Whenever the manned space flight's return capsule lands safely, people's hearts are really relieved, which means that the astronauts have returned safely and smoothly.
At this time, the return capsule was already "beyond recognition" , and the surface was burned as black as charcoal.
It turned out that on the way back, the return capsule had violent friction with the atmosphere, was surrounded by raging fire. It can be said that the astronauts at this time were in a ball of fire.
After the return capsule enters the Earth's big ball, the temperature on the surface of the spacecraft can exceed 2000 degrees Celsius, so the black things we see are actually the metal on its surface that is burned and then cooled.
So how do our astronauts withstand such high temperatures, and how do the instruments inside the return capsule ensure normal operation under high temperatures?
The return capsule whose surface was burned into black carbon
The dangerous return journey
If the return capsule wants to cool down safely from space to the ground, it needs to experience a narrow escape . First of all, according to the regulations of Karman line , the area more than 100 kilometers above the ground is called outer space .
The return capsule needs to find a good angle to enter the earth's range from outer space - atmosphere . The area between 335 and 80 kilometers from the ground is called the "black barrier area". During this period, the spacecraft will lose contact with the command platform, and the process will last about 4 minutes. The
headquarters has no idea what will happen during this period. Once there is a problem with , there will be no chance of saving .
Schematic diagram of the black barrier area
The reason why the black barrier area appears is that the return capsule falls into the atmosphere very fast, at about 4 to 5 kilometers per second .
At such a fast speed, air molecules in the atmosphere experienced violent friction with the surface of the return capsule, causing the temperature on the surface of the return capsule to reach more than 2,000 degrees Celsius.
Under such a high temperature, the gas molecules in the atmosphere are ionized , producing a lot of positive and negative ions , which are wrapped around the outer of the return capsule.
Aerospace communications use electromagnetic waves . The wrapped positive and negative ions can just affect the transmission of electromagnetic waves, resulting in headquarters not receiving any signals from the return capsule.
fell into the black barrier area
After passing through the black barrier area, the speed of the return capsule began to slow down. Only then did begin to open the parachute .
Generally speaking, there are three parachutes in the return capsule. We saw on TV that the largest parachute was , but it was the that was opened last.
The first parachute of in the return capsule is actually a lead , which is used to lead out the two subsequent parachutes .
The second parachute is control direction , because the return capsule is not necessarily falling into the earth's atmosphere , it is very likely to have flipped during the process, does not have the bottom side down , the second parachute is adjust the position of the return capsule .
Finally, the third parachute is required, which is the largest one. It is called main parachute .
Its diameter has reached more than 10 kilometers , and the return capsule is as small as a toy in front of it.
The last parachute accompanies the return capsule all the way until it lands steadily on the ground. The moment the return capsule touches the ground, it must immediately cut off the connection with the main parachute.
Because it is so big, as long as the wind blows it, it will pull the return capsule and roll on the ground, which will make the astronauts in the capsule feel the rolling.
Cut off the parachute immediately after the return capsule lands.
Originally, astronauts need an adaptation process when returning to the earth from space. Letting them roll like this is very bad for the body, and it is very likely to hurt the astronauts inside.
Therefore, for safety reasons, the main parachute will be discarded after it has completed its duties.
After the return capsule landed steadily, the rescue team waiting at the side came forward. First, you need to check the air pressure inside and outside the return cabin, and do not open a position rashly.
Secondly, it is necessary to check the physical condition of the astronauts inside . After confirming that everything is OK, the hatch can be opened and the astronauts can be lifted out . Only at this time can
declare that the task has been successfully and successfully completed.
Rescue workers are checking the health of the astronauts
How to insulate
Everything in the cabin is intact because the shell of the return capsule is divided into several layers. The outermost layer of
is actually easy to burn and volatile materials . When they burn, they will take away a lot of heat . The inner layer of
is made of high-temperature resistant material , which will not melt at more than 2,000 degrees, so the astronauts in the cabin cannot feel the high temperature outside.
