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View Full Version : What is the weakest point on a modern submarine?


Claude Remains
02-23-2010, 10:54 PM
I'm guessing that ballast tanks, prop shafts and torpedo tubes are all very problematic. What about the hull in general?

Rick
02-23-2010, 11:42 PM
I think you will find that where the hull has something pass through it is the weak point.

Claude Remains
02-23-2010, 11:55 PM
No kidding? wow. Dang, before I go I still am wondering about the point that is THE WEAKEST.

Dereknocue67
02-24-2010, 03:19 AM
Usually, when something tragic occurs, an official military investigation concludes the weakest point was the captain.

Kiber
02-24-2010, 07:56 AM
Possibly, it would help if you define what type of modern submarine you are talking about - as the weakest point will be different.

For example - on a submarine like this (http://www.lamorsubsea.com/files/sm300.jpg), I'm fairly certain the windows are the weakest point.

By contrast - on a submarine like this (http://www.armybase.us/wp-content/uploads/2009/05/australian-submarine-hmas-rankin-hull-6-and-us-navy-attack-submarine-uss-key-west-ssn-722.jpg), I'm fairly certain the weakest point is classified.

Xema
02-24-2010, 08:18 AM
I'm guessing that ballast tanks, prop shafts and torpedo tubes are all very problematic.
Is there any significant history of serious failures of these on modern subs? I see no real reason why it would be especially challenging to design these to be as reliable as the rest of the sub.

Icerigger
02-24-2010, 08:39 AM
BTW on subs and ships as well how do they seal a spinning prop shaft from the sea. A surface ship can pump the leaking water out but a sub under high water pressure I would think any leak of water would be a disaster.

smiling bandit
02-24-2010, 08:44 AM
No kidding? wow. Dang, before I go I still am wondering about the point that is THE WEAKEST.

Rick was being pretty stupid there, for some reason. Regardless, if we assume you're talking about a modern naval submarine, there's a real question of "Weak to what?" Are we talking something hitting it? Water pressure?

beowulff
02-24-2010, 08:49 AM
BTW on subs and ships as well how do they seal a spinning prop shaft from the sea. A surface ship can pump the leaking water out but a sub under high water pressure I would think any leak of water would be a disaster.

High pressure shaft seals. Here's (http://www.emeraldinsight.com/10.1108/eb053372) a paper if you wish to purchase it.

Bijou Drains
02-24-2010, 08:49 AM
How deep US subs can go is officially secret but I believe they say it's below 800 feet. From what I have read once they go too deep the hull implodes.

Lumpy
02-24-2010, 08:55 AM
How deep US subs can go is officially secret but I believe they say it's below 800 feet. From what I have read once they go too deep the hull implodes.Can the limit be guesstimated from how thick a cylindrical steel hull could be before it couldn't maintain positive buoyancy?

KneadToKnow
02-24-2010, 08:57 AM
NCIS leads me to believe that the weakest point is a sonar operator with strong environmentalist leanings.

Bijou Drains
02-24-2010, 08:58 AM
I would imagine people can make a good guess how deep the subs can go if they know how it's built. I don't know if the specs of the sub are secret as well, it's logical they are also secret.

robby
02-24-2010, 09:09 AM
By contrast - on a submarine like this (http://www.armybase.us/wp-content/uploads/2009/05/australian-submarine-hmas-rankin-hull-6-and-us-navy-attack-submarine-uss-key-west-ssn-722.jpg), I'm fairly certain the weakest point is classified.Exactly. You're not going to get any more detail than a generality like Rick posted. (And I don't think his answer was stupid.)

With respect to Rick's comment regarding hull penetrations, one of the principles of the U.S. Navy's SUBSAFE (http://en.wikipedia.org/wiki/SUBSAFE) program was a change in design philosophy to minimize the number of hull penetrations. Pre-SUBSAFE submarines had hundreds of hull penetrations, just like most surface ships do even today. Post-SUBSAFE submarines were designed with far fewer (but larger) hull penetrations that serve multiple purposes. In addition, the hull penetrations all have quick-closing emergency closures in the event of a pipe rupture inside the submarine (which is what sank the USS Thresher (http://en.wikipedia.org/wiki/USS_Thresher_(SSN-593)), the loss of which was the impetus for the SUBSAFE program).

