When the earth is not affected by gravity, that is, when all objects are not on the earth. Our life and work are carried out in an environment of gravity. However, in space navigation, whether the space shuttle, satellite, spacecraft or astronauts themselves are in a state of weightlessness, or only subject to small gravity and other external forces.
Many novel phenomena will appear under the condition of microgravity. For example, candles burn continuously on earth. This is because during combustion, the air around the flame expands and rises upward, and the surrounding cold air flow comes to supplement, so as to continuously bring oxygen and continue the combustion. Air can produce convection, but also because of gravity. In the environment of microgravity, convection basically does not exist. Soon after the candle began to burn, it consumed the oxygen in the surrounding air. Because there was no oxygen supplement, the candle would soon go out.
The sand will be put into the water on the earth. It won't take long. Under the action of gravity, the sand will sink to the bottom of the container. In the microgravity environment, the sand will not sink (in fact, it doesn't matter up or down in the weightless environment). Space vehicles not only provide microgravity conditions, but also provide a dust-free, sterile and ultra clean environment. This provides conditions for the development of a new space material science. Some developed countries have started the experiment of microgravity material processing and are ready for commercial production.
At present, microgravity material processing is mainly used in the following aspects:
1、 Metal materials.
Due to the disappearance of stratification and precipitation in microgravity, it is possible to manufacture homogeneous mixed alloys which are difficult to make on the earth in space, and can also produce low specific gravity foam metal with fine porosity and uniform distribution. These alloys have special physical properties, and some of them can be used to prepare new superconducting materials.
2、 Semiconductor materials.
Under the favorable conditions of microgravity, semiconductor materials with uniform composition, complete structure and excellent performance can be manufactured, which will greatly promote the development of microelectronic industry.
3、 Optical glass and other composite materials.
Using the characteristics that various substances with different specific gravity can be mixed evenly under microgravity conditions, glass doped with various metal oxides can be manufactured, and the mixture of metal and ceramics can also be manufactured. Some of these new materials have special optical, electrical and magnetic properties, and some have high hardness, high wear resistance and corrosion resistance. These materials play an irreplaceable role in modern science and technology.
4、 Pharmaceutical processing and polymer materials. Using the high-definition cleanliness environment of space and the characteristics of processing without containers, we can realize extremely high purification technology, and can also prepare various polymer materials, active materials and various drugs that are difficult to be prepared on earth.
Experts predict that an industry for processing microgravity materials in space is rising. It not only provides new materials that can not be seen in nature, but also plays a powerful role in promoting the development of natural science and various applied technologies.