Satellite launch process. How do satellites work? Orbital speed and height
The launch of the satellite into space was marked by a new era and became a breakthrough in the field of technology and astronautics. The need to create a satellite was determined at the beginning of the twentieth century. However, from the very beginning, on the way to launching a satellite into outer space, there were many problems that the best engineers and scientists worked on. These problems were associated with the need to create engines that can work in the harshest conditions and at the same time, they must be unusually powerful. Also, problems were associated with the correct determination of the satellite's trajectory.
So, Soviet scientists solved the tasks, and on October 4, 1957, an artificial satellite was successfully launched in the USSR, the movement of which was watched by the whole world. This event became a world breakthrough and marked a new stage, both in science in general and in the whole world.
Live broadcast of the Soyuz-Progress launch (mission to the ISS)
Tasks solved by the satellite
The tasks solved by launching a satellite can be defined as the following:
1. Study of the climate;
Everyone knows the impact climate has on agriculture and military infrastructure. Thanks to satellites, it is possible to predict the appearance of destructive elements, to avoid a large number of victims.
2. Study of meteorites;
In outer space there is a huge number of meteorites, the weight of which reaches several thousand tons. Meteorites can be dangerous not only for satellites, spacecraft, but also for people. If during the flight of a meteorite the friction force is small, then the unburned part is able to reach the Earth. The speed range of meteorites reaches from 1220 m/s to 61000 m/s.
3. Application of television broadcasting;
At present, the role of television is great. In 1962, the first television broadcaster was launched, thanks to which the world first saw video footage across the Atlantic within a few minutes.
4. GPS system.
The GPS system plays a huge role in almost every area of our lives. GPS is divided into civil and military. It is an electromagnetic signal emitted in the radio wave portion of the spectrum by an antenna installed on each of the satellites. Consists of 24 satellites, which are in place of the orbit at an altitude of 20200 km. The time of revolution around the Earth is 12 hours.
Telecommunication satellite "Arabsat-5B"
Soyuz launch
Launching satellites and getting them into orbit
To begin with, it is important to indicate the flight path of the satellite. At first glance, it seems that it is more logical to launch a rocket perpendicularly (along the shortest distance to the target), however, this type of launch turns out to be unprofitable, both from an engineering point of view and from an economic point of view. A satellite launched vertically is affected by the forces of gravity of the Earth, which significantly remove it from the intended trajectory, and the thrust force becomes equal to the force of gravity of the Earth.
To avoid the fall of the satellite, first, it is launched vertically so that it can overcome the elastic layers of the atmosphere, such a flight continues for only 20 km. The satellite then tilts with the help of the autopilot and moves in a horizontal direction towards the orbit.
In addition, the task of engineers is to calculate the flight path in such a way that the speed spent on overcoming the atmospheric layers, as well as on the cost of fuel, is only a few percent of the characteristic speed.
It is also important in which direction to launch the satellite. When a rocket is launched in the direction of the Earth's rotation, there is an increase in speed, which depends on the location of the launch. For example, at the equator it is maximum and is 403 m/s.
Satellite orbits are either circular or elliptical. An elliptical orbit will be in the event that the speed of the rocket is higher than the circumferential one. The closest point is called perigee, and the farthest point is called apogee.
The launch of a rocket with a satellite is carried out in several stages. When the engine of the first stage stops working, the angle of inclination of the launch vehicle will be 45 degrees, at an altitude of 58 km, then it will be separated. The engines of the second stage are included in the work, with an increase in the angle of inclination. Further, the second stage separates at an altitude of 225 km. Then, by inertia, the rocket reaches a height of 480 km and ends up at a point located at a distance of 1125 km from the start. Then the third stage engines start to work.
The return of the satellite to earth
The return of a satellite to Earth is accompanied by some braking problems. Braking can be done in two ways:
- Thanks to the resistance of the atmosphere. The speed of a satellite entering the upper atmosphere will decrease, but due to its aerodynamic shape, it will ricochet back into outer space. After that, the satellite will reduce its speed and enter deeper into the atmosphere. This will repeat itself several times. After slowing down, the satellite will descend using retractable wings.
