This is what astronauts described when they talked about seeing the earth from the space shuttle.
The development of space technology is one of the most remarkable undertakings in the world today, which promotes the progress of human science and technology and expands the field of human activities from the atmosphere to space. Space technology is the crystallization of modern science and technology and the integration of basic science and technical science. Space technology is an important symbol of a country's scientific and technological level.
Aerospace technology is a comprehensive engineering technology, which mainly includes: guidance and control technology, thermal control technology, jet propulsion technology, energy technology, space communication technology, telemetry and telecontrol technology, life support technology, aerospace environmental engineering technology, rocket and spacecraft design, manufacturing and testing technology, spacecraft launch, return and on-orbit technology. The aerospace system integrated by various technologies is a complex large-scale modern high-tech system, which is not only large in scale, high in technology and cutting-edge, but also consumes huge manpower and material resources and has a long engineering cycle. Today, space technology has been widely used in political, military, economic and scientific exploration fields, and has become a symbol of a country's comprehensive national strength.
Humans have long had the ideal of traveling in space and conquering the universe. The universe has always been full of attraction and mystery for human beings. Many beautiful myths and legends reflect the yearning for the universe and the mood of exploring the mysteries of space. The Goddess Chang'e flying to the moon, the Cowherd and the Weaver Girl, and the Monkey King's walking and somersaulting.
The history of space flight begins with the history of rocket technology. Without rockets, there would be no space flight. Tracing back to the source, China was the first country to invent the rocket. The word "rocket" appeared in the Three Kingdoms period (AD 220-280). But at that time, the rocket was just tied with combustible materials at the front end of the shaft and then fired with a crossbow, so it was also called "burning an arrow".
With the appearance of gunpowder, one of four great inventions of ancient china, gunpowder replaced flammable materials, making rockets quickly applied to the military. There are written records in the late Tang Dynasty and early Song Dynasty that rockets use gunpowder. Although the rockets at this time used gunpowder, they still used crossbows to shoot. Wu Bei Zhi, edited by Mao in the Ming Dynasty, recorded the shape of a rocket that was really propelled by gunpowder rather than fired by a crossbow, as shown in figure 1. 1.
Although this primitive rocket is not as complicated as a modern rocket, it already has a warhead (arrow), a propulsion system (powder keg), a stability system (tail wing) and an arrow body structure (arrow shaft), which can be considered as the embryonic form of a modern rocket.
The Chinese nation not only invented the rocket, but also applied series (multi-stage) and parallel (bundling) technology for the first time to improve the carrying capacity of the rocket. The "flying crow with divine fire" recorded in Ming History is the embodiment of parallel technology; "Fire dragon effluent" is a concrete application of series-parallel integration technology, as shown in figure 1.2.
The world's first "astronaut" who tried to fly into the sky by rocket also appeared in China. According to legend, at the end of14th century, there was a man named "Wan Hu" in China. Holding a big kite in one hand, he asked others to tie himself to a special seat with 47 biggest rockets (also called "fire") behind it. He tried to realize the ideal of "taking off" with the help of the thrust of the rocket and the aerodynamic lift of the kite. Although Wan Hu's brave attempt failed and gave his life, he was still the first person in the world who wanted to use the power of rockets to fly.
/kloc-at the end of 0/9 and the beginning of the 20th century, rockets flourished again. With the development of modern rocket technology and space flight, many pioneers who dare to explore have emerged, among which K.3. tsiolkovsky (~ OHCTAHTH3Yap and oBHq UHOaKOBCKHfi), R.Goddard and H.oberth are the representatives.
Tsiolkovsky, a scientist of the former Soviet Union, devoted his life to the research of space flight by using rocket technology. In his classic works, he profoundly demonstrated the idea of rocket flight, and proved theoretically that multistage rockets can overcome gravity and enter space at the earliest.
1, the basic mathematical equation of rocket motion is established, which lays the foundation of astronautics.
2. Firstly, it is affirmed that liquid rocket engine is the most suitable power device for spacecraft, and the possibility of using liquid hydrogen-liquid oxygen as rocket propellant is discussed, which points out the direction for the development of launch vehicles. These views have become a reality in just a few decades.
