On November 10, NASA announced that its independently developed and tested "inflatable reentry reducer" landing test was a complete success, and the inflatable heat shield was unfolded on orbit and landed safely in the predetermined sea area.
Before that, on the afternoon of May 5, 2020, when China launched the Long March 5B launch vehicle for the first time, it was also equipped with my country's " new generation manned spacecraft test ship " and "flexible inflatable cargo return cabin test cabin". Among them, the new generation manned spacecraft test ship returned to the ground safely and achieved a complete success. The flexible inflatable cargo return cabin test cabin had an abnormality during the landing process due to the drift of the landing site during the return process.
That is to say, the United States successfully verified the flexible inflatable return capsule technology this time, which really surpassed China in terms of test speed. I can’t help but ask : Why are China and the United States taking the lead in developing the "flexible return capsule" technology? Why did this technology be broken after 50 years? Is China really surpassed by the United States?
Why are China and the United States taking the lead in developing the "flexible return capsule" technology?
If the spacecraft wants to successfully enter the predetermined orbit, it must be the flight speed of the spacecraft exceeds the first cosmic speed of when the star arrow is separated, so the rocket must continue to accelerate, thus giving birth to a multi-stage rocket structure. Similarly, if a spacecraft wants to leave orbit, it is not a simple matter to return to the ground. Because when the spacecraft returns to Earth at extremely high speeds, the spacecraft itself will produce violent friction with the dense atmosphere, and eventually produces continuous high-temperature ablation of thousands of degrees on the surface of the spacecraft.
So in the 1960s, more than half a century after humans mastered the spacecraft return technology, humans have always been using conical structure + bottom insulation shield + ablation and cooling coating technology to protect the safe landing of return capsules. For example, my country's Shenzhou manned return capsules, Russia's Soyuz return capsules, the United States' Apollo, the manned dragon and other manned return capsules, as well as some unmanned return capsules, all of which use this traditional but mature and reliable space return technology. Although this conical structure + thermal insulation shield + ablation and cooling return technology is mature and reliable, it also has its own shortcomings such as self-weight, high cost, and single-use. In particular, this type of thermal insulation and cooling technology can only protect the return capsule from smoothly through the atmosphere and cannot have a positive effect on the safe landing of the return capsule. To this end, the return capsule also needs to have multiple super-large-area reduction parachutes + recoil rocket/ airbag to reduce the landing speed of the return capsule, which also makes the return capsule + recoil rocket + airbag buffer structure occupy a large amount of the internal space of the return capsule, and the super-large-area radiator also has the risk that the return capsule will be easily entangled + after landing, the return capsule may be dragged by the reduction parachute.
Therefore, in the 1960s, the United States proposed that if there could be a technology that actively wraps the body of the return capsule before the spacecraft leaves the predetermined orbit and enters the atmosphere, and at the same time, it uses its own expansion to generate greater flight resistance, thereby reducing the speed and frictional heat of the return capsule entering the atmosphere, and helping the return capsule to land smoothly on the ground, the conical structure, heat insulation shield, ablation and cooling that must be used when the spacecraft returns can be replaced, and this technology is called "inflatable flexible return capsule technology."
Its biggest advantage is not only to be able to protect the return capsule to land safely on the earth, but also has a major advantage. Compared with traditional heat insulation shields, this new structure of flexible inflatable return capsule not only does not restrict the return capsule structure, but also allows the return capsule to be designed and developed more openly according to aerospace needs. Before the flexible inflatable return capsule is itself a small size and lightweight airbag bag, so the small and light weight also makes it very advantageous in the field of aerospace , which focuses on lightness and heavyness. After all, the weight of aerospace launch determines the launch cost.Moreover, when this airbag bag is opened, it looks like an umbrella, and while wrapping the body of the return capsule firmly, the umbrella structure also makes its re-entry speed lower and has the advantage of reuse.
Especially the current new generation of manned spacecraft in China and the United States weighs more than 20 tons. If such a large mass is used, the recycling method of the insulation shield + reduction parachute will not only restrict the structure of the entire manned spacecraft return capsule and the insulation performance of will be hindered. At the same time, the most important thing is that the area of the deceleration parachute needs to be larger, but the number of umbrellas cannot exceed more than 4, otherwise it is very easy to entangle. Therefore, this is also the core reason why the two new generation of manned spacecraft in China and the United States are eager to test this flexible inflatable return capsule after the emergence of the two new generations of manned spacecraft in China and the United States.
Why has this technology been able to be broken after 50 years?
Although this flexible inflatable return capsule technology was proposed as early as the 1960s, the development of this seemingly simple inflatable airbag structure is not simple, because this inflatable return capsule must be filled with a large amount of gas before entering the atmosphere. If it is directly filled with air, it will definitely not work. After all, the content of oxygen in the air exceeds 21%, which is easy to detonate in the atmosphere with high temperatures of thousands of degrees, so it can only be filled with helium or nitrogen with good stability. However, how these two gases are compressed and compressed, it is very important to quickly fill the airbag in a short time.
Secondly, when this flexible inflatable return capsule reenters the atmosphere, not only will the surface of the flexible airbag be subjected to high-temperature friction to generate heat, but also affected by the increase of the earth's gravity and the increase of air density, the ablation resistance of the airbag surface of the flexible inflatable return capsule must be further improved, at least to ensure that it will not be compressed and exploded after filling a large amount of gas and is severely rubbed with the atmosphere at a high temperature. Therefore, it is necessary to develop a polymer composite material with a light texture, reusable and strong heat resistance.
So for countries that want to develop this flexible inflatable return capsule, in addition to solving the rapid injection of stable gas, thermal insulation and cooling of polymer materials, and airbag buffer shock absorption functions, it must also be able to ensure that it is small in size, light in weight, and has the function of reuse. Therefore, this is also the reason why this technology has not been successfully implemented for half a century.
Is China really surpassed by the United States?
If we talk about the development and testing progress of flexible inflatable return capsules, the United States had tried them as early as the 1980s. ESA also conducted many tests at the beginning of this century, but all failed without exception. Either they could not be quickly inflated in space directly, or they were inflated successfully and failed to return.
. my country conducted a flexible inflatable return capsule test chamber technology during the first flight of the Long March 5B in 2020. The final failure was the large-scale change in the landing location. The experiment has been successful in the core inflation and filling the atmosphere. I believe that with a slight improvement in the future, the probability of my country's success in conducting relevant tests will be very high.
Of course, the United States is the first to complete this experiment at this stage, which does not mean that the United States is at the forefront of China and surpasses China. At present, China and the United States are still in a state of progress, and the United States has only successfully tested it and has not really applied it to the process of returning manned spacecraft to the real world. , so who in the end will be the first to apply it to the actual space return depends on the progress of China and the United States.
