Over the past six months, two major space disasters have occurred in succession. Although people are sorry, these setbacks can't stop mankind from marching into the universe. Since space activities are so risky, why don't humans give up their dream of marching into the universe? In the long run, the earth's resources are limited, and mankind will one day walk out of the cradle; In the short and medium term, space activities can bring huge returns and reflect a country's comprehensive national strength. Marching into the universe is a great cause of mankind now and in the future. Therefore, manned space flight has become the top priority of the development of modern space science and technology. ...
The Development of Manned Space Technology in China and Its Significance and Prospect
As the saying goes, the sky is high for birds to fly and the sea is wide for fish to jump. Mankind has continuously expanded its living space in the long social progress. Now, the range of human activities has experienced a gradual development process from land to sea, from sea to atmospheric space, and then from atmospheric space to space. Every expansion of human activities is a huge leap.
The Development Course of Manned Space Technology in China
A long time ago, human beings had the desire to fly out of the earth, explore the mysteries of space and develop the resources of the universe, and many fairy tales in ancient China were outstanding reflections. The most typical one is the widely circulated goddess the Goddess Chang'e flying to the moon. It describes a beautiful woman named Chang 'e who stole the elixir of life that her husband Hou Yi got from the Queen Mother of the West, and then lightened it and floated to the moon.
The first person in history who tried to fly into the sky by rocket was an official of China in the15th century. 1945, American scholar Kim described it in his book Rockets and Jet Engines: Ten thousand families first made two big kites and placed them on both sides of a chair. Then, he tied 47 of the biggest rockets that could be bought at that time under the chair. After the preparations were completed, thousands of families sat in chairs and ordered their servants to light the rockets. However, with a loud noise, he disappeared into flames and smoke, and the first attempt of human rocket flight was unsuccessful.
In the 1980s, the reform and opening up brought the spring of space technology. From 65438 to 0986, the Central Committee of China and the State Council approved the outline of the high-tech research and development plan (referred to as the "863 Plan"), which listed space technology as one of the key points of high-tech research and development in China. Experts in the field of "863" high-tech space conducted in-depth and detailed argumentation on the future development of China's space technology, and described the blueprint for the development prospect of China's space technology. They agreed that manned space flight is the logical next development goal of China after the artificial satellite project. 1992 65438+ 10, the Central Committee of the Communist Party of China approved the manned spacecraft development project. Since then, China's manned spaceflight project has been officially launched. 1 999165438+1On October 20th, China successfully launched its first spaceship Shenzhou1,becoming the third country in the world to launch a spaceship. Since then, Shenzhou II, Shenzhou III and Shenzhou IV have been sent to the ninth heaven respectively. Before 1992 began to develop manned spacecraft, experts in the field of "863" high-tech space flight in China had studied for several years and worked out what kind of transporter to develop, that is, all kinds of technical schemes for directly developing space shuttle beyond manned spacecraft were fully demonstrated, compared and analyzed, and even had a heated debate.
In 2003, 10, 15 yen realized the dream of thousands of families, because on this day, the first manned spaceship, Shenzhou 5, which the people of China had been waiting for for for a long time, was successfully launched and returned safely, realizing the dream of China flying in the Millennium. It also broke the monopoly pattern of the United States, the Soviet Union and Russia in this field for many years, and became the third country in the world to independently develop and launch manned spacecraft, which played a great role in promoting the development of the world's manned space industry and revitalizing the China Association for Science and Technology.
The great significance of manned space flight
Historically, the rise of ocean navigation technology has led to the development of world trade, the opening of world market and a series of achievements of modern science, which has opened an era of "global civilization". The advent of contemporary manned space technology has brought mankind out of the cradle of the earth and into space, opening a new era of "space civilization".
Manned space flight is the product of the development of space technology to a higher stage. However, there are great differences between manned space technology and unmanned space technology, which are mainly reflected in three aspects: safety, complexity and high cost. Therefore, since 196 1 the first astronaut went to heaven, it has not shown particularly obvious use. However, in the foreseeable future, several problems that need to be solved urgently, such as resource depletion and population explosion, can only be solved by opening up the world and expanding the living space of mankind. Even in contemporary times, the development of manned space flight can also play the following roles:
First of all, it can reflect a country's comprehensive national strength and enhance its international prestige. Because the level and achievement of space technology is a comprehensive reflection of a country's economic and technological strength. Manned space flight is the development of space technology to a higher stage and a breakthrough in manned space flight-sending astronauts into space and returning safely with domestic manned spacecraft is also a symbol of a country's comprehensive national strength. The development of manned space flight needs to rely on advanced technical level, developed industrial base and strong economic strength. So far, only Russia and the United States have achieved manned space flight. Other countries with a certain space technology foundation or strong economic strength want to get their hands on manned space flight, but they are unable to do so, so they can only turn to cooperate with them and invest Russian and American manned spacecraft to send their astronauts into space, so as to gradually join the world's "manned space club." Comrade Deng Xiaoping once said: Without two bombs and one satellite, there would be no great power status of China. Therefore, China astronauts' entry into space can attract the world's attention, enhance China's international status, invigorate the national spirit and enhance the cohesion of the whole people, just as China had "two bombs and one satellite" in the 1960s and 1970s.
