The military-industrial scientific research system of the academic master.

Compared with their predecessors who sailed on the water surface most of the time, modern submarines, especially nuclear submarines, rarely surface during normal mission procedures.

Therefore, all aspects of performance are focused on optimizing underwater performance.

If noise and reactor load issues are not taken into account, the Long March 9 can reach a theoretical maximum speed of about 24-25 knots underwater.

But even for Seawolf-class or Type 945 attack nuclear submarines that represent the peak level at the end of the Cold War, if they sprint at maximum speed, it is basically equivalent to driving a train underwater.

Not to mention that the 09IV itself is not a strategic nuclear submarine known for its speed and quietness.

No vigilant submarine commander would do that.

In fact, even sailing at a relatively safe depth of 19 meters at a speed of 210 knots now makes most crew members who are accustomed to crawling at a relatively low speed a little nervous.

"Old Han."

The political commissar Xiao Songhao opened the round rear hatch, crouched down and entered the command cabin, and said to Han Xiangjie:

"I just came back from the engine department, and I think the noise from the cooling pump is a bit too loud. What do you think? Should we reduce the steam pressure in the secondary circuit and raise some of the core control rods to alleviate the problem?"

These words caused Fan Chaohui, who had also just entered the command cabin not long ago, to look up and give him a strange look.

In the organizational sequence of the People's Army, the political commissar is of course one of the main officers involved in the command, and is by no means an unimportant role who "only takes care of life". But usually, due to differences in the division of labor, the higher the level and the more technical the political commissar, the less professional he is in command as the military chief.

But the image of Xiao Songhao is completely different.

Relatively speaking, it seems that he also assumes some of the responsibilities of the deputy captain.

That is to remind you of some precautions when necessary.

Han Xiangjie seemed to have noticed the other party's reaction.

He sat up slowly, but did not respond to Xiao Songhao's question immediately. Instead, he explained to Fan Zhaohui first:

"Old Xiao worked in the engine department in his early years, and later switched to a political work position. He is more familiar with some technical details than I am..."

As soon as Xiao Songhao finished speaking, he heard the captain bragging about himself to outsiders, and he was in a dilemma for a moment.

But submarine command is a serious matter after all, so he waved his hand:

"Don't be too quick to flatter me. With the noise we are making now and the fact that we will be operating in this sea area for a long time, if there is a distant-water fishing boat or destroyer using towed sonar within a few dozen nautical miles, they may detect some anomalies."

Seeing that the other party kept asking this question, Han Xiangjie quickly put away his smile and answered seriously:

"Even if the enemy destroyer reacted, it should be on its way at high speed. It is impossible for it to put down the towed sonar that would get in the way... And if it only relies on the hull sonar, it is impossible to hear too far away."

This is indeed a fairly sufficient reason.

However, Xiao Songhao still frowned:

"But Lao Han, caution is the lifeline of a submarine commander. This is what you keep saying..."

Han Xiangjie couldn't help but look a little embarrassed when someone used his catchphrase to teach him a lesson.

But he made this seemingly risky decision after careful consideration:

"Besides the fact that the enemy cannot use towed sonar, I wonder if you have noticed, Old Xiao, that between us and the approximate location of the enemy's destroyer fleet, there happens to be a rather complex sea ridge and sea hill."

Xiao Songhao nodded, with a look of bewilderment on his face:

"That's true according to the data, but...what impact will this have? We can't dive deep enough to take advantage of the seabed topography..."

For the Chinese submarine force, which spends most of its time operating within the first island chain, dealing with and utilizing complex underwater terrain is indeed a unique skill.

But even the shallowest spot nearby has a water depth of nearly four digits. Except for some verified monsters during the Cold War, it is impossible for anything to withstand such outrageous water pressure.

"Before setting sail, I specifically checked the hydrological conditions in this area and noticed that between March and May each year, due to the continued effects of ocean currents, wind fields, eddies and Rossby waves, active high-frequency ocean fronts that were originally only distributed along the California coast would spread to the eastern Pacific Ocean."

"so?"

Xiao Songhao has now realized that the captain, who has always been upright, now has the leisure to keep him in suspense, which must be a safe enough trump card.

So they also cooperated with each other's performance.

"According to the results of geoenvironmental research, mesoscale ocean phenomena such as internal waves or ocean fronts can cause an additional loss of about 20-30dB in sound propagation."

Han Xiangjie, who had received cooperation, showed a satisfied expression and continued:

"In this case, it wouldn't be too risky for us to go a little faster. On the contrary, if we delay for too long and let the enemy cross the ocean front area in the middle, it would cause greater trouble..."

