Submarine question

Factual Questions
1

As you all know, I prefer to be over the earth to being under the sea. (Although the idea of being under water is very cool as well.) So I know much less about submarines than I do other types of conveyances. Anyway…

It strikes me that submarines often operate in waters whose depths are not as great as the submarine’s length. IIRC, the Kursk was about 450 feet long and sank in about 325 feet of water.

Obviously, it would be impractical to provide enough reserve bouyancy in a submarine so that it could surface even when it was half-full of water. But would it be possible to have some sort of system such that the stern of a submarine might be floated while the bows rest on the ocean floor? Large inflatable floatation bags between the hulls, maybe? If that could be done, then survivors of an accident could just climb aft to safety.

Just wool-gathering here.

2

Actually this happen once to the

3

Per this site, the seabed was 108 meters (or about 355 feet) below sea level. Per this site, the Kursk was 155 meters (or about 508 feet) long. If I could remember my trigonometry better, I could tell you the angle that the crew would need to climb at in order to reach the stern (which would be bobbing at the surface with your idea). That’d be the first problem I could see: embedding ladders and horizontal transfers through the ship so that the crew could reach either the stern or bow.

Another problem I can think of would probably be the added weight of another buoyancy system. I’m probably wrong on this, but wouldn’t any added weight require more powerful engines? I could see the two of these taking up space that’s already at a premium on a submarine.

Other than those two things, I can’t really see a problem that would cause the system not to work. Of course, I expect a marine architect or a physicist to pop in here and bop me on the head for guessing. :slight_smile:

4

Rick? Rick?

Anyone see what happened to Rick?

5

Screwed that one up didn’t I?
This did happen once to the submarine S-5
Down by the bow, the survivors were able to blow the ballest tanks and rasie the stern enough to escape.
But subs were smaller then, and had more compartments.
IIRC correctly a Los Angeles class sub has only one watertight door. (door not exterior hatch) This means that there are only two compartments in the sub. When I took a tour of the USS Blueback the guide (an ex Navy chief) reffered to it as something that was installed to keep the moms happy. As in don’t worry mom, we have watertight doors.
No way are you going to be able to fit a bag big enough to lift that much dead weight.
It would be about as practical as putting a big parachute on top of a 747

6

I don’t think the problem is as much weight as it is space. There’s not a lot of room on a submarine. Even if they did have that recovery system, it would only work when it was operating at a depth less than that of the hull’s length. If deployed in deep water, the crew would have to climb straight up, and I don’t think they can do that without ladders or some kind of system to help out.

7

Los Angeles-class subs have two interior watertight doors, and there are three compartments. The second door is not normally accessed when the plant is steaming, as it leads to the Reactor Compartment. It’s possible to pass from the Operations Compartment to the Engine Room via the other watertight door that leads to a tunnel which passes around the Reactor Compartment.

Submariners used to remark that the escape system was installed for the benefit of “mommies and Senators” because of its limited utility. (I, personally, have reassessed this in light of the Kursk accident, for which a U.S. submarine-type escape system might have helped immensely.)

8

I stand corrected. My information was from the chief that was taking us through the Blueback. I noticed only one watertight door and asked about Los Angeles class boats. I screwed up his answer obviously.

9

If I might add a question to Johnny’s?

I have often wondered about the order “Rig for depth charges!”, in the older sub movies.

I mean, what’s to rig? Maybe I’m watching too much tv, but it seems to me that only nanoseconds pass between the order and the explosions.

Or is it a euphemism for “grab onto yo’ass!”?

Thanks for letting me hijack the thread!

Q

10

The “Rig for depth charge” order was SOP when there was a possibility of an attack; it was not reserved for when the depth charges were already on their way.

The crew’s response would be to close all watertight doors, ventilation ducts, etc. between compartments (IIRC, WWII U S subs had 7-8 main compartments), preventing flooding in one from affecting another. Because of the limited(!) size of the sub’s compartments, this could be accomplished in a matter of seconds.

11

Getting back to the OP, concerns about weight seem to have invalidated the “stand it on its nose” technique. But imagine for a moment that the sub assumed this attitude of its own accord. As the stern climbed skyward, would there come a point at which the reactor, oven, fryer, washing machine, and other heavy pieces of equipment tore away from their mounts and crashed down through the ship?

12

Johnny - aside from it being the most deadly weapon in the current U.S. arsenal, it is also one of the safest machines to be in. Coming from a long line of Submariners, I do not believe the current subs could ever be put in that situation, meaning I don’t think it could physically happen. There are so many devices on our subs that are designed to prevent it, it is considered by some, a complete improbability. Then again so was the titanic.
As per your OP, the pure amount of compressed air to “lift” a submarine weighing however many thousands of pounds to safety, is in my opinion impossible.

