Chapter 561 I really fell to my knees
"."
in the classroom.
Hearing these words coming out of Xu Yun's mouth.
Master Qian and many other members of the ‘Zhu Xian Sword’ team were all stunned.
Don't hit him after you tell him?
What does this mean?
Could it be that Xu Yun was going to say something like "I'm not targeting anyone, but you are all rubbish"?
But soon.
Qian Wushi figured out what Xu Yun meant:
This guy is afraid that he will be beaten if his request is too outrageous
So he smiled heartily, waved his hand quite grandly, and said to Xu Yun:
"Comrade Han Li, you don't have to be burdened, just say whatever you think."
"It doesn't matter whether it's colorful black, or whether you want to enlarge a certain part and shrink it a little - whether it can be done or not is the business of our project team."
"The reason why I asked you to be my assistant is because I thought you could come up with some unique insights?"
"."
Hearing what Qian Wushi said.
Xu Yun, who had intended to express his inner thoughts, no longer hesitated and said directly:
"Director Qian, do you still remember the waverider technology we just talked about outside?"
Master Qian nodded:
"Of course I remember."
Xu Yun made a free falling motion from top to bottom with his fingers and said:
"According to the original design, after the 'Zhu Xian Sword' missile falls from an altitude of 30,000 meters, its falling speed will soon approach the speed of sound, and it will always collide with the oncoming air."
"The air accumulates and compresses in front, causing the temperature to rise and converting kinetic energy into heat and taking it away."
"At the same time, the air pressure difference before and after the missile will produce air resistance, giving the missile a reverse acceleration, which is the so-called overload."
Hearing this sentence thrown by Xu Yun.
Master Qian nodded slightly again.
As everyone knows.
Gas compression is a common situation in missiles and aircraft, which can lead to overload and heating - friction is a secondary factor.
The greater the overload of the aircraft.
This means that the greater the air pressure in front, the more intense the compression, and the stronger the heat generated.
Then Xu Yun paused and continued to explain:
"In addition, the density of the atmosphere at high altitude is also an environmental factor that cannot be ignored."
"With the density of the atmosphere, the sentence 'gravity is always greater than the centripetal force required for missiles to rotate around the earth' can be realized."
"Based on the above points, I have an immature idea, that is."
"Can we design a projectile that, with a certain launch angle, can complete a trajectory similar to [ ], from high to low during the entire flight?"
"The entire turning process is completed through the aerodynamic structure. In this way, we only need to prepare the lateral propellant needed for the final sprint stage."
"?!"
Hearing Xu Yun's words.
Qian Wushi on the side was suddenly stunned, and everyone else at the scene also fell silent.
After a while.
Qian Wushi's chest rose and fell a few times, and his whole breathing rate increased.
Suddenly became anxious.
It seems
Is there any way?
To know.
According to the original design of Qian Wushi and others, the missile’s falling steps are as follows:
After leaving the Zhuxian Sword Formation platform, first perform a free fall.
This period of free fall is about more than 10,000 meters. Let's give a random value, for example, from 30,000 meters to 20,000 meters - U2 performs photography tasks at a height of 18,000 meters or even lower.
When the vertical height difference between the two sides is one or two kilometers.
Designs such as the missile's air rudder began to take effect.
The combustion of propellant generates lateral kinetic energy, which begins to turn the missile through side thrust.
Finally, the ultra-wideband proximity fuze started working, guiding the missile to hit U2.
throughout the process.
The steering of the missile can be approximately seen as a shape similar to [L].
But on the other hand.
If you want a missile falling at high speed to turn around, the thrust required here is actually very strong.
The essence of thrust is to consume the propellant in the combustion chamber.
The amount of propellant required to turn a corner is even greater than the consumption of straight-line acceleration. (doi:10.13675/j.cnki.tjjs.2203015)
But if the aerodynamic structure can be used to allow the missile to complete its steering
Then this part of the propellant may be omitted.
This way.
The volume of the entire combustion chamber can be shortened by more than half at once!
What?
You ask why not just launch at an angle of 45°?
Of course, this is because launching at an angle of 45° requires constant use of propellant to keep the missile in an oblique downward attitude. This approach consumes even more propellant than the L-type.
Looking at Master Qian deep in thought.
Xu Yun on the side slightly shrank his neck.
He probably won’t be beaten.
After all, he didn't know whether this plan was feasible.
The original inspiration for the plan he mentioned actually came from the technology used in the return of Chang'e 5 in later generations.
