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Thread: Ask An Expert- Naval Forces

  1. #16
    Defense Professional Dreadnought's Avatar
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    Quote Originally Posted by blidgepump View Post
    The impact on a submarine would be minimal, unless it was tied up to a pier.

    Any lurkers that could offer pictures of museum ships in the quake zone would be interesting.
    Not out of the ordinary for the navy to order all ships to sea for such an event, this would have less damage effect of their moorings etc and ofcoarse the ships themselves and whatever lies around them. Mooring lines can take astronomical pounds of force (millions) pending the size (diameter) of the morring lines themselves. Also better for them not to get beat up against other ships and their respective piers. Better to send them to sea where they can manuver and then bring them back into port. You cant help anyone if your ships are f@$&!d up.

    For museum type ships the best you can do is lock em down tight, have all pumps ready and adjust their lines and clear the area incase they were to ground. If they do ground chances are theyre going to be scrapped pending the damage. The money better spent on the population and their needs. Would hate to see that happen to any museum ship but they would fall to the bottom of the list as far as what will get attention first and a museum ship will probably be last.
    Last edited by Dreadnought; 15 Mar 11, at 17:52.
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  2. #17
    Defense Professional RustyBattleship's Avatar
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    The worst a Submarine would receive is a jolt through the hull of the Tsunami shock wave going past it. But that is only if the Sub were fully submerged.

    You do not get gigantic waves until the shock wave approaches shallow water where it also draws in water from the beaches thus giving it more destructive power.

    Out at sea, surface waves rarely exist more than just a swell as the shock wave passes under. Closer to epicenter you can actually see the shock wave underwater as a dark ring rapidly expanding out trying to compress the water.

    But water being nearlly uncompressable becomes a perfect carrier of a tsunami. A shock wave in the air (aka concussion wave) does compress the air but it's higher pressure is quickly absorbed and dissapated into the surrounding atmosphere. Water cannot do that so the energy of the shock wave is merely spread out in a thin line until making landfall.

    So a fully submerged Submarine would receive little or no damage. A large surface ship over deep water may just receive a high swell.

    It's ships tied up to piers or in shallow waters that will really get hit hard. As for memorial ships, docked commercial ships, docked Cruise ships, etc. tied up to a pier or quay wall would benifit themselves by slackening up the mooring lines. The ships may drop low (perhaps even bottom out) as the tsunami shock wave is approaching and then ride high on the tall water waves as they come in. There will be some damage. But if the slack in the mooring lines is just right they will have a better chance of remaining pierside than having the lines part (break in two) and winding up on the beach or down town.
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  3. #18
    Senior Contributor JA Boomer's Avatar
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    Ship design questions:

    1) The Arleigh Burke class and her variants seem to have a forward sloping flight deck. I presume this is to lower the position of the hanger and aft superstructure, in order to reduce the overall center of gravity of the vessel and increase seakeeping abilities?

    2) What is the slightly raised portion of the after super structure on the Arleigh Burke class (Flight IIA) between the aft Mk 41 launcher and the flight deck. It appears to maybe have an exhaust of some sort, perhaps for a compressor/generator used in the helo hanger?

    3) Does the Alvaro de Bazan class Destroyer have two funnels or one? It looks like the forward stack is direction attached to the forward superstructure, but I am not certain that this is a funnel.

    I can post pictures of the specific parts of the ships in question if the discriptions are not clear enough. I'm started to get interested in the "shipbucket" style of drawing, and it's raising a bunch of curious design questions in my head!
    Last edited by JA Boomer; 23 Mar 11, at 22:15.

  4. #19
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    1) The Arleigh Burke class and her variants seem to have a forward sloping flight deck. I presume this is to lower the position of the hanger and aft superstructure, in order to reduce the overall center of gravity of the vessel and increase seakeeping abilities?
    You are correct that the flight deck has a forward/downward sloping flight deck. However it is only a few degrees and does not consequentially affect the height of the hangar/aft superstructure. The hangar is located on the DC deck and perhaps a better way of describing the flight deck's angle is that it is angled aft/upward. I know of a couple reasons posited for why the angle is there but not being the expert on that I'll leave that answer to the more knowledgeable.