3. It is pointed out that new fuel (energy of nuclear decomposition) has been used as the power of rocket; This paper expounds in detail the conditions of space flight with rockets, the conditions of rocket taking off from the ground and the assumption that intermediate stations must be established when flying to other planets.
4. Many technical suggestions are put forward, such as using gas rudder to control rocket, using pump to press propellant into combustion chamber, and using instruments to control rocket automatically, which have played a great role in the development of modern rocket and space flight.
Dr Goddard, an American rocket expert, physicist and one of the founders of modern astronautics, began to study modern rockets in 19 10. In his paper "Methods to Reach Extremely High Altitude" published in 19 19, he expounded the mathematical principle of rocket flight and pointed out that a rocket must have a speed of 7.9 km/s to overcome the gravity of the earth, and
In the book "Rocket to Interstellar Space" published by 1923, German professor Aubert not only established the basic principle of rocket working in space vacuum, but also explained that the rocket can orbit the earth as long as it can generate enough thrust. Like tsiolkovsky and Goddard, he has conducted extensive research on many propellant combinations.
1932, Germany launched A2 rocket with a flying height of 3 km. 1942 19421On October 3rd, Germany successfully launched the first ballistic missile V2(A4) in human history for the first time and put it into use for the first time on September 6th, 1944.
The success of V-2 realized the technical idea of space technology pioneers at the end of 19 and the beginning of the 20th century, trained and brought up a large number of rocket experts with practical experience, and played an important role in the development of modern large rockets. Although the design of V-2 is not perfect, it is the first tool that human beings have to challenge the gravity of the earth and has become an important milestone in the history of space technology development.
1957101October 4th, used by the former Soviet Union? Satellite? The world's first artificial earth satellite was sent into space by the launch vehicle "X". The satellite is spherical, with an outer diameter of 0.58m and four strip antennas, with a mass of 83.6kg.. The satellite worked normally in the sky for three months. According to today's standards, the first satellite of the former Soviet Union was just a sphere extending from the transmitting antenna, but it was the first artificial celestial body in the world. It turned the dream of mankind for thousands of years into reality, created a new space age for mankind, and marked another leap in the scope of human activities.
1961April 12, the former Soviet union successfully launched the first ship? Oriental? Manned spacecraft, yuri gagarin became the first human astronaut, which opened the prelude of human entering space and started a new era of manned space flight in the world.
1On August 27th, 962, Mariner 2 launched by the United States successfully flew over Venus for the first time.
1July 20, 969, N.A. Armstrong and E.E. Aldrin of the United States took a ride? Apollo 1 1? The spacecraft successfully landed on the moon and landed in the southwest corner of the moon's sea of tranquility, becoming the first people to set foot on another celestial body outside the earth. They put scientific experimental devices on the moon, took photos of the surface of the moon, collected 22 rainbow samples of moon rocks and soil, and then took off from the surface of the moon, joined the command module and returned to Earth. The ideal of man landing on the moon has come true for the first time.
1971April19, the former Soviet union? Salute 1? The space station has been manned successfully, with a mass of about 18 t, a total length of 14 m, an orbital height of 200~250 km and an orbital inclination of 5 1.6. Became the first space station of mankind, completed scientific research plans in astrophysics, aerospace, medicine and biology, inspected the earth's resources, and conducted technical experiments under long-term weightlessness.
1on March 2, 972, the United States launched Jupiter and a deep space probe? Pioneer 10? . It carries a gold-plated aluminum plate that displays human information. After flying for 1 1 years, it crossed Neptune's orbit in June of 1983, and then became the first artificial celestial body to fly out of the solar system.
1June 8, 975, launched by the former Soviet Union? Venus 9? The probe landed on the surface of Venus.
1975 USA July 18? Apollo? Spacecraft and the former Soviet Union? Alliance 19? The spacecraft successfully docked over the Atlantic Ocean (video data).
1August 20, 975, launched in the United States? Pirates 1? The probe successfully landed on the surface of Mars for the first time (video data).
1September, 977, launched in the United States? Voyager 2? +/-The detector detects Uranus and Neptune.