It’s the one that was on the hot search list back then [Waste in Space].
Of course.
The real name of this skimming technique is actually "jump re-entry", which is a very delicate operation.
This is a special case of semi-ballistic reentry, suitable for high-speed reentry into dense atmosphere.
As for the purpose
Naturally, this is to reduce overload and heating as much as possible.
Those who were Wu Gang's classmates in a previous life should know this.
The distance between the earth and the moon is actually very far.
When the probe returned from the moon, it was almost free-falling vertically toward the earth.
Gravity will continue to accelerate the detector, eventually accelerating it to a speed of 10.9KM/S.
This speed is so fast that it is only 300M/S less than the speed of the second universe.
There's no drag in space, which means you don't have to run the engine during flight, but there's also no place to apply the brakes.
Any artificial speed change requires manual application of external force.
Wait until you reach your destination.
If you don't want to land hard, that is, hit it, you have to change speed and even direction.
For the moon, you can also use rockets to forcefully neutralize the force when landing.
After all, it has small gravity and slow speed.
But for an object with such a strong gravity as the earth, this approach will not work.
The reason is simple.
The amount of change in velocity that a chemical rocket can provide depends primarily on the amount of fuel.
To increase the amount of speed change, you must increase fuel.
But this way.
Regardless of whether the combustion chamber of Chang'e-5 is enough to store fuel, the launch vehicle for launching Chang'e-5 will be increased several times. According to the previous Tsiolkovsky formula, it can be seen that the amount of energy changes with the speed. With the increase, the mass of the rocket will increase exponentially.
Therefore this approach is obviously not feasible.
Finally, after discussions from all aspects.
The design team formulated a special regression plan:
If the location of entry into the atmosphere can be precisely controlled within a range called the "reentry corridor", then the density of the atmosphere can slow down the reentry capsule.
That is to say, after the return capsule enters the atmosphere for about 60 kilometers, a bow shock wave will be formed at the bottom.
This shock wave will eject the returner into the atmosphere again, and then re-enter again.
This way.
The speed of the returner will be reduced by more than 40%.
This principle is actually the embodiment of Mr. Qian’s wave-riding body.
So just now.
After hearing Qian Wushi's inquiry, Xu Yun suddenly had an idea:
The starting conditions for the Chang'e-5 returner and the Zhuxianjian missile are actually very similar:
They all fall vertically.
It's just that one height is higher and the other is lower.
Therefore, if the launch position of the 'Zhu Xian Sword' missile can be optimized, its warhead should not be pointed vertically downward, but slightly tilted
At the same time, if we make some aerodynamic structural designs on the projectile, we might be able to achieve an effect through shock waves:
During the falling process, the projectile continuously began to deflect horizontally under the guidance of its own structure.
In the end, the initial [╲] turned into [→]. The entire process did not consume any propellant and maintained a certain degree of kinetic energy.
When it gets close to U2, the propellant combustion accelerates and the missile hits the red heart! (Note: This is a plan I came up with from a friend of the Second Artillery Equipment Research Institute. It was not my own idea. I don’t have the brains)
Of course.
This is just a picture Xu Yun came up with from a layman's perspective. He doesn't understand whether this is difficult in missile design.
In case this inspiration is in the field of missile development and colorful black is a concept.
Then Xu Yun will prepare to drink donkey hair soup.
But at present
It seemed like the situation wasn't as bad as he thought?
At least Master Qian's eyes didn't glance at the broom in the corner.
It probably took quite a while.
Master Qian just blinked and returned his gaze to reality.
I saw that he first looked at Xu Yun with a new look, then walked to Xu Yun, reached out and pressed a few times around Xu Yun's Tianling Cap.
After finding that he couldn't open it, he sighed with regret.
Xu Yun:
"????"
A few more seconds passed.
Qian Wushi just spoke slowly:
"Comrade Han Li, to tell you the truth, I really want to see how your brain grew."
"Using shock waves and launch angles for aerodynamic optimization is awesome."
Qian Wushi made a faint mouth gesture with the word "sao".
But in the end, he changed to a few more peaceful words:
“It’s so wild and unrealistic.”
See this situation.
Xu Yun couldn't help but feel happy, and tentatively asked Master Qian:
"Director Qian, so...my idea is actually feasible?"
Upon hearing this, Master Qian suppressed the emotion on his face, pondered for a moment, and said seriously:
"Comrade Han Li, your idea is very strange, but whether it is feasible or not. I can only say that there is a certain probability."
