Maximum diving depth of submarines: features and requirements. Maximum Submersion Depth of Submarines A Simple Practical Method for Submerging a Pump
Whoever dived deeper wins
Among the many characteristics of a submarine, one of the main ones is its diving depth. Moreover, the development of military equipment only increased the importance of this factor. Before World War I, the maximum diving depth for a submarine was considered to be 50 meters. At such a depth, the enemy could no longer detect the boat, and in underwater warfare this is the most important thing.
However, progress does not stand still, especially in military affairs. The means of detection and destruction were improved, and the submarine's diving depth began to move into first place. Depth charges, acoustic and sonar capabilities of anti-submarine ships - all this drove submarines deeper and deeper. In addition, the greater the thickness of water that separated the boat from the surface, the greater the opportunity for maneuver and safe navigation.
Conquering the depths
The submarines entered World War II with 100 - 145 meters of depth behind them. In the post-war years, for the first nuclear-powered submarines this value reached 200 m, and for 2-3 generations of nuclear submarines, the depth gauge indicators exceeded 400 meters. There are, of course, record holders in this matter. For example, the famous "Komsomolets" (K-278) set an absolute record for the maximum diving depth of a submarine - in 1985 the submarine went under water to 1027 meters.
American experts believe that the diving depth of a submarine in modern conditions should begin at 600 m and reach 1200 m. The main problem in this case is compensation for the increasing water pressure on the hull. Every 10 m of descent under water increases the water pressure by 100 kPa. Not a difficult task for a primary school student: what pressure will there be at 1200 m? Answer: 120 kg per 1 sq. cm. On paper, the figure does not look terrible, but in reality the load is prohibitive.
Everything is decided on land
Therefore, the main issue that scientists working in this field are struggling with is the extremely balanced hull architecture of a combat submarine. Based on physical laws, the most suitable shape is a sphere, or spherical. However, such a submarine as a combat unit is ineffective. The resistance of the environment (water) is too high, there are huge problems with the placement of weapons and a large crew. Of course, sooner or later, this problem will be solved. In the end, the optimal balance between form, content and speed will be found.
The second question that constantly arises, and apparently will always arise, is the material of the case, its constant improvement. The maximum diving depth of a submarine is limited, first of all, by the strength of the material from which the hull is made. Once upon a time, boats started with wooden hulls, then they switched to iron, and now steel and titanium hulls are in great use. However, the process is ongoing, and pundits are in constant search.
The properties of steel are constantly improving and are manufactured specifically for underwater applications. But metal is beginning to become a thing of the past. Hard plastics and reinforced fiberglass are gradually replacing some body elements, and experts predict a great future for them. For example, fiberglass, obtained by reinforcing synthetic resin with glass fibers, is not much inferior in strength to steel, but is 4 times lighter. Here scientists are also trying to achieve a balance - between weight and strength.
The desire to reach the maximum diving depth of a submarine is not a whim of scientists or an abstract desire. A boat sailing at great depths merges with the bottom and is less noticeable. In modern submarine warfare, this factor can become decisive. A powerful, heavy missile carrier, secretly deployed to a strike position, is capable of ending any conflict in favor of its country with one salvo.
Submarine shipbuilding has several goals. All of them, one way or another, are associated with a decrease in the possibility of detecting a submarine due to an increase in the distance between it and the water surface, as well as some other factors.
Of course, the military-industrial complex is generally a special area, the goals of which are often very different from the aspirations of an ordinary civilian. However, in this article we will consider some data on the diving depth of submarines, as well as the limits within which this value varies.
A little history: bathyscaphe
The article will, of course, talk about warships. Although human exploration of the sea includes visiting even the planetary maximum depth - the bottom of the Mariana Trench, which, as is known, is located more than 11 km from the surface of the World Ocean. However, the historical dive, which took place back in 1960, was carried out in a submersible. This is a device that does not have buoyancy in the full sense, since it can only sink and then rise due to the tricks of an engineering genius. In general, when operating a bathyscaphe there is no question of moving in a horizontal plane over any significant distances. Therefore, the diving depth of submarines, which, as is known, can cover enormous distances, is significantly less than the record for a bathyscaphe, at least for now.