- Automatic rocket engine. The rocket engine must be directed in the direction opposite to the movement of the artificial satellite. The advantage of this method is that the braking speed can be adjusted.
Conclusion
So, in just half a century, satellites entered human life. Their participation helps to explore new outer spaces. Satellite, as a means of uninterrupted communication, helps to make people's daily lives convenient. Paving the way to outer space, they help make our life the way it is now.
If a member of the ISS crew who went into outer space took a small box with him and then threw it into space, this does not mean at all that a general cleaning is taking place at the station. Most likely, a very small satellite set off on its orbital path. The launch of nanosatellites has become today, if not cheap, then already a relatively affordable pleasure, and students and even amateurs of do-it-yourself designers have joined in space exploration.
Oleg Makarov
A large serious satellite, for example, one that maintains the GPS system, weighs one and a half to two tons, and the cost of its manufacture and launch into orbit exceeds $100 million. The order of prices is cosmic, and there’s nothing to be done about it - even a kilogram of clay sent into space will become gold almost without exaggeration. But if there are not so many of these kilograms of anything, then the launch of a spacecraft can become a much more budgetary event.
The world's first artificial Earth satellite, although it contained nothing but a radio transmitter, weighed a solid 83.6 kg. Since then, electronics have stepped forward, miniaturized by orders of magnitude, and now satellites, weighing from several kilograms to several grams, can, as it turns out, be quite functional. As soon as this became clear, space exploration ceased to be the exclusive prerogative of government departments and huge rocket and space corporations: the time has come for student and amateur satellite construction, along with which the second wave of space romance is gradually rising. And this wave also did not bypass Russia.
CubeSat is a nanosatellite developed by California Polytechnic University and Stanford University specifically for student and amateur experiments in space. It measures 10 x 10 x 10 cm and weighs 1.3 kg. These days, you can buy a kit for building a nanosatellite at the store.
Found each other
Was it possible to imagine 20-40 years ago that the creation of an orbital spacecraft would become the topic of student work? Today, students of the department of designing electronic computing facilities of the Southwestern State University (Kursk) are creating equipment for sending into orbit. “We are not the only university in Russia where satellites are being developed,” says Associate Professor Valeryan Pikkiev, head of the Center for the Development of Small Spacecraft. - There are devices made at the Moscow State Technical University. Bauman, Moscow State University, Military Space Academy. A.F. Mozhaisky, however, these are already serious professional works, in which the entire scientific potential of our leading universities is involved. We have both the equipment and the experiments that will be carried out with the help of this equipment - everything is invented by the students themselves.
The Department of Designing Electronic Computing Means of SWSU was established in 1965 and was engaged in the development of various electronics for domestic enterprises, including military devices. Among them were vacuum gauges - devices for measuring the concentration of particles in rarefied media. These devices aroused interest from the enterprises of the rocket and space industry - NPO them. Lavochkin and RSC Energia.
Flying in an old suit
By this time, Energia already had its own program for the creation and launch of small satellites. “It all started 15 years ago,” says RSC Energia Leading Specialist Sergey Samburov. - In 1997, cosmonaut Valery Polyakov proposed to celebrate the 40th anniversary of the first satellite by launching its smaller copy. The proposal was accepted, and schoolchildren from Kabardino-Balkaria and the French Reunion took part (albeit symbolically) in the creation of the device. The satellite not only looked like its prototype, but also reproduced its “stuffing”, including the “beep-beep-beep” signal transmitter. Of course, a separate carrier was not used for this apparatus - it was delivered by the Progress spacecraft to the Mir orbital station, and there, during a planned spacewalk, it was “thrown” into outer space.
The launch of a smaller copy of the first satellite caused a real stir among radio amateurs around the world, especially among those who recalled their youth and the radio signal of the 1957 satellite with nostalgia. It was decided to continue the theme, and the next year another amateur radio satellite was launched, which broadcast songs and addressed the audience of planet Earth in different languages. The technology for launching satellites from orbital stations was improved, and in 2002 RSC Energia, together with the Space Research Institute, sent a small Hummingbird apparatus with scientific equipment into orbit. They launched it like this: when the Progress undocked from the ISS, its hatch remained open. A container was installed inside the ship, which, when the holding cord was burned out by a squib, literally fired a satellite.
