The Monster in the Pipe
KSS-III Batch-III (4) +22
Kugugugugung—!
The massive twelve-cylinder diesel engine roared to life.
The heart of the 3,000-ton submarine had finally begun to beat.
Under normal circumstances, the force of that hulking machine should have rattled through the steel deck and tickled the soles of my feet.
But then—
Clink.
The water in the glass I’d set on the railing.
The surface remained smooth as a mirror.
Even with the engine running, not a single ripple disturbed it.
“Hah. Well, I’ll be damned.”
Go Kwangsoo, the production director, let out a dry laugh.
He rubbed the railing with his palm as if he still couldn’t believe it.
“Even with the distance from the engine room, this is still too quiet. Does this even make sense?”
“The vibration values on the instruments are converging on zero. Within the margin of error—no, there’s just nothing there. I thought the sensor had broken.”
The ADD researchers murmured among themselves, tapping at the monitors.
To them, it must have looked like a miracle. To me, it was only the inevitable result.
Red explosive energy filled the engine room.
That ferocious force had been trying to run wild through the piping and frame, but the moment it met the thin plates I’d installed and the precisely aligned shafts, it dissolved into a gentle blue current and scattered away.
Perfect dispersion.
The energy wasn’t trapped or colliding anywhere; it flowed smoothly along the intended path, keeping both noise and vibration to a minimum.
“At this point, there’s nothing left to check.”
Colonel Choi, head of the Navy’s acceptance evaluation team, nodded in satisfaction.
“Let’s begin the S.A.T. tomorrow. We’ll head straight out to sea.”
*
The situation was over.
Once the tension drained away, exhaustion hit me all at once.
I left the engine room and threw myself onto the sofa in the temporary office I’d been assigned.
“I want to go home...”
I was so tired that at this point I didn’t care about submarines or anything else. If I could just take a hot shower and crack open a beer, I’d have no complaints left in life.
The lawn back home was really nice.
If I could sit there, run my bare hands over the grass, and stare up at the sky, wouldn’t that be real paradise?
Thinking that, I lay back on the sofa and closed my eyes.
Then, all of a sudden, I heard a knock.
“Come in.”
The door opened, and an elderly gentleman with a dignified bearing stepped inside.
He was dressed simply, with no attendants in tow.
Yet the moment he entered, the air in the room seemed to sink under a strange, heavy pressure.
As I hurriedly got to my feet, the old man said, “You must be Executive Director Baek Gunwoo? I’ve heard a great deal about you.”
“And you are...?”
The old man smiled faintly and handed me a business card.
I took it on reflex, then straightened almost instantly.
Park Jincheol, President of the Agency for Defense Development (ADD)
The summit of South Korea’s defense industry.
Hanseo Defense, Taeseong Heavy Industries, Solaris Marine...
No giant defense company could sell a single weapon without this man’s approval stamp.
In the defense industry alone, he was practically absolute power.
“Ah, y-yes, sir! Baek Gunwoo of Hanseo Defense!”
“No need to be so stiff. I hear thanks to you, our country’s weapons are selling like hotcakes overseas. I only stopped by to express my gratitude. No need for formalities.”
President Park chuckled loudly as he plopped down on the sofa opposite me.
Watching him, I could only swallow hard.
Come to think of it, he was far more formidable than even Chairman Cho of Hanseo Defense. How was I supposed to act relaxed in front of a man like that?
While I stood there awkwardly, seriously wondering how I was supposed to survive this conversation, Park asked, “Am I making you uncomfortable?”
“N-not at all!”
“Then sit down. Let’s talk comfortably.”
I carefully sat back on the sofa.
Park nodded with obvious satisfaction and said, “What’s really making me happy these days is the KAAV-II project. The Philippine side is incredibly enthusiastic, you know? Thanks to the design you put together so brilliantly, we’re doing our nation proud. I’m sure your name has come up more than once in reports headed to the Blue House.”
“...Is that so?”
“Of course. If you’d been one of our ADD employees, I’d have told the others to carry you around on their backs.”
Park burst into hearty laughter.
At first glance, he’d seemed like a difficult, prickly old man, but now that we were actually talking, he felt oddly approachable.
He was boisterous to the core, the kind of big brother who made you feel safe the moment you got close to him.
Thanks to that, my own nerves loosened a little too.
And the words that slipped out of my mouth became a little easier as well.
“Haha. You’re too kind, sir. Honestly, if I were ten years younger, I’d have tried applying to ADD. Isn’t it the dream workplace for engineers?”
“Kwahaha! Is that so? Well, it’s not too late even now. I’ll make a special opening for you if you want to come over. Salary-wise, I can’t match Hanseo, but I can give you the prestige.”
“Oh? Then I suppose I should give it some thought.”
We traded light jokes back and forth, but Park’s eyes were sharp, scanning me the whole time.
