HISTORY, FEATURES, COMPONENTS AND TYPES OF SATELLITE
Sputnjik - the first Earth's artificial satellite
intercontinental ballistic missile (ICBM)
which could launch a nuclear warhead at a distance of around 4000 miles, easily sent, 4. October 1957. year, with "cosmodrome" in Baikonur
(Kazakhstan today) in the orbit of the first artificial satellite. The official name was "A friendly companion of the Earth." Companion, and Sputnik, after lengthy hundred minutes after launch, once again found above the same point, and its radio signal confirmed the success of the launch. Only then official Soviet agency TASS news telegraphed around the world. Cosmic time is started. Unfortunately, the Soviet paranoia reason is that they are not taken photos of the historic launch. Sputnik 1, a tiny aluminum sphere just bigger than a basketball ball, with antennas that slid like the oversized mustache Feliks, at that time a popular character from cartoons, was too small to be visible from Earth. The tiny satellite 58 cm in diameter, 83.6 kg weight circled around the Earth at a variable height from 228 to 947 km, with a period of 98.6 minutes, then a fantastic speed of 17,000 miles per hour. It was designed to emit radio signals, by which scientists wanted to determine the density of the upper part of the atmosphere. Though these signals have already been silenced by 21. the day after launch, the Soviet Union, albeit with its allies, liked it. Sputnik 1 was launched in space in the heat of the Cold War, the first earth art satellite. An unbroken series of monotonous beep-beep-beep
radio signals shocked the United States, which considered themselves technological superpower unrivaled. Sputnik in space remained total 92 days, and the 4. January 1958. The burned in the atmosphere. Preliminary father of Sputnik was Sergei Korolev
(1907-1966), Soviet counterpart Wernher von Braun. Sputnik had a spherical shape because the aerodynamics of the sphere were easy to predict, and tiny changes in flight characteristics could change by moving the center of gravity. The sphere, in addition, has the most favorable relationship between volume and abundance. So the next Soviet satellites had the shape of a ball. Career Sergei Koroljov culminated in 12. April 1961. When the spacecraft, which he also designed, Jurij Gagarin, As the first man catapulted into space. However, Korolev is the general public was virtually unknown, never publicly wearing decorations, and even his rare photos - all for fear of American intelligence, and the CIA. The award was Korolev arrived only after death, when one of the Moscow suburbs called his name.
Space Race - Sputnik-2, Explorer-1, StarWars
Demonstrating the evil (albeit brief) Soviet superiority in space exploration, Sputnjik was even more intensified by fears of nuclear destruction among Americans. It has appeared at a time when science with important discoveries such as penicillin, radar, nuclear bomb, etc., helped win over Naci-fascism in II. world war. Today, when more than ten years have passed since the Soviet Union split, a orbital cell
Mir, which was the last remaining Soviet space program, was devastated in the aftermath of the universe between the rifles and the catastrophe, it is difficult to spell the spell of the Sputnjik in the 1950s. She ruled that it is fearful that "red scientists" could get a cold war. Physicist Edward Teller, the creator of a thermonuclear bomb, said the US lost the battle more important than the one in Pearl Harbor. The then senator, later 36. president of the USA, Lyndon Johnson he said that control of the universe means control of the world. II Rabi, chair of the then-US President's Council of Science Dwight Eisenhower, Warned that the emphasis on math and science in general in the Soviet educational system to provide a strategic advantage to the enemy of 10 years. It seemed then that Sputnik is a system superior to capitalism, and proved to be useful in solicitations states that have not yet chosen a side in the cold war. This is evidenced by numerous series of philatelic stamps, depicting Sputnik issued in many countries around the world, including the former Yugoslavia. But Yugoslavia has already tried to be non-aligned: to not hurry with the release of commemorative series of stamps have been time for it to marki (denomination 0.30 Dinar) are jointly displayed Sputnjik and Explorer - the first Russian and first American satellite. However, in Yugoslavia, as a mushroom, after the rain, various societies of "lovers of cosmos" were born. The race for universe dominance has