Secondly, it can reflect the achievements of modern science and technology in many fields, and at the same time put forward new development needs for all fields of modern science and technology, which can greatly promote the development of the whole science and technology and contribute to the cultivation and cultivation of aerospace science and technology talents. For example, as far as the development and operation of manned spacecraft are concerned, high requirements are put forward for technologies such as communication, remote sensing, propulsion, measurement, materials, computer, system engineering, automatic control, environmental control and life support, which greatly promotes the progress of these technologies.
Moreover, the development of manned space flight can promote the development of space resources and benefit mankind on earth. The high altitude position and microgravity of manned spacecraft can provide an ideal experimental site for scientific research. It plays an important role in promoting life science and biotechnology, microgravity science and application, and is expected to make breakthrough progress in some frontier disciplines and bring great benefits to mankind. Some countries have made remarkable achievements in aerospace pharmacy, aerospace breeding, aerospace material processing and other fields, and are ready to establish aerospace factories, with unlimited efficiency and benefits.
In addition, the population that the earth can accommodate is limited, about 8 billion ~ 1 1 100 million, so some people began to study the plan of emigrating to outer space; The energy on the earth is becoming more and more tense, so can we explore mineral deposits on other planets? This is a problem that scientists are concerned about, and it is not a fantasy, because many once unattainable myths and fantasies like manned landing on the moon have now become reality.
Finally, manned space flight has great military potential. Using manned spacecraft can accomplish reconnaissance and surveillance tasks well; Flexible deployment, maintenance and assembly of large military satellites; Safe and continuous command and control of military forces on the ground; It can also be used as a testing ground for special weapons. For example, as early as 1 965,65438+February, the astronauts on the Gemini 7 spacecraft in the United States used infrared remote sensors to monitor and track the launch of1submarine-launched missiles, and the information obtained was faster than that reported by the observers on the submarine. During 1 and the Second Gulf War, astronauts on the Mir space station and the International Space Station carried out a lot of observation activities in the war zone and obtained a lot of useful information.
The future prospect of manned space flight in China.
China's manned space flight will implement a "three-step" development strategy. On the basis of successfully launching four unmanned test spacecraft, China sent astronauts into space for the first time, achieving a historic breakthrough in manned space flight. However, this is only the first step. In the second step, in addition to continuing to carry out earth observation and manned spacecraft space experiments, we will focus on extravehicular activities, space rendezvous and docking tests, and launch long-term autonomous flight and short-term manned space laboratories, so as to build a complete space engineering system as soon as possible and solve space application problems of a certain scale. The third step is to build a larger space station with long-term care.
Space technology has created a series of advanced and complicated construction procedures for the smooth progress of space activities. It involves the allocation of human resources, the collocation and installation of equipment and instruments, and other difficult academic tasks. It is the lofty pursuit of the development of the country, the nation and even all mankind.
Avionics technology (aerospace electronics)
[Edit this paragraph] Overview
Electronics and electromagnetic wave theory and technology applied to aviation engineering and aerospace engineering. Electronic system is one of the important systems in modern aerospace engineering.
[Edit this paragraph] Composition
It is divided into communication, navigation, radar, target recognition, telemetry, remote control, remote sensing, fire control, guidance, electronic countermeasures and other systems. Generally, various systems include electronic systems on airplanes and corresponding ground electronic systems, which are combined into a system by transmitting signals through electromagnetic waves. Electronic theories and technologies related to these electronic systems include communication theory, electromagnetic field theory, radio wave propagation, antenna, detection theory and technology, coding theory and technology, signal processing technology and so on. Microelectronics and computer technology are the basis to improve the performance of various electronic systems. Their development has further miniaturized the electronic system on the aircraft, and has the ability to process more data in real time, thus greatly improving the performance of the aircraft (maneuverability, fire control capability, all-weather flight, automatic landing, etc.). ) and expand the functions of spacecraft (scientific exploration, resource investigation, communication and broadcasting, reconnaissance and early warning, etc. ).
