The machine made a slight clicking sound, as if a gear had meshed into place.

Carl looked up at the screen. The green light was still on.

He didn't speak, his fingers already reaching for the wrench in the toolbox. Chen Hao, standing beside him, still holding the scrap metal, looked up after hearing the sound: "Still turning?"

“It didn’t stop,” Carl said in a low voice.

"Then don't just stand there, take notes."

The two immediately sprang into action. Karl stared at the instrument panel, writing down the voltage, temperature, and RPM readings for each second on the whiteboard beside him. Chen Hao, meanwhile, crouched beside the chassis, his ear pressed against the casing, listening for any unusual noises inside.

Nana stood in front of the control panel, her arm connected to the data cable, her eyes scanning the constantly scrolling parameter stream. "Currently running stably, but the heat accumulation rate is higher than expected. The protection mechanism is expected to be triggered in seven minutes and twenty-three seconds."

"Fifty seconds longer than last time," Chen Hao grinned. "I've improved."

“Not enough.” Carl erased the old records on the whiteboard. “To last for twenty minutes, the temperature needs to drop by at least another two hundred degrees.”

"The materials aren't good enough." Chen Hao stood up, patted his pants, and said, "These are all scraps pieced together; it's a miracle they even turn."

“Then let it generate less heat.” Carl turned around, opened the repair cabinet, and pulled out a roll of ceramic rings. “Nana said to use these for insulation.”

"You actually believe what she said?" Chen Hao raised an eyebrow.

“She has never miscalculated.” Nana retracted her connector and walked towards the projection area. “This is the solution in the database that is closest to the local conditions.”

A three-dimensional structural diagram appeared in the air, marking the welding points and pressure distribution. Karl looked at it and nodded: "First press, then fix, discontinuous heating."

"Sounds like assembling a toy." Chen Hao sat down against the wall. "You guys go ahead with your work, I'll keep an eye on things."

"Aren't you the one who works the hardest with your brain?" Karl sneered. "Now you're all relaxed?"

"I'm on strategic standby." Chen Hao took out his key card and tossed it in his hand. "If you guys blow it up, I'll have to call for help to put out the fire."

Nana pulled up another set of data. "HV-9 unit status confirmed; transmission components are theoretically detachable. Susan's team has entered the East District warehouse area."

"The doors over there must be rusted to death, right?" Chen Hao said.

"It's been cut open with hydraulic shears," Nana replied. "It's progressing smoothly so far."

The scene shifts to footage transmitted from a handheld terminal: Susan bends down and crawls between a pile of collapsed metal frames, while two technicians behind her use jacks to lift a crossbeam. Dust falls in a flurry, and her headlamp shines on an old piece of equipment with "hV-9" written on its casing.

“That’s it.” She wiped the dust off her face and reached out to touch the interface cover.

Nana's voice came through the communicator: "Pay attention to the third bolt on the right. It is severely corroded. The torque must not exceed twelve Newton-meters."

“Received.” Susan switched to a smaller wrench. “The old man has been lying here for three years; his parts are probably all stuck together.”

She slowly and gently unscrewed the screws. As the cover loosened, a strong smell of stale engine oil wafted out. She wrinkled her nose and reached inside to feel the transmission compartment.

“There’s movement,” she whispered. “The components are still inside, they haven’t deformed.”

The technician behind her handed her an insulating sleeve. She put on gloves and slowly disconnected the wires. After unplugging each wire, she would pause for a few seconds to check for any short circuits.

"The main power is off," she reported. "Prepare to retrieve the module."

“The cushioning packaging has been sent to the terminal,” Nana reminded. “Put it into the shockproof box immediately after taking it out.”

"Understood." Susan took a deep breath, gripped the edge of the component with both hands, and slowly pulled it outwards.

A metallic scraping sound rang out, followed by a soft "click"—the component detached from the slot.

She placed it on the workbench and turned on the detector. The screen displayed several numbers before finally stopping at a green indicator.

"It's intact." She breathed a sigh of relief. "It works."

“Bring it back to base,” Nana said. “Highest priority.”

Susan nodded and directed the team to disassemble and pack the equipment. She personally placed the transmission components into the shockproof box and then wrapped them with a layer of foam.

“Let’s go,” she said. “We can still make it back in time for dinner.”

Meanwhile, in the repair area, the fourth assembly has already begun.

Karl slipped the ceramic ring onto the shaft and then tightened the joint little by little with hydraulic pliers. This time there was no welding; the entire process was done cold. Chen Hao squatted beside him, handing him tools, occasionally asking, "Will this really work?"

“I don’t know.” Carl tightened the last retaining ring. “We’ll only know if we try.”

They installed the new prototype into the chassis and connected the test power.

The screen lit up, the red light flashed once, and then turned yellow.

"Starting up," Nana monitored.

The fan turned slowly, and the sound was much more stable than before. The temperature curve rose slowly, but the slope became noticeably gentler.

"Six minutes have passed." Chen Hao stared at the timer. "The police haven't been called yet."

“Nine minutes,” Carl added.

"Twelve minutes," Nana announced. "The system is still in a safe zone."

The two exchanged a glance.

"There's potential." Chen Hao smiled.

"Eight minutes short," Carl said without smiling. "Not enough."

“But we’re on the right track.” Chen Hao stood up. “This means the ceramic ring is useful, and the process can be modified.”

