Iron Sonata of World War II

Aiming at the shortcomings of the submarine's survivability, which is highly dependent on concealment, weak in information collection and interaction capabilities, slow underwater speed, and poor endurance, the allied forces on the previous plane gradually figured out from practice after suffering a big loss. A set of effective countermeasures is the anti-submarine blockade and centralized escort system that keep the German submarine force in the throat.With the perfection and systematization of these measures, the comfortable hunting time of the sea wolves came to an end, and the German Navy's strategy of breaking diplomatic relations also went completely bankrupt.

Regarding the effectiveness of the Allied anti-submarine measures, many people will have such doubts: At the end of World War II on the last plane, there were still a large number of German submarines that could safely pass through the anti-submarine blockade and break into the depths of the Atlantic Ocean to carry out activities.At that time, the success rate of various submarine attack methods did not seem to be very high. For example, the "hedgehog" deep bomb with relatively good performance in the above plane, even in the most ideal state, this weapon has less than 10% success rate. Chance to damage or sink the submarine.Now the question is: Why is such an omission of the blockade and such an inefficient anti-submarine weapon able to keep hundreds of submarines of the German Navy on their backs?

If you want to answer this question, you must first point out: Although in terms of specific details, there are still a large number of loopholes that can be exploited in the anti-submarine system of the Allied forces; , multi-level, and three-dimensional network, as long as the submarine is in this network, it will be restricted at all times and everywhere, and there is no comfort zone to speak of.This is where the power of the Allied anti-submarine system lies.

Next, let us take the "VIIC type" medium-sized submarines built in large numbers in Germany as an example, and talk about the restrictive effect of this system on submarines.

First of all, the VIIC submarines will have trouble when crossing the blockade.The Allied forces rely on shore-based patrol aircraft, surface warships, and the offshore blockade pulled up by modified anti-submarine ships. Although it is somewhat weak against submarines in a submerged state, the depth of this blockade is as high as several hundred kilometers, far exceeding that of the VIIC type. The submarine has a maximum underwater range of 80 nautical miles/4 knots.

That is to say, in the process of passing the blockade, the German submarine has to go up and charge at least twice, and each charge may take several hours.You must know that floating and charging in the blockade where there are "eyes" everywhere on the water surface and the sky, even in the state of the snorkel, is a matter with a high risk factor.

Although from the actual combat experience of the previous plane, the chance of being discovered by a submarine in a blockade zone is not very high, and the probability of being sunk is even smaller.But the so-called often walks by the river, how can you not get your shoes wet, once your submarine misses once, there will be no chance of missing the next time.In other words, the risk will accumulate with the frequency of your submarine access.And to take a step back, even if the submarine is very lucky and the crew is extremely skilled, and can pass through the blockade unscathed every time, there is no need to be too happy, because there are more severe challenges ahead.

How to search for enemies in the vast sea is a big problem.The Allied forces gathered the transport ships that were originally scattered on the sea to form a formation, which brought a lot of trouble to the submarine's search for the enemy.This is because no matter how large the fleet is, it is still a tiny point-like target compared to the vast ocean and long transportation lines.It's like throwing a thousand pennies at random in a huge gymnasium and finding some of them is easy, but if you throw ten pennies at random, it's much harder to find.

The practice of concentrating merchant ships to form a formation not only reduces the probability of being discovered by submarines, but also allows escort forces to be concentrated and used.In this way, even if a small number of submarines found the traces of the merchant fleet, they would not be able to speak in the face of a large number of escort ships, and would probably give up the attack.Just like a hungry lone wolf on the prairie meets a flock of sheep protected by many shepherd dogs, even if he salivates, he can only retreat in the face of difficulties.

Faced with this dilemma, in the last plane, Karl Dönitz formulated the so-called "wolf pack tactic", that is, a large number of submarines were organized into a fleet, and then scattered around the opponent's route to form a warning screen. Once a certain submarine found After knowing the whereabouts of the merchant fleet, instead of launching an attack immediately, they tracked it from a distance while reporting the formation's position, composition, speed, and course to the command center.Then the command center can call the surrounding submarines to gather near the merchant fleet based on the information, and wait for a sufficient number of submarines to gather around the merchant fleet before choosing an appropriate time (usually at night) to launch a coordinated attack.

In the last plane, the "Wolf Pack Tactics" once achieved good results for the centralized escort system of the Allies.But this tactic also has many fatal weaknesses.One of them is that the submarine's underwater navigation capability is limited, and it can only rely on surface navigation to track the merchant fleet. The same is true for the process of other submarines concentrating on the merchant fleet.

Let's still take the VIIC submarine as an example. The maximum surface speed of this type of submarine is 17.7 knots, and it is not a problem to catch up with ordinary merchant ships.However, the maximum underwater speed of the VIIC submarine is only 7.6 knots, which is much slower than the economic speed of merchant ships.And if you continue to sail at this speed, it will only take a few hours for the battery to die.