"After all, the common condition for shock waves is supersonic speed, and it is actually very difficult for a 30,000-meter missile to reach supersonic speed after dipping at a certain inclination - after all, the location of U2 is not on the ground, but at 10,000 meters or even close to 20,000 meters. Meter height ”
"Of course, high subsonic speeds can also produce local shock waves, but we don't have any data to refer to this structural curve."
"So I can only say that there is a certain feasibility, but whether it can be implemented in the short term."
"More detailed derivation calculations of Mach number and aerodynamic structure are also needed."
When it comes to business, Master Qian's expression becomes serious.
Just as he said.
Xu Yun's idea is very innovative, but it is very difficult to implement it technically.
Because this involves the concept of Mach number.
What is Mach number?
This first requires mentioning a concept:
That is, when aircraft fly at supersonic speeds, their speed often does not change. What really changes is the speed of sound in the air.
This is because low-altitude flight and high-altitude flight are two completely different concepts, and there is a big difference in atmospheric temperature between the two.
therefore.
The same speed may be supersonic at high altitudes, but is often subsonic at low altitudes.
So to better differentiate between different types of flows, the real term is Mach number.
Or to be more precise
The Mach number is not only used to distinguish different types of flows. The most essential function of the Mach number is to reflect the compressed state of the fluid.
Regarding this point, you can understand it this way:
Think of air as a "spring" whose stiffness is inversely proportional to the Mach number.
So when the Mach number is small.
The stiffness of the "spring" is relatively large.
Therefore, the fluctuation caused by the speed will be easily transmitted to all positions of the "spring", and the "spring" will not be compressed.
therefore.
When the Mach number is small enough, air can be considered an incompressible fluid.
When the Mach number is larger.
The "spring" is less stiff.
The fluctuations caused by the speed can easily cause local compression of the "spring", and the air is considered to be a compressible fluid.
The concept is very simple and easy to understand.
Generally speaking.
Low-speed fluids with a Mach number less than 0.3 can be regarded as incompressible fluids.
A fluid with a Mach number greater than 0.3 is a compressible fluid.
And when the Mach number exceeds 1, shock waves will be generated.
When the Mach number has exceeded the transonic speed region.
The shock wave will not appear on the surface of the aircraft, but in front of the aircraft - the shock wave at this time is also called a breakaway shock wave.
Therefore, if we want to ensure that the Zhuxianjian missile can complete the [ ] flight with only gravitational potential energy to provide power, we must accurately determine the location where the shock wave appears.
That is.
Design of waverider-like structure.
etc!
Waverider-like body?
Think of this.
Qian Wushi suddenly realized another thing:
If this missile was really designed, wouldn't it be true that what he and Xu Yun said before about eating an axe
A few seconds passed.
Qian Wushi gritted his teeth hard.
That’s all.
If you can really build this kind of missile, what's the point of chewing two axes?
A real man should chew an ax!
all in all.
At this point.
The discussion on the general direction has come to an end for the time being, and what is left is
Structural design and calculations.
So Qian Wushi once again divided the people at the scene into three groups according to the previous method.
But it's different from before.
This time Qian Wushi no longer went out fishing with Xu Yun, but formed a fourth group to make calculations.
Another member of the team is a middle-aged man with the same round face. He looks to be in his early thirties and is a member of the computing team:
Mentioned before.
The computing team sent by the base has a total of ten people, but the previous team had three. Therefore, the earlier allocation plan was 334, and one of them was actually redundant.
Now that Qian Wushi has personally set up a fourth group, the extra people will naturally be brought in to start the fight.
According to the division of functions.
Four groups are responsible for the derivation of four configurations:
Supersonic axisymmetry,
Air-breathing propulsion power,
Two-dimensional inlet configuration,
and
Close cone design of fixed plane shape considering viscosity.
Among them, Qian Wushi and Xu Yun were responsible for the first supersonic axial symmetry, which was also the most difficult direction in the entire process.
But Xu Yun was still happy.
After all, once he was able to partner with Qian Lao, he didn't feel emotionally conflicted, but was very excited.
Not an exaggeration.
This is a supreme honor, much more glorious than being interviewed on TV or winning a certain award.
Secondly,
Supersonic axial symmetry is the field closest to fluid mechanics among the four steps, and involves a lot of fluid mechanics knowledge.