become a metaphor for the Cold War, and for Americans it was either a question of whether or not to be. The US Army was painfully aware of the power of Soviet intercontinental ballistic missiles (ICBM). President Eisenhower knew that several rocket system development projects were in progress in America, and he did not share public concerns about launching Sputnik. No, 3. November 1957., the universe is in Sputnik 2 started the first space traveler, doggy dogskin. Seven days ago, Lajka circled around the Earth in 508.3 kg body weight, with a period of 103.75 minutes, and visited the Earth hundreds times. Then the most up-to-date devices reported to scientists in the Earth's flight control data about Breathing, Blood Pressure and Heart Rate, and the radiation dose received by her body. As there was no device to return to Earth, the last piece of Lajkine's food that was "served" by a special machine at regular intervals, contained a strong poison from which the unlucky dog died immediately. But a tiny satellite, the diameter of only 15 centimeters, ended with the unsuccessful launch, 6. December 1957. The plummeting satellite falling to the Earth in the dead manhole still emitted radio signals. The newspapers recorded this event sarcastically by calling the American satellite "Flopnik", "Kaputnik" and "Stayputnik." And another American attempt, 25. January 1958., already burst 14 seconds after launch. The US officials then turned to an army, where a pioneering group was in the base Redstone Arsenal (Huntsville, Alabama) was trying to find an answer to the Soviet intercontinental missile. And indeed, already 31. January 1958., from Cape Canaveral launched a modified Redstone rocket satellite Explorer-1. However, Congress has acted presciently recognized the strategic value of education. Despite the budget deficit, approved a law that is separate from the budget then huge sum of one billion dollars to improve the education system, the purchase of scientific equipment and scholarships for gifted students. Sputnik has also initiated the debate on the reform of the US education system, and the debate about the new curricula. Began to apply new teaching methods with regard to improving the learning process. Emphasis is placed on experimental teaching, and not just learning facts by heart. In the US, the classrooms also "slipped" and interest in space exploration. Glenn T. Seaborg, a Nobel Prize chemist with a long-standing interest in scientific education, believes that another lesson has been taught from a small satellite: teachers and professors themselves must be scientifically educated. The reform of the economy later stalled, partly even turning to a stranger. The result was elitism and reduced "natural science literacy" of the majority of the population. Namely, those who did not care about natural sciences were able to completely avoid the system of dialing their education courses. Still, the seeds sown in the sixties, the eighties, were generously born to giants like Steve Jobsa,
Bill Gates, Brand AndreessenaAnd others that have marked the end of XX. Century computer and communications revolution. Given the space race, the Soviets is definitely lost, unsuccessfully trying to find an answer to the Strategic Defense Initiative, popularly called Star Wars (Star Wars). It was the most complicated military-research project in history approved by the president Reagan
1983. years. The goal was to establish a satellite defense system that would protect the US from laser weapons by the so-called " the first shock to nuclear missiles, and the "hostile" satellites. It was an extra blow to the shrinking, technologically outdated economy of the Soviet Union, which could not withstand the price of a raced arms race. It is interesting that this project faded after the collapse of the Soviet Empire, and it was only 1998. the US Department of Defense approved a laser beam test. Russian officials do not particularly care about them, they have other problems today, such as paying Kazakhstan a lease of $ 450 million for the space shuttle in Baykonur. In Russia, there was not a great celebration of forty-centuries of Sputnik, except in the universe itself. At the Russian orbital station Peace, after a successful merger with the American spacecraft
AtlantisAmerican astronauts and Russian cosmonauts, 30. September jointly celebrate the fortieth anniversary of the launch of Sputnik. Former space race today has turned into cooperation. Sputnik has also finally become what he had always been, the common heritage of all earthlings.