“The problem is, we don’t have time to optimize it slowly.” Carl looked at the instrument panel. “If Susan can’t bring back the parts, this thing still won’t be able to withstand the restart process.”

“She’ll bring it back,” Chen Hao said. “And even if she does, you’ll still have to keep making changes. Who knows if the old components can handle the new load?”

Carl didn't speak, but looked down to check the seams for any micro-cracks.

Nana suddenly spoke up: "The power fluctuations in the maintenance area are intensifying, interfering with the test signals."

"Where did this fluctuation come from?" Chen Hao turned to look at the distribution box.

“The external input is unstable.” Nana’s quick operation panel says, “It is recommended to disconnect unnecessary loads and add a temporary voltage regulator.”

"I'll go get it." Chen Hao stood up. "The old distribution cabinet has a spare port, and we can also connect a capacitor in parallel."

He opened his toolbox and found several wires and an old voltage regulator module. He spread out a wiring diagram on the floor and started connecting the wires while gesturing.

“You understand this?” Carl looked up.

"I don't understand." Chen Hao tightened the last screw. "But I've seen it done three times, and it's always fixed this way."

He turned off the switch.

With a soft hum, the lights on the entire repair station steadied for a moment.

"Alright," he said. "Now you can focus on your welding."

“I didn’t weld,” Carl corrected. “I crimped.”

"Whatever," Chen Hao waved his hand. "Just don't make me crawl on the floor again."

At this moment, Nana received a new message: "Susan's team has left the East District warehouse and is on their way back. The items they are carrying are in normal condition."

"How long will it take?" Chen Hao asked.

"We are expected to arrive at the base entrance in 43 minutes."

“There’s still time.” Carl looked at the prototype being tested. “Let’s do another round of debugging and try to get the time down to fifteen minutes.”

"Double insurance." Chen Hao nodded. "They bring back the original parts, and you make the spare parts here. At least one of them will work."

"Provided the machine doesn't completely break down during this time." Carl unplugged the power, preparing to disassemble the prototype for fine-tuning.

Nana suddenly reminded: "Attention, the temperature of the test module has reached the critical value. It is recommended to pause the operation for five minutes to cool it down."

“I can’t wait five minutes.” Karl shook his head. “If we stop now, the data from before will be wasted.”

"Then be careful." Chen Hao sat back down against the wall. "I'll keep an eye on my watch."

The fan was still running, the sound steady. The red line on the dashboard climbed slowly. Carl used the rangefinder to check the degree of deformation at each interface, moving very slowly.

Nana continuously monitors the power status, reporting data every ten seconds.

"Voltage is stable. Current is normal. The rate of temperature rise in the casing has decreased by 34%."

"It works," Chen Hao said.

“Add another layer of insulation.” Carl removed the side cover and picked out a thin metal plate from the parts box. “Put it here to block heat radiation.”

Chen Hao handed over the glue gun.

He had just pulled the trigger when the machine suddenly jerked.

The screen flashed yellow, and the fan speed suddenly dropped.

"What's wrong?" Chen Hao let go of her hand.

“The voltage dropped.” Nana immediately pulled up the circuit diagram. “There was a momentary interruption in the external power supply, lasting 0.8 seconds.”

"Damn it." Carl quickly checked the connections. "Was the voltage regulator I just connected loose?"

"No." Chen Hao checked the distribution box. "The main line tripped, but it's back to normal now."

“But the components are affected.” Carl pointed to the instrument panel. “The temperature suddenly increased, and there was a slight sticking in the bearing position.”

Can it still be repaired?

Carl didn't answer; instead, he disassembled the prototype and placed it on the table. He turned on his magnifying glass and examined the joints closely.

There is a barely visible fine line that cracks at the edge of the ceramic ring.

“It’s cracked,” he said.

"Just a little short," Chen Hao sighed.

“Again.” Carl tossed the scrap into the recycling bin. “There are still materials left, and I’m familiar with the process.”

"Aren't you annoyed?" Chen Hao asked, watching him take out the materials again.

“Annoying.” Carl looked down and cut the metal sheet. “But I’m even more annoyed by the machine stopping.”

Nana updated the progress report: "Fourth test of the self-made prototype terminated, running time twelve minutes. Thermal stress concentration point found, improvement plan recorded. Search route confirmed, Susan's team is still nineteen kilometers away from the base entrance."

"Soon," Chen Hao said.

“We’ll be there soon too.” Karl loaded the new materials. “This time, I’m going to finish in fifteen minutes.”

He began assembling, moving even faster than before. Chen Hao silently handed him the tools, asking no further questions.

The fan started up again, and the screen lit up with a green light.

Time passed second by second.

Eight minutes.

Ten minutes.

Twelve minutes.

When the clock struck thirteen minutes and fifteen seconds, Karl suddenly looked up.

“Listen,” he said.

Chen Hao stopped writing and pricked up his ears.

The sound of the fan has changed.

It was no longer a uniform whooshing sound, but a vibration with a slight rhythm.

“Something’s not right,” he said.

Carl immediately checked the instruments.

The temperature was normal and the rotation speed was stable, but the vibration frequency fluctuated periodically.

"Resonance?" Chen Hao asked.

“Maybe.” Carl quickly adjusted the support foot pads. “Let’s try a different fulcrum.”

He had just reached out to tighten the base screws when the machine suddenly jolted.

The screen is flashing red.

The alarm went off.