How to transfer Chapter 692? (Work is complicated, I will post two chapters first, and there will be another chapter at pm)
"Compared to the Magnus effect, the benefits of a certain amount of rotation far outweigh the secondary effects of the Magnus effect, so the necessary rotation cannot be reduced, and we cannot give up because of fear of failure. Moreover, among the means of improving accuracy, this kind of rotation is one of the lowest-cost ways."

The comrades from Changfeng Factory and Fenglei Factory finally understood why Gao Zhendong had been talking about rotational stability.

"For example, the problems caused by long projectiles are far more than the ones we just discussed. For example, there is a problem that can be thought of intuitively without any theory. That is the phenomenon of the long projectile falling when it leaves the tube."

This example is very intuitive. Although the bullets they have always made are short and thick and have not encountered this problem, it did not affect the comrades from the two factories at all. They imagined the situation just through Gao Zhendong's description.

As the projectile becomes longer, the center of gravity moves forward. When the rocket leaves the directional tube, once the center of gravity leaves the tube mouth, the projectile tends to fall. And it is very obvious. Anyone who has studied junior high school physics can imagine that this phenomenon is more obvious the longer the projectile.

For a rocket, this means that its direction goes astray as soon as it leaves the air.

"Yes, Chief Engineer Gao's reminder is indeed true. It is the simplest lever principle. Moreover, as the rocket moves further out of the directional tube, the fulcrum moves further away from the center of gravity of the rocket, and this phenomenon becomes more obvious."

You don't even need to do any actual experimenting, just fill it in your mind.

Another comrade thought about it and made a suggestion: "Then we move the center of gravity of the rocket as far back as possible, so that it leaves the nozzle as late as possible. Can this solve the problem?"

Without Gao Zhendong's advice, some comrades objected: "That's definitely not possible. First, the structure and function of the rocket determine that it is impossible to move the center of gravity backwards. Second, the further the center of gravity is moved backwards, the easier it is for the oncoming airflow to affect the flight state of the rocket, and it will be even more unstable."

Seeing that this idea was not working, some comrades suggested increasing the initial velocity of the rocket.

Rockets are different from artillery shells. Artillery shells reach their peak as soon as they debut, and their muzzle velocity is when their speed is the highest. Rockets are the opposite. They move first, then develop slowly, and accelerate during flight.

This means that at the beginning, its speed is not high and the projectile has no lift, so the impact of the nose-fall phenomenon is greater.

This comrade's idea is to throw the rocket out as quickly as possible before anyone notices it, so that it can fly!
Then a comrade did some mental calculations and laughed bitterly: "I can't figure out how fast this speed should be for now, but the estimated value will have a significant impact on rockets and even rocket artillery. Moreover, this method does not solve the problem from the root."

After discussing it for a long time, everyone felt that this was indeed the case. After thinking about it, they couldn't find a simple, convenient and cheap solution. Finally, they remembered what Gao Zhendong had said just now.

"What should we do? I think Chief Engineer Gao has already said that we should rotate the missile body while it is still in the launch tube."

It seems that Chief Engineer Gao is right, we still have to rotate the projectile.

The rotating projectile can reduce this effect to a great extent. The precession of the gyroscope is a good thing. There is a reason why rotational stabilization is used in everything from guns and artillery shells to rockets.

At this time, the comrades realized a big problem: how to make this thing turn in the pipe?
When the rocket was just started, its speed was the lowest. Not to mention the tail fins that had not yet unfolded in the tube, even the small wings at the tip of the missile that had already stretched out did not have enough power to turn the thing.

"Do we still need to use turbine engines? Isn't this going back to the old ways?"

This is actually an old question. I don't know about other things, but both the Russians and our rockets, as long as they have a certain range, will start rotating while leaving the barrel.

Among them, our later foreign trade 80km 273mm rocket is quite interesting. It looks like a box-type launcher, but in fact it does not use a directional tube, but a directional guide rail. Some technologies cannot be used. The 273 rocket is heavy, and it cannot be turned by ordinary methods.

Finally, they used a powerful method to achieve miracles, and installed a spinning engine on the head of the rocket! Use the small rocket engine on the head of the rocket to spin it up when it is launched!
Everyone had almost finished their discussion and were stuck at this point. Gao Zhendong smiled and said, "It's not that difficult actually. If you want to make it work, can't you just equip the rocket launcher with rifling?"

Rifling? Chief Engineer Gao, are you confusing it with other projects?

Everyone looked at each other in astonishment, including the comrades from the Land Equipment Bureau.

Seeing that no one knew what to say, Gao Zhendong drew a directional tube on the blackboard, and then drew an arc on the directional tube.

