Batch-III +16
Seoul, Hanseo Defense headquarters, Technical Audit Office.
"Congratulations on your promotion, sir!"
The head of HR, who had arrived in my office before anyone else, came up to greet me with a bow.
Behind him, the HR staff were moving briskly as they replaced the nameplate on my desk.
- Department Head Baek Gunwoo
The familiar nameplate was taken away, and in its place they set down a mother-of-pearl plate that seemed to carry its own weight.
- Executive Director Baek Gunwoo
When I stood before Chairman Cho, I had taken it with the same calm feeling one had when something long expected finally arrived. But seeing the nameplate on my own desk changed like this made my chest swell with a strange sense of grandeur.
"And this is your renewed contract. It reflects the special instructions Chairman Cho gave us."
I skimmed the documents the HR head handed me.
The numbers, the number of zeroes, were dizzying.
Annual salary: Five billion won.
A pre-tax base salary of 500,000,000 won.
Project incentives and stock options were listed separately.
Of course, after taxes, it would shrink to nearly half, but compared to myself from just a few months ago, when I had not even made 100 million a year, it was nothing short of a transformation from land to sea.
"And finally, this is your corporate card."
The HR head handed me a black card with both hands, carefully and respectfully.
"What's the limit?"
"There isn't one."
"...Pardon?"
"Chairman Cho emphasized that you shouldn't skimp on maintaining your dignity. It's a black-tier card with no preset limit at all."
...Good heavens.
Without realizing it, I swallowed hard.
A card with no limit.
It was something I had never even imagined.
"Then I'll be taking my leave. If you have any questions, please don't hesitate to let me know. Goodbye."
After the HR head bowed to ninety degrees and withdrew,
I was left alone in the empty office, which now felt as spacious as a sports field.
"Hah..."
Until a moment ago, I had simply been tired.
I had been summoned back the instant I returned from Malaysia, and all I wanted was to go home, wash up, and sleep.
But staring at the contract and the black card on my desk...
My heart began to pound strangely.
My fatigue vanished in an instant, and it felt as though my brain cells were crackling awake one by one.
Dopamine was surging through my bloodstream and slamming into every part of my body.
Was I supposed to clock out after getting paid this kind of money? That would be negligence.
Sleep could wait until I was dead, couldn't it?
At that very moment, I was desperate to prove that I was worth what I had been paid.
I took out my phone without hesitation.
The number printed on the business card Chairman Cho had given me.
The moment I pressed the call button, the line connected as if it had been waiting for me.
*
An hour later.
"Good afternoon. I'm Baek Gunwoo."
"Seo Minseok, Principal Researcher at the ADD Underwater Weapons System Center."
The man seated across from me at the meeting table in my office was the textbook image of a researcher.
Thin, sharp-looking eyes, tightly pressed lips, and an atmosphere so taut it seemed ready to snap.
The instant he sat down, he pulled a thick stack of documents from his bag.
"I've heard the situation, but please understand that the procedures are unavoidable on our end as well. Please fill out the Top Secret clearance application and the security oath first."
Thud.
A ballpoint pen was placed in front of me.
"It includes clauses for referral to a military court in the event of a violation, so I recommend reading it carefully."
Seo Minseok's tone was so dry it was almost rigid.
There was none of the polite small talk or smiling one usually did when meeting a conglomerate executive.
But I didn't feel offended. On the contrary, I felt relieved.
Yes, this was right.
For a master who had spent his life shaping submarines, it was only natural to be wary of some stranger trying to step into his territory.
If someone I didn't know tried touching my blueprints, I'd hate it too.
That sort of prickliness only proved that Seo Minseok was a man confident in his own skill.
"Yes. I'll fill it out right away."
I signed the documents without a word and handed them over.
Only after Seo Minseok had carefully checked everything did he take a tablet PC from inside his coat.
"Before we begin, may I speak candidly?"
"Go ahead."
"I think the people above us made the wrong choice."
"...Pardon?"
He was saying it that openly?
Seo Minseok met my bewildered stare head-on and said, "Of course, I don't mean to dismiss Executive Director Baek's capabilities. I've heard all about the legend you made in the ground systems division. But land equipment and underwater equipment... the scale of fluid dynamics itself is different."
"......"
"I assume you can understand why I'm so skeptical. I'm sorry to say this as well, but I felt I had to."
I gave a wry smile and nodded.
He wasn't wrong.
What could a man who crawled around on land possibly know about the inside of the sea?
