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hachiman
Joined: 25 Dec 2001
Posts: 722
Location: Edinburgh Jockland
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 Posted: Wed Oct 20, 2004 2:49 pm Post subject: For Jamie or anyone from Sonalysts |
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Hi
In 688I and Sub Command you could not tell how many Screws a Target has.
Will this at last be modelled in DW?
The SIMHQ Preview seemed to hint at it when the Kilo first discovered the Vosprey albeit a bit of Fiction Fun!
“Conn, sonar. Contact bearing 063. An 18 kilohertz sonar! And we hear it on the hydrophone now, twin screws. Identify the contact as Master 01.”
“In these waters, a surface contact with a Western sonar? And twin screws? It must be enemy, a warship.”
Thanx |
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Jamie
Joined: 07 Jul 2002
Posts: 779
Location: Waterford, CT (USA)
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| Posted: Thu Oct 21, 2004 1:28 pm Post subject: Re: For Jamie or anyone from Sonalysts |
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| hachiman wrote: | Hi
In 688I and Sub Command you could not tell how many Screws a Target has.
Will this at last be modelled in DW?
The SIMHQ Preview seemed to hint at it when the Kilo first discovered the Vosprey albeit a bit of Fiction Fun! ...
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Hey hachiman,
No, I think that was for a little bit of "dramatic effect" ... DEMON will be very similar to how it was before with the use of TPK to determine speed, etc. Sometimes there is reason to complicate things for the sake of realism (and game play) and other time it merely adds complexity for the sake of complexity.
In this case, many people already did not like the fact that they had to consult USNI to obtain the TPK and to feed that into the DEMON (they thought it was unintuitive). I know that it sounds silly, but there are two sides to the issue in that sense, and we opted to just leave it as it was and concentrate on other areas instead... |
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sonar732
Joined: 03 Jul 2003
Posts: 1358
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| Posted: Thu Oct 21, 2004 3:00 pm Post subject: Re: For Jamie or anyone from Sonalysts |
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| hachiman wrote: | Hi
In 688I and Sub Command you could not tell how many Screws a Target has.
Will this at last be modelled in DW?
The SIMHQ Preview seemed to hint at it when the Kilo first discovered the Vosprey albeit a bit of Fiction Fun!
“Conn, sonar. Contact bearing 063. An 18 kilohertz sonar! And we hear it on the hydrophone now, twin screws. Identify the contact as Master 01.”
“In these waters, a surface contact with a Western sonar? And twin screws? It must be enemy, a warship.”
Thanx |
I'm sure that the mainstream won't care about how many screws a contact has. The ones who worry about realism have come to that conclusion and as far as I can see...no one really has complained. Besides...a good sonar operator knows the number of shafts and blades the various contact has. Not to mention that there are multiple ways of classifying a contact as a warship besides the actual broadband reading. It is touched with "Western sonar", narrowband frequency lines, DEMON reading, and the navigation style (multiple changes in speed and/or heading). |
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Ritual
Joined: 18 Oct 2004
Posts: 10
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| Posted: Thu Oct 21, 2004 8:53 pm Post subject: |
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Wasnt it a valid tactic to use different propellers to not give you a distinct classsification to the enemy?
Or have I read too many books.
And dont the new submarines use engines typical of water jets in some kind of stealth configuration to run silent. |
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sonar732
Joined: 03 Jul 2003
Posts: 1358
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| Posted: Thu Oct 21, 2004 9:21 pm Post subject: |
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| Ritual wrote: | Wasnt it a valid tactic to use different propellers to not give you a distinct classsification to the enemy?
Or have I read too many books.
And dont the new submarines use engines typical of water jets in some kind of stealth configuration to run silent. |
Each different style of ship has it's own "set" of number of shafts with a certain number of bladed screw. This does not change. Carriers have 4 shafts, destroyers and cruisers have 2, frigates have 1, etc... On DEMON the number of blades and shafts come thru by the "strength" of the line. |
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Furia
Joined: 14 Mar 2001
Posts: 558
Location: Spain
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| Posted: Fri Oct 22, 2004 4:12 am Post subject: |
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| Ritual wrote: | Or have I read too many books.