Due to the wolf pack tactics, the tracking and assembly of the merchant fleet by submarines mainly rely on surface navigation. In the later period of the war, the Allied forces began to consciously strengthen the aviation force in the escort formation, and expanded and strengthened the escort by adding escort aircraft carriers to the formation. The warning circle around the formation immediately put Doenitz's "wolves" in a difficult situation.Although the number of aircraft carried on the escort aircraft carrier is limited, it is still a very serious threat to submarines.

Although in the previous plane, it was not uncommon for submarines to rely on their own anti-aircraft guns to fight against incoming aircraft, Dönitz even once suggested that submarines use anti-submarine aircraft to fight directly after encountering anti-submarine aircraft.But the Germans soon discovered that due to the high cost of submarines and the low cost of aircraft, it was not worthwhile to fight recklessly, so they gave up the suggestion of letting submarines and aircraft fight hand-to-hand.Therefore, unless the submarine has no time to dive in the future, in most cases, it still has to hide when encountering an anti-submarine aircraft.

However, hiding is not a problem. If the submarine uses underwater navigation to avoid the aircraft, it will neither be able to effectively track the merchant ship nor reach the assembly sea area on time, so the "wolf pack tactics" cannot be discussed at all.And if the submarine continues to implement the established tactics and ventures to use surface navigation to approach the merchant fleet, it will face close contact with anti-submarine aircraft.

Sometimes anti-submarine aircraft don't even need to attack the submarine directly, they only need to press the submarine below the water surface for a few hours, and when the submarine floats up again to look around, the merchant fleet has already disappeared without a trace.Of course, the submarine can also choose to launch an attack without waiting for the teammates to gather after discovering the merchant fleet. After firing a round of torpedoes, listen to the continuous explosion of "hedgehog bombs" and "squid bombs" around you. Listening to heavy metal rock also stimulates your nerves...

All in all, under the anti-submarine system of the Allied forces, if a submarine wants to ensure its own safety, it can only be a salty fish honestly; Gone with the wind, how can I not get stabbed." mentally prepared.This situation is far from the submarine's expected "I can hit you, but you can't find me" situation. It can be said that once this situation is formed, the threat of the submarine will be cut by more than half.

Helena knows very well that in order to completely counter the Allied anti-submarine system, the system must be used to fight the system, rather than relying solely on submarines to fight alone.However, as a key node in the system, the performance of the submarine itself plays a vital role in the strength of the entire system. Therefore, targeted improvement of the technical performance of the submarine is of great significance to the future strategy of the German Navy.For this reason, Helena has spent money and brains all these years.

Chapter 185 Counter Blockade

As a small submarine with an underwater displacement of only a little over [-] tons, the main combat area of ​​the Type II submarine under construction is in the North Sea and the eastern part of the North Atlantic Ocean, which is the surrounding waters of the British Isles.Since these areas highly overlap with the anti-submarine blockade that the United Kingdom may establish, the future combat environment of Type II submarines can be described as perilous. However, Helena insists that it is very necessary to maintain a capable underwater combat force in the British coastal waters all year round. .

In Helena's vision, the main mission of Type II submarines is not only to attack merchant ships that are about to sail into British ports, but warships and modified ships cruising on the anti-submarine blockade are also important hunting targets for Type II submarines.Regardless of the fact that surface anti-submarine ships usually call themselves submarine hunters, in fact they are extremely vulnerable when performing anti-submarine missions.

Because the noise during high-speed navigation will affect the work of the ship's sonar, surface ships during World War II must be in a low-speed navigation state when using sonar.And a battleship moving slowly at a low speed of less than 10 knots is also an ideal target for submarine torpedoes.So don't look at the surface warships as if they are walking in the garden when searching for submarines. If there are other submarines lurking around at this time, then the surface warships may be in bad luck.When a surface warship finds a torpedo track coming from another direction, it is estimated that it is too late to even turn to avoid it, because at a low speed of less than 10 knots, the rudder effect of the warship is also very weak.

Due to the vulnerability of surface warships during World War II when performing anti-submarine missions, this gave Helena a focus to counter the British naval blockade.In Helena's vision, Germany first needs to manufacture a batch of high-performance offshore submarines, and then organize these submarines into hunting groups, each group consisting of four to six submarines.

When fighting in the British blockade, the submarines in the group will take turns to float up and charge, so that some submarines in the group are always in a highly silent state.And once the British anti-submarine ships in cruise state are found, one of the submarines can launch a torpedo attack first.Even if it fails, it doesn't matter. As long as the British anti-submarine ships dare to slow down and enter the submarine search state, there will be two to four other submarines in a good attack position. At this time, the anti-submarine ships sailing at low speed are basically dead. lifeless.

At this time, someone may ask: It is true that a single anti-submarine ship cannot deal with a team of four to six submarines, but what if Britain also organizes its anti-submarine warships into a team?To this Helena can only say: It is just what I like when the British do it.This will greatly reduce the density of warships in the blockade, and the efficiency of the British blockade will also be reduced accordingly.

That's right!When performing escort missions, it is necessary to concentrate ships to enhance the strength of the formation; but when performing blockade missions, it is necessary to disperse ships to control a larger sea area.The number of British ships is also limited. If the warships in the blockade are gathered to form a formation that can deal with the German submarine hunting squad, the area of ​​the sea area that the blockade can control and the size of the "eyes" in the blockade Density will drop.This will allow Germany's medium-sized submarines and ocean-going submarines to break into the Atlantic Ocean more freely, so that Helena's goal of countering the British blockade will be achieved.

