Rebirth of science and technology academic master

Unknowingly, Qin Yuanqing was already starting the calculation workload from the lunar orbit to the soft landing.

First, there is the main deceleration section of the first stage.

Based on the configuration characteristics of Chang'e-4 in the data, Qin Yuanqing established the working model of the navigation, guidance and control system and the center of mass and attitude dynamics model of the small lunar probe. The model takes into account the impact of thrust eccentricity and deflection of each engine, as well as the discrete operating characteristics of the guidance, navigation and control subsystems.

Then, the guidance law of the main deceleration section under the terminal horizontal speed constraint is studied.

The corresponding relationship between the orbit parameters of the Kepler orbit and the terminal motion parameters is used to convert the terminal motion parameter constraints into orbit parameter constraints, thereby converting the trajectory planning problem into a limited thrust orbit change problem, and then obtain the guidance law through the least squares correction method .

Next, the guidance law of the main deceleration section under the terminal height constraint was studied.

Subsequently, the dynamic equations in the guidance inertial polar coordinate system are established, and the target constraint is used as the state quantity. The pseudospectral method can be used to easily obtain the values ​​of some parameters.

On this basis, for a given engine configuration, the value range of the main deceleration section range was studied, and the orbit characteristics within this range were studied. Quaternions were used as parameters, and deviation quaternions were introduced to construct quasi-Eulerian The angle is used to eliminate the dual value of the target attitude, and the attitude control is designed using the time optimal control of the perturbation double integral system, trying to obtain an optimal control solution.

There is no room for error in the entire process. In fact, Qin Yuanqing broke out in a cold sweat when he learned that Chang'e-3 used the model built by Qin Yuanqing for Chang'e-2, because the model he built was a model specially built based on Chang'e-2 and the rocket. is optimal. However, Chang'e-3 has some changes compared to Chang'e-2. In other words, the optimal plan for Chang'e-2 does not mean that it is the optimal plan for Chang'e-3. It can be said that Chang'e-3 was a complete success. , it really had an element of luck, but Qin Yuanqing estimated that the original moon landing location of Chang'e-3 was definitely quite different from the calculated value.

This time Chang'e-4 has to log in from the back, which is similar in theory, but in practice the difficulty is much higher. One of the problems is the signal problem!

On the far side of the moon, wireless signals from the earth cannot be received.

Of course, China Aerospace Engineering also has a corresponding plan for this. It plans to launch a relay satellite for the Chang'e-4 lunar probe, which is the 'Queqiao'. According to the plan, the relay satellite will be allowed to reach the Earth-Moon gravitational balance point L2. , is scheduled to be launched on May 21.

The role of 'Queqiao' is to maintain communication between the Earth Control Center and the Chang'e-4 probe.

Of course, because the distance between the earth and the moon is relatively far, there is a certain delay problem in communication. This resulted in the Chang'e-4 probe's landing orbit being unable to be controlled by technicians at the Earth Control Center during the moon landing phase. This is completely equivalent to a blind landing, so the technical difficulty is more than one level higher than the landing process that can be controlled in real time.

Qin Yuanqing's calculation work was to control every parameter to an extremely precise level. In daily life, the habit of keeping 2 digits after the decimal point does not apply in aerospace engineering. Aerospace engineering pays great attention to accuracy, so Qin Yuanqing always keeps 10 digits after the decimal point to minimize the error.

Sometimes I have to say that mathematics is the most rigorous of all sciences, and mathematicians are a group of idealists who pursue perfection.

As for the landing point on the far side of the moon, Qin Yuanqing chose the SPA Basin. The SPA Basin is the largest and oldest crater on the moon, with a diameter of up to 2,500 kilometers.

At the same time, the SPA basin is 13 kilometers deep and is the deepest impact basin on the moon. This means that the impact event that year is likely to dig out materials from the depths of the lunar crust and even the lunar mantle. These may become the basis for humans to study the internal composition of the moon. key".

Once the Chang'e-4 probe makes discoveries in this area, it may further promote China's complete conquest of the moon!

Completion of the computational workload is the first step, and the second step is to build a complete model to facilitate supercomputer simulation.

If it is other mathematicians, they may only be able to complete the calculation part, and the model must be completed by other professionals, but Qin Yuanqing does not need it. He is also an expert in this aspect. This avoids the difficulty between different people in understanding each other's needs. caused by human error.

After Qin Yuanqing finished all his work, it was already a week later. Qin Yuanqing stood up, stretched and yawned. After arriving at the secret base, his working hours were considered short, including 16 hours a day, and sometimes he even worked 24 hours a day.

"Academician Qin, how are you?" Academician Ouyang asked.

"Fortunately, everything is done!" Qin Yuanqing handed the data disk to Academician Ouyang: "Then the supercomputer simulation will be left to you. I'm going to take a nap, I'm so sleepy!"

