LwAmi 2.02 Test 1 Baffles.

[Bellman]

New SA baffle correctly implemented at 120 deg arc but Hull Conf.
remains at the Stock 60 deg ie 150 - 210 deg arc. (not 120-240deg)

Contacts tracked by Conf at bearings 150 and 210. If its intentional OK but 'Greenville didnt indicate
different stern SA and Conf boundaries to the arc.
In reality I suspect they may vary but I dont think that was a n in-game objective.

[LuftWolf]

No, I didn't change the Hull and Conformal Array, they seemed like they were already set to the correct range, and should be able to see slightly farther to the rear than the Sphere and Cylindrical Arrays, since they are on the sides of the hull.

[Bellman]

:) Is this a concession to playability ? In practise we then only move a small step towards realism with sub baffles ?
I am concentrating on a bubblehead perspective only so my remarks are focused.

NTSC 'Greenville' Report P 11 Note 15:-
''As is typical of all submarines, interference from noises generated by the Greenville itself prevented the sonar system from reliably detecting sonar signals between approximately 120 - 240 deg. relative to the vessel's bow. This arc astern of the vessel is known as the ''baffles'' area, and a submarine has to periodically alter course to uncover this null are, or
''clear the baffles,'' for the sonar system ''

We second guess that there is a difference between SA and Conf stern limits. I suspect there is and SQs responses
to my "Swivel Arrays' topic/thread seems to indicate that the limiting factor on sensor coverage is 'own-noise' and therefore both arrays will share the same boundary interference and performance reduction/s.

If I was to guesstimate I would say that your new limit for SA is about right for Conf and the SAs stern limit
boundaries could be 100 (110) - 220 (230) degs.Figure it this way the sub is cigar shaped with a reduced prow profile
therefore the maximum girth amidships the vessels own construction will block sternwards receptivity at that point.
And that is not to include 'slipstream' turbulence which is much more likely to be heaviest at midships.
The conf can be abaft this point lying in quieter flow and would be expected to have a greater arc of coverage sternwards.

But it remains true that all we have in print is the report. Reality (?) v Gamers who I know in the past have
said to this proposal - 'Dont make it more complicated !'

[LuftWolf]

No, I'm certain the modeling of the conformal and hull arrays is accurate.

The hull/conf arrays should have the same geometry fore and aft (symetrical coverage). The primary limiting factor on the sphere arrays is the heavy sound shielding directly between it and the submarine that the hull and conformal arrays don't have.

The acoustic geometry of the conformal arrays, reaching around the tops and bottoms of the rounded hull, make it very likely that they can see farther after than the conformal arrays (draw a picture for yourself and you'll see what I mean).

Also, it is important to remember that the coverage of all sensor arrays is not simply a matter of the sensor surface and the environment, but also the computational processes that lie between the array and the displays. To get a feel for this, picture the TA in your mind... how the hell could you localize sounds on bearings with an array such as that??? The answer can only be found in the computers that process and amplify the raw imput from the sensor in order to display it to the sonarman.

Keep in mind, due to array geometry, that if we reduced the backward sweep of the hull and conformal arrays, logically and mechanically we would have to reduce the forward sweep of the array as well, and this has the duel dissadvantage of being somewhat implausible and much less practical for gameplay.

So I'd say there is both a realism and playability reason for not reducing the baffling of the hull and conformal arrays, in other words, it would be "wrong." ;)

Like I said, draw a picture of the arrays and their sensor cones, and you will see what I mean. :)

[Bellman]

:lol: As you know I'm in the Irish Sea testing but just floated the wire :lol:

Did'nt see much/anything out beyond 7-8 nm with both the SA and Conf last dive. So yet to witness the
'significantly increased sensitivity' :hmm:

That was in a specialy designed scenario with some 20 plus subs and surfs holding formation speed and course.
But in case the lads are not 100% after de-Guinessing Dublin :oops: we will have some more goes. :roll: :yep: ;)

[LuftWolf]

The SeaWolf Hull array will pick up supertankers at 12kts up beyond 30nm and the sphere array will pick up supertankers at 12kts beyond 25nm.

Also, the Han at 5kts will light up the Sphere array beyond 12nm and will even pick up a Collins at 5kts around 4-5nm.

It's important to consider the SL's of these objects and the speeds they are travelling at.

I can email you two of my test scenarios if you would like.

[Bellman]

LWThe hull/conf arrays should have the same geometry fore and aft (symetrical coverage).
Yep - agreed .

LW The primary limiting factor on the sphere arrays is the heavy sound shielding directly between it and the submarine that the hull and conformal arrays don't have.

