What is the weakest point on a modern submarine?

I’m guessing that ballast tanks, prop shafts and torpedo tubes are all very problematic. What about the hull in general?

I think you will find that where the hull has something pass through it is the weak point.

No kidding? wow. Dang, before I go I still am wondering about the point that is THE WEAKEST.

Usually, when something tragic occurs, an official military investigation concludes the weakest point was the captain.

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, I’m fairly certain the windows are the weakest point.

By contrast - on a submarine like this, I’m fairly certain the weakest point is classified.

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.

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.

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?

High pressure shaft seals. Here’s a paper if you wish to purchase it.

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?

NCIS leads me to believe that the weakest point is a sonar operator with strong environmentalist leanings.

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.

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 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, the loss of which was the impetus for the SUBSAFE program).

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.

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…and thought I’d give a link to it.

Hope you stop by.

Need answer fast?

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?

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.

You use a podded system like this 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.