More importantly, the design of German surface warships on this plane is almost all designed with an eye on slaughtering young ones.If the British Royal Navy disperses the children over a vast sea area, the efficiency of German surface ships' slaughtering children will decrease instead.And if the British concentrate all the light warships in the blockade into small teams, the German navy can just take advantage of the loopholes at any time, cleanly wipe out several British anti-submarine teams under the cover of aviation, and then rush to the British large fleet. Before swaggering away.

Helena's strategy and tactics can be summed up as follows: If Britain does not make German submarines comfortable, then German submarines will not make British blockade ships comfortable; The psychological preparation for the continuous bloodshed on the blockade, who is afraid of the other in the game of mutual harm.On the previous plane, the construction of the German surface fleet was in disarray, and there was a lack of submarines that were particularly suitable for offshore operations. Naturally, this kind of mutual harm game could not be played, but Helena, on this plane, was happy to accompany the British to play the game to the end.

This is because no matter whether Britain uses the ships of the blockade fleet individually or in groups, it will fall into a disadvantageous situation because it cannot take care of both.The former cannot deal with the German submarines that form a team to spawn monsters, and the latter may be taken away by the German fast fleet that suddenly rushes out at any time. After all, the British fleet cannot always float on the high seas, when and where to attack The choice of attack is with the Germans.

After Helena clarified the operational concept of the Type II submarine, the design goal was basically clarified. This will be a small offshore submarine suitable for operations in shallow waters around the UK. Cruising British anti-submarine ships.The high-risk combat environment requires this type of submarine to have fast dive speed, good underwater maneuverability, high concealment and sufficient production quantity.

Although in the past few years, under the guidance of Helena, Germany has gradually broken through the closed-cycle diesel engine technology. This relatively simple AIP technology allows submarines to operate underwater for several weeks. Several test submarines were used for engineering demonstrations, but Helena is not planning to use the technology on offshore subs.

On the one hand, this is because the liquid oxygen/exhaust gas circulation device of the closed-cycle diesel engine is more complicated, and it is more difficult to control the cost on the offshore submarine. After all, the simplicity of the closed-cycle diesel engine is compared with other several AIP technologies. Compared with the traditional Conventional submarine power mode is still much more complicated.

On the other hand, it is because the type II submarine with a single-hull structure does not have enough space to store a huge liquid oxygen storage tank. If you want to start a closed-cycle diesel engine, you can only put the liquid oxygen storage tank in the pressure hull. Safety is a relatively big hidden danger.In the last plane, the Q-class submarine built by the Soviet Union in the 50s based on the German closed-cycle diesel engine technology placed the liquid oxygen storage tank in the pressure hull of the submarine, but due to the leakage of liquid oxygen in the pressure hull , and could not be ruled out in time, causing several fires, which made this type of submarine notorious in the Soviet Navy.

In fact, even if the crew is prohibited from drinking vodka, the liquid oxygen on the AIP submarine needs to be released due to pressure relief or is not tightly sealed. It is difficult to avoid occasional small-scale leakage. The smarter way is to be like the 212 submarine in the previous plane. Similarly, the liquid oxygen storage tank is placed outside the pressure hull, and then wrapped with a non-pressure hull or fairing, so that even if an accident occurs, it will not affect the safety of the submarine. If the pressure in the storage tank suddenly increases, part of the Oxygen is discharged to the outside in an emergency to reduce internal pressure, which greatly improves safety.

However, the body of the Type II submarine is too small. If a liquid oxygen storage tank is added outside the pressure hull, it will be difficult to ensure a good underwater line shape.Based on the above two reasons, Type II submarines do not use AIP technology, and are still relatively traditional diesel/electric submarines.As for the AIP technology, it should be used on those larger double-hull submarines. The liquid oxygen tank can be arranged between the two hulls.However, this does not mean that the Type II submarine is not innovative. In fact, this submarine is very different from its diesel-electric predecessors during World War I.

The author has something to say: the specific principle of the closed-cycle diesel engine can be read back to Chapter 59.

Chapter 186 Dexterous Dolphin

Due to factors such as platform size and cost control, Helena did not equip the Type II submarine with an AIP system, but greatly enhancing the underwater activity capability of this type of submarine is still a necessary guarantee for the completion of the task of containing the British offshore blockade force.However, in order to enhance the underwater activity capabilities of submarines, not only the advancement of application technology is required, but also the innovation of design concepts is required.

Although in the last world war, submarines had grown into one of the brightest stars in the naval warfare arena, early submarines were actually closer to traditional surface warships in terms of design ideas.It's just that compared to ordinary surface warships, submarines can temporarily dive when launching attacks and avoiding threats by virtue of power generation/electric motors, ballast water tanks, and fully enclosed hulls.

Based on the design idea above, in terms of line shape, most of the early submarines used ship shapes suitable for surface navigation; in terms of transmission mode, most of them used mechanical transmission with high efficiency during surface navigation; Most of them will be equipped with large and medium caliber deck guns.

