Why did the first “Satellite” fall to Earth in just three months?

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On October 4, 1957, the Soviet Union launched Sputnik-1, which rose above the earth’s atmosphere and entered the orbit of our planet, making a full revolution around It in 90 minutes. In the clear sky of the world of those times, it was the only object of its kind: an artificial, man-made satellite. Unofficially, this meant the beginning of the space race, military and political activities, which for decades fascinated international politics.

But the Satellite is no longer in earth orbit. In fact, he stayed there so long that by the time Explorer 1, the first American satellite in space, was launched, Sputnik-2 was flying around the Earth for quite a long time with the first animal in space. But the original Satellite, having completed 1400 orbits, fell to Earth.

What happened to Sputnik was to be expected. In fact, this happens to most satellites if you launch them into near-earth orbit and leave them to yourself. With each orbit passed, the satellite first reaches its apogee, the maximum distance from The earth’s surface, and then perigee, the closest approach to the Earth. For a low earth orbit, this essentially means that the satellites are several hundred kilometers above The earth’s surface. Given that the line separating the earth’s atmosphere and outer space runs at an altitude of only 100 kilometers, at first glance it may seem that satellites should remain in space forever.

sputnik-650x479 Science  Why did the first "Satellite" fall to Earth in just three months?

But in reality, the situation is much more complicated. The atmosphere has no sudden end or boundary. The gaseous state does not tend to take shape for some reason other than the following: as you climb higher, the particle density will continue to fall, but different particles that are heated by collisions will move at different speeds: some faster, some slower, but with a clearly defined average speed.

The higher you go, the more likely you are to find particles that have more energy, because you need more energy to go to a higher altitude. The density of such particles at high altitude will be, of course, low, but will never fall to zero.

We found atoms and molecules that remain gravitationally bound to the Earth at altitudes up to 10,000 kilometers. The only reason we didn’t go beyond that 10,000 kilometers is because at that altitude The earth’s atmosphere becomes indistinguishable from the solar wind: both are made up of hot atoms and ionized particles.

The vast majority of our atmosphere (by weight) is contained in the lowest layers, the troposphere accounts for 75%, the stratosphere for another 20%, the mesosphere — almost 5%. But the next layer, the thermosphere, is incredibly diffused.

While an atmospheric particle at sea level has to travel a microscopic distance to collide with another molecule, the thermosphere is so diffuse that a normal atom or molecule can travel a kilometer and collide with nothing.

The thermosphere may seem like an empty space, because you will not even meet an atom. But rising to this height from The earth’s atmosphere, you linger in this reverse abyss of low density, being at the peak of your parabolic orbit, and then slowly return to your home planet under the influence of gravity.

But if you are a spacecraft, you will experience something completely different. The reasons are:

  • You do not rise from the Earth, and go around it in orbit, that is, moving in the opposite direction to the hot atmospheric particles.
  • Since you’re in a stable orbit, you have to move fast: at least 7 kilometers per second to stay in space.
  • You have the size of not an atom, but a spacecraft.
  • These three points together lead to disaster for any satellite in orbit.

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Such a disaster is inevitable because of the resistance that the satellite faces, which determines how much speed the satellite loses over time due to atmospheric particles entering it at a relatively high speed. Any satellite in low earth orbit will have a lifespan of several months to several decades, but nothing more. You can fight it by going higher, but it won’t help much.

Every time there is any activity on the Sun, such as sunspots, solar flares, coronary mass ejections or other explosive events, The earth’s atmosphere heats up. The hotter the particles, the higher the speed, and the higher the speeds of their movement will mean that they rise higher, increasing the density of the atmosphere even in space. When this happens, even satellites that were almost outside the gravitational pull begin to fall to Earth. Magnetic storms can also increase air density at extremely high latitudes.

And this process is cumulative, in the sense that as the satellite experiences attraction, its perigee falls to lower and lower altitudes. Now, at these lower altitudes, the drag force increases even more, and this causes you to lose your kinetic energy, which keeps you in orbit, even faster. The final spiral of death may take thousands, tens of thousands or even hundreds of thousands of orbits, but as the orbit is completed in 90 minutes, any satellite in low earth orbit will live for several decades at best.

This problem of falling back to Earth was not only a problem for the first satellites of the 1950s, but remained a problem for almost all the satellites we ever launched. 95% of all satellites created by humans are in earth orbit, including the international space station and the Hubble space telescope. If we had not periodically dispersed these devices, many of them would have fallen to the Ground.

Hubble and the ISS would have less than 10 years in their current orbits if we had just let them die. And while large satellites do die, they do so at the expense of uncontrolled re-entry into the atmosphere. Ideally, they should burn in the atmosphere or fall into the ocean, but if their debris falls on people, it will be a disaster.

And the Hubble telescope will also have to fall to the Ground. His orbit will be going down. The telescope itself will be fine, but with each orbit it will be closer and closer to the Earth.

The final mission of the telescope includes a docking mechanism, which was installed on the telescope: Soft Capture and Rendezvous System. Any equipped properly will be able to safely take the telescope home.

sssr-650x825 Science  Why did the first "Satellite" fall to Earth in just three months?

But if we talk about 25,000 other satellites in low-earth orbit, it will be impossible to carry out a controlled entry into the atmosphere. The earth’s atmosphere will lower them below the Pocket line, below the boundary with space we’ve drawn. If we stop launching satellites today, in a hundred years there will be no trace of the presence of humanity in earth orbit.

Sputnik 1 was launched in 1957, and just three months later, it spontaneously left orbit and fell to Earth. Particles in our atmosphere rises much higher than any of the artificial lines that we’ve drawn, affecting all our satellites. The farther the perigee, the longer you will stay in orbit. As long as we do not have the technology to keep satellites in orbit without fuel, The earth’s atmosphere will remain the most destructive force impeding the presence of man in space.


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