And in 2006, RSC Energia, together with representatives of the American amateur radio corporation AMSAT, gave birth to one of the most original projects in the history of space exploration. It was decided to make a new amateur radio satellite on the basis of the Orlan-M spacesuit that had served its purpose, which was used as a platform for mounting the equipment delivered to the ISS. There was no scientific equipment on the Radioskaf-1 satellite (aka SuitSat-1) - only antennas (mounted on a helmet), a radio station, a digitolker unit for broadcasting sound programs, two cameras (digital and film) and a battery. It is interesting that the standard battery from the suit did not fit - it is designed for a small number of charge-discharge cycles, and a satellite experiencing temperature drops from minus 100 to plus 100 degrees Celsius in orbit would use up the resource of such a device very quickly. Moreover, Radioskaf-1 did not have solar panels and relied only on the battery life. In February, ISS cosmonaut Valery Tokarev, having gone into outer space, pushed his old spacesuit with a new filling away from him, and the satellite went on a two-week mission.
Skaf and wardrobe
Despite all the exoticism of the project, the suit turned out to be very interesting platform for small satellites. Firstly, it does not need to be delivered to the ISS, since it has already been delivered there. Secondly, the elongated shape opens up the possibility of passive stabilization due to the uneven distribution of the load (the heavier part will always “gravitate” towards the Earth, and the satellite will not rotate around its axis). Finally, the suit has a cylinder that can contain oxygen or other gas at a pressure of 100 atm. This can be used to deploy satellite inflatables.
However, while in RSC Energia the Radioskaf-2 plan was ripening - again on the basis of a spacesuit, there was a problem. The next old spacesuit, on which they wanted to mount a satellite, had to be thrown out of the ISS, without waiting for the equipment for the second satellite to be ready: space is in short supply. “We couldn’t wait another five years for the new suit to replace the old one to grow old,” says Sergey Samburov. “That's why, as we joke, we had to make a Radio Cabinet instead of the Radioscaphe, that is, a structure in the form of a rectangular parallelepiped with dimensions of 500 x 500 x 300 mm. The project was timed to coincide with the half-century anniversary of Gagarin's flight, and the device itself was named "Kedr" in honor of the call sign of the first cosmonaut on the planet. He also had another name - ARISSat-1, after the name of the international association of radio amateurs working with satellites launched from the ISS. The satellite was made in international cooperation, but also for the first time, the department of designing electronic computing systems of the SWGU, which became a full partner of the Radioskaf project in 2010, took an active part in its creation. This is where the scientific equipment designed by Kursk students came in handy - the same vacuum gauges. Of course, the creators of "Kedr" did not forget about radio amateurs, for whom broadcasting of messages in different languages of the world was provided. The satellite was sent into orbit from the ISS on August 3, 2011, and it successfully completed its mission, in particular, by measuring the density of particles in a vacuum in orbits of different altitudes.
Nanosatellite over the Andes
“We continue to work on the Radioskaf program in cooperation with RSC Energia, which partially finances our activities and takes on the launch of student and amateur radio devices as part of its own experimental programs,” says Valeryan Pikkiev. - Another satellite - "Chaski-1" - we are doing together with students of the Technical University from Peru. It will be a satellite in the CubeSat nanoformat, which is popular in the world (a cube with sides of 10 cm, weight 1.3 kg). There will be no scientific equipment on the spacecraft, but we intend to test a specially designed framework that makes it possible to passively stabilize the satellite along the lines of the Earth's magnetic field. In addition, cameras with a low resolution will be installed on Chasky-1. They will make it possible to take photos of the earth's surface (two cameras in the visible spectrum, two infrared), the image from them will be available to radio amateurs. We will also work out the command line at a frequency of 144, 430 MHz. All this will allow us to launch scientific equipment in the next joint satellite, in particular, a new generation of our vacuum gauges, which are now capable of recording not only the concentration of particles, but also determining their nature.”