In fact, under the combat background of the year, there was no problem in adopting this design for submarines. After all, for submarines, the combat environment during World War I was quite friendly.At that time, the sky was still blue, the sea was still green, the merchant ships were still basically unarmed, the performance of the aircraft was still very bad, and there was no such thing as sea radar.

Therefore, in order to save torpedoes and shells, when the submarines at that time encountered a single merchant ship, they sometimes even surfaced directly and generously, and used deck guns to threaten the merchant ship to open the sea valve and sink.Even if there are a few hard-headed merchant ships who refuse to submit immediately, the submarine only needs to fire a cannon to scare the crew, and most merchant ships will recognize the situation and surrender obediently.

It is a pity that this kind of good time will probably be difficult to reproduce in future wars.In World War II on the last plane, with the strengthening of aviation anti-submarine technology and the widespread adoption of radar, the surface activity capabilities of submarines were greatly restricted.And the centralized escort system makes it less and less likely for submarines to attack lone merchant ships with deck guns. Moreover, even if a submarine encounters a so-called lone merchant ship, how can it be judged whether it is an armed anti-submarine ship disguised as a merchant ship?

Based on the new combat environment in the future, Helena gave a vivid metaphor to the designers during the planning stage of Type II submarines: "The submarines in the past were like sea otters, most of the time they were active on the sea surface, only occasionally Diving into the sea to look for food; while killer whales live below the sea surface most of the time, only occasionally surface to take a breath. Now everyone's design goal is to enhance the underwater activity of the submarine. Starting from this model, we will gradually Submarines went from sea otters to killer whales."

Seeing the understanding smiles on the faces of the designers, Helen nodded to everyone with satisfaction, and added with a smile: "Of course, our Type II submarine is just a small 400-ton submarine. It may be a bit exaggerated to compare it to a killer whale. So let's take the second best and design this new submarine as a smart dolphin!" So the general tone of the new submarine to improve underwater maneuverability and endurance time is set like this down.

In order to improve the submarine's underwater activity capability, the Type II submarine first made major innovations in the submarine's line shape, abandoning the traditional ship line shape, and instead adopting a cigar-shaped hull design that is quite new for this era.The specific method is to add a layer of non-pressure-resistant structure above the cylindrical pressure-resistant hull of the submarine to form a trapezoidal bulge extending from the bow to the stern.

Helena has always admired the amazing imagination of Jules Verne, a great science fiction writer in the 19th century. In his classic science fiction novel "Twenty Thousand Leagues Under the Sea", Verne described the "Nautilus" driven by Captain Nemo in this way. "The appearance of the submarine: "The ship is very long cylindrical, with conical ends, like a cigar." Taking into account the requirements of surface navigation, it is a relatively compromised boat design.

In World War II on the last plane, Germany used a more aggressive drop-shaped hull on the V80 submarine.This linear shape has lower underwater navigation resistance than the cigar shape. Driven by the hydrogen peroxide steam turbine AIP system designed by Dr. Walter, the V80 submarine in the previous plane once reached an underwater speed of 28 knots. It was indeed an appalling achievement at the time.

However, the tall drop shape actually has many disadvantages: it not only has a relatively complicated manufacturing process, but also has a relatively low utilization rate of the internal space, and it is also prone to bow bow phenomenon when sailing on the water.After comprehensive weighing, Helena believes that if the underwater speed of the submarine does not exceed 20 knots, the drag reduction advantage of the drop shape over the cigar shape is not obvious.

In fact, in the conventional submarine design of later generations, the cigar shape and the whale shape are very commonly used shapes, while the drop shape and elongated drop shape are more used in nuclear submarines with higher underwater speeds.Moreover, after using the cigar-shaped line, the Type II submarine can also take advantage of the opportunity to arrange the fuel tank, buoyancy adjustment cabin and other equipment that can directly contact with seawater in the non-pressure structure above the pressure hull, thereby saving the space inside the pressure hull. space.

In addition to the optimization of the underwater line shape, the power system of the new submarine has also undergone major innovations, mainly reflected in the structure of its transmission system.When the early submarines sailed on the water, the power from the diesel engine would be divided into two parts in the splitter mechanism, one part would enter the reducer to drive the propeller, and the other part would be used to drive the generator to charge the battery.The transmission mode in which the diesel engine directly drives the propeller through a mechanical connection is direct drive.

Submarines using direct drive have higher transmission efficiency when navigating on the water surface, but there are also a series of disadvantages.Firstly, when the reducer is working, it will generate a lot of mechanical noise, which will increase the probability of exposure of the submarine when navigating on the water surface and in the snorkel state; secondly, the power generated by the diesel engine is shunted through mechanical devices, and it is not easy to drive the propeller and drive the generator Finally, the mechanical transmission structure itself needs to occupy a certain amount of space and weight, which affects the improvement of the power of the generator and the main motor, and is not conducive to increasing the charging speed and underwater navigation speed.

