For now, there are two main ways to land a spacecraft. One spacecraft can glide like an airplane after returning to the earth’s atmosphere and then land at an airport, such as space shuttle; the other spacecraft enters at high speed first. The earth’s atmosphere then safely landed to the predetermined landing zone after a series of decelerations.
In general, the space shuttle can accurately taxi and land at the designated airport. The advantages in many aspects are obvious. Why do we not develop a space shuttle but use a traditional spacecraft? It is undeniable that the space shuttle does have many advantages, such as accurate landing, reusability, and strong carrying capacity. However, the space shuttle also has many disadvantages, such as high cost, high maintenance and launch costs, and low safety factor.
The United States built a total of 5 space shuttles in the last century. It was originally hoped that the reusable space shuttles will reduce the cost of space flight, but in fact, the cost of each flight is as high as 500 million US dollars, and 5 space shuttles. Two of the planes experienced a physical explosion, and 14 astronauts died as a result. Finally, the space shuttle withdrew from the stage of history in 2011 and was replaced by a traditional spacecraft.
Shenzhou XII is about to return to Earth
There are many spacecraft flying in space, such as our space station and Shenzhou XII spacecraft. Since its launch, the three astronauts of the Shenzhou XII spacecraft have been working and living in space for more than two months. In the past few dozen days, our astronauts have completed many scientific missions, Took 2 spacewalks. It is expected that these astronauts will return to Earth in about half a month. This time the landing site of the spacecraft is made public. It is not the previous Siziwangqi landing site, but Dongfeng landing site. The way to return is as described above. The second one mentioned is to turn on the parachute to slow down after entering the earth’s atmosphere.Finally, he stopped steadily near the landing site.
Siziwang Banner Landing Field: This landing field is located in the Amugulang Prairie in central Inner Mongolia. This is a famous space landing field, and the main landing field of the Kennedy Space Center of the United States, the Edwards Air Force Base of the United States , Russia’s main manned space landing site and other world-famous space landing sites are equally famous. Shenzhou-1 to Shenzhou-11 spacecraft are all landed on this landing site. Here, the area is open and the air visibility is high, search and rescue personnel can quickly start rescue, so it has become the first choice for the landing of the Shenzhou spacecraft .
Dongfeng Landing Field: This landing field is located in the Badain Jaran Desert and the Gobi zone. It is a vast and sparsely populated area and is also suitable for spacecraft landing, so it is an alternate landing field for the Siziwang Banner. The Shenzhou 12 spacecraft is about to land at the Dongfeng Landing Site, which will test the search and recovery capabilities of the Dongfeng Landing Site for the first time.
Why does the spacecraft burn when it returns?
I believe that many of my friends have seen the pictures of the spacecraft when it launches and returns to the earth. Although the spacecraft will pass through the earth's atmosphere during the launch and return to the earth, the situation is quite different. A spacecraft generally does not burn when it is launched into the air, but when it returns to Earth, it burns. What is going on?
In fact, it will not only burn when returning to Earth, but also when landing on the surface of a planet with an atmosphere. For example, the Mars probe is in the process of landing on Mars, the lander becomes a raging fireball falling from the sky, after burning for a period of time, the lander no longer burns.
Before launching,The speed of the spacecraft is zero at the beginning, and after launching into the air, the speed of the spacecraft will become faster and faster. At this time, the aerodynamic heating effect becomes stronger and stronger, and the temperature of the spacecraft will be higher and higher. However, as the height of the spacecraft continues to rise, the air density of becomes lower and lower, and the heat generated by the aerodynamic heating effect is not enough to make the spacecraft burn. Therefore, when we watch the spacecraft launch, we generally cannot see the picture of the spacecraft burning.
when returning to the earth, the situation is different. Before returning to Earth, the speed of the spacecraft is very fast. Some spacecraft are even close to the second cosmic speed (for example, the return capsule of Chang'e 5 is very fast when returning to the earth). When these spacecraft are extremely fast When the speed enters the atmosphere, the aerodynamic heating effect is very strong. As the height of the spacecraft continues to drop and the air density becomes greater and greater, the aerodynamic heating effect will be very strong, and the temperature outside the spacecraft will rise sharply, causing the spacecraft to look like a raging fireball. However, as the height of the spacecraft continues to drop, the air density becomes greater, the speed of the spacecraft becomes slower and slower, and the aerodynamic heating effect becomes weaker and weaker, so the burning phenomenon will not last for a long time.
In fact, not only the spacecraft will burn when returning to the earth, but the meteor showers and blazing fireballs we see are actually the same principle. The meteor showers that cut through the sky are also very fast before entering the atmosphere, but when they enter the atmosphere, they will burn violently and become brilliant meteors.
Although the spacecraft will briefly burn during its return to the earth’s atmosphere, the external temperature of the return capsule may be as high as several thousand degrees, but these phenomena have no effect on the astronauts in the spacecraft. Because the surface of the spacecraft's return cabin is coated with various ablative materials, it can avoid the high heat generated by the intense friction with the atmosphere from burning through the bulkhead. In order to avoid local overheating, the return cabin is generally equipped with a rolling attitude engine, which will be evenly heated by rotation.
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