The military-industrial scientific research system of the academic master.

Chang Haonan's trip back to Beijing this time was just a side trip to participate in the membrane rupture test of the Institute of Mechanics. The main reason was to prepare for the warhead test of the hypersonic verification missile.

With the help of two cold wind tunnels, JF8A and JF10, the research and development of the basic double-cone configuration by the Aviation Power Group and the First Academy of Aerospace Science and Technology was relatively smooth.

Although the lift coefficient and internal space have not yet been optimized to the theoretical limit, they are sufficient for the current stage.

Especially in terms of structural strength and shape drag reduction——

The reason why the double-cone rocket plan of the First Academy of Aerospace Science and Technology could not be continued was mainly because the mechanical calculations were not done well, which led to the failure of the first test.

Once bitten, twice shy.

Now that they have another chance, they naturally have to be extra careful where they fell into the trap last time.

However, the cone shape in a broad sense has a pair of contradictions that are difficult to resolve in principle.

The smaller the curvature of the nose cone, the more beneficial it is to reduce wave resistance.

The greater the curvature of the nose cone, the more beneficial it is to reduce aerodynamic heating.

Since the double-cone warhead chooses to reduce drag in the mechanical and thermal balance, the requirements for nose cone cooling are correspondingly increased.

After the work meeting at the beginning of the year, Chang Haonan assigned the task of researching a new sweat-inducing material to Li Yabo, who had already stayed at the school to teach, based on the molecular mechanics calculation results provided by the system.

Now that two months have passed, it is time to test the results.

……

The day after inspecting the Institute of Mechanics, Chang Haonan brought Li Yabo to the Institute of Launch Vehicle Technology.

Xing Muchun, who was in a meeting, immediately stopped the meeting and took the two to his laboratory.

"Academician Chang, during this period, we have conducted several rounds of different types of sweat cooling experiments on the scaled model of the cone head according to your request."

As he started to introduce himself, he took out his glasses from his pocket and put them on, then sat down next to the computer in the laboratory:

"From the laboratory results alone, after the forced sweat cooling system used on the rocket engine nozzle was moved to the warhead as it is, whether it is cooling efficiency, working time, structural strength, or the difficulty of integrated production with the bearing layer, it basically meets the requirements of our warhead system."

As they were talking, a light suddenly lit up in an inconspicuous transparent glass cover nearby, attracting the attention of Chang Haonan and Li Yabo.

Inside the cover, there was a double-cone shell mounted on a bracket, but the shell, especially the surface of the first cone section, was almost completely covered by a layer of white whisker-like solid.

It is crystal clear under the air flow and light, and looks very beautiful.

"Look, this is the arc heating and sweating cooling experiment we are conducting... Because we knew you were coming, we didn't turn off the equipment immediately after the results came out."

Xing Muchun turned around and explained to the two people behind him:

"For safety reasons, our indoor test uses water as a coolant. When the water evaporates on the surface, the wall temperature is reduced to the freezing point. Therefore, the water will freeze on the surface, then melt when heated, sweat, cool, and freeze again. This process will be repeated, and finally this layer of ice whiskers will be formed. However, this situation is impossible in actual use."

In fact, Chang Haonan certainly knew these details, so it would be better to say that he was explaining to Li Yabo who came here for the first time.

The latter was also somewhat puzzled at this moment——

According to the other party, this cooling technology seemed to be quite perfect and did not leave any use for the new material he had developed.

"Let's not talk about the engineering application level."

Chang Haonan just waved his hand:

"The sweat cooling technology itself should be feasible, right?"

"Of course."

Xing Muchun nodded:

"According to calculations, the entire system can achieve a heat dissipation efficiency of about 6.5*10^8 W/m^2 on the warhead surface. Although it is only about half of that on the nozzle surface, it is sufficient for our aerodynamic heating... or even faster, to more than 10 times the speed of sound."

Although he said so, there was not much joy on his face.

At this time, Li Yabo, who had been bending over and staring at the ice whiskers on the outer shell of the double cone, stood up and asked Xing Muchun:

"Director Xing, I see that the ice layer on the surface of the shell is still growing slowly. I think the consumption of coolant will not be too small. I wonder where the coolant is stored..."

