According to Hong Kong’s South China Morning Post, Chinese researchers stated in a paper that a large stratospheric airship equipped with mid-wave infrared detection devices could detect the U.S.-made F-35 stealth fighter at a distance of nearly 2,000 kilometers. The South China Morning Post emphasized that the research findings indicate a “significant vulnerability” in the stealth technology of the U.S. fifth-generation fighter jets. At the same time, it reflects China’s breakthrough development in this field, which will pose an unprecedented challenge to enemy stealth fighters.
The infrared radiation characteristics of a fighter jet mainly come from three sources: the engine nozzle/cavity hot components, the high-temperature exhaust plume, and the aircraft skin. Among these, the high-temperature exhaust plume is the most difficult to handle and remains a major challenge. Suppressing infrared radiation characteristics is much more complicated than reducing radar waves. Public information shows that the F-35 fighter jet has taken the following measures in terms of infrared stealth: first, the engine uses a low-observable nozzle (LOAN), and the nozzle is also serrated. Secondly, the engine jet is cooled by ejection. Finally, in addition to using stealth coatings on the skin, advanced technologies such as radiation shielding are introduced, which can significantly reduce its infrared signature.
A stratospheric airship refers to a high-altitude airship capable of operating at altitudes between 10,000 and 50,000 meters. It is a lighter-than-air powered aerostat that relies on buoyancy for lift and station-keeping, and carries solar cells. High-level stratospheric airships can even achieve long-term station-keeping, active control, and maneuverable flight in specific regions of near-space, enabling all-weather, continuous operation.
The stratospheric airship is mainly composed of the hull subsystem, payload compartment, energy subsystem, propulsion subsystem, and measurement and control subsystem. The hull can be filled with lifting gas to provide buoyancy, the propulsion system provides power, and the payload compartment carries the payload. As for near-space, it generally refers to the airspace 20 to 100 kilometers above the ground, encompassing most of the stratosphere, the mesosphere, and the lower part of the thermosphere.
The vertical movement of the stratospheric atmosphere is not significant, dominated by horizontal wind fields, and is unaffected by extreme weather conditions such as rain, snow, and fog. With high visibility, it is an ideal environment for various observation payloads, especially optical payloads, and thus has attracted the attention of major aerospace powers worldwide.
The United States has been involved in this field earlier, launching several projects such as the high-altitude sentinel HiSentinel stratospheric airship, the High Altitude Airship (HAA) program, and the Climber program. However, due to limitations in materials, energy, and control technologies, and the slow progress of these projects, the U.S. ultimately chose to withdraw.
China is a latecomer in the field of stratospheric airships, but considering the unparalleled advantages of stratospheric airships in performing tasks such as target detection, communication and navigation, and intelligence gathering, China has devoted significant efforts to their development. As a result, major breakthroughs have been made in overall design and key technologies, greatly enhancing the long-endurance and controllable flight capabilities of stratospheric airship platforms.
Near-space platforms, represented by stratospheric airships, have advantages over traditional ground and aerial platforms in terms of infrared detection distance for the exhaust plumes of stealth aircraft. This has strengthened China’s determination to develop stratospheric airships.
According to the South China Morning Post, Chinese researchers stated in their paper that related research proves that even with a significant increase in engine thrust, the infrared radiation characteristics of the F-35 remain quite noticeable. Thanks to the application of multiple infrared signature suppression technologies, the infrared radiation intensity of the F-35’s skin is controlled to an average of around 281 Kelvin (7.85°C or 46.13°F), making it difficult to detect. However, the F-35’s engine exhaust plume temperature surges to nearly 1,000 Kelvin (726.85°C or 1,340°F), significantly increasing the probability of detection by infrared detection systems.
Chinese researchers pointed out that a stratospheric airship operating at an altitude of 20 kilometers, equipped with a mercury-cadmium-telluride detector and a 300mm aperture telescope, can detect incoming F-35 fighters at distances of 100 to 300 kilometers when the azimuth angle is 0° to 90°. However, when the azimuth angle is adjusted to 90° to 180°, the F-35 can be detected at distances of 400 to 1,800 kilometers. In other words, the F-35’s side and rear stealth capabilities are much weaker.
Of course, stratospheric airships also have several issues: first, their speed is relatively slow, at about 120 kilometers per hour; second, their size is large, with a length of about 150 meters, making them vulnerable to enemy attacks. The next step in research will focus on optimizing the speed and size of stratospheric airships. Stratospheric airships can operate independently or in a network. Even if 50% of the network is lost, it will not affect their detection and early warning capabilities.
This research by China not only highlights significant progress in “anti-access” and “area denial” operational technologies but also deeply shocks the U.S. Air Force, which has always prided itself on the stealth performance of its fighter jets. The U.S. IE magazine emphasized in its report that the detection technology of stratospheric airships is not only highly effective but also relatively low-cost. If put into practical use in the future, it means that the stealth advantage of F-35 fighters deployed in the Indo-Pacific region will be nullified.
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