[Edit this paragraph] function
First of all, the characteristics of electronic equipment on aerospace vehicles are:
① Small size, light weight and low power consumption are required; ② Able to work in harsh environmental conditions; ③ High efficiency, high reliability and long service life. These requirements are especially strict in high-performance aircraft and spacecraft. There are strict restrictions on the cabin volume, load and power supply of aircraft and spacecraft. Every time the weight of the equipment on the satellite increases by 1 kg, the launching weight of the launch vehicle will increase by several hundred kg or more. Missiles and spacecraft are subjected to severe impact overload, strong vibration and particle radiation. Some spacecraft work for a long time, such as the geostationary orbit communication satellite for 7 ~ 10 years, while the deep space probe works for a longer time. Therefore, electronic components used in aerospace must undergo very strict quality control and screening, and the design of electronic systems needs to make full use of reliability theory and redundancy technology.
Second, the main development direction of aerospace electronic technology is:
① Make full use of computers and large-scale integrated circuits to improve the integration, automation and intelligence of aerospace electronic systems; ② Improve the real-time signal processing and data processing capabilities and data transmission speed; (3) Developing high-speed and ultra-high-speed large-scale integrated circuits; (4) Developing electronic technology in higher frequency bands (millimeter wave, infrared ray and optical frequency); ⑤ Develop various electronic components with higher reliability and longer service life.
Basic knowledge of aerospace
As we know, the home of mankind is the earth, and the outside of the earth is covered with an atmosphere. Without water and atmosphere, without suitable temperature and environment, it is difficult for living things to survive.
Usually in people's eyes, "the sky" is very high, and it is very, very difficult to rush out of the thick atmosphere into space. In fact, compared with the earth, the atmosphere is very thin.
It is known that the diameter of the earth is about 12700 km, while the thickness of the atmosphere is only 100 -800 km. If the earth is compared to an apple, then we can regard the atmosphere as an apple skin, but this "apple skin" itself is changeable.
For example, the layer closest to the earth's surface is called the troposphere. Its height ranges from sea level to about 1 1000 meters, and its top boundary varies with latitude and season, with 17000 meters in equatorial regions and1000 meters in mid-latitude regions (such as Beijing and Tianjin).
The main feature of the troposphere is that the temperature decreases with the increase of height, so it is also called thermocline. On average, the temperature drops by about 6.5℃ for every1000m elevation. At the same time, the air pressure also decreases with the increase of height. Because of the gravity of the earth, the height of 5500 meters contains half of the total atmosphere, and the whole troposphere accounts for about three quarters of the total mass of the atmosphere.
Because almost all the water vapor is concentrated in this atmosphere, plus a large number of particles, this is also the most dramatic layer. From the height of 1 1000 meters to about 30,500m, the atmospheric temperature is basically unchanged, with an average of -56.5℃, so it is called stratosphere (the actual situation is: below 25,000m, the temperature rises with the height. At the top of the stratosphere, the temperature rises to MINUS 43 to MINUS 33 degrees Celsius. The reason why the temperature in the stratosphere has such characteristics is that the atmosphere in this layer is far away from the earth's surface and is less affected by the ground temperature, and there is ozone at its top, which can directly absorb the radiant heat of the sun.
The stratosphere is less than a quarter of the whole atmosphere. In this layer of atmosphere, there is no up-and-down convection, only horizontal wind, so it is also called stratosphere. In addition, there is almost no water vapor in this atmosphere, and there are basically no meteorological changes such as clouds, fog, rain and hail, which is very beneficial to the smooth flight of the aircraft. However, due to the low air density, the aircraft is not suitable for maneuvering flight at this altitude.
Almost all human aviation activities are concentrated in the troposphere and stratosphere. In order to ensure the working efficiency of aircraft and engines, the flying height of aircraft generally does not exceed the limit of 30 kilometers.
The height range from 30 km to 80- 100 km is called the middle layer. The characteristic of this layer of air is that the temperature rises first and then falls, with a boundary of 45 kilometers. Due to the existence of a large amount of ozone, its temperature first rises from -33℃ at the top of the stratosphere to about17 ~ 40℃; Starting from 45km, with the elevation rising, the temperature began to drop again until it dropped to -65.5℃ to-1 13℃.
The air in the middle layer is already very thin, and its air quality only accounts for about 1/3000 of the whole atmosphere. At an altitude of 80 kilometers, the density of air is only one fiftieth of that of the ground; At the height of 100 km, the density of air is only eight ten thousandths of that of the ground. Because the air is very thin and the gas begins to ionize, people generally regard the aircraft flying at an altitude of 80- 100 km as a spacecraft flying without relying on the atmosphere.
