After a successful launch, where does the rocket's final stage go?

"10, 9, 8, 7, 6, 5, 4, 3, 2, 1, ignition", as the countdown ended, the huge carrier rocket slowly rose into the sky with a huge roar, sending the satellite into space. Such a spectacular launch scene must have shocked you. Do you know where the last stage of the rocket goes after the launch? Do you know that in addition to becoming space junk, the last stage of the rocket can also become a space laboratory, a space hotel, or even be used to save the earth?

Today we will learn about the whereabouts of the rocket's final stage, a question that few people pay attention to.

Just like a train has different carriages, rockets are also divided into the first and second stages, and the last stage is called the final stage. The first few stages of the rocket are like dumplings with thin skin and large fillings. The "filling" is the fuel, and the "skin" is the shell of the rocket. Rocket launch is to burn fuel and exhaust gas to obtain continuous acceleration and send satellites into outer space. After the first-stage rocket fuel is burned out, the first-stage rocket is thrown away. Because the first-stage rocket shell weighs more than ten tons, continuing to fly with it will affect the continued acceleration of the rocket. Similarly, after the second-stage rocket fuel is burned out, the second-stage rocket must be thrown away. At this point, you must understand that only the final stage rocket carries the satellite into the target orbit. After the previous stages of the rocket are burned out, they are thrown away and eventually fall to the ground. This is why the launch of the rocket requires the calculation of the landing area and even the evacuation of the population in advance. It is not good to hit the flowers and plants. And the famous skill of Elon Musk of the US Space Exploration Company is to let the first-stage rocket return to the earth intact and reduce the launch cost by reusing it.

After the last stage of the rocket sends the satellite into the target orbit, it becomes a huge piece of space junk floating in space. In order to prevent this huge piece of space junk from exploding under high temperature and high pressure to produce more space junk, it is necessary to "drain" the remaining high-pressure gas, fuel, and electricity. This is the "passivation" operation of the rocket. If the last stage can leave orbit and enter the atmosphere to burn up, it would be great. However, most rocket last stages do not have the ability to leave orbit and often float in orbit for many years. If they are unfortunately hit by other debris during this period, an avalanche effect may form, producing a large number of small fragments, threatening the normal operation of satellites.

Since the final stage has also entered orbit, can it be transformed and the discarded final stage turned into treasure? Chinese researchers have proposed a test plan for the final stage of the rocket to remain in orbit. On the basis of the final stage of the rocket, by adding energy, communication, measurement and control modules, the final stage of the rocket is upgraded and transformed into a "space laboratory", making full use of the complete structure and orbital stay time of the final stage of the rocket, carrying a variety of scientific instruments, and conducting scientific experiments such as component verification, new material synthesis, biology, pharmaceuticals, and basic physics, providing scientists with more opportunities to conduct experiments in space. This technology has now become a reality.

Some people abroad have come up with a brilliant idea to transform the box of the final stage rocket into a space hotel to develop space tourism. A US startup called NanoRacks proposed using special materials to strengthen the fragile shell of the final stage of the rocket, increase its structural strength, and enable it to withstand the impact of tiny space debris. Then the huge internal space of the final stage of the rocket will be renovated and transformed into a space hotel. If this technology is feasible, then many abandoned final stages of rockets can be turned into chain hotels in space. It would be great to experience space life, appreciate the magnificent starry sky, overlook the earth's veins, and watch the sunrise and sunset every 90 minutes in the "final stage hotel"!

In fact, the last stage of the rocket can also be used to protect the earth! If a near-Earth asteroid hits the earth, in addition to using nuclear weapons to blow up the asteroid, the most reliable way is to launch an impactor to knock the asteroid off its orbit. But the weight of a man-made impactor is too light to deflect the asteroid to a safe distance. At this time, if you bring the last stage of the rocket to hit it, you can give full play to the weight advantage of the last stage and deflect the asteroid to an orbit farther away from us. For example, the dry weight of the last stage of the Long March 5 rocket is as much as 6.5 tons. Calculations have found that if a spacecraft is used to control the last stage of the Fat Five to hit an asteroid, one Fat Five rocket can have the asteroid defense effect of three Fat Fives. It can be said that big guys have great wisdom. At critical moments, the last stage of the rocket can be used to defend the earth!

Now you know that after a successful launch, the fate of the rocket's final stage is not just to become "space junk"! With the wisdom of scientists, the rocket's final stage can be turned into treasure, transformed into a space laboratory, a space hotel, and even save the earth in times of crisis! What other ideas do you have about turning waste into treasure for the rocket's final stage? !

This article is a work supported by Science Popularization China Starry Sky Project

Author: Li Mingtao

Reviewer: Zhou Binghong (Researcher at the National Space Science Center, Chinese Academy of Sciences)

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.