    2) What is the slightly raised portion of the after super structure on the Arleigh Burke class (Flight IIA) between the aft Mk 41 launcher and the flight deck. It appears to maybe have an exhaust of some sort, perhaps for a compressor/generator used in the helo hanger?
    At the aft end of the missile deck is a generator exhaust, helicopter landing aids, and an escape scuttle for the HCO tower. There are no generators or compressors in the hangar (of any significant size/consequence).

  5. #20
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    Question: Steam turbines and condenser units

    I am particularly interested in how this relates to WW2-vintage propulsion.

    Water is boiled via fuel oil, the steam system is pressurized to hundreds of PSI or maybe 20 bar, and the expansion across turbine blades moves the ship. The steam is then routed to condensers, which return the water to liquid form. If I understand correctly, the system is closed loop.

    Question: Can these units operate on sea water? How is salt, dissolved solids, etc, dealt with? If they require fresh water, how did a WW2 ship replenish its supply if needed? Were there distillation units on board? Finally, were there mechanisms to capture otherwise wasted heat energy in the condenser section? Thanks!

  6. #21
    Defense Professional Dreadnought's Avatar
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    Question: Can these units operate on sea water? How is salt, dissolved solids, etc, dealt with? If they require fresh water, how did a WW2 ship replenish its supply if needed? Were there distillation units on board? Finally, were there mechanisms to capture otherwise wasted heat energy in the condenser section? Thanks!

    In short no, the units cannot operate on sea water although it is used for cooling in the Main Condenser tubes. All sea water and water taken from shore (outside the condenser) must be distilled through the Evaporators (distillers). This removes all the pollutants from the water such as salt, calcium and other particles making it pure water to be fed to the boilers (sparing the boiler tubes and other mechanicals deposites of unwanted pollutants that deteriorate metals as they are only premitted x amount of parts per million ratio or ppm to pure water) and other equipment. The Evaporators pending their design can make water all day long when the ship is operating and stores this purified water aboard in tanks or voids to be used as feed water or "make up" water when the need arises. It enters the system via the DFT Deaerating Feed Tanks after being processed through the Evaporators.

    Making feedwater alone for a ships boiler is pretty much a science and closely monitiored by sampling and analyzing by the Engineering or Water Treatment dept.

    The distillers or Evaporators as they are know aboard ship are normally located deep inside the ship and normally located close to the ships fire rooms as the first stop for this pure water are you boilers and then the perifery for others ships service. You normally have more then one Evaporator, normally a set of them and also ones for back up (located in different spaces) in case of failure or damage but these are normally reduced in size compared to the main evaporators.

    As far as recycling the energy that has already passed your HP & LP turbines (last stop) in the phase, it is pulled back into the Main Condenser via vacuum. As the steam passes over the Main Condenser tubes (cooled by sea water) in condenses back into water or condensate and then fed back into the DFT where it is recyled through the system all over again.

    Hope that sounds understandable.
    Last edited by Dreadnought; 20 Apr 11, at 16:31.
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  7. #22
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    Quote Originally Posted by Dreadnought View Post

    As far as recycling the energy that has already passed your HP & LP turbines (last stop) in the phase, it is pulled back into the Main Condenser via vacuum. As the steam passes over the Main Condenser tubes (cooled by sea water) in condenses back into water or condensate and then fed back into the DFT where it is recyled through the system all over again.

    Hope that sounds understandable.
    Couple of things. The steam in the main condenser that doesn't condense is used as the Aux Exhaust system which heats the DFT, saltwater heater on the evaps and so on.

    When the feed water leaves the main condenser, it goes through the main air ejector which expells the non-condensable gasses before it travels to the DFT.

  8. #23
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    Thank you, gentlemen... so if I understand correctly, within this closed system, air is undesirable and purged? And the system at rest and cool consists of pure water in bulk, and the voids (if any) are 100% water vapor? Or... as it cools and condenses, check valves admit atmosphere back in to occupy what would otherwise be vacuum?

  9. #24
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    Quote Originally Posted by Chogy View Post
    Thank you, gentlemen... so if I understand correctly, within this closed system, air is undesirable and purged? And the system at rest and cool consists of pure water in bulk, and the voids (if any) are 100% water vapor? Or... as it cools and condenses, check valves admit atmosphere back in to occupy what would otherwise be vacuum?