Launching satellites in orbit
Satellite (from the Latin satelles - companion, companion) in the broadest sense of the astronomical celestial body, which under the laws of celestial mechanics is moving around another body much greater weight and dimensions. For example, the moon is Earth's natural satellite and the Earth's natural satellite of the sun. The artificial satellite is the product of man and artificially introduced into orbit around the Earth.
The way the satellite travels around the Earth is called the orbit. To have the satellite circulate around the Earth, a number of conditions must be met. The body, that is, the satellite must have such a speed that its centrifugal force is equal to the gravitational force of the earth, so that the earth can not attract gravity to itself. That speed is first cosmic (orbital) speed and it would have an 7,906 km / s on the Earth's surface (when there was no air resistance). The first cosmic speed decreases with the distance from Earth. The second requirement for a successful satellite spin around the Earth is that the plane of the orbit of satellites always knocks the Earth's center. The orbit whose plane would not cut off the Earth's center, is not possible.
Setting up a satellite in orbit around the Earth requires accurate guidance in three-dimensional space, precise positioning and achieve the necessary speed with very little error. The reasons for all this are not particularly complex. The planets orbit the sun by the laws of that is still 17. century discovered Kepler on the basis of
Galilean budget. But for orbital flights probably the most important role plays Newton
the principle that bodies move straight-line until there is a force in them.
The universe controls only four forces: two are related to atomic events, one is responsible for electromagnetic radiation, and is the fourth gravity. This last one holds the satellites in their path around a celestial body or planet in the circle around the sun. Take for example the satellite that flies around the Earth: gravity, harder force, acting continually and pulling it down, toward the center of the planet. But as this weight-dependent gravity (with gravity is proportional to it), it operates on a satellite that is unique to our planet. The moon has a smaller mass of earth and the body attracts less force; The sun, on the other hand, has a much larger mass, so its appealing force is greater. Let's go back to our planet: the object close to its surface will be drawn to the center of acceleration from 9,8 m / s ^ 2, so in the first second it will fall 4,9 meters. The curvature of the earth's surface is exactly such that at a distance of almost 8 km falls for the mentioned 4,9 meters. Thus, if we can run an object at a speed of about 8 km / s, or around 28000 km / h, it will always circulate around the Earth, because every second to the surface will be attracted to exactly the distance the planet is "fleeing" from it 8 km. The body running at a speed of almost 8 km / s falls to the Earth as quickly as it apparently moves away. It will never fall to the surface of the planet and will circulate eternally around it - provided it is above the atmosphere that could be blocked. If he fails, he will go to Earth because the planet will "overcome" him. On the other hand, speeding up the body more than needed to overcome the force will hurt the planet around a very lengthy path, or will ultimately escape its gravitation and go into the interplanetary space.
- At a speed of about 28000 km / h satellite will orbit the Earth
- If the speed is reduced gravity will begin to be attracted to the satellite and it will switch to a lower orbit until it falls to Earth
- When the speed increases, the satellite will move to multiple orbits until it completely leaves the Earth's gravity and goes into space
Therefore, the aircraft we have launched horizontally at speeds of 28000 km / h will circulate around the Earth. Speed is of fundamental importance for the release of the force of hardship, and the height is needed to resolve the resistance of the atmosphere. The first Newton's law of motion says that a body that does not act is moving at a uniform speed, which means that the satellite will remain in a certain path as long as that condition is met. Of course, that's the theory. In reality, this would mean a fully symmetric Earth of the same internal mass distribution. Our planet is not a perfect ball, and the mass in it is not uniformly distributed. The pole measured for the poles is slightly smaller than the radius of the equator; Turning the Earth around its axis causes slight bulging, and thus the strength of the force increases. In addition, the centrifugal force (or, more precisely, the reciprocal value of the centripetal force) affects the inertia of the body at the equator, and the acceleration of gravity on the poles is 9,832 m / s ^ 2, while on the equator 9,78 m / s ^ 2 on the equator she loves.
