In Sichuan, China, Chinese scientists have opened a new high-powered wind tunnel that can simulate the most extreme flight conditions of any device of its kind on the planet. It is also the biggest known wind tunnel right now.
South China Morning Post (SCMP) suggests that the wind tunnel can reach speeds of 1.5 to 7.14 miles per second (2.5 to 11.5 km/s), or Mach 33. It is 80 centimetres wide, twice as big as the biggest high-speed wind tunnel that had been made before.
When a spaceship comes back into Earth’s atmosphere from orbit, it usually only arrives 17,500 miles per hour, called Mach 25.
So, the wind tunnel will be able to test weapons and vehicles that go faster than Mach 5 and spacecraft that can either come back to Earth or leave Earth’s gravity and land on other planets.
Lyu Zhiguo, who led a team at the Hypervelocity Aerodynamics Institute under the China Aerodynamics Research and Development Centre in Mianyang, told the SCMP that they had built the world’s largest free-piston driven expansion tube wind tunnel with high enthalpy. Enthalpy is the energy a thermodynamic system needs to stay together in relation to the air around it.
The ultra-high-speed tunnel is called a “free-piston driven tunnel.” Australian space engineer Raymond Stalker came up with this design in the 1960s as an alternative to the hydrogen-powered wind tunnels that were already in use. Stalker came up with a design that used nitrogen instead, which is much cheaper, and had a piston that fired quickly to make it go very fast.
Since the 1980s, Stalker designs have been made worldwide, but Lyu’s team says the Chinese design is better. This design reduces vibration, which makes measurements more accurate, uses a much stronger piston, can be used more than once, and costs less. But their tube still has the main problem of all Stalker wind tunnels: the effect only lasts a few thousandths of a second.
Beijing based 30 Mach tunnel
Another similar wind tunnel, called JF-22, will soon open in Beijing. It will be able to make speeds as fast as Mach 30. Han Guilai, a researcher at the Chinese Academy of Sciences, said in an online lecture in May 2021 that the JF-22 wind tunnel in Beijing’s Huairou district could reach 10,000 degrees Celsius (18,032 degrees Fahrenheit), which is hot enough to break air molecules into atoms and even give some of the atoms an electric charge.
He said the air is no longer the air we breathe in, adding that the flying vehicle they are studying is like swimming in mud.
Han, who works for China’s top hypersonic research agency, the Institute of Mechanics, said that the JF-22 wind tunnel would produce 15 gigawatts of power. This is almost 70% of the installed capacity of the world’s largest hydropower station, the Three Gorges Dam in China’s southwestern Sichuan province, or more than seven times the Hoover Dam in Nevada.
Aviation Industry Corporation of China (AVIC) has another smaller tunnel called the FL-64 with a diameter twice that of the institute’s first equipment while, on the other hand, under a total temperature of 900 Kelvin or 626.85 degrees Celsius, flight speeds from Mach 4 to 8 at an altitude of 48,000 metres can be simulated.
China and other major countries have put a lot of money into developing hypersonic flight technology, which could let planes land anywhere in the world in just one or two hours. It would also cut the cost of sending things into space by more than 90%, making it possible for more people to go into space.
China’s hypersonics pursuit
Beijing has put a lot of money into hypersonic technology. It has a few hypersonic weapons that could get past almost any air defence system. It has also put money into cargo and passenger travel designs at speeds above Mach 5. The fastest of these planes in use today doesn’t even reach Mach 1.
In the past few years, China is claimed to have used many kinds of hypersonic weapons, and the number of test flights they do in one year is equal to what the US does in ten years.
Chinese hypersonic test flights are said to have had a very high success rate and no crashes. In 2019, the Chinese government ran a secret test of what is thought to be a prototype space plane that can take off and land at a regular airport. Researchers have also written about hypersonic engine designs that have never been seen anywhere else in the world in domestic scientific journals.
Researchers in Beijing said they had successfully communicated with a hypersonic vehicle from the ground more than once. The breakthrough could help ground control avoid the “blackout” period that spacecraft go through during reentry, or it could let the military give precise orders to hypersonic weapons in mid-flight, including a “kill button” to stop the mission at any time.
China’s claims that its research in hypersonics is advanced partly because its wind tunnels use unique technology. In other countries, high-speed airflow is made with mechanical compressors. The JF-22, on the other hand, uses chemical explosions.
They also claim that China would be “about 20 to 30 years ahead” of the rest of the world with JF-22 tunnel, another existing facility JF-12, also in Beijing, and the newest tunnel.