Earlier this month, solar activity was intense, with 10 X-class flares and more than 60 M-class flares erupting in just one week, an outbreak of unprecedented intensity and frequency in history. With the frequent eruptions of solar activity, from the night of May 10 to the early morning of May 11, the Earth's magnetic field erupted into a very geomagnetic storm (kp=9). At that time, there were extremely gorgeous aurora in many areas, including Mohe in Heilongjiang and some areas in Xinjiang.
The most intuitive manifestation of the geomagnetic storm phenomenon caused by solar activity is the occurrence of the aurora phenomenon, in addition to short-wave communication and navigation and positioning. Under normal circumstances, the occurrence of geomagnetic storms does not have much impact on the lives of ordinary people, but it has a greater impact on spacecraft operating in low-earth orbit.
The Chinese space station is declining at an accelerated rate
Because when the geomagnetic storm phenomenon occurs, the density of the upper atmosphere will increase, resulting in an increase in the air density of low earth orbit, and the spacecraft operating in low earth orbit will have the problem of flight speed decrease because of the need to face greater air resistance, and the flight orbit altitude will also accelerate the attenuation along with the decrease in spacecraft flight speed. That is, under the influence of the phenomenon of geomagnetic storms, the speed of the spacecraft in low-earth orbit decreases, and the altitude decreases.
There are many spacecraft flying around the Earth in low earth orbit, among which the International Space Station and the Chinese space station are manned spacecraft, both of which are orbiting in circular orbits of about 400 kilometers, but under the influence of geomagnetic storms, their flight orbits have declined, among which our space station fell by almost 1 km on May 11, and the orbital altitude of the International Space Station also dropped by more than 0.5 km on the same day. In other words, under the influence of geomagnetic storms, the altitude decline rate of China's space station and the International Space Station has accelerated.
In the recent past, solar activity has been more frequent, and now it is just in the 25th solar activity cycle peak year, which means that in the future, solar activity will be very frequent, the probability of X-class flares will increase, and the trend of strong geomagnetic disturbance (Kp≥7) will increase. And these solar activities may affect the earth, affect the flight of spacecraft, and some netizens may begin to worry about whether our space station will continue to drop in altitude due to frequent solar activities, and then fall into the atmosphere and burn up.
Theoretically, a spacecraft flying in low Earth orbit will always fly around the Earth, but in practice it is not so simple, and the spacecraft will not fly around the Earth forever without falling. Because there is still thin air in low earth orbit, which means that air resistance is not negligible, the longer the flight time, the slower the spacecraft will be, the flight altitude will continue to decrease, and finally re-enter the atmosphere, orbital altitude attenuation is inevitable.
Regardless of whether it is the Chinese space station or the International Space Station, the design life is very long, generally can operate for more than ten years, through the maintenance, replacement, and upgrade of the module, the operation time of the space station can continue to be extended.
Without intervention, these space stations will not fly for such a long time, because the space station assembly is very large, the "windward side" is very large, and the air resistance faced is much greater than that of ordinary satellites, so the flight altitude of the space station is seriously attenuated.
But in order to make these space stations run longer, every once in a while, the spacecraft and engines of the space station will start to accelerate to increase the altitude of the flight orbit. In this way, the problem of altitude attenuation of the space station due to air resistance, gravity, and other factors is offset. By increasing the altitude of the flight trajectory, the space station assembly can be allowed to fly for a longer period of time.
It is undeniable that during the eruption of solar activity, it may affect spacecraft in low-Earth orbit, causing their flight altitude to drop rapidly, and stronger radiation may also affect astronauts, but the impact on manned spacecraft such as the space station is actually controllable.
Because there will be some areas within the space station that are more protected, astronauts can enter those areas that are more protected during solar outbreaks. And after the end of the solar activity, the space station can consume its own fuel to raise the orbit and avoid falling into the atmosphere and burning up. So, you don't need to worry about it at all.
