H-20 Aerodynamic Layout Could Exceed Expectations

According to the South China Morning Post, Chinese scientists have achieved a breakthrough in plasma stealth technology. A cluster of plasma can absorb, refract, or even alter the frequency of electromagnetic waves emitted by radar, leaving enemy radars bewildered. Stealth aircraft will no longer require complex stealth aerodynamic layouts and can be designed according to optimal aerodynamics at will. Netizens exclaimed that if the performance is indeed as good as claimed, the aerodynamic configuration of the H-20 might exceed everyone’s imagination!

China Breaks Plasma Stealth: Solving a Problem Baffling Global Scientists
The breakthrough in this research was reported by the Xi’an Aerospace Propulsion Institute Plasma Technology Center and the Key Laboratory of Plasma Physics and Applications in Shaanxi Province. This technology can make almost all military aircraft disappear from radar screens!

The report states that this technology can set up a plasma cloud on an aircraft, where radar echoes are most easily generated, eliminating the strongest signal reflection areas of military aircraft, such as radar domes, cockpits, or other areas most easily detected by enemy radar. It can be selectively covered or turned on and off at any time. In simple terms, it means stealth can be toggled on and off at will, which is truly domineering.

Tan Chang, who leads this research at the Plasma Technology Center of the Xi’an Aerospace Propulsion Institute under the China Aerospace Science and Technology Corporation, said that this technology solution will soon be applied to various military aircraft to meet China’s rapidly growing demand for superior military capabilities. The South China Morning Post called this plasma stealth technology a game changer. Now, let’s see just how formidable this game changer really is.

Plasma Stealth: Not a New Technology, but Solving Intractable Problems
According to the South China Morning Post, the author indeed found a paper titled “Study on Closed Electron Beam Plasma Characteristics” in the Journal of Radio Science, which provides a detailed description of the principles and solutions of this technology. Especially, the “closed electron beam plasma stealth technology solution” completely solves the problems that existed in previous plasma stealth technology solutions studied internationally.

Plasma is a familiar term to everyone. It is the fourth state of matter, beyond solid, liquid, and gas. It is a gas-like substance composed of positive and negative ions formed by atoms or groups of atoms after partial electron loss. The properties of this substance are very unique. Like gas, its shape and volume are not fixed and can change depending on the container.

Moreover, plasma has nearly perfect conductivity and can be controlled by magnetic fields. The so-called ion electric propulsion (rocket engine) utilizes the reactive force of plasma accelerated in a magnetic field to propel spacecraft forward. The nearly perfect conductivity of plasma encountering electromagnetic waves has fascinated scientists:

Plasma only reflects incoming low-frequency radiation. It interacts strongly with incoming radio waves, absorbing and converting electromagnetic waves into thermal energy. If the frequency of the radio waves is lower than the plasma frequency, they are reflected. If higher, they are transmitted. If they are equal, resonance occurs.

There is another mechanism to reduce reflection. If electromagnetic waves pass through plasma, are reflected by metal, and the power of the reflected wave is roughly equal to that of the incident wave, they may form two vectors. When these two vectors are phase-opposed, they cancel each other out, causing a significant attenuation of the radar signal. However, plasma also requires sufficient thickness and density.

Plasma surrounding aircraft can absorb incoming radiation, reducing the signal reflection of the aircraft’s metal components. Because the received signal is weak, it is invisible to distant radar. Additionally, plasma can be used to modify reflected waves to confuse the opponent’s radar system, such as shifting the frequency of reflected radiation, which will hinder Doppler filtering and make it difficult for the radar to distinguish between reflected waves and noise.

The most common real-world example is the plasma-enshrouded fireball when spacecraft re-enter the atmosphere. Radar has difficulty tracking it, and communication cannot be maintained because this layer of plasma not only blocks some signals but also changes the frequency of the signals passing through. This magical property results in complete communication blackout during this phase, commonly known as blackout.

Plasma Stealth Works So Well, Why Isn’t It Used?
The theory of plasma stealth was proposed as early as 1956 by Arnold Eldredge of General Electric. He proposed a “method and device for object camouflage using a particle accelerator to create an ion cloud” patent application for aircraft, which was granted U.S. Patent No. 3,127,608 in 1964.

Plasma stealth is indeed impressive, but the problems are challenging. Firstly, plasma itself emits electromagnetic waves similar to background noise. Secondly, plasma leaves a trail behind the aircraft, although tracking it is difficult, it’s theoretically possible. Thirdly, plasma emits fluorescence; while the radar is stealthy, it becomes visible optically. Fourthly, placing plasma generators around high-speed aircraft to produce enough radar stealth plasma is nearly an impossible task.

Countries have invested heavily in researching plasma stealth, but it has always remained in the laboratory stage and has never reached practical application. The U.S. military, which was initially very interested, lost interest later. Starting from the late 1970s, the United States shifted its focus to stealth from the perspective of coatings and airframe shaping. This led to the development of the F-117 and B-2 stealth bombers, and subsequently to the F-22, F-35, and the latest B-21 aircraft.

However, Chinese scientists have taken a different approach, pioneering the “closed electron beam plasma stealth technology solution” to solve the problems of plasma generation and maintenance. It involves placing a plasma hood in the required stealth position, where the plasma is generated and maintained within this enclosed area, unaffected by high-speed airflow. It also solves the problem of efficient plasma generation, significantly reducing the power generated by plasma and doubling the reaction speed.