In order to overcome the above-mentioned shortcomings, Helena requires the Type II submarine to adopt an indirect transmission mode, that is, the diesel engine directly drives a large electric motor to generate electricity when it is on the water surface or in the snorkel state, and part of the electricity generated is directly used to charge the battery. The electric motor used to drive the submarine, and then drive the propeller to propel the submarine forward.This is the so-called indirect transmission mode, which can also be called electric transmission.

The disadvantages of the direct drive mode are exactly the advantages of the indirect drive mode.On the one hand, the indirect transmission completely eliminates the noise of the submarine reducer and improves the concealment of the submarine in the snorkel state; on the other hand, the indirect transmission can flexibly allocate the engine power between charging and propulsion; finally, the indirect transmission also The power of the generator and the motor can be made larger, which improves the charging speed and underwater navigation speed.Of course, these benefits come at a price, and the transmission efficiency of indirect transmission is lower than that of direct transmission.Even before Helena crossed over, this gap still existed, and the gap is even more obvious in this era when motor technology is not very developed.

However, in Helena's eyes, it is totally worth sacrificing a little surface performance for better underwater performance.Anyway, the cigar line shape of the Type II submarine has already sacrificed part of the resistance of surface navigation compared to the shape of the boat, and it seems that it is not so unacceptable to sacrifice a little transmission efficiency of the surface navigation. The surface navigation ability of the Type II submarine is just passable.In the blockade area of ​​the British, you don't expect to come up to blow the sea breeze frequently, that would be too contemptuous.

The glorious task of developing an electric drive system was entrusted to Dr. Ferdinand Porsche by Helena early on.Dr. Porsche is very grateful for Helena's unconditional trust, but he doesn't know that Helena just wants to find something for him to do, and the purpose is to prevent this guy from moving his telex system to the tank when he has nothing to do. .You must know that there is enough space on the submarine for efficient water cooling, and there is no overload condition like when a tank climbs over a hurdle, which is just enough for Dr. Porsche to fully display his talent for telex.

Although in the last plane, no matter Dr. Porsche's Ferdinand tank destroyer or Dr. Walter's V80 AIP drop-shaped submarine, they are all typical examples of falling into the pit because of too advanced technology applications.But in Helena's eyes, Dr. Porsche and Dr. Walter belong to that kind of precious misplaced resources.

So Helena asked Dr. Walter to study torpedoes and rocket turbo pumps. Anyway, these two are a one-off deal, and there is no need to consider repeated use like the submarine AIP system; so Helena asked Dr. Porsche to study marine electric drive systems. Anyway, there is no need to pursue the compact size too much, and the motor load will not change frequently...

I hope that Dr. Porsche in this plane can get rid of the hat of "King De Qi Xia", Helena thought so.

Chapter 187 Underwater Maneuvers

Facts have proved that as long as you find a stage that suits you, Dr. Porsche's design is actually very reliable.Through cooperation with MAN and Siemens, Dr. Porsche quickly came up with a power design for the new submarine.After more than a year of improvement and perfection, the prototype of the Porsche solution finally passed various tests successfully.The test results show that the technical performance of this scheme can fully meet the requirements of Helena, thus becoming the design basis of the Type II submarine power system.

Due to the relatively limited displacement, the new submarine adopts a single-shaft propulsion form.The source power of the submarine is a six-cylinder four-stroke medium-speed diesel engine designed by Mann Company with a maximum power of 800 horsepower.When the submarine sails in the surface state or the snorkel state, the diesel engine drives the generator to generate electricity.Through the power distribution system on the boat, part of the power generated by the engine is used to drive the electric motor to propel the submarine, and the rest is used to charge the battery.

According to the designer's calculation, when all the power generated by the generator is used to propel the submarine, the surface speed of the Type II submarine should be able to reach more than 12 knots.In fact, compared with the contemporary submarines of the current plane and the previous plane, the surface speed of Type II submarines at 12 knots is relatively low.

However, as far as the combat mission of the Type II submarine is concerned, the low surface speed is not a fatal problem.After all, the preset main battlefield of this submarine is in the coastal waters of the United Kingdom. Helena does not think that it is right under the eyes of the British. This submarine will have too many opportunities to surface, unless the British patrol ships and aircraft Lookouts are blind.So in Helena's eyes, as long as the Type II surface speed is passable, there is no need to deliberately pursue it.

Compared with the surface speed that can only barely pass, the underwater mobility of Type II submarines is very prominent in this era.After the mechanical transmission was omitted, Dr. Porsche equipped the Type II submarine with a main motor with a maximum power of 1250 horsepower and a cruise motor with a maximum power of 60 horsepower, taking advantage of the freed volume and space.

It is not difficult to see that, unlike the power of electric motors in submarines during this period, which was generally less than that of diesel engines, the power of the main electric motors of Type II submarines far exceeded the power of diesel engines.That is to say, when the Type II submarine sails on the surface at a full speed of 12 knots, the motor on the boat does not even do its best. The reason why it cannot run faster is only limited by the power generated by the diesel engine. Waste the power in the battery on the water.