"The term rifling is just a metaphor. In fact, it is to make a rotating groove on the rocket launcher's directional tube, and install a corresponding bump on the rocket to get stuck inside it. As the rocket moves outward, the bump forces the rocket to rotate. The speed of rotation and the final effect can be determined based on the rocket's muzzle velocity and the pitch of the groove."

How can this be done?

The comrades' eyes almost popped out when they looked at the abstract "guide groove" in the picture.

But the more I think about it, damn, it seems like it might really be possible!
First of all, this method can indeed make the rocket spin during the launching process as needed.

Secondly, this thing has no difficulty or threshold for rockets, and has little impact on costs. Finally, the processing of this guide groove is somewhat difficult, but fortunately, this thing is processed on the directional tube of the rocket launcher, which is a one-shot deal. After the processing is completed, the rest of the work will be handed over to the guide block on the rocket. The cost and processing difficulty are generally acceptable.

The comrades from Changfeng Factory looked at Gao Zhendong and really had no idea what was going on in this comrade's head.

If you talk about theories, research, and analysis that seem very advanced, he has them, and a whole set of them, but when it comes to solutions to problems, he uses both basic and basic methods.

If you want to say that this method of adding a groove on the pipe is very advanced, it is not.

But can it solve the problem? Yes! And it can be solved very cheaply.

No, no, no, this is really advanced!

"Chief Engineer Gao, I'm convinced. This is a good idea."

Gao Zhendong smiled and said, "In fact, there are active control methods to solve the accuracy problem of rockets, such as inertial navigation correction, but that is too expensive and not realistic right now."

But it doesn’t matter if it’s unrealistic. Just sow the seeds and they will naturally sprout when the time is right.

The comrade from the Land Equipment Bureau laughed and said, "The current range is sufficient. If it is farther, our observation methods will not be able to support its use."

If 60 kilometers is barely sustainable, then a higher range is actually of little significance. If you can't see it, there is no point in hitting it.

Speaking of long range, Gao Zhendong suddenly thought of a hidden danger. He pointed to the back half of the rocket on the blackboard and said, "Pay attention to this part. When the rocket engine works long enough, the projectile may be burned through by high temperature and fall off. This is especially true for new propellants, which have a high combustion temperature. This should be considered in advance during design."

Not to mention high-temperature propellants, even ordinary propellants, Gao Zhendong knew in his previous life that this situation had occurred when he was working on 122, and it took more than a year to find the problem and solve it.

It would be best if you can avoid taking detours.

Comrades from Changfeng and Fenglei factories took note of this situation and asked Gao Zhendong: "I remember you said there are fan-out, trajectory intersection and other problems. How to solve these problems?"

Gao Zhendong shook his head. "These situations are only possible, but different designs do not necessarily appear, and the solutions are all related to your specific design. When you are working on it, you can analyze and solve them when you encounter them. If I must make a suggestion, it is that under the premise of ensuring the flight attitude of the rocket, the rotation, movement, support and other structures must be locked firmly enough during launch."

To put it simply, it is not a big deal if the launch tube is uneven on the left and right, but if it is loose, then every shot will not go the normal way.

Seeing that the work was almost done, the comrade from the Land Equipment Bureau asked, "Chief Engineer Gao, do you have any other suggestions or opinions?"

Gao Zhendong thought about it, and although he felt it was a little late, he still made a suggestion: "If possible, it is recommended to increase the caliber of large-caliber rocket launchers to more than 250mm."

Comrades from the Land Equipment Bureau and the Defense Work Committee were very surprised as to why Gao Zhendong made this suggestion.

Gao Zhendong explained: "The caliber of the terminal-sensitive bomb we are working on now is 110mm. If the large-caliber rocket is only 180mm, it means that its cross-section can only accommodate one terminal-sensitive bomb, and a lot of space is wasted. If it is increased to more than 250mm, three can be placed side by side in a triangular shape."

This is a simple geometry problem. After everyone thought about it, they realized that Gao Zhendong was right.

"Can you make the terminal-sensitive rounds smaller? 80mm?"

Gao Zhendong shook his head: "No, if it's smaller, the power cannot be guaranteed, and the sensors are difficult to arrange. The 110mm caliber is almost the limit of existing technology."

The comrades from the Land Equipment Bureau thought about it and said: "We will take this issue into consideration. If it doesn't work, we will solve it in the next generation."

When seeing off the comrades, Gao Zhendong shook hands with the comrades from Fenglei Factory very solemnly and said: "Comrades, this 40mm rocket launcher with a range of 130 kilometers is very important. I hope you will do a good job."

Then the 180mm one is not important? The comrades from several parties felt a little strange, but for them, whether Gao Zhendong said this or not, the work had to be done well. Maybe Chief Engineer Gao just said whatever he thought of.

(End of this chapter)