The Active Counter-Stress Truss
The outdoor training range was being whipped by a cutting wind so sharp it seemed to cut straight through flesh and bone.
I climbed a ladder and hauled myself directly onto the barrel of the massive K2SE tank.
The cold at minus thirty degrees slipped through my thick winter gear and seemed to sink all the way to my joints, but my eyes were fixed only on the thermal tube around the enormous, oversized 130mm main gun.
Where was the problem?
Had the band been tightened too much?
Or was the insulation assembled poorly?
As always, I was looking for some minor field mistake or some hidden flaw in the design.
But then.
“...This is...”
My prediction was completely off.
The blue lines I could see with my own eyes proved that the bands fixing the thermal tube and the joints connecting it had been assembled perfectly, with not even a one-percent deviation.
But the problem was the steel mass trapped inside that perfect bond.
“That’s troublesome.”
It felt like I’d run into an unexpected dead end.
I folded my arms, looked down at the main gun, and let out a sigh.
The horrific residual stress trapped inside the steel after being forced into a sudden chill at minus thirty degrees right after firing.
Like a burn scar, grotesquely tangled red waves were rising like heat shimmer, as if they might tear the barrel’s inner wall apart at any moment.
The reason was obvious.
The upper part of the barrel, taking the blizzard head-on, would have rapidly cooled and tried to contract in the minus thirty cold, while the lower part facing the ground would have held on to its firing heat and kept trying to expand.
The top shrank, the bottom stretched.
That extreme temperature difference between upper and lower forced the steel to bend upward, and the stress from that process remained etched inside the metal like a scar.
It was because, at Sweden’s request, the outer wall of the barrel had been shaved down to reduce weight.
That left the gun with nowhere near enough thermal mass to hold heat, and since it couldn’t distribute firing heat evenly through the entire barrel, the deformation had exceeded its limit.
The design itself wasn’t wrong, and it didn’t seem as though anyone had made a mistake during manufacturing.
Then the conclusion was simple.
With our current technology and data, it was impossible to meet, one hundred percent and perfectly, the standard demanded by Sweden’s brutal natural environment.
“Damn.”
Unlike Germany, which had been developing and operating tanks since World War II and even pushed them all the way to the outskirts of Moscow, we had only started developing tanks on our own in the 1980s.
We were short on data.
That made the situation all the more maddening.
This really was a case of making something out of nothing.
“Hah... how the hell am I supposed to handle this?”
◇◇◇◆◇◇◇
After confirming the problem, the first thing I did was go find Jo Taehyung and relay my diagnosis.
“The design is perfect. Assembly is fine, and the setup is fine too.”
The atmosphere inside the VIP tent sank heavy at my words.
Chief Executive Jo Taehyung and the doctors who had just witnessed the miracle of the suspension system.
Because of that, now that I had acknowledged the integrity of their own design instead of offering a solution, they seemed to have fallen into even deeper despair.
“So steel bends even when there’s no mistake...” Jo Taehyung muttered, pressing a hand to his brow.
“Looks like forcing the weight down to fit Sweden’s terrain really was the root of the problem...”
“That appears to be the case for now,” I said.
At present, the European defense trend, following the Ukraine war, had hardened around the preference for seventy-ton heavy tanks armored to the teeth for maximum protection.
Germany’s latest Leopard, the competition’s answer to that demand, was also a heavy beast that satisfied the market perfectly.
But our Korean consortium had boldly countered that Sweden’s many snow-covered swamps, fragile ground, and old bridges might not be able to bear seventy tons without issue, and made a bold proposal in return.
Fifty-three tons.
Strip the tank’s weight down to the limit so it could move like a flying shadow across the harsh Nordic terrain, and make up for the lighter armor by mounting a state-of-the-art Active Protection System that would intercept incoming missiles and drones. That was the next-generation asymmetric tactic we’d suggested.
In the middle of that, Jo Taehyung and the Ground Weapons Systems Command had taken a gamble to maximize our strengths: they reduced the gun’s weight while cramming in 130mm-class firepower.