BTW on subs and ships as well how do they seal a spinning prop shaft from the sea. A surface ship can pump the leaking water out but a sub under high water pressure I would think any leak of water would be a disaster.You have shaft seals. Some nominal amount of water always does leak in, particularly at depth, but submarines have bilge pumps and drain pumps just like surface ships.

Frank apisa
02-24-2010, 09:29 AM
Haven't got the slightest idea of the correct answer to your question, Claude, but I just mentioned this thread in a thread of my own (http://boards.straightdope.com/sdmb/showthread.php?p=12155979#post12155979)...and thought I'd give a link to it.

Hope you stop by.

Smeghead
02-24-2010, 10:49 AM
Need answer fast?

Shamozzle
02-25-2010, 01:45 AM
This might be a dumb question, but wouldn't it make sense to power the prop electrically while isolating the motor-prop unit outside the hull, there-by not penetrating the hull with the shaft?

Xema
02-25-2010, 07:48 AM
wouldn't it make sense to power the prop electrically while isolating the motor-prop unit outside the hull
Wouldn't this require either a motor that operates while surrounded by salt water, or one that must be pressurized (with air, or perhaps nitrogen) to match the water pressure?

Kiber
02-25-2010, 08:04 AM
Wouldn't this require either a motor that operates while surrounded by salt water, or one that must be pressurized (with air, or perhaps nitrogen) to match the water pressure?

Plus - it would leave the only means of propulsion outside the pressure hall, making it pretty much impossible to maintain. And of course, it would still require a hole in the hull for power and control cables. So - several downsides, but not really any upside.

yendis
02-25-2010, 08:05 AM
This might be a dumb question, but wouldn't it make sense to power the prop electrically while isolating the motor-prop unit outside the hull, there-by not penetrating the hull with the shaft?

You use a podded system like this (http://en.wikipedia.org/wiki/Azipod) where you have an electric motor in an external pod. Then you would only need to get electrical power to the motor.

The problem with this system is that even the smallest amount of damage will completely disable the sub since repairing the motor while underwater would be difficult if not completely impossible.

robby
02-25-2010, 08:13 AM
You use a podded system like this (http://en.wikipedia.org/wiki/Azipod) where you have an electric motor in an external pod. Then you would only need to get electrical power to the motor.

The problem with this system is that even the smallest amount of damage will completely disable the sub since repairing the motor while underwater would be difficult if not completely impossible.Many U.S. submarines actually do have a small motorized, retractable Secondary Propulsion Motor (SPM) colloquially referred to as the "outboard." It is lowered into position and and rotated in different directions. It is used for close maneuvering situations (like docking).

mlees
02-25-2010, 09:22 AM
USS Scorpion, an older Skipjack class "attack" sub, sank below crush depth in 1968.


The operations compartment itself was largely obliterated by sea pressure and the engine room had telescoped 50 ft (15 m) forward into the hull by collapse pressure, when the cone-to-cylinder transition junction failed between the auxiliary machine space and the engine room.


http://en.wikipedia.org/wiki/USS_Scorpion_(SSN-589)

Shamozzle
02-26-2010, 12:23 AM
Wouldn't this require either a motor that operates while surrounded by salt water, or one that must be pressurized (with air, or perhaps nitrogen) to match the water pressure?

Plus - it would leave the only means of propulsion outside the pressure hall, making it pretty much impossible to maintain. And of course, it would still require a hole in the hull for power and control cables. So - several downsides, but not really any upside.

Hmmm, yes maintenance would be a problem.

But besides that, I was thinking that the unit could be in its own sealed hull. Granted, the shaft would still need to be sealed, but a breach would only compromise the isolated hull and not the main hull.

As for power and control cables, would it be easier to seal these than a dynamic shaft? And couldn't power and control be transmitted by induction through the hull, precluding the need to penetrate the hull? I'm reaching here, I know, but its just a thought.

But yea, the lack of maintenance access would be the deal killer.

