Rebirth: Starting from Lighting Up the Tech Tree

Chapter 167 Technological Iteration

Three days after the signing ceremony, Li Guodong placed a report on Yu Ying's desk.

"Let's look at the data from the first month of the satellite's operation in orbit," he said. "I think you should take a look first."

Yu Ying looked at the book for ten minutes without saying a word. Li Guodong sat opposite her, waiting.

Outside the window, people were walking in the corridor on the third floor of the research institute, and the faint sounds of technical discussions could be heard.

"The actual conversion efficiency of the solar cells is 1.2 percentage points lower than the design value." Yu Ying looked up. "It's not a random error; it's a systematic one."

"Yes." Li Guodong nodded, "The attenuation is due to space radiation. The verification satellite uses first-generation gallium arsenide batteries, which were designed with a 1.5% attenuation margin, but the actual attenuation rate is faster than expected."

"In other words, if the battery materials aren't improved, the transmission efficiency will drop below 85% in a year?"

"Around the 18th month, approximately 84.7%."

Yu Ying closed the report and placed it on the corner of the table. "What kind of batteries will the second-generation satellite use?"

"Triple-junction gallium arsenide is a next-generation product. Theoretically, its conversion efficiency is 5 percentage points higher than existing products, and its radiation resistance is improved by 40%," said Li Guodong. "The problem is that there is currently too little measured data on the space performance of triple-junction gallium arsenide in China; most of the data comes from ground-based laboratories, which introduces uncertainties when extrapolated to the space environment."

This is a core technical challenge in the design of the second-generation satellite. When Zuo Cheng arrived at the research institute's conference room at 3 p.m., he happened to run into Yu Ying and Li Guodong discussing this problem; the whiteboard was covered with formulas and data.

"How's it going?"

Li Guodong turned around: "There's a hurdle with battery materials. There isn't enough data on the space decay of triple-junction gallium arsenide. We have two options now—either wait and collect more on-orbit data, or take a gamble and use it directly after reducing the theoretical value by 20%."

Zuo Cheng pulled up a chair and sat down, looking at the data on the whiteboard.

Triple-junction gallium arsenide has a theoretical conversion efficiency of 38%, which is 5 percentage points higher than existing batteries. If space degradation matches ground-based predictions, the overall efficiency of the second-generation satellite can be pushed to over 90%. However, if the actual degradation is higher than expected, the design will have to be completely redesigned.

He thought for about twenty seconds.

"Could I please see the basic material data for triple-junction gallium arsenide?"

Li Guodong pushed the notebook over. Zuo Cheng flipped through it, then stood up, walked to the whiteboard, picked up a pen, and wrote a few lines next to the existing formulas.

This was the first time he had ever written anything in the research institute's conference room. Yu Ying watched from the side without saying a word.

Zuo Cheng wrote a set of derivations—starting from the bandgap structure of triple-junction gallium arsenide materials and combining it with the energy spectrum distribution of the space radiation environment, he calculated the upper limit of attenuation at different orbital altitudes.

Li Guodong watched for a while, then his eyes slowly narrowed.

"This derivation..." he began, his tone a little strange, "I've seen similar ideas somewhere, but no one has ever combined these two dimensions in the calculation."

"That's one method," Zuo Cheng said, "It might not be correct; let's verify it."

That evening, Wei Jia ran the mathematical model. After receiving the results, he messaged Zuo Cheng: "Professor Li Guodong said your derivation error is within 5%. The actual upper limit of the decay of triple-junction gallium arsenide is 18% of the theoretical value, not 20%, so it can be used directly."

Zuo Cheng glanced at the message and put down his phone.

Something was vibrating gently in his pocket, on the system panel. In the list of leaves on his tech tree, specifically the Space Photovoltaic branch, a leaf labeled "Space Radiation Protection" lit up slightly—it had been activated by a small increment, as if it had accumulated a little progress with this derivation.

Technological convergence has not yet been fully triggered, but the implicit technological boost is already taking effect.

The design work for the second-generation satellite has entered a fast track.

Li Guodong led the overall design, and triple-junction gallium arsenide was chosen as the main material; Wei Jia re-established a more accurate atmospheric correction model and optimized it for the microwave frequency band of the second-generation satellite; Qiu Pei designed a new orbital deployment scheme, changing the satellite spacing from a uniform distribution of verification satellites to a non-uniform distribution based on the density of ground receiving stations, which theoretically can improve the overall transmission efficiency by 3 percentage points.

Three months later, the design scheme for the second-generation satellite passed internal review.

When Zuo Cheng received the final performance prediction data, the figure was 91.2%.

"It's a little more than Zhang Gang's estimate of 90%," Yu Ying said, standing next to him as they looked at the numbers on the screen.

"It's thanks to the non-uniform deployment scheme," Zuo Cheng said. "Qiu Pei's scheme wasn't even included in the initial outline."

Yu Ying smiled but didn't reply.

In the research institute's corridor, Qiu Pei was discussing the manufacturing schedule with Li Guodong. Wei Jia was working on two computers, one running an atmospheric model and the other reviewing orbital simulations. Shen Yiming called from the AI ​​division, saying that the second-generation satellite's onboard AI module needed two modifications and that they needed to confirm the interface specifications with the research institute.

The lights were on on the entire third floor of the building.

In terms of cost, Li Guodong's calculations concluded that the cost of triple-junction gallium arsenide batteries is 8% higher than that of existing solutions, but with the lightweight design of the satellite structure and the optimization of the launch scheme, the overall manufacturing cost is reduced by 22%.

This exceeds the initial design target by 20%.

"The cost can be reduced further after mass production," said Li Guodong. "The current cost benchmark is based on single-unit production; there's still room for a 15%-20% reduction after scaling up."

Han Lu has already been in contact with the procurement teams of the State Grid and China Southern Power Grid, sharing the performance parameters and timelines of the second-generation satellite ahead of schedule. Both companies are very interested, and Ge Lilin has sent a message asking if a priority purchase clause for the second-generation satellite could be added to the procurement agreement.

"Add," Zuo Cheng said.

The mass production schedule has been set. The first batch of 20 second-generation satellites is expected to complete assembly and testing within 18 months.

The first-generation verification satellite is still in orbit, with 10 satellites transmitting energy to the Dunhuang ground station daily, and test data continuously accumulating. The blueprints for the second generation have been finalized, and the manufacturing line is preparing for scheduling. Regarding the design discussions for the third generation, Li Guodong said that they will begin after the second generation is launched.

On a quiet afternoon, Zuo Cheng went through these things in his mind and felt a sense of peace that he couldn't quite explain.

It's not the satisfaction of accomplishing something, but the feeling of a train accelerating past a station—the speed has picked up, and the next station will be even faster.

He mentally opened the tech tree panel. In the leaf grid of the space photovoltaic branch, the "space radiation protection" grid had brightened a bit more, becoming more noticeable than in the morning. The overall progress of the six leaves was still a bit behind, but it was moving every day.

He didn't bother calculating how much was still missing. Once he reached that threshold, the system would automatically light up.

He put his phone back in his pocket, pushed open the meeting room door, and headed to the next topic of discussion.