    You have feed water storage tanks on the ship. When a ship is running at high speed, it's usually using more water than the evaporators make.

    There shouldn't be any more or less air in the water than you'd have in a regular household system. The main condenser fills up with condensate, then the condensate pump pumps the water through the main air ejector to the DFT. Once the water is in the DFT, it's heated and maintained at 240 degrees by aux exhaust steam. From there it goes through the main feed booster pumps which adds something like 50psi more to the system, then to the main feed pumps, up through the economizer tubes then to the steam drum where it's converted to steam.

    The feed water system runs under pressure, no vacuum. Evaporators require vacuum to convert salt water to fresh water.

  10. #25
    Senior Contributor blidgepump's Avatar
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    Would you drink it ???

    Quote Originally Posted by Ytlas View Post
    You have feed water storage tanks on the ship. When a ship is running at high speed, it's usually using more water than the evaporators make.

    There shouldn't be any more or less air in the water than you'd have in a regular household system. The main condenser fills up with condensate, then the condensate pump pumps the water through the main air ejector to the DFT. Once the water is in the DFT, it's heated and maintained at 240 degrees by aux exhaust steam. From there it goes through the main feed booster pumps which adds something like 50psi more to the system, then to the main feed pumps, up through the economizer tubes then to the steam drum where it's converted to steam.

    The feed water system runs under pressure, no vacuum. Evaporators require vacuum to convert salt water to fresh water.
    Excellent recital for the quality of liquid used in a steam engine. My Great Uncles and Grandfather work with steam traction and stationary engines the first half of their lives. Passed on to me was the edict.... "if you wouldn't drink it, don't even think of placing it in the WATER TANK!!!"

    Sounds like good advice for aSteam turbine on a Naval ship, too.

  11. #26
    Defense Professional Dreadnought's Avatar
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    Quote Originally Posted by blidgepump View Post
    Excellent recital for the quality of liquid used in a steam engine. My Great Uncles and Grandfather work with steam traction and stationary engines the first half of their lives. Passed on to me was the edict.... "if you wouldn't drink it, don't even think of placing it in the WATER TANK!!!"

    Sounds like good advice for aSteam turbine on a Naval ship, too.
    Dont know if I would drink it, would probably be close to distilled water in taste not knowing exactly what additives or particles if any are present in it.
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  12. #27
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    About submarines

    Why do the latest subs still have a sail/fin/conning tower?

    Why have that structure stick out and negatively influence drag, silence, etc.

  13. #28
    Defense Professional RustyBattleship's Avatar
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    Quote Originally Posted by FJV View Post
    Why do the latest subs still have a sail/fin/conning tower?

    Why have that structure stick out and negatively influence drag, silence, etc.
    The Sail still provides the same uses as the Conning Towers of older subs. It allows raising of the periscope, snorkel and various antennas high enough out of the water still representing a low profile. If the water is choppy, the top of the sail my appear for just a few seconds. This is far better and definitely a lower profile than the entire upper part of the hull suddenly showing.

    Also, as in the older subs, when on the surface it provides a high position of eyeball to eyeball spotting as well as raising various antennas higher.

    Even most of the smaller research submarines have some sort of conning tower when on the surface. At first glance, even our former Deep Submergence Rescue Vehicles (DSRV rescue and research subs) don't appear to have a conning tower. Actually they had a tear-drop shaped clear plastic dome on top for surface control.
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    Thanks for your reply, yet I really see no overriding reason that mandates the need of a sail on modern day submarines.

    Housing of the periscopes, snorkel and various sensors do not seem like insurmountable technical problems that cannot be overcome.
    (Storing the periscope in the hull, make the periscope extend the height of a sail further, etc, etc)

    There are also very interesting benefits to gain with regards to stealth.

    However, that's just my 2 cents worth, opinions can differ.

    Maybe in the future we'll see submarines without sail.

  15. #30
    Resident Curmudgeon Military Professional Gun Grape's Avatar
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    I believe they are still armored to allow them to poke up through ice

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