1981April, the world's first reusable American space shuttle took off vertically and landed horizontally? Colombia? The successful test flight marks a new stage of the transformation of space launch vehicle from disposable launch vehicle to reusable space launch vehicle. This is an important milestone in the history of space flight, which indicates that by going up one flight of stairs entered the space shuttle era in the space age. By June 2000, the space shuttle had successfully flown 65,438+000 times.
1986 February, the former Soviet Union? Mill? The orbital space station was successfully launched, becoming the manned spacecraft with the longest launch time, and its in-orbit operation time exceeded 15 years. March 23, 2006 5438+0, Mir? The orbiting space station was introduced into the atmosphere and destroyed, completing its brilliant historical mission.
At present, with the cooperation of the United States, Russia, Canada, Japan, Italy and the European Space Agency, a larger international space station is being assembled in orbit.
Man is knocking on the door of the universe at such a fast speed!
It is not difficult to see that from the China rocket in the 10 century to the V- 12 missile in World War II, human beings developed rocket technology for military needs, which laid a solid foundation for the development of space technology. Since the 1940s, space technology has been developing at an alarming rate and getting better and better. We can firmly believe that with the progress of science and technology and the continuous strengthening of industrial base, space technology will make greater breakthroughs and become more perfect.
Space technology developed from the research and experiment stage in the late 1950s to the mid-1970s, and reached the stage of extensive practical application. Since the 1960s, various scientific and applied satellites serving scientific research, national economy and military affairs have made great progress. By the 1970s, military and civilian satellites had fully entered the application stage. On the one hand, it specializes in research on reconnaissance, communication, navigation, early warning, meteorology, geodesy, oceanography, astronomical observation and earth resources, on the other hand, all kinds of satellites are developing in the direction of multi-purpose, long life, high reliability and low cost.
Looking back on the application of space technology in the past 50 years, the representative events are as follows:
1958 18 in February, the United States launched the world's first communication satellite? Skoll? ;
1960 in April, the United States launched the world's first meteorological satellite? Tyros 1? And navigation satellites? Meridian 1B? ;
1in July 1963, the United States launched the world's first geosynchronous orbit communication satellite;
1In August 1964, the United States launched the world's first geostationary orbit communication satellite;
1in April, 965, the United States successfully launched the world's first commercial communication satellite? Intelsat 1？ The official provision of communication services between North America and Europe marks the practical stage of communication satellites;
1972 in July, the United States launched the world's first earth resources satellite? Landsat 1？ ;
1982165438+10, the U.S. space shuttle started commercial flight; 1984165438+1October, the US space shuttle successfully released two satellites and recovered two failed communication satellites, realizing the two-way carrying mission for the first time;
1in April 1983, the United States launched the world's first tracking and data relay satellite;
1999, the United States consists of 66 small satellites? Iridium? The satellite global telephone communication system was built and put into use.
At present, American GPS system and Russian satellite navigation system have become widely used positioning and navigation systems in various fields all over the world, playing a huge role.
In China, after the first satellite on April 24th, 1970? Dongfanghong No.1? Since the successful launch, great achievements have been made in the development and application of space technology:
1975165438+10, China's first recoverable remote sensing satellite was successfully launched and recovered;
1in April 1984, China's first geostationary orbit test communication satellite was successfully launched;
1February 1986, China's first geostationary orbit practical communication satellite was successfully launched;
1September 1988, China's first meteorological satellite? Fengyun-1? The launch was successful;
By June 2000 10, China? Long March? The series of launch vehicles have been successfully launched 62 times.
In the 1990s, the pace of space technology application in China was further accelerated, and large-capacity communication satellites? Dongfanghong No.3? , meteorological satellite? Fengyun-1? And then what? Fengyun 2? The resource satellite has been successfully launched.
1999165438+1On October 20th, China successfully launched its first experimental spacecraft? Shenzhou? A solid step has been taken in the field of manned spaceflight.
To sum up, it is only 40 years since 1957, when the world's first artificial earth satellite was successfully launched. It is unprecedented that space technology has made such great achievements and produced enormous social and economic benefits.
In short, with the development of the application of space technology, space activities are increasingly showing its great military significance and economic benefits, and have become an important part of the national economy and national defense construction. In turn, this social and economic benefit has further promoted the rapid development of space technology.
