China now has the world’s most powerful hypersonic wind tunnel

[beijingwalker]

China now has the world’s most powerful hypersonic wind tunnel​

• The ‘world-leading’ JF-22 can simulate extreme flight conditions at Mach 30
• Facility will play key role in developing Beijing’s hypersonic weapons programme and passenger air travel

Published: 10:00pm, 6 Jun, 2023

The JF-22, located in Beijing, can simulate extreme flight conditions at 30 times the speed of sound. Photo: handout

After five years of construction, the most powerful wind tunnel on the planet has roared to life in China’s capital – a facility that will be key to advancing Beijing’s hypersonic ambitions.

Located in the mountainous Huairou district of northern Beijing, the JF-22 wind tunnel is 4 metres (13 feet) in diameter and can generate air flow speeds up to 10km (6.2 miles) per second, according to a final evaluation conducted on May 30.

That makes it the largest and fastest wind tunnel in the world, capable of simulating hypersonic flight conditions up to Mach 30, according to the Institute of Mechanics, the owner of the facility.
The tunnel will “support the research and development of China’s space transport system and hypersonic aircraft,” the institute said in a statement on Friday.

By comparison, the Mach 10 tunnel at Nasa’s Langley Research Centre in the United States, a primary hypersonic test facility, has a test section diameter of nearly 0.8 metres.
A larger test section enables researchers to put larger aircraft models or even an entire weapon into the wind tunnel to obtain more accurate flight data.

Most intercontinental missiles are under 4 metres in diameter.

The JF-22 is integral to goals set out by the Chinese government to be achieved by 2035. By then, Beijing hopes to deploy a fleet of hypersonic aircraft that can carry thousands of passengers into space each year, or reach anywhere on the planet within an hour.

But such aircraft must be able to withstand the extreme heat and pressure of hypersonic flight, while maintaining stable flight trajectories and a safe, comfortable environment for passengers.

At five times the speed of sound, air molecules around an aircraft begin to become highly compressed and heated, leading to a phenomenon known as molecular dissociation.

The air molecules break apart into their constituent atoms, which can then react with each other to form new chemicals.

Understanding the complex physics of flows associated with molecular dissociation is crucial for the development of hypersonic aircraft, according to the institute.

By studying the phenomena in a laboratory environment using facilities like wind tunnels, researchers can learn how hypersonic vehicles interact with their surrounding environment, and develop new technologies to improve their performance and safety.

Wind tunnel testing can also help identify potential problems or design flaws before the vehicle is actually built and flown, reducing the risk of failure or accidents.

According to some estimates, simulating the conditions of a Mach 30 flight inside a large tunnel, requires power comparable to that produced by the Three Gorges dam – a practical impossibility.

So, Professor Jiang Zonglin, the lead scientist for the JF-22 project, came up with an innovative solution.

To create the high-speed air flow needed for hypersonic testing, Jiang proposed a new type of shock wave generator called a “reflected direct shock wave driver”.

In traditional hypersonic wind tunnels, air flow is generated by a process called “expansion,” in which high-pressure gas is rapidly released into a low-pressure chamber, creating a supersonic flow. However, this method has limitations when it comes to generating the extremely high speeds and temperatures needed for hypersonic testing.

Jiang’s reflected shock wave driver overcomes these limitations by using a series of precisely timed explosions to generate a series of shock waves that reflect off each other and converge at a single point.

The resulting intense burst of energy is used to drive the air flow in the wind tunnel at extremely high speeds.

The innovation has paved the way for more advances by bringing more accuracy and efficiency to the study of hypersonic flight, according to the institute.

Using explosives to generate energy in a wind tunnel comes with lots of drawbacks – they are dangerous for both humans and equipment, and they produce noise and air pollution.

But an explosive shock tunnel allows for a very rapid and intense burst of energy, necessary for driving the air flow in the wind tunnel at extremely high speeds.

And because the energy source is generated by explosions rather than a fixed mechanical system, the intensity and timing of the explosions can be tailored to create a variety of air flows for testing different types of vehicles or materials.

A team of 16 independent experts hired by the National Nature Science Foundation of China evaluated the JF-22 in several key areas, including effective testing time, total temperature, total pressure and nozzle flow field size.

They concluded that the JF-22 had achieved “world leading” performance. “The JF-22 wind tunnel, together with the JF-12 wind tunnel, forms the only ground-based experimental platform that covers all flight corridors for near-space vehicles,” the institute said.

The JF-12 wind tunnel, which has been operating since 2012 at the same site as the JF-22, is designed to simulate flight conditions for vehicles travelling at speeds up to Mach 9.

Together, the two wind tunnels can be used in a variety of ways to test hypersonic weapons and aircraft – the JF-12 simulates flight conditions at lower speeds and temperatures, while using the JF-22 replicates more extreme conditions at higher speeds and temperatures.

By combining the data, researchers can better understand how different materials and designs perform under a range of flight conditions, and use that information to improve the performance and reliability of hypersonic weapons or aircraft.

The facilities could put China years ahead of its competitors, according to Jiang’s team.