The most important characteristic
Speaking about records in the field of ocean exploration, we should not forget about the true purpose of submarines. Military purposes and the warhead usually carried on such ships imply not only the highest mobility required for them. In addition, they must skillfully hide in water columns that are ideally suited for this, emerge at the right moment and descend as quickly as possible to the depth necessary for survival after a military operation. In fact, the latter determines the level of combat capability of the ship. Thus, the maximum diving depth of a submarine is one of its most important characteristics.
Increase factors
There are several considerations in this regard. Increasing the depth makes it possible to improve the maneuverability of the submarine in the vertical plane, since the length of a warship is usually at least several tens of meters. Thus, if it is 50 meters under water, and its dimensions are twice as large, moving down or up is fraught with a complete loss of camouflage.
In addition, in water columns there is such a thing as “thermal layers”, which greatly distort the sonar signal. If you go below them, the submarine becomes practically “invisible” to the tracking equipment of surface ships. Not to mention the fact that at great depths such a device is much more difficult to destroy with any weapon available on the planet.
The greater the diving depth of submarines, the stronger the hull must be, capable of withstanding incredible pressures. This, again, benefits the overall defense capability of the ship. Finally, if the depth limit allows it to lie on the ocean floor, this also increases the submarine's invisibility to any locating equipment available to modern tracking systems.
Basic terminology
There are two main characteristics that show a submarine's ability to dive. The first is the so-called working depth. In foreign sources it also appears as operational. This characteristic shows the immersion depth of submarines, to which they can descend an unlimited number of times during the entire period of operation. For example, the American Thrasher normally completed 40 dives per year within this value, until, during another attempt to exceed it, it tragically died along with the entire crew in the Atlantic. The second most important characteristic is the calculated or destructive (in foreign sources) depth. Corresponds to its value at which the hydrostatic pressure exceeds the strength of the body calculated during the design of the apparatus.
Test depth
There is one more characteristic that needs to be mentioned in context. This is the immersion depth of a submarine, the limit according to calculations, below which can cause destruction of the skin itself, or frames, or other external equipment. It is also called “test” in foreign sources. In no case should it be exceeded for a specific device.
Returning to the Thrasher: with an estimated value of 300 meters, it went to a test depth of 360 meters. By the way, in the USA, the submarine is sent to this depth immediately after launching from the factory and, in fact, “breaks in” on it for a certain time before being handed over to the agency ordering it. Let's finish the sad story of "Thrasher". Tests at 360 meters ended tragically for him, and although this was not caused by the depth itself, but by technical problems with the nuclear engine of the submarine, the accidents, apparently, were not accidental.
The submarine lost speed due to the engine stopping, blowing the ballast tanks did not produce results, and the device sank to the bottom. According to experts, the destruction of the submarine’s hull occurred at a depth of about 700 meters, so, as we see, there is still a fair difference between the test value and the truly destructive one.
Average numbers Naturally, depth values increase over time. If WWII submarines were designed for values of 100-150 meters, then subsequent generations increased these limits. With the invention of the ability to use nuclear decay to create engines, the diving depth of nuclear submarines also increased. In the early 60s it was already about 300-350 meters. Modern submarines have limits of about 400-500 meters. While there is a clear stagnation on this front, it seems that it is a matter of future developments, although it is worth mentioning the extraordinary project created in the Soviet Union in the 80s.
Absolute record
We are talking about the Komsomolets submarine, which, unfortunately, tragically sank, but it still holds the unconquered peak in the exploration of the depths of the sea by modern submarines. This unique project has no analogues in the whole world. The fact is that for the manufacture of its body a very durable, expensive and extremely inconvenient material to process was used - titanium. The maximum diving depth of a submarine in the world still belongs to Komsomolets. This record was set in 1985, when a Soviet submarine reached 1,027 meters below the sea surface.
By the way, the working value for it was 1000 m, and the design value was 1250. As a result, Komsomolets sank in 1989 due to a strong fire that started at a depth of about 300 meters. And although he, unlike the same “Thrasher,” managed to surface, the story still turned out to be very tragic. The fire damaged the submarine so much that it sank almost immediately. Several people died in the fire, and about half the crew drowned in icy water while help arrived.
