AM


After spending the last two days reading about electrochemical noise measurements of steel in salt water solution (exciting stuff), I’m not convinced that the noise produced by a corroding hull will be detectable at any tactically useful distance.  The power
density spectrum of the noise produced does not seem to exhibit any useful signatures, other than a dull background hiss that is going to be incoherent and nearly impossible to detect.  I must be missing something?

CardEE


I'm not really keen about having this kind of discussion in an open forum, but I have serious doubts about an ability to conduct long range sensing on a corroding hull.
 
there are easier and existing ways to detect the target.  ( I can see an assisted benefit if searching the sea bed for static foreign objects, but its still easier to run something like a ms 1000r  than search for an acoustic anomaly which will always be discrete and "unknown")
 
 
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gf0012-aust       4/27/2007 12:52:20 AM

Most of the links just mention ELF or (ELFE) mitigation in passing.  The journal article at the bottom seems more directed, but I do not have a journal subscription and none of my electronic subscriptions cover it.                                                                                            
If you have the patience to look through the first two links, they seem like the best open sources I could find. 

It seems like a good deal of effort has been expended to mitigate ELF response of hull degradation.  I’m just wondering what kind of detection distances one could expect from an ill maintained hull without cancellation technology?


CardEE


h**p://www.jcse.org/Volume9/Preprints/V9Preprint17.pdf


h**p://www.ultra-pmes.com/downloads/Research_Papers/Choice%20of%20Electric%20Field%20Sensor%20Type.pdf 


h**p://www.qinetiq.com/home_us/aboutus/defense/maritime/submarine_concepts_and_designs.html


h**p://www.fnc.co.uk/services_electro.shtml 


Avera, W.; Development Of An Electrical Conductivity Model With Application To A Submarine ELFE Signature (U). Published in The Journal of Underwater Acoustics, July 1999. 


Basically and simplistically speaking the US, France and Australia have signature management on their subs.  The australian tech has been provided to US, UK, Sweden (surface vessels) and a nameless country ()
There is a secondary acoustic technology we've developed which has only been shared with US and UK - and I'd argue that it would make the above papers rather redundant.
I really struggle to see the value in it (and question the concept) when other superior (and some simpler) solutions are available
 
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CardEE       4/27/2007 1:48:19 AM
gf0012-aust, 

I agree, I should probably just shut-up on the online forum.  Nothing I’ve said is in any way classified, but it’s probably best to say nothing.

If you are willing to continue the discussion offline, shoot me an email:

CardEE.Hokie atthislocation gmail.com

CardEE
 
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gf0012-aust       4/27/2007 7:51:17 PM

CardEE.Hokie atthislocation gmail.com


mate, check your inbox.
 
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ingnoway    neutrons   5/19/2007 9:12:54 PM

I was reading some articles that mention corrosion mechanisms can cause strong currents to form on the hull of an ill maintained vessel. Apparently, these currents radiate most of their energy in the ELF band (1 – 100 Hz) and are enough of a problem that some platforms have devised cancellation schemes (I’m not talking about degaussing).

Does anyone know anything about these currents and possible detection methods? I can’t imagine that they are strong enough to detect from more than a few hundred yards? It also seems that corrosion would generate a random statistical set of currents that would produce incoherent radiation, which is impossible to integrate out of background noise.

Am I missing something obvious here?

CardEE

Since the sigs are so weak, they need some neutron data also.
 
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the_boat_guy       6/6/2007 6:12:49 AM
I was at a conference on warship cathodic protection hosted at the defence academy of the UK at Shrivenham a few years ago(at least the unclassified section).   These signals were a major thread of discussion, they are real and also detecable though the exact methods for doing that are highly classified.  They are generated by a contantly changing voltage running through the cathodic protection systems of the submarines.  A lot of research has been done over the last few years into mitigating these signals.
 
I have the conference preceedings somewhere.
 
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gf0012-aust       6/6/2007 6:38:45 PM
 
nobody is denying the presence of the effect, the issue is meaningful detection  - esp in a real time hot environment.
 
outside of a structured and managed test environment there is no (public) meaningful tech that has the power and portability to detect such events in a tactical environment (or even a benign test environment where boats still have room to manouvre)
 
 
 
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