On September 29, Beijing time, the United States company SPaceX launched a Crew Dragon spacecraft to carry out a special mission. The reason why this mission is special is that, unlike previous manned missions, this is to carry out a so-called "space rescue" mission.
That's because on June 5, United States' Boeing launched a manned Starliner spacecraft to carry two astronauts to the International Space Station on its first manned mission. According to the original plan, the two astronauts would stay on the ISS for a few days and then return to Earth in a Starliner spacecraft.
However, due to the many problems of the "Starliner" spacecraft, it was impossible to ensure a safe return, and the return time of the "Starliner" spacecraft was constantly delayed, and finally it had to return in an "unloaded" way, that is, it would return to Earth without astronauts. And these two astronauts have been trapped on the International Space Station for more than 3 months.
In this way, even if there is a problem with the "Starliner" spacecraft during the return process, it will not affect the safety of the astronauts. However, as a result, the two astronauts involved in the mission could not return to the mission on time and had to wait for a new spacecraft to pick them up. NASA's plan was for SPaceX to launch a Crew Dragon spacecraft to bring the two astronauts back.
On September 29, a Crew Dragon spacecraft was launched, which will dock with the International Space Station on September 30. This is the ninth astronaut rotation mission of the Crew Dragon spacecraft, codenamed "Crew-9", and this time it carries only two astronauts, Nick Haig of United States and Alexander Gorbunov of Russia.
The Dragon spacecraft is a new generation of manned spacecraft that can be reused, and in previous manned missions, it generally carried 4 astronauts, but this mission only carried 2 astronauts, and the purpose was to reserve 2 seats for the two astronauts of the Boeing "Starliner" spacecraft.
Although the Crew Dragon spacecraft has now been launched, the two astronauts who will bring back the "Starliner" spacecraft will be picked up when they return home, which is good news for these two astronauts, and the plan for returning home has finally been determined, but because the Crew Dragon spacecraft will not return until February next year, the two astronauts still need to stay on the International Space Station for a few months, which were originally carried out for a few days, but now it has been extended to eight months.
The drastic extension of the flight time is not good news for either the two astronauts or the normal operation of the International Space Station. On the one hand, the longer the flight, the greater the physical impact on the astronauts, which is why space station missions are generally rotated for about 6 months, and these two astronauts need to stay on the ISS for almost 8 months.
On the other hand, due to the addition of these two "uninvited guests" to the International Space Station, this also affects the subsequent manned missions of the International Space Station, no, the Crew Dragon spacecraft, which was supposed to carry 4 astronauts, can only carry 2 astronauts when performing the mission codenamed "Crew-9".
Moreover, because the two astronauts returned to the ISS on time, in order to make the ISS operate normally, the United States and Russia have launched cargo spacecraft to resupply and transport supplies including food and water to the ISS.
In any case, even if the two astronauts will stay on the ISS for nearly eight months and overstay the flight, it is the best news that they can return safely. Because the spacecraft was very thrilling in the process of returning home, and there was no way to ensure the safety of the "Starliner" spacecraft, NASA did not dare to let the two astronauts take risks, and used the more reliable Crew Dragon spacecraft to pick them up.
The spacecraft will be subjected to nearly 2,000°C burns on its return
Although the "Starliner" spacecraft finally landed safely, it is understandable that United States NASA chose a more secure return plan and let the "Starliner" spacecraft return empty. After all, no one knows whether the "Starliner" spacecraft will have problems during the return process, you know, the process of the spacecraft returning to Earth from outer space is very thrilling, and it needs to withstand a high temperature close to 2000 °C.
This is because the spacecraft needs to reach a fast enough speed to orbit the Earth, which is close to the Earth's first cosmic velocity of 7.9 kilometers per second. If the speed is much lower than this, the spacecraft will continue to lose altitude under the effect of gravity and air resistance, and then fall into the atmosphere, unable to fly for a long time.
It is precisely because the spacecraft is flying so fast that the spacecraft needs to undergo a series of braking and deceleration on the process of returning to Earth to reduce the speed in order to land safely. The earth has a dense atmosphere, the lower the altitude, the greater the air density, the greater the air resistance, under the action of air resistance, the speed of the spacecraft will gradually decrease, but when the spacecraft breaks into the earth's atmosphere at such a fast speed, it will face a problem, that is, the aerodynamic heating effect.
That is to say, when the spacecraft re-enters the Earth's atmosphere at high speed, the aerodynamic heating effect will be very strong, causing the temperature outside the spacecraft to rise sharply, and the temperature in the local area can even approach 2000 °C. Under such high temperatures, ordinary materials are unbearable, so those satellites, rocket wreckage, and spacecraft wreckage returning from outer space will burn directly in the atmosphere.
The return capsule of the manned spacecraft is specially designed to withstand burns of more than 2000 ° C without problems. However, under the scorching heat of such a high temperature, the exterior of the spacecraft's return capsule will still change, and some areas will be burned beyond recognition and black due to the high temperature.