Carl crouched at the edge of the ruins, pulling his fingers back from the muddy ground. He stared at the half-footprint for two seconds, then looked up and glanced deeper into the mine.
Nobody moved.
Chen Hao tucked the clipboard back under his arm and said in a low voice, "Let's retreat first."
Nana didn't speak, but the projection had already been taken down. As she turned around, the mechanical joints made a slight turning sound, like a rusty door being pushed open.
Susan turned off the terminal and casually stuffed the sampling bottle into her backpack. She didn't ask why they were leaving, nor did she glance at the footprints. At times like this, trusting the captain was more important than asking for reasons.
The four of them returned the way they came. It took them forty minutes to get there, but only twenty-five to get back. Chen Hao walked in front, his pace faster than usual, but he didn't falter. He knew the three behind him were watching his back, and as long as he didn't stop, they wouldn't panic.
The sample box was double-locked, labeled with a pressure tag, and carried by Karl. These things are more precious than oxygen cylinders now.
It was still dark when they returned to base. The wind was strong outside, making the metal exterior walls hum. They took off their diving suits and went straight into the laboratory.
"Turn on the lights," Chen Hao said.
The lights came on. White light shone on the workbench, making the rare metal brought back from the mine gleam coldly. Its surface was uneven, as if it had been struck by something hard, with tear marks along the edges.
"This is it." Chen Hao plopped down in a chair. "Let's stop digging and make good use of it first."
Nana walked to the analyzer, her arm popped out a data cable, and she plugged it into the interface. The screen flashed, and the scan began.
“During the hardness test… the thermal conductivity is abnormal… the crystal structure is asymmetrically arranged.” She listed them one by one, “It is not suitable for traditional processing methods.”
"Can't you cut it?" Carl stood to the side, holding a wrench in his hand.
“High-temperature cutting will cause an imbalance of internal stress, and the material will break,” Nana said. “Low-temperature cutting is also not good, it’s too brittle.”
"Then don't cut it." Chen Hao leaned back in his chair. "We're not making a kitchen knife. Can we try a different approach? Like—stick it on?"
Susan looked up at him: "You mean, use this thing as a shell?"
“Yes.” Chen Hao sat up straight. “Our diving suits can’t withstand the pressure in the deep zone, and our oxygen tanks won’t last long either. If we could add this layer on the outside, we might be able to survive a few more minutes.”
“The idea is feasible.” Nana pulled up a 3D model of the diving suit. “I suggest making thin sheets of rare metal to cover key areas: the chest plate, shoulders, and back of the neck. The oxygen cylinder can also be wrapped to improve pressure resistance.”
“Sounds simple,” Carl muttered, “but how are you going to slice it up? By biting it?”
“No need for teeth.” Nana turned her head. “I have a plan.”
She opened the database, the pages scrolled rapidly, and finally stopped on a technical file.
“Low-temperature pulsed laser micro-sculpting,” she said. “Combined with inert gas coating and welding, it can achieve precise shaping and avoid thermal damage.”
“I don’t understand.” Karl scratched his head.
“It means—” Chen Hao continued, “that you use a cold laser to shave it little by little, with air jets protecting it from exploding. It’s similar to shaving, just with more expensive tools.”
“We have the equipment.” Nana walked to the cabinet in the corner, opened the drawer, and said, “The laser array left over from the last reactor repair is still usable. We just need to modify it.”
“Then you do it.” Chen Hao waved his hand. “Susan and I will keep an eye on the parameters, and Carl will assist you.”
No one rested for the next six hours.
Nana was in charge of the main control; the laser beam traversed the metal surface, emitting a faint hiss. Each small piece was clipped and placed into a tray to cool. Susan recorded the deformation rate and energy consumption, adjusting the output power from time to time. Karl ran back and forth, delivering parts, changing coolant, and cleaning lenses.
Chen Hao sat in front of the monitor, his eyes fixed on the progress bar.
“Fifteen percent remains,” he said.
"Watch out for temperature fluctuations," Susan warned. "It just rose by 0.3 degrees Celsius. Although it's not above the limit, the trend is wrong."
"The cooling flow rate has been adjusted," Nana responded. "It's currently stable within a safe range."
It was noon when the last piece was finished.
Seven thin metal sheets were neatly arranged in the tray, resembling silver-gray fish scales.
"Next step," Chen Hao rubbed his face, "assembly."
They chose an older wetsuit as a prototype. They removed the outer layer to reveal the carbon fiber frame underneath. According to the design, the metal plates were to be attached to the areas of greatest stress.