Xema
02-26-2010, 08:02 AM
I was thinking that the unit could be in its own sealed hull. Granted, the shaft would still need to be sealed, but a breach would only compromise the isolated hull and not the main hull.
A breach would almost certainly render the propulsion unit inoperable. While not as rapidly fatal as a breach to the main hull, this would be an extremely serious emergency that could threaten the sub's survival.

couldn't power and control be transmitted by induction through the hull, precluding the need to penetrate the hull?
Doing this efficiently through a thick metal hull looks to be extremely challenging.

Not to say that sealing a shaft against 80 atmospheres of pressure is trivial. But it has been done, and made reliable.

CutterJohn
02-26-2010, 08:32 AM
The shaft isn't really hard to seal. About the only thing that would absolutely prevent you from stopping the water from coming in would be the entire shaft falling out. If that happens, you've got much, much bigger problems.

Speaking from intimate experience(I once spent a very long day scraping, cleaning, polishing, and painting one of the shaft seals on the enterprise)..

Pretty much there are 3 main systems keeping water out of the people space. For normal operations, there is a plain old(though very large) mechanical seal. If that fails, there is an even plainer old ring of packing, which can be tightened down to form a seal on the shaft.

If both of those fail, there is an inflatable bladder that seals the shaft. However, the shaft cannot be rotated if its inflated.

If worse comes to worse, and all of those fail, you would simply seal the hatch to the shaft room. Submarines may not have this last option, however. I've only been on one, and it didn't.. the shaft seal was in the engine room.

robby
02-26-2010, 08:50 AM
...If worse comes to worse, and all of those fail, you would simply seal the hatch to the shaft room. Submarines may not have this last option, however. I've only been on one, and it didn't.. the shaft seal was in the engine room.Right. Can't do that on a submarine, because the shaft seals are in the engine room, which is one of just three watertight compartments on a Los Angeles-class submarine, for example (and the largest, BTW). If all of the shaft seals failed and you had uncontrolled flooding in the engine room, the sub is toast.

kevlaw
02-26-2010, 03:36 PM
If worse comes to worse, and all of those fail, you would simply seal the hatch to the shaft room. Submarines may not have this last option, however. I've only been on one, and it didn't.. the shaft seal was in the engine room.

In my submarine, the shaft seal was, in fact, in a separate compartment from the engine room and, in fact, we did once have a leak and sealed just that compartment (with someone in it!).

Trivia: We did a Maximum Deep Dive Test before every patrol and someone would always tie a piece of string across the hull at max depth to impress the newbies when it broke as the sub went back to the surface.

Our max safe dive was 750ft but I believe modern subs can go 3x that. Our boat used to creak like hell at that depth. Pretty scary the first time.

ralph124c
02-26-2010, 04:04 PM
In my submarine, the shaft seal was, in fact, in a separate compartment from the engine room and, in fact, we did once have a leak and sealed just that compartment (with someone in it!).

Trivia: We did a Maximum Deep Dive Test before every patrol and someone would always tie a piece of string across the hull at max depth to impress the newbies when it broke as the sub went back to the surface.

Our max safe dive was 750ft but I believe modern subs can go 3x that. Our boat used to creak like hell at that depth. Pretty scary the first time.

In the movie "DAS BOOT"-the German U-Boat is portrayed in a very deep dive (the depth gauge reads in the "red" region). Finally, they hit the bottom-and the hull starts making all these scarey groaning noises (as the hull contracts under the great water pressure). Suddenly, there comes a series of sounds like pistol shots-and the chief of the boat explains that the sounds are of the rivets in the hull sheaing off, as the hull plates contract.
is this true? Seems like the next thing would be a wall of water flooding in!:eek:

kevlaw
02-26-2010, 04:42 PM
In the movie "DAS BOOT"-the German U-Boat is portrayed in a very deep dive (the depth gauge reads in the "red" region). Finally, they hit the bottom-and the hull starts making all these scarey groaning noises (as the hull contracts under the great water pressure). Suddenly, there comes a series of sounds like pistol shots-and the chief of the boat explains that the sounds are of the rivets in the hull sheaing off, as the hull plates contract.
is this true? Seems like the next thing would be a wall of water flooding in!:eek:

I can testify to the scary groaning but I never witnessed rivets popping :)

633squadron
02-27-2010, 06:40 PM
I'm guessing that ballast tanks, prop shafts and torpedo tubes are all very problematic. What about the hull in general?