“...We should have just used the existing gun instead. If we’d used a proven model, we wouldn’t be tearing our hair out like this.”
“If we’d mounted the existing model as-is, we’d have lost on firepower and handed Germany the forty-trillion-won contract without a fight. The direction was right.”
“What use is the direction being right if the steel can’t hold up and bends anyway? There’s no way out of this.”
“I think that’s something I can figure out from here on out.”
“...What?”
Jo Taehyung blinked in confusion and asked again.
“No, you’re saying you’ll start looking for a way now, when the alloy research alone would take at least a year? And you won’t give up?”
“If we can’t change the alloy, then we change something else so the steel can withstand it. Let me take a look first.”
“Hah, seriously...”
Jo Taehyung let out a dry laugh as if he couldn’t believe what he was hearing.
The other doctoral engineers with him looked just the same.
Well, that was a normal reaction.
This was a problem caused by a lack of data on a special alloy steel.
A tank main gun was also a thing that took eight months just to manufacture.
To them, I probably looked like a lunatic claiming I could solve that kind of problem here, with less than six full days left in the test period.
“When I say I need something, just make sure the support is there. I’ll get this resolved somehow.”
“...Understood. If you find a solution, I’ll have whatever you need prepared no matter what it costs. Just find a way, please.”
Jo Taehyung’s voice was trembling faintly.
Even now, half-doubting me, he was still desperate enough to cling to my ungrounded confidence under the pressure of forty trillion won. That was what his answer carried.
I gave him a light nod, then walked over to Department Head Maeng Giyong and Principal Researcher Jo Seokhun, who were stationed at one side of the tent.
“All right, you two. Sightseeing’s over. Let’s get to work. Bring up the structural analysis program on the laptop.”
At my words, Director Maeng snorted and turned the laptop screen toward me.
“Man, and here we are in Sweden doing this again. Not long after we were tearing apart a torpedo down in Geoje, either.”
“You’re telling me. I’m already looking forward to what kind of outrageous mess you’re going to make now that you’ve powered up the laptop.”
Standing beside the grumbling Maeng, who used honorifics out of consideration for the people around him, Jo Seokhun chimed in, his eyes bright with interest.
These two had become the field aces who’d handled one insane project after another with me, from the powerpack to Hunt-Dog and, not long ago, the supercavitation torpedo.
They were also my most reliable partners, the ones who would flinch every time I stood behind a monitor and dumped some absurd intuition on them, only to turn that intuition into steel with flawless precision.
“Anyway, let’s get started.”
I stood with my arms folded behind the two of them as they opened the laptop.
“Principal Researcher Jo. Let’s add one condition to the simulation. If the barrel bends slightly upward every time it takes heat, then we pull it down from below with wire and force it back to level. Could you try putting in the numbers?”
Tap-tap, click.
At my instruction, Jo Seokhun immediately began hammering the keyboard and entered a virtual tension load.
Watching the altered drawing on the laptop screen in 3D graphics, I could see the result with my own eyes.
Tsk. This time the stress is too strong.
On the 3D model on the screen, blood-red waves were leaping around like crazy.
If we brute-forced it with wire alone, the steel wouldn’t survive the thermal expansion and would tear apart.
This wouldn’t do.
Just as I was thinking that, Director Maeng, the hydraulics expert, clicked his tongue and said, “Chief Executive, if you yank it around like that with wire alone, the steel will just tear once it expands from heat. You need a small accumulator and hydraulic cylinders that can flexibly absorb the tension and give the force somewhere to go.”
“Hmm, that makes sense.”
“Right? Principal Researcher Jo, add a hydraulic cylinder variable underneath.”
“I already did while you were talking. Look. Just adding the accumulator throws the timing off, like Director Maeng said.”
“Huh, so that’s how it is?”
At Director Maeng’s words, Jo Seokhun looked at the refreshed screen.
It was better than before, but a different problem had surfaced.
