229: Chapter 229 A seven-and-a-half-meter-long iron coffin, big enough for a person to stand inside!

sentry ship arrival countdown, day 30.

Pangu Laboratory, B2 level, evening.

When Su Che returned from Kaitian Base, the lights on the B2 level were already on.

Liu Huaqiang notified everyone quickly, and they arrived even faster.

Academician Zhang Weide was already sitting in front of the supercomputing terminal, a blank modeling window open on the screen.

Academician Sun Qiwen's thermos had changed positions, moved from the second shelf of the cabinet to the third, with the mouth of the cup facing the wall.

Zhao Mingyuan was not at his workstation; he was standing in front of the large public screen, hands in his pockets, staring at the blankness on the screen.

Su Che walked to the main console and projected the complete blueprints of the Cheng Ying All-Domain Tactical Mecha onto the large public screen.

The 7.5-meter full-body Mecha slowly unfolded on the screen.

It was humanoid.

Two legs, two arms, a torso, and a head.

The proportions were close to a human body, but every joint was three to four times thicker than a human's. The torso looked like an inverted trapezoidal armored box, and the bulge on the back was the Anti-gravity low-altitude flight module.

The B2 level fell silent for a few seconds.

Academician Zhang Weide spoke first.

"This time, it's not an aircraft."

"It's not an aircraft." Su Che read through the overall machine parameters.

"Height 7.5 meters, weight 10 tons, powered by a portable Controlled Nuclear Fusion infantry battery, Anti-gravity low-altitude flight module for maneuverability, dual-mode ground walking and low-altitude flight, and full deep-space radiation protection."

Zhao Mingyuan pulled one hand out of his pocket and pointed to the waist and abdomen area of the Mecha on the large screen.

"Where is the person?"

"In the chest cavity; the pilot lies supine in a conformal seat within the chest section."

Su Che switched to the cross-sectional view. "The limbs are rigidly connected to the Mecha's limbs via exoskeleton linkage rods. The head wears a Brain-Computer Interface helmet, allowing dual-channel control via conscious commands and physical movements."

"Supine?"

"When the Mecha is standing, the pilot's spine is parallel to the Mecha's spine, head up and feet down. But the pilot isn't standing inside; they are half-lying in a conformal seat, with the back and pelvis bearing the weight, and knees slightly bent."

Zhao Mingyuan pulled his other hand out as well.

"So if the pilot raises their right arm, the Mecha raises its right arm?"

"Yes! The force amplification ratio of the exoskeleton linkage rods is 1 to 120; if the pilot exerts one Newton of force, the Mecha outputs 120 Newtons."

Academician Li Zhengyang stood to the left of the large screen. "Su Che, this isn't a flight control issue anymore; this is ergonomics."

"The control interface for an aircraft is a joystick, throttle, and Brain-Computer Interface—clear, straightforward input and output."

He finished in one breath. "The Mecha is human movement mapping: 22 degrees of freedom for the human upper limbs plus 16 degrees of freedom for the lower limbs, totaling 38 degrees of freedom. Each one must be precisely mapped to the corresponding joint on the Mecha."

"That's why I called someone."

Su Che looked toward the communications area.

Academician Chen Shian walked out from behind the door of the communications area.

The Director of the Life Sciences Division of the Longguo Academy of Sciences, in his early sixties, with evenly graying hair, wearing silver-rimmed glasses, and lab coat sleeves rolled up to the mid-forearm.

He didn't appear on the B2 level often.

The last time he appeared was during the development of the Brain-Computer Interface.

"Little Su, I looked at your human movement mapping model on the way here." Academician Chen Shian took a tri-folded A4 paper out of his lab coat breast pocket, unfolded it, and placed it on the main console.

On the paper was a handwritten set of data on the range of motion of human joints.

"Out of the 38 degrees of freedom, six are redundant and almost never used in normal human movement."

"Extreme postures like internal rotation of the knee joint or inversion of the ankle joint won't occur in combat."

"Cut the redundant degrees of freedom, map to 32 effective degrees of freedom, and the complexity of the control algorithm will drop by 30%."

Su Che glanced at the data set.

"Cut it."

Academician Chen Shian put the A4 paper back into his pocket.

Su Che refreshed the division of labor table on the large screen.

"Academician Zhang Weide, overall Mecha structure, joint drive mechanism, and force transmission path of the exoskeleton linkage rods."

"Academician Chen Shian, human-machine adaptation, pilot's conformal seat, body positioning constraints, life support, and anti-G protection."

"Academician Sun Qiwen, power distribution and heat dissipation for the portable Controlled Nuclear Fusion infantry battery, and energy consumption for the 10-ton Mecha in both ground running and low-altitude flight modes."

