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In July 2023, China officially announced the good news that the JF-22 ultra-high-speed wind tunnel had passed the acceptance.
This is the world's most advanced ultra-high-speed shock wave wind tunnel, with a speed of up to Mach 30, which means that China has won another "world's best" in this aspect, and its technology is at least 30 years ahead of the United States.
But what exactly is a wind tunnel, and why is the JF-22 hypervelocity wind tunnel the cradle of hypersonic weapons and aerospace vehicles?
What is a wind tunnel used for?
When it comes to wind tunnels, everyone may feel relatively unfamiliar, NASA's definition of a wind tunnel is a large pipe with air flow inside, to put it bluntly, a wind tunnel is a hole that can produce air.
As we all know, whether it is developing an airplane, a missile, or a small golf ball, as long as it is related to air flow, it needs to be tested in the air.
It may be easier to test golf balls, after all, there are only a few kinds of weather that we can encounter on a daily basis, but it is different for large heavy equipment such as aircraft.
If you want to use a real environment, sometimes you have to go to space to measure, which is obviously unrealistic, so you need to have tools to simulate a variety of air environments, and wind tunnels are just that.
Wind tunnels can artificially form flowing gases, while control gases can be used to build different air environments, and can also simulate complex air environments, providing a place for aircraft and other tests.
Generally, a wind tunnel consists of a cave body, a drive system, and a measurement and control system, which usually form a fixed model, and then simulate different air environments by controlling gas changes.
However, there are some special wind tunnels, their models may change, but the gas is normal and unchanged, and this kind of wind tunnel is mainly used to study aircraft recovery.
Taking an airplane as an example, usually the shape of the aircraft is designed together with the internal system, but the shape design will be faster, so the shape should be tested first.
At this time, the internal parts of the aircraft may not have been assembled, and even if they have just been assembled, it is impossible for us to let the pilot drive a freshly assembled plane into the sky, and then the wind tunnel will be used.
In 1871, Winholm from England made a wooden box with two openings, which was the world's first wind tunnel, and it couldn't be simpler.
If you explain it this way, don't you think that the wind tunnel is not as tall as you think?
But the U.S. media doesn't think so, they think that the development of hypersonic weapons in the United States is not as fast as China's, precisely because the United States does not have a wind tunnel like China, why is this?
Wind tunnels directly determine the progress of hypersonic weapon research?
Based on wind speed, wind tunnels can be divided into low-speed wind tunnels, transonic wind tunnels, supersonic wind tunnels, and hypersonic wind tunnels, and the JF-22 mentioned at the beginning belongs to hypersonic wind tunnels.
Usually a hypersonic wind tunnel is a shock wave wind tunnel, which according to NASA's interpretation is a shock tube.
This type of wind tunnel works like placing a membrane in the middle of the tube to separate the tubes, and then filling one side of the membrane with high-pressure gas.
At this point, a large pressure difference forms between the two sides of the membrane, and when the membrane is torn, a strong air flow is formed.
Seeing this, I believe it is not difficult to guess the disadvantage of this kind of wind tunnel, that is, the time that lasts is fleeting.
Because membrane rupture is instantaneous, unless the membrane is constantly ruptured, it can only output a very short high-velocity airflow, but the airflow output of a shock wave wind tunnel will be much faster than other types of wind tunnels.
At present, the JF-22 can last up to 40 milliseconds, although this is only a blink of an eye, but it is a well-deserved first in the world.
Generally, the greater the speed of the test object, the greater the speed of the wind tunnel, so it is not difficult to conclude that the JF-22 hypersonic wind tunnel is tailor-made for hypersonic weapons.
Hypersonic weapons are a new concept that has often emerged in recent years, but many people may still be unfamiliar with this emerging weapon.
In fact, hypersonic weapons are a general term for weapons that fly faster than 5 times the speed of sound, which is equivalent to such weapons can move 6,000 kilometers per hour.
