China News Service, Beijing, May 10th (Ma Shuisha and Dong Jiaying) With the deafening roar, the Long March 7 Yao-5 carrier rocket spewed out of the white fog, drawing a golden curve in the sky, and successfully launched the Tianzhou. The No. 4 cargo spacecraft was sent into the predetermined orbit. This is the third time that the Long March 7 carrier rocket has sent the Tianzhou cargo spacecraft into space since the Chinese space station was built in orbit.

　　As a veritable "ice arrow", the Long March 7 carrier rocket possesses "stunts" and played a "song of ice and fire" on the banks of the South China Sea.

Rocket launching.

Photo by Tu Haichao

"Fire and Ice"

　　The temperature of the rocket can reach a maximum of 3000 degrees Celsius when the rocket is ejected. The white fog formed at the moment of launch is the evaporation of water in the diversion groove tens of meters deep at the bottom of the launch tower. The water vapor takes away a lot of heat to cool the rocket.

　　But water spray cooling is far from enough for the low-temperature rocket Long March 7.

When the rocket stands in the sun, the water on the rocket body rushes down like rain, while in the rocket cabin, it is a low temperature of minus 183 degrees Celsius.

　　This is because there is liquid oxygen in the fuel of the Long March 7 launch vehicle.

The liquid oxygen kerosene engine is known as the Mount Everest in the field of aerospace power in the world. It uses non-toxic and non-polluting liquid oxygen kerosene as fuel, which is 60% cheaper than conventional engine propellants and can be reused.

Its low temperature will also cause water vapor to condense on the surface of the Long March 7 launch vehicle.

Waterproof "Golden Bell Cover"

　　Under the strong contrast of "ice and fire", how did the Long March 7 launch vehicle develop a waterproof "golden bell cover"?

　　The Long March 7 carrier rocket's protection against "water" permeates every design detail. For example, in the conventional model, the vent used to balance the pressure inside and outside the fairing does not require separate waterproofing when launching inland, but On the Long March 7 carrier rocket, special waterproof measures have also been taken for the vent holes.

　　Lu Songtao, a rocket design expert from the General Department of the First Academy, said that in waterproof design, researchers follow the principle of "what can be solved by a single machine, not by a system, and what can be solved by a system, not by an overall solution", and solve the waterproof problem from the "source of the product".

Insulation "thick cotton coat"

　　In addition to a waterproof "golden bell cover", the surface of the low-temperature liquid oxygen tank of the Long March 7 carrier rocket also wears a thick "padded coat", which mainly plays the role of insulating heat conduction.

After wearing the "padded coat", the inside of the tank can maintain a sufficient low temperature environment, so that the liquid oxygen propellant will not volatilize a lot due to the temperature rise, and the external temperature of the tank will not be too low, so that external instruments, personnel, etc. cause frostbite.

　　The main component of "thick cotton clothes" is a plastic foam.

In the process of making cotton clothes, a foaming agent needs to be used to expand the foam. The Long March 7 carrier rocket uses a new type of fluorine-free foaming agent, which will not cause harm to the earth's ozone layer.

　　Compared with the past, a layer of metal aluminum foil has been removed from the "padded coat" worn by the liquid oxygen storage tank of the Long March 7 launch vehicle, and the automatic production of automatic spray foam and surface machining has been realized.

These improvements not only greatly improve the production efficiency of the "padded coat" in the low-temperature liquid oxygen tank, but also make the "padded coat" greener and lighter in texture.

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