Conclusion
The diving depth of modern submarines is 400-500 meters, the maximum usually has slightly higher values. The record of 1027 meters set by Komsomolets is not yet within the capabilities of any of the submarines in service in all countries. It's up to the future
Everyone knows that the maximum depth of the ocean is 11 kilometers in the Mariana Trench, but there are many shallow areas in the oceans and seas. What should be the diving depth of future submarines? This question can be answered by analyzing the distribution of depths over the area of the World Ocean. This analysis shows that a submarine with a diving depth of 5500 meters can reach the bottom of 90% of the area of oceans and seas, and with a diving depth of 4600 meters - 60% of the area. The ability to reach the bottom anywhere in the ocean opens up the possibility of using new tactics, turning nuclear submarines into a decisive factor in operations in ocean theaters.
In the practice of underwater shipbuilding, the following concepts of immersion depths are used: working, limiting and design (destructive). The ratio of the calculated depth to the working depth is called the safety factor, usually it is 1.5 - 2. The working diving depth of WW2 submarines was 100 - 150 meters. American submarines built in the 1950s have 200–250 meters, while nuclear submarines built in the 1960s have increased to 350–400 meters.
Further increase in depth depends on the possibility of increasing the strength of the hull. The nuclear submarine has two hulls: durable and lightweight. The durable hull houses the internal equipment and crew, and the lightweight hull forms the ballast tanks for diving and ascent.
On modern shallow-sea missile submarines, hull structures account for 40% of the weight displacement, of which the pressure hull accounts for 20% of the boat's weight. Unlike other types of equipment, an increase in the mass of a nuclear submarine's hull is not only a cost, since a more massive hull simultaneously increases resistance to the effects of weapons, including nuclear weapons.
In the 1960s, high-strength steel with a yield strength of 70 kg/mm2 was used as the material for the strong hulls of nuclear submarines. In terms of strength properties, it is twice as strong as steel, which is widely used in general mechanical engineering.
The diving depth of the experimental submarine of the US Navy "Dolphin" is 1200 meters, steel with a yield strength of 70 kg/mm2 is used, the durable hull accounts for 60% of the weight of this boat.
What are the prospects for improving the mechanical characteristics of hull materials? Back in the early 1960s, steel with a yield strength of 140 kg/mm2 was used as the material for Polaris rockets. It is interesting that in rocket science such steel could not withstand competition with fiberglass. For structures with a displacement of less than 1000 tons, aluminum alloys are also promising. However, US submariners for a long time continued to use old grades of steel with high fatigue strength.
In the USSR, titanium alloys with a density of 4500 kg/m3 and a yield strength of 120 kg/mm2 are widely used; they are equivalent to steel with b(0.2) = 210 kg/m3. The issue of fatigue strength of titanium alloys is largely resolved by the fact that at a depth of more than 200 meters the submarine does not experience pitching even in stormy conditions on the ocean surface.
It is difficult to say by when the task of creating combat nuclear submarines with operating depths of up to 5,000 meters will be solved. The Komsomolets nuclear submarine had a working depth of 2000 meters, which made it possible to confidently make a record dive of 1020 meters shortly after the boat was launched.
So the question is:
Are SCWRs needed for promising nuclear submarines with an operating diving depth of 5000 meters?
SCWR must have a pressure above the critical 225 atmospheres. At 300 atmospheres, the water-vapor phase transition, stretching over tens of degrees, does not have the character of a density jump, which opens up the possibility of spectral regulation. In addition, if it is impossible to have less external pressure in the internal pipelines on a deep-sea nuclear submarine, SCWRs are needed on promising nuclear submarines.
In the primary circuit of the nuclear submarine reactor, 200 atmospheres corresponds to external pressure at a two-kilometer depth. The feasibility of switching to SCWR also depends on how realistic it seems to be in the new generation nuclear submarines to significantly exceed this value.