Not to mention how proficient Xu Yun is in this aspect.
At least it doesn't have to be possessed by Quincy like before, and the whole process is OvO.
Then quickly.
Each of the four groups chose a classroom and began their own calculations and derivation.
Among them, Qian Wushi and Xu Yun's group stayed in the original classroom, after all, they took care of the disabled.
"Comrade Han Li."
After everyone leaves.
Master Qian glanced at the member of the calculation team beside him, pondered for a moment, and said to Xu Yun:
"Comrade Han Li, do you know anything about supersonic axial symmetry?"
Xu Yun nodded and said:
"I don't know a little bit about it. For example, this is one of the three ways you proposed to generate a waverider."
"The remaining two are supersonic binary flow fields, and supersonic flow fields flowing through any three-dimensional configuration."
"The axisymmetric minimum wave resistance configuration can be obtained through the classical minimum resistance theory, which is the easiest way to generate a waverider."
Master Qian nodded with satisfaction.
Then he drew a relatively simple diagram on the calculation paper and said:
"Since Comrade Han Li is no stranger to supersonic axial symmetry, let's get straight to the point."
"The purpose of our team on the technical side is very simple, which is to complete the integrated design of the minimum wave resistance cone guide wave rider and the inward-turning inlet."
"The core of this design is the parameter derivation of the cone flow field within the curved surface."
Say it.
Qian Wushi took a few more documents from his side and said to Xu Yun
"Look here, this is the partial intersection line between the waverider shock surface and the inner cone shock surface that I derived in the early years."
"The curve CD is a capture profile, and the intersection point D is usually located on the center body of the reference flow field of the internally rotating inlet."
As everyone knows.
In terms of the integrated design of the forward body inlet, there are many plans in various countries at this time.
For example, Leviste used the streamline tracing method to design the lip of the inlet in a conical flow field to approximately match the two-dimensional inlet configuration.
Shinhin Takashima of Neon completed this step using the close cone method.
Stark in the UK used the variable wedge angle method - this was actually a pity. If the UK had supported his research more, the UK might have completed the research and development of the waverider precursor first.
Qian Wushi adopted the coupling design of the minimum wave resistance cone guide waverider, which was considered quite bold even in later generations.
no way.
If you don't find another way.
Xu Yun's plan has no chance of coming to fruition.
As for the document Qian Wushi produced, it was not just as simple as in the early years.
These documents were all valuable information that he sent back in advance from across the sea. They were considered unique documents at the time, and their preciousness is difficult to describe in words.
After Jin Beier reported Qian Wushi for backstabbing and Qian Wushi and his wife were imprisoned, he could no longer take or mail anything back to China.
Of course.
It was precisely because of these data that he had done across the sea that Qian Wushi chose to do this with Xu Yunmang.
Then quickly.
Master Qian drew a shock wave profile on the gap surface and wrote the intersection point D on the center body of the reference flow field of the internally rotating inlet.
Then he wrote another flow rate formula:
qm=A2kk-1p0ρ0[(pp0)2k-(pp0)k+1k]
This is the description of a complete gas under the one-dimensional isentropic steady flow, which was derived in 1954.
After writing this.
Qian Wushi's pen tip paused slightly and said to Xu Yundu:
"Comrade Han Li, what do you think should be calculated next?"
"Back pressure ratio, or area-flow rate relationship?"
Xu Yun knew that this was not the time for him to be polite, so he immediately expressed his opinion:
"Director Qian, I personally think the back pressure ratio should be better."
When he was working at Chengdu Aircraft Manufacturing Co., Ltd. in his previous life, Xu Yun once heard a colleague who was engaged in fluidics say something:
After the shock wave is generated, the entropy will increase, but the stagnation pressure will decrease.
At the same time.
The stagnation temperature before and after the shock wave remains unchanged.
So in this case.
There is a misunderstanding in calculating the area-flow velocity relationship that can only be known through supercomputing:
Without importing the compressibility coefficient, the entire formula would be completely useless.
Therefore, after Qian Wushi asked for his opinion, Xu Yun immediately put forward his own opinion - if Qian Wushi didn't ask, Xu Yun would take the initiative to speak.
And next to Xu Yun.
Qian Wushi also nodded when he heard this:
"Just what I wanted."
So soon.
Qian Wushi calculated the back pressure ratio.
The so-called back pressure ratio.