The screen doors.

Kobal2
02-27-2010, 07:26 PM
In the movie "DAS BOOT"-the German U-Boat is portrayed in a very deep dive (the depth gauge reads in the "red" region). Finally, they hit the bottom-and the hull starts making all these scarey groaning noises (as the hull contracts under the great water pressure). Suddenly, there comes a series of sounds like pistol shots-and the chief of the boat explains that the sounds are of the rivets in the hull sheaing off, as the hull plates contract.
is this true? Seems like the next thing would be a wall of water flooding in!:eek:

Nope, not true. Like the exploding computers of the Entreprise's bridge in Star Trek, it's for effect on the viewer, added drama.
On a real boat, even a single rivet failing or valve/steam duct exploding would be a serious concern, esp. at 150m depth. Nevermind a whole lot of them at once. As you surmise, it means the end will come very suddenly, and very, very soon.

The groaning is real however (as has already been said), and it happened during any rapid change of depth, not just when you went too far down. It's just the sound of the hull and bulkheads contracting/de-contracting in reaction to rapid pressure changes.

Trivia: We did a Maximum Deep Dive Test before every patrol and someone would always tie a piece of string across the hull at max depth to impress the newbies when it broke as the sub went back to the surface.

They did it the other way round in Up Periscope : the engineer tied a taut string to the walls of the engine room, to impress the newbies when it started sagging at the old boat went deeper and deeper.

robby
02-27-2010, 09:23 PM
In my submarine, the shaft seal was, in fact, in a separate compartment from the engine room and, in fact, we did once have a leak and sealed just that compartment (with someone in it!).Out of curiosity, what submarine (or class of submarine) were you on?

Trivia: We did a Maximum Deep Dive Test before every patrol and someone would always tie a piece of string across the hull at max depth to impress the newbies when it broke as the sub went back to the surface.

Our max safe dive was 750ft but I believe modern subs can go 3x that. Our boat used to creak like hell at that depth. Pretty scary the first time.

The groaning is real however (as has already been said), and it happened during any rapid change of depth, not just when you went too far down. It's just the sound of the hull and bulkheads contracting/de-contracting in reaction to rapid pressure changes.Even on a relatively modern submarine (like the Los Angeles-class I served on) the hull groans when making dramatic depth changes. Pretty unnerving the first time you hear it.

We also used to do the string trick.

Magiver
02-27-2010, 11:14 PM
The question needs to be clarified but as a point of impact I think the horizontal plane on the conning tower would be the weakest point of contact. Hit the end of one of those and you're going to leverage it against the tower.

thirdname
02-27-2010, 11:34 PM
Can anyone tell me where the armor is thinnest on an M1A2 Abrams tank? Also, what is the frequency of the shield modulation on the USS Enterprise?

Shamozzle
02-28-2010, 03:45 AM
Can anyone tell me where the armor is thinnest on an M1A2 Abrams tank? Also, what is the frequency of the shield modulation on the USS Enterprise?12.3 Megafonzies

kevlaw
02-28-2010, 02:54 PM
Out of curiosity, what submarine (or class of submarine) were you on?

HMS Revenge. A Polaris (SSBN) submarine.

Nice cutaway diagram of HMS Resolution (same class) at wikipedia. (http://upload.wikimedia.org/wikipedia/commons/b/bc/HMS_resolution_model.jpg)

It was only 25 years ago and it drives me mad that I can't remember the names of the compartments and that I can't find any annotated diagrams on the intertubes.

I want to say that the last compartment was the shaft room (but I might be misremembering). In another thread about submarines I claimed to work in the Sonar Instrument Space but I suspect that I misremembered that too. That's what it was called on my previous (surface) ship. Any other Polaris submariners around who can help me?

It's funny. I can remember exactly which compartment is which because one of the tests before you earned your dolphins was to go blindfolded from stern to stem (and point out all the fire extinguishers/breathing apparatus along the way) but I can't remember the names. I suck.

ralph124c
02-28-2010, 03:47 PM
I ask because it seems that a diesel-electric sub can settle down on the bottom, and be totally noiseless (unless a crew member drops a wrench).
Recently, I read about an advanced Swedish D-E boat (HMS Gotland) that gave the US Navy fits-it was so quiet that it couldn't be tracked.
So, does the USN have anything to fear from non-nuclear subs?