The high-power main motor combined with the low-resistance cigar line for underwater navigation makes the underwater speed of the Type II submarine expected to reach about 15 knots.Although this speed is not very eye-catching in later generations, you must know that during World War II on the last plane, most submarines' underwater speeds were only between 7-9 knots, and the underwater speed of Type II submarines was their highest. about twice.Please don't think that Type II submarines pursue high underwater speeds to chase merchant fleets underwater. In fact, for Type II submarines that are not equipped with AIP systems, if they sail underwater at the maximum speed, the power in the battery can only maintain Just an hour or two.The real purpose of Helena's Type II submarine pursuing high underwater speed is actually to fight against the British surface anti-submarine ships.

In the contest between the submarine hunting team and the British destroyer, the high underwater speed of the German submarine will not only bring a great advantage to seize the attack position, but also can more easily avoid the pursuit of the destroyer.In World War II in the last plane, almost all destroyers and frigates could normally use sonar at a speed that was lower than the maximum speed of Type II submarines of 15 knots.This is because when the speed of the ship increases, the noise generated by itself will seriously interfere with the sonar.

That is to say, when the Type II submarine escapes underwater at a speed of 15 knots, if the destroyer on the surface wants to use sonar to determine the position of the Type II submarine, it must reduce its own speed to a speed much lower than that of the Type II submarine. This will allow the Type II submarine to slip out of the destroyer's search range with a high probability; but if the destroyer wants to speed up and chase the fleeing Type II submarine, the sonar it is equipped with will be almost ineffective due to the noise generated by the ship. In this state, the Type II submarine can still use its own mobility to calmly get rid of the half-deaf destroyer.

Type II submarines not only have a high underwater speed, but also have a good underwater range.On the one hand, the designers installed as many batteries as possible on the Type II submarine. On the other hand, over the years, Helena has invested in many scientific research projects aimed at improving the performance of lead-acid batteries, including trying to use high-tin-lead-calcium alloys instead as positive electrodes. For grid materials, copper alloys are used instead of lead-antimony alloys as negative grid materials, and reinforced plastics are used instead of hard rubber as battery casing materials. These measures have more or less improved the specific energy and charge-discharge capacity of lead-acid batteries.

The combination of the above two doubles the storage capacity of the type II submarine battery. In addition, Dr. Porsche added a special 60 horsepower low-power cruise motor to the type II submarine, which greatly improved the operating efficiency of the submarine motor at low speed. , coupled with the well-designed low-resistance line shape, allows Type II submarines to sail at least 4 kilometers underwater at a speed of 200 knots.It has reached 2.5 times that of the German underwater main Type VII submarine in the previous plane. Considering that the size of the Type VII submarine in the previous plane is almost twice that of the Type II submarine, this result is already quite gratifying.

The powerful underwater activity capability of the Type II submarine is not only reflected in the maximum underwater speed and endurance, but also reflects the ingenuity of Helena and the designers in many design details.For example, the Type II submarine is equipped with the snorkel, oxygen candle and fast charging method that have been verified on the small "sightseeing submarine" previously built by the "Ship Construction Engineering Bureau" in Japan.

Among them, the snorkel allows the submarine to recharge without fully surfacing.When using the snorkel, the submarine can stay at a depth of several meters underwater and extend the movable air intake tube of the snorkel out of the water. There is a float valve in the snorkel. Once the wave is too large to submerge the floating intake tube, the float valve will automatically close to prevent Seawater floods.In this way, the submarine can start the diesel engine to sail at a low speed and complete the process of charging the battery and ventilating the cabin in a relatively concealed state.

In order to reduce the probability of the snorkel being detected by the enemy's radar, Helena also wrapped a layer of ferrite ceramic material on the active air intake tube of the snorkel to absorb radar waves, weaken radar reflection, and reduce the risk of the snorkel being detected by the ship. and the probability of detection by airborne radar.In this way, even in areas patrolled by British aircraft and ships at high density, Type II submarines are not so easy to be found when they raise their snorkels to charge at night.

Oxygen candle is a kind of emergency oxygen supply equipment.After the oxygen candle is ignited, the sodium chlorate in the candle will be catalyzed and decomposed, thereby releasing a large amount of oxygen.Only a small oxygen candle is needed for several hours of normal breathing for dozens of sailors in the submarine. In addition to supplying oxygen, the oxygen candle can also provide lighting. It is an essential life companion for submariners.

In order to further reduce the exposure probability of the submarine, Helena also organized manpower to study the fast charging technology of the battery.Charging the battery does not shorten the charging time simply by increasing the charging current brutally, because when the battery is charging, the movement speed of electrons is always faster than the speed of electrochemical reaction, and the charge will accumulate on the two poles of the battery, so that The charge on the positive electrode is more positive and the charge on the negative electrode is more negative, thus slowing down the charging speed. This process is called polarization of the battery.

In order to reduce the harm of battery polarization and increase the charging speed, Helena also developed a new pulse charging method for this era for Type II submarines.When the battery is empty, since the polarization phenomenon of the battery is not obvious at the initial stage of charging, it can be charged with a large current and maintained for a period of time.When the battery polarization occurs, it can enter the pulse charging mode, first charge with a large current positive pulse, then stop charging, use a negative pulse discharge to eliminate battery polarization, and then use a large current positive pulse to charge, and so on.When the battery is about to be fully charged, stop the pulse charging and use a small current for trickle charging to prevent overcharging and protect the battery.

