Transmigrated as the Crown Prince

The German fleet anchored in the waters off Oahu, the correspondent reported to Commander Hellman. "Commander, our destroyer found a suspicious signal fifty kilometers northeast of the sea. It is suspected to be an enemy submarine."

"Are these idiots here to die?" Commander Hellman sneered and casually ordered. "Sink them!" Who else can appear here besides the US submarine?

The adjutant on the side spoke. "It seems to be a US military submarine supporting Oahu. Maybe it is sending them fresh water purification equipment. But it is just used to try out our latest sonar system."

The collision of the luxury ship "Titanic" with an iceberg in 1912 and the outbreak of World War I in 1914 greatly promoted the research and development of civilian and military sonar. The first anti-submarine sonar came out in World War I. However, due to theoretical and technical imperfections at that time, the performance of this underwater echolocation system was very unreliable, so it was unable to deal with the threat of German U-boats. has not yet contributed.

Sonar research did not end with the end of World War I. It was not until 1935 that Germany, Britain, and the United States developed several more practical sonar. In 1938, sonar equipment began to be mass-produced in the United States. In World War II in the original time and space, almost all military ships were equipped with sonar systems and played a very important role in naval battles. At that time, the warring parties lost more than a thousand submarines, and most of them were discovered by sonar. of.

"Report, the enemy destroyer is approaching at high speed!" In the underwater US submarine, the submarine sonar operator listened quietly for a few seconds and then immediately reported to Captain Thomas standing aside. They had just discovered a German destroyer patrolling in the distance. Although they dived in time, they were still discovered by the other party.

"Dive to 30 meters and reduce the speed to 3 knots! Reduce the noise!" Following Captain Thomas's order, some unnecessary equipment was turned off in the submarine to reduce the noise the submarine made in the sea. However, these noises can be said to be insignificant. The noise from the submarine's engine and propeller is the main source of noise. Unless all power systems are turned off, the probability of the other party discovering them is still very high.

But they cannot shut down all the power systems. If the enemy ships on the water do not leave by then, their situation will be even more dangerous.

On the sea, a German destroyer had approached the sea area, and the captain issued an order on the bridge. "Turn on active sonar! Find this rat!"

Sonar technology can be divided into two categories: passive sonar and active sonar according to the working method. To put it simply, dynamic sonar only has ears. It can only estimate the approximate direction of the target by listening to various underwater sounds. Active sonar has an additional mouth, shouting sounds with your mouth, and receiving echoes with your ears to determine the target distance. These two have their own advantages and disadvantages. Active sonar is accurate, but it is easy to be exposed (turning on active sonar by a surface ship is equivalent to shouting to the submarine in the water: "Hey! Brother, I am here, my position is here, Did you hear it clearly?". Vice versa); passive sonar concealed points, but cannot be measured accurately. Later nuclear submarine collisions showed that passive sonar technology still has problems.

For underwater submarines, the noise they emit when quiet is low, and passive sonar cannot distinguish the noise between the submarine and the noise in the sea. Active sonar can, because active sonar relies on specific echo positioning. Generally speaking, as long as the submarine does not land (sink to the seabed), active sonar can effectively locate the submarine.

The German destroyer turned on active sonar and began to emit mid-frequency sound waves into the surrounding waters.

Ultrasound is divided into three bands: low frequency, medium frequency and high frequency. Among them, the medium frequency has the best anti-interference ability. When using medium frequency ultrasonic for active detection, it can effectively image submarines submerged in seawater. Ultrasonic waves in the low-frequency band and high-frequency band are either far away but poor in accuracy, or high in accuracy but close in distance. They are not as suitable as mid-frequency, which has both good distance and good accuracy.

But unfortunately, this frequency band is also the physiological frequency band of most marine organisms (such as dolphins, whales and other large marine animals rely on mid-frequency acoustic echolocation for navigation and hunting activities). Although some countries in the late World War II and post-war period equipped with mid-frequency active acoustic However, it was later discovered that the use of this sonar caused blindness, internal bleeding and even death of a large number of marine creatures that relied on echolocation for cruising. Some dolphins or whales swam to unfamiliar waters and became stranded, or even washed up on the beach (that is, what people thought was a collective suicide). Therefore, the relevant United Nations animal protection organizations have formulated relevant measures to protect the safety of these marine creatures. Therefore, under the pressure of global public opinion, the military of various countries have abandoned the use of mid-frequency sonar on ships, and some countries have even stopped using high-frequency sonar. phased out.

It's a pity that now is a life-and-death war, and no one cares about the safety of those marine animals.

Ping! Ping! Ping!

Dense sound waves hit the hull of the US submarine, and the sonar operator screamed and took off his earphones.

The cavity effect amplified this sound, and the sailors in the submarine clearly heard this terrible sound.

"Continue to dive to a depth of 50 meters!" Although Captain Thomas didn't know what the Germans were doing, he was obviously not friendly and decided to do something.

Soon, the submarine dived to a depth of 50 meters, but that terrible ping! Ping! The sound is more intensive.

Because the sonar operator took off his earphones, he could not hear that the German destroyers on the water had dropped several depth charges.

boom! The sudden explosion caused all the sailors in the submarine to stagger.

The first depth bomb exploded more than ten meters to the left of the submarine, causing no substantial damage to the submarine, but the other depth bomb exploded two meters above the stern of the submarine, and a huge shock wave blew up the front of the submarine. A big hole emerged, and the sea water poured straight down.

"Drain the water from the bow! Emergency surface!" Upon hearing the damage to the stern of the boat, Captain Thomas immediately issued an order to surface. This level of damage is fatal to a submarine. If they continue to harden, then they can only go to see God; and he does not want to go to see God so early.

The submarine's sailors were well-trained, and the captain's orders were immediately implemented. As the sailors operated, compressed air poured into the ballast water tank at the bow of the boat, draining the seawater out of the bow. The weight of the bow was immediately reduced, while the tail was filled with seawater. As a result, the bow of the submarine was naturally tilted. Get up, the whole submarine surfaced quickly!

At this time, the third depth charge exploded almost against the hull of the submarine. Coincidentally, if it were an ordinary depth charge, it would only explode at the set depth. But the German depth bombs had proximity fuses. As a result, the sinking depth bombs exploded the moment they passed by the floating submarine. The severely damaged submarine was broken into pieces under the terrible impact. Two pieces, slowly sinking into the deeper seabed.