Lumpy
02-28-2010, 05:36 PM
I ask because it seems that a diesel-electric sub can settle down on the bottom, and be totally noiseless (unless a crew member drops a wrench).
Recently, I read about an advanced Swedish D-E boat (HMS Gotland) that gave the US Navy fits-it was so quiet that it couldn't be tracked.
So, does the USN have anything to fear from non-nuclear subs?My 2˘:
Yes and no. Modern diesel-electric subs are much better than anything available in WW2, and they're as capable as nuclear subs in anything but powerplant. That is a big "but" however. Diesel-electrics don't have the global range of nuclear, nor the ability to stay submerged indefinitely. As a secondary point, if they aren't nuclear powered they probably aren't going to be nuclear armed either. A carrier task force expecting trouble from below is going to be screened by robust anti-submarine defenses, including one or more hunter-killer subs, anti-sub destroyers and frigates, and air reconnaissance including helicopters deploying sonar buoys.

In short, diesel-electrics can be a cost-effective option for a navy of modest means and worth having, but they're still minor league.

Pushkin
02-28-2010, 06:05 PM
NCIS leads me to believe that the weakest point is a sonar operator with strong environmentalist leanings.

Voyage to the Bottom of the Sea suggests large humanoid monsters that pop up from behind a rock from time to time.

robby
03-01-2010, 08:50 AM
In my submarine, the shaft seal was, in fact, in a separate compartment from the engine room and, in fact, we did once have a leak and sealed just that compartment (with someone in it!).On re-reading, I see that you actually sealed a compartment with a leak with someone in it? Do you mean to say that they actually drowned? :eek:

(I remember a scene from the 1978 film Gray Lady Down (http://www.imdb.com/title/tt0077629/), that I saw in the theater when I was 10 years old, in which a sailor was sealed in a flooding compartment. It completely freaked me out, which makes it all the more amazing that I went into the submarine service myself.)

It's funny. I can remember exactly which compartment is which because one of the tests before you earned your dolphins was to go blindfolded from stern to stem (and point out all the fire extinguishers/breathing apparatus along the way)...We had to do the the much the same thing in the U.S. submarine force.

To be more precise, we had to wear an EAB (Emergency Air Breathing) device that hooked into various ports throughout the ship. Wearing a piece of black fabric over the faceplate (to simulate smoke), we had 3 minutes or so to make it from the torpedo room up forward, to shaft alley in the engineroom lower level back aft. You had to wear the mask the whole way, stopping to plug into air jacks as needed. Between stops to plug in and get a breath, you had to hold your breath. When you went through normally closed hatches, you also had to properly shut them behind you.

robby
03-01-2010, 09:05 AM
The question needs to be clarified but as a point of impact I think the horizontal plane on the conning tower would be the weakest point of contact. Hit the end of one of those and you're going to leverage it against the tower.I don't that the planes are much of an issue. If you hit them hard enough, they will just bend or break off. (That's even if the submarine has fairwater planes on the sail. Most new submarines have eliminated the fairwater planes in favor of bow planes up forward on the hull.) Heck, if you hit the sail (formerly referred to as the conning tower), it will just bend, like what happened to the USS Hartford last year (http://en.wikipedia.org/wiki/USS_Hartford_and_USS_New_Orleans_collision). The Hartford's sail was extensively damaged, and noticeably askew in pictures taken after the collision. (The sail was no longer perpendicular to the hull, but noticeably bent over.)

In any event, the sail is outside of the pressure hull (though there are numerous penetrations for periscopes, masts, and antennas).

kevlaw
03-01-2010, 10:07 AM
On re-reading, I see that you actually sealed a compartment with a leak with someone in it? Do you mean to say that they actually drowned? :eek:


He managed to repair the leak and survived. He was a bit of a hero after that.


To be more precise, we had to wear an EAB (Emergency Air Breathing) device that hooked into various ports throughout the ship. Wearing a piece of black fabric over the faceplate (to simulate smoke), we had 3 minutes or so to make it from the torpedo room up forward, to shaft alley in the engineroom lower level back aft. You had to wear the mask the whole way, stopping to plug into air jacks as needed. Between stops to plug in and get a breath, you had to hold your breath. When you went through normally closed hatches, you also had to properly shut them behind you.