Astronauts still wear spacesuits during the return process. Even if unfortunately a malfunction occurs in the return capsule and the external temperature is transmitted to the cabin,the spacesuit can also provide certain protection and isolate the high temperature from the astronauts. s damage.
Check the return capsule
Why astronauts still wear spacesuits in the return capsule? This is a lesson learned at the expense of the lives of three astronauts in human history .
In 1971, the former Soviet Union's Alliance No. 11 had an incident where the valve was opened during the return process, causing them to have an accident in outer space.
Due to the extremely unreasonable design of the spacecraft at that time and the narrow space in the cabin, the astronauts were forced not to wear spacesuits in order to accommodate the spaceship.
When the accident occurred, three astronauts were exposed to the space environment . They were burst by the air in their bodies, body fluids boiled , and eventually died in pain.
It is this lesson that astronauts from various countries must wear spacesuits during their return, regardless of whether the return capsule is intact or not.
Inside the return capsule
Rocket launch
Regarding the burning after the return capsule enters the atmosphere, someone has raised this question. When the rocket is launched, also has to pass through the atmosphere . Why is the spacecraft entering space not burned? Into black carbon?
First of all, the speed of the rocket passing through the atmosphere during launch is not as fast as the speed of falling into the atmosphere during the return process.
From when the rocket is launched to when it crosses the Kármán line , during this journey, the speed of the rocket is from low to high .
Therefore, the friction between the atmosphere and it is not as severe as when returning.
Secondly, when the rocket is launched, the spacecraft is wrapped by the shell . The shell burns and falls off , which plays a role in protecting the spacecraft.
The rocket launches
and the return capsule has nothing during the return process. It has to bear the heat generated by surface friction entirely on its own. When the
rocket was launched, many parts were actually burned into black charcoal, but they were either burned up in the air, or fell to a place where the earth could not see it, such as the sea.
To know the speed of the spacecraft orbiting the earth, the minimum speed must reach the first cosmic speed , which is 7.9 kilometers per second . In order to save fuel, the return capsule adopts a free fall method after entering the earth, which causes its speed to be much faster than that of the rocket when it is launched.
Shedding objects from rocket launch
Some people have made suggestions for this, why does every return capsule have to experience such a dangerous burning?
Historically, accidents occurred during the return process, resulting in the disintegration of the Columbia space shuttle , and the death of astronauts in the former Soviet Union Soyuz 1 due to a parachute accident .
These accidents show that traveling through the atmosphere is a very dangerous thing, so can humans avoid these narrow escapes during return.
The Space Shuttle Columbia disintegrated
Solving the high temperature
Someone mentioned that since the frictional heat is caused by the free fall of the return capsule in the atmosphere, can the speed be reduced at the moment the spacecraft enters the Earth? , thereby slowing down surface friction and heat generation? The idea of ​​
is actually okay, but is not necessary. First of all, if you want to slow down the spacecraft when it enters the earth, you must give the return capsule a reverse acceleration , which requires extra fuel to burn .
The return capsule will basically not carry much fuel. If this is really needed, the return capsule will be designed to be larger than it is now and carry enough fuel to ensure reverse acceleration.
The return capsule generally does not carry fuel
The design of the entire rocket will be changed, and the total fuel carried will increase. This is a big challenge for a spacecraft that carries a heavy weight.
Secondly, such a design will inevitably increase the cost of each flight . If the reverse acceleration is not mastered well, it is easy for the return capsule to roll in the atmosphere, which will make things more complicated. The final result of
is that money is spent, and it may not achieve the desired effect.
At present, this return method has the lowest cost.
Finally, looking at the several return accidents in human history, without exception, the surface of the aircraft was damaged, resulting in the high temperature during the return process to amplify the damage. .
means that determines the safety of the return capsule , not its landing speed , but its surface quality .
Instead of spending a lot of time thinking about how to reversely brake the return capsule, it is better to design the surface of the return capsule to be more solid, so as to better ensure the safety of astronauts.
The return capsule at the exhibition
I hope every astronaut can return to Earth safely.