Yep- exactly my point above so it cant ''see'' as far sternwards

LW The acoustic geometry of the conformal arrays, reaching around the tops and bottoms of the rounded hull, make it very likely that they can see farther after than the conformal arrays

Exactly my point.
And I have done a lot of'' figuring and picturing and drawing'' ;)

LWif we reduced the backward sweep of the hull and conformal arrays, logically and mechanically we would have to reduce the forward sweep of the array

Right - correct and I'm sure thats how it is in reality. I dont think it is ''implausable'' at all. You draw it out. ;) :D

Finaly if the Greenvilles Conf sternwards cover was greater then those limits the report would have said - there was no need for them to make a distinction, and the didnt attempt, between SA and Conf so we have set boundary limits. I cant see how we can justify
any second guessing.

But as I say gameplay considerations will probably prevail :hmm:

[LuftWolf]

The way that each sonar array accomplishes its task is significantly different, so there is no way of directly comparing them.

It's like comparing the a traditional dish radar, to a doppler radar, to the SPY-1 radar. They all use the priniciples of reflected energy, but the actual physics of how they accomplish that are very very different.

Given the lower washout speeds of the Hull/Conformal arrays are already modelled, I'm not sure that making their aparatures more narrow is correct, given that the primary deciding factor of their ability to pick up sounds are determined as much by their computers as their physical arrays.

Also, it's worth noting that in the Ehime Maru report, it is stated that only the sphere array station was manned, and that the public report wouldn't get into details such as the technical differences between sonar arrays on the specific platform, only make general statements about "sonars."

I'm not sure that 20 degrees in the least used array is really "sacrificing realism for gameplay" as the pay-off simply isn't that great.

[Bellman]

:) Just read yours re sonar range.

LWThe SeaWolf Hull array will pick up supertankers at 12kts up beyond 30nm and the sphere array will pick up supertankers at 12kts beyond 25nm.
Please :roll: :huh: :o

We agree I hope that testing should be between like platforms so I think you will appreciate that I
would not be disrespectfull to your work by setting about it casualy

I mentioned 20+ subs and surfs so you would I hope expect me to compare like with like ?

So to on compass quarter run a group of Kilos all same speed depth course etc
Another quarter has FFGs etc etc.

The testing started by creating a special test scenario and I trust that I will always, as in real-life, proceed professionaly :arrgh!:

[Bellman]

:up: Anyways - diving now - speak again tomorrow. :D

Cheers.

[Amizaur]

Personally I think hull sonar cones were OK. Only the sphere were seeing too much to the rear. So we (;)) changed only Sphere and active sonar cones. Hull sonar is a substitute of towed in shallow water. Let it be this way. Phased array radars work usually in +/-60deg cone (more modern ones). If you wanted to have baffles from all sonars +/-60deg in the rear, hull cone would have to be only +/-30deg, don't you think it's little low ? Sensivity may drop on greater angles, but it's quite poor anyway...

P.S. About spherical and active cones - just though to take a look at 688i and Seawolf sonar array pictures (there is picture of SW sphere) and after this look I think again we are now right with reduced cone. Take a look and think how could the sound to the passive or from the active travel at angles greater than 120deg. It's clear that the hull (simply the "disk" sonar is mounted to) blocks field of view of the sphere at angles greater than about 120 degress, it's blocked for sure at 150deg (that's only 30deg from the rear).

http://www.globalsecurity.org/military/systems/ship/images/ssn21-array.jpg

https://www.milnet.com/pentagon/navy/688_cutaway.jpg

By the way the SW sonar dome is much larger than 688i (and it is said somwhere that it's improved) so greater sensivity (and little lower min freq ? :) ) is OK. But Akulas still have bow torpedo tubes and much smaller cylinrical sonar, it should really have lower sensivity than even 688i sphere in realistic sim...

[LuftWolf]

Just read yours re sonar range.

LW Quote:
The SeaWolf Hull array will pick up supertankers at 12kts up beyond 30nm and the sphere array will pick up supertankers at 12kts beyond 25nm.

Please

We agree I hope that testing should be between like platforms so I think you will appreciate that I
would not be disrespectfull to your work by setting about it casualy

Well what do you want??? The Sphere to be a forward looking Towed array???

I tuned the sensors to provide "realistic" performance on the loudest platforms. A very happy consequence of this is that the tunes I have done make the acoustic engine perform almost exactly to what I have read about real world sensor performance in every context I have tested. I explicetly stated that the Sphere and Hull arrays are primarily for situational awareness and not tactic action, which is the job of the TA. Their performance against quiet platforms will not be as dramatically enhanced as against the loudest platforms because that is how the arrays and acoustics function in the game engine, and in real life. If it were something else in real life, then the submarine engineers wouldn't go through all the trouble of putting winches and miles of TA cable on the submarine and sonar designers wouldn't spend years making computational algorthims to make a cable give bearing information (which is really really hard BTW).

If you don't want it to be that way, then start engineering submarine sonars that are more efficient and then I can model them that way. ;)

Don't you think picking up a Collins at 5kts at 4nm is an improvement?

