Chapter 36: Watching from the Sidelines

"Indeed, this must be error analysis and statistical modeling. It utilizes probabilistic statistical quantification to create errors, simulating the impact of engine thrust deviations and environmental disturbances on trajectories."

"And here, this must be the dynamic trajectory correction equation system. It uses the inertial navigation system, constrained by gyroscope drift and accelerometer noise, to perform dynamic trajectory correction! Exactly—the linear recursive least-squares filter simplified here, combined with the piecewise stationary error model he provided, can effectively rectify mid-course and terminal ballistic deviations."

"Furthermore, this section simplifies the conversion problem between the Earth-centered coordinate system, the missile body coordinate system, and the target coordinate system into matrix operations, which is used for generating guidance commands. By predicting the impact point through angle vector projection during terminal guidance, we can not only improve accuracy now but also reduce the demand for real-time computing in the future, even if we develop infrared-guided missiles."

With the notebook for cross-reference, Qian Xuesen was able to decipher even more information from the mathematical models before him.

The middle-aged man beside him keenly caught the sensitive term: "Infrared-guided missiles? Can this be used for infrared-guided missiles?"

It was no wonder he was so sensitive; the shadow cast by infrared-guided missiles over China was profound. The very first combat application of an infrared-guided air-to-air missile had involved China. The sting of being technologically suppressed in that manner was too bitter, and everyone in China's military-industrial sector remembered it vividly.

"It cannot be used to manufacture infrared-guided missiles, but it can be used to optimize them. The greatest technological gap between us and America lies in materials science. I have consulted with colleagues at the Shenhai Electronics Institute, the Shencheng Materials Institute, and the Xi'an Engine Institute; the biggest reason why projects have been stalled in the past lies exactly there."

"The Americans' AIM-9B uses lead sulfide infrared photosensitive elements. We lack high-purity lead sulfide single-crystal growth technology. If we use domestic lead sulfide detectors, the sensitivity is at most 70% of theirs. Their detection range is 8km, while our theoretical range is only 5km. Furthermore, missile seekers require high-precision germanium lenses; we simply cannot mass-produce aspheric lenses with a polish reaching one-tenth of the wavelength. We have to rely on manual grinding, and the yield is not even 5%."

"Added to our comprehensive backwardness in signal processing circuits, solid propellants, and airframe structures, even if we spent the time to build one, it would be outdated, and more importantly, it wouldn't be functional. But now, with angle vector projection for impact point prediction, even if we have a gap, we can reach a level that is sufficient. To put it simply, in the past, even if we built and launched one, we couldn't hit the target. But based on angle vector projection for impact point prediction, we at least have a probability of hitting the target. In the future, if our technology in materials, circuits, and photosensitive elements catches up, we could even become more precise than their Sidewinders!"

Three hours passed in the blink of an eye. The darkness gradually retreated, and the east began to pale with the coming dawn.

***

For China, however, there were far too many preparations to be made. Once it was confirmed that the models Lin Ran sent back were immensely beneficial in all aspects, the entire massive machine began to operate at an unprecedented speed. Qian Xuesen had no time to rest; he was immediately arranged to board a special flight to Bingcheng to conduct a comprehensive upgrade of the DF-1 missile using the new models.

The latest news from the south would be synchronized to him via telegram the moment it arrived. By his estimation, using the models provided by Lin Ran to optimize the DF-1 could improve the accuracy of the missile to within a 1-kilometer radius. Setting aside whether it was usable or not, this was already at an international top-tier level—capable of earning foreign exchange through exports. Once successfully verified, it would also be a direct slap in the face to the Soviet experts who had withdrawn.

In addition to Qian Xuesen, Hua Luogeng was also urgently transferred to a new unit. Because the models Qian Xuesen understood were those translated by Chen Jingrun into a language he could comprehend, and many other models remained hidden in obscure mathematical language, mathematicians were urgently needed to decipher them. In just one night, Chen Jingrun had finished the ones that were easier to interpret; the rest were the "hard bones."

"Academician Hua, your work requires certain changes. You may have very little time to reunite with your family. Are you willing to participate?"

Hua Luogeng was a sharp man; he guessed the reason immediately. "The country has a need, and I will not shirk my duty."

...

Hong Kong, Modern Stage.

"Ms. Meng, Professor Lin is at the door," the housekeeper, Sister Liu, whispered as she entered Meng Xiaodong's room.

Meng Xiaodong, a famous Peking Opera performer known as the "Empress of Winter," was living in seclusion in Hong Kong and had long since stopped performing on stage. Not performing did not mean she was indifferent to current events; naturally, she was quite curious about this figure who had stirred up Hong Kong that summer. From the newspapers alone, he was young, handsome, and immensely talented—praised by the Hong Kong media as a once-in-a-century mathematical genius.

She was even more curious about why he had come to see her. Three years ago, Zhang Shizhao had come to persuade her to return. In her view, the only value she had left was to go back and teach, but Professor Lin was an American professor—could it be that he wanted to persuade her to go to America? There was also the possibility that he was a fan of her performances and wanted to meet her in person.

However, considering his age, that possibility seemed pitifully slim. Nevertheless, Meng Xiaodong did not decline the request for a meeting; she was even quite expectant to know the motive of such a talent.

"Professor Lin truly lives up to his reputation. Not only is he dashing, but his entire demeanor is that of a quintessential scholar," Meng Xiaodong complimented.

"Thank you for the praise, Ms. Meng. I have come today to ask if you could help me record a short song." Lin Ran reached into his suit pocket and handed a sheet of staff notation to her.

This intent was indeed something she had not expected. Meng Xiaodong picked up the music; aside from the neat handwriting, the title made her eyes light up: "Watching from the Wall?"

After reading it, she tried humming a small section:

"...
Departing now, the dust settles on the banquet,
How can I not notice the fading of youthful faces?
The murals of the past, once brilliant,
Awaken only to watch from the wall...
..."

One thing that could not be avoided when coming to Hong Kong was accepting interviews. More accurately, Lin Ran also needed to accept interviews, and this song, "Watching from the Wall," was carefully selected for that purpose.

The moment you arrive in Hong Kong, the other side develops a world-class short-range missile. Perhaps it doesn't matter now, but after Lin Ran makes waves in the American aerospace industry, it would be no surprise if certain departments or people dug this up to make an issue of it. A song like "Watching from the Wall" might not be truly effective on its own, but what he needed most was to cooperate with General Electric to secure NASA orders, proving his indispensability so that the Morgan family and the Rockefeller family behind Professor Horkheimer would join forces to protect him.

But for them to protect him, they needed a public justification, and "Watching from the Wall" was the song he prepared to express his stance. Another song, intended for the Chinese side, was "My People, My Country."

After Meng Xiaodong finished singing, she clapped repeatedly, the sound echoing softly in the living room: "Good song, good melody, good sentiment, and good metaphor. It is a pity that Professor Lin found the wrong person; I am a *kunsheng* (male role actor), not a *danjiao* (female role actor)."