Hypersonic missiles flying through a thin atmosphere can readily ionise the surrounding air, leading to a telemetry blackout. In May 2022, Xidian University’s National Near Space Ultra-High Speed Target Plasma Electromagnetic Science Experimental Equipment Project was approved that used an experimental apparatus with which the Chinese scientists claim to have made a breakthrough in the theory and fundamental technology of information transmission under the plasma sheath. This technological advancement will assist spacecraft, hypersonic aircraft, and hypersonic weapons to overcome blackouts and achieving wireless communication and detection.
The National Near Space Ultra-High Speed Target Plasma Electromagnetic Science experimental equipment is intended to address the blackout phenomenon, a technical challenge faced by high-speed aircraft such as ballistic missiles, spacecraft, hypersonic aircraft, and hypersonic missiles flying in near space. Near space refers to the altitude between 20 and 100 kilometres above the Earth’s surface. When travelling at hypersonic speeds in this space, the friction between the thin air and the hypersonic vehicle’s surface can induce ionisation, resulting in the formation of a plasma layer known as the plasma sheath. This plasma sheath can absorb radio signals, resulting in a cessation of radio communication and radar detection.
The hypersonic aircraft’s surface air is readily ionised, forming a plasma sheath and a blackout. Professor Bao Weimin, an academician of the Chinese Academy of Sciences and the dean of the School of Space Science and Technology at Xidian University led a team to overcome technical challenges in collaboration with Zhejiang University, Hefei Institutes of Physical Science of the Chinese Academy of Sciences, Harbin Institute of Technology, Air Force Engineering University, Beijing Institute of Telemetry Technology, and other universities and research institutions. Between 2017 and 2022, they successfully created China’s first high-speed target plasma electromagnetic science experimental device. Since its operation, they have rapidly replicated the blackout phenomenon from the L to the Ka-band on the ground and proposed a new low-frequency electromagnetic wave and dynamic adaptive anti-blackout communication method.
The experimental results indicate that when plasma covers the communication antenna, the system can detect changes in the plasma in real-time based on standing wave detection and automatically switch the communication rate between 4Mbps and 250bps, achieving an additional gain of approximately 40dB, which increases the tolerance limit of the communication system to plasma density by at least an order of magnitude. In other words, even if the plasma density exceeds the critical value of the black barrier by more than a factor of ten, continuous communication can still be maintained so long as the minimum information rate is maintained. A breakthrough has been reached in the theory and key technology of information transmission under the plasma sheath of the critical black barrier zone and severe black barrier zone of high-speed aircraft.
At the same time, another team led by Yao Jianquan from Tianjin University in China expanded the technical research in this field. It surmounted the technical issue of communication interruption under hypersonic flight conditions at five times the speed of sound or higher. The laser Yao Jianquan’s team developed can generate terahertz-frequency electromagnetic pulses with a continuous waveform. Continuous electromagnetic waves in the terahertz frequency range can be used for 6G communication and readily penetrate plasma equivalent to the Mach 10 flight. This technology increases the wireless frequency spectrum capable of penetrating the blackout barrier from the L-band to the Ka-band. This technology enables high-speed wireless communication and radar detection to penetrate the blackout barrier.
As a result of these scientific advancements, the Chinese Shenzhou spacecraft will no longer experience communication disruptions during its return to Earth. Thus, astronauts can maintain radio contact with the Earth in real time, and ground-based tracking radars can track the Shenzhou spacecraft without losing sight. It also means that China’s DF21D, DF F26, DF27, and other ballistic anti-ship missiles can track maritime targets continuously without losing track. This allows continuous tracking and significantly improves target detection and data link signal transmission capabilities.
With a larger communication bandwidth, the missiles can obtain more target images. Using the terahertz frequency band can significantly improve the communication bandwidth and enable SAR synthetic aperture radar guidance heads to obtain higher-resolution radar images of sea surface targets, achieving more precise target identification. Even target images can be transmitted back in real-time, allowing the rear command centre to obtain more detailed target information. In the future, Chinese situational awareness capabilities in targeting carrier strike groups will be greatly enhanced. Chinese generals can see detailed information on the carrier formation and identify each ship’s size and shape. They can distinguish which target is the carrier, the supply ship, and the escort vessel. They can even see the operation of carrier-based aircraft on the carrier deck. With this information, China can better plan its attacks and provide more powerful information assurance for its ballistic missile strikes against carriers.