Three minutes to talk about popular science
To become a qualified astronaut, you need to go through many challenges, and the mere fact that "working in a weightless environment for a long time" is not something that ordinary people can do.
Because long-term exposure to weightlessness will cause a series of changes in the human body, muscle atrophy, cognitive decline, and loss of balance, which are unavoidable, so if human beings want to truly leave the earth and go to the universe, artificial gravity technology is indispensable. We are no strangers to "artificial gravity", as this technology is often seen in science fiction movies. Although the spacecraft in science fiction movies are all strange, one thing is the same: there is something like a disc that is constantly spinning, and this is the artificial gravity system.
Is an artificial gravity system hard?Theoretically, it's not difficult at all, just turn it up.
A rotating object produces a centrifugal force, of course, the centrifugal force itself is only a manifestation of inertia, not a real force, it is a virtual force, and this statement can make the problem seem simpler. Due to the action of centrifugal force, the objects in the rotating system will be pulled against the outer wall, and when the person is in this rotating system, the person is stationary relative to the rotating system, and at this time, it is not the system that rotates for the person, but the whole world outside the system. Because centrifugal force is equivalent to gravity, a person inside a rotating system will feel the same as real gravity.
If it's so simple in theory, why hasn't an artificial gravity system been implemented in reality?
It's easy to make a rotating system, but to successfully simulate gravity equal to Earth's, one thing must be considered: rotational speed. If the radius of the rotating system is shorter, then the required rotational speed will be higher, in the case of the core module of the Tianhe space station in China, which has a diameter of 42 meters, if you want to simulate the earth's gravity, then the rotation speed must reach twenty or thirty revolutions per minute.
In such a high-speed space, there is no way for people to move normally.
Why?Because of the Coriolis effect. To put it simply, an object moving in a rotating coordinate system will deflect its path, and the faster the rotation, the more obvious this deflection will be. For example, in a system that rotates twenty or thirty times per minute, we just try to stand up from a chair and fall headlong to the ground, which is the result of the Coriolis effect. There is no way to completely eliminate the Coriolis effect, even in a large rotating system like the Earth, the movement of objects will still be deflected, so the fluid in the Northern Hemisphere will shift to the right, the fluid in the Southern Hemisphere will shift to the left, and the atmosphere and ocean circulation will be affected by this.
Fortunately, the earth is large enough, so this movement deflection does not have much impact on our daily activities.
So for a spacecraft, how much diameter should be reached so as not to affect the normal activities of people on it?According to calculations, the diameter should be at least 100 meters or more. However, this is only calculated by treating people as a point, and in fact people are not a point, people themselves have a height. In a circular rotation system with a diameter of 100 meters, there will be a significant difference in the linear speed of the rotation of the human head and feet, which will directly cause the human head and feet to be under different levels of gravity.
In such a gravity environment, it is difficult to survive normally.
Because the gravity of the feet is high and the gravity of the head is small, it takes more force for the blood flowing to the feet to flow back to the head. And every time a person bends down and lowers his head, it will directly lead to a change in the gravity environment, so it is easy to get dizzy. To make these problems disappear completely, the diameter of the rotating system needs to be further expanded. With the current capabilities of mankind, it is very difficult to build a spacecraft with a diameter of 100 meters or even larger, and the cost of launching thousands of rockets just to ship the components that make up this spacecraft into space in batches is too high.