Through the development of battery fast charging technology, the charging time of Type II submarines with excellent water quality has been further compressed each time they float up. Coupled with the snorkel with a certain radar stealth capability, Type II submarines have more or less some ships that perform anti-submarine patrol missions in the British coastal waters. The cost of dealing with the body, but these measures are far from enough in Helena's opinion.For the new generation of active and passive sonar that will appear in World War II, Helena must also give more thoughtful consideration.

Chapter 188 The Silent Ghost

After the outbreak of the First World War, in order to deal with the elusive submarine force of the Germans, the famous French physicist Paul Langevin, the old gentleman who presided over the two Solvay conferences, was ordered in danger and finally invented in 1915. developed a new type of detection device known as a hydroacoustic transducer.This kind of equipment cleverly utilizes the piezoelectric properties of quartz crystals to convert sound signals in water into electrical signal output. Based on the characteristics of underwater acoustic transducers, sonar in the modern sense came into being.

Although Lang Zhiwan's invention was very groundbreaking, but limited by the technical level at that time, sonar, which appeared as a new thing in World War I, did not play a very limited role.In the following 20 years, as the design and manufacturing technology of underwater acoustic transducers has made great progress, sonar technology has also achieved tremendous development.During World War II in the last plane, sonar was not only the main means for surface warships to detect submarines, but also an important tool for submarines to detect surface ships. Since then, sonar buoys that can be carried by aircraft have appeared.

According to Helena's plan, the underwater acoustic detection equipment of the future Type II submarine will consist of a medium-frequency active/passive sonar installed on the lower jaw of the submarine and a very high-frequency sonar installed on the command enclosure.Among them, the medium-frequency active/passive sonar is mainly used to search and attack enemy ships, and the very high-frequency sonar is used for navigation and collision avoidance. After all, there are a large number of anti-submarine mines and jagged reefs in the British offshore.However, since the development of these two sonars has not yet been completed, the first six Type II submarines built only have a passive sonar installed in the jaw for the time being.

Because the positioning accuracy of sonar in passive mode is limited, the first batch of six II submarines cannot be like the Type XXI submarine developed by Germany in the late World War II on the previous plane (the Type XXI submarine has a mechanical fire control computer, which can be controlled according to the active The data sent by the sonar automatically calculates the shooting elements and equips the torpedo), and directly uses the sonar to command the submarine to launch a torpedo attack underwater.Instead, you need to raise the periscope first to find the target.Although this somewhat compromised the concealment of the submarine when attacking, fortunately, at the request of Helena, the type II submarine reserved the installation base for the new type of sonar, and it would be easier to replace it when the technology matures in the future.

Although in terms of underwater acoustic detection, the Type II submarine is far from reaching the level that Helena is satisfied with, but in terms of the opposite of underwater acoustic detection - underwater acoustic countermeasures, the Type II submarine has taken a crucial step.The underwater acoustic countermeasure mentioned here refers to the submarine's use of acoustic means to reduce the detection effect of the opponent's underwater acoustic equipment, making it difficult for anti-submarine forces to find their own existence, or to accurately lock their own position.

The means of underwater acoustic countermeasures are generally divided into passive countermeasures and active countermeasures. The passive countermeasures mainly rely on weakening the sonar reflection echo and reducing the sonar intensity of the own ship to achieve the purpose of shortening the enemy's active and passive sonar detection effects; The means of countermeasures is to achieve the purpose of interfering with and deceiving opponents by releasing artificial noise sources or false targets.

Generally speaking, both passive countermeasures and active countermeasures need to be applied comprehensively to achieve better countermeasures.Although in addition to underwater acoustic detection methods, anti-submarine detection methods are also available using optical, radar, infrared, magnetic field and other search methods, but from the beginning of World War II until the 21st century before Helena crossed, underwater acoustic detection methods were the most widely used in anti-submarine warfare. means of detection.Correspondingly, improving the submarine's underwater acoustic countermeasures is also the basic work for improving the submarine's survivability.

In order to improve the submarine's underwater acoustic countermeasures, it is first necessary to reduce the noise generated by the submarine when it is sailing.This is not only related to the range of the passive sonar of the enemy, but also the range of the passive sonar of the own ship.If the submarine is beating gongs and drums when it is advancing, not only the opponent's passive sonar can find you at a further distance, but the passive sonar of the submarine itself will also be interfered, resulting in a reduction in the range of action.Conversely, the situation would be reversed if the sub was as silent as a feline as it advanced.Therefore, the level of the noise level of the submarine is like a seesaw, which determines whether the information acquisition capabilities of both parties will be upgraded or lowered by you, and its importance is self-evident.

In the last plane, the countries did not have a deep understanding of the importance of reducing the noise of submarines at the beginning, so the submarines designed by Germany at the beginning of World War II did not give much consideration to reducing noise until the XXI type developed in the late World War II And on the Type XXIII submarine, the Germans began to consciously take some measures aimed at reducing noise, but it was too late.So after learning the experience and lessons from the previous plane, Helena adopted some simple and effective noise reduction measures on the Type II submarine.