You must know that the current speed of high-speed rail is about 300 kilometers per hour, which shows that the advantage of hypersonic weapons in flight speed is very prominent, so the existing air defense system cannot intercept this weapon.
However, as an emerging weapon, the hypersonic flight technology it uses is also relatively immature, and flight stability is one of the main problems.
The solution to this problem is to use a wind tunnel to continuously test this technology.
In addition, according to the current design concept, the flight path of hypersonic missiles is to enter the atmosphere first to avoid interception, and then re-enter the atmosphere.
Wind tunnels can simulate the environment in which hypersonic missiles re-enter the atmosphere, which shows that wind tunnels are indispensable for the development of hypersonic missiles.
In fact, China, the United States and Russia are now researching hypersonic flight technology, but even the chief scientist of the US Defense Intelligence Agency admits that China is the leader in this area because it has better infrastructure than the United States and Russia, namely wind tunnels for testing.
There is a reason why the United States is so popular, as early as 2012, we developed the largest wind tunnel JF-12, and the JF-22, which just passed the acceptance last year, is the most advanced wind tunnel in this field.
With a length of 167 meters, the JF-22 can simulate a flight environment with an altitude of 40-90 kilometers and a speed of 30 times the speed of sound (equivalent to 10 kilometers per second).
For example, JF-22 can form a flow field with a diameter of up to 2.5 meters, while the most advanced wind tunnels abroad can only generate a flow field of 1.5 meters, but what is the use of this advantage?
In fact, it is not difficult to understand that the larger the flow field, the larger the aircraft, which determines that the JF-22 may be used to test aerospace aircraft.
Researchers on the project have revealed that they are working on a two-stage or multi-stage vehicle into orbit.
To put it simply, the two-stage orbit is to let the rocket first send the aircraft to the altitude where the first orbit is located, and then release the second stage to let it continue to fly upward on its own power system.
The principle of this kind of aircraft is very similar to the design of the aerospace aircraft, which is also sent to a certain altitude by a rocket, and then separated from the rocket and continues to fly upward by its own power.
This relay method is equivalent to lowering the threshold for launching space planes or other spacecraft, and it may be possible to launch anywhere in the future.
In addition to research vehicles, wind tunnels can also be used for hypersonic engine experiments.
The laboratory working on the JF-22 is currently working on a stationary oblique explosion engine, a hypersonic engine that is more than half as efficient as existing engines and can steadily output heat.
Engines have always been a relatively weak field in the mainland, and if there is such an engine, it will be of great significance to the mainland's research on manned spacecraft, aerospace aircraft, and even ordinary fighter planes.
China's wind tunnel lead is just blowing?
In fact, in recent years, many so-called media experts in the United States have questioned that China's research on wind tunnels is for "self-boasting", saying that the research of Mach 30 wind tunnels can only be used to travel to and from other stars, such as the moon, which is actually useless, but is this really the case?
Obviously, this statement is typical of not being able to eat grapes and saying that grapes are sour, because wind tunnels can truly simulate a hypersonic environment.
In fact, many countries, such as the United States, have been conducting wind tunnel testing for a long time.
As early as the sixties and seventies of the 20th century, most of the American spacecraft began to be tested in the wind tunnel, but the test speed of the wind tunnel could only reach Mach 3.5 at the highest, and now the fastest shock wave wind tunnel in the United States is about Mach 7.
Because the speed of the wind tunnel has been difficult to meet the demand, the United States has later used more software to carry out hypersonic testing, but the software is always virtual, and there is no way to simulate the real environment.
Now that the Pentagon is also aware of the limitations of the software and is starting to think about testing directly by flying, this is clearly putting the cart before the horse.
Because for example, in the case of a second orbit, it will be much easier to test what conditions are suitable for aircraft separation, and then fly according to these data.
If we look at it this way, it is not unreasonable for us to be ahead, and being able to show advanced technology generally means that more advanced technology may be researched.
As you can imagine, this time we are not a little ahead.