It refers to the ratio of the static pressure at the nozzle outlet to the stagnation pressure upstream of the nozzle, but in the design scheme it refers to the coupling ratio of the cone flow field and the gas.
When the cone flow field just reaches critical conditions.
When the external gas reaches the speed of sound and the gas mass flow reaches the maximum value, the back pressure ratio at this time is called the maximum back pressure ratio.
This concept is somewhat similar to MBPR in later generations, but the interpretation is closer to downstream.
Then quickly.
Xu Yun also assessed the condition of his right hand.
His right hand had not been used today and the load was 0, so he picked up a pen and paper to help write.
As everyone knows.
If the shock wave is a normal shock wave and the shock wave thickness is not considered, then the shape of the shock wave control body will be very symmetrical:
You make a scissor gesture and point your fingertips downward.
This is the diagram of the shock control volume.
The basic equation of the control volume CV consists of three continuous equations:
DΦDt=DDt∫V(r,t)dV=t∫V(r,t)dV+∮S(r,t)undA
ΔN=(IIσρdτ+IIIσρdτ))t+Δt(IIσρpdτ)t
limΔt→0(Iσρdτ)t+ΔtΔt=CSinσV→dA→=CSinσρVcosαdA (Let’s just make do with the layout at the starting point)
where t is time;
Fx is the component of the force on the x-axis of the fluid in the control body;
v is the fluid velocity vector;
A is the surface area vector of the control body;
V is the volume of the control volume.
At the same time, the steady flow of gas is considered, and the speed and energy are assumed to be uniform on the shock wave cross section.
Then there is ∫CSv·dA=cA.
Xu Yun then connected the cross-sectional states together and prepared to continue the derivation.
But half a minute later.
Xu Yun suddenly frowned, clicked his tongue, and shook his head slightly:
"No, if we fit it like this, we can't continue the calculation."
As a result, the words just fell out.
Xu Yun suddenly heard a voice in his ears:
"Comrade Han Li, why can't we continue the calculation?"
"?"
Xu Yun was suddenly startled and looked towards the speaker.
After turning his head.
He discovered that the round-faced middle-aged man from the calculation team, who was called "greater than", had arrived beside him at some point.
Seeing this, Xu Yun glanced at Qian Wushi, who was lowering his head and calculating, and explained in a low voice:
"Isn't it obvious that he is bigger than a comrade?"
"The temperature after the shock wave is higher than before the shock wave is generated, the pressure rises sharply intermittently, and the equation of the diffusion section obviously cannot be calculated."
Say it.
Xu Yun shook his head and prepared to think of another method.
However, what surprised him was.
The round-faced middle-aged man did not speak after hearing this, but also lowered his head and started writing with a pen and paper.
Seeing this, Xu Yun said nothing and continued to think.
About three or four minutes passed.
The middle-aged man suddenly handed the calculation paper to Xu Yun and said:
"Comrade Han Li, look at this."
Xu Yun was still in a period of interruption in his thinking. He was repeatedly disturbed by others, but he still had some ideas in his mind.
Disgust is out of the question.
But there’s definitely a bit of impatience.
After all, this is a quasi-axiom that has been established in 2023 for future generations. In Xu Yun's opinion, there is no need for much discussion.
However, out of respect for the ancestors of this era, Xu Yun decided to help this comrade find the problem first and teach him a simple lesson.
The result is the first time you see the contents of the calculation paper.
Xu Yun's pupils suddenly shrank.
I only see this moment.
A derivation is clearly written on the calculation paper:
[Known ρd/ρu=(k+1)Ma2u/2+(k1)Ma2u]
【And y=pd/pu√[2kx2(k1)k+1]^1/2】
[Synthesize the above two equations to establish the continuity equation, N-S equation, energy equation and gas state equation of compressible viscous gas in two-dimensional cylindrical coordinates]
[It can be seen from the variation that the cross-sectional state will gradually increase in the second half of the diffusion section, and the final formula can be obtained after introducing the influence of the gas boundary layer]
【∑F→cv=tcvV→ρdB+csV→ρ(V→n→)dA】
"???????"
Look at the calculation results in front of you.
Xu Yun was violently shaken in his heart.
I subconsciously asked:
"Comrade Da, what do you call me? - I'm asking for your full name."
"Are you talking about me?"
The round-faced middle-aged man named Da Da adjusted his glasses when he heard this, and said with a very honest smile:
"My name is Yu Min. Hey, Comrade Han Li, why did you fall?" (End of Chapter)