[LuftWolf]

But Akulas still have bow torpedo tubes and much smaller cylinrical sonar, it should really have lower sensivity than even 688i sphere in realistic sim...

I done that! :up:

By the way the SW sonar dome is much larger than 688i (and it is said somwhere that it's improved) so greater sensivity (and little lower min freq ? ) is OK.

I have made the SW arrays the most sensitive, that would be a good thing to include in the next version as well, I believe. But then I would have to do a lot of recalculating... :hmm: But I think it's worth it. :rock:

[Amizaur]

Sorry, it's changed indeed, I loaded wrong db into editor while checking :oops:

If we are talking about that, the low frequency array mounted around the shpere is SW version of hull array ? Maybe we should change SW hull sonar cone to look to the front too ? ;)
Is this same way in 688I, the hull sonar is really inside the bow around sphere and can look to the front too ?

[LuftWolf]

Yikes! :doh:

That would mean completely reworking the SW sonars! :huh: :o

I think we'll have to do some thinking about this. :hmm: :know:

To be completely honest, strictly based on gameplay, I *really* like the way the sonars are working now. However, realism calls... :rock: ;)

[Bellman]

:) I wont press further on the SA and Hull/Conf issues........at present......But could I raise the subject of TA baffles
for your future consideration. Amizaur showed some interest in this topic in early August ?

BellmanI would have expected considerable degradation in the TA receptivity around the 180 deg arc

AmizaurIs TA coverage mearly 360 deg (without ownship sector) like in SC/DW or is it best tp the sides,
mediocre on other angles and worse at 180 deg ?

Rip. Real experience (not sonarman)There is a small null zone directly forward and aft of the
array, but it is very small.

AmizaurHow big would be this very samall null zone of TA, 5 deg. or something ?

RIPMy experience is 20 years old.......Assuming the array is straight and stabalised, 5 deg. sounds about right 10 at the most. Forwrd 20 deg. or so difficult to make contact in. As I recall the bearing error would be more apparent as you neared wash out speed .

So we have a TA null zone at the stern and 'possibly' a 20 deg (not 60 deg) prow null zone.

I think Fish also raised the point that TA droop could take ownship out of the picture. ( Depending on available depth, speed etc)
Ccould we consider any such TA reality adjustments as a trade-off against the increased rear Hull/Conf stern baffle proposed above ?

[Amizaur]

Personally I would like to add 5deg null zone at the rear of TA :). 5 or 10, would have to witness how it looks on display.

[Deathblow]

Sorry, it's changed indeed, I loaded wrong db into editor while checking :oops:

If we are talking about that, the low frequency array mounted around the shpere is SW version of hull array ? Maybe we should change SW hull sonar cone to look to the front too ? ;)
Is this same way in 688I, the hull sonar is really inside the bow around sphere and can look to the front too ?

I've looked at that picture of the SW sonar a thousand times and I just noticed that as well....

.... perhaps the low frequency detection should in fact have a forward arc.... :hmm:

[Bellman]

Thiis is probably 'off the wall' but take a look at the TDC of the USS Nautilus SSN-571 (Timmyg00s photo - vacation trip)

Just a theory but consider that in the high stress pre-torp launch calculation phase the TDC operator must interreact with
sonar and 'steerage.' Grey areas of baffle coverage must be 'no no' so for operational speed and efficiency sonar
will probably be set to predetermined limits.

So could the diagonal markers shown on the main pointer in the photo have some greater
significance than emphasising direction ?

The indicated angles (and arcs) bear more than a passing relationship to sonar baffles.
egs. Prow baffle 30 deg. SA(?) 125 deg. Rear 60 deg.
Could this be more than coincidence and be of real significance ?

http://www.subsim.com/phpBB/viewtopic.php?t=44465

Possibly just idle musing.............but ? :hmm:

[Bellman]

Direct link:-
http://www.pbase.com/timmyg_00/image/51004857

[Bellman]

Image Shack did'nt deliver :hmm:

[LuftWolf]

That gizzmo is largely beyond me, at least just looking a partial photo... :hmm:

I'd imagine, however, that it'd be hard to directly compare anything on the Nautilius to more modern submarines. For example, the BQQ-10 Integrated Fire Control Suite on the 688i directly integrates the sonar with the modern quivalent of the TDC, which is a WWII era piece of technology, originally used to calculate unguided torpedo intercept points... you probably know more than I do, but I am hesitant to try to glean any information on modern sonars from a TDC on the Nautilus.

[Bellman]

Yep - only looking at a ''passing relationship'' :roll: :o :huh: So thats - probably past and **no** relationship. :doh: :P
Now I'll concentrate on the ''baffles'' in my brain. :damn: :arrgh!: :hulk:

Anyways LW all the very best with the job app. - seeing the great job you do here we are all rooting for you. :cool: :rock:

[LuftWolf]

Hehe, thanks! :)