1967 10, American test pilot Joseph Volcker flew the X- 15A rocket plane at an amazing speed of 7297 km/h, setting a world record for the speed of manned aircraft. Moreover, he flew to an altitude of more than 80 kilometers many times, becoming the first "astronaut flying a plane" in the United States. According to the regulations of NASA, pilots who fly more than 80 kilometers can be called astronauts.
800 kilometers above the mesosphere is called the ionosphere. It is characterized by containing a large number of positively or negatively charged ions, and air has conductivity. Moreover, its temperature rises rapidly with the elevation. At the height of 200 kilometers, the temperature can reach 400℃. Therefore, it is also called "warm layer".
Beyond the top of the ionosphere is the outermost layer of the atmosphere, the "escape layer". Due to the weakening of the earth's gravity, gas molecules and plasma have been kept at arm's length from the earth.
The air density in the ionosphere and stratosphere is extremely low, which has little effect on spacecraft. Therefore, most of human space activities are carried out inside (or outside) them.
The difference between aviation and aerospace;
Aviation and aerospace are two technical terms that people often come into contact with. Although there is only one word difference, it is called two technical categories. Why?
If we pay a little attention, we can find that aviation technology mainly develops military aircraft, civil aircraft and air-breathing engines, while aerospace technology mainly develops unmanned spacecraft, manned spacecraft, launch vehicles and missile weapons, and aircraft and spacecraft can best reflect their achievements. From the main differences between aircraft and spacecraft, we can see the significant differences between the two technical fields.
First, the flight environment is different. All planes fly in dense atmosphere, and their working height is limited. The maximum flying height of modern aircraft is more than 30 kilometers from the ground. Even if the aircraft height increases in the future, it will be inseparable from the dense atmosphere. After the spacecraft rushes out of the dense atmosphere, it will fly in a space close to vacuum with a motion law similar to that of natural celestial bodies, and the perigee height is at least 100 km. For spacecraft in operation, it is necessary to study the space flight environment.
Second, power plants are different. Airplanes use air-breathing engines to provide thrust, absorb oxygen in the air as oxidant, and only carry combustibles. The launch and operation of spacecraft use rocket engine to provide thrust, which carries both combustion agent and oxidant. Air-breathing engine can't work without air, while rocket engine can reduce drag and increase effective thrust without air. Air-breathing engines, including propellant tanks, can be used many times with aircraft, while launch vehicles for launching spacecraft are all disposable. Although the solid booster of the space shuttle can be reused for 20 times, and the liquid rocket engine of its orbiter can be reused for 50 times, compared with the air-breathing engine used in the aircraft, the number of uses is still very small. The propellants used in air-breathing engines are only aviation gasoline and aviation kerosene, while there are many kinds of propellants used in rocket engines, including liquid, solid and solid-liquid types.
Third, the flight speed is different. The fastest speed of modern aircraft is more than three times the speed of sound, and it is a military aircraft. As for the passenger planes in use now, they all fly at subsonic speed. In order not to fall to the ground, the spacecraft runs at a very high speed in space. For example, the speed of a spacecraft in a circular orbit 600 kilometers above the ground is 22 times the speed of sound. All spaceships are in weightlessness during normal operation. If manned for a long time, it will cause the physiological effect of weightlessness and affect health. Because of this, compared with pilots, the selection and training of astronauts are much stricter. Most people can fly as long as they buy tickets, but those who spend a lot of money to travel in space must also receive special training.
Fourth, the working hours are different. Whether military or civil aircraft, the maximum range is about 20 thousand kilometers, and the longest flight time does not exceed one day and night. Its scope of activities and working hours are very limited, and it is mainly used for military and transportation. Although light aircraft are widely used, the scope of each activity is relatively small. Spacecraft can work in orbit for a long time, for example, the Soyuz TM manned spacecraft, which is still in use, can run in space for several months after docking with the space station. Another example is the space shuttle, which can fly in orbit for 7-30 days and circle the earth for about 1.5 hours. The longest manned spacecraft is the Mir space station, which has been flying in space for 15 years. As for unmanned spacecraft, such as various application satellites, they have generally been working in orbit around the earth for many years. Some deep space probes, such as Pioneer 10, have been flying in space for 32 years and are flying out of the solar system to the Milky Way. The advantage of airplanes is that they can be reused many times, while spaceships can only be used once except the space shuttle, and manned spaceships are no exception.