Where to throw - that is the question
Of course, nanosatellites can be launched in different ways. There is a variant of placing a cassette with satellites between the second and third stages of a rocket that puts, say, a heavy communications satellite into orbit. Two-stage rocket-aircraft launch concepts are being developed, similar to Virgin Galactic's LauncherOne project. However, as long as the ISS exists, it will probably be the most reliable platform for such launches, and for this purpose it is used by both Russian cosmonauts and US and Japanese astronauts. However, even here the human factor can be minimized.
The history of Russian student and amateur radio satellite construction began in 1996, when, on the initiative of cosmonaut Valery Polyakov, a small copy of the world's first satellite was launched from the Mir station. The flight aroused great interest among radio amateurs around the world.
“Now, as part of our program, we are making a cannon to launch small satellites,” says Sergey Samburov. - It will be a box the size of a shoe, and inside there will be a spring that, on command, will push the satellite out at the right time. And this is not so simple in fact, since the device must be launched in the right direction, while giving it rotation. If you simply throw the satellite away from the station, then, according to the laws of ballistics, it will return to the station. It is necessary to throw along the motion vector or against the vector, but it is impossible along the vector, because then the satellite will rise to a higher orbit and fly over the station, and if the station corrects the orbit, a collision may occur. The probability is small, but it exists. It is necessary to throw against the vector, and then the device goes under the station, and then overtakes it and will never collide with it again. The technique of manually launching a satellite is rather complicated, and astronauts work it out on Earth during training in a hydro pool. If an automatic device for shooting satellites is created, then the crew will need to do exactly two things: pull the device out into space, and then, upon returning to the station, give the launch command.
Helpful and safe
Today RSC Energia has created a special subdivision dealing with small spacecraft. The main task of its activity is educational. “Students who took part in the creation of spacecraft during their studies will come to us as specialists with experience in practical design. This is very important for us,” says Sergey Samburov. “Besides, don't think that small satellites are only good for learning and hobbies. On them, you can work out the technologies of movement and maneuvering, stabilization systems, the operation of new devices for quite serious tasks. And with the relatively low cost of these devices, the cost of an error is also lower, which otherwise can destroy a large and expensive satellite or probe.
Only the last question remains: will the global fascination with nanosatellites become another factor in the pollution of near-Earth space - after all, there is already enough space debris in orbits. “There is nothing to worry about,” explains Valeryan Pikkiev. - Amateur satellites do not belong to orbital centenarians. From the height of the ISS (about 400 km), our satellites fly to the dense layers of the atmosphere for only half a year. In addition, we make them from materials that easily burn out from friction with the air, so that none of our brainchildren will ever fall on anyone's head.
In January 2018, the first successful illegal launch of a satellite into space took place in the history of mankind, or rather four small experimental orbital drones at once.
The American company Swarm Technologies managed to launch illegal launches of satellites called SpaceBee-1, 2, 3 and 4 into space, which agreed with Indian specialists that they would additionally load four book-sized drones onto the Polar Satellite Launch Vehicle launch vehicle along with three dozen other satellites.
Back in the 2000s, the Indian Space Research Organization (ISRO) set out to launch hundreds of satellites into orbit for the needs of the state and business, and achieved notable success in this direction, so it was not difficult for them to “grab” with them a few commercial devices for them.
According to open data, the last successful launch of a PSLV rocket with satellites of India, the USA, Canada, Finland, France and South Korea took place on January 12, 2018.
It was only after the Swarm Technologies satellites were in space that US regulators raised the alarm: it is difficult to track small objects in orbit normally, but at the same time they pose a mortal danger to any device or ship that they might collide with.
The legal conflict with Swarm Technologies is that it is not India that is responsible for its actions in space, but the United States, where this company is registered. The scientific community is especially indignant about this, which demands to figure out how a group of private individuals, secretly from the state, put their satellites into orbit at a time when even the Pentagon is obliged to strictly report on such things, with rare exceptions.