Red sparks were still flickering intermittently across the drawing.
The hydraulics could absorb the force of expansion, but the change in displacement that happened in a split second of 0.1 seconds was too quick for a mechanical accumulator alone to follow perfectly, and the system was falling out of sync.
“Then the barrel would be swaying every time it fires. The expansion speed changes depending on the firing heat, so there’s no way to precompute exactly when and how much to pull with hydraulics.”
Jo Seokhun narrowed his eyes and pointed out the limit.
A precise analysis, exactly what you’d expect from a control specialist.
I took his words and immediately pointed to the perfect answer.
“There’s no need to precompute it. Principal Researcher Jo, put displacement sensors on the front and rear of the barrel. The moment the steel bends by one millimeter, the control logic should trigger dynamic feedback and have the hydraulic cylinder pull that same one millimeter in just 0.1 seconds.”
“Ah...! So it reacts in real time and only pulls as much as it bends? Understood!”
At my crisp solution, Jo Seokhun’s eyes lit up and his fingers flew back over the keyboard.
Tap-tap-tap-tap!
With Jo Seokhun’s relentless typing, new variables poured into the model.
And the moment the Enter key went down.
The red sparks that had been circling the 3D drawing on the monitor were washed away before my eyes as if they’d never existed.
In their place, clear, sleek blue lines stretched outward, locking the swaying barrel into an utterly solid, perfectly straight line.
I found it.
This was the perfect answer.
Silently cheering inside, I began explaining the result that only I could see in engineering terms the others could understand.
“Good. This is it.”
“What? That works?”
“Yes. The instant heat expansion makes the steel lengthen, the dynamic logic Jo Seokhun wrote pulls on Director Maeng’s hydraulics by exactly that amount, flexibly opening space and then re-centering the zero point.”
“Ahh...”
“You’re not fighting force with more force. You’re opening a path for the force to escape while forcing only the direction of a straight line.”
At my clear logic, Jo Seokhun’s eyes widened.
“Uh... now that you put it that way, yes? Then no matter how much heat builds up, the trajectory will keep a straight line for sure.”
“We call it the Active Counter-Stress Truss. A mechanical muscle that makes the impossible possible.”
It was originally a control system used in civil engineering.
It reduced sway in structures like skyscrapers under external shocks such as earthquakes or strong winds, allowing internal stress to disperse evenly.
It wasn’t a familiar method in mechanical engineering, but what did it matter if borrowing it could solve the problem?
Thinking that, I immediately turned and headed for Chief Executive Jo Taehyung.
“What did you just say you were going to do?”
Jo Taehyung, who had been watching us from a little distance away, frowned and asked again.
I answered him calmly.
“We’re going to mount hydraulic cylinders and high-tensile wire on the outside of the main gun, then build an active control truss that applies tension in the opposite direction of the force trying to bend the barrel.”
“You think that’ll work?”
Jo Taehyung threw back an immediate, sharp objection, like he couldn’t believe what he was hearing.
“Vice President Baek. Thermal deformation is the domain of pure thermodynamics, where the molecular structure of the material expands from within. If you try to pin that down from the outside with mechanical tension like wire, you might preserve the visible straightness for a while, but the suppressed expansion force will pile up as internal stress. In the end, the barrel will accumulate enormous fatigue and won’t be able to withstand the 4,000-degree high pressure generated during firing. You’d get microcracks or outright rupture, wouldn’t you?”
As expected, it was the sharp assessment of someone who truly deserved to be the heir apparent and the head of the Ground Weapons Systems Command.
If this had been a one-dimensional approach of simply crushing it with brute force, then Jo Taehyung would have been right and the barrel would have torn apart on the spot.
I smiled faintly at his concern and pushed back.
“That’s why I said active, Chief Executive. We’re not pinning it down by force.”
“Not pinning it down by force?”