Fifth, the promotion methods are different. The takeoff of an airplane is a movement process that starts from the takeoff line, slides off the ground and accelerates to climb to a safe height. When it returns to the ground, it just needs to land down. Only a few aircraft, such as the Harrier fighter in Britain, can take off and land vertically by turning the engine nozzle, but the fuselage is still in a horizontal position and not erected. So far, the launch of spacecraft, including ground and sea launches, as well as launch vehicles with spacecraft on them, are all vertical in the air. During the launch process, the launch vehicle should turn around and separate step by step according to the procedure, and finally send the spacecraft into the predetermined orbit. Some spacecraft have to undergo multiple orbital changes in the middle of launch, and the situation is more complicated. Although the space shuttle can also launch spacecraft, it is also a vertical launch. As for the recoverable spacecraft, its return to the ground must go through four stages: derailment, transition, reentry and landing, which is far more difficult than the landing of the aircraft. Although the takeoff, flight and landing of aircraft and the launch, operation and return of spacecraft are inseparable from the command of the ground center, the ground facilities and support systems, as well as their working performance and content, are also very different.
World aerospace events:
Kites originated in ancient China and spread to Europe around14th century.
In 500-400 BC, people in China began to make wooden birds and test primitive aircraft.
1909 The world's first light aircraft was born in France.
From 1903 12 14 to 17, the "Flyer" 1 designed and manufactured by the Wright brothers realized autonomous flight for the first time in the history of human aviation. The successful test flight has become an epoch-making event, and the history of human aviation has entered a new era.
19471June14th, Charles yeager, a famous American test pilot, broke the sound barrier in the X- 1 plane.
1at 22: 56: 20 on July 20, 969, Amster took a small step and became a giant step for all mankind on earth.
1957 10 October 4th
The former Soviet Union launched the world's first artificial earth satellite. Six months later, an American satellite flew into the sky.
1959 September 12
The former Soviet Union launched the "Moon" 2 probe, which was the first spacecraft in the world to hit the surface of the moon.
1961April 12.
Former Soviet astronaut Gagarin became the first person in the world to fly into space.
1July 20, 969
American astronaut Armstrong became the first man to set foot on the moon in Apollo 1 1 spaceship.
1970 65438+February 15
The former Soviet probe Venus 7 landed on Venus for the first time.
1971April 9
The Salute Space Station of the former Soviet Union 1 became the first space station for human beings to enter space. Two years later, the United States sent the Skylab space station into space.
197 1 year 65438+February 2.
The former Soviet "Mars" 3 probe landed on the surface of Mars. Five years later, the American Viking Mars probe landed on Mars.
1981April 12.
The world's first space shuttle, the American space shuttle Columbia, was successfully launched.
1986 65438+1October 28th
The American space shuttle Challenger exploded 73 seconds after liftoff.
1February 20, 986
The former Soviet Union launched the "Peace" space station, which has been in service for 8 years and is still in operation. It is the most successful human space station at present.
1 993165438+1October1.
The United States and Russia signed an agreement to build the International Space Station on the basis of the "Peace" space station and named it the Alpha International Space Station.
Major space events in China;
1956, 10, 10 On October 8th, China's first rocket and missile research institution, the Fifth Research Institute of the Ministry of National Defense, was established.
1970 On April 24th, the Long March-1 carrier rocket successfully launched the Dongfanghong-1 satellite at Jiuquan Satellite Launch Center, making China the third country in the world to independently develop and launch satellites.
1975165438+1On October 26th, the Long March II D carrier rocket successfully launched China's first recoverable rocket at Jiuquan Satellite Launch Center.
The recoverable scientific experimental satellite was successfully recovered after 3 days.
1On April 8th, 984, cz-3 successfully launched China's first geosynchronous orbit satellite-Dongfanghong-2 experimental communication satellite in xichang satellite launch center.
1On April 7th, 990, China successfully launched the Asia-1 communication satellite in xichang satellite launch center with the independently developed cz-3. This was the first time that China's Long March series launch vehicles launched a foreign satellite, which made China occupy a place in the world space commercial launch service.
1999 5438+00 In June, the first Earth resources satellite jointly developed by China and Brazil was successfully launched and operated normally, which was the first comprehensive international cooperation in the field of space technology in China.
June 5438+1October 65438+May 2003 Shenzhou 5 successfully launched and successfully recovered June 65438+1October 65438+June 2003, and China became the third country in the world to independently master manned space technology.
From June, 5438 to February, 2003 and July, 2004, China and the European Space Agency jointly developed and launched the scientific satellites Exploration I and Exploration II, and the "Earth Space Double Star Exploration Program" was a complete success.
On June 23rd, 2004, China's lunar exploration project was officially approved by the State Council.
June 65438+1October 65438+February 2005, Shenzhou VI was successfully launched.