The first piece was successfully glued on.
The second piece had just been pressed down when a crack appeared on the edge.
"Stop!" Susan shouted.
Everyone stopped.
The crack wasn't long, but it was quite noticeable under the light. A slight bend revealed the exposed base inside.
“The coefficients of expansion don’t match.” Susan touched the crack. “Metal and polymer react differently under pressure, so the hard adhesive will break.”
"Then what do we do?" Carl asked, "Rebuild the base?"
"It's too late." Chen Hao shook his head. "Do you have any cushioning material? Something soft and absorbent."
Susan thought for a moment: "The diatomaceous earth adhesive we found last time was natural, flexible, and resistant to water pressure."
Where?
"It's still in the sample cabinet; it hasn't been sent away yet."
In less than five minutes, the bottle arrived. It was a grayish-white paste, somewhat like toothpaste.
"Try it." Chen Hao handed it over.
Susan applied a small amount to the seam and then pressed the metal sheet on top. This time, she didn't apply pressure immediately but waited ten minutes to allow the adhesive to adhere naturally.
"Alright." She let go. "It's not cracked."
"Press it again," Chen Hao said.
They slowly increased the pressure to simulate a deep-sea environment. The numbers on the screen jumped, from 500 meters equivalent to 800 meters, and then to 1,000 meters.
The crack did not widen.
“It’s done.” Carl smiled. “The sandwich structure really works.”
“It’s not just about the structure,” Nana added. “We can also optimize the distribution. Based on historical damage data, the right side of the sternum is most vulnerable, so we should add a double layer there.”
"You draw, I'll paste." Chen Hao stood up. "Let's try to finish the whole set this afternoon."
It was already dark when the new diving suit was completed.
Overall, it doesn't look much different, but it weighs three kilograms more. The surface is smooth with low reflectivity, unlike ordinary coatings which are glaring.
“What should we call it?” Carl asked.
"Deep Dive Type 3," Chen Hao said. "The first two were scrapped. If this one breaks down too, we'll have to switch to sand mining."
Next up are the oxygen cylinders.
The old model could only last six hours, which was far from enough for missions in the deep zone. They wanted to coat the outer layer with rare metals and improve the internal oxygen supply system.
Nana retrieved the data from Chapter 659 for reference and redesigned the valve control logic.
“The problem is the release rate,” she said. “The new material has too high air conductivity, and the initial flow rate is too high, which can easily cause breathing disorders.”
"Then let's add a manual valve," Chen Hao suggested. "If automatic doesn't work, we'll adjust it ourselves."
“Okay.” Nana nodded. “We’ll add an emergency knob, located on the left side of the bottle, so it can be operated directly with your thumb.”
The first test was conducted in a simulator.
Carl put on his new diving suit, slung his oxygen tank over his shoulder, and entered the pressure chamber.
The door closed.
The pump starts, and the pressure gradually increases.
“Five hundred meters.” Susan stared at the screen. “Breathing rate is normal.”
"800 meters. Oxygen supply is stable, and no leaks have been detected."
"1200. The coat is in good condition and the seams are intact."
"Wait a minute," Chen Hao suddenly pointed to the oxygen curve, "The flow rate is increasing!"
Sure enough, the number jumped, from two increases per minute to three and a half.
"Adjust manually," Nana ordered.
Carl pressed the knob, and the flow rate dropped.
“Let’s try again,” Chen Hao said. “This time, let’s start from 1,500.”
The second test took even longer. They repeatedly adjusted the algorithm, tried three different output modes, and finally settled on a constant current scheme.
Battery life has increased by 40%.
"It's enough." Chen Hao signed to confirm the acceptance. "At least it will keep us alive a little longer."
Susan placed the diatomaceous earth adhesive sample into a sealed box, labeled it, and prepared to hand it over.
Carl checked the tools and put the laser array back in the cabinet. He wrote a line on the notepad: Batch copyable.
Nana stood in the background, the program still running. Her device had entered a low-power state, and the heat dissipation vents were slightly warm.
Chen Hao leaned against the wall, watching the fully equipped Deepsea 3 stand quietly on the shelf. Its silver-gray exterior had little luster under the light, looking like a piece of sunken iron.
He should have breathed a sigh of relief.
But he didn't move.
Just now, a signal flashed in the lower right corner of the monitor screen.
It was very short, less than a second.
The source is neither outside nor in the direction of the underground river.
It was coming from inside the rare metal they brought back.
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