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Space environment

Environment in space

Space environment, the environment in space, in space, various celestial bodies also radiate outward electromagnetic wave , many celestial bodies It also radiates outward High-energy particle , forming cosmic rays 。

Chinese name: Space environment
troposphere: (sea level to 10km

stratosphere: (10~40 km)
Middle layer: (40-80 km)

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brief introduction

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Since the Big Bang universe With the expansion of, the temperature keeps decreasing. Now, space has become a cold environment, with an average temperature of minus 270.3 ℃.

In space, various celestial bodies also radiate outward electromagnetic wave Many celestial bodies also radiate outward High-energy particle , forming cosmic rays 。 As the sun has Solar electromagnetic radiation ， Solar cosmic ray Radiation and solar wind, solar cosmic ray radiation is the high-energy particles emitted by the sun when a flare burst occurs, while the solar wind is Corona High energy plasma flow blown out.

There are many celestial bodies magnetic field , magnetic field captures the above high-energy charged particles, forming strong radiation radiation zone For example, in the sky above the earth, there are two radiation belts inside and outside. It can be seen that space is still a strong radiation environment.

Space is still one high vacuum ， microgravity Environmental Science. Gravity is only one percent to one hundred thousandth of a gram (g- Gravitational acceleration ) The gravity that people feel on the ground is 1g.

Delimitation

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physical scientist Divide the atmosphere into five layers

Thermogenic layer ( the ionosphere 80~370km) and the outer atmosphere (ionosphere, 370km above).

Space environment

About 3/4 of the atmosphere above the earth is troposphere Inside, 97% is below the stratosphere, and the outer edge of the stratosphere is aircraft The highest limit of flight supported by air.

Some high-altitude rockets can enter the middle layer. The lowest orbit of the artificial satellite is in the thermosphere Air density 1% of the earth's surface.

The air continues to exist at 16000 km altitude, and even at 100000 km altitude, there are still air particles. From a strictly scientific point of view, Air space and outer space There are no clear boundaries, but they are gradually integrated.

United Nations Committee on the Peaceful Uses of Outer Space The Scientific and Technical Subcommittee noted that it was currently impossible to propose precise and lasting scientific criteria to delimit outer space and airspace. In recent years, it has tended to take the lowest altitude (100~110 km) of artificial satellite from the ground as the lowest limit of outer space.

Environmental characteristics

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According to the first paragraph: "Since Big Bang Later, with the expansion of the universe, the temperature continued to decrease. " Although there are stars radiating heat, the number of stars is limited, and their life is also limited, so the overall temperature of the universe is gradually declining. After more than 10 billion years, space has become a cold environment. yes Cosmic microwave background Research on radiation (radiation left in space during the Big Bang) has proved that the average temperature of space is minus 270.3 ℃.

In space, not only the radiation left by the Big Bang, but also various celestial bodies radiate electromagnetic waves, and many celestial bodies also radiate outward High-energy particle , forming the universe radial 。 For example, Galaxy yes Galactic cosmic ray Radiation, the sun has solar electromagnetic radiation Solar cosmic ray Radiation (high-energy particles emitted outward when the solar flare bursts) and solar wind (from the sun Corona High energy plasma flow blown out). Many celestial bodies have magnetic fields, which capture these high-energy charged particles and form highly radioactive radiation zone For example, in the sky above the earth, there are two radiation belts inside and outside. It can be seen that space is still a strong radiation environment. After the Big Bang, hydrogen and helium were formed in the universe, of which hydrogen accounted for 3/4 and helium for 1/4. Later, most of them gradually agglomerate into clusters, forming galaxies and stars. Successive generation of hydrogen and helium in the center of stars nuclear fusion , forming heavy elements such as oxygen, nitrogen and carbon. When the star dies, most of the remaining hydrogen and helium as well as oxygen, nitrogen, carbon and other elements are scattered in space. The main one is still hydrogen, but it is very thin, with only 0.1 hydrogen atoms per cubic centimeter, a little more in the interstellar molecular region, about 10000 per cubic centimeter.

In addition to ultra-low temperature, strong radiation and high vacuum Besides, there are high-speed dust Micrometeoroid And mobile stars. It has great kinetic energy. A milligram of micrometeoroid can penetrate a 3mm thick aluminum plate.

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Comparison between celestial environment and space environment

With the development of space industry Artificial earth satellite There are more and more spacecrafts Upper level Rocket. Some of them were destroyed by remote control, and some of them broke into pieces by themselves. These debris will continue to fly around the earth for a certain period of time, forming new environmental characteristics in space, namely“ space trash ”。 Space debris also runs at a high speed, posing a collision threat to spacecraft in use. The environment on all celestial bodies outside the earth is not the same as that in space. As far as the solar system is concerned, the environment on the planets and satellites is also very different. Some of them have no atmosphere (such as Mercury 、 Moon ）, (some have thin atmosphere such as Mars), some have dense atmosphere (such as Venus Jupiter ）The composition of the atmosphere is also different. For example, the atmosphere of Venus is mainly carbon dioxide Jupiter's atmosphere is mainly hydrogen. Some have magnetic fields, some have solid surfaces (such as Mercury, Venus, Mars, the moon), and some have no solid surfaces (such as Jupiter, Uranus Neptune ）Some of them have very high surface temperature (e.g. Venus reaches 470 ℃), some have very low surface temperature (e.g. Pluto reaches - 253 ℃), and comets are completely composed of dust and ice, and so on. Specific analysis of specific celestial bodies is needed.

