From: Jim Christley <jchris@bbn.com>
Newsgroups: sci.military.naval
Subject: Re: Idea on Litorral sub
Date: Wed, 09 Oct 1996 11:20:59 -0500

Folks:

I keep seeing the statement or something similar, "SSN's always are 
louder than conventional subs..."  

That statement is not true.  At present the quietest submarines in the 
world, according to published work [Broadband, 5-7 knots] are Los 
Angeles Class (Improved) and Ohio Class.  This is passive only.    

Rigged for quiet operations, (ultra-quiet in US Naval language), a 
diesel submarine will become quieter.  So will either one of the two 
classes mentioned above.  They are both very close to having a 
detectability range of approximately hull size.  That means you need to 
use something other than passive only sonar to detect the submarine.

Going active, contrary to popular opinion, does not mean your instant 
death nor does it mean you are detected.  What it means is that you have 
most probably detected the opposing submarine and now have his range.  
It also means that he knows you are here.  Where is another problem.

If both sides are using active sonar, the problem isn't silence, it is 
now target strength.  Which is a measure of how well your submarine 
reflects the incoming sound signal.  

There is also the use of bistatic sonar processing to consider.  That is 
where there are two sonar platforms operating in conjunction with each 
other.  One goes active, the other uses the initial sound signal and the 
reflected signal off the target.  The second sonar platform does not 
need to be active.  

Regards
Jim

From: Jim Christley <jchris@bbn.com>
Newsgroups: sci.military.naval
Subject: Re: Submarine, Littorial and NSSN
Date: Thu, 10 Oct 1996 15:39:32 -0500

Re the request for statement that nucs are quieter than non-nucs.

The broadband numbers are published in Stefanik: Strategic ASW and Naval 
Strategy which is a bit dated but an updated look is available in an 
unclassified US Industrial Association brochure dated Aug 1996.  

The narrowband arguments, numbers or ranges have not been openly 
published. At least I don't think so.

The move to active from passive mode in the monostatic problem would 
presume you have detection in passive but not of sufficient S/N and/or 
to intermittant to perform TMA or other tracking methods to gain a 
solution. Bistatic, of course, presents a differing set of 
circumstances.

I am not privy to any tactical treatises for present submarine conflicts 
so am really making presumptions, which may be taken as such.  What I do 
know is that the ASW problem is moving back into the forefront and that 
it is becoming important enough to resurrect NavSea offices to deal with 
the blue water problem.  The "brown water" problem may be 1) Relatively 
unsolvable or 2)Solved or 3)the object of a strategic and/or tactical 
workaround.

Any hard information would be greatly appreciated.

Regards
Jim Christley