Space technology is an engineering technology to study and realize how to send spacecraft into space and conduct activities there. It mainly includes three parts: spacecraft, carrier and ground measurement and control. For the sake of understanding, we first classify spacecraft.
The same spacecraft can have several missions and cannot be mechanically and absolutely classified. The same spacecraft often includes several series, and each series can be divided into several different satellite systems or models.
Spacecraft can be divided into unmanned spacecraft and manned spacecraft. Unmanned spacecraft can be divided into artificial earth satellites and space probes according to whether they orbit the earth or not. It can also be further classified according to the purpose, as shown in figure 1.3.
Satellites are the largest number of spacecraft (accounting for more than 90%). Their orbital lengths range from 100 kilometers to hundreds of thousands of kilometers. According to their uses, they can be divided into:
At present, manned spacecraft only fly in low-earth orbit, from the earth to the moon. In the future, there will be manned spacecraft and permanent space stations that can reach various planets for human beings to live and work in space for a long time. Manned spacecraft can be divided into:
A reusable spacecraft shuttles between the ground and near-earth orbit with an altitude below 1000 km to transport payload.
3. Space probe
Voyager 1 Voyager 2
According to the function of spacecraft in orbit, artificial earth satellites can be divided into four categories: observation stations, relay stations, reference stations and orbital weapons. Each category includes spacecraft with different purposes.
The satellite is in orbit. For the earth, stand high and see far (big vision). It is very beneficial to observe the earth with it. In addition, because the satellite is free from all kinds of interference and influence from the atmosphere outside the earth's atmosphere, it has more advantages than the ground observatory in astronomical observation. Satellites with this function have the following typical uses.
Among all kinds of application satellites, reconnaissance satellites were launched the earliest (1959) and the largest number were launched. There are two kinds of reconnaissance satellites: photographic reconnaissance and electronic reconnaissance satellites.
Resource satellites are developed on the basis of reconnaissance satellites and meteorological satellites. Multi-spectral remote sensors on satellites are used to acquire electromagnetic waves of various bands radiated and reflected by ground targets, and then transmit them to the ground, and then process them into useful information of earth resources. They include ground and underground, land and sea, etc.
The task of marine satellites is to forecast the marine environment, including the selection of the best route for ocean-going ships, the analysis of marine fish resources, the investigation of offshore and coastal marine resources, the monitoring of coastal and offshore marine environment, the prediction and early warning of disastrous sea conditions, the protection and law enforcement of marine environment, marine scientific research, marine buoys, data transmission between stations and ships, and maritime military activities.
Of course, there are more satellites as observation stations, such as early warning satellites, nuclear explosion detection satellites and astronomical prediction satellites (such as the Hubble Space Telescope in the United States). Although their functions are different, the basic observation principle is similar.
2. Relay station
Compared with ordinary terrestrial communication, satellite communication has the following advantages:
① Large communication capacity;
② Wide coverage;
③ Long communication distance;
④ High reliability;
⑤ Good flexibility;
⑥ Low cost.
Broadcasting satellite is a kind of communication satellite mainly used for TV broadcasting. This kind of broadcasting satellite can broadcast or transmit TV programs to the ground without any transit, and it can be directly received by public organizations or individuals, so it is also called direct broadcast satellite. At present, an ordinary household TV set with an antenna diameter less than 1m can directly receive TV broadcast programs from direct broadcast satellites.
Tracking and data relay satellite is an important development of communication satellite technology. It uses satellite tracking to measure the position of another satellite, and its basic idea is to move the monitoring station on the earth to geosynchronous orbit to form a satellite-ground monitoring system network.
3. Reference station
This kind of satellite is the reference point of on-orbit measurement, which requires very accurate orbit measurement. Satellites that belong to this function are:
4. Orbital weapons
This is an active attack spacecraft, which has the functions of space defense and space attack. Mainly includes:
Different types of spacecraft have different systems in structure, appearance and function, but their basic system composition is the same. A typical spacecraft consists of several subsystems with different functions, and its basic systems are generally divided into two categories: payload and support system.
1. Payload
Components, instruments or subsystems used to directly complete specific space tasks.