Unique environment of spacecraft

In addition to the above natural environment, the spacecraft flying in space also has a unique induced environment, that is, the environment generated by the operation of some spacecraft systems under the action of the space environment. It mainly includes the following types.

Extreme temperature environment. The spacecraft flew in the vacuum of space, because there was no air conduct heat And heat dissipation. The side directly exposed to the sun can produce high temperature of more than 100 ℃. On the shady side, the temperature can be as low as - 100 ℃~- 200 ℃.

High temperature, strong vibration and overweight environment. When a spacecraft takes off and returns, Carrier rocket And reverse rocket ignition and flameout, will produce severe vibration. When the spacecraft reenters the atmosphere, it travels through the dense atmosphere at a high speed and rubs violently with air molecules, making the surface temperature of the spacecraft as high as about 1000 ℃. When a spacecraft accelerates to rise and decelerates to return, positive and negative acceleration will cause all objects on the spacecraft to be extremely overweight. overweight In the gravity of the earth Average acceleration (Its symbol is "g", and g is about 9.8 meters/square second). Manned spacecraft The maximum overweight is 8g when ascending and 10g when returning, and the overweight is greater when the satellite returns.

weightlessness and microgravity Environmental Science. When a spacecraft is in inertial motion in space orbit, the gravity of the earth or other celestial bodies is just offset by its centrifugal force centroid The gravity at is zero, that is Zero gravity , where Weightlessness environment 。 The environment on the spacecraft outside the center of mass is the microgravity environment, where the gravity is very low.

The weightlessness and microgravity environments are the most valuable unique environments on spacecraft. In weightlessness and microgravity environment Convection phenomenon Disappear, buoyancy Disappear, component separation and floating caused by different densities disappear, the hydrostatic pressure of fluid disappears, and the liquid surface tension Restraint, wetting and Capillarity Aggravation, etc. In short, it has caused a series of unpredictable changes in physical properties of matter, providing an extreme physical condition. Using these rare environmental conditions on the ground, many scientific experiments that are difficult to carry out on the ground can be carried out to produce special materials, expensive drugs and industrial products that are difficult to produce on the ground.

During the flight of Shenzhou VII

During the Shenzhou VII flight, the space environment was generally good

Chinese Academy of Sciences After more than five months of accurate calculation and analysis, the Space Environment Research and Forecast Center believes that Shenzhou VII Manned spaceflight During the flight, the space environment was generally good.

The analysis and forecast of space environment show that in recent two to three years solar activity In the low years, the sun has no large energy release and explosion, and the earth space is relatively quiet, which is suitable for carrying out manned space activities.

For the Shenzhou VII manned spacecraft A good space environment is very critical. If you encounter High-energy particle Radiation, low magnetic field and other disastrous space environmental events will threaten the life safety of astronauts.

Director of the Space Environment Research and Forecast Center of the Chinese Academy of Sciences for Shenqi Flight Gongjian Village The introduction said that the space environment is affected by many factors, among which the most important natural factors are solar activity 。 Every 11 years, the sun will change from a state of frequent activity to a relatively calm state. During the period of frequent solar activity, space environmental disasters will suddenly occur.

The Space Environment Research and Forecast Center of the Chinese Academy of Sciences started to conduct comprehensive analysis and forecast of the space environment five months in advance, and recommended and suggested the task period within the scope of project selection.

If severe space environment does occur, the Forecast Center will suggest shortening or changing the mission time, or even canceling the mission.

At the end of April 2008, the Forecast Center made the first forecast. Since then, they have continuously revised the forecast. When the spacecraft is about to launch, the forecast frequency has increased to once a day.

Gongjian Village He said, "From Shenyi to Shenzhou VI, we always do this every time. Because the closer to the mission time, the more accurate the forecast results will be, so we must constantly revise the forecast results."

Gong Jiancun also introduced that now solar activity In low years, the solar activity will rise to Senior years 。 This means the future Manned spaceflight Many of the tasks will face worse environment, and then the space environment guarantee task will become more arduous.

harm

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A new Australian study found that human stem cells are simulating microgravity The development performance under environment is quite different from that under normal conditions. This discovery may have great significance for space migration and long-term space flight. Australian researchers use NASA The developed rotating container simulates the microgravity environment and finds that the expression of human stem cell protein is very different from that under the gravity of the earth. About 64% of the proteins in microgravity cells did not appear in the control model group. The proteins involved in bone damage and calcium control contained in microgravity cells do not exist in ordinary gravity cells. embryonic stem cell It can differentiate into any of hundreds of cell types in the body. Elizabeth Blaber, 21, was a participant in the study. Last month, they Houston Held Astrobiology A paper was published at the meeting.

Space travel will damage people's bodies. Astronauts the outer space Will show Muscular atrophy 、 osteoporosis And slow heart rate. Sydney University of New South Wales The research team led by Brendan Burns said that researchers have carried out a lot of research work in this field, but little work has been done at the cellular level.

research meaning

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And found that stem cells microgravity The expression of different proteins under the action can help explain the changes of adult muscles and bones. The study also found that antioxidant The level will decrease with time, which can explain why the wound healing is very slow in space.

last month Space Shuttle Discovery The mouse stem cell experiment carried in the air has returned from international space. When researchers carefully review the experimental results, more information on space stem cell research will be released. In this space experiment, mouse stem cells were placed in a small reaction container and provided conditions for them to differentiate. On Earth, mouse stem cells are models for studying stem cell differentiation and development. NASA researchers are still analyzing the results.

Although there are no embryonic stem cells in adults, this kind of research is very important to understand the impact of living in space on health, and may be of significance to human reproduction in space in the future.

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