According to another network publication IEEE Spectrum, the SpaceBee-1, 2, 3 and 4 satellites are designed for "two-way satellite communications and data transmission from the United States." It is known about Swarm Technologies itself that it “grew” from a well-known in professional circles startup Silicon Valley in California.
The company was founded two years ago by Canadian aerospace engineer, former NASA and Google employee Sarah Spangelo and University of Michigan professor and independent developer Benjamin Longmyer, who sold his previous company Aether Industries to Apple Corporation.
The company has only five employees, and this whole team is working on a system that will allow businesses to use the power of satellite Internet to create a single network of ships, trucks, cars, agricultural equipment, and anything else that can be assigned an IP address. The Internet to all these devices anywhere in the world should be distributed by SpaceBee-1, 2, 3 and 4, as well as their future counterparts.
Presumably, Swarm Technologies needed its own satellites in order to show potential investors how cheap satellite Internet can be with the right approach to business as part of the Internet of Things concept.
Everything would be fine, but in December 2017, the US Federal Communications Commission officially rejected the company's application to launch experimental satellites for security reasons, after which the startups simply ignored this decision, thereby creating a dangerous precedent that could turn into a disaster or the death of astronauts in the future. Whether enterprising engineers will be punished or whether they will be able to complete work on their project is still unknown.
sources
Both private companies and non-profit organizations, and individual enthusiasts are increasingly raising money for space projects through crowdfunding platforms. Let's talk about the most interesting ideas.
See traces of the Apollo
The question of whether the Americans were on the moon worries a huge number of people around the world. And the Russians, especially.
Four years ago, a well-known popularizer of astronautics, blogger Vitaly Egorov offered to get an answer to the "damned" question in the most direct way - to send a satellite into the orbit of the moon, which would photograph the landing sites of the Apollos. Let us recall that there were six of them in total, and in the vicinity there should be many traces of astronauts, artifacts left by them (up to moon vehicles), and simply garbage.
“Now private and student satellites are launched into orbit almost every month,” said Vitaly Yegorov at a recent presentation of the project, held at the Museum of Cosmonautics. We decided to take a swing at something more difficult. And this is the Moon. As you know, society is concerned about two questions: do aliens exist and whether the Americans were on the moon. I personally have no doubt that the Americans were on the moon. With aliens it is not clear, but we postponed them for later, but for now we decided to concentrate on a more realistic goal.
In October 2015, Yegorov announced a fundraiser for the construction of a "people's" microsatellite. Then, in less than three days, the blogger and his team raised over a million rubles. The first version of the spacecraft was very modest - with a small engine and solar panels. But then, having studied all the nuances of the upcoming mission, the project participants were forced to increase the mass of the satellite, add a full-fledged liquid engine and a powerful antenna to it. The probe will be equipped with photographic equipment that will take very clear pictures: each pixel will correspond to 25 cm of the surface of the moon.
Since 2015, the device has been simplified in every possible way, and its current version is already the fourth. But to build a satellite, funds will be needed about a thousand times more than was raised through crowdfunding. Participants rely on various funding options - private sponsors, advertising contracts, as well as assistance from society, business and the state.
“If a potential sponsor comes to us today and donates a truck filled with money, we will be able to prepare the device and deliver it to Baikonur or Vostochny in the next three years,” said Vitaly Egorov. “When it launches will depend on what missiles are available. But everyone will be watching this launch, because there are enough people who believe in the lunar conspiracy.”
What are they throwing off in the West?
The first space project of the English-language crowdfunding platform Kickstarter was an attempt made nine years ago to launch a very large balloon into the atmosphere to photograph the Earth from a height of 40 km (this is already considered near space). Managed to collect 296 dollars.
The most noisy fundraising campaign on the same platform is Arkyd-100. This is a "space telescope for everyone" project. It was announced in 2013 by Planetary Resources, which intended to start mining on asteroids. In total, more than $1.5 million was raised. Donors were promised "space selfies" aboard the telescope and shooting astronomical objects if desired. However, in 2016 it was announced that the launch of the telescope would not take place. The money should have been returned.