There are many kinds of payloads, which vary with different tasks, that is, the functions of spacecraft are different. For example, particle detectors on scientific satellites, astronomical telescopes on astronomical observation satellites, visible light cameras on reconnaissance satellites, CCD cameras, infrared detectors and radio reconnaissance receivers, visible light and infrared scanning radiometers on meteorological satellites, television cameras, CCD cameras, thematic mappers, synthetic aperture radars on earth resources satellites, transponders and communication antennas on communication satellites, seeds and culture media on biological science satellites, etc. Are all payloads.
A single-purpose satellite can carry one type of payload, while a multi-purpose satellite can carry several types of payloads.
2. Security system
It is used to ensure the normal work of all subsystems on the spacecraft from rocket takeoff to the end of working life. The support systems of various types of spacecraft generally include the following subsystems:
(1) structural system: it is used to support and fix all kinds of instruments and equipment on the spacecraft to form a whole, so as to withstand all kinds of mechanical environments (vibration, overload, impact, noise) and space operating environment during ground transportation, carrier launch and space operation. The basic requirements for spacecraft structures are light weight, high reliability and low cost, so most spacecraft structures are made of light alloys such as aluminum, magnesium and titanium and carbon fiber composites. Usually, the structural quality ratio, that is, the ratio of structural weight to the total weight of spacecraft, is used to measure the structural design and manufacturing level of spacecraft.
(3) Power supply system: it is used to provide all instruments and equipment of the spacecraft with the required electric energy. Modern spacecraft mostly use the combined power supply system of solar cells and storage batteries.
(4) Attitude control system: used to maintain or change the running attitude of the spacecraft. The commonly used attitude control methods include gravity gradient stability, spin stability and three-axis stability.
(5) Orbit control system: used to maintain or change the orbit of spacecraft. Orbit control and attitude control are often combined to form a spacecraft control system.
(6) Measurement and control system: including telemetry, remote control and tracking. The telemetry part is mainly composed of sensors, modulators and transmitters, and is used to measure and send engineering parameters (voltage, current, temperature, etc. 2 12). ) and other parameters (environmental parameters and attitude parameters, etc. ) all kinds of instruments and equipment of the spacecraft are transported to the ground. The remote control part is generally composed of a receiver and a decoder, which is used to receive the remote control instructions sent by the ground monitoring station and transmit them to relevant systems for execution. The tracking part mainly consists of beacons and transponders, which constantly send out signals so that the earth monitoring station can track the spacecraft and measure its orbital position and speed.
In addition to the above basic system components, spacecraft often need some special systems, which have different functions according to their different tasks. For example, recoverable satellites have recovery systems, manned spacecraft have crew systems, environmental control and life support systems, rendezvous and docking systems, and space shuttles have landing systems.
The motion of a rigid spacecraft can be described by its position, velocity, attitude and attitude motion. Among them, position and velocity describe the motion of the center of mass of the spacecraft, which belongs to the orbit problem of the spacecraft; Attitude and attitude motion describe the rotation of spacecraft around the center of mass, which belongs to attitude problems. From the kinematic point of view, the motion of spacecraft has six degrees of freedom, of which three degrees of freedom in position represent the orbital motion of spacecraft, and the other three degrees of freedom in rotation around the center of mass represent the attitude motion of spacecraft.
Spacecraft control can be divided into two categories, namely orbit control and attitude control.
1. Orbit control
Orbit control includes orbit determination and orbit control. The task of orbit determination is to study how to determine the position and speed of spacecraft, sometimes called space navigation. Orbit control is a technology that applies control force to the center of mass to change its trajectory according to the existing position, speed and ultimate goal of spacecraft, sometimes called guidance.
According to the application mode, track control can be divided into four categories.
(1) orbital maneuver:
Refers to the control of spacecraft's orbit transfer from one free flight segment to another. For example, in order to enter the geostationary orbit during the launch of a geostationary satellite, it is necessary to perform orbital maneuvers at the apogee of its transfer orbit.
(3) Orbital rendezvous: refers to the control process in which one spacecraft and another spacecraft can reach the same position in space at the same speed.
