If Wu Hao and the others want to develop the retrievable technology of the second-level rocket, they must first solve a problem, so that the second-level rocket does not burn in the atmosphere.

If this problem is solved, it is actually very simple, that is, to cover the rocket body of the secondary rocket with insulation material, or to design and manufacture the rocket body to resist high temperature burning.

At present, there are two technologies or two ideas for this kind of returnable spacecraft in this field. One is the idea of ​​the Mi Space Shuttle, which is to cover the surface of the spacecraft with insulating materials. In this way, the contact between the spacecraft and the atmosphere can be reduced, thereby preventing the spacecraft from being burned when returning.

The second method is to directly use high temperature resistant materials to make the spacecraft shell, and then let the shell directly contact the atmosphere and burn. This technology is mainly used in Soviet spacecraft and our spacecraft. At present, most of the new generation of spacecraft return cabins in various countries also use this technology.

But for Wu Hao and others, no matter what kind of technology, the first big impact or what they want to solve is the weight problem.

Regardless of whether it is a heat-resistant shell or an insulation tile, the first thing to solve is the weight problem.

If the weight is too heavy and takes up too much rocket thrust, it is not worthwhile. But if these two technologies are not used, then the rocket may be burnt.

So is there a third way to make the secondary rocket drop from space without being burned by the atmosphere?

Yes, speed is the key.

The primary cause of the spacecraft being burned by the atmosphere is the speed. If the speed is fast enough, then the friction of the spacecraft in the dense atmosphere will be greater, and the friction will generate heat, so the rocket will naturally be burned.

Therefore, if the return and landing speed of the secondary rocket can be controlled, the temperature on the surface of the rocket body can be greatly reduced, so that the rocket can return to the atmosphere safely.

There are several ways to reduce the speed of the rocket. The first one is the parachute that everyone can think of first. Use a parachute to slow down.

When the rocket reaches the edge of the atmosphere, it starts to throw a parachute, using the air resistance of the parachute to slow the rocket.

Can this situation be achieved? Yes, but first the parachute must also have strong heat resistance, otherwise the parachute may be burnt down after a long time of landing.

In addition, opening the umbrella at the edge of the atmosphere is still very difficult and difficult to implement.

In addition, the parachute was opened too early, and the landing location was uncontrollable, so it was meaningless to reclaim.

The second method is to use rocket engine reverse thrust technology to slow down the landing like a Falcon rocket.

This technology is feasible and feasible, but this means that the rocket has to carry more fuel, and too much fuel will also squeeze the rocket's carrying capacity, thus losing the value of recovery.

The third technique is gliding and landing, similar to the space shuttle, which uses a gliding method to slow down and gradually land, thereby reducing the rocket's descent speed.

The fourth method is to land in a water-floating manner similar to Chang'e-5, but this has certain requirements for the strength of the spacecraft itself. Obviously, the rocket body is not suitable.

So Wu Hao and the others set their sights on the third technique, using gliding techniques to slow the rocket.

But this alone is far from enough. It is necessary to attach a layer of insulation material to the rocket, commonly known as insulation tiles.

Although this thing is not new, and because of this insulation tile, several space shuttles have suffered major accidents.

But the rocket body and the space shuttle can be different, and the rocket is unmanned load most of the time, so safety is also guaranteed.

In addition, the current technology is not the same as it was decades ago. The project R&D team chose a special thin and light insulation material this time.

This material is very light and thin, about the same weight as ordinary foam, or even lighter. It can be expected that it has very good heat insulation performance, even if it is burned on a fire, the temperature of the general fire will not match it.

And when it encounters high temperature, this kind of insulation material has another characteristic. It can gradually dissolve slowly from the surface, and after dissolution, it will also emit a lot of heat. It is a very ideal insulation material.

Moreover, this material is usually stored in a liquid state, and when needed, it is sprayed onto the relevant objects with a spray gun.

In this way, the cost of use is also reduced a lot, and only need to re-spray the insulation material each time.

This kind of material is also the latest scientific research result successfully developed by Wu Hao and his related project research team of the Materials Research Institute under Wu Hao's "instruction".

At present, this technological achievement is still strictly confidential, but relevant material samples and part of the data have also been sent to the military's materials laboratory for testing.

Judging from the preliminary test results obtained, UU Reading www.uukanshu.com is still very amazing, which also makes many departments and institutions coveted, and they have to seek cooperation with Wu Hao.

But, the initiative is in the hands of Wu Hao and the others, so he is naturally not in a hurry. After the relevant test results were all released, he was sharpening his knife and waiting for the arrival of these institutions and departments. He was so "warmly entertained."

This time, Wu Hao and the others sprayed this new type of heat-insulating material on the second-stage rocket body of the Jianmu-2 modified rocket to be launched.

In addition, the entire second-stage rocket has also undergone changes. On the second-stage rocket body, a folding flying wing similar to that of a cruise missile has been added.

When launching, this flying wing is folded up and does not affect normal launch. When it landed, the wings would bounce off and then drive the entire body to glide.

Even though this is just a folding flying wing, the technology used on it is also very complicated.

For example, it must first be light enough, because the weight it occupies is the payload of the rocket.

Secondly, it must be strong enough so that it can withstand the huge strength of the arrow itself.

Finally, it must be reliable enough, it must be able to open normally when landing, and it must be reusable, so the difficulty will naturally increase.

Of course, for Wu Hao and the others, they challenged it precisely because of the difficulty.

After calculating the model data of the "their own way" super photon computer and their consecutive tests, after the project R&D team felt that this technical solution was feasible and reliable, Wu Haocai approved to use it for testing on this important launch mission .

It stands to reason that this is very risky, but seeing the confident gaze of the project development team, Wu Hao finally approved it, and he was very confident in his "own technology".