Why doesn't the space station fly higher
Seeing that during the operation of low earth orbit, spacecraft such as space stations and satellites are still facing the problem of air resistance, some netizens may have such and such questions: Why do China's space stations and the International Space Station fly at an altitude of about 400 kilometers, instead of flying higher? If you fly higher, the air resistance will be less, and won't that help the space station fly longer?
There is a reason why the flight altitude of China's space station and the international space station are controlled at about 400 kilometers. The selection of the flight altitude of the space station involves two important "lines", that is, the Kármán line and the Van Allen radiation belt, of which the Kármán line is about 100 kilometers above the ground, and after more than 100 kilometers, the air density is extremely thin, which is considered to be the dividing line between the atmosphere and outer space.
Theoretically, the farther away from the Earth's surface, the lower the density of the air and the less air resistance it will be, but this is not to say that the higher the altitude of the space station, the better. Because it cannot exceed the 600-kilometer Van Allen radiation belt, this can be considered the "upper limit" of the flight altitude of manned spacecraft in low-Earth orbit.
The Van Allen radiation zone is divided into an inner zone and an outer zone, where the height of the inner zone is an area of 600-5000 km above the ground, while the outer zone is an area of 13000-20000 km above the ground. In these areas, there will be a large number of high-energy charged particles captured by the Earth's magnetic field, which will cause great harm to spacecraft.
Ordinary satellites and probes operating in this area are not very problematic, but if manned spacecraft operate in this area, especially the space station, the safety of astronauts and space stations will be threatened if they are in a strong radiation environment for a long time.
As for why the low-earth orbit at an altitude of about 400 kilometers was chosen as the flight orbit of the space station from a range of 100-600 kilometers, in addition to the objective factors mentioned above, the earth's gravitational attraction and rocket carrying capacity were also taken into account, and finally scientists chose to let the space station operate at an altitude of about 400 kilometers above the ground.
Shenzhou-19 is on standby
Due to the operation of low earth orbit, the space station spacecraft will face a variety of inevitable problems, in addition to the geomagnetic storm phenomenon caused by the space station assembly flight altitude accelerated decline, the space station will also face the threat of space particles or space debris, cosmic radiation will also affect the astronauts' bodies to a certain extent.
In such a situation, there is no way to ensure absolute safety in spaceflight. In order to ensure the safety of astronauts during orbital flights, we need to prepare in many ways.
One of them is that rockets and spacecraft adopt the mode of "sending one and preparing one". In other words, when there is a Shenzhou manned spacecraft on a mission in the Chinese space station, there will be a Shenzhou spacecraft on standby on the ground.
Now it is the Shenzhou 18 spacecraft that is flying on the Chinese space station, the Shenzhou 19 spacecraft is on standby, and when the Shenzhou 19 spacecraft is launched, the Shenzhou 20 spacecraft is on standby.
The reason why a new spacecraft is put on standby is actually for the safety of astronauts. If the space station or spacecraft encounters an emergency during the orbital flight, for example, if the spacecraft or space station is damaged due to the impact of large space junk, and the astronauts need to quickly evacuate from the space station and return to Earth, the spacecraft in the standby state can be launched in the shortest possible time to carry out rescue missions in space.
Spacecraft and rockets on standby are actually standing at the launch site. If we don't use this model, in case we have to prepare the spacecraft and rockets in case of an emergency, it will take a long time to launch the spacecraft to carry out the rescue mission.
Of course, the Shenzhou-19 spacecraft is on standby, which is just a normal operation, not that our space station has encountered an emergency, and everyone does not need to worry. This is from the launch of the Shenzhou 12 spacecraft, such a mode has been adopted, which is a normalized operation.
Although there are still more than five months before the launch of the Shenzhou-19 spacecraft, the spacecraft and rockets are ready, and the astronauts participating in this mission have already been determined, and they are now participating in relevant mission training. Which astronaut do you think will be the commander of this mission?