In simple terms, using this technology can make aircraft stealthy on demand. Imagine an aircraft flying in the sky, suddenly disappearing from radar screens. This should be extremely shocking to observers. If one day the enemy air defense forces see the radar signals of a large number of aircraft suddenly disappear, they would probably be dumbfounded.

Game Changer: H-20 Aerodynamic Configuration Beyond Imagination
With the emergence of plasma stealth technology, some aerodynamic designs sacrificing stealth but still quite excellent can be resurrected. Why was the F-117 so strange? It had a faceted geometry, with each facet having an angle greater than 30 degrees to the vertical plane, because this way electromagnetic waves could be reflected away from threatening areas.

This was because the radar-absorbent coating technology at the time was inadequate, so this odd structure was used to compensate. This also resulted in poor flight performance of the F-117, with a maximum speed of Mach 0.92 and a range of only 1720 kilometers, and poor handling quality. Fortunately, it could refuel in the air and still carry out stable bombing missions.

After the breakthrough in stealth coating technology, the B-2 emerged. Strictly speaking, the external design of the B-2 bomber is quite cool—a tailless flying wing lifting body with a black paint scheme, indicating its formidable combat capability. If the author were to say that the aerodynamic layout is not good from an aerodynamic standpoint, many netizens would probably disagree. However, the B-2 sacrificed many flight qualities for stealth:

The flying wing’s flight qualities are not good (prone to pitching up);
Lack of vertical tail makes it prone to yaw; the fly-by-wire system uses speed brakes to maintain heading;
Considering stealth, the engine intake on the back of the aircraft is insufficient and needs auxiliary intakes;
The aerodynamic layout of the B-2 flying wing lift body has its center of gravity located ahead of the lift focus, so it cannot naturally recover when disturbed airflow causes an increase in angle of attack. It can only use flight control software to generate a nose-down moment on the control surface. Under normal circumstances, this wouldn’t be a problem, but during takeoff or landing, complex low-altitude airflow and ground effects can cause pitch instability, leading to a crash on the runway. The B-2 has experienced such accidents more than once, resulting in at least one being written off.

The YB-49 used small vertical tails, but directional stability was still poor.

Conventional aircraft have vertical tails, and early Northrop flying wings had vertical tails, and not just one, because the directional stability of tailless aircraft is difficult to maintain. For example, the YB-49 used four small vertical tails, but directional stability was still poor. The B-2 lacks a vertical tail to minimize the side radar cross-section, but solving the radar reflection problem has led to directional instability. However, the B-2 uses an electro-hydraulic control system that can control the control surfaces hundreds of times per second, opening left and right speed brakes to maintain heading stability. Please see the figure below:

The right speed brake is open, indicating a leftward deviation, which needs to be “pulled back.” Although the B-2 currently does not have significant heading stability issues, it’s like driving a car without a steering wheel and having to use left and right brakes to keep the vehicle straight. It’s likely that the drivers would curse the designers.

Another issue is the engine intake on the back. This was done to solve the problem of strong radar reflections from the belly intake duct, but the airflow here is affected by the aircraft’s back, and the B-2 also had to install a smaller intake for stealth, leading to insufficient intake. During takeoff with a significant angle of attack, the intake needs to be opened to increase the airflow.

The B-21 is even more radical, as it reduces the size of the intake by two sizes for the sake of extreme stealth, leading to even more severe intake deficiencies. Therefore, like the B-2, it also uses auxiliary intakes. Judging from the visual angle, the area proportion of the auxiliary intake seems to be even larger than that of the B-2.

If stealth is not a concern, these aircraft would not be designed like this. Classic structural aircraft are easier to accommodate bomb bays, and flight performance would be better. Even if extreme stealth design is desired, combining stealth design with plasma stealth could achieve even better stealth performance.

So when you understand the practical level of plasma stealth design, the aerodynamic layout of the PLA’s undisclosed H-20 might exceed everyone’s imagination again. Of course, it is possible that the aerodynamic layout may still be a flying wing, but the stealth performance may be 1-2 orders of magnitude higher than previously estimated. However, regardless of the design, we gladly accept it, as it means better performance!

If the H-20 has better performance, what about the 4.5th generation fighter jets?
China and the United States are the only two countries with fifth-generation stealth fighters. In addition to stealth fighters, both sides have a large number of non-stealthy fourth-generation aircraft or 4.5th generation fighter jets. For example, China’s J-16, which incorporates a large amount of fifth-generation stealth fighter electronic technology, can only be considered a 4.5th generation fighter jet due to the lack of stealth design. Now with this plasma stealth technology, installing a few stealth devices in key locations can immediately turn such 4.5th generation fighter jets into fifth-generation ones.

It’s no wonder the South China Morning Post defined it as a “game changer” because China has a large number of 4.5th and fourth-generation aircraft. If every fighter jet is as stealthy as the J-20, or even slightly less so, this massive quantity alone would overwhelm the U.S. military. For a military that values equipment like the U.S. Air Force and Navy, such technological improvements and increased quantity are undoubtedly shocking. (Xing Chen)

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