"Wen Bo, armor materials, and the balance between thickness and weight for the high-strength anti-radiation protective coating."

"Zhao Mingyuan, control algorithms for exoskeleton linkage, real-time mapping of 32 degrees of freedom, plus mental assistance via the Brain-Computer Interface."

"Academician Li Zhengyang and Academician Qian, weapons and protective shields will be addressed later; let's build the overall skeletal frame first."

Five lines of work unfolded.

Academician Zhang Weide closed the modeling window for the Mingdi Interceptor and opened a new one.

When he entered the basic Mecha parameters into the command line, his hand paused at the "walking gait" column.

"Su Che, when the 10-ton Mecha walks on the ground, what is the ground pressure during the single-leg support phase?"

"Calculating based on a height of 7.5 meters and alternating bipedal walking, the single-leg support area is about 0.6 square meters. With 10 tons concentrated on 0.6 square meters, the ground pressure is 160,000 Pa."

"160,000 Pa."

Academician Zhang Weide entered this number and took a moment to process it.

"The bearing limit of ordinary asphalt pavement is 0.7 MPa. 160,000 Pa is less than a quarter of the limit, so walking on normal roads is no problem. But if it's on soft soil..."

"Soft soil isn't the primary combat scenario on Earth; it's for the Moon and Mars. Moon gravity is one-sixth, Mars is three-eighths, so the ground pressure will be scaled down proportionally."

Academician Zhang Weide didn't dwell on it anymore and started building the joint drive mechanism.

...

sentry ship arrival countdown, day 28.

B2 level, morning.

Two days passed.

Academician Zhang Weide completed the first round of structural design for the Mecha's lower limb joints.

The knee and ankle joints were the two points bearing the most weight and were also the places where the entire Mecha was most prone to issues.

He pushed the cross-sectional view of the knee joint onto the large public screen.

"Su Che, I have two proposals for the knee joint drive method."

"Option one: hydraulic drive. High thrust, fast response, but if the hydraulic lines are pierced in combat, it will directly lose mobility."

"Option two: electric direct drive. Superconducting motors are embedded directly into the joints; there are no exposed lines, but the torque output of a single motor is 30% lower than hydraulic."

Su Che looked at the two sets of numbers.

"What does 30% lower mean?"

"It means the Mecha's maximum speed at full sprint drops from the design target of 60 km/h to 45."

Academician Chen Shian slid over in his chair from the test bench.

"Running slowly doesn't matter; it has an Anti-gravity flight module. There are few scenarios where ground running is necessary; most of the time, flying over is faster."

"But landing operations involve urban warfare." Zhao Mingyuan's voice came from the corner. "Low-altitude flight in city streets risks hitting buildings; sometimes, rapid ground advancement is safer than flying."

Su Che made a decision.

"Electric drive. The risk of lines being pierced is uncontrollable in actual combat; even if speed drops, the Mecha must be guaranteed to keep moving after taking a few hits."

"45 is enough." Academician Zhang Weide changed the parameters.

Academician Sun Qiwen came out of the U-shaped array area, not holding his thermos, but a plate of peanuts.

"The power consumption distribution for the infantry fusion battery is out. In ground walking mode, joint drive plus life support plus communication and navigation, the total power consumption is 35% of the fusion battery's rated output."

He tossed a peanut into his mouth. "In low-altitude flight mode, with the Anti-gravity module at full capacity, total power consumption jumps to 72%."

"What about the margin?"

"The margin in ground mode is very large; the 65% remaining capacity is all reserved for weapons and shields. Flight mode is tighter; weapons and shields only get a 28% margin."

Su Che noted down the two sets of numbers.

"Is 28% enough to fire weapons and activate shields simultaneously in flight mode?"

"Firing is enough; the power consumption of the directed-energy rifle is not high, it's infantry-grade. Activating shields is also enough; the power consumption of the micro-shield is three orders of magnitude lower than the luan bird's ship-borne shields..."

"But if the gun and shield are both at full power, it's right on the edge of 28%, with no margin left." Zhao Mingyuan threw in a comment. "The probability of being hit while flying is higher than on the ground."

Su Che looked at Academician Sun Qiwen. "In flight mode, shield priority is higher than the rifle. The fire control system will automatically limit the rifle's power output to 70% to ensure the shield always has an 8% power margin."

Academician Sun Qiwen dipped a peanut in the salt on his finger.

"Will the effective range of the rifle decrease at 70% power?"

"Yes, it will shrink; it'll be 70% of the designed full range, which is enough on the battlefield."

Academician Sun Qiwen tossed the last peanut into his mouth and walked away with the empty plate.

...

sentry ship arrival countdown, day 26.

B2 level, afternoon.

