The atmosphere of our planet protects us from ultraviolet radiation and from numerous meteorites approaching the Earth. Most of them burn up completely in the dense layers of the atmosphere, just like space debris falling from orbit. But this circumstance is a whole problem for the space industry, because astronauts need to not only be sent into orbit, but also returned back. But astronauts safely complete their stay on the International Space Station, returning in special capsules that do not burn up in the atmosphere. Today we will look at why this happens.
Spaceships, like extraterrestrial objects, suffer from the destructive effects of the atmosphere. With the aerodynamic resistance of the gas layers of the atmosphere, the surface of any body moving at a significant speed is heated to critical values. Therefore, designers had to put a lot of effort into solving this problem. The technology for protecting space technology from such effects is called ablative protection. It includes a surface layer based on asbestos-containing compounds, which is applied to the external part of the aircraft and is partially destroyed, but allows the spacecraft itself to be kept intact.
The return of astronauts from the ISS to Earth takes place in a special capsule, which is located on the Soyuz spacecraft. After undocking from the ISS, the ship begins to move towards Earth, and at an altitude of about 140 kilometers it breaks up into three parts. The instrumentation and utility compartments of the Soyuz spacecraft completely burn up in the atmosphere, but the descent vehicle with the astronauts has a protective layer and continues to move on. At approximately an altitude of about 8.5 kilometers, a braking parachute is released, which significantly slows down the speed and prepares the device for landing.
If you look at the photographs of the capsules with astronauts after their landing, you will see that they are almost black in color and have traces of burning as a result of flying through the layers of the atmosphere.
When asked why objects, as well as the astronauts themselves, are in weightlessness while in orbit, you can often hear incorrect answers. In reality, there is a force of gravity in space, because it is what holds the planets together.
Without the action of gravity, galaxies could simply fly apart in all directions. In fact, weightlessness occurs due to the presence of movement speed.
In reality, astronauts, as well as other objects that are in Earth's orbit, fall. However, this fall does not occur in the usual sense (to the Earth, with orbital speed), but as if around the Earth.
Moreover, their movement must be at least seventeen and a half miles per hour. When accelerating relative to the Earth, the force of gravity here transfers the trajectory of motion, directing it downward, so astronauts during a flight will never be able to overcome the minimum approach to the Earth. And due to the fact that the acceleration of the astronauts is equal to the acceleration of the space station, they are in a state of weightlessness.
The International Space Station (ISS) is a large-scale and, perhaps, the most complex technical project in its organization in the entire history of mankind. Every day, hundreds of specialists around the world work to ensure that the ISS can fully fulfill its main function - to be a scientific platform for studying the boundless space and, of course, our planet.
When you watch the news about the ISS, many questions arise regarding how the space station can generally operate in extreme conditions of space, how it flies in orbit and does not fall, how people can live in it without suffering from high temperatures and solar radiation.
Having studied this topic and collected all the information together, I must admit that instead of answers I received even more questions.
At what altitude does the ISS fly?
The ISS flies in the thermosphere at an altitude of approximately 400 km from the Earth (for information, the distance from the Earth to the Moon is approximately 370 thousand km). The thermosphere itself is an atmospheric layer, which, in fact, is not yet quite space. This layer extends from the Earth to a distance of 80 km to 800 km.
The peculiarity of the thermosphere is that the temperature increases with height and can fluctuate significantly. Above 500 km, the level of solar radiation increases, which can easily damage equipment and negatively affect the health of astronauts. Therefore, the ISS does not rise above 400 km.
This is what the ISS looks like from Earth
What is the temperature outside the ISS?
There is very little information on this topic. Different sources say differently. They say that at a level of 150 km the temperature can reach 220-240°, and at a level of 200 km more than 500°. Above that, the temperature continues to rise and at the level of 500-600 km it supposedly already exceeds 1500°.
According to the cosmonauts themselves, at an altitude of 400 km, at which the ISS flies, the temperature is constantly changing depending on the light and shadow conditions. When the ISS is in the shade, the temperature outside drops to -150°, and if it is in direct sunlight, the temperature rises to +150°. And it’s not even a steam room in a bathhouse anymore! How can astronauts even be in outer space at such temperatures? Is it really a super thermal suit that saves them?