“This is the problem we face now…”

Xing Muchun smiled bitterly and pointed to the fixing rod behind the shell:

"The test shell is a scaled model, so the coolant is injected from the outside through a hollow pipe. But we have calculated that if the sweat cooling system is to maintain operation for 150 seconds, the coolant cavity will almost fill the entire double cone... By then, let alone the warhead and the seeker, there will be no place to put even the terminal acceleration engine of the Sixth Institute..." At this moment, Li Yabo's mind flashed with lightning, and he immediately understood, and cast his eyes on Chang Haonan next to him:

"Teacher, so our spontaneous sweating material is designed to solve this problem?"

"Spontaneous sweating material..."

When Xing Muchun heard this question, he was stunned at first, and then he showed a complicated expression.

It seems that there is a hint of expectation mixed in with the trouble:

"Although Academician Chang did not mention it before, we have actually tested a surface process that uses sintered porous tungsten as the skeleton and then infiltrates copper into the micropores. In this way, the copper with a lower melting point will melt in advance, achieving evaporation and heat absorption."

"However, tungsten and copper are two immiscible materials, so a powder metallurgy process that is not yet mature is needed to achieve a good infiltration effect. Moreover, if the amount of copper infiltration is too small, the cooling effect will not be obvious enough. On the contrary, if it is too large, the thermal shock resistance of the overall structure will be reduced. It is difficult to find a specific balance..."

Looking at Xing Muchun who was retrieving experimental data from the computer, Chang Haonan's eyes showed a hint of surprise.

He did underestimate the other party's initiative and work efficiency.

"Don't worry, Old Xing."

As he spoke, Chang Haonan gestured behind him.

Soon, Li Yabo took out a sample box about ten centimeters square and placed it carefully in front of Xing Muchun.

"This is……"

The latter took a puzzled look and found a pile of black-gray powder inside, which he couldn't identify.

"To be honest, I didn't expect you to move so quickly. Otherwise, I should have told you the specific tasks for the second phase earlier..."

Chang Haonan gently patted the lid of the sample box:

"The new self-sweating cooling material we developed uses titanium diboride (TiB2) as a ceramic skeleton, and then infiltrates metal nickel and silver to prepare the TiB2-(Ag, Ni) composite material through high-temperature pre-sintering and pressureless infiltration process."

"nickel?"

Xing Muchun was a little slow to react.

The melting point of nickel is as high as 1500℃, and its boiling point is above 2700℃, which is almost the same as the melting point of the titanium diboride matrix itself. It has no value as a diaphoretic at all.

Chang Haonan had expected this and explained with a smile:

"In addition to allowing the silver itself to melt and dissipate heat, this composite material can also absorb and store a large amount of traditional perspiration agents. When the temperature is high enough, it will seep out through the surface, further saving the internal space of the double-cone warhead. According to the results calculated by the molecular mechanics method, the cooling efficiency can reach about 3.75*10^8 W/m^2..."

Hearing this, Xing Muchun's eyes widened slightly, and he looked at the half box of unremarkable powdered solid in front of him with some disbelief.

If what Chang Haonan said is true, then all the engineering problems currently faced by sweat cooling will be solved.

After all, for the aerodynamic heat of the warhead, the efficiency of sweat cooling itself is seriously excessive.

It’s just that the duration and system complexity are difficult to meet the requirements.

"Academician Chang, this is titanium diboride and silver, the cost is probably..."

He said this, but his hands did not slow down at all, and he had already held the sample box firmly in his arms.

As if he was afraid that Li Yabo would snatch it back again.

In fact, compared with the material itself, it is the extremely complex preparation process that is more expensive.

"The cost... is indeed a bit high."

Chang Haonan said with some regret:

"But there's nothing we can do. When it comes to hypersonic research, sometimes we can't just save money blindly..."

"Besides, the matrix of this material is very strong and will not peel off like ablative cooling. So it can be used in more than just this place. For example, it can be used in the gas rudders of missiles and the surfaces of inter-space vehicles. It has potential applications. Just think of it as an investment in the future..."

Xing Muchun was obviously just being polite as usual.

Before Chang Haonan could finish his words, he grabbed the telephone receiver on the table and called a few technicians in blue lab coats:

"You, use this material and follow Academician Chang's instructions to conduct another sweat cooling test!"