Another two days.

Academician Chen Shian's human-machine adaptation proposal reached its second version.

He had overturned the first version himself.

"The angle of the headrest on the supine conformal seat is wrong. When the pilot is lying supine, a 15-degree forward flexion of the cervical spine is the most comfortable angle. But when the Mecha performs a forward lunge, acceleration will push the pilot's head backward, passively extending the cervical spine from 15 degrees of flexion to 0 degrees."

He spread out the mechanical model of the human cervical spine on the test bench.

"Repeatedly swaying between 15 degrees and 0 degrees, after two hours, the cervical muscles will fatigue, and the pilot will start to feel dizzy."

Su Che stood next to the test bench.

"Can the airbag cervical protection module from the White Emperor be moved over?"

"The White Emperor's pilot is in a seated position; the direction of force on the cervical spine is completely different from the Mecha's supine position. The inflation orientation and support angle of the airbag must be redesigned."

Academician Chen Shian pushed up the sleeves of his lab coat, revealing an old watch on his forearm.

"I've redesigned a dynamic cervical support module. It's not an airbag, but a gel-filled adaptive pillow. The viscoelastic coefficient of the gel is damping-matched to the vibration frequency of the cervical spine."

He paused. "When the pilot's head is pushed back, the gel actively hardens to block it; when the head returns to center, the gel softens so as not to obstruct."

"Response time?"

"30 milliseconds. The time window from the moment a human cervical spine is subjected to force until discomfort arises is 200 milliseconds. 30 milliseconds to intervene is more than enough."

Su Che confirmed this proposal.

Zhao Mingyuan had been sitting at his workstation in the corner since the morning.

The real-time mapping algorithm for 32 degrees of freedom had reached its third version.

The first version was pure exoskeleton force feedback—the Mecha moved when the pilot moved—but the problem was high latency.

The second version added Brain-Computer Interface intention prediction; the pilot's movement intention was captured by the Brain-Computer Interface before the limbs moved, starting the Mecha's joints 50 milliseconds in advance.

The latency was solved, but another problem arose.

"Su Che, there are false triggers in the Brain-Computer Interface intention prediction."

Both cuffs of Zhao Mingyuan's work uniform were covered in writing. Today, he had changed into a new anti-static work uniform, and the left cuff was already half-filled.

"What's the situation?"

"The pilot thinks about raising their hand but hasn't done it yet. The Brain-Computer Interface captures the movement intention, and the Mecha raises its hand 50 milliseconds early. But if the pilot thinks about it and then changes their mind and decides not to raise it, the Mecha has already raised it."

Su Che thought for a moment.

"Add an intention confirmation window. After the Brain-Computer Interface captures the movement intention, don't execute immediately. Wait 20 milliseconds to see if the limbs have actually started moving. Execute only after double-confirmation from both limb signals and Brain-Computer Interface signals."

"A 20-millisecond confirmation window, plus the 50-millisecond lead time from Brain-Computer Interface prediction, leaves an actual lead time of 30 milliseconds."

"30 milliseconds is enough. It's over 100 milliseconds faster than pure exoskeleton."

Zhao Mingyuan noted down a line of numbers on his new cuff and lowered his head to revise the algorithm.

Wen Bo came in from the corner of the corridor, not wearing anything on his waist today, his hands empty.

"The armor coating proposal is set. High-strength lightweight alloy base plus anti-radiation protective coating, total protective layer thickness 18 mm, unit area weight 42 kg/m²."

"In the 10-ton overall weight budget, how much does the armor account for?"

"The Mecha's surface area is about 37 square meters, with a total armor weight of 1,550 kg. After subtracting about 15% of the area for the thinned-out regions at the joints, the actual armor weight is around 1,320 kg."

Academician Zhang Weide chimed in from the supercomputing terminal.

"1,320 kg of armor plus 3,400 kg of frame, plus 1,200 kg of fusion battery and flight module, plus 800 kg of weapon and shield systems, with 300 kg reserved for cables, lines, and seats, totals 7,020 kg."

"There's still 3,000 kg left until 10 tons."

"The rest is for the micro-spatial displacement evasion module, various redundancy backups, and the pilot's own weight."

Su Che updated the overall machine weight distribution table, clearly marking the weight percentage of each subsystem.

The windows outside the B2 level showed the twilight.

In late October, it was already getting dark early in the capital.

On the large public screen, the 7.5-meter Mecha model was slowly rotating.

The skeleton had an outline, the joints had a drive solution, the human-machine adaptation had a cervical gel pillow, the control algorithm was being polished into its third version, and the armor material thickness was set.

Five lines of work were pushing forward simultaneously.

In the corner of the main screen, the sentry ship arrival countdown.

26 days.