10 fantastic pictures of the Hubble telescope
Another company is about to send a space probe to the Moon to drill into the rocks at its South Pole. Over a million dollars have already been raised. And the not-for-profit Planetary Society spent 10 years raising funds for the mission of a tiny satellite with a solar sail, LightSail. The goal of the project was simple - to show that the creation of such a spacecraft is possible in principle. Its cost was estimated at 1.8 million dollars, and this money, in the end, was collected. On June 25, 2019, the solar sailboat went into orbit.
Other space projects that have received funding from the Internet community include SkyCube (an ultra-small satellite that "inflates" a shiny balloon visible from Earth), KickSat (in orbit, it should release a swarm of tiny satellites the size of a postage stamp) and Plasma Jet Electric Thrusters (a plasma engine that will find applications in future astronautics).
... and for what - with us?
In Russia, they also raised money to launch a stratospheric probe. The author of the idea is a lifeguard and a photographer Denis Efremov. First, he and a friend sent a video camera into the stratosphere in honor of the anniversary of the flight. Yuri Gagarin. And then he announced the collection of funds for the launch of the stratospheric balloon. Having reached a critical size at high altitude, this ball should burst, and the platform with the equipment should parachute down.
“My goal is to arrange a children's science festival based on a large educational program- Denis Efremov reported. - The core of the project is launches into near space at a height of up to 40 km. To send something of your own into space, to follow the flight, to look for a place to land, and to pick up again what has been "there" - this is a miracle! Children are encouraged to be interested in science. They see with their own eyes and can figure out how to apply knowledge in practice. And finally, launching and searching for a platform in nature is a real adventure that will pull any student out of social networks!”
The project became successful. It was planned to collect 140 thousand rubles, as a result, they managed to attract 155 thousand rubles.
In 2014, a group of enthusiasts created the Your Sector of Space community, which proved for the first time in practice that space enthusiasts in Russia can launch their own spacecraft into orbit. They became the Mayak satellite. Funds were collected by crowdfunding for two campaigns, in 2014 and 2016. In total, they collected about 2.5 million rubles. About 1 million rubles were spent directly on the creation of a flight copy of the device, its backup and their testing.
“We have shown that it is possible to invent a satellite together with friends, without huge factories and complex laboratories, to build it and launch it into real space,” the project manager shares his impressions. Alexander Shaenko, engineer and candidate of technical sciences. “The idea was to create a bright glowing object visible to the naked eye.”
It was decided to equip the satellite with a solar reflector in the form of a metalized film pyramid, which should turn around after entering orbit. "Mayak" was supposed to be the brightest twinkling star in the night sky for almost a month. The device was launched on July 14, 2017 from the Baikonur Cosmodrome and successfully launched into orbit simultaneously with 72 other satellites. Unfortunately, the reflector never opened up. Together with Mayak, another 9 satellites launched on a launch vehicle failed.
The second project of the Your Sector of Space community was a photobioreactor for growing microscopic green algae. They called it 435nm. In the future, on the basis of the created installation, it is planned to build a space life support system and test it in orbital flight.
“Russia, along with other countries, is participating in the Martian race, and we are interested in our country emerging victorious from it,” says Alexander Shaenko. - One of the important parts of the project for the development of the Red Planet is the development of spacecraft, and they need life support technologies. That is why the 435nm bioreactor project was born in our community.”
Fundraising was completed in March 2018, the team managed to raise 407 thousand rubles. A prototype was created and tested. It is noteworthy that the technology will find application not only in space, but also on Earth. Such photobioreactors can be used to clean wastewater or air, produce raw materials for biofuels and other practical tasks.
We continue our series of articles "Everything about everything." This time we'll talk about satellites.
Not so long ago, satellites were exotic and top-secret devices. They were mainly used for military purposes, navigation and espionage. Now they are an integral part of modern life. We can see them in weather forecasts, television, and even regular phone calls. Satellites also often play a supporting role in some areas:
- Some newspapers and magazines are fast because they send materials to different printers via satellite to speed up local distribution.
- Before transmitting the signal over the wire to cable television users, provider companies use satellites to transmit the signal.