In addition, irregularities in the inner structure of the Earth cause the mass change below the satellite at every point of its path. As the force of gravity - gravitationally depends on weight, it is, for that reason, a little, but continually, changing. At only one tour of the planet, the consequences will not be particularly felt, but accumulated over a longer period of time become significant. Because of this, the satellites will move away from the predicted positions, unless it is already foreseen in the budgets. The gravitational attraction decreases with the square of the distance, so the speed of circling on the further paths may be smaller. For example, a satellite that is 1600 km away from Earth must travel at speeds of 25400 km / h, while in a circular orbit, the 4000 km is flying at about 22400 km / h. And here are equal circular conditions as well as on lower paths: if the speed of the aircraft drops, it will start to fall; if it increases, it will move to a higher orbit. Since the laws of celestial mechanics are known, it is easy to calculate the phase time, defined as the period in which the satellite once traveled around the planet. Let's just neglect the fact that the Earth is also turning around its axis, that each point on its surface moves relatively to a star.
The curvature of the Earth's surface causes the perimeter to be drawn to the line connecting a point on it and the center of the planet, after 8 km being 4,9 over the ground. Outside the atmosphere, at an altitude of, say, 200 km, the satellite will continually "fall" toward the Earth.
Circuit circumference is calculated using the 2 R Pi (Pi = 3,14159) equation, where R is the circle radius, so the path that the satellite has to overcome is easy to calculate if we know the exact distance from the center of the Earth or the path radius. The required velocity of rotation in an orbit is obtained by a known amount of harder force at that height, so the rotational time will be determined by dividing the range at speed. Thus, for example, a body distanced 8045 km from the center of Earth will travel at speeds of 5,26 km / s, and for one tour of our planet it will take 9610 seconds. The extent of its path is, in fact, 50548 km, and when we divide it with 5,26 we will get 9610. Similarly, we will select a path according to one of the two required conditions: height, which depends on the speed of rotation, or the ophode time, depending on the height of the orbit.
The condition of passing over a certain area of the planet is fulfilled by planning the path or, secondly, by setting satellites to a higher altitude. It does not take much to understand how the rocket engine will change orbits as desired. But keep in mind that speed is not reduced or increased too much because in the first case it will fall on Earth, and in the second it will be removed from it forever. Changing the speed of just a few meters per second is enough for every maneuver.
At first glance it may be thought that a lower rocket engine should be used to lift at higher altitudes because the speed of rotation is smaller. True, the kinetic energy needed to reach these paths is smaller, but with potential energy is quite different. In fact, it has to be bigger, because to get the satellite to a higher orbit, it is worth investing a lot more. The total amount of energy needed to place the body in a path is proportional to the square of the characteristic velocity, where this last term is defined as the velocity in a particular orbit. Thus, for example, the rate of retention of approximately circular orbits at the height of 1600 km is about 25400 km / h. The actual energy consumption to reach this trajectory will be equal to the quadratic speed. From this station, it is clear that more paths are consumed more energy, or fuel. However, if we set up a satellite in the orbit parallel to the equator, it has some advantages.
When the body is in the universe, it is not affected by the rotation of the planet under it. But the speed of Earth rotation is very important when launching. At the equator it amounts to 1670 km / h or 0,47 km / s. Thus, for example, a satellite fired at the equator at the start of the east is helping the Earth, so the rocket must achieve a characteristic speed of only 7,44 km / s. This, of course, changes with the latitude change; at Cape Carneval the Earth's rotation speed is somewhat less (0,42 km / s), so it has to be taken into account when calculating the rate of release.
If we launch a satellite in a polar path, where the northern and southern geographic poles of the Earth will pass, the rocket will not support the rotation of the planet, and therefore with its own power it must reach a speed of 7,91 km / s, so-called. the first cosmic speed. If we want to send the spacecraft to the west, in the retrograde path, the rocket will have to achieve additional 7,91 km / s beyond the 0,47 km / h above, which is needed to overcome the rotation of the planet in the opposite direction, ie a total of 8,38 km / s. It is quite clear that the situation with the increasing of the latitude becomes ever more difficult.
