Array swivel.

[Bellman]

My line of enquirey elsewhere (TG) has made me wonder whether it could be possible to make some azimuth/elevation
changes underway to the passive sensor arcs by moving the SA within its housing.
A technique incorporated in military aircraft radar with very obvious tactical advantages.

Furthermore should we suppose that the Conf is limited in a coverage arc only centered around 270 and 90 deg ?
Why should it not be centred around 220 and 140 or alternatively angled back resulting in a sensor arc extending
sternwards. In fact why place the Conf. amidships at all where it will be in the main slipstream turbulence area ?

[XabbaRus]

The spherical array is just that a sphere so you don't need to move the array like a radar in a fighter.

[SeaQueen]

Originally Posted by Bellman

My line of enquirey elsewhere (TG) has made me wonder whether it could be possible to make some azimuth/elevation changes underway to the passive sensor arcs by moving the SA within its housing.

WWI and II sonar domes did rotate. Now a days, because sonar arrays are composed of hundreds of transducers, the array's beam pattern can be altered by electronically adjusting the phases of the signals generated by each transducer. In this sense, sonars are very similar to phased-array radars, where the antenna doesn't physically have to move for the beam pattern to move.

Furthermore should we suppose that the Conf is limited in a coverage arc only centered around 270 and 90 deg ?
Why should it not be centred around 220 and 140 or alternatively angled back resulting in a sensor arc extending
sternwards. In fact why place the Conf. amidships at all where it will be in the main slipstream turbulence area ?

I'm not sure what you're referring to as the Conf. I think I might be able to answer your question, though.

[Bellman]

SQ.

So the beam can be swiveled electronically but the physical limits of the array set the outer limits or parameters.

Presumably then the conformal or hull (Conf) arrays also have this same capacity ?

[SeaQueen]

Originally Posted by Bellman

SQ.
So the beam can be swiveled electronically but the physical limits of the array set the outer limits or parameters.

True, provided what you're thinking of as the physical limits of the array are what I'm thinking of as the physical limits of the array. To me, this also includes things like self noise. The shape of the array ultimately is what determines the beam pattern. Then, through various ways of adjusting the phase of the signals coming from the individual hydrophones in that array, you can engage in further "shaping" of the beam pattern. The technique is actually most useful in active sonar, although it's good for passive sonar too, especially for determining bearings.

In sonar, there's actually a single number used to characterize the ability of a sonar array to discriminate the directionality of a signal. It's called the directivity index (DI). It's dependent on the array beam pattern.

Presumably then the conformal or hull (Conf) arrays also have this same capacity ?

True. In fact, the ability to precisely shape the beam pattern of sonar arrays is what allows the Wide Aperture Array (WAA) to determine the range of a target with some reasonable accuracy. The beam pattern isl limited by their shape, though. The fact that arrays are basically big, flat, rectangles dictates a lot of their directionality, but within that you can make a lot of adjustments.

It's just like any antenna, really.

[XabbaRus]

I thought they did use beam forming on the passive spherical transducers.

Is that similar to how it is done on an active phased array radar?

I have always wondered how a WAA array works.

[Bellman]

SQ. Thanks.
To me as a layman, then the sonar operation you describe could be compared to shining a light
upwards/downwards and to the sides. Focusing the beam of attention (so to speak)
both for passive and active functionality.

So if you were in a heavy traffic situation and making a turn to starboard for instance into a baffled area
the sonar operator would focus the beam tp its maximum starboard extent ? Resulting in a withdrawal
of the beam from its existing port limits ?

In order then to make up for this loss the port conformal array/s(or some of them) may be turned to the prow ?
And of course to assist the starboard looking SA the starboard conformal could be 'focused' to
a proportional and ballancing prow extent ?

If this is the case then I take my hat off to those guys and it stirs up a lot of other questions on the limits
of baffles and the tactical implications. The baffled areas would appear then to become constantly variable .
I need to sleep on this. :hmm:

[SeaQueen]

Originally Posted by Bellman

SQ. Thanks.
To me as a layman, then the sonar operation you describe could be compared to shining a light
upwards/downwards and to the sides. Focusing the beam of attention (so to speak)
both for passive and active functionality.

Sort of, and just like a flash light, things fade out towards the fringes of a central bright spot. There's also issues like "side lobes" the size and shape of which depend on the array design. The analogy fails, though, because what people mean by "beam pattern" is really "array gain function" which is probably better thought of as the array's tendancy to amplify signals from certain directions, and not pick them up from others.

So if you were in a heavy traffic situation and making a turn to starboard for instance into a baffled area
the sonar operator would focus the beam tp its maximum starboard extent ? Resulting in a withdrawal
of the beam from its existing port limits ?

Not exactly. More likely a computer would rapidly point the beam in all possible directions to insure that everywhere is looked at with equal efficacy and there's no real blind spots.

