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

Two weeks later, in the early morning, the morning mist had not yet dissipated.

Jiang Ming opened the top of the safe on time, took out the three neatly bound guidance demonstration materials, carefully put them into a canvas bag, and went with Comrade Song to the West City Confidential Compound.

The second guidance system demonstration meeting is about to begin.

Ren Xinmin was already seated on the right side of the long table, with a report on the shutdown delay sensitivity spread out in front of him, and seven pages of calculation paper independently verified by the overall team next to him.

As soon as Jiang Ming handed the materials to the meeting secretary, Ren Xinmin pushed the seven pages towards him, pointed to the last column, and said:

"The relay action, thrust chamber response, and thrust attenuation are all recalculated according to a different path, and the nominal value still falls around eighty milliseconds, with a range deviation of about 0.3 kilometers."

The two calculations used different intermediate variable names, and the final results differed by only one rounding position. Jiang Ming checked the input parameters page by page and added the hot test data to be replaced next to the thrust drop section marked by the overall group engineer.

"This can be entered into the overall interface. Once the Soviet side sends the hot test curve, we will convert the average effective thrust into the measured integral."

Ren Xinmin retrieved the calculation sheet, put the conclusions of both sides into the same folder, and then gestured to the meeting secretary to distribute the three documents to Qian Xuesen, the major general, and the seats of each professional group.

The major general first looked up the low-latitude atmospheric density correction model. He skipped the derivation process and directly found the applicable range. He drew boxes outside the two rows of Jiuquan summer and Jiuquan winter, and then checked them item by item along the monthly table of launch windows throughout the year.

The summer model uses the mean tropopause around 13.2 km, while the winter model establishes a parameter range around 12 km. A sounding correction entry is reserved between the two references, and density stratification can be regenerated based on the temperature profile of the day before launch.

"Can it cover the whole year?"

The major general pressed the pencil down on the transitional month between spring and autumn, and turned his gaze to Jiang Ming.

"Two sets of parameters are used for interpolation in spring and autumn. When abnormal sounding conditions are encountered, the seasonal average is replaced by the daily profile, and the drag table, lateral force table and thrust loss table are recalculated simultaneously."

Jiang Ming flipped to the interpolation process in the appendix, pushed it forward to the center of the long table, and at the end of the process were the format requirements for the overall group's access data.

After reviewing the interface panel, the major general picked up the second shutdown delay report, then extracted the third report on the combined calculation of the three error sources, and laid the comprehensive scatter plot flat in the center of the table.

The returning control expert left his seat, and the head of the ballistics group also came over with a slide rule. The group checked the results along three error paths: atmospheric model, Earth's rotation, and shutdown delay, and finally merged them into the root mean square composite result.

The outer circle on the map is 60% to 80% larger than the Soviet design specifications. The correction for low-latitude atmospheric density contributes the most, followed by the correction for Earth's rotation coupling. The deviation caused by the 80-millisecond shutdown delay is relatively small, but it still needs to be included in the overall error distribution.

The ballistics team leader redraws a set of boundaries with red and blue pencils, looks up and says, "If we treat the three terms as completely unidirectional superposition, the result will be worse. Root mean square synthesis is already a reasonable approach in engineering design."

"The overall team accepts this approach."

Ren Xinmin got up from his seat, opened the interface directory he had brought, and inserted the low-latitude model page into the reference parameter column.

"Subsequent ballistic simulations will use the low-latitude correction model submitted by the guidance team. The corresponding reference values ​​in the Soviet parameter package need to be corrected before they can be used. The shutdown delay will be calculated separately based on the nominal value and the upper and lower limits."

The meeting secretary copied this opinion into the minutes. Qian Xuesen reviewed the three documents item by item and checked the independent calculation results of the overall group before picking up his pen to sign after receiving the opinion.

"Yes, we can first use this model to establish our own simulation benchmark. If the Soviet side provides actual measurement records later, we can then use the records to verify the model. The order cannot be reversed."

The major general opened the military requirements group's stamp box, pressed his red stamp on the review page of the synthetic scatter plot, and after the ink settled, he signed off on the low-latitude model cover to include it in the next stage of the demonstration.

This is the second time the military requirements group has stamped the technical results submitted by Jiang Ming. The first time, they crossed out the direct use qualification of the Soviet atmospheric model, and this time they sent the modified model of the Chinese test area into the formal simulation process.

The meeting secretary collected the archived copies of the three documents, and the agenda then shifted to horizontal stability control. Jiang Ming unfolded the note he had given to Qian Xuesen after the last tea break and placed it next to the Soviet mechanical integrator structural diagram.

First, draw the dynamic pressure curve that varies with altitude on the left side of the whiteboard. Jiang Ming then marks the control surface efficiency of the ground section, mid-range section and high-altitude section according to the Soviet parameters. He then converts the fixed integral reset time into control bandwidth and draws a second line along the altitude axis.

"The Soviet solution uses single-channel proportional control with a fixed reset time for the mechanical integrator. When the dynamic pressure is sufficient in the low-altitude section, the control torque generated by the control surface is sufficient to keep up with the deviation correction."

