Lead
The successful completion of the Apollo moon landing program by the United States in 1969 has remained a huge mystery, and even in the 21st century, the Apollo program still has many unsolved mysteries.
At that time, the moon landing was an important demonstration of the power of the United States, but people found an interesting phenomenon during this period, that is: "Why is it that the rocket is fine when it flies out, but the spacecraft burns when it comes back?"
In fact, this is closely related to speed.
The spacecraft comes back to slow down, and if there is no way, the friction of the atmosphere alone will have an incredible amount of heat, and it will even blow up the spacecraft.
The rocket flies out differently, most of the speed is used to counteract the earth's gravity, they can't escape the gravitational range of the sun, so many people will be curious about how fast the rocket flies out, which solar system friends also have this speed?
The ship has to slow down when it comes back.
Flying out of space from Earth is easy, as long as it's fast enough.
However, the return of the spaceship is not so simple, and if it is too fast, it will kill people.
In order for a vehicle to fly out of the Earth, it needs to reach the first cosmic velocity, and then fly out, and the speed is not so important - as long as it escapes the gravitational range of the Earth.
And in order for the spacecraft to finally enter lunar orbit, it must have sufficient linear velocity – that is, orbital velocity.
In order to be able to land in the area where the United States is located on the way back to Earth, and finally to stay alive, the spacecraft must slow down again, so the spacecraft must slow down when it flies back to Earth.
Some people will ask, why not just adjust the speed of the ship?
Why use rockets to slow down when you return to Earth?
This is because the power that humans can make at present cannot achieve the effect of slowing down slowly, and the power created by humans is too heavy, so in order to fly out, people still decide to save as much as they want.
As the rocket slows back, the rocket can only throw away the top part of the rocket, leaving the potatocake-shaped return capsule.
In order to prevent the return capsule from burning, people also designed to jet the high-temperature resistant butt towards the rocket, and use the force of the rocket to push backwards to slow down, without actively filling the fuel of the hand-out party.
In this way, the weight of the rocket is greatly reduced, and a lot of fuel money is saved.
After returning to Earth, the spacecraft will go through several re-entry processes, which also greatly change the speed of the spacecraft back to Earth.
The process of deceleration is actually the conversion of speed into heat.
In the process of decelerating, the spacecraft feels a little hot in its body, because the spacecraft is fast and hot, and when it rubs against atmospheric molecules, the friction will produce heat, and the heat generated will be carried away by the molecules.
In this way, the speed of the ship is weakened.
The three re-entry processes that a vehicle must go through to return to Earth are called "re-entry processes".
When the spacecraft flies to the earth, it will rub against the atmosphere to produce a lot of heat, and this heat will cause the temperature of the surface of the spacecraft to rise, which is very high, and if you want to cancel it, you have to come up with a lot of fuel, and if you run out of fuel, the spacecraft will be finished.
As a result, the exterior of the ship is protected by a thick layer of heat to protect against high temperatures.
When the spacecraft leaves the earth and returns to space, the friction of the atmosphere suddenly disappears, which will cause a large acceleration to act on the spacecraft, and the spacecraft is too fast at this time, and it is easy to fly far away.
After the spacecraft leaves space, it throws away the outer layer of thermal protection, and after the speed is reduced by more than half, it only needs to open the door to release the spacecraft, and the spacecraft can descend back to Earth.
By the time the spaceship was released, that is, when only the spaceship was left, it was already much faster than before, more than twice as fast.
How fast does a rocket fly out?
In order to be able to fly the spacecraft out of the earth, people made a large rocket, and the rocket has jet power, even if it weighs several tons, it can still fly, so in fact, it mainly depends on the rocket itself, but the rocket itself is also heavy, and people still decided to load a little more fuel. Even so, people still hope that the rocket will fly as fast as possible, because in this way, the rocket will fly out less painfully, and the rocket will fall happily.
In order to know in advance what this speed was, people did a lot of calculations, and the result was half the fastest speed that people could grasp at that time.
This velocity is also known as the "second cosmic velocity".
It was discovered that if a spacecraft wanted to leave Earth, it had to fly at the maximum speed at the minimum altitude that the vehicle could reach, so as to waste as little fuel as possible.
Another very interesting property of this calculated velocity is that if you let a rocket fly at this speed if you keep it on an orbit that is not hindered by air friction, then when the rocket escapes the gravitational range of the earth, it will fly towards the sun, and it will fly to a certain distance and then stop, and will not fly again.
This distance is about the same as the radius of the Earth's orbit, so when flying to this distance, people can retract the spacecraft and no longer have to work.
If you want the rocket to come back, the main thing is to slow down.
The rocket uses an engine, and the way the engine works is actually to jet backwards.
The gas ejected by the rocket is very hot, and the impact head can be steamed, so when the spacecraft comes back, there is no need to set large brakes, just tell the engine at the head of the spacecraft to use it for a while longer.
However, an engine needs fuel, and how long it lasts depends on how much fuel it has.
What if you run out of fuel and the ship hasn't come back?
Slow down in some other way, of course: drive forward.
Therefore, after the spacecraft returns for a period of time, scientists will calculate how long the spacecraft will fly according to the speed and position of the spacecraft, and then calculate how much fuel the spacecraft still has.
When they heard that there was still fuel, the people were ecstatic, because the parts that were not powerful and did not need to be thrown away were no longer needed, so that the ship was light and fast.
At what speed does the ship go all the way forward?
First, spiral star spacecraft: spiral stars are a kind of white dwarfs, their radius is small, but the mass is large, so the surface gravity is still very large, this kind of planet is relatively easy to eat Pepsi near the planet, and after eating, it begins to fart air particles.
The gravitational pull of these air-shot particles and the white dwarf will produce some strange phenomena before, such as: when the speed of the air-shot particles is low, they will want to fly out, but they will be attracted by the gravitational pull of the white dwarf, and finally stay in place quietly and will not fly again;
When the velocity of the air-shot particles is high, they can escape the gravitational pull of the white dwarf and thus escape farther away.
Because the white dwarf is constantly flying out of the air particles, it has a gas cloud around it, and this gas cloud is different, it has both low-velocity gas and high-speed gas, and these gases with different velocities have different footholds, and these footholds form a spiral shape.
Although spirals are named after the velocity of the air-shot particles, they behave differently on low-velocity gases than popular spirals in that they rotate faster.
The velocity of the gas flying out of the spiral star is about its speed of sound, about 300 km/s, and the high-velocity gas is even more powerful.
They are even half as fast as the Sun, and some have even reached 99.95% of the speed of light.
Second, Venus: Venus is similar to the Earth, so flying from Venus to Earth, the spacecraft can only fly for about a year or two, which is not counting whether the spacecraft can fly fast, if the spacecraft leaves Venus, the speed is too fast, it is possible to fly farther.
However, it is inseparable from the gravitational range of the sun, so the planet-solar system partner formed by the combination of the sun and Venus has always been in an intimate relationship.
epilogue
It can be seen that many planets, like human spaceships, need to go very fast, and of course, many more spaceships go much faster than human spaceships.
For example, one of the most well-known customers in outer space, Halley's Comet, has a speed of about 54 kilometers per second, about a dozen times that of the Earth, and Halley's Comet is also faster than the Earth, and it only takes about 76 years to circle the sun.
In fact, Halley's Comet is still stranded in the outer circle of the solar system, and there are some planets and asteroids, which are faster and more powerful, and there are also some planets that not only fly fast, but also run far, so the universe still hides a lot of secrets that we don't know, and everything needs to be explored by people.