But.
Whether it was a submarine or a tank, in the end it was all steel and machinery.
If it got hot, it expanded. If it vibrated, it cracked. If it was trapped, it burst.
Those laws of physics did not run backward just because something was underwater.
Even if I didn't have my ability, even if I were the me from a few months ago, I would still be able to grasp at least that common denominator.
Viewed that way, it might have been a little infuriating...
But was there any need to make a fuss over it?
The man sitting across from me was probably already at the edge, his pride badly bruised by the sudden appearance of crippling problems, his mind boxed in from every side.
If such a man snapped at me a little, there was no reason for me to snap back.
"I understand. I'd probably have done the same."
My plain answer softened Seo Minseok's eyes a little.
He brought up a file on the tablet and slid it toward me.
"Then please look at this first. This is the most troublesome problem we're currently facing on the prototype submarine."
The screen was filled with complex graphs and equations.
It was damage data for the bolts securing the battery modules.
"As you can see, shear failure is occurring continuously in the mounting bolts. The bolts used are maraging steel with a tensile strength of 1,200 MPa. By all calculations of yield stress and fatigue limit, they absolutely shouldn't be breaking."
Seo Minseok continued his explanation.
"We spent six months analyzing every possibility, including fretting fatigue caused by accumulated microscopic torsional moments, or even hydrogen embrittlement in the material itself... but we still haven't found a clear cause. What do you think, sir?"
Fretting fatigue referred to the cracking and wear that occurred when the surfaces of two interlocked metals vibrated or rubbed against each other at a microscopic level.
Hydrogen embrittlement meant that metal materials, especially high-strength steel, absorbed hydrogen and lost their ability to stretch, becoming brittle and breaking like glass.
Neither explanation was worth dwelling on here.
And they weren't especially useful for solving the problem, either.
As I was thinking this, Seo Minseok was staring at me intently.
A test?
He was deliberately throwing out unnecessary terminology to confuse me.
He was trying to see whether I understood the special environment of a submarine, or whether I was just a businessman making blind guesses on instinct.
I quietly shifted my gaze to the blueprint on the tablet.
At the same time, I could confirm it.
As expected.
It wasn't a problem with the bolts.
Before my eyes, the battery module at the bottom of the submarine was swelling in a vivid red shape.
It was the force of immense thermal expansion.
Those absurdly huge forces were being borne by bolts no thicker than a finger.
Worse, the dark red bolts dying one after another looked as though their joints were being bent backward while they desperately tried to suppress a giant's thrashing.
"It's simple."
I casually flipped through the data and said, "Don't blame the bolts."
"What? What do you mean by that...?"
"The battery's overheated and it's thrashing around, so of course it blows apart if you lock it down tight with bolts. Just let it move."
I drew an oval shape on the tablet with my index finger.
"Make the mounting holes slot holes instead of round ones. And put Teflon pads on the bottom so it can slide."
"......"
"When something heats up, it expands. If you clamp it tight, it breaks. Let it slide, and once it cools, it'll return to position on its own. It's basic thermal ratcheting, but... surely the doctors here didn't call me out because they didn't know that."
I gave Seo Minseok a small smile and asked, "Are you testing me?"
Seo Minseok's mouth fell open in a daze.
I had given the answer in a single minute without even looking at the hundreds of pages of structural analysis reports.
And I had done it as if it were too easy to mention.
"...I knew it."
Seo Minseok's face flushed red.
He cleared his throat and straightened in his chair.
"Just as I'd heard. I apologize for the rudeness."
"It's fine. Verification is necessary. Shall we get to the point now?"
At my words, Seo Minseok's eyes changed.
His defensive attitude disappeared, leaving only the seriousness of a real expert facing a formidable problem.
"Yes. To be honest, what I just showed you was a test. If I offended you, then I will apologize properly and formally. But what I'm about to show you now is... the real problem we're facing."
He switched the folder on the tablet.
[KSS-III Batch-III Cooling Piping Vibration Analysis]
"It's the piping vibration. Not in one specific section, but throughout the submarine's cooling line, the whole system is out of control. The moment we start the pumps, the pipes start dancing like mad."
"What if you clamp them?"
"If we do, the resonance inside the pipes creates a wheezing whistle. It's loud enough to be picked up by sonar from 100 kilometers away. In the simulation, we can't identify a single vibration node."
The vibration node was the fixed point where the wave canceled itself out and movement dropped to zero.