ORBIT TYPES AND CHARACTERISTICS
According to the form of the orbit can be circular, when the satellite at each point of its path is equidistant from the center of the Earth. If the velocity of the satellite rotation on a part of the path is greater or smaller than the first orbital velocity, the consequence is elliptical
orbit, when the orbit is on one side closer to the center of the Earth than the other.
The lowest and highest point are the first two parameters needed to determine the path around the Earth. Since neither theoretical can be the perfect circle, the satellite travels through the ellipsis with one of the focal points in the center of the planet. The point, when the elliptical orbit of the satellite is closest to the Earth's center is called perigeeWhile the point of maximum distance apogee. Other important elements of orbit satellites are period and inclination. Period (during the tour)
is the time for which the satellite once traveled around the Earth and returned to the starting point. Inclination (tilt) angle, which makes orbit satellites to the equatorial plane in the direction of rotation of the Earth. If the satellite is orbiting the Earth just above the equator, has an inclination 0 °, and its orbit is then equatorial. If the orbit has an inclination of 90 °, the satellite travels over the north and south poles, so that orbit is called polar. Considering that the Earth is spinning around its own axis, the satellite in a few days covers the entire surface of the earth, including the poles. Also inclination of, say 50 degrees means that the satellite is traveling around the Earth with a trace - point vertically below it - that overwrites all latitudes between 50. Southern and Northern parallels; This path led him to the southern coast of England in the northern hemisphere, and the Falkland Islands in the south. Sometimes, though, to describe the path to be used another coordinate system.
Earth spins around the Sun tilted for 23,45 degrees toward its path. The planet does not change direction, and at one point the sun is closer to the south, while in six months the situation is reversed. The point crosses the Earth's path and plane of the equator are called nodes. Our planet passes through them during the spring or autumn equinox. The plane of the orbit of the satellite can be expressed according to these points. But for what purpose? It should be remembered that due to the constant position of the planet's axis toward the plane path around the Sun, and thus toward it, the plane of the orbits of the satellite, expressed at the nodes, also shows an angle to the Sun.
From all of this we will see that another parameter is needed for the exact path determination. This is the angle between the main axis of the elliptical orbit and the line of the plane plane of the Earth's path and equator. That angle is called argument perigeja. As the main axis of the elliptical orbit can be directed anywhere, this parameter is set right in our coordinate system.
Given the size of the orbit of the difference between: low, medium and geostationary Earth orbit. Niska
The Earth's orbit is at altitudes between 100 and 1000 km (some sources indicate the upper limit of low orbit at 500 and 800 km). Low-orbit satellites are closer to Earth, and have a higher orbital speed and a shorter period (about 90 minutes). There orbit, among other things, is used by military observation satellites. For secondary
The Earth's orbit is rated as 1000 to 35800 km. Middle Earth orbit at altitudes between 19000 and 20000 km use navigational satellites. Geostationary (geosynchronous) orbit at an altitude 35800 km with an inclination of 0 ° (the equatorial plane), the orbital velocity at that height is equal to the speed of rotation of the Earth (3 m / s), the period is thus slightly less than 24 hours, a satellite is always above the same point of the earth's surface. In this orbit are communication satellites, some military satellites for early warning and for collecting signals intelligence. satellites with high elliptical the orbit around the Earth circles to varying heights. Examples of such orbits are some types of geosynchronous orbits, geostationary transfer orbit (the most energy efficient way of introducing satellites into a geostationary orbit), and Molnija orbit. The latter, with a perigee between the 500 and 1500 km, apogee about 40000 km and an inclination of about 64 °, allows telecommunication connections over the northern latitudes, which can not be covered from geostationary orbit. It is named after Soviet communication satellites Molnija, Who have used such orbit.
