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Dr. Sviatov is a frequent contributor ta THE SUBMARINE REVIEW and has been a knowledgeable observer of submarine characteristics across the world.

After the deaths of American nuclear submarines THRESHER and SCORPION and Russian nuclear subs KOMSOMOLETS and KURSK there had been a lot of publications about these tragedies and their details. But unfortunately there were almost no naval architectural analyses of these catastrophes.

It is understandable that the American and Russian naval architects in their design bureaus are not interested in publicly discussing such a delicate subject. But this problem is so crucially important that it deserves an independent and not a biased analysis.

It should be mentioned that the American and Russian naval architects who design surface ships are much more certain relating to their vessels. The notion in principle is very simple. A major surface warship, let us say, from a destroyer class and bigger, must preserve her buoyancy and stability with flooding of any two compartments.

As to combat submarines’ designers, the situation is different. During the many years of development of submarines in various countries there had been developed certain criteria of that class of combat ships damage control or unsinkability.

On the diesel-electric submarines of the USA, which were built before and during World War II, the surface unsinkability had been provided. A submarine had to remain on the surface with flooding of any one compartment and two adjacent ballast tanks Surface unsinkability of these submarines was provided by a certain level reserve of buoyancy and by dividing the pressure hulls on several compartments. On the American Fleet Type World War II submarines the pressure hull was divided by significant strength transfers bulkheads on 8 compartments and
reserve buoyancy was sufficient- some 30%.

On these submarines was provided also some degree of the so-called underwater unsinkability, in other words, the ability of a submarine to sail underwater with one flooded compartment. The main means to prevent the flooding of the whole pressure hull were the sufficiently strong transfer bulkheads. These bulkheads on the Fleet Type submarines were designed in such a way to prevent the flooding of the adjacent compartments in a case of one compartment flooding on the working (close to maximum) diving depth, which was not so great- some 300 feet.

Russian naval architects now, like American naval architects in World War II, provide surface unsinkability of a nuclear submarine with any one flooded compartment and two adjacent ballast tanks with reserve of buoyancy some 30%. American naval architects, wishing to provide the highest possible speed on a relatively low maximum power of the first generation of serial production nuclear submarines (Skipjack class’ standard nuclear power plant of some 15000 hp in comparison with 35000 hp on the first generation Project 627 Russian nuclear sub November class), decided to reduce on their serial nuclear submarines the reserve of buoyancy from 30 to 15 percent.

But they did it not without a hesitation, which appeared in the unique American nuclear two reactors and two turbine compartments nuclear (initially radar picket and later attack) submarine TRITON with 11 compartments and 35% reserve of buoyancy. On that unique sub the surface and also some underwater unsinkability with any one flooded compartment had been provided.

And not only TRITON had the usual previous conventional submarines reserve of buoyancy. The British post World War II diesel-electric submarines of Porpoise type, French subs of Narval class and American submarines of Tang and Barbell classes were designed with reserves of buoyancy 25-35%. And the Russian nuclear submarines of all classes had and have their reserve of buoyancy not less than 30%. For a comparison of these two different approaches in designing of American nuclear submarines it is reasonable to compare longitudinal cuts of the US nuclear submarines. They were built some quarter of a century ago, but the naval architectural principles of SSN THRESHER are almost the same for all the most modern nuclear attack (and in principle also for ballistic missile nuclear submarines) of the United States.

The pressure hull of THRESHER SSN is divided by relatively strong transfer bulkheads on 5 compartments with one reactor and one turbine compartment and the reserve of her buoyancy is some 15%. With flooding of one of these power plant compartments the submarine is losing her ability to sail and use hydrodynamic forces for compensating of her negative buoyancy, but will preserve her surface unsinkability. But with flooding of anyone of three other compartments THRESHER SSN would be able to provide her surface unsinkability and some degree of underwater unsinkability.

The pressure hull of TRITON SSN was divided by sufficiently strong transfer bulkheads on 11 compartments with two reactor and two turbine compartments and the reserve of her buoyancy is some 35%. With flooding of any one compartment, except of reactor or turbine, the sub will preserve 100% of her horse power and will be able to use all of her power for compensating a negative buoyancy, and even with flooding of one reactor and one turbine compartment simultaneously she will preserve 50% of her power for such a compensation.

