Chinese researchers use a wind tunnel to mimic hypersonic bombing

Military researchers have been examining the capability of bombers jets to dump payloads in wind tunnel since the 1960s.
Baba Tamim
Prototype aircraft in a wind tunnel.
Prototype aircraft in a wind tunnel.

XH4D/iStock 

Chinese researchers claim to have created the most sophisticated method in the world for testing an aircraft's capacity to discharge a weapon or tiny spacecraft at very high speeds.

The technique has enabled scientists to test a hypersonic bomber prototype in the wind tunnel.

The research team claimed to have built a hypersonic captive trajectory system (CTS) that uses two robotic arms to hold and tilt a prototype aircraft and its cargo, allowing them to pitch, rotate, and roll in nearly all directions, reported South China Morning Post (SCMP) on Friday.

"During an experiment in a one-meter-wide (3.3 feet) wind tunnel, the upgraded device allowed the Chinese researchers to simulate offloading cargo at Mach 6 – six times the speed of sound – and obtain data with unprecedented detail and accuracy," according to a study cited by SCMP that appeared in the Chinese journal Acta Aerodynamica Sinica on Monday.

New hypersonic CTS

The first CTS capable of operating in a hypersonic wind tunnel against intense, rapid shock waves was created by Lin Jinzhou's team in 2017. Now again, his team from China's Aerodynamics Research and Development Center claims the new hypersonic CTS.

The paper claims that the new system is a significant improvement over Lin's earlier one-armed CTS.

The two robotic arms have a combined 12 degrees of freedom, or independent joints, which is twice as many as in earlier studies. This enables researchers to model practically any separation-related phenomena.

Military researchers have been examining the capability of bombers and other military aircraft to dump cargo in wind tunnel testing since the 1960s using a device known as CTS.

For the systems to simulate the separation of two objects against high currents in a wind tunnel, a tiny crane is often used to lift the bomb or missile away from an aircraft.

Since similar wind tunnel tests carried out in other nations often required one component - typically the airplane - to stay put, this finding propels China ahead in the quest to reach hypersonic speeds. And while this hypersonic flight exceeds Mach 5, these other tests were carried out at lower speeds, noted SCMP.

"So far, the CTS tests available in other countries support one-body movement only. In the hypersonic range, there is no report of CTS being used at all," according to Lin and her coworkers.

Dangers of Mach 6 speed

Chinese researchers use a wind tunnel to mimic hypersonic bombing
Airplane design on the virtual reality simulator, stock photo.

However, Lin cautions that separating the aircraft from its payload at such high speeds could be risky.

"Whether the storage can be safely separated from the aircraft becomes a big problem," she said.

Shock waves, vortexes, and other airflow patterns may form when a hypersonic aircraft separates from another item due to the high speed and pressure, which can increase the likelihood of a collision between the plane and its cargo.

Wind moving at such a high speed can create explosion-level shocks. The robotic arms have to be able to proceed with an inaccuracy of one micrometer or less. At the same time, it also has to withstand repeated shocks for close to a minute.

Chinese researchers had to create novel sensors, computer algorithms, and ultrafast communication systems to overcome these obstacles.

"During the Mach 6 experiment," the team "observed the formation of shock waves between the hypersonic aircraft and separating cargo. These shocks bounced back and forth between the surface of the two bodies, causing the cargo to lose speed and assume an unexpected pitch that could lead to a collision with the aircraft," said Lin.

The airplane rolled into an uneven position due to several shocks that also went sideways.

However, "by carefully adjusting the relative movements of the aircraft and its cargo," the researchers said, "they could find a safer way to offload under various flight conditions."

China is working on a two-stage transportation system that will travel anywhere on Earth in under one hour.

The system seeks to use a big hypersonic aircraft to transport a weapon or vessel with passengers at a very high speed, then release them at a near-space altitude so they can glide from one continent to another.

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