“The instant heat expansion makes the steel lengthen, the displacement sensors mounted front and rear on the barrel detect it. Then the hydraulic cylinders flexibly create space for exactly that expanded volume and let the force pass through. We’re not blocking the force and stacking up stress; we’re opening a path for the expansion while enforcing only the direction of a straight line. Like the dampers in a skyscraper that absorb earthquake shocks while keeping the frame intact.”
“...What?”
Jo Taehyung’s eyes widened until they looked ready to split from the shock.
It was an idea that used the concept of civil engineering to bury thermodynamic limits and material shortages under a destructive form of mechanical engineering.
It was as if a shockwave unlike anything he had ever experienced had just swept through the mind of an elite trapped inside theory.
“My God.”
A stunned exclamation slipped from Jo Taehyung’s mouth.
He looked back and forth between me, Director Maeng, and Principal Researcher Jo with trembling eyes and asked, “In theory... this is perfect. If we modify it this way, will it really work?”
At that desperate question, I gave a heavy nod full of certainty.
As soon as Jo Taehyung saw my answer, his gaze returned in an instant to that of a cold, sharp commander.
He immediately grabbed the radio and satellite phone and shouted at the managers inside the tent.
“Track down every single special welder and hydraulic technician we have from Hanseo currently stationed across Europe, right now! Cost doesn’t matter, so charter a private jet immediately and bring them here to Kiruna! We start work within ten hours!”
◇◇◇◆◇◇◇
The work was carried out at once.
In the middle of the minus-thirty training range, a huge temporary windbreak tent was erected over the tank.
South Korean A-class technicians rushed in on private jets, along with Korean technicians hastily gathered from across Europe, and under our supervision they went berserk with sparks as they began modifying the barrel.
Fsssssh—!
“Lower that cylinder bracket angle by another half degree! The wire tension’s twisting!”
“Yes, sir!”
I was directing the site together with Jo Taehyung’s managers, shaping the steel beast when it happened.
From the entrance of the windbreak tent, I heard an unfamiliar language.
The local engineers from the Swedish Defence Materiel Administration, who had apparently been so impressed by watching us clear the ice off the tracks, couldn’t hold back their curiosity and had drifted closer.
They stared wide-eyed at the bizarre web of wire and hydraulic cylinders being grafted onto the outside of the main gun like a skeleton.
“What exactly are you doing to the barrel right now?”
To the Swedish technician’s careful question in English, I flipped through the drawing and answered without much ceremony.
“The barrel couldn’t handle ice and fire and kept trying to bend, so we’re fitting it with muscles to force it straight.”
“Oh, my God. Germany’s Leopard has spent more than half a century accumulating metallurgy data to make a perfect alloy that can survive the cold. Isn’t this a fundamental materials problem that can’t be solved just by attaching wires on the outside like you’re doing?”
At that question, I pushed my welding mask up and looked the Swedish technicians straight in the eye.
“If Germany survives on fifty years of static data, then we’re giving the machine a dynamic muscle that responds to the environment in real time. When the steel bends, the muscle pulls it back and forces it straight. If the data is lacking, then you just make the machine adapt to the environment on its own.”
“......!”
The Swedish technicians’ mouths fell open.
To northern European elites who relied only on static data and materials engineering, the philosophy of Korean engineers chewing through a lack of data with rough, dynamic mechanical engineering must have been a fresh shock.
They quickly pulled out notebooks and began meticulously jotting down our modification process with eyes full of wonder.
And at last.
“Work’s done,” Director Maeng called out, wiping grease from his hands.
The beast had revealed itself, now clad in an Active Counter-Stress Truss that gave off an eerie but overwhelming presence.
I watched it for a moment, then informed Jo Taehyung, “We’ve reset the zero point, so let’s go straight to the firing test.”
Jo Taehyung looked back and forth between the modified barrel and me, truly awestruck, then gave a heavy nod.
I began moving with him toward the test area.
And in the midst of that, I could see him.
Far away, outside the windbreak tent, a man was watching us move with narrowed eyes and obvious interest.
If I remembered right, that person was... the Nordstrom headquarters director from Sweden?
What’s he doing here?