13

I´ve seen videos of submarines doing emergency surfacing (the maneuver has a specific name which I don´t remember right now) the sub goes up in an angle of 45 or more degrees, full speed, it actually jumps out of the water and almost half the hull sticks out of the surface, then makes the mother of all belly slams. If the washing machine holds to it´s bolts after that I don´t see why it wouldn´t do so in the case you describe.

14

Excellent Cite for this thread found here

I believe it was called the Archimedes Principle.

15

“… hold to **its[/bolts]…”

:smack:

16

ARRGHHHH!!!

MUST-HIT-PREVIEW

17

OK:

While that’s an interesting propsition, basically, the size (volume) and construction of current submarines prohibit that as a design feature.

The S-5 was a special case: She was in very shallow water (for a submarine). As aft tanks were blown, the angle of the boat allowed water to drain forwad, and eventually the stern poked clear of the water. This was a desperate and ultimately successful gamble. In any greater depth, they’d have been screwed.

As the angle of the hull increasese to rise through a greater depth of water, you lose lifting capacity in the MBTs. They have vents on the bottom, “Free-Flood” ports that allow the water to escape or enter. As the angle of the boat rises sufficiently, the volume of air in the tank, combined with the angle in the boat will expose those ports, and you’re no longer blowing air into the tanks, you’re blowing it out into the ocean. That physical construction limits the angle you can achieve.

The other limiting factors are how much water there is in the boat, and where is it? If it’s all at one end or the other, and not too much, you’ll be able to reach the extreme angle as limited by MBT geometry & air available. More water, or more evenly-distributed water, and your angle goes down. This is not the sort of issue one can predict with much assurance, so designing a boat to stand on its nose to act as its own rescue ladder isn’t really practicable.

Contrary-wise, if the S-5 had possesed more modern escape aids, the depth in which she sank would’ve made for a relatively easy escape to the surface. Certainly 300 feet is doable, though there will be injuries, and some may not make it in really good shape. Some may even die, but most would make it to the surface in acceptable condition. IIRC, the S-5 was in less than 200 feet. Much deeper than that, it becomes more problematic. Cold water also makes an emergency escape much more risky, and something you want to hold off on as long as is practical.

The Soviet Union went a different direction from Western submarines, in that many designs had escape capsules built-in, which could hold a significant portion of the crew. In some cases, the capsules were capable of holding the entire crew, and, IIRC, in some boats where the capsule couldn’t hold the entire crew, there were multiple capusles.

In the case of the Kusrsk, her escape capsule was severly damaged, and was in the flooded end of the boat, anyway.

18

I have to disagree with the premise of the post that "submarines often operate in waters whose depths are not as great as the submarine’s length. " Most submarines operate almost exclusivly where the bottom depth is in the thousands of feet. The U. S. Navy realizes that in the event of submarine acidents, there will be no hope of rescue due to this fact. The USS Scorpion (SSN-589), lies in 10,000 feet of water for example.

19

Regardless that U.S. submarines operate almost exclusively in areas of great depth, they still do often operate in more shallow waters. Even a boomer has to get close to land every so often (but I was thinking more about attack subs).

I’ll bet there are U.S. subs operating in the Persian Gulf. The Persian Gulf has a maximum depth of 90 metres and an average depth of 50 metres.

20

Ok, I spent 4 years stationed on the USS Bluefish SSN 675. I was an MM/1, (e-6 for you non-naval guys) I think I can help here somewhat.

Let’s talk about a sub’s design in general. The ballast tanks on a sub don’t really take on ballast in the original sense of the word. Meaning weights in the lower part of a ship to keep it upright in high seas and rough weather. The inner hull of a sub is encased in an outer hull, the outer hull forms the sides on the tanks. They are open at the bottom at all times. When the vents in the top are opened, the air is forced out by the weight of the sub and it submerges. To surface air is forced into the tanks from the top. This air comes from huge tanks of compressed air that are also located between the inner and outer hull. Actually, there is a lot of tankage and storage between the inner and outer hull.

Incidentally, all nuclear subs have a deisel generator for emergency and stand by use. The fuel for this is stored in an exterior tank that is also open to the sea at the bottom, remember, diesel is lighter than water. The fuel lines that feed the deisel come out of the top of the tank, unlike in your car. But back to the sub. Subs also have a ‘trim system’. A set of tanks that are used to balance the sub on a level keel front to back and side to side. This is an active process during watch change, drills and some high speed, high angle manuvers. And after every stores load or shipyard period. Remember as stores and supplies are loaded or consumed it will change the ‘trim’ of the boat. As a safety feature, no sub will completly submerge if the trim tanks are empty even if every ballast tank is flooded.

The problem with the ‘end up’ idea is this, as a matter of safety subs have a policy, (Captains Standing Orders) not to submerge unless there is at least 650 ft of water under the keel. That puts the sub in water too deep to reach the surface even if you could get it ‘end up’. And you can’t do that.

If you know any sub sailors then you are honered to know some of the bravest men in the service. Also, some of the wildest and craziest.