Real Submarine Technology & History Q&A

[Stealhead]

Ok I have a question about a structure seen on some older submarines. Those "cage" things on the sterns of some what are those? I notice that some warships also have them. Are they sort of like a bumper to protect the screws?

[Sledgehammer427]

yeah, I ahve a painting somewhere of those guards pushing a mine cable away from the screws, so yeah.

also, i'm sure they are there so people dont get...fouled up.

thats what I know anywho

[DaveyJ576]

Originally Posted by Stealhead

Ok I have a question about a structure seen on some older submarines. Those "cage" things on the sterns of some what are those? I notice that some warships also have them. Are they sort of like a bumper to protect the screws?

You are exactly correct. They are propeller guards. They are mostly in place to prevent a tugboat from hitting the screws while maneuvering in harbor, or to keep the screws from hitting the pier pilings. Many subs had them temporarily removed during the war, the reasoning not being entirely clear.

[Platapus]

Originally Posted by DaveyJ576

In the early days, the officers that made up the Gun Club looked down their blue blood noses at the "pigboats". They considered them nothing but a toy and the sailors that manned them to be rude, crude, and socially unacceptable.

]

You mean they aint?

[Platapus]

Originally Posted by Kapitan Soniboy

II think. They mounted an automatic weather station there. Maybe it was in Canada...

If this type of thing interests you, you might be interested in reading about the Battle of Greenland which was a land battle between Danish and German weathermen.

A piece of WWII history few know.

[Stealhead]

I was going to say it seems that not all subs had them. Might just have been something they did not do at the yards to save time.Must have been some reason for them being removed.

[Platapus]

Another nit-picky question

Originally Posted by DaveyJ576

A vessel designated with the prefix USS (United States Ship) is owned and operated by the United States Navy and manned with USN sailors. A vessel that carries the tag USNS (United States Naval Ship) is owned by the Department of the Navy, but is operated by the Military Sealift Command and is manned by civilian mariners.

I fully understand your explanation about the crews. Thank you. My nit-picky question is about the "different" navies in your answer.

Is there some legal distinction between United States Navy and Department of the Navy?

Are there some parts of one that aint in the other?

[DaveyJ576]

I should have written Department of Defense instead of Navy. The MSC is a joint command of the DOD. They support operations of all the services to a point, although their primary focus is the Navy. The ships do not carry an official commission as vessels of the USN but are government owned and operated in support of DOD operations, thus the United States Naval Ship title, used to differentiate it from a regular Navy vessel.

Most MSC ships that are assigned to a task force or group (oilers and stores ships) will carry a detachment of Navy sailors to augment the civilian crew. They will primarily assist in communications.

I never really thought of it that way due to the significant differences in shipboard organization, but I guess you could consider it a second Navy.

The Department of the Navy consists of two major components: the United States Navy and the United States Marine Corps. Yes, to their everlasting chagrin, the mighty Marines are actually a part of the DON.

The United States Coast Guard is a separate uniformed service that operates under the control of the Department of Homeland Security. Wikipedia actually has a pretty good entry on the USCG and it describes the legal distinction of this service.

[Platapus]

Thanks, as always, for the clear explanation.

This learnin stuff is good!

[Stormende]

Great thread!

Back to Silent Hunter, the first game had a feature that was not implemented in the sequel. It was the chlorine factor, we must surface. How often the batteries broke to the point that chlorine was present inside the sub and was not the anti gas masks enough to deal with it until the time to surface was better with no destroyers around?

Also I read somewhere that an electric sub is harder to detect by passive sonar than a nuclear, is it due to the reactor makes more noise or what?

Thankx in advance for this great thread and the replies and questions my fellow skippers have made. I gave you another star even if it already is 5 stars thread.

[Sensekhmet]

It seems modern diesel subs really are quiet. For example, since we joined the NATO, it seems every western nation wants our Kilo class sub (ORP Orzel) to take part in their sea excercises! And it's not even the newer Kilo generation. Oh, but don't believe mr. Clancy's 'black sea hole' Kilo theory, the man's delusional.
As for the Kilo class itself it seems it was specifically designed to detect and stalk/hunt big nuclear subs.