Yeah - same deal for us.

mlees
03-01-2010, 03:14 PM
I ask because it seems that a diesel-electric sub can settle down on the bottom, and be totally noiseless (unless a crew member drops a wrench).
Recently, I read about an advanced Swedish D-E boat (HMS Gotland) that gave the US Navy fits-it was so quiet that it couldn't be tracked.
So, does the USN have anything to fear from non-nuclear subs?

Yes, IMO, they have their uses.

While the greater endurance and performance from nuclear reactors makes nuclear submarines better for long-distance missions or the protection of a carrier battle group, their reactor cooling pumps have traditionally made them noisier, and thus easier to detect, than conventional diesel-electric submarines. Diesel-electrics have continued to be produced by both nuclear and non-nuclear powers as they lack this limitation, except when required to run the diesel engine to recharge the ship’s battery. Recent technological advances in sound damping, noise isolation, and cancellation have made nuclear subs quieter and substantially eroded this advantage. Though far less capable regarding speed and weapons payload, conventional submarines are also cheaper to build. The introduction of air-independent propulsion boats, conventional diesel-electric submarines with some kind of auxiliary air-independent electricity generator, have led to increased sales of such types of submarines.

They have somewhat limited patrol range based on feul tankage. I dunno about underwater speed limitations (battery versus reactor power).

The USN, with worldwide commitments and limited manpower availability (all volunteer military), chooses to use nuclear subs only.

Within their limitations, a diesel sub is still a dangerous weapon sysytem.

CapnScuttle
05-19-2015, 03:10 PM
I'm guessing that ballast tanks, prop shafts and torpedo tubes are all very problematic. What about the hull in general?

This thread is probably long dead, but never mind. Stumbled across it and felt I may have something useful to offer.

Whenever a weak point is found, designers try and put in a fix.

E.g. if a US or UK submarine accidentally bumps into an iceberg (especially a black one with a red star painted on, that was playing 'chicken') there is a possibility that the propeller of one may get bust (one Brit sub is supposed to have found bits of bronze propeller in its casing on getting home!). So a secondary motor - 'outboard (US) or 'eggbeater' (UK) is fitted.

I believe one electrical fitter was trying to remove the slip rings at the top of the eggbeater mounting column one day, so he took off the big nut that was in the way. He was rewarded with a 13" wide fountain, as the motor dropped out. Someone slammed the Motor Room door on him and turned on the salvage air blow to pressurize the compartment, and left the silly bugger in the compartment half full of water until divers could cover the hole, and they could blow out the water, release the pressure and let him out. All good fun. I don't suppose a 24" prop shaft could 'fall out', and you'd need to be very quick slamming the motor room door, but in principle that is how you'd deal with it. Mind you, if not on the surface, you'd be sunk before you got the ballast tanks blown and enough air in the motor room to stop you going down! British subs had a lot of subdivision, so in theory collision damage to one end compartment would limit the flooding to recoverable amounts.


Shaft seals wear out, so they had 2 of standard ones, and a super-duper different sort, and an inflatable one for last-ditch (UK Polaris boats). Hull openings are minimised, as any hole in the pressure vessel is a source of increased stress, and hull valves are made VERY strong. Hopefully all the stick-out bendy bits (fin, planes, periscopes etc. are made so that they will bend and collapse before affecting the pressure hull, if hit.

So the question is impossible to answer - the problems and solutions are always changing and developing, as designers strive to sort out the worst.

Looking back on driving the reactor of an SSBN, nearly 40 years ago, I am struck by how accurate the Simpsons portrayal of nuclear safety is. (I have a nice little nodding bird in front of me as I write this!) I made a tremendous contribution to nuclear safety, 35 years ago, by resigning to gett jobs at which I was competent, or at least harmless!) So the manpower aspect is very important - in the UK we got paid about 30% extra, not for danger money (What could possibly go wrong?) but for being responsible and 'fessing up ' at once if any mistake was made - no witch hunts, just get it put right! There are too many ways of making simple - but potentially lethal - mistakes. The 'fix' was to have very, very thorough training and selection. (I obviously slipped through.)