But now the most interesting problem is in comparison of the two newest nuclear attack submarines: the US serial construction nuclear attack submarine of Virginia class and the Russian mass production nuclear attack submarine of Acula class. They represent the most contemporary and advanced items in the development of nuclear attack submarines in these countries.

The really one significant difference between the American and Russian subs is their reserve of buoyancy (15% and 30%). American naval architects consider that 15% reserve of buoyancy is sufficient from the point of view of the same degree of a sub’s surface and underwater unsinkability with one flooded compartment, probably considering that in such circumstances the only one way of escaping sinking is surfacing of the submarine.
Russian naval architects are more conservative and the reserve of buoyancy of their submarines is not lower than 30%. The crucial question is: how much speed increase is reached by American naval architects by reducing the buoyancy reserve of their nuclear submarines from 30 to 15%? The answer is: very little, not more than a couple of knots. And this gain could be compensated by easily increasing the power plant horse power not more than 10%.

So, by my opinion the game here does not cost the value of the candles. But what can be done for increasing the unsinkability of existing force of the US nuclear submarines?

There, by my opinion, exists only one way: to provide more strength (let us say to 5 atmospheres) to the submarines’ decks, making them watertight and consider the submarine’s unsinkability in this more narrow sense.

As to the Russian naval architects-submariners, they preserved the classical 30% buoyancy reserve for the contemporary nuclear attack and ballistic missiles submarines and providing by such a way a little more degree of surface and underwater unsinkability of their nuclear subs.

By my opinion the Russian approach is more correct and the United States Navy must consider a Russian way as an option in the development of the future American subs and not ignore its own positive experience of World War II submarines and SSN TRITON or at least to increase in reasonable degree the watertightness of the decks of their future nuclear submarines.

It should be mentioned that my idea about watertightness of the American nuclear submarines is an assumption. I do not know if it exists in reality on the US subs or not, but l know that it was not implemented on the Soviet nuclear submarines. But I never read or heard about a possibility to use that idea for increasing survivability of submarines. If it is my invention, I would be very glad to present it for American and Russian nuclear submariners.
The problem of nuclear submarines’ underwater unsinkability with one flooded compartment is extremely important, especially for nuclear submarines of the United States. But, being a Russian by birth, education and professional formation, I am also recommending its implementation for nuclear submarines of Russia and other civilized countries.

Presenting my personal point of view that Russian naval architects-submariners are more conservative and cautious and not welcoming the idea of reduction in half the reserve of buoyancy and number of compartments on their nuclear submarines, I like to present the point of view on this subject of former Assistant Secretary of the Navy for Research, Engineering and Systems

Melvin R. Paisley:
“The Soviet submarine technology advantages for quieting, strengthened double hulls, higher speed, higher
reserve buoyancy, and deeper operations are advances which by and large were not stolen or brought from the United States. Some technologies are Soviet design decisions which are different from our decisions. Other technologies are the result of using by them advances of high strength hull materials. The Soviets are ahead of us in these technologies” (Testimony before the Committee on Appropriation, House of Representatives, 2 April, 1985).

In conclusion I would like to say, that what had been done, cannot be undone. But first, for the future United States nuclear attack and ballistic missiles submarines might be reasonable to think about increasing on them the reserve of buoyancy from 15% to 30% and second, about increasing the number of their compartments from 3 to, let us say, 5 or at least to increase the strength of their decks, probably, by two times. And another important consideration.

The Russian KURSK nuclear sub had perished from blasts of torpedoes in their first compartment because their control rooms had been in the second compartment. So, by my point of view, the control room on a safe nuclear submarine must be at least the third compartment, what is absolutely impossible for the contemporary US nuclear submarines which have only three major compartments. But the Russian naval architects are not significantly better in aspects of submarines unsinkability because of having six compartments on the Acula class nuclear attack submarines’ they put the subs’ control rooms in the second compartment as it was made on the perished KURSK sub.

In other words they did not take into account the lessons of the tragic destinies of the Russian attack nuclear submarine KURSK.

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