An astronaut's work in outer space at +150°
What is the temperature inside the ISS?
In contrast to the temperature outside, inside the ISS it is possible to maintain a stable temperature suitable for human life - approximately +23°. Moreover, how this is done is completely unclear. If it is, for example, +150° outside, how can you cool the temperature inside the station or vice versa and constantly keep it normal?
How does radiation affect astronauts on the ISS?
At an altitude of 400 km, background radiation is hundreds of times higher than on Earth. Therefore, astronauts on the ISS, when they find themselves on the sunny side, receive radiation levels that are several times higher than the dose received, for example, from a chest x-ray. And during moments of powerful solar flares, station workers can take a dose 50 times higher than the norm. How they manage to work in such conditions for a long time also remains a mystery.
How does space dust and debris affect the ISS?
According to NASA, there are about 500 thousand large debris in low-Earth orbit (parts of spent stages or other parts of spaceships and rockets) and it is still unknown how much similar small debris. All this “good” rotates around the Earth at a speed of 28 thousand km/h and for some reason is not attracted to the Earth.
In addition, there is cosmic dust - these are all kinds of meteorite fragments or micrometeorites that are constantly attracted by the planet. Moreover, even if a speck of dust weighs only 1 gram, it turns into an armor-piercing projectile capable of making a hole in the station.
They say that if such objects approach the ISS, the astronauts change the course of the station. But small debris or dust cannot be tracked, so it turns out that the ISS is constantly exposed to great danger. How the astronauts cope with this is again unclear. It turns out that every day they greatly risk their lives.
The hole in the shuttle Endeavor STS-118 from space debris looks like a bullet hole
Why doesn't the ISS fall?
Various sources write that the ISS does not fall due to the weak gravity of the Earth and the station’s escape velocity. That is, rotating around the Earth at a speed of 7.6 km/s (for information, the period of revolution of the ISS around the Earth is only 92 minutes 37 seconds), the ISS seems to constantly miss and does not fall. In addition, the ISS has engines that allow it to constantly adjust the position of the 400-ton colossus.
As you know, geostationary satellites hang motionless above the earth over the same point. Why don't they fall? At that height there is no force of gravity?
A geostationary artificial Earth satellite is a device that moves around the planet in the eastern direction (in the same direction as the Earth itself rotates), in a circular equatorial orbit with a period of revolution equal to the period of the Earth’s own rotation.
Thus, if we look from the Earth at a geostationary satellite, we will see it hanging motionless in the same place. Because of this immobility and the high altitude of about 36,000 km, from which almost half of the Earth's surface is visible, relay satellites for television, radio and communications are placed in geostationary orbit.
From the fact that a geostationary satellite constantly hangs over the same point on the Earth’s surface, some draw the incorrect conclusion that the geostationary satellite is not affected by the force of gravity towards the Earth, that the force of gravity disappears at a certain distance from the Earth, i.e. they refute the very Newton. Of course this is not true. The launch of satellites into geostationary orbit is calculated precisely according to Newton’s law of universal gravitation.
Geostationary satellites, like all other satellites, actually fall to the Earth, but do not reach its surface. They are acted upon by a force of attraction to the Earth (gravitational force), directed towards its center, and in the opposite direction, a centrifugal force (force of inertia) repelling the Earth acts on the satellite, which balance each other - the satellite does not fly away from the Earth and does not fall on it exactly just like a bucket spun on a rope remains in its orbit.
If the satellite did not move at all, then it would fall to the Earth under the influence of gravity towards it, but satellites move, including geostationary (geostationary - with an angular velocity equal to the angular velocity of the Earth’s rotation, i.e. one revolution per day, and satellites in lower orbits have a higher angular velocity, i.e. they manage to make several revolutions around the Earth per day). The linear speed imparted to the satellite parallel to the Earth's surface during direct insertion into orbit is relatively large (in low Earth orbit - 8 kilometers per second, in geostationary orbit - 3 kilometers per second). If there were no Earth, then the satellite would fly at such a speed in a straight line, but the presence of the Earth forces the satellite to fall on it under the influence of gravity, bending the trajectory towards the Earth, but the surface of the Earth is not flat, it is curved. As far as the satellite approaches the Earth's surface, the Earth's surface moves away from under the satellite and, thus, the satellite is constantly at the same height, moving along a closed trajectory. The satellite falls all the time, but cannot fall.
