The Ship Model Forum

Sorry Werner, I thought that was your idea of additional serious support for for space based submarine tracking.

Correct me if I am wrong, but wasn't the nuclear bomb that fell off a B 52 near the coast of Spain found by a mathematical algorithm?

If I remember correctly they searched for weeks, and a scientist at MIT cribbed together a mathematical model and the nuke was pinpointed rather quickly?

Ric

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Political Correctness is a doctrine, fostered by a delusional, illogical, liberal minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end."

Math was used to predict the location of the fallen bomb from the course of the lost bomber. Math was not used to process any actual search data to find the bomb.

That's OK ... at the time the world's aggregate computational power was less than that which runs in my home server room.

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If an unfriendly power had attempted to impose on America the mediocre educational performance that exists today, we might well have viewed it as an act of war.

-- "A Nation at Risk" (1983)

Working in an Infrared Compagny, I can write today:

It is impossible to detect a submarime in immersion with an Infrared system.
But a thing like a periscope could be certainly detected after a few second in air because, the thermal propriety of the periscope (metal or synthetic material) is different of the temperature of the sea.

The linear speed of the periscope is also an element of the detection.



Jef

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Current 1/700 WL
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Hmmm, why couldn't the periscope be actively cooled or heated to eliminate the temperature difference?

I reiterate, the mechanism before us does not rely on infrared or thermal properties, but rather the harmonics set up by any large body under the influence of an incompressible medium like water. The effects are rather like a hologram, but are more easily understood when the receiver knows the type of pattern for which to look.

A precursor to the effect under study was witnessed in 18th Century British canals as a wave which would continue along the canal for miles after a barge stopped. This "standing wave" exhibits the properties of water exploited to localize a submarine some depth below the surface.

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If an unfriendly power had attempted to impose on America the mediocre educational performance that exists today, we might well have viewed it as an act of war.

-- "A Nation at Risk" (1983)

That was not a standing wave but a soliton wave and that does not happen on open sea. That wave appeared because the waters were restricted. Normal ship wave systems diverge radialy and quicky reduce in height. If you want to detect that, the sub should not be submerged too much and the sea water should be clear. Here's a pic



Solitons also travel ahead of the ship (normal ship waves never) and can fully reflect on e.g., a dam wall and return to sender. The solitons occur when a ship enters a sudden narrowing. Reflected solitons exiting the channel can partially reflect back at the widening point. Even wiki has something to say, although it says solitons are non-linear, which is not true for water solitons (That is, direct analytical equations predicting them are not linear, numerical simulations using linear theory can predict them). The wiki content seems to be written by a mathematician, hence it is non-understandable and useless if you're not a mathematician.

Note that the waves coming from the ship aren't standing waves either, they travel but with the same speed as the ship. From the ship's point of view, that does seem like a standing wave, but not from the point of view of a fluid particle.

Guest wrote:

"Hmmm, why couldn't the periscope be actively cooled or heated to eliminate the temperature difference?"

That's right the periscope can be cooled or heated, but I think that the inertie to increase or decrease the temperature by a few degrees is enought to detect the object (periscope) in linear movement.
A perfect correction made by cooled or heated is very hard to made & certainly impossible to obtain in an unstable environement (waves & wind).

The infrared result 'll be certainly an irregular object irregulary detected in a regular & linear movement.

For Military Detector Specialist...that mean a periscope



Jef

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Current 1/700 WL
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Why would its temperature be any different from the ambient water and air temperature? I don't see any reason why its outer casing should not be at "room temperature".

Foeth wrote:

"Why would its temperature be any different from the ambient water and air temperature? I don't see any reason why its outer casing should not be at "room temperature".

This physical effect is named "Wind Chill"


Air temperature is 15°c;
when the wind is 20km/h, the object is at 10°c.
When the wind is 45km/h, the object is at 6°c
When the wind is 60km/h, the object is at 5°c

For a submarine, that mean that the periscope, with the speed is cooler than the sea or the air.

More info here:

http://en.wikipedia.org/wiki/Wind_chill


Jef

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Current 1/700 WL
HMS Repulse

Wind chill is only important if there is a temperature difference between the flow and the object. If that object is at the same temperature as the wind, there is no heat exchange and no thermal boundary layer to be affected by the wind. I don't see why it should be cooler.

extract from Wikipedia:

"Wind chill is the apparent temperature felt on exposed skin due to the combination of air temperature and wind speed. Except at higher temperatures, where wind chill is considered less important, the wind chill temperature (often popularly called the "wind chill factor")
is always lower than the air temperature.
In cases where the apparent temperature is higher than the air temperature, the Heat Index (HI) is used instead."



Jef

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Current 1/700 WL
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Exposed skin is at 35-37 degrees C, so there is always a temperature gradient between skin and air. If the wind blows the air closest to the skin away, it is replaced with colder air. Temperature gradients increase, heat flow increases, and the air feels colder (even though it isn't). You experience hot and cold objects by the heat that flows to your skin, not the temperature of the object. Some objects release heat more easliy and feel colder. Compare wood to steel. Even though the temperature is equal, steel feels colder.

If the wind were at 37 degrees, this all doesn't work.

So, no wind chill for objects at the same temperature as the wind.

Foeth wrote:

"So, no wind chill for objects at the same temperature as the wind."

3 elements can change the T° of the periscope,

The wind (Wind Chill) - aleatoire
The speed - constant
The waves - aleatoire.


...

More info to come... perhaps...



Jef

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Current 1/700 WL
HMS Repulse

...After discus with specialists colleages, the detection is possible, but, some factors influence the detection. The T° contrast of the periscope with the sea T° & the air T° environnement & the distance of the periscope from thermical camera.


In calm sea reasonable distance & soft weather,
the thermical camera clearly identify the object in movement.

When the distance is too great, the waves too high, the contrast is too small & the camera is nearly unable to detect.

When it's raining, the detection is impossible.


Some tests were made & the results are classified.


Jef

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Current 1/700 WL
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I did not mention Solitons, nor did I say the principle was based on standing waves or Solitons. I said the dynamics of the water which are exploited by the technology can also (primitively) be seen in these phenomena.

Try as we like to throw logical roadblocks in front of this methodology, it remains that the USSR was sufficiently confident of the process to commit a substantial satellite to it, and it may partially explain the rapid decommissioning of SOSUS in the 1980s. It might be noted that CIS Russian submarine deployments exceeded those in the last days of the USSR.

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If an unfriendly power had attempted to impose on America the mediocre educational performance that exists today, we might well have viewed it as an act of war.

-- "A Nation at Risk" (1983)

But you did say was



and there I complemented you. And informatively at that. But you seem have elevated cognitive dissonance into an art form.

Your water and air temperature will most likely be different, so do you maintain it at air temp, or water? I should think water temp most of the time as you'd be more concerned about detection from aircraft than submarines in regards to this technology.

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Air doesn't show up on most IR images. So to hide the periscope head one would make its temperature the same as background water.