If this is the case then I take my hat off to those guys and it stirs up a lot of other questions on the limits
of baffles and the tactical implications. The baffled areas would appear then to become constantly variable .
I need to sleep on this. :hmm:

The baffles are constantly changing, but not for the reasons you're thinking of. They're really a region of increased self noise, so while an array pointed in that direction has increased gain, it also has increased self noise, so it doesn't matter that you have a "brighter flashlight" in that area, because, in effect, there's also an awful lot of smoke. You'd just see the smoke better, if that analogy makes sense.

If you really want to get into this stuff there's some really good books on it. Robert J. Urick wrote, Principles of Underwater Sound and Sound Propagation in the Sea. Also, fairly recently, some researchers at SACLANT wrote Computational Ocean Acoustics which I enjoy. It's good stuff.

[Bellman]

SQ. I think I see a chink of light and many thanks for that.

When I get through with Wayne Hughes( remember ) I guess I would like to read some more.

[SeaQueen]

Originally Posted by Bellman

SQ. I think I see a chink of light and many thanks for that.

When I get through with Wayne Hughes( remember ) I guess I would like to read some more.

How is that going? I'm curious what other people take away from it. The sonar stuff is a lot heavier because it doesn't necessarily rely on simple mathematical models. It relies on some fairly complex ones for people who aren't comfortable solving a partial differential equation here and there. It's worth reading, though, if you want to know about ocean acoustics.

[SeaQueen]

Originally Posted by XabbaRus

I thought they did use beam forming on the passive spherical transducers.

They do. If I implied otherwise, I'm sorry, I didn't mean to imply they didn't.

Is that similar to how it is done on an active phased array radar?

I have always wondered how a WAA array works.

Exactly the same idea. It's just setting up an interference pattern and using that to point the beam in whatever direction you want to or doing essentially the reverse and noticing the phase differences between different signals and then using that to determine their direction.

They were actually doing this sort of thing in sonar before they did it in radar. My sense is that the real advance in phased array radars wasn't the idea (which is just antenna theory) but the ability to manufacture panels with lots and lots of tiny microwave antenna on them. I might be wrong on that, though.

[Bellman]

I'm not strong on mathematical models so progress through some of the theory is leaden.
But topics such as 'Planning with Salvo Equations' can be skipped for a reread - first an overview.

I like the way he integrates the historical perspective into current theories of naval tactics.
The new stuff, added to his earlier work, on missile implementation, is proving heavy going.
In the broader perspective its an exciting book.

[SeaQueen]

Originally Posted by Bellman

I'm not strong on mathematical models so progress through some of the theory is leaden.
But topics such as 'Planning with Salvo Equations' can be skipped for a reread - first an overview.

I like the way he integrates the historical perspective into current theories of naval tactics.
The new stuff, added to his earlier work, on missile implementation, is proving heavy going.
In the broader perspective its an exciting book.

The chapter on "planning with the salvo equations," is the part which will make you a better player at DW, because it will give you an idea of how to balance the number of cruise missiles or torpedos to shoot versus their ability be evaded and their ability to put the target out of action.

The range dependent version he provides is especially instructive, I think, because it's actually very easy, given what we see in the little guide DW provides on the ships and warships in it, and a little bit of experience, to analyze simple scenarios ahead of time in terms of that model, and have a fairly good idea in your head about what the smartest thing (statistically) to do is.

As in all of these questions of operations analysis, what is the smartest thing to do mathematically isn't necessarily the thing that's actually done all the time. That's where leadership is an issue and you start thinking about things like, "these guys aren't totally trained yet," or "we've been at this for 3 days and missing a lot of sleep, can they really pull this off?" But.. ya know.. that's very difficult to capture in any wargame, DW included.

The big thing that he really doesn't cover AT ALL, is search and screening. That's another HUGE topic. It's not easy at all. It's really interesting mathematics, though.

[Bellman]

We have wandered off topic into the fringes of your specialisation.
TG

It's pretty rare to see such good tactical/mission design analysis around here. Bravo Zulu.

SQ.

Building computer models of naval combat is what I do for a living..........they sent me to school for underwater acoutics, taught me the modeling language, and set me up analyzing all kinds of things.

Bellman.

Who will do a TACMAN for Mission Design ?

SQ.

....little bit of experience, to analyze simple scenarios ahead of time in terms of that model, and have a fairly good idea in your head about what the smartest thing (statistically) to do is.

Its tempting to invite you to contribute scenario/s and/or a primer for DW scenario designers to demonstrate
some of the theoretical considerations.
I dont see any security issues in such 'playtime' but would sympathise with a desire to escape from work

I think when we discussed Harpoon you felt that much of the same could be implemented in DW scenario design.
Has this 'full' potential been demonstrated yet ?

The game needs someone, like you, to move us on.

[Bellman]

SQ. I'll take that as a no then.
No problem. Hope I did'nt press too hard.

Thanks again for your thoughts on arrays. :|\