The periscope only rose above the surface of the sea for about half a year, but the antenna rose even higher. The waves obscured the periscope's tracks, and before it was discovered, Wen Haomao withdrew the periscope.

"The telegram has been sent." When Wen Haomao observed the situation on the sea, the second mate had already sent a telegram.

"Dive to 60 meters and push at full speed." Wen Hao took a breath, "Adjust the course to 120 degrees." If there is a listening radio on the US battleship, then our position will be exposed, so get out of here first. ”

"The first ten, the last five!" The chief engineer quickly gave a specific order, "All the aircraft advance, heading 120." ”

The two propellers spun at 70 revolutions per minute, and the submarine was rapidly diving. In a short time, the listener heard the sound of the destroyer passing on the sea, but instead of following the submarine, he went in another direction. Then, the "crashing sound" of the sonar also appeared, but the US destroyer found the wrong direction and failed to spot the Project 542 submarine.

This is one of the great advantages of the "D" type submarines, which can reach a maximum underwater speed of 18 knots and can sail at this speed for four hours, while the "C" type submarines have a maximum underwater speed of less than 10 knots and can only sail for a maximum of two hours. On the surface, this improvement is not very obvious, and it can run dozens of nautical miles at most in four hours, and finally it has to float up to recharge, but in actual combat, especially when avoiding enemy destroyer attacks, the underwater speed advantage of the "D" type submarine is quite obvious.

Submersible capability has always been the ultimate goal pursued by submarine designers in various countries, but before the advent of nuclear power, the underwater navigation ability of submarines was quite limited, and most of the time, submarines can only sail on the surface of the sea, and try not to use batteries, but to use diesel engines. It can be said that during World War II, submarines spent 95% of their time on the surface. Only in combat, as well as in evading enemy destroyers, as well as attacks by anti-submarine patrol aircraft, and when the sea conditions are so bad that submarines cannot navigate on the surface of the sea, will they dive under the surface and propelled them with batteries. However, for any submarine, the time to dive under the surface of the sea is quite limited, and most submarines sail at a quiet speed of 4 knots. At most, I will spend a day or two under the surface. In the same way, any captain is not satisfied with the submarine's ability to sail, and always hopes that his submarine will be able to sail faster and longer under the surface, preferably without the need to surface for ventilation throughout the combat operation.

Before the advent of nuclear power, the only way to improve the submarine's ability to submerge was to install more batteries, and use better batteries. The Germans were the first to use their brains on the battery, and it can be said that the Germans were quite ahead of their time in their thinking, in 24 years. German engineers came up with a rather avant-garde. The basic technology, which will only have a value after decades, is the use of electricity generated by the reaction of hydrogen and oxygen to provide electricity for submarines, and this is the most basic concept of "fuel cell". If such a "fuel cell" can be made. Then the submarine can carry hydrogen and oxygen to the surface of the sea for a long time. However, the problem was that the technology at that time could not make such batteries that were ahead of their time, and the easiest way was to develop batteries with better storage capacity as much as possible. In this respect, too, Germany is ahead of the rest of the world.

The battery used in the "D" submarine was imported from Germany, and Germany did not want to provide the manufacturing technology for the battery, so it promised to export the finished product to the Tang Empire, and the negotiations lasted for several months. As a result, the scientists of the Don Empire took advantage of these months, as well as several samples obtained from Germany. The technology was thoroughly understood, and a better performance battery was developed, and Germany also agreed to use the battery at this time to exchange other technologies with the Tang Empire. Of course, the core technology of the battery is German, and for the submarines of the Tang Imperial Navy, it has finally obtained a power technology that can greatly draft the submarine submarine submarine capability, and this progress is of great significance.