The first noise reduction measure is to optimize the shape of the boat and reduce hydrodynamic noise. The cigar-shaped line used by the Type II submarine is originally a good hydrodynamic shape. At the request of Helena, the designers further improved the distribution of the inlet and outlet ports, reducing the protrusions on the surface of the hull, such as cuts. Lost the deck gun that is basically useless in the future.These measures make the water flow through the surface of the hull more smooth when the submarine is navigating underwater, which not only reduces noise but also reduces resistance.

The second noise reduction measure is the use of low-speed, large-diameter five-bladed ducted propellers.As one of the main noise sources of submarines, propeller noise mainly comes from the vibration of the blade itself and the cavitation phenomenon caused by water flowing through the low-pressure area.By increasing the diameter of the propeller, reducing the speed of the propeller, increasing the side slope angle of the propeller, and increasing the camber of the blade, the propeller noise of the Type II submarine has been significantly reduced compared with the conventional three-blade propeller.

In addition, the designer also added a circle of ducts to the propeller of the Type II submarine, but this is not a legendary pump jet design, it is just a circle of ordinary pipes, which will be used on shallow sea and inland river ships in later generations. The kind you see often.The function is to improve the efficiency of the propeller at low speed and prevent the propeller from being damaged by foreign objects when the submarine is active in shallow sea. In addition, the duct also has a certain effect on suppressing the noise of the propeller.

In fact, before this, Helena had tried to manufacture a more advanced seven-bladed large-slope propeller.However, the test shows that the cavitation noise of the propeller is reduced, but the noise caused by the vibration of the blades is increased, and the result is that the overall noise intensity is not significantly reduced.According to the analysis of technicians, the reason for this situation may be due to insufficient machining accuracy, and the blades of the seven-bladed large-skew propeller are relatively thin, which causes the propeller to be affected by eccentric force and exciting force during operation.

However, Helena was not only not depressed by the failure, but actually showed such a smile, because this thing was originally a ticket for Helena to know it was impossible.

You must know that the processing of seven-blade large-slope propellers in later generations generally requires large-scale multi-axis linkage CNC machine tools. However, Konrad Zuse has not even come up with the first electromechanical programmable computer in history. Von Neumann has not yet completed the basic theory of electronic computers. As for CNC machine tools and so on, they are far away from each other, and they cannot be developed in a few decades.However, Helena's purpose is to prove that seven-bladed large skewed propellers cannot be produced in this era, so as to satisfy her own bad taste as a time traveler.

The third noise reduction measure is to mount the submarine's noise source on an elastic base.In order to prevent the vibration generated by diesel engines, generators and electric motors from being transmitted outwards, these facilities are not rigidly connected to the hull, but are installed on a steel wire rope vibration-absorbing base.Of course, the vibration reduction effect of this measure cannot be compared with that of the vibration-damping floating rafts of later generations (the vibration-damping floating rafts of the 21st century have begun to use electromagnetic fields as damping to completely isolate the floating raft from the hull), but the wire rope shock absorber The advantage lies in its simple structure, small footprint, no fear of high temperature, no fear of engine oil, and most importantly, low price.

The fourth noise reduction measure was commonly used in the last plane XXIII. A 4 mm thick rubber layer is laid on the hull. This method can reduce the noise transmission of the submarine itself and weaken the reflection echo of the enemy's sonar. With a certain effect, it can be regarded as the prototype and predecessor of the anechoic tile in later generations.

Through the above means of reducing noise, the quietness of the Type II submarine is far ahead of the times, and the most important thing is that the cost of these improvement measures is not high.This is the advantage of "picking the low fruit first" of a technology in its infancy, and only needs some inconspicuous improvements to obtain huge benefits.Now Helena only needs to make some low-cost improvements to the submarine to raise the level of quietness to a higher level. A drop of a few tenths of a decibel.

In addition to the passive countermeasures of weakening the sonar reflection echo and reducing the sonar strength of the own ship, Helena also added some basic active countermeasures to the Type II submarine.This so-called "active countermeasure" is actually quite shabby. Type II submarines can throw "air curtain bombs" through the launch tubes on the boat when necessary. The cylinder of the potion, after a while out of the sub, will start to generate a lot of air bubbles for a while.

The role of the gas curtain bomb is first to cover the noise of the submarine itself, so that the local passive sonar is covered by noise; secondly, to generate a gas curtain in a certain direction of the submarine, temporarily blocking the detection of the enemy's active sonar.Since the Type II submarine's own noise reduction work is relatively well done, the effect of the air curtain bombs will also be more effective.

Helena believes that after combining the above active and passive underwater acoustic countermeasures, the Type II submarine is like a very slippery loach for the underwater acoustic detection equipment that appeared on the previous plane during World War II. An existence that is not easy to grasp.If British surface ships want to effectively deal with such an opponent, if they only want to rely on their numerical advantage to win, it is completely futile. Apart from bringing more casualties to their own side, it has almost no meaning.

Chapter 189 Unexpected Exchange