- Recently, geolocation capabilities provided by GPS and GLONASS systems have gained unprecedented popularity. With the help of them, we can quickly and accurately get to the required month.
- The goods we buy are delivered by the supplier's manufacturers more efficiently thanks to logistics using geolocation using GPS and GLONASS.
- Radio beacons from downed planes and ships in distress send signals via satellite to rescue teams.
What is a satellite?
A satellite in general is an object that revolves around a planet in a circular or elliptical orbit. For example, the Moon is a natural natural satellite of the Earth, but there are many more man-made (artificial) satellites that are usually closer to the Earth.The path followed by a satellite is called an orbit. The point of the orbit farthest from the Earth is called the apogee, the nearest point is called the perigee.
Artificial satellites are not mass-produced products. Most of the satellites were specially made to perform their intended function. The exceptions are GPS / GLONASS satellites (of which there are about 20 copies for each of the systems) and Iridium system satellites (of which there are more than 60 copies, they are used to transmit voice communications).
There are also about 23,000 objects that are space junk. These objects are large enough to be picked up by radar. They either accidentally ended up in orbit, or they have exhausted their usefulness. The exact number depends on who is counting. A payload that has fallen into the wrong orbit, satellites that have run out of batteries, and also the remnants of rocket upper stages - all this is space debris. For example, this online catalog of satellites has about 26,000 objects.
Although any object in Earth orbit can generally be called a satellite, the term "satellite" is usually used to describe a useful object placed in orbit to perform some important task. We often hear about weather satellites, communications satellites, and scientific satellites.
Whose satellite was the first to orbit the Earth?
In general, the Moon should rightly be considered the very first satellite of the Earth :)
To our common joy, the first artificial Earth satellite was Sputnik 1, launched by the Soviet Union on October 4, 1957. Hurrah, comrades!
However, due to the strict secrecy that existed at the time, there are no publicly available photographs of that famous launch. Sputnik 1 was 23 inches (58 centimeters) long, weighed 184 pounds (83 kilograms), and was shaped like a metal ball. However, for that time it was an important achievement. The contents of the satellite by modern standards seems meager:
- Thermometer
- Battery
- Radio transmitter - changed the tone of its sounds according to the thermometer
- Nitrogen - created pressure inside the satellite
After 92 days, gravity did its job and Sputnik 1 burned up in the Earth's atmosphere. Thirty days after the launch of Sputnik 1, the dog Laika flew on a half-ton satellite with air. This satellite burned up in the atmosphere in April 1958.
Sputnik 1 is a good example of how simple a satellite can be. As we will see next, modern satellites are much more complex, but the basic idea is simple.
How are satellites launched into orbit?
All modern satellites are put into orbit by rockets. Some were delivered into orbit in the cargo hold of the shuttles. Several countries and even commercial companies have the ability to launch satellites into orbit, and it is now not unusual to deliver a satellite weighing several tons into orbit.
For most scheduled launches, the rocket is typically positioned vertically upwards. This allows it to pass through the dense layers of the atmosphere quickly and with minimal fuel consumption.
After the missile is launched vertically upwards, the missile control system uses the inertial guidance system to control the missile's nozzles and directs it to the calculated trajectory. In most cases, the rocket is heading east because the Earth itself is spinning east, allowing the rocket to get "free" acceleration. The strength of this "free" acceleration depends on the speed of rotation of the Earth at the launch site. The greatest acceleration is at the equator, where the distance around the Earth is greatest, and consequently the rotation speed too.
How big is the acceleration in an equatorial launch? For a rough estimate, we can calculate the length of the Earth's equator by multiplying its diameter by pi (3.141592654...). The diameter of the earth is approximately 12,753 kilometers. Multiplying by pi, we get a circumference of about 40,065 kilometers. To pass the entire circle in 24 hours, a point on the surface of the Earth must move at a speed of 1,669 km / h. A launch from Baikonur in Kazakhstan does not give such a large acceleration from the rotation of the Earth. The speed of rotation of the Earth in the Baikonur region is about 1,134 km/h, and in the Plesetsk region it is generally 760 km/h. Thus launching from the equator gives more "free" acceleration. In general, the Earth is not quite the shape of a sphere - it is flattened. Therefore, our estimate of the Earth's circumference is somewhat inaccurate.
