Can a sub really sink itself beyond recovering by opening a tube?

At school I spent two weeks on an ocean liner. They told us that as long as the fire doors were closed, she could stand to have quite a substantial amount of water on board before listing and going down. I would suppose a sub. is the same.

I qualified aboard SSBN656 (USS George Washington Carver) in 1980, and subsequently trained aboard another boomer as diving officer, and I disagree (and heartily, I'm afraid). Merely moving a dozen or so decent-sized men to the forward room will alter trim perceptibly to where the diving officer will feel compelled to pump water aft, and on a submarine more than twice the likely size of the one in the movie. The forward room is a large space and will hold a lot of water, and the rate of ingress of water through an opening 21 inches in diameter at sea pressure will fill it entirely in as little as a minute, tops, depending upon your depth. This will add far greater weight to that end of the boat than a dozen men will, and in a short period of time. Because all the water is staying up at the forward end of the boat, you can expect to develop a significant down-angle that the planesmen cannot hold pretty promptly. Indeed, we used to practice this type of casualty on the dive training simulator at the former FBM Training Center in Charleston, South Carolina, and that is just what happened. In real life a hole that size while submerged is a nightmare casualty that will get you every time if you do not respond correctly and promptly, if then.

Consequently, I never thought that this sequence was especially "Hollywood" at all. In the aforementioned simulator it looked a lot like the way it did in the movie. To begin with, in the movie the captain orders the blowing of all main ballast tanks as soon as the casualty is reported. This was obviously inspired by an extremely competent technical advisor. From my experience with the simulator, it is what saved the ship. Waiting to do that until other measures had been tried and failed in the simulator resulted in the loss of a boat at least twice this one's presumed size. This is because the forward momentum the boat had prior to the casualty is now directed downward as well as forward, because of the trim problem, and the fact that the boat is taking on water faster than it can expel it by blowing main ballast means it is still getting heavier by the minute. All of this is dragging the boat ever deeper by the second.

Even once the flooding is contained (in this case by getting the tube outer door shut), so that you are now shedding weight as the blow of main ballast continues, the boat has tremendous downward momentum that must be reversed before it gets so deep that it reaches design depth, at which point it is assumed that you'll start having a lot more flooding from blown packings, gaskets, fityings, and the like. Worse still, if you plunge past design depth quickly enough, you could have a hull rupture and implosion such as appears to have happened to SSN589, the USS Scorpion, or a complete hull disintegration as appears to have happened to SSN593, USS Thresher.

The problem is not a static one of looking at weights but a dynamic one, looking not only at the boat's overall weight but that weight's bow heavy distribution and the momentum of the boat in the downward direction, as well as sea pressure effects. I still remember a very experienced chief petty officer trying to get it through my thick head as I was learning this that as the boat goes deeper, the steadily increasing sea pressure fights against the high pressure air (on the boats I was on, 4500# air, not 3000) trying to expel the water in the main ballast tanks. You can get to the point long before reaching design depth that countervailing sea pressure keeps even all your air banks' 4500# air sufficiently compressed that you can't ever get all of the water out of the main ballast tanks, so that if you haven't arrested the boat's downward momentum by that point the problem will get nothing but worse as you continue to go deeper.

However, there are certain other things about this sequence that I have always wondered about. One thing that has never made sense about this sequence was the pressurizing of the compartment, because once the torpedo tube outer door was secured it would have no effect; perhaps that was SOP in 1968 as a backup precautionary measure, but we would not have done it in the 1980's unless it were specifically ordered by the captain.

There are any number of other technical things I could nitpick about in this movie, but the fact is that it is more accurate than not in regard to technical matters, and it is obvious that the writers and director, John Sturges, went to a lot of effort to pay respect to technical issues in comparison with just about anything else regarding submarines that you are likely to see.

