Why doesn't the ISS fall from orbit? Why do people experience weightlessness in space? Facts about the ISS
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.
Falling “near the Earth”
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, 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.
Or why don't satellites fall? The satellite's orbit is a delicate balance between inertia and gravity. The force of gravity continually pulls the satellite towards the Earth, while the inertia of the satellite tends to keep its motion straight. If there were no gravity, the satellite's inertia would send it directly from Earth's orbit into outer space. However, at each point in the orbit, gravity keeps the satellite tethered.
To achieve a balance between inertia and gravity, the satellite must have a strictly defined speed. If it flies too fast, the inertia overcomes gravity and the satellite leaves orbit. (Calculating the so-called second escape velocity, which allows a satellite to leave Earth orbit, plays an important role in the launch of interplanetary space stations.) If the satellite moves too slowly, gravity will win the fight against inertia and the satellite will fall to Earth. This is exactly what happened in 1979, when the American orbital station Skylab began to decline as a result of the growing resistance of the upper layers of the earth's atmosphere. Caught in the iron grip of gravity, the station soon fell to Earth.
Speed and distance
Because Earth's gravity weakens with distance, the speed required to keep a satellite in orbit varies with altitude. Engineers can calculate how fast and how high a satellite should orbit. For example, a geostationary satellite, always located above the same point on the earth's surface, must make one orbit in 24 hours (which corresponds to the time of one revolution of the Earth around its axis) at an altitude of 357 kilometers.
Gravity and inertia
The balancing of a satellite between gravity and inertia can be simulated by rotating a weight on a rope attached to it. The inertia of the load tends to move it away from the center of rotation, while the tension of the rope, acting as gravity, keeps the load in a circular orbit. If the rope is cut, the load will fly away along a straight path perpendicular to the radius of its orbit.
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.
Space debris hole in shuttle Endeavor STS-118 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.
We are talking about the fact that any object located in close proximity to the Earth is affected by its gravitational force. And if so, then it cannot stay in its orbit for a long time, and will definitely fall to the surface if it does not burn up in the upper layers of the atmosphere before that. The same fate, in theory, should befall the ISS, which is located 400 kilometers from the surface of the planet. But even such a considerable distance cannot relieve the space station from the force of earth's gravity. But then how does it stay in a stationary orbit for such a long time?
Let's first figure out what the international space station is. This is a complex modular design, weighing 400 tons. If we talk about its size, it is approximately the same as an American football field. It took 13 years to assemble such a structure. During this time, a huge amount of work was carried out, which includes: numerous launches of Progress space cargo ships, American Shuttles, and astronauts going into outer space. The international space station currently costs more than $150 billion. There are six cosmonauts constantly at the station, who are representatives of different countries of the world.
But let's return to our original question and try to figure out why the station, under the influence of gravity, does not fall to the surface of the Earth.
In fact, it is slowly falling. During the year, its decline reaches two kilometers. And if it weren’t for the orbit adjustment, we would have said goodbye to it long ago. It is timely adjustments that allow the ISS to remain in a stationary orbit. You won’t believe it, but such a complex and heavy design has the highest mobility. It can change orbital parameters, move in all directions, and even turn over if necessary, in order, for example, to dodge various space objects, which include space debris.
All movements are carried out using special engines called gyrodins. There are four of them at the station. To orient the station or adjust its orbit, a command is received from the Earth to launch them, after which the station begins its movement. A special operator is responsible for such a responsible operation. His responsibility includes not only timely adjustment of the ISS orbit, but also ensuring its safety, in order to prevent collisions with meteorites and space debris. Similar boosters and engines are available on the Progress cargo spacecraft that dock with the ISS. With their help you can also correct its orbit.
The operator also monitors the weight of the station. Without this, it is impossible to accurately calculate the thrust of herodins, which should not be less than 1 m/second. The mass of the station is constantly changing. As a rule, this happens at the moment of docking of the next Progress cargo ship, which delivers payload on board. Cosmonauts do not take any part in the process of planned station relocation. Everything is controlled by an operator from Earth.