But wait, you say, if rockets can reach speeds of thousands of kilometers per hour, then what will give a small boost? The answer is that rockets, along with their fuel and payload, are very heavy. For example, according to Wikipedia, the proton launch vehicle has a launch weight of 705 tons. To accelerate such a mass even up to 1,134 km/h requires a huge amount of energy, and therefore a large amount of fuel. Therefore, launching from the equator provides tangible benefits.
When the rocket reaches very thin air at an altitude of about 193 kilometers, the rocket's control system turns on small motors, enough to turn the rocket into a horizontal position. The satellite then separates from the rocket. The rocket then turns on the engines again to provide some separation between the rocket and the satellite.
Inertial Guidance System
The rocket must be controlled very precisely to put the satellite into the required orbit, and mistakes in this matter are very expensive (remember the failures of Roskosmos with GLONASS satellites or the Phobos-Grunt probe, which ended up in the wrong orbit, which they should have). Inertial guidance systems inside missiles make such control possible. Such a system determines the exact position of the missile and its direction by measuring the acceleration of the missile using gyroscopes and accelerometers. Located in a gimbal, the axes of the gyroscope always point in the same direction. In addition, the gyroscope platform contains accelerometers that measure acceleration in three different axes. If the control system knows the initial location of the rocket at the time of launch and acceleration at the time of flight, it will be able to calculate the position of the rocket and its orientation in space.Orbital speed and height
The rocket must accelerate to a speed of at least 40,320 km/h (11.2 km/s) to fully exit Earth's gravity and travel into space. This speed is called the second cosmic speed and it is different for different celestial bodies.
The second space velocity of the earth is much greater than the speed required to put satellites into orbit. Satellites don't need to get out of the Earth's gravity, they need to balance against it. Orbital speed is the speed required to achieve a balance between the gravitational pull and the inertia of the satellite. On average, this speed is 27,359 km / h at an altitude of approximately 242 kilometers. Without gravity, the inertia of the satellite would push it out into space. Although even if gravity is present, then too high a satellite speed will take it out of Earth's orbit into outer space. On the other hand, if the satellite moves slowly, then under the influence of gravity it will fall back to Earth. If the satellite has a certain correct speed, then gravity will be balanced by the inertia of the satellite, the Earth's gravity will be sufficient for the satellite to move in a circular or elliptical orbit, and not fly into space in a straight line.
The orbital speed of a satellite depends on the altitude at which it is located. The closer to the Earth, the greater the required speed. At an altitude of 200 kilometers, the required orbital speed is about 27,400 km/h. To maintain an orbit of 35,786 km, a satellite must orbit at a speed of about 11,300 km/h. This orbital speed will allow the satellite to make one revolution around the Earth in 24 hours. Since the Earth itself rotates at a rate of 24 hours, a satellite at an altitude of 35,786 km will remain strictly above the same point on the Earth's surface. Such an orbit is called "geostationary". Geostationary orbits are ideal for weather and communications satellites.
The Moon has an "altitude" relative to the Earth of 384,400 kilometers, and its orbital speed is 3,700 km/h. It makes a complete revolution in its orbit in 27.322 days. Note that its orbital speed is lower because it is farther away than artificial satellites.
In general, the higher the orbit, the longer the satellite can stay in orbit. At low altitudes, the satellite enters the layers of the atmosphere, which creates friction. Friction takes away part of the energy of the satellite's motion, and it falls into denser layers and, falling to the Earth, burns up in the atmosphere. At high altitudes, where there is almost a vacuum, friction does not occur and the satellite can remain in orbit for centuries (take the Moon, for example).
Satellites tend to have an elliptical orbit at first. Ground control stations use the satellite's small jet engines to correct the orbit. The goal is to make the orbit as circular as possible. Turning on the jet engine at the apogee of the orbit (the most distant point), and applying a force in the direction of flight, shifts the perigee further from the Earth. As a result, the orbit approaches a circular shape.
To be continued…