Consider a cylinder of radius R, length L and shell thickness d made of a material with density p_w. Let the nuclear submarine have a reserve of buoyancy S, let the proportion of the mass of the durable hull in the total mass be X. Let us denote the yield strength of the hull material as b_02. Let us write down the buoyancy condition:
(2*Pi*(R^2)*d*p_w + 2*Pi*R*d*L*p_w) = (p_H2O)*Pi*(R^2)*L*(1-S)*X;
On the left is the mass of the body, on the right is the displaced mass of water. We reduce Pi*R:
2*d*(p_w)*(R+L) = R*(p_H2O)*L*(1-S)*X; Select the equal sign d/R on the left:
(d/R) = (p_H2O * L* (1-S)*X) / (2*p_w *(R+L));
Now remember that hydrostatic pressure P = (p_H2O)*g*H, and for a cylinder, if the wall thickness is much less than the radius, then the withstand pressure P = (b_02)*(d/R) therefore, the maximum immersion depth according to the strength conditions of the floating hull is H = ((b_02) / (p_H2O *g))*(d/R)). Substituting here the found value (d/R), we reduce the density of water and obtain an expression for H:
H_max = ((b_02) / (2*g*p_w))* (L/(L+R))*(1-S)*X
Although for nuclear submarines this is not a destructive depth, since the tensile strength of the materials is higher than the yield strength, the working depth is taken to be 1.4 times less. Let the ratio of length to diameter be L/(2R) = 1:6. Using ordinary ship steel with a density p_w = 7800 kg/m3 and strength b_02 = 700 MPa, choosing a large buoyancy reserve of 30% (S = 0.3) and a strong hull mass of 20% of the total mass (this does not impair speed and other qualities) , we get
H_max = 580 meters. This is an easily achievable value for strategic SLBMs.
It is logical to make tactical nuclear submarines deeper-sea. Using a titanium alloy with a strength b_02 = 1200 MPa, a density of 4500 kg/m3, increasing the mass of the durable body to 40% of the total mass, we obtain the immersion depth H_max = 3450 meters.
Approximately the same figures are obtained for aluminum hulls, as well as for fiberglass; these options are relevant for displacements of less than 1000 tons.
Conclusion: the strength-to-density ratio of existing materials does not allow making high-speed nuclear submarines to a destructive depth of 7 kilometers, which is necessary for a working depth of 5 kilometers. Allowing you to reach the ocean floor at any point on 90% of its area.
At the same time, the SCWR design is easily feasible at a pressure in the primary circuit of 300 atmospheres or more, when the water-steam transition ceases to have a density jump with increasing temperature. The pressure in existing nuclear submarine reactor cores, up to 200 atmospheres, is less than the operating outboard pressure of the new generation of nuclear submarines. For these reasons, SCWR is needed on new generation nuclear submarines. At the first stage, up to 300 atmospheres. One can hope that someday there will also be nuclear submarines with a 5-kilometer operating depth, the SCWR of which will operate at 500 atmospheres.
The transition of a submarine from the surface to the underwater position is carried out by filling the main ballast tanks, and the change in immersion depth from less to greater, as a rule, by the stroke and horizontal rudders.
Diving a submarine in two stages is usually called a conventional dive. It is produced:
At the sign;
When trimming in areas that are difficult to maneuver in a submerged position;
For training purposes, as well as at the discretion of the submarine commander.
During a normal dive, the end tanks of the main ballast are filled first, then the middle group when the quick dive tank is empty.
Before diving on a submarine, the holds are drained, the compartments and battery are ventilated, the bridge is prepared for the dive, and when approaching the dive point, the speed is stopped and the quick dive tank is purged. The dive is preceded by the command of the submarine commander “Everything down. Stand in your places, ready to dive.” The personnel takes places according to the dive schedule, closes the outboard openings and prepares the submarine systems for swimming underwater. The main command post is transferred from the bridge to the central post or to the conning tower. Observation of the horizon is carried out through a periscope and using radio equipment. Then the main ballast tanks of the bow and stern (end) groups are filled, and the ventilation of the stern group opens 1-2 seconds earlier than the bow, and the submarine moves into a positional position.
In the positional position, the filling of the drainage line and unloaded torpedo tubes with water is checked, and the compartments are inspected to establish the quality of sealing of the durable hull. The roll and trim of the submarine are reduced to zero.
After completing the above steps, the main ballast tanks of the middle group are filled. The ventilation valves of these tanks close at a depth of 5-7 m. If the submarine begins to sink quickly when the middle group begins to fill, you should immediately close the ventilation valves of the middle group tanks, vent the “middle” one, start the pump to pump water from the surge tank overboard and float up into a positional position, and then establish and eliminate the cause of the submarine’s failure. Only after this repeat the dive. If the submarine does not dive when the middle group is filled, it is considered “light”. In this case, the positive buoyancy is extinguished by receiving water from overboard into the surge tank. When the submarine reaches a depth of no more than periscope, the ventilation valves of all main ballast tanks are closed.
