Chapter 790 Hawaiian Islands (11)

"Captain, the 'Sea Crucian' seems to have been sunk!"

In the distance, in another US submarine, the sonar operator showed a sad expression on his face and reported the bad news to the captain. But the next second, his face suddenly changed. "Oh no, the German destroyer is coming towards us!!"

"Damn it!" The captain did not have time to commemorate the sunken "Sea Crucian" and gave a decisive order. "Turn off the power system!!" As mentioned earlier, this is a very risky decision. Once the power system is turned off, the submarine can only move underwater. But the experience of the "Sea Crucian" warned them that if they wanted to fight the German destroyer, it would be purely courting death. He could only fight hard and turn off the power system. The entire submarine was quietly suspended in the 50-meter-deep sea water, hoping to avoid the search of the German destroyer.

Ping! Ping! Ping!

As the destroyer approached, the sound waves hitting the submarine's hull became louder and louder. The cavity effect amplified the sound, and the sailors in the submarine could hear it clearly even without sonar headphones. The sonar operator turned down the volume of the headphones in time to avoid damaging the eardrums.

Everyone was so nervous that they didn't even dare to breathe. They looked at each other and communicated with their eyes. "What is this sound?!" They had never heard such a strange sound before.

"God!!" At this moment, the sonar operator suddenly shouted. "This is active sonar! The German destroyer is equipped with active sonar!!" Then he told the people around him the principle of active sonar at the fastest speed. His uncle is an expert in sonic research and has heard about the principle of active sonar before. But he didn't expect that the Germans have successfully developed and equipped active sonar.

"What?!" After hearing this, everyone was shocked. According to the principle of active sonar mentioned by the sonar operator, even if they turned off the power system to maintain absolute silence, they could not escape the search of the German active sonar! !

The captain asked hurriedly. "Then is there any way to avoid detection by active sonar?!"

The sonar operator's expression was uglier than crying. "As far as I know, there is only one way, that is to dive into the seawater jump layer, which will cause the propagation of sound waves to refract."

The so-called seawater jump layer is a water layer where seawater parameters change significantly with depth. It refers to a water layer where the temperature, salinity, density, speed of sound and other states of seawater undergo sudden or discontinuous changes in the vertical direction.

There are mainly thermoclines, salinity jump layers, density jump layers and sonic jump layers. Thermoclines often exist in the ocean and affect salinity, density and sonic jump layers. Salinity jump layers often appear in estuaries or sea areas with a lot of precipitation, evaporation and ice melting. Density jump layers usually appear in seawater mixing, two water masses meet and fresh water flows into rivers, where water temperature and salinity suddenly change. Except for estuaries and individual sea areas with particularly large vertical gradients of salinity, density jump layers generally overlap with thermoclines. Sonic jumps are usually formed due to uneven temperature, pressure and salinity of seawater, and sudden changes in the speed of sound propagation in the vertical direction.

These jumps have a positive effect on underwater communications and submarine concealment. Sonar equipment works best in deep sound channels, and submarines sailing in deep sound channels can detect targets at a long distance. Sonar signals emitted above the sonic jump are not easy to detect targets below the jump, and the possibility of submarines diving below the jump is greatly reduced. If the seawater jump is weak, the upper boundary is deep, the thickness is large, and it is more persistent and stable, irregular sound reflections will be formed, which will greatly reduce the combat effectiveness of anti-submarine sonar and cause difficulties for anti-submarine operations.

"Shit!" They are not clear about the hydrological conditions here. If they dive rashly, they may not reach the jump even if they exceed the submarine's maximum diving depth!

Just as the captain was hesitant, the sonar operator turned extremely pale. "Captain, the German destroyer dropped a depth charge!!"

After hesitating for a second, the captain decisively ordered. "Start the engine! Drain the water tank!!"

A few seconds later, the depth charge exploded above them. The loud noise made the sonar operator scream and take off his headphones. He felt that his ears were almost bleeding, and his whole head was rumbling.

The shock wave of the depth charge explosion was as powerful as thunder, and the sea water pressed against the submarine's hull with huge pressure! The rear outer shell steel plate of the submarine could not withstand this terrible impact force, and it was instantly twisted and deformed. A big hole was cracked in the engine room. The sea water under five atmospheres of pressure seemed like a huge fist, flattening the sailors in front of it against the bulkhead. The sea water, which was instantly dyed red by blood, rushed to other cabins frantically.

"Close the hatch! Emergency surface!" The captain issued an emergency surface order. The submarine drained water and surfaced at the fastest speed, and was very lucky to avoid the rest of the depth charges. When it floated to more than 20 meters above the sea surface, the captain instructed the communicator. "When we surface, immediately send out the news that the Germans are equipped with active sonar!" Otherwise, our submarines will suffer a lot.

As he said this, he raised the periscope and saw that the guns of the German destroyers were already pointed at this side.

"I hope they can capture prisoners." The captain just prayed in his heart, and saw the guns spewing fire, and then he knew nothing.

After sinking the submarine mercilessly, the German destroyer continued to search in this sea area until it was confirmed that there were no other submarines and then sent the news back to the fleet.

"Commander, we sank two American submarines."

Commander Hermann nodded. "Strengthen vigilance and don't let them deliver supplies to the island."

Oahu has been besieged by them for eight days. And even God is on their side. In the Pacific Ocean, which was originally full of rain, Oahu only had a light rain in these eight days, which was not enough to moisten the throats of the defenders on the island. At most three or four days, these defenders will lose their combat effectiveness due to lack of water.

Another fleet sent to Midway Island easily occupied Midway Island. Although all the facilities on the island were destroyed by the evacuated US troops, they did not expect to receive these facilities intact from the beginning. The accompanying engineering team has begun to repair the airport and port on the island. It will not be long before Midway Island will become a base for the German Navy.

In the underground command post on Oahu Island, Commander Wilson once again asked a question that he had asked countless times. "Have you contacted the supply submarine?" Because of lack of water, his lips were dry and cracked, and the whole person looked listless.

The communicator replied weakly. "Commander, the supply submarine may be submerged. According to previous communications, it is already 50 kilometers away from here."

50 kilometers, even if the submarine is submerged at a speed of 5 knots, it will arrive in less than six hours.

Unfortunately, after waiting for more than ten hours, there was no news from the submarine.