Re. the string trick, we used string across the dining hall, tight up top, with a key hanging in the middle - it sagged to the floor as we went down. Another aspect of this was to make sure you were not in a cabin with the door shut on diving! (You might have to wait 6 weeks to open it again!)

Subs are designed not to collapse until 2 or 3 times their maximum permitted diving depth (which is reassuring) but most accidents happen because of combinations of many, little errors. In training we were told how a submarine had sunk alongside at HMS DOLPHIN (home of UK subs) one evening, with 3 men onboard. They identified about 13 different mistakes that led to it - hoses and wires through hatches, filling tanks unsupervised, doors left open when they should be closed, draught marks not checked frequently enough - all sorts of little, everyday faults that just happened to combine. (All three guys ran up the boat trying to shut doors behind them and finally got to the escape compartment at the front and got that door shut. They were saved by the trot sentry (quartermaster) who stood with his foot over the (obstructed) engine room hatch until the water was up his nose, to slow down the rate of flooding. All 3 were floated out alive 16 hours later, I believe.)

Nukes can sit on the mud - HMS REPULSE demonstrated that very successfully when CND protesters delayed its launch by half an hour and there wasn't time to get it out of the muddy channel! Vickers Sub Association have the embarrassing picture on line! But normally they don't dare, because the reactor is like a coal fire - it goes on burning after you stop feeding it; so you MUST always have good cooling water supply, and you don't mess about risking blocking a hull opening by sitting in mud. Diesel subs are therefore better for sneaky inshore silent stuff, while nukes are kept for the open water - which is best, a bike or a car? Depends where you want to use it!

Personally, I always thought the weakest point of a nuke was the single prop - too many ropes, nets, icebergs, rocky bits etc. about. Coming back from Murmansk harbour or the Caspian Sea, or wherever it was we lurked, at 2 knots on the eggbeater, never struck me as a viable proposition.

Ballast tanks were pretty robust - mostly outside the boat, and if one fell off - well, we had a dozen.

Hope that helps

Capn. Scuttle

*I wouldn't like to be in a submarine with me onboard*

Morgenstern
05-19-2015, 06:24 PM
Nice reply, Welcome to the board Capt.

I don't known why the US has not pursued diesel subs for some missions. Seems they would have some real advantages.

Velocity
05-19-2015, 06:46 PM
Nice reply, Welcome to the board Capt.

I don't known why the US has not pursued diesel subs for some missions. Seems they would have some real advantages.

The Navy wants endurance, range and performance.

Shagnasty
05-19-2015, 07:16 PM
It is the thermal exhaust port. I have no idea why the engineers keep building in that vulnerability.

drewder
05-19-2015, 07:46 PM
Can anyone tell me where the armor is thinnest on an M1A2 Abrams tank? Also, what is the frequency of the shield modulation on the USS Enterprise?

I can't say for certain but usually the least armor is on the bottom of the tank.

Saint Cad
05-19-2015, 09:42 PM
I believe one electrical fitter was trying to remove the slip rings at the top of the eggbeater mounting column one day, so he took off the big nut that was in the way. He was rewarded with a 13" wide fountain, as the motor dropped out.

That sounds like a major design flaw.

Rick
05-19-2015, 11:10 PM
That sounds like a major design flaw.

Just proves every time you make something foolproof they go invent a better fool.

AK84
05-19-2015, 11:50 PM
T

Nukes can sit on the mud - HMS REPULSE demonstrated that very successfully when CND protesters delayed its launch by half an hour and there wasn't time to get it out of the muddy channel! Vickers Sub Association have the embarrassing picture on line!

This would be the (http://www.rnsubs.co.uk/Boats/BoatDB2/img/repulse2.jpg) picture in question?

Coming back from Murmansk harbour or the Caspian Sea, or wherever it was we lurked, at 2 knots on the eggbeater, never struck me as a viable proposition.


British subs can go on the 1000 KM overland route to the Caspian Sea (http://en.wikipedia.org/wiki/Caspian_Sea)? Must have been made for quite a sight in downtown Tehran seeing HMS Trafalger crawling to the Caspian.