It felt less like he was being friendly and more like he was testing whether I was a long-term piece worth keeping on the board.
“Truthfully, you’re very tempting. We spent months chasing a vibration issue we couldn’t pin down, and you solved it in one day... do you have any idea how shocked I was when I heard?”
“I just got lucky.”
“Lucky my ass. That was skill. Would it be all right if we asked for your help again from time to time? We need engineers as capable as you.”
“Of course. Just call on me whenever you need me.”
A connection with the ADD president.
That was an excellent card for both the company and me.
Just as the atmosphere was turning warm and friendly—
Bang.
The door swung open, and Senior Manager Seo came in with a pale face.
He froze the instant he saw President Park sitting on the sofa.
He looked like a rabbit that had wandered straight into a tiger’s den.
“Senior Manager Seo? What’s with your face? Did something happen?”
Park’s gaze turned razor-sharp in an instant.
The easygoing old man from a moment ago was gone.
Seo bit his lip, caught between anxiety and fear.
“President... and Executive Director. We’ve got a problem.”
“Did the vibration spike again?”
“No. The pipe vibration has been completely eliminated. The instruments are still at zero.”
“Then what’s the problem?”
Seo wiped his face with a trembling hand and spoke with obvious strain.
“There’s a sound. A very clear, very pure... something like a whistle.”
*
The engine room was silent.
No— it was supposed to be silent.
But I could hear the sound just as clearly.
Woooooong—
It was like someone was rubbing the rim of a giant wineglass with a wet finger.
A clean, transparent single tone hovering around 440 hertz.
Because there was no mechanical rattle from the pipe itself, the sound felt even more grotesque.
“We checked every sensor we had. There’s no vibration source. The pump, the motor, the pipes—everything’s normal. But the sound only exists in the air. I’m losing my mind.”
Seo reported the situation through clenched teeth.
President Park’s brow furrowed too.
This was something far beyond common sense.
I slowly looked around.
Most of the piping flowed in stable blue curves.
While I wandered through the submarine with Park and Seo, talking quietly as we inspected the interior, something strange caught my eye.
In a corner, there was an emergency bypass line that normally went unused.
Inside that pipe, where the valve was shut and no water flowed, a bright red mass of light was ricocheting back and forth between the two walls at insane speed, like a ping-pong ball.
A standing wave.
Concentrated energy was amplifying itself and screaming.
That was the source of the noise.
“There it is. The bypass line.”
Seo looked where I pointed and shook his head.
“Executive Director, that’s a dead pipe. All the valves are shut, and no water flows through it. If there’s no flow, how can it make a sound?”
Then President Park, who’d been standing with his hands clasped behind his back, stepped forward.
“Senior Manager Seo. What’s the diameter of that pipe?”
“Huh? Ah, it’s two inches, sir. Fifty point eight millimeters.”
“The main line velocity? Around one point five meters per second?”
“That’s right, but...”
Park glanced up into the air for a moment, thinking, then clicked his tongue softly.
“Exactly. The Strouhal number converges on 0.2.”
“...!”
“As the fluid passing through the main pipe goes by the mouth of that dead line, it forms vortices, and by sheer bad luck, the frequency matches the pipe’s natural resonant frequency.”
“Ah...! Flow-induced resonance!”
Seo’s mouth fell open.
Park snapped at him coldly.
“It’s a design flaw. You missed the vortex-shedding frequency calculation. That pipe’s length is practically perfect for resonance. You built a flute and called it a pipe.”
Was this really the ADD president?
He saw the phenomenon and immediately pierced through to the theoretical basis behind it.
And the Strouhal number, too.
That complicated number describing how often a fluid forms vortices as it passes an object—he’d mentally calculated it on the spot.
The man was a monster.
Even as I stood there in admiration, Park continued, “There’s only one solution. Break the resonance. Change the pipe length or alter the inlet shape. Cut it out now.”
At his order, Seo’s face went ashen.
“P-President. We’re leaving tomorrow. If we cut the pipe now, we’ll have to drain the system and start over... it’ll take at least three days. We’d have to delay the schedule.”
“Then you want to take a defective product out to sea? Whether it takes three days or thirty, do it by the book!”
The atmosphere froze.
Park’s words were technically flawless.
But in practical terms, they were a disaster.
A delay in departure would mean being dragged over the coals by the Ministry of National Defense and the Joint Chiefs.
I quietly stepped between them.
“President, your assessment is absolutely correct. As expected, you’re incredible. To calculate the Strouhal number by mental arithmetic alone...”
“Mm. So you recognized it too? But if you did, then you also know there’s no easy way around it.”
“Changing the structure would be the proper solution. But if we have to put the ship to sea tomorrow, then... we use a workaround.”
“...A workaround?”
Park’s eyebrow twitched.
“If we can’t change the pipe length, then we change the material properties. This is something a heating wire can solve. But we need to check it quickly first, so let’s test it with a heat gun.”