Having said all that, one thing that is worth mentioning, however ironically, is that this casualty itself could never have occurred as portrayed in the film in the first place, because, as Rock Hudson says with such admirable succinctness in the movie, one thing that can't happen on a submarine is to have both ends of torpedo tube opened at the same time. Regardless of Patrick McGoohan's (may he rest in peace) explanation, this is because the thing that isn't mentioned here is that the inner and outer doors on US submarines are **mechanically** interlocked for the very purpose of preventing this kind of problem. You can't open both at the same time anymore than you can tow your rear-wheel-drive pickup truck forward with the transmission stuck in reverse, for just as you would have to disconnect the drive shaft to do that, so too you would have to disconnect the mechanical interlock, which is not only not mentioned by Patrick McGoohan, but because it is plainly visible right alongside the tube would be spotted by anyone working there at a glance. Moreover, submarine torpedo rooms always have a watchstander present 24 hours a day while at sea, and they are popular hangouts for off-watch crew looking to socialize, if not actually sleeping spaces for some crew as in all World War Two submarines and many subsequent nuclear-powered boats, so that numerous other people would be expected to be there at all times. Worse still, I have to wonder about the procedure of using a torpedo to blow a hole in the ice. Apart from the danger this might represent to the submarine, I have to wonder how you get one to detonate when and where you wanted it to - maybe they were going to use a vintage MK. XIV or other weapon equipped with a contact exploder? Certainly I don't know of any contact exploder in the later Mk. 37 and 48 torpedoes, which were designed to be used in combat relying on the presence of the magnetic field of a steel target to detonate under normal circumstances. Here, at last, you can find some "Hollywood" in this otherwise very plausible sequence.

In theory, a flooded forward compartment should not cause the boat to descend at that rate. It might tip downward. A boat can be caused to rise by releasing compressed air into the ballast tanks. (There are about a dozen compressed air tanks with 3000 psi air. At 3000 psi, a cubic foot of air is reduced to the size of a dime.)

Yeah, they were in a world of hurt. As I looked at this I couldn't help thinking of it in terms of the boomers I'd been on, where the forward room is smaller in proportion to the whole ship, and is a self-contained compartment of its own (the boomer's biggest compartment is it vast missile compartment, and that alters the arithmetic substantially from a fast attack). Under those circumstances, as best as I recall, flooding that room doesn't rob you of all your reserve buoyancy, but you have a major trim problem (to put it mildly) and you can't drive yourself to the surface except on a major backing bell, if that were possible.

I had not thought about the effect of pressurizing the compartment to help out the pumps, but certainly you think that could help. One thing conspicuously missing from this sequence is the chief of the boat, and absent that at this point I can't remember if the captain gave any orders to pump anything or not.

As far as the gigantic empty berthing compartment just aft of the torpedo room where the marines were berthed that looks like pure Hollywood imagination (that boat even had to much empty space in the officer accommodations, as well) except to the extent that I had to wonder whether it didn't have some inspiration in the oversized one-off fast attack submarine TRITON, a white elephant almost as big as a boomer. Its hull was surely big enough to accommodate something like that, whether it was designed that way or not.

Yeah, they were in a world of hurt. But as as I looked at this I couldn't help thinking of it in terms of the boomers I'd been on, where the forward room is smaller in proportion to the whole ship, and is a self-contained compartment of its own which does not contain anything very far beyond torpedo room gear (unlike all the later later fast attacks, where the torpedo room is in the operations compartment; also, the boomer's biggest compartment is its vast missile compartment, which alters the arithmetic substantially from a fast attack). Under those circumstances, as best as I recall, flooding that room doesn't rob you of all your reserve buoyancy, but you have a major trim problem (to put it mildly) and you can't drive yourself to the surface except on a major backing bell, if that were possible.

As far as the gigantic empty berthing compartment just aft of the torpedo room where the marines were berthed that looks like pure Hollywood imagination (that boat even had to much empty space in the officer accommodations, as well) except to the extent that I had to wonder whether it didn't have some inspiration in the oversized one-off fast attack submarine TRITON, a white elephant almost as big as a boomer. Its hull was surely big enough to accommodate something like that, whether it was designed that way or not.

One thing I agreed with ion particular was the captain's statement that having both ends of the torpedo tube open at the same time is not possible under normal circumstances. It just isn't. I remember while qualifying n submarines wondering just what kind of casualty that could really be likely to occur could break the door interlock and permit that to happen.