He stayed up all night last night and was so immersed in work that he didn't feel it yet. Now that work was over, Qin Yuanqing felt tired and sleepy. What he wanted to do most was to have a good sleep.

Not to mention that Qin Yuanqing went to his room to sleep, but after Academician Ouyang got the data disk, he immediately arranged for a supercomputer simulation. As an aerospace engineer, he had a supercomputer dedicated to aerospace engineering.

What made Academician Ouyang extremely happy was that there were no accidents during the entire simulation process. On the big screen, it can be clearly seen that the Chang'e-4 probe was launched into space with a rocket, then entered a predetermined orbit, then flew around the earth and entered the earth-moon orbit, and then was captured by the moon after changing orbit. After flying around the moon on a set orbit, it then entered the lunar landing orbit through orbit changes, and then continued variable speed control. The Chang'e-4 probe finally landed steadily at the scheduled landing site in the SPA basin.

After several consecutive supercomputing simulations, they all landed in the SPA basin, and the location was exactly the same.

"Sure enough, asking Academician Qin to come over for help is the wisest choice. Academician Qin solved the problem that our team has not been able to solve in a week!" Academician Ouyang muttered to himself.

In fact, before inviting Qin Yuanqing to help, their team naturally conducted calculations and supercomputing simulations, but the results were not satisfactory.

That is why, after more than a year of ups and downs, we have been unable to obtain satisfactory results. Academician Ouyang simply applied to his superiors and invited Qin Yuanqing to help solve this problem.

"Academician Ouyang, you see, including the orbit around the moon, the migration of the earth-moon orbit, the orbit around the moon, and the landing point are quite different from our original ones." A middle-aged scientist hesitated: "Isn't it inappropriate?"

"If there's anything wrong, just follow Qin Yuanqing's set of parameters and models!" Academician Ouyang said angrily: "You guys, do you still doubt Academician Qin's ability?"

With the last cooperation, Academician Ouyang is very aware of Qin Yuanqing's abilities. What's more, Qin Yuanqing has made rapid academic progress in recent years, gained worldwide recognition, and established his academic status early.

For Academician Ouyang, all he had to do was believe in Qin Yuanqing.

Even if Qin Yuanqing's calculation results were different from the supercomputing simulation, Academician Ouyang would undoubtedly choose Qin Yuanqing. What's more, supercomputer simulation is no problem.

As for inputting parameters into the original model and getting different results, Academician Ouyang didn't care at all. After all, that model was developed by Qin Yuanqing a few years ago and was aimed at Chang'e 2. But now that so many years have passed, the situation has changed. Is it necessary to use new things to adapt to the old rules?

There is no such truth.

"You should study carefully during this period of time to study why this is the case. People, you must remember to live and learn and never rest on your laurels!" Academician Ouyang said seriously.

The rest of the team couldn't help but look ashamed when they heard Academician Ouyang's words.

"In the field of aerospace engineering, we are still far behind the United States. We must not be complacent and complacent just because we have achieved some results. This is unacceptable. We are not trying to compare with others, we are trying to constantly surpass ourselves. You are comparing yourself with yourself!" Academician Ouyang said: "I am already over 70 years old, and I am no longer motivated. Our Chinese aerospace project still has to rely on you. We must always remember that our goal is not the United States, but the stars and the sea!"

Aerospace engineering is also divided into various fields, and they are only part of the lunar exploration project.

Academician Ouyang does not want to see these young people become proud and complacent, thus clinging to their own selves.

When Qin Yuanqing woke up, he slept for 12 hours. Only when he woke up did he realize that he had just completed the supercomputing simulation. There were no problems in the supercomputing simulation. The results of several supercomputing simulations were consistent.

Qin Yuanqing smiled. All this was as expected, so Qin Yuanqing said goodbye and left. Of course, when Chang'e 4 was launched, Qin Yuanqing had to participate, but this was to prevent some accidents so that they could be repaired in time.

But at that time, Qin Yuanqing could just be at the command center.

Academician Ouyang personally escorted Qin Yuanqing out of the base gate and returned to Shuimu from the secret base. Special departments used special vehicles to escort Qin Yuanqing back.

Although he slept for 12 hours, Qin Yuanqing's energy was not very good. After a week of high-intensity work, which was extremely mentally demanding, once it was over, his whole body relaxed and his mental state was not shaken.

Qin Yuanqing said hello to the office and took a three-day leave, which coincided with May Day, so Qin Yuanqing rested directly at home. As for some activities, Xu Jiayi and other vice principals participated.

Qin Yuanqing now just wants to relax and spend time with his children. He also took advantage of the May Day holiday to take his wife and children back to his hometown. After all, he hadn't been back to his hometown for a long time and was homesick.