During the process of pursuing full-domain stealth capabilities in fifth-generation fighter jets, a seemingly minor yet crucial technology—flexible skin—has become a key factor in distinguishing the level of stealth. China has already widely applied this technology on the J-20, improved J-20A, and even the next-generation fighter J-35, achieving a radar stealth breakthrough for body gaps. In contrast, American fighter jets have remained largely dependent on traditional mechanical cover plate solutions, already lagging behind in the pursuit of ultimate stealth.

Fighter aircraft are covered with control surface joints, compartment gap, and maintenance ports, which can become strong sources of radar wave reflection. Traditional stealth design mainly focuses on overall shape and radar-absorbing materials, but often fails to adequately address the gaps caused by moving mechanisms.

The flexible skin technology embeds conductive elastic materials into a high-strength fiber matrix, forming a skin that can continuously deform with the movement of control surfaces. This "seamless" coverage of control surface junctions physically eliminates radar wave scattering caused by mechanical gaps.

Radar stealth for fighter aircraft is not just about front-side stealth or direct radar hits. When radar waves hit from the side or oblique angles, they create electromagnetic waves that "crawl" along the fuselage surface, known as "crawling waves." When these crawling waves encounter gaps, steps, or other discontinuities, they scatter strongly, greatly increasing the aircraft's radar cross-section in the side and rear directions.

The flexible skin significantly suppresses discontinuous scattering caused by crawling waves at the root of flight control surfaces (such as flaps, ailerons, and rudders), greatly enhancing the survival capability of the aircraft in all-directional radar threat environments.

The J-20, as China's first stealth fighter, already paid attention to managing gap stealth during its prototype stage. The mass-produced version, especially the J-20A, extensively used flexible skin technology on movable parts such as the leading and trailing edges of the wings, belly fins, and inlet adjustment plates.

From parades and public images, it is visible that the J-20's wing-body connection and the root of the all-moving vertical tail show almost no obvious gaps, demonstrating an extremely high level of process consistency. Its next-generation J-35 and Chengdu's next-generation fighters also continue this technological path, indicating that China has systematically mastered and promoted this technology.

In contrast, both the F-22 and F-35 in the United States still generally use the traditional mechanical stealth design of "metal cover plate + serrated edge" for their flaps and spoilers. Although this structure offers some shielding effect, it cannot completely eliminate gaps, and tends to wear and change gaps due to repeated operations, causing the actual stealth performance to degrade over time.

The high complexity and lifecycle cost of the F-35 are partly due to its extensive use of precision mechanical cover plate structures, requiring frequent disassembly and calibration during maintenance, further increasing the logistical burden.

Aside from improving stealth performance, flexible skin also brings aerodynamic and weight reduction benefits. Removing excess mechanical cover plates, screws, and actuation mechanisms significantly reduces the weight and complexity of the flight control system, improves the smoothness of the aerodynamic shape, and indirectly enhances maneuverability and range.

China has already applied this technology on a large scale in its next-generation aircraft and expanded it to unmanned aerial vehicles and hypersonic flying vehicles, forming a complete design-manufacturing-testing system. The mature application of flexible skin technology in China's stealth fighters is not only a technological advancement, but also reflects a forward-looking approach to stealth design: from "shielding gaps" to "eliminating gaps."

Although the United States experimented with similar concepts on aircraft like the EF-111, it never made it a standard technology for fifth-generation fighters. Now, returning to this path on a series of already finalized fighter jets would mean significant retrofitting costs and technical risks.

When the J-20A cruises through the airspace with a nearly seamless flying wing configuration, it represents not only a step ahead in stealth technology, but also the most fundamental aspect in the competition for the next generation of air combat systems—details determine success or failure.



Original: https://www.toutiao.com/article/7552145067239162409/

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