Regular diving on the go
Having arrived at the dive point and switched to the required mode of movement, the submarine commander commands: “All down. Stand in your places, ready to dive.” When executing this command, the same actions are carried out in the same order as when diving without a move. After the command “Fill the middle one,” the commander orders: “Dive to so many meters, trim so many degrees.” When diving to a safe or greater depth, it is not recommended to create a trim of more than 5-7°.When diving on an even keel, the filling of the main ballast tanks will be more uniform. In this case, the horizontal rudders are shifted “parallel to the dive” so that the trim of the submarine is equal to zero. This position persists to a depth of approximately 5-7 m.
Once the submarine reaches the specified depth, it is possible to create a trim specified by the commander.
If the boat does not submerge, water should be taken into the surge tank. In this case, as soon as the depth gauge shows a change in depth, water intake is suspended. If, after filling the middle group of main ballast tanks, the submarine begins to sink quickly, it is necessary to create a trim to the stern, using the stroke and rudders to keep it from further diving. At the same time, it is necessary to pump water from the surge tank overboard. If this is not enough, you should partially blow out the middle group of main ballast tanks, pump out the required amount of water from the surge tank, and then, having removed the “bubble” from the “middle” one, continue the dive.
Urgent dive
An emergency dive is performed by the submarine commander or watch officer and, as a rule, one combat shift. It ensures that the submarine goes under water in the shortest possible time.At the command “All down,” the personnel on the bridge quickly descend into the boat. At the “Urgent Dive” signal, personnel perform the following actions:
Stops diesel engines, disengages bow clutches, battens the air supply shafts to diesel engines and other outboard openings, opens the pressure equalization valves of the main ballast tanks, which contain fuel, as well as the buoyancy tank ventilation valve;
The upper deckhouse hatch is battened down (by the submarine commander or watch officer);
Powered by electric motors;
Fills main ballast tanks;
Controls horizontal rudders;
Blows out the rapid immersion tank and closes its seacocks;
Closes the ventilation valves of the middle group and main ballast tanks.
During an urgent dive, the middle group of tanks is filled after the conning hatch is battened down. The control device of the alarm station must indicate that the wheelhouse hatch, the locks of the air supply shaft to diesel engines, ship and battery ventilation are closed.
During the initial period of the submarine's dive, the bow horizontal rudders should be set to submerge, and the stern rudders should be set to ascent. In this case, both pairs of horizontal rudders create drowning forces. Stern horizontal rudders, which create a trimming moment at the stern, help keep the boat on an even keel, balancing the trimming moment that appears with the filling of the quick dive tank.
Upon reaching the depth, when all the tanks of the main ballast are filled, the stern rudders should be shifted to dive, create a trim of up to 10° on the bow (depending on the design of the submarine) and hold it during the dive.
If the submarine must remain at periscope depth, the rapid dive tank is purged at a depth equal to half the periscope depth. If it is necessary to go to a safe depth, the rapid immersion tank is purged at a depth no less than the periscope. The ventilation valves of the main ballast tanks are closed immediately after the submarine goes under water.
As a rule, with the command “Urgent dive” the order is given by the submarine commander (officer on watch): “Dive to a depth of so many meters with a trim of so many degrees.” When approaching a given depth, the trim is pulled back, and the horizontal helmsman reports the depth of the dive using the depth gauge.
During an urgent dive, you must be prepared to perform an emergency blowdown of the end tanks of the main ballast if the trim, rapidly increasing, exceeds the permissible limit. Blowing out the middle group of tanks may be required in case of loss of buoyancy due to incorrect calculation of the submarine's load or in case of late blowing of the fast dive tank.
Dive to extreme depth
In a submerged position, the submarine can be located at depths: periscope (7-9 m), under the RDPThe meaning of the word “deep” is as difficult to express in numbers as it is to indicate the height of the word “high”.