(4) Reentry control: refers to the control of the spacecraft leaving the original orbit and returning to the atmosphere.
2. Attitude control
Attitude control also includes attitude determination and attitude control.
Attitude determination is a method to determine the attitude of spacecraft relative to a certain reference. This reference can be an inertial reference or a reference that people are interested in, such as the earth.
Attitude control is a process of spacecraft orientation in a specified or predetermined direction (which can be called reference direction), including attitude stabilization and attitude maneuver. Attitude stability refers to keeping the attitude in a specified direction, while attitude maneuver refers to the redirection process of spacecraft from one attitude to another.
Attitude control usually includes the following specific concepts.
(1) azimuth: refers to the fuselage or accessories of the spacecraft (such as solar array, observation equipment, antenna, etc.). ) in a single axis or three axis with a certain accuracy in a given reference direction. This reference direction can be inertial, such as astronomical observation; It can also be rotating, such as earth observation. Because the orientation needs to overcome all kinds of spatial interference to keep in the reference direction, it needs to be maintained by control.
(2) Redirection: refers to the change of the orientation of the spacecraft body from one reference direction to another new reference direction. The redirection process is realized by continuous attitude maneuver control.
(3) Capture: Also known as initial alignment, refers to the maneuvering control process of spacecraft from unknown uncertain attitude to known directional attitude. For example, when the spacecraft is in orbit, the star and arrow are separated, and the spacecraft enters the earth-to-sun orientation attitude from uncertain attitudes such as rotation and rolling; Another example is the attitude re-determination after the spacecraft loses its attitude due to a fault during operation. In order to make the control system design more reasonable, the acquisition is generally divided into two stages: coarse alignment and fine alignment.
(4) Rough alignment: refers to the initial alignment, which usually requires a large control torque to shorten the maneuvering time, but it does not require high orientation accuracy.
(5) Fine alignment: refers to the correction maneuver after coarse alignment or repositioning because the accuracy is not enough to ensure the accuracy requirement of orientation. Generally speaking, a small control torque is used for precise alignment.
(6) Tracking: means that the spacecraft body or accessories keep the orientation of the moving target.
(7) Search: refers to the capture of moving targets by spacecraft.
In a word, attitude control is a process of acquiring and maintaining the orientation of spacecraft in space. For example, satellite communication or earth observation, antenna or remote sensor should be aimed at ground targets; When the satellite is in orbit control, the engine should aim at the required thrust direction; When the satellite re-enters the atmosphere, it is necessary to brake the heat protection surface to a quasi-oncoming airflow. All these require the stars to establish and maintain a certain attitude.
Attitude stabilization is the control to maintain the existing attitude. According to the form of spacecraft attitude motion, spacecraft attitude stabilization methods can be roughly divided into two categories.
(1) Spin stability: Spacecraft such as satellites rotate around an axis (spin axis), and the orientation of the spin axis in inertial space is maintained by the rotating moment of momentum. Spin stability is usually supplemented by active attitude control to correct the pointing error of spin axis.
(2) Three-axis stabilization: the three orthogonal axes of the spacecraft body are kept in the reference space direction through active attitude control or using environmental torque.
3. Relationship between attitude control and orbit control.
Spacecraft is a complex control object. Generally speaking, orbit control is closely related to attitude control. In order to realize orbit control, the attitude of spacecraft must meet the requirements. That is to say, when the spacecraft needs orbit control, it also needs attitude control. Attitude control and orbit control can be considered separately in some specific situations or in some flight processes. Some application tasks do not have strict requirements on the orbit of spacecraft, but have requirements on the attitude of spacecraft.
According to the source of control force and torque, spacecraft control can be divided into two categories.
(1) Passive control: Its control force or torque is provided by space environment and spacecraft dynamics characteristics, and it does not consume on-board energy.
4. Composition of active control system
Spacecraft active control system, whether attitude control system or orbit control system, has two components.
(1) Airborne autonomous control: refers to the control completely realized by airborne instruments without ground intervention, and its system structure is shown in Figure 1.4.
(2) Ground control: or "satellite-ground large loop control" refers to the control realized by combining airborne instruments and ground equipment with ground intervention, and its structure is shown in Figure 1.5.