*
Seo, looking half-convinced and half-dubious, started heating the pipe with a heat gun.
With a whirring sound, the hot air warmed the cold metal pipe.
His hand trembled slightly.
And no wonder.
President Park, the apex of South Korea’s defense industry, was watching him from behind like a hawk.
One minute, two minutes...
I could see it.
The red standing wave packed inside the pipe began to sag and loosen, like something suffering from the heat.
As the temperature rose and the speed of sound in the medium changed, the once-perfect resonance started slipping out of tune.
The orderly red wave collided with itself and died.
And then at last—
Woooong... wooong... thud.
The sound cut off as if it had never existed.
The red energy faded away helplessly, and the pipe sank back into cold silence.
“...”
Only true stillness remained in the engine room now.
Seo lowered the heat gun with a look of utter disbelief.
“As I said earlier, once we’re underway, just wrap it with heating wire to maintain the temperature. That should be enough for now.”
At my words, Park let out a laugh of disbelief.
“Hah... incredible. A temporary fix, but you completely understood the principle. You stopped a construction job worth billions with a heat gun?”
Admiringly, Park casually checked the overall noise meter beside him.
In an instant, his eyes widened.
He tapped the device a few times, as if wondering whether it had broken.
“Huh? Is this thing busted? Senior Manager Seo, check yours too.”
“Y-yes? Mine too... uh...?”
Seo read the number with a trembling voice.
“President. It’s 95 decibels.”
“Does that make sense? This vessel’s operational requirement is 110 decibels. The design limit is 105. And yet it’s 95?”
Park turned to look at me.
He was staring at me with eyes that clearly said he couldn’t believe what he was hearing.
“You said you worked on the piping, right? Just how perfectly did you tune the flow that the fluid noise practically disappeared?”
“Executive Director Baek paid especially close attention to making sure the new piping matched the existing system one hundred percent, sir. He even went through the trouble of adding rifling to the pipes and eliminating any play at all.”
“Huh... one hundred percent, you say?”
“Yes. That was my own conclusion after checking the entire route myself.”
“Amazing. Truly amazing.”
Park looked genuinely astonished as he spoke.
“At this point, this submarine might as well have become the sea itself.”
“The sea?”
I asked in confusion.
For the submarine to become the sea itself... did he mean it had become one with the ocean?
It sounded like praise in context, but I honestly had no idea what he was talking about.
Apparently noticing my confusion, Seo gave a quiet laugh and said, “The natural background noise underwater—waves, marine life, and the like—usually sits somewhere around 85 to 95 decibels.”
“...Huh?”
“Since the background noise and our submarine’s noise are now in the same range, people won’t be able to distinguish our sound from the ocean’s ambient noise. In the truest sense, it has become one with the sea.”
Oh...
All I’d done was give my absolute best at the job I was assigned.
“Looks like I ended up making a monster without even meaning to.”
“Haha, a monster indeed. The ship’s a monster, and so are you for making something like this. Once it goes out on sea trials, it’ll prove itself for sure.”
Park laughed heartily and patted my shoulder.
Then—
“All right, then. Now that the piping issue is solved, I’ll head back. I still need to return to Seoul and file my report...”
Honestly, all I wanted was to hurry off to a sauna and melt the tension out of my body.
But then—
“Executive Director Baek, wait a moment.”
Park stopped me. A bad feeling prickled at the back of my neck.
“Yes?”
“You’re coming too.”
“...Excuse me?”
Thinking I’d misheard him, I asked again, and Park sealed it with a smile.
“You’ll be riding along for this sea trial too.”
“No, sir. I’m a civilian. To board a military vessel, there has to be a security clearance and the proper procedures—”
“I’ll vouch for you. If the ADD president says you’re cleared, who’s going to stop it?”
Park was completely unreasonable.
Seo, standing nearby, joined in as well.
“You need to come, Executive Director. That pipe is only a temporary fix with heating wire right now. If the wire cuts out in the middle of the ocean, or the temperature slips and the resonance comes back, who’s going to stop it?”
“No, but if we just keep an eye on the temperature—”
“Executive Director Baek.”
Park’s voice sank lower.
He looked at me with absolute seriousness.
“There are unwelcome guests in the East Sea right now. The Chinese.”
“......”
“They’re itching to hear the sound of our new submarine. But what if that whistle starts up again during the sea trial? There’d be no greater international humiliation. You’ll have to see this through to the end.”
A justification I couldn’t refuse.
And to be honest... I was curious, too.
I wanted to know what kind of performance this monster I’d built would show against a foreign submarine in a real-world situation.
My engineering curiosity overrode my exhaustion.
I let out a sigh and tightened my tie again.
“...You’ll cover the overtime, right?”
At my answer, Park burst out laughing.
“Of course I will! I’ll make sure you get the full package—overtime and hazard pay, all of it!”