Eighteen meters is “high” for a person standing on the ground and “low” for a satellite in orbit. Obviously, the terms “deep” and “high” are subjective. However, physics and physiology can slightly reduce the arbitrariness of the meaning of the word “deep” in recreational diving. In any case, the line must be drawn somewhere, if only to make our discussion more meaningful and understand the characteristics of diving.
RADI and most members of the recreational diving community define “deep” diving as diving to 18 meters or less, but not deeper than 40 meters. Recreational diving does not involve diving to depths greater than 40 meters, so they are not available to amateurs. Considering the capabilities of equipment for amateur diving, limited time when diving non-stop to depths of more than 18 meters, as well as the intensity and focus of training for amateur divers, setting depth limits is very useful and justified by experience.
Although the maximum depth is 40 m, as practice shows, there are four reasons why in most cases it is necessary to reduce the optimal depth limit to 30 meters. Firstly, at depths greater than 30 meters, small no-decompression limits and rapid air consumption make dives very short. Considering the time and effort that goes into planning and executing a deep dive, the program and goal should be completely satisfying and achievable within 10 minutes.
Secondly, at depths greater than 30 meters, most divers are exposed to nitrogen narcosis. This is nitrogen poisoning that increases with depth. Although sensitivity to blood nitrogen varies from person to person, it is a good enough reason not to go deeper than 30m.
Thirdly, when diving to depths of more than 30 meters, the chances of developing decompression sickness increase, especially with repeated dives. With only one air tank, at this depth it is very easy to exceed the no-compression limit.
Finally, in many places at depths of more than 30 meters, nothing or almost nothing is visible - the water absorbs the light. There it is much more difficult to navigate and read instrument readings - the latter circumstance makes it difficult to control the equipment.
How to Increase Your Personal Depth Limit
Although in the diving community "deep" dives are generally considered to be dives starting from 18 meters, you need to decide what kind of dive is "deep" for you personally based on your environment, your training and experience. When setting a depth limit for yourself, do not forget about the experience and training of your partner.
Let's say, diving to 18 meters will not cause any difficulties if it is done in the warm, clear waters of a tropical sea, and you and your partner are appropriately prepared, and have been actively diving lately. The same dive, but after a ten-month break and without preparation will probably be more difficult and seem more “deep”. The exact same dive to a depth of less than 18 meters in a cold and dark lake in poor visibility conditions can be considered “deep” even if there is a experience and training.It is clear that depth limits vary depending on circumstances.
When setting your depth limit for a given dive, take into account the conditions in which it is being made, as well as your partner's capabilities and your own. First, think about the diving conditions. Based on these, what is the actual depth limit? Maybe it's better for you to start with a shallower dive and then gradually increase the depth? Secondly, decide how physically and mentally prepared you are for the dive. Are you in good shape, do you have the necessary experience, do you feel confident? Third, look at what depths you have dived to before, what your nitrogen group is, and how much time you have spent on the surface since your last dive. Check your dive computer if you have one. Repeated dives reduce the no-decompression limit, which limits the depth of your dive (remember, deeper dives come first). Fourth, assess the geographic location of the place where you are diving. How quickly will help arrive if something happens to you? Fifth, evaluate your partner's capabilities using the same criteria. The optimal and safe depth for both of you will be the limit for this dive.
They go deeper
The diving community almost unquestioningly accepts 40 meters as the limit for recreational diving, but you've probably heard or read about technical diving people going lower. This circumstance, however, does not in any way affect the depth limits established for amateur divers.
Having understood the essence of the matter, you will understand that when practicing technical diving you need to take much more equipment under water: often this is not one, but four to six cylinders, several regulators, and so on, with an increasingly complex design. Diving to depths of more than 40 meters often requires breathing a special helium mixture, as well as several decompression stops lasting an hour or more. As you can imagine, this type of diving requires special training and significant prior recreational diving experience. Even with the appropriate equipment, experience and training, technical diving remains a much riskier activity than recreational diving. When you take into account all the additional equipment, special diving techniques and intensive training that reduce the risk of technical diving, exceeding the 40-meter depth limit seems quite reasonable. Technical diving is not for everyone, and it is not the next necessary step even after several thousand recreational dives, but if you do have an interest in technical diving, you will have to acquire the necessary training and experience before giving it a try.
