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

In the confidential cubicle late at night, Jiang Ming pressed his finger on Karl Kranz's name, and dark gold patterns appeared on the pages of the Tongtianlu book. The desktop, lamp, and Russian files sank into the distance as his consciousness faded from view.

When the scene became clear again, the rough wooden wind tunnel occupied half of the laboratory. The pulleys drove the blades to rotate continuously. Ballistic drawings, brass goniometers, and several dissected spinning projectile models were scattered on the oak table. The air was filled with the smell of engine oil and gunpowder burning.

An elderly man in a woolen vest was adjusting a model stand, his cuffs covered in black dust. After listening to Jiang Ming explain his purpose, he simply stretched out his hand toward the table, asking him to produce the disputed data.

Jiang Ming laid out the side deviation coefficient matrix of the low Mach range of the Soviet Union on the oak table, and then pointed out the deviation law of 0.02% at different angles of attack to the other party. Krantz glanced at the two columns of numbers, and then pressed the corner of the paper with his pipe and pushed it outward.

The drawing slipped to the ground, and the old man walked to the blackboard, writing down the velocity, projectile diameter, air viscosity, and sideslip angle with chalk. He then connected the Reynolds number with the lateral separation position.

"This kind of table is suitable for people who only look at the summary numbers. It makes the air too orderly. Once a real projectile enters the low Mach region with a sideslip, the boundary layer on the leeward side will detach from one side first."

He drew the cross-section of the projectile. The pressure distribution on the windward side remained continuous, while the two separation lines on the leeward side moved with the sideslip angle. One of them crossed the critical position first, while the other continued to attach, thus forming cross-flow vortices of varying strengths at the tail.

When the two vortices fall off alternately, the center of lateral pressure will cross the axis of the projectile. The assumption that the lateral force coefficient changes linearly with the angle of attack will then fail, and the curve will show changes in slope, local plateaus, or even short-range reverse bending.

Jiang Ming stared at the separation line on the blackboard and marked several fluctuations in the original summary from the Soviet side next to the same operating conditions. They all happened to fall in the interval where low Mach number and small sideslip angle overlapped.

Kranz continued writing down the crossflow velocity components, splitting the local pressure integral into the attachment zone and the separation zone, and then connecting the two sides with a separation position function that varies with the sideslip angle. As a result, the originally smooth sideslip coefficient has an additional nonlinear term.

"Wind tunnel supports, surface roughness, and tail fin gaps will change the jump position, so the scatter points of each test will inevitably be different. Parameter adjustment can fit the main trend, and the critical slope must be retained."

Jiang Ming picked up another piece of chalk and wrote the maximum wind shear in Jiuquan in August on the right side of the blackboard. He then calculated the crosswind speed according to the height level and substituted the effective sideslip angle, dynamic pressure change and the response time of the program integrator one by one.

The shear layer in the Northwest Sounding Records just happened to cause the projectile to pass through two separation critical points in succession. If the Soviet smooth curve is used, the controller will underestimate the lateral force in the first segment and then compensate for it in the second segment according to the incorrect slope.

Krantz stood on the right and, together with Jiang Ming, derived the equations from the aerodynamic and control ends toward the middle. The chalk lines on the blackboard kept intersecting and eventually merged into the lateral velocity and position integral at the moment of shutdown.

Jiang Ming added the output limit of the integral controller, but the result was still that it accumulated in the wrong direction. Especially after the thrust descent in the tail phase, the rudder effect decayed faster than the integral quantity was released, and the misjudgment formed in the early stage would be directly brought into the free flight phase.

When the derivation reaches the last line, an amplification term controlled by the derivative of the separation position appears in the landing point scattering formula. As long as the wind shear crosses the critical zone, the error changes from a general linear deviation to a continuously accumulating nonlinear yaw.

Kranz took off his pipe, looked at the two-kilometer increase in lateral deviation calculated by Jiang Ming, and drew a diagonal line in the center of the Soviet matrix with chalk.

"Take this set to the target and your missiles will waltz in the sky by themselves, and the people on the ground will think that the controller is working extra hard."

Jiang Ming continued to press on how to prove the separation jump under the existing conditions. Kranz pointed out that three sets of sideslip angles can be used to perform piecewise sensitivity verification and compare the residual signs of the linear model and the critical separation model.

If the smoothing parameters are true, the residuals should change continuously with the wind shear amplitude. If the critical term is deleted or modified, the residuals will change direction on both sides of the separation point and correspond to the original wind tunnel fluctuation range.

This approach only requires existing aerodynamic instruments, Jiuquan radiosonde data, and overall group computing equipment. It can avoid dependence on the original wind tunnel conditions provided by the Soviet Union and also allow the dispute to be resolved based on repeatable Chinese data.

With the deadline for the psychic communication approaching, Jiang Ming memorized the crossflow separation position function, the lateral force integral formula, and the three sets of sensitivity verification conditions. Meanwhile, Krantz straightened the wind tunnel model again and urged him to return to his test site.

When the lamplight returned to the cubicle, the Russian file on the table was still on page twelve, and the clock on the wall had only moved forward a short distance in reality. Jiang Ming immediately took out his pen and transcribed the formula he had just learned into his brown paper notebook.

He traced the derivation back to the intersection of von Kármán's rotating flow theory, publicly available ballistic literature, and the original Soviet summary, and then used measured wind shear in Jiuquan to complete the local parameter closure, thus enabling the entire analysis to be independently recalculated.

A one-page outline of aerodynamic nonlinear sensitivity under wind shear was quickly written, with only three issues to be verified at the beginning: whether the separation critical point exists, whether the residual sign has reversed, and whether the smoothing coefficient causes inverse integral compensation.

Jiang Ming did not expand it into a formal report. The large-scale circulation of the report before the demonstration meeting would give the Soviet side time to prepare alternative explanations. The ordinary security review was proposed first at the round table, and the model was handed over after the other party expressed its opinion. This made it easier to lock in the focus of the dispute.

He folded the outline and tucked it into a separate canvas file bag close to his body. He also placed Ren Xinmin's recalculation paper in the back layer. The two sets of calculations, one from the engineering input and the other from the underlying aerodynamic model, were independent of each other but pointed to the same risk range.

As dawn broke outside the window, the sound of a jeep starting up came from downstairs. The guard honked the horn once to remind everyone that the vehicle for the seminar had arrived.

Jiang Ming changed into a blue canvas work uniform, fastened the document bag, and took an enamel mug and guidance data with him. He kept his pace steady as he went downstairs, repeatedly checking the order of the three sets of sensitivity conditions in his mind.

Ren Xinmin sat in the back seat of the car, a half-smoked cigarette between his fingers. He saw Jiang Ming holding the file bag in his arms and asked only one question.

"Found it?"

"Find a way to let the air be the witness."

Ren Xinmin put the cigarette into the car's metal box, stepped aside to make room, and left the rest of the conversation to the conference table. At this moment, the two of them shared the same judgment: extreme wind shear must be verified before the parameters are frozen.

The jeep drove into the confidential compound in the west of the city. After the documents were verified at several checkpoints, the long table in the main conference room was already filled with experts in overall design, aerodynamics, guidance, and engine.

In front of Qian Xuesen was an agenda and a Parker pen. Across from him, the silver-haired advisor Vasily was having a translator organize documents. A thick Russian original was placed in the center of the table, with two red top-secret seals facing the Chinese seats.

As soon as Jiang Ming sat down next to Ren Xinmin, Vasily raised his hand and pressed down on the cover of the dossier, indicating that the meeting could begin.