I stared at the blueprint.
The coolant lines were tangled together in a complicated network.
The fluid flowing through them surged in blue pulses as it rushed along.
The trouble was at the bends and near the valves.
Every time the blue flow struck the pipe wall, dark red stress bloomed at the impact point like bruises.
It looked as if a living blue serpent were vomiting blood while squeezing the pipes to death.
"This isn't just simple vibration."
I frowned.
"This is one of the nasty kinds of flow-induced vibration. The pump pulsation and the pipe's natural frequency are getting tangled out of sync. And moreover..."
I enlarged one spot on the blueprint.
"This valve manifold layout here. Who placed it?"
As the fluid rotated here, it created vortices, and the cycle just happened to align with a whole-number multiple of the pipe length. This isn't something you can fix by clamping it down. You have to break the rhythm.
"Yo-you figured that out from the blueprint alone? We spent two full months running fluid analyses and could only barely guess at that much..."
Seo Minseok's eyes went wide.
It was natural for him to be shocked.
Even now, months after gaining this ability, I still found it shocking.
As Seo Minseok had said, to reach this kind of analysis with precision equipment alone would take a very long time.
But I couldn't exactly tell him my secret.
So I just put on a modest smile and said lightly, "I suppose the blueprint has its limits. It's hard to secure enough information that way."
I closed the tablet and stood up.
"I'll need to see and hear exactly how the piping is vibrating with my own eyes and ears. It can change depending on the installation condition and even the shape of the weld bead."
"Y-you want to go see it directly? Right now?"
Seo Minseok looked flustered and checked his watch.
It was already after 10 p.m.
"The prototype submarine is at Okpo Shipyard on Geoje Island, but..."
"Have a vehicle standing by. If we sleep a little on the way down, we'll get there by dawn."
"No, sir. I heard you just returned today, didn't I? Aren't you tired?"
Tired?
As I put on my jacket, I grinned.
The corporate card in my pocket felt heavy.
"I need to earn my pay. Let's go, Principal Researcher."
*
Geoje Island, Solaris Marine Okpo Shipyard.
We arrived there just before 3 a.m.
With the rain falling in a thin, dreary drizzle, even the outdoor dock felt grim and abandoned.
"We've arrived."
The black sedan that had brought us passed through the security gate and came to a stop in front of the dock.
Seo Minseok and I got out of the car with umbrellas.
Under the harsh floodlights of Dry Dock No. 1,
a black monster lay on the vast dock floor, where the water had been drained away.
KSS-III Batch-III.
The Republic of Korea Navy's next-generation 4,000-ton submarine, built with everything on the line.
"Wow..."
A breath escaped me before I could stop it.
Its scale was on a completely different level from armored vehicles or tanks.
It had the overwhelming presence of a giant whale holding its breath.
But I could tell.
Inside that sleek, almost beautiful mass, everything was tangled and screaming in disarray.
From here on, I was the one who had to fix it.
"All right, let's go in."
Brushing rainwater from myself, I pointed toward the stairs descending beneath the dock.
"Let's take a look at where exactly this four-thousand-ton patient feels unwell."
Seo Minseok checked his wristwatch with a troubled expression.
"It's 3 a.m., sir. And it's raining. You must be exhausted from traveling here all the way from Seoul... Let's head to the lodging first. Tomorrow morning, once the workers are in and the lights are properly set, then we can do this formally..."
"No, Principal Researcher. If we don't look now, we won't get another chance."
I shook my head firmly.
"Once daylight comes, this place turns into a battlefield."
"Pardon?"
"Grinders running, cranes moving, dump trucks rolling through. In that kind of noise and vibration, there's no way we'll solve this."
The shipyard was loud during the day.
Trying to catch a subtle fluid vibration or a pipe's tremor amid hundreds of workers cutting and pounding steel was nearly impossible.
"We need it dead quiet. Right now, when the background noise is as close to zero as possible. That's the only way we'll catch even the tiniest vibration without missing it."
"Ah..."
Seo Minseok's mouth fell slightly open.
He seemed to have finally understood what I was after.
He looked as though he were regretting that he had wanted to inspect it during the noisiest hours of the day when he had come to eliminate vibration in the first place.
At the same time, there was awe at the fact that an outsider who had just arrived was already calculating the conditions of the site itself.
"I... wasn't thinking far enough ahead. You're right, sir."
Seo Minseok bowed his head and folded his umbrella.
"I'll guide you. This way."