The orbits can share with regard to some other features.
Sunny synchronous orbit (heliosinkrona) the orbit in which the satellite's orbital plane is always in the same angle with respect to the direction of the sun. This requires a polar orbit with an inclination of more than 90 °. This orbit allows the observation of the Earth's surface at the same local time, and therefore the same angle of illumination from the Sun, but they, among others, used military satellites for photographic reconnaissance, because of the photos on which the shadows are always equal, easier to detect changes due the previous photos.
To sum up: the area over which the satellite flies depends on the slope of the path; height above the Earth's surface is determined by the perigee and apogee - the lowest and highest point of the orbit, always from opposite sides of the globe; the energy needed to reach higher orbits higher than those for entering the lower, although the speed of entering into them falling from a height. Orbital period increases with increasing distance from Earth satellites. It follows that at a certain height to be the same time period of rotation of the planet. When orbital plane lies in the equatorial, such orbits are called stationary. When these two planes do not coincide, we are talking about synchronous orbit (because the orbital time as the rotation of the planet); in this case, the satellite will render the sky eight, with the endpoint trajectory as much in the south and north as far as is its inclination to the equator.
The advantage of the stationary orbit is that the satellite placed on it for the observer on Earth looks stationary, as if the 24 hour of the day is connected to one point of the sky. The only difficulty is the distance (35880 km), which means that a lot of energy is needed to get to it.
The satellite is composed of two basic parts - the platform and the cargo. Purpose platforms
the support load and ensure its normal operation. Burden depends on the performance of the task for which the satellite is made and needs support from the platform. The platform includes a number of subsystems:
Drive subsystem so it includes an electric or chemical engine that sets the satellite in its permanent position as well as small propulsion engines by which the satellite maintains its orbiting path. The satellite ejected from the orbit of gravitational and magnetic forces, and the sun's wind. In this case, the propulsion engines are included, which satellites return to its proper orbit.
Subsystem supply of electricity
produces electricity from solar cells, which are on the outside of the satellite, and is stored in batteries that provide energy when the sun does not shed on solar cells. Electricity is needed for the operation of various subsystems and satellite loads. Some satellites (eg Russian satellites for US-A radar monitoring) have provided nuclear power to the power supply.
Structural subsystem serve to relieve the mechanical stress in the launch, and acts as a solid, stable base to which they are attached other parts of the satellite.
Subsystem of thermal monitoring
Keeps active parts of the satellite cool enough for proper operation. This achieves the heat transmitted by the satellite in the work to the universe.
Subsystem for position monitoring
ensures that the satellite is constantly in the right path and is properly aligned. When the satellite comes out of the correct position, the subsystem for position monitoring includes a drive subsystem that returns the satellite to the correct position.
Subsystem for telemetry and management
enables communication with the earth observation stations from which the proper operation of the satellite is monitored.
CLASSIFICATION OF SATELLITE
Satellites can be classified according to different criteria: by type of orbit, by weight, by purpose, etc. Due to mass, different sources classify satellites differently - the European Space Agency (ESA) divides satellites into large satellites
with mass over 1000 kg, small satellites
with a mass between 500 and 1000 kg, minisatelite
between 100 and 500 kg, microsatellites
between the 10 and 100 kg and nano pikosatelite
with a mass below 10 kg.
Due to distinguish between primary users commercial
satellites i institutional satellites, although institutional users (eg. military) use commercial satellites for certain purposes and vice versa.
Military satellites are mostly sorted into the following groups: satellites for early warning and assessment of attacks, survey and monitoring satellites, communication satellites, navigation satellites,
geodetic satellites i meteorological satellites.
To this can be added even battle satellites, which were tested for protusatelitske tasks. US turn today in the framework of the missile defense develops satellite SBL (Space Based Laser). Agreement on exploration and use of outer space from 1967. prohibits the installation of nuclear and other weapons of mass destruction in the universe.