[Stealhead]

The Kilo is nothing compared to the current German and Swedish made subs ever heard of AIPS?But the bad guys will have Kilos so it is a good idea to train aginst them. The newer SSKs with AIPS that many western navies are using and also the russians are selling are perfect in what they call Green Water or platorial(i know that is misspelled) waters are very quiet nuclear powed ships are perfect in the deep ocean where there is a lot of water to hide in but not so great aside form the Sea Wolf and Virginia class in green waters.It is really a change in how most navies choose to fight. You can have a very small cheap navy be pretty nasty by simply playing an area denial war in shallow water where an AIPS SSK can hide very well that makes a big ship like a CV think twice about going into those waters.I belive the Kilo was an imporvement on the Tango class and they where they where perfect to control places like the Black Sea or the Med. in a "hot" Cold War era the Kilo is the son of the Tango which is the son of the Whiskey class all SSKs.What the US Navy must and is doing is adapt to this new very serious threat the new SSK.

[DaveyJ576]

Originally Posted by Stormende

How often the batteries broke to the point that chlorine was present inside the sub and was not the anti gas masks enough to deal with it until the time to surface was better with no destroyers around?

Chlorine gas is generated when sea water mixes with the acid inside the batteries. It is extremely deadly and only a very small amount can kill you. I do not have any data as to how often this occurred in the USN fleet boats, but theoretically it can happen anytime sea water gets into the battery well. I do know, however, that it was not a common occurrence.

The individual jars that contained the battery cells in the USN fleet boats consisted of an outer layer of hard rubber, then an impermeable membrane of soft rubber roughly the thickness of a toy balloon, then another layer of hard rubber. This was a very rugged construction that could flex with shock and not break. The membrane contained the acid and prevented leakage that could mix with sea water to create chlorine. This design was a tremendous improvement over the standard hard steel jar and was a key factor in the high survivability rate of the USN boats.

Originally Posted by Stormende

Also I read somewhere that an electric sub is harder to detect by passive sonar than a nuclear, is it due to the reactor makes more noise or what?

You are correct.

The prime source of radiated noise on a submarine is the propulsion plant. What drives a diesel-electric boat when it is submerged? Electric motors that are coupled to the propeller shafts. These motors are powered by storage batteries. Electric motors are virtually silent in operation, thus very little if any noise is radiated into the water.

What many people don't realize is that nuclear powered submarines are actually propelled by steam. The only thing the reactor does is provide an anaerobic (i.e. no air needed) heat source to superheat water in the primary loop. The primary loop provides heat to boil water in the secondary loop, generating steam. This steam then spins a turbine. This high speed turbine is connected to a set of reduction gears that in turn spin the propeller shaft. The water in both loops has to be moved through the system using pumps. So, in a nuclear plant you have three sources of noise: the pumps, the turbine, and the reduction gears. If not designed right this makes a heck of a lot of noise. The first American and Soviet nuke boats sounded like a freight trains barreling through the water. Eventually the twin practices of sound isolation mounting of machinery and extremely tight production standards largely mitigated this problem, but even today a well designed and tightly run diesel-electric boat can be just as quiet, and in some cases quieter, than a nuke boat when running on the battery. Of course, when running on the diesels it gets very noisy and this is its primary weakness.

Keep in mind that my description of a submarine nuclear plant is a very simplified one, but essentially accurate. There are several different designs out there. One eliminates the circulation pumps and moves the water around the loops using the natural heat convection of the water. Another substitutes the reduction gears for an electric generator which in turn supplies power to a motor on the shaft.

The USN has gotten so good at noise reduction that our modern boats are actually substantially quieter than the ambient noise in the surrounding ocean. That gives the word "silent" a whole new meaning!

[Stormende]

You are indeed a truly well of knowledge, thank you for the answers now I leave with a lil more knowledge.

Your thread is awesome.

[LukeFF]

Dave,

The WWII patrol reports mention the use of what is called a "bubble sextant" for navigation. Many commanders also mention how it was sometimes difficult to use this device. How did this new type of sextant differ from the "old" style sextant, and what made it so more difficult to use?