I started with a ship full of max-level veterans, and I'm just a complete noob.

Ren Xinmin closed his notebook and followed the others out of the conference room.

The overall interface discussion, which was just added to the agenda, is scheduled for the afternoon, and his original return time has been postponed.

In the corridor, the major general took the teacup handed to him by his bodyguard, walked over to Qian Xuesen, and talked about the new arrangements revealed by the Soviet advisors last week.

"They said they could provide another batch of data next month, including engine hot-fire test data and ballistic test and firing records."

Qian Xuesen pressed down on the cup lid, his gaze sweeping across the corridor and landing on the closed confidential door.

"First, let the guidance team test their own correction model. Only with a foundation of independent judgment can the Soviet data be used appropriately."

The major general switched the teacup to his other hand.

Are you worried they'll include the applicable conditions in the data?

"Data always carries the characteristics of the testing ground, equipment conditions, and design habits. Directly copying data can easily lead to treating someone else's choice as the only answer."

Qian Xuesen stopped there.

The major general nodded and turned to instruct the meeting secretary to list out the time when the Soviet documents were received.

A few steps away, Jiang Ming was standing by the window, using the afternoon light to look through the calculation sheets he had left behind that morning.

Comrade Song stood guard on one side of the path leading to the stairs, while Ren Xinmin walked towards them with a teacup in his hand.

The bottom of the enamel cup touched the windowsill with a soft sound. Ren Xinmin stood next to Jiang Ming, the tea in the cup still steaming.

"The ballistic sensitivity coefficient you used was derived from the partial derivative of the range equation with respect to atmospheric parameters?"

Jiang Ming turned to the second page of the calculation sheet and moved his finger along the speed loss term to the shutdown state variable.

"First, write the density profile as a baseline value with a small perturbation, then linearize the integral of the drag during the ascent phase to obtain the changes in shutdown velocity and trajectory inclination. Finally, substitute these values ​​into the range equation and perform partial derivatives with respect to the shutdown state."

Ren Xinmin looked down at the two-level transmission relationship on the paper and pressed for more information.

"Density perturbations directly enter the drag term, and seasonal variations will change the integration interval. How do you handle the tropopause height?"

"Treating the tropopause as the moving boundary, the change in the density function is counted as one term, the movement of the upper limit of integration is counted as another term, and the two terms are combined and transmitted to the shutdown state."

Jiang Ming took out a pencil, added a boundary change term to the margin of the page, and then connected it with the velocity loss range obtained last night.

"The main errors in Jiuquan during the summer are concentrated between 11 and 13 kilometers. This section is stratified separately, and the errors after linearization are still within a controllable range."

After reading the formula, Ren Xinmin reached out and pushed the enamel mug towards the inside of the windowsill.

"Have you considered the sensitivity of the engine shutdown signal delay to the landing point?"

Jiang Ming stopped collecting the papers and reviewed the shutdown delay table from his memory in the Soviet parameter package.

"The complete values ​​have not yet been calculated, but the structure can be determined first. If the shutdown command arrives late, the engine will work for a longer period of time. The extra working time is multiplied by the effective acceleration before shutdown and converted into speed increments."

He wrote down three quantities on the back of the calculation paper: shutdown time, extra velocity, and range deviation, and then connected them with arrows to the same ballistic sensitivity relationship.

"Once the extra velocity is incorporated into the range equation, it will change the shutdown velocity, shutdown altitude, and trajectory inclination, with the velocity term contributing the most."

Ren Xinmin took a pencil and added two sources next to the extra working time: relay action and thrust chamber response.

"The thrust decay process cannot be treated as completely constant."

"We can use the average effective thrust before and after shutdown to make the first round of estimation, and then use the thrust reduction curve during hot test to correct it. If the Soviet side only provides the nominal delay, we can calculate the upper and lower limits first."

Jiang Ming wrote the average thrust into the molecule and then connected the arrow to the atmospheric density sensitivity formula from the morning.

"This term uses the same mathematical structure as atmospheric density sensitivity, but the inputs are different. Atmospheric error is entered from drag integral, and shutdown delay is entered from velocity increment. In the end, they are both mapped to the landing point dispersion."

Ren Xinmin took out a grid notebook from the pocket of his Zhongshan suit, turned to the blank page he had just folded, and wrote down the two input paths Jiang Ming had mentioned at the top of the page.

"Go back and calculate it, then submit it to me before the next meeting."

"Okay, I'll combine the nominal value, upper and lower bounds, and three error terms into one calculation."

Ren Xinmin closed his notebook, picked up the tea that had gone cold, and walked straight towards the conference room.