China now has the world’s most powerful hypersonic wind tunnel

The world-leading JF-22 can simulate extreme flight conditions at Mach 30 and will play key role in developing Beijing’s hypersonic weapons programme and passenger air travel.

www.scmp.com

 

[beijingwalker]

China’s JF-22 hypersonic wind tunnel blows by US​

World’s most powerful wind tunnel can generate air flow speeds of 10 kms per second and could rapidly advance China’s hypersonic ambitions
June 7, 2023

The JF-22 wind tunnel can simulate the environment in which a spacecraft re-enters the atmosphere. Photo: China Central TV

China’s self-developed JF-22 wind tunnel is ready for hypersonic tests after passing a final evaluation conducted on May 30.

Based in the mountainous Huairou district north of Beijing and reputedly the world’s fastest, the wind tunnel can simulate the environment in which a spacecraft re-enters the atmosphere, according to Chinese physicists quoted in media reports.

The National Natural Science Foundation of China, managed by the Ministry of Science and Technology, recently held a meeting at the Chinese Academy of Science’s Institute of Mechanics in Beijing, China Central TV reported on Monday.

During the meeting, scientists confirmed that the JF-22 detonation-driven high-enthalpy shock tunnel project’s performance indicators including effective test time, temperature, pressure and nozzle flow had achieved international standards.

“The goal of the JF-22 wind tunnel is to accelerate the development of a space-to-earth shuttle system,” said Jiang Zonglin, a researcher at the Institute of Mechanics and head of the wind tunnel project. “If successful, the facility can also help reduce the cost of launching satellites and spacecraft by 90%.”

The JF-22’s construction began in 2018 and was completed in August 2021, according to state media. The tunnel has a length of 167 meters and diameter of four meters with an air flow range of three to 10 kilometers per second.

That makes it the largest and fastest wind tunnel in the world, capable of simulating hypersonic flight conditions up to Mach 30, or 30 times of the speed of sound, according to the Institute of Mechanics, the owner of the facility.

CAS researcher Han Guilai said in a lecture in 2021 that the JF-22 has the capability to simulate hypersonic flight conditions up to Mach 30 and could sustain such a runtime for an average of 130 milliseconds. LENS II, believed to be the most advanced wind tunnel in the United States, can only reach Mach 7 with a runtime of 30 milliseconds.

Han said then the JF-22, together with China’s JF-12 wind tunnel, would put China “about 20 to 30 years ahead” of the West. The JF-12 passed an acceptance check in May 2012 and can simulate flights of up to Mach 7.

Hypersonic competition​

However, Chris Combs, an expert in hypersonic and aeronautical engineering, told EurAsian Times that China’s JF-22 claim ignores the “presence of a wide variety of decades-old facilities around the world.” He said several wind tunnel facilities around the world had already achieved speeds of Mach 20 and above.

Combs said Mach 30 speeds are only seen “during extraterrestrial return (Moon, Mars, etc.)”, meaning that “until they start launching missiles from the Moon, this isn’t even really military.”

He also pointed to problems with detonation-driven shock tunnels, stating that they “alter the air chemistry to the point that the aero will no longer be representative of flight.”

The JF-12 hypersonic wind tunnel in Beijing pictured here has about one-fifth of the power output of the new JF-22. Photo: Handout
During the 1960s and 1970s, all NASA space shuttles and space launch systems were tested in the California-based Unitary Plan Wind Tunnel at the NASA Ames Research Center. The tunnel could only reach Mach 2 to 3.5. More tests were conducted by digital simulation with computational fluid dynamics (CFD) software.

Due to a lack of hypersonic wind tunnels, the US Department of Defense’s Defense Innovation Unit has reportedly considered skipping wind tunnel tests and instead getting data directly from actual flight testing.

An unnamed DIU spokesperson told Breakingdefense.com last September that the DIU is seeking commercial partners to demonstrate a test aircraft prototype that can fly and maneuver at greater than Mach 5, the minimum speed of hypersonic planes and weapons.

“I was surprised to know that the DoD wants to skip the wind tunnel tests and directly launch its hypersonic planes,” a Zhejiang-based columnist wrote in an article last September. “Such a practice violates the general procedures of scientific research.”

He said only wind tunnels, not software, can simulate actual hypersonic environments. He added that a wind tunnel with Mach 33 capability is useful as space shuttles will eventually re-enter the atmosphere at the “escape velocity” of 11.2 kilometers per second without deceleration.

However, a popular IT vlogger known as GeekLead said in a June 2020 video that China chooses to invest in wind tunnels because it lacks its own CFD software. He said senior Chinese officials usually favor investments in hardware over software as they prefer to see tangible results.

Other commentators claimed the US uses digital simulation of hypersonic tests but to date they haven’t worked as well as old-fashioned wind tunnels.

China’s JF-22 hypersonic wind tunnel blows by US

China’s self-developed JF-22 wind tunnel is ready for hypersonic tests after passing a final evaluation conducted on May 30. Based in the mountainous Huairou district north of Beijing and reputedly…

asiatimes.com

 

[JSCh]

JF-22 hypersonic wind tunnel :
Diameter: 2.5 meters
Length: 167m
Temperature range of hypersonic flows: 2500°C to 18000°C
Air flow speed: Mach 5 to 30
Simulated altitude: 25 to 90km
Simulation duration: 40ms at Mach 10

https://twitter.com/x/status/1680594474638950400