The submarine's submersible speed, as well as its ability to sustain submarine, are critical in combat, especially when evading enemy attacks. The speed of submarine, as well as the ability to continue submersion, even determine the survival of the submarine, and the life and death of the submarine's officers and men. This reason is very simple, the submarine will definitely make an emergency dive after it is exposed, and the speed of any submarine emergency dive is about the same. In the same way, it takes a certain amount of time for the enemy's anti-submarine forces to rush over, and judging from the operational statistics, if it is a sneak attack, the time for the destroyer to rush over is about half an hour. During this half an hour, the submarine will certainly evade the enemy destroyer at the fastest submersible speed. If its maximum diving speed is 10 knots, it can run 5 nautical miles in half an hour, while enemy destroyers will have to search in a circular sea area with a radius of 5 miles, which is about 80 square nautical miles. If the fastest speed of the submarine is 18 knots, it can go 9 nautical miles, and the enemy destroyer will search within a range of about 250 square nautical miles. Therefore, this requires at least three times more search time, and within this time, the submarine can escape to a farther place, and the enemy destroyer needs to search for a greater range. Purely theoretically, the range of the enemy destroyer's search for a submarine is directly proportional to the square of the submarine's maximum diving speed, that is, the chances of the submarine being found by the enemy destroyer are inversely proportional to the square of its maximum speed. Obviously, the benefits of increasing the maximum submarine's submarine's speed are significant. And the time it takes to be able to sail at its maximum submersible speed determines how far the submarine can go, and the farther it goes, the safer it is.

Wen Haomao is very aware of the performance of his submarines, and at the same time he is glad that he stopped commanding the "C" type submarine half a year ago, and if he still uses the "C" type submarine this time, I am afraid that he has been killed by the US destroyer by now. The others had the same thoughts, especially when they heard the sound of the sonar impact getting weaker and weaker, and everyone was thanking the submarine and at the same time relaxing, once again there was no danger.

"The enemy destroyer has left!"

"Keep the current course and reduce to a quiet speed." Wen Haomao did not immediately change course, and after the chief engineer gave the order, he called the chief engineer, the second officer, and the chief gunner to the navigation table.

The submarine's nautical table is located next to the aisle between the command cabin and the bow torpedo compartment, and the world is just a table against the wall, on which are placed nautical charts wrapped in plastic film, as well as some drawing tools.

"This is the course of the American fleet, judging by the results of the first observations. There should be aircraft carriers, and two more, or even more. Wen Haomao used an oil paint pen to draw the course of the US fleet on the chart, "The speed is only more than 10 knots, and I don't have time to calculate it carefully, but it will not exceed 15 knots." ”

"That's a little slower than their normal cruising speed." The chief engineer frowned slightly, and the cruising speed of US warships was above 16 knots.

"There must have been damage to the warship, and any task force in the Fifth Fleet has three aircraft carriers. Judging by the actions of the American destroyers, now the American fleet is retreating, and perhaps, their battle with the 4th task force is over. "I wonder if the telegram we sent will be of any help, and if the battle is over and Task Force 4 is unable to continue the attack, then our telegram will not be of much use." ”

"We can only rely on ourselves!" The gunner's words were more direct, "Don't expect the Fourth Task Force, maybe General Huang Xiaotian is thinking about how to return to Apra Harbor now." Can we get in touch with the other submarines? ”

Wen Haomao smiled bitterly. "Now the U.S. fleet is already retreating. Even if you can contact other submarines. It is also impossible for them to arrive in time, and judging by the current situation, maybe only one of our submarines is here. ”

"Eight torpedoes......" the chief engineer sighed. It's not a good job.

"Eight torpedoes can also take out two aircraft carriers!" The gunners were a little unhappy, "At least we can't return with these eight torpedoes!" ”

"We'll think about that later." Wen Haomao did not let several main assistants argue, "The key problem now is that our position is not very good, and judging from the actions of the US fleet, we are now heading in the direction of Necker Island, and we must seize a better position." ”

"It's better to fire torpedoes from a safe distance!" The chief engineer apparently didn't have much interest in the adventure.