Jiang Ming put the calculation paper into his canvas bag, and only when he saw the corner of the notebook sticking out of his pocket did he realize that this conversation had gone beyond a normal Q&A session and had become a clear technical collaboration.

After the tea break, the complete parameter package was turned to the lateral stability control section, and the returning control expert hung the connection diagrams for the R-2 rudder, attitude gyroscope, and mechanical integrator on the rack.

The Soviet design employs single-channel proportional control. The attitude gyroscope outputs a deviation signal, which is amplified to drive the servo motor. The mechanical integrator accumulates long-term deviations to eliminate steady-state errors left by the proportional circuit.

The presenter introduced the parameters of each component along the signal channel, while Jiang Ming recorded the proportional gain, servo response and gyroscope drift range, and compared them with the height program in the parameter table.

As the flight altitude increases, the atmospheric density continues to decrease, and the dynamic pressure decreases accordingly. The amount of deflection required for the rudder to generate the same control torque will gradually increase, and the controlled object itself will also change.

The mechanical integrator column only lists a single reset time, which remains fixed from launch until the engine shuts down. There is also no program mechanism next to the parameter table that switches according to altitude or dynamic pressure.

Jiang Ming wrote the lateral motion equations at the bottom of his notebook, linked the rudder efficiency with the dynamic pressure, and then connected the fixed integral reset time to the closed-loop response.

When the dynamic pressure is high at low altitude, the fixed reset can still catch up with the attitude deviation. However, when the dynamic pressure drops at high altitude, the rudder effect weakens. The same integral accumulation speed will cause the control correction to lag behind the change of the object. Long-term deviations may also be released in a concentrated manner before shutdown.

He tore off a narrow piece of paper, wrote down that the fixed integral reset time was disconnected from the dynamic pressure change, and marked that the high-gain program should be reviewed in the horizontal topic.

The note was passed along the edge of the table to Qian Xuesen. After reading it, Qian Xuesen turned it over, wrote a line with a pen, and then passed it back along the same path.

"We'll elaborate on that in a future cross-disciplinary feature; today's topic is broad enough."

Jiang Ming folded the note and put it in his pocket, then refocused on the speaker's system diagram, without opening any new points of contention in the current agenda.

After 5 p.m., the first round of review of the three parts—shutdown signal, lateral control, and overall interface—was completed. The Major General closed the parameter package and announced that the next demonstration meeting would be scheduled for two weeks later.

"The guidance team submitted a draft of the low-latitude atmospheric density correction model, and a simulation verification plan for the Earth rotation coupling correction also needs to be developed. The overall team is responsible for the data interface, and the ballistic team is responsible for cross-verification."

Ren Xinmin pushed his notebook next to the agenda and then added to the agenda.

"Add one more item: quantitative analysis of engine shutdown delay sensitivity."

After he finished speaking, he looked at Jiang Ming, who noted the task down at the top of the schedule page, with two entries marked next to it: the Soviet Union's nominal value of 80 milliseconds and the hot test correction.

After the meeting, Qian Xuesen stayed at the head of the table to organize the documents. When the security officer took away the parameter package, he asked Jiang Ming to put the canvas bag back on the table.

"I have reviewed your draft reply to Mr. von Kármán. The temperature potential transformation and boundary conditions have been preserved, and the format has been processed."

He took out a signed reply envelope from his briefcase; the cover already had the forwarding number from the International Exchange Office of the Chinese Academy of Sciences filled in.

"It will be sent out tomorrow. This is the second formal reply; we await Pasadena's assessment."

Jiang Ming checked the signature area and then put the envelope back to Qian Xuesen's side.

Qian Xuesen then picked up a copy of the letter from the Soviet advisor and placed his finger under the words "more complete parameter package".

"The Soviet side offered the data voluntarily, either because they genuinely wanted to help us shorten the testing cycle, or because they wanted to lock our design habits into their solutions."

He pushed the copy in front of Jiang Ming.

"We will modify the model as before and collect the data, but we must retain the right to make our own judgments. In particular, we should first see which layer they are willing to provide the data for in the actual measurements."

Jiang Ming wrote this sentence below the shutdown delay task, and then listed three verification items: the landing point of each shot, the weather at the test site, and the handling of abnormal missiles.

After returning to the institute tomorrow, he will first handle the preliminary research plan for receiving the equipment, and then calculate the relationship between the 80-millisecond shutdown delay and ballistic sensitivity.

Qian Xuesen glanced at the arrangement page, then raised his hand to close the letter from the Soviet side.

"First, settle your own accounts, then wait for their records."