This time, it was Fan Chaohui's turn to be shocked:

"Old Han, do you still understand these?"

In his impression, even when he was studying at the Naval Academy, he was not good at academic performance.

Now it seems like after three days of absence, it is time to look at him with new eyes.

"That is……"

Han Xiangjie had been laying the groundwork for so long, waiting for this moment:

"It's a new era. If the commanders of the people's army want to win battles, they must not only rely on courage, but also be good at using their brains..."

Fan Zhaohui could tell at this point that his old friend was just trying to show off in front of him. Although he was happy for him, he pouted and changed the subject...

Number one

"Let's not talk about that for now... Actually, I wanted to ask you a few hours ago, even if you really reach the target waters, how do you plan to search for the target?"

He looked towards the right rear of the shell.

"We can't surface, and we don't have any aviation equipment... Although the UUV has a camera, it is wire-guided after all, and its range of action is quite limited. To ensure safety, we can probably only stay here for less than two hours... We can't use active sonar, right?"

Active sonar has enough accuracy to detect even some medium-sized marine life.

The only problem is that any target with passive sonar on will be able to detect you half the time, just like radar.

But electromagnetic waves propagate at the speed of light, so these don't matter at all. The speed of sound in water is only 1.5 km/s, so being half the time in advance usually means a time window of minutes, which is no different from suicide.

Therefore, the active sonars on submarines are all high-frequency models, which are used for close-range collision avoidance and are not suitable for large-scale searches.

Xiao Songhao, who had been standing at the back, obviously knew the answer to this question. He did not continue to listen, but turned around and prepared to leave again:

"I'd better go to the engine room and keep an eye on it for a while, and bring some food to my comrades..."

This submarine has not yet been officially put into service, and most of the people on board were transferred from old-model nuclear submarines. Therefore, although there is sufficient sensor data, they are often accustomed to personally monitoring various key positions.

After watching the political commissar leave, Han Xiangjie shook his head and explained again:

"Using active sonar to search such a large sea area is no different from a blind cat catching a dead mouse. However, we can detonate a small mine at a specific location, use the sound waves generated by the underwater explosion as the search source, and let the submarine listen at a certain distance. Then, through triangulation, we can find some relatively large floating objects on the water surface... This is actually a trick we learned from the Americans..."

"..."

Fan Chaohui was so shocked by this slightly crazy idea that he was speechless for a moment.

But if you think about it carefully, it makes some sense.

As long as what happens on the high seas and oceans does not pose a threat to shipping routes, no one can say anything.

What's more, the enemy fleet was more than a hundred nautical miles away and it was impossible for it to notice a small explosion.

Cutting the Gordian knot is more efficient.

"All right……"

Fan Chaohui did not raise any objections:

"So…when do we start laying mines?"

Han Xiangjie looked at the other person with a slightly strange look, and then glanced at the submarine clock next to him:

"About... twenty minutes ago."

"???"

Fan Zhaohui almost couldn't catch his breath when he heard this -

So you have already finished everything?

"You were still resting in your cabin at that time, so I didn't bother you..."

Han explained to Jie.

Fan Chaohui was aware that he was only responsible for the two additional payloads in this mission and was not responsible for the command of the submarine itself, so there was really no reason for others to specifically notify him.

At this time, Han Xiangjie looked at the submarine clock again:

"Tilt forward 10 degrees, rise to a depth of 90, turn to a direction of 340 degrees, and monitor the sonar side array!"

As new orders were issued, the atmosphere in the command cabin, which had been relatively relaxed, suddenly became tense again.

Fan Chaohui immediately stopped talking and ran to the side to prepare to separate the UUV.

Given his relationship with Han Xiangjie, they could chat as they pleased, but when it came to combat command, it was better not to disturb each other casually.

After about 15 minutes of silence, Fan Chaohui heard a clear voice.

"Boom-"

It was as if someone had taken a small hammer and knocked on the hull from the outside.

Obviously, it was the main sound wave after the mine explosion that hit the submarine.

The reflected sound waves will be relatively slower due to the distance.

And the intensity will be much weaker, at least it cannot be heard directly by human ears.

The next half minute or so seemed like an eternity to Fan Chaohui.

After all, the results of this detection will determine whether he can catch something interesting or can only take some water samples to go back and argue with the Americans.

"Captain."

Finally, the sonar chief's voice came:

"After eliminating several targets that were judged to be schools of fish, there are still two suspicious echoes on the water surface. However, because the sound waves produced by the explosion of a mine are relatively rough, the specific shape of the floating objects cannot be determined for the time being..."

Now, before Han Xiangjie could answer, Fan Zhaohui stood up:

"The UUV is ready and can detach by self-propulsion at any time!"