The Military-industrial Scientific Research System of the Academic Master Chapter 881

Chapter 881 Trouble at the Signal Transmission Level

Although the Y-9 at this time has no blood relationship with any other model, the overall design of a military transport aircraft does not actually have much variety.

In particular, superior units and user levels have now given very clear technical index requirements.

Not to mention anything else, just "the cross-sectional area of the cargo compartment is not less than 85% of the IL-76" plus "turbofan power" do not leave much room for manipulation at the design level.

Turboprop-powered transport aircraft can also tolerate some weird designs due to their slow flying speed.

However, for jet transport aircraft whose cruising speed is generally above 600km/h, their overall aerodynamic characteristics are highly homogeneous.

Full metal semi-monocoque structure, cantilevered upper monoplane with swept back angle and T-shaped tail, hanging engine...

Basically, it is an Il-76 that has been reduced in height and shortened in length, but the width remains roughly the same.

Or in other words, it is an all-round reduced C17.

There is little room for opportunism through ingenuity.

It's basically just hard work.

The key to the success or failure of a model lies in the design at the structural level and the supplement and improvement of some details.

Radical air-blowing lift-increasing technology is too risky for a tactical twin-engine aircraft and is a design that outweighs the gain and loss.

As for winglets, Huaxia already has rich experience in past models, so it is worth a try.

In addition, tactical transport aircraft have the need to take off and land on non-paved runways, so special attention needs to be paid to the design of the engine's anti-foreign object and landing gear structure. Fortunately, even the larger IL-76 has this capability. It's not as if his eyes are completely black...

In short, almost on the way back to Nanzheng from the capital, Liang Shaoxiu had already roughly conceived the overall appearance of this plan.

What Ding Gaoheng said before was very clear.

“Take the lead with Qinfei Group”.

In other words, it can also receive support from other brother units within the aviation industry system.

Actually, this is normal.

An aircraft of 80-90 tons is not big, but for China Aviation Industry, it is still a blank slate.

We must concentrate our efforts on tackling key problems.

However, that is all after the formal establishment of the project.

The top priority is to turn Yun 9 from a demand into a formal project.

Therefore, after getting off the plane, the first thing Liang Shaoxiu did was to concentrate the main research and development forces of Qinfei Group and start deploying pre-research work...

On the other side, Chang Haonan didn't know at this time that Ding Gaoheng had already arranged the research and development work of Yun 9.

He is working hard to perfect ultrshort laser processing technology as soon as possible...

Still in the conference room of the Aerospace Power Group.

Another lively project seminar is underway.

The reason why I say "again" is because since the project was officially approved last month, similar plots have been staged here almost every few days.

First, Chang Haonan routinely demonstrated the progress at the theoretical level, and then several leaders in charge of hardware research and development began to argue.

And the situation today... It's similar.

As usual, Chang Haonan was the first to speak:

“Last week, Academician Hou's team has used femtosecond pulse lasers to verify the ablation threshold model I proposed before.”

“Furthermore, thanks to the fact that femtosecond lasers can be used for experiments with pulse widths of smaller steps, we also noticed some conclusions that were not reached by calculation alone.”

Xi'an Institute of Optics and Mechanics developed a femtosecond (one thousandth of a picosecond) laser in the mid-1990s. However, the peak power could not meet the needs of industrial production, so it was not selected as a light source by Chang Haonan.

However, it is enough to just conduct material science research.

"According to the ablation threshold model, when laser irradiates the surface of a metal material, due to the small specific heat capacity of the electrons in the metal and the violent inverse bremsstrahlung radiation, the electrons absorb a large amount of laser energy in a very short period of time, and the electron activity increases instantly. High, and through the collision of electrons, a Fermi-Dirac distribution appears.”

"At this time, because the temperature of the free electrons is much higher than the temperature of the lattice, the temperature of the lattice gradually rises by obtaining heat through collision with hot electrons, and finally reaches a thermal equilibrium state. The specific collisions required to achieve a thermal equilibrium state The time is mainly determined by the electron-phonon collision relaxation time, but for most metallic materials, it is on the order of 10 picoseconds. "

“But now we find that below 10 picoseconds, it can be further divided into three more detailed processes.”

Theory and experiment are always complementary to each other.

Before Chang Haonan proposed the ablation threshold model, this femtosecond laser did not show particularly considerable scientific research value in the first few years of its birth.

Without this laser for testing, the improvement of the ablation threshold model will be greatly slowed down.

After a slight pause, Chang Haonan switched to a page of PPT, and then continued:

"10 femtoseconds after the high-energy laser irradiates the surface of the metal material, the electrons will be stimulated ionization, and if the irradiation time is continued to 100 femtoseconds, the electron-phonon coupling will begin to occur, but it will not appear at this time. Visible thermal effects.”

"Continue to extend it to 1 picosecond, and the electronic lattice thermal equilibrium process will begin. The thermal effect at this time has gradually begun to appear, but the number of affected molecules is far lower than the number of molecules directly converted to the plasma state, and can basically be ignored. …”

"Thanks to this discovery, I revised the ablation threshold model again and added two variable parameters related to the non-thermal melting process. The differential expression after solving through the implicit method is..."

When Chang Haonan introduced new developments, the atmosphere in the conference room was generally calm.

　In addition to Academician Hou's frequent active exchanges, there are only occasionally one or two people who raise their hands to ask questions.

First of all, these sub-picosecond level studies are more based on future needs and will not have a great impact on the current picosecond level project.

Secondly, and more importantly...

It is true that there are not many people who can fully understand it.

However, the next part is not so harmonious...

After a short tea break, the two technical teams responsible for controlling signal transmission and light source control started fighting.

Mainly because this device is so awkward.

Han Zhigao, the leader of the light source control team, first expressed his position:

“Mr. Chang, after the last meeting, we built a simple prototype for testing. So far, we have discovered at least 8 major factors that affect laser processing.”

"In addition to beam quality and pulse width, which we have thought of before, there are also luminous flux density, polarization state and defocus amount. This refers to the defocus amount itself. That is to say, even if the energy ultimately acting on the material surface is the same, different The amount of defocus will also produce different processing effects..."

The general meaning of these words is one:

The control requirements for this processing method are extremely precise. The signal transmission process must meet low latency, low noise, high bandwidth and high stability. In addition, because the equipment itself is highly complex, the electromagnetic signals radiated outwards must be controlled at extremely low levels. level.

Huo Penghua, the head of the signal transmission team, said that you are probably not dreaming. Just two low-loss conversions between optical signals and electrical signals are enough to cause a headache. How can something so good can satisfy you so much? The requirements, especially the requirement of low electromagnetic radiation, are in conflict with high bandwidth. Unless a layer of shielding layer with an outrageous thickness and weight is added, it is simply impossible to achieve.

What's even more troublesome is that in order to compensate for signal delay between the acquisition end and the control end, a technology called "real time delay line" needs to be introduced, and the compensation ability of this thing is related to the physical length, which can easily be dozens or hundreds. meters, which will have an adverse impact on transmission delay and loss...

Chang Haonan looked at Academician Hou, who said that the problems they mentioned existed objectively, and it was indeed difficult to satisfy them at the same time.

So the situation became deadlocked.

(End of this chapter)

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