"I'll think about this, at least 650 torpedoes won't let us down." Wen Haomao hesitated for a moment, and then marked a new location on the chart, "Based on the return of the Fifth Fleet to Necker Island." Its basic speed is below 15 knots, and in 15 knots, we must rush to this sea area within four hours, and then wait for the arrival of the Fifth Fleet, if possible, try to shorten the attack distance, and immediately retreat after completing the attack, if not, then we can only launch torpedoes at a long distance! ”

The other three all nodded. This is the most reasonable tactical arrangement.

"Now enter the combat mode, adjust the course first, and check the status of the torpedo at the same time, I don't want to encounter another torpedo that doesn't explode!"

The order was swiftly given, and the submarine continued to sail below the surface for an hour before coming to the surface, and then proceeded to the predetermined interception point at the fastest surface speed. The surface speed of the "D" type submarine can get 18 knots, which is a little faster than the US fleet, and it can also go around to the front of the US fleet.

Wen Haomao did not let his guard down, he increased the number of lookouts to 5 people, and added one officer. He didn't know if the telegrams he had started had been received by other submarines or warships, but in fact, he had lost much hope. Perhaps several other aircraft carriers of the Fifth Fleet have been sunk by bombers from the Fourth Task Force, and the Fourth Task Force has also suffered heavy losses and has now withdrawn from the battlefield, and the only submarine with the number 542 can continue to fight on the battlefield. And the only hope that Wen Haomao hopes for is that the remaining eight torpedoes will not have any problems, and one will explode accurately!

The 650 mm heavy torpedo was a new product of the Imperial Navy, and its technical basis was the Japanese "Spear" type oxygen torpedo, but it was not exactly the same as the "Spear", and its main improvement was to increase the safety of the torpedo, such as the use of a thicker, and one-time casting oxygen container, instead of inferior welded oxygen cylinders. In addition, the results of the swash plate engine have been improved, the utilization of oxygen has been improved, and a better propulsion system has been used. This allowed the maximum range of the 650 torpedo to exceed 8 nautical miles, which was about double the previous torpedoes. But in real combat, such a long range is not of much use, and in the absence of a guidance system, the accuracy of the torpedo at a distance of 3 nautical miles is already so bad that you can only pray for luck. In addition, it is also difficult for submarines to spot warships a few nautical miles away, especially at night when submarine combat time is most concentrated, and it is quite good to be able to see warships 3 nautical miles away. Therefore, the ultra-long range is largely of little use. Later, the Imperial Navy made an improvement to the torpedo, that is, the torpedo can be set to two different carriers before launch, and the maximum range can be achieved when using low speeds, and when attacking close targets, high speeds close to 70 knots can be used, which greatly shortens the attack time and improves the hit rate, perhaps, this speed is the most important.

Another major improvement of the 650 torpedo is its detonation system, the detonator. Originally, the torpedoes of the Imperial Navy used magnetic proximity and collision fuzes, but magnetic fuzes were very unreliable and easily affected by the surrounding environment and even the latitude of the combat sea area, and the collision fuzes were full of problems, and the angle was slightly worse and could not work normally. Thus, in the first years of the war, the dud rate of torpedoes fired by the submarines of the Imperial Navy turned out to be more than thirty percent, that is, a third of the torpedoes did not explode, thus missing too many opportunities. There are not many ways to improve torpedo fuses, although many people have come up with many whimsical methods, and some even think of using the noise of enemy battleship propellers to detonate torpedoes, but the most effective and reliable are still magnetic and impact two detonation methods. The Type 650 torpedo has made a lot of improvements in this regard, and its dud rate has been reduced to less than 10%, but this is still not satisfactory.

At least Wen Haomao was very dissatisfied with the dud problem of the 650 torpedo, just more than ten days ago, he missed a 10,000-ton ship, when he obviously saw the torpedo hit the freighter, but he didn't hear the sound of the torpedo explosion, nor did he see the freighter sink, and the biggest effect of this torpedo was to frighten the American sailors on board when it hit the freighter, and at the same time attracted a destroyer, almost letting Wen Haomao go to be the companion of the dragon king.

The submarine was sailing rapidly, and Wen Haomao did not know that the telegram he sent would attract a fleet, a fleet that was not so strong but almost made him mistake.