Urbanredneck
05-20-2015, 12:14 AM
I saw a video of a submarine smashing upwards thru polar ice. Then the crew got off and walked on the ice. Can they all do that or just certain ones?

Urbanredneck
05-20-2015, 12:18 AM
This would be the (http://www.rnsubs.co.uk/Boats/BoatDB2/img/repulse2.jpg) picture in question?

British subs can go on the 1000 KM overland route to the Caspian Sea (http://en.wikipedia.org/wiki/Caspian_Sea)? Must have been made for quite a sight in downtown Tehran seeing HMS Trafalger crawling to the Caspian.How did a submarine get there? By train?

Alessan
05-20-2015, 01:07 AM
British subs can go on the 1000 KM overland route to the Caspian Sea (http://en.wikipedia.org/wiki/Caspian_Sea)? Must have been made for quite a sight in downtown Tehran seeing HMS Trafalger crawling to the Caspian.

Which begs the question - do non-bridge submarine crew ever actually know where the hell they are?

AK84
05-20-2015, 01:37 AM
AFAIK they do not unless they need to know or its obvious like say a port call. On board missile subs I think only the skipper and a few others know.

robby
05-20-2015, 09:29 AM
I saw a video of a submarine smashing upwards thru polar ice. Then the crew got off and walked on the ice. Can they all do that or just certain ones?The short answer is "just certain ones."

To break through the ice, a submarine needs a hardened sail (formerly known as a "conning tower"), some type of controlled deballasting system (because you don't actually "smash" through the ice [which would break things]; instead you more or less push up through the ice in a controlled fashion); and either sail-mounted fairwater planes that can be rotated to vertical, or bow planes.

I was part of the crew of the first Los Angeles-class submarine to break through the polar ice 20+ years ago.

Which begs the question - do non-bridge submarine crew ever actually know where the hell they are?The standard tongue-in-cheek answer to that question (when posed by engineering personnel on watch in the engineroom) was, "Don't worry about where we are. Shut up and push!" ;)

LSLGuy
05-20-2015, 09:36 AM
nm

Ranger Jeff
05-20-2015, 11:40 AM
Which begs the question - do non-bridge submarine crew ever actually know where the hell they are?

Would knowing their lat/long really tell them much? The view from aboard the boat wouldn't change.

LSLGuy
05-20-2015, 12:46 PM
Them knowing wouldn't improve their life much at the moment.

Them not knowing improves security over the course of multiple patrols a bunch by reducing the number of data points that might leak into more public knowledge.

Hence the policy to keep navigation stuff pretty close-hold.

Morgenstern
05-20-2015, 03:39 PM
Plus, the fewer people who know where a submarine is, the safer the mission of that sub.

lisiate
05-20-2015, 03:55 PM
If this long list of problems (https://wikileaks.org/trident-safety/)from an ex RN submariner is true the British submarines seem to be a disaster waiting to happen. It's doubtful his sub could even have launched it's missiles if it had to:

Final tests - At the end of a patrol tests are done to see if the weapons system could have performed a successful launch. These tests let us know if we really were providing the UKs strategic nuclear deterrent / CASD. It had reached the end of my three month patrol. It was time to do WP 186 missile compensation test. The test was carried out 3 times and it failed, 3 times. Basically the test showed that the missile compensation system wouldn't have compensated for the changes in weight of the submarine during missile launches. Which means the missiles would've been launched on an unstable platform, if they decided to launch. Another test was the Battle Readiness Test (BRT) which proves that the muzzle hatches could've opened whilst on patrol; if they needed to launch, they could've launched. The BRT was cancelled due to the main hydraulic system containing mostly sea water instead of actual hydraulic oil. Basically they're endangering the public and spending Billions upon Billions of tax payers money for a system so broken it can't even do the tests that prove it works.

One shudders to think what the Russian boats are like...

pdunderhill
05-20-2015, 04:00 PM
Well done Capt. for resurrecting this particular Zombie.

As an aside the story of U864's sinking amazes me http://en.wikipedia.org/wiki/German_submarine_U-864

It is the only instance in the history of naval warfare where one submarine intentionally sank another while both were submerged. Nothing in the Pacific campaign and nothing since.

To the OP's question, the weakest point, as with most complex machinery, is the operator. human error.

Peter