And dont the new submarines use engines typical of water jets in some kind of stealth configuration to run silent. |
The only sub I know that used water jets for propulsion was Marko Ramius Typhoon in the Hunt for Red October motion picture 
I have heard no opereational combat sub with such propulsion but if you know something els about this I would love to hear.
The ammount of water required to flow through the jet duct in order to move a 5000 tons sub would be really large and that makes noise.
Take the example of an airplane reactor. Most of the moise radiated you hear comes from the sucction and compression of the air instead just from the combustion. If the air makes such noise, I just imagine what cubic meters of water would do if forced to flow through and narrow duct.
I think actual scimitar shaped propellers are quite advanced to allow quiet silent running at low speeds. |
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hachiman
Joined: 25 Dec 2001
Posts: 722
Location: Edinburgh Jockland
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| Posted: Fri Oct 22, 2004 4:26 am Post subject: |
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| Thanx for the reply Jamie. |
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Scion
Joined: 31 May 2001
Posts: 1552
Location: New Zealand
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| Posted: Fri Oct 22, 2004 8:27 am Post subject: |
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| The Seawolf subs, the 688(i) Cheyenne, and many other subs around the world have Pump-Jet Propulsers. These replace the standard propeller. They allow the sub to operate quiter, and to travel faster without cavitating. |
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MSgalileo
Joined: 24 Aug 2003
Posts: 336
Location: Paris (France)
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Furia
Joined: 14 Mar 2001
Posts: 558
Location: Spain
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| Posted: Mon Oct 25, 2004 6:49 pm Post subject: |
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| Scion wrote: | | The Seawolf subs, the 688(i) Cheyenne, and many other subs around the world have Pump-Jet Propulsers. These replace the standard propeller. They allow the sub to operate quiter, and to travel faster without cavitating. |
Well, I have heard of no evidence about this.
A shroudered screw does not mean a pump jet.
I guess we are talking about two diferent things.
So please if you can share with us what information you have as Pump Jet driven submarines it would be great because so far even the new models I know are driven by propellers, scimitar blades kind, but propellers. |
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badhat17
Joined: 07 Jul 2002
Posts: 385
Location: hub o de universe
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| Posted: Mon Oct 25, 2004 8:24 pm Post subject: |
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The difference between a shrouded propellor and a pumpjet is the use of a stator blade in the pumpjet , it is very similiar to the primary compressor stage in an axial flow turbojet .
Pumpjet is shown at right handside on that gif .
The UK mod website has a document for manufacturing standards for contractors which contains the following definitions ,
| Quote: | | A propulsor consisting of a set of stationary blades (stators) and a set of identical twisted rotating blades (rotors) equally spaced around a rotating hub or boss housed within an open annular duct. |
| Quote: | | A pump-jet is described as PRE-SWIRL or POST-SWIRL depending on the relative positions of the rotor and stator. A PRE-SWIRL pump-jet has the stator forward of the rotor. A POST-SWIRL pump-jet has the stator aft of the rotor. |
A few sketches are included in the document but they lack details for some reason . 
http://www.dstan.mod.uk/data/02/304/03000200.pdf |
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finiteless
Joined: 05 Aug 2004
Posts: 751
Location: Australia
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| Posted: Mon Oct 25, 2004 9:02 pm Post subject: |
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Hmm, OT, but that reminds me of a trawler I once worked on about twenty years ago, the owner/driver installed a shrowded prop during refit and all was sweet; better cruise speed, less rpm, lower engine room heat, less fuel consumption, less noise, he discussed it at length with all the other operators on the marine band between shots, (who were keen to hear about it, and perhaps a bit envious of it) ... then an inquisitive 14 foot hammerhead got lodged in it, and we were given a tow back to port and removed it (shark remains and shroud). I might have tried some steel bars to keep the big sharks from trying to swim through it but the incident was so embarrassing it had to be removed.  |
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