So, all artificial Earth satellites fall to Earth, but along a closed trajectory. Satellites are in a state of weightlessness, like all falling bodies (if an elevator in a skyscraper breaks down and begins to fall freely, then the people inside will also be in a state of weightlessness). The astronauts inside the ISS are in weightlessness not because the force of gravity to the Earth does not act in orbit (it is almost the same there as on the surface of the Earth), but because the ISS freely falls to the Earth - along a closed circular trajectory.
Why do you think astronauts experience weightlessness in space? There is a high probability that you will answer incorrectly.
When asked why objects and astronauts appear in a state of weightlessness in a spaceship, many people give the following answer:
1. There is no gravity in space, so they weigh nothing.
2. Space is a vacuum, and in a vacuum there is no gravity.
3. The astronauts are too far from the surface of the Earth to be affected by the force of its gravity.
All these answers are wrong!
The main thing you need to understand is that there IS gravity in space. This is a fairly common misconception. What keeps the Moon in its orbit around the Earth? Gravity. What keeps the Earth in orbit around the Sun? Gravity. What prevents galaxies from flying apart in different directions? Gravity.
Gravity exists everywhere in space!
If you were to build a tower on Earth 370 km (230 miles) high, approximately the altitude of the space station's orbit, the force of gravity on you at the top of the tower would be almost the same as at the surface of the earth. If you were to step off the tower, you would be heading towards Earth, just as Felix Baumgartner plans to do later this year when he attempts to jump from the edge of space. (Of course, this doesn't take into account the cold temperatures that will instantly freeze you, or how the lack of air or aerodynamic resistance will kill you, and how falling through layers of atmospheric air will force every part of your body to experience first-hand what it's like to "rip off three skins" "And besides, a sudden stop will also cause you a lot of inconvenience).
Yes, so why don't the space station or satellites in orbit fall to Earth, and why do astronauts and their surroundings inside the International Space Station (ISS) or any other spacecraft appear to float?
It turns out that it's all about speed!
Astronauts, the International Space Station (ISS) itself, and other objects in Earth's orbit do not float—in fact, they fall. But they do not fall to Earth due to their enormous orbital speed. Instead, they "fall around" the Earth. Objects in Earth's orbit must travel at least 28,160 km/h (17,500 mph). Therefore, as soon as they accelerate relative to the Earth, the force of the Earth's gravity immediately bends and takes their trajectory downward, and they never overcome this minimum approach to the Earth. Because astronauts have the same acceleration as the space station, they experience a state of weightlessness.
It happens that we can also experience this state - briefly - on Earth, at the moment of the fall. Have you ever been on a roller coaster ride where, right after passing the highest point (the “top of the roller coaster”), when the cart begins to roll down, your body lifts out of the seat? If you were in an elevator at the height of a hundred-story skyscraper, and the cable broke, then while the elevator was falling, you would float in weightlessness in the elevator cabin. Of course, in this case the ending would have been much more dramatic.
And then, you've probably heard of the zero-gravity aircraft ("Vomit Comet") - the KC 135 airplane, which NASA uses to create short-term states of weightlessness, for training astronauts and testing experiments or equipment in zero-gravity (zero-G) conditions. , as well as for commercial flights in zero gravity, when the plane flies along a parabolic trajectory, like in a roller coaster ride (but at high speeds and at high altitudes), passes through the top of the parabola and rushes down, then at the moment the plane falls, conditions are created weightlessness. Fortunately, the plane comes out of the dive and levels out.
However, let's return to our tower. If instead of a normal step from the tower you took a running jump, your energy directed forward would carry you far from the tower, at the same time, gravity would carry you down. Instead of landing at the base of the tower, you would land at a distance from it. If you increased your speed as you took off, you would be able to jump farther from the tower before you reached the ground. Well, if you could run as fast as the reusable space shuttle and ISS orbit the Earth, at 28,160 km/h (17,500 mph), the arc of your jump would circle the Earth. You would be in orbit and experience a state of weightlessness. But you would fall without reaching the surface of the Earth. True, you would still need a spacesuit and supplies of breathable air. And if you could run at about 40,555 km/h (25,200 mph), you would jump just outside the Earth and start orbiting the Sun.
