# What is the weakest point on a modern submarine? **URL:** \ **Category:** Factual Questions\ **Created:** [February 24, 2010, 4:54am UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236 "2010-02-24T04:54:08Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [March 1, 2010, 3:05pm UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/41 "2010-03-01T15:05:09Z")
> [@Magiver](#): > > 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). ---
**Author:** ![kevlaw](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kevlaw/32/2281_2.png) [@kevlaw](https://boards.straightdope.com/u/kevlaw)\ **Post date:** [March 1, 2010, 4:07pm UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/42 "2010-03-01T16:07:54Z")
> [@robby](#): > > 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. > [@robby](#): > > 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. ---
**Author:** ![mlees](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@mlees](https://boards.straightdope.com/u/mlees)\ **Post date:** [March 1, 2010, 9:14pm UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/43 "2010-03-01T21:14:36Z")
> [@ralph124c](#): > > 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. > [@wiki](#): > > 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. ---
**Author:** ![CapnScuttle](https://avatars.discourse-cdn.com/v4/letter/c/cdc98d/32.png) [@CapnScuttle](https://boards.straightdope.com/u/CapnScuttle)\ **Post date:** [May 19, 2015, 8:10pm UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/44 "2015-05-19T20:10:58Z")
> [@Claude\_Remains](#): > > 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_ ---
**Author:** ![Morgenstern](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@Morgenstern](https://boards.straightdope.com/u/Morgenstern)\ **Post date:** [May 19, 2015, 11:24pm UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/45 "2015-05-19T23:24:02Z")
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. ---
**Author:** ![Velocity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/velocity/32/18006_2.png) [@Velocity](https://boards.straightdope.com/u/Velocity)\ **Post date:** [May 19, 2015, 11:46pm UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/46 "2015-05-19T23:46:37Z")
> [@Morgenstern](#): > > 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. ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [May 20, 2015, 12:16am UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/47 "2015-05-20T00:16:02Z")
It is the thermal exhaust port. I have no idea why the engineers keep building in that vulnerability. ---
**Author:** ![drewder](https://avatars.discourse-cdn.com/v4/letter/d/57b2e6/32.png) [@drewder](https://boards.straightdope.com/u/drewder)\ **Post date:** [May 20, 2015, 12:46am UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/48 "2015-05-20T00:46:24Z")
> [@thirdname](#): > > 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. ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [May 20, 2015, 2:42am UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/49 "2015-05-20T02:42:06Z")
> [@CapnScuttle](#): > > 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. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [May 20, 2015, 4:10am UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/50 "2015-05-20T04:10:53Z")
> [@Saint\_Cad](#): > > That sounds like a major design flaw. Just proves every time you make something foolproof they go invent a better fool. ---
**Author:** ![AK84](https://avatars.discourse-cdn.com/v4/letter/a/85e7bf/32.png) [@AK84](https://boards.straightdope.com/u/AK84)\ **Post date:** [May 20, 2015, 4:50am UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/51 "2015-05-20T04:50:42Z")
> [@CapnScuttle](#): > > 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. ---
**Author:** ![Urbanredneck](https://avatars.discourse-cdn.com/v4/letter/u/ea5d25/32.png) [@Urbanredneck](https://boards.straightdope.com/u/Urbanredneck)\ **Post date:** [May 20, 2015, 5:14am UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/52 "2015-05-20T05:14:55Z")
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? ---
**Author:** ![Urbanredneck](https://avatars.discourse-cdn.com/v4/letter/u/ea5d25/32.png) [@Urbanredneck](https://boards.straightdope.com/u/Urbanredneck)\ **Post date:** [May 20, 2015, 5:18am UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/53 "2015-05-20T05:18:18Z")
> [@AK84](#): > > [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? ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [May 20, 2015, 6:07am UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/54 "2015-05-20T06:07:44Z")
> [@AK84](#): > > 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? ---
**Author:** ![AK84](https://avatars.discourse-cdn.com/v4/letter/a/85e7bf/32.png) [@AK84](https://boards.straightdope.com/u/AK84)\ **Post date:** [May 20, 2015, 6:37am UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/55 "2015-05-20T06:37:56Z")
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. ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [May 20, 2015, 2:29pm UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/56 "2015-05-20T14:29:40Z")
> [@Urbanredneck](#): > > 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. > [@Alessan](#): > > 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!” 😉 ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [May 20, 2015, 2:36pm UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/57 "2015-05-20T14:36:25Z")
nm ---
**Author:** ![Ranger\_Jeff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranger_jeff/32/2065_2.png) [@Ranger\_Jeff](https://boards.straightdope.com/u/Ranger_Jeff)\ **Post date:** [May 20, 2015, 4:40pm UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/58 "2015-05-20T16:40:18Z")
> [@Alessan](#): > > 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. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [May 20, 2015, 5:46pm UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/59 "2015-05-20T17:46:22Z")
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. ---
**Author:** ![Morgenstern](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@Morgenstern](https://boards.straightdope.com/u/Morgenstern)\ **Post date:** [May 20, 2015, 8:39pm UTC](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236/60 "2015-05-20T20:39:53Z")
Plus, the fewer people who know where a submarine is, the safer the mission of that sub. [Previous page](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236.md?page=2) [Next page](https://boards.straightdope.com/t/what-is-the-weakest-point-on-a-modern-submarine/530236.md?page=4)