As the chalk moved past the 20-kilometer and 30-kilometer markers, the dynamic pressure curve continued to decline, and the effective control bandwidth corresponding to the rudder effect also changed accordingly.

"After entering the high-altitude phase, the efficiency of the control surfaces decreases, and the original integral parameters continue to accumulate long-term deviations. However, the correction amount given by the control system cannot keep up with the state changes. Before shutdown, the accumulated deviations may be released in a concentrated manner."

Jiang Ming extended the bandwidth corresponding to the fixed reset time of the Soviet side to the right, and then drew the actual bandwidth range required for the high-altitude section. The two lines intersected at a distance of more than 40 kilometers.

The returning control expert first checked the formula at his seat, then took a pencil to the whiteboard and checked it segment by segment along the feedback loop from the starting point of the integral link. He then converted the dynamic pressure into the control torque of the steering surface and wrote down a set of estimated values ​​next to the intersection.

"The fixed reset time was originally intended to reduce steady-state error. However, in the rudder effect decay phase, the mismatch between the integral accumulation speed and the actuator capability can indeed lead to a concentrated correction before shutdown."

At this point, he flipped back to the Soviet appendix to look up the altitude procedure mechanism. The page only listed the fixed cam and the uniform reset time, and the relevant parameters were used from takeoff to engine shutdown.

"When I was working on automatic control, I mostly dealt with ground servo and stable platforms. After the dynamic pressure changes with altitude and enters the control bandwidth, the parameters themselves should follow the flight segment. This intersection point is worth simulating separately."

Jiang Ming redraws the integrator block diagram on the right side of the whiteboard, splitting the fixed parameters into three groups. The ground section maintains a short reset time, the middle section adjusts the integral action according to the decrease in dynamic pressure, and the high-altitude section switches to another set of parameters, leaving a transition zone before each switching point to prevent jumps.

"Mechanical implementation can use a programmed cam, which pre-stores three segments of integral parameters according to the flight time, and sets them separately for the ground segment, mid-range segment and high-altitude segment. When switching, the integral state is retained and the output change rate is limited."

The returning control expert took the chalk, added a status holding contact after the program cam, and then connected the three parameter inputs back to the same integrator.

"Switching based on flight time is easy to implement initially. If a reliable altitude signal can be obtained later, the position can be verified and switched. However, at this stage, we must first safeguard the manufacturability of the mechanical structure."

Ren Xinmin looked at the three sets of parameters, opened the summary of the No. 3 furnace temperature control previously submitted by Jiang Ming, and moved his fingertips between the proportional, integral and differential tuning tables.

"The segmented parameter switching that you verified in furnace temperature control has now been applied to ballistic control. You are also adjusting the parameters according to the object's state to account for the changes in thermal inertia before and after charging of Furnace No. 3."

"The mathematical structures are the same, but the controlled objects and actuators each have their own constraints. The furnace temperature relies on temperature measurement feedback, and the ballistic lateral stability also needs to incorporate dynamic pressure, rudder effect, and gyro error. The parameters can only be recalculated."

Jiang Ming wrote the step response form of Furnace No. 3 on the bottom edge of the whiteboard, and placed the response form of the ballistic lateral deviation side by side. The proportional, integral and differential parts of the two sets of equations corresponded one by one, but the constraints fell on the heating actuator and the servo motor torque respectively.

Qian Xuesen had been taking notes since the start of the meeting. When he saw two sets of equations side by side, he put down his Parker pen and, for the first time at this symposium, took the initiative to evaluate Jiang Ming's work.

"The ability to transfer engineering methodologies is sometimes more scarce than depth of knowledge in a single field."

After he finished speaking, he pointed to the segmented PID diagram on the whiteboard with his finger and turned to the Major General.

"The lateral stabilization correction scheme has also been incorporated into the next stage. The guidance team provides the parameter switching principles, the control team is responsible for mechanical implementation and stability verification, and the ballistics team provides dynamic pressure and rudder effect inputs at each altitude."

The major general wrote this item into the mission page, while the returning control expert tore off a piece of graph paper and began copying down the bandwidth cross-section of more than forty kilometers.

After the meeting, Jiang Minggang had just reached the corner of the corridor when Ren Xinmin called him from behind, placed his enamel mug on the windowsill, and then turned to the parameter switching page of the No. 3 furnace temperature control summary.

"Is the temperature control of the zone purification furnace using the same tuning method as the segmented PID control of the ballistics system shown on the whiteboard today?"

"With the same entry point, first test the object's response, then adjust according to the time constant and the actuator's capability, and continue to correct after the running data is available."

Ren Xinmin pressed his hand against the edge of the report and then asked, "When did you learn cybernetics?"

"The chapter on automatic control in Mr. Qian's lecture notes is the entry point. The specific tuning method is derived from the journal index and the actual test data of the equipment. Several rounds of step tests were carried out for both the No. 3 furnace and the single crystal furnace."

Ren Xinmin looked at Jiang Ming for a while, picked up the enamel cup again, nodded, and returned to the conference room along the corridor, taking the summary he had left on the windowsill with him.