J-20 5th Gen Fighter Thread VI

Discussion in 'Air Force' started by siegecrossbow, Sep 4, 2017.

  1. Air Force Brat
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    They are all beautiful aren't they, I'd have to pick the vapor cloud, but some of those here may recall the days when I longed to see a J-20 2 Ship formation, Zhuhai 2018 made me practically giddy, I LOVED all the J-20 flying, particularly day 5's solo-jockey to close the show, that roll-over break was beautiful, and showed the J-20 likes a few G's as well as the next gorgeous 5Gen!

    Like the F-35, people have put down the J-20's maneuverability due to no OVT, but Dr. Song's brilliant solution seem to have worked out amazingly well....

    What about you Dieno, I don't believe I saw your first hand account of the J-20 or J-10C performance's? or are you saving that for your new book??
     
  2. siegecrossbow
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    siegecrossbow Brigadier
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    I'm surprised you didn't mention the fact that Minnie Chang first quoted an outdated number (22 meters) for J-20's length and then claimed that it was two meters shorter than the J-15! The J-15 must be a 24 meter long behemoth based on her logic.
     
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  3. Errys
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    Errys Just Hatched
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    Chinese scientists hail ‘incredible’ stealth breakthrough that may blind military radar systems
    • Researchers at academy of science believe electromagnetic wave model is key that will herald new era in radar detection and avoidance for military ships and aircraft
    Stephen Chen
    Published: 1:00am, 19 Jul, 2019

    Chinese scientists have achieved a series of breakthroughs in stealth materials technology that they claim can make fighter jets and other weaponry lighter, cheaper to build and less vulnerable to radar detection.
    Professor Luo Xiangang and colleagues at the Institute of Optics and Electronics, Chinese Academy of Sciences in Chengdu, Sichuan province, said they had created the world’s first mathematical model to precisely describe the behaviour of electromagnetic waves when they strike a piece of metal engraved with microscopic patterns, according to a statement posted on the academy’s website on Monday.
    With their new model and breakthroughs in materials fabrication, they developed a membrane, known as a meta surface, which can absorb radar waves in the widest spectrum yet reported.
    At present, stealth aircraft mainly rely on special geometry – their body shape – to deflect radar signals, but those designs can affect aerodynamic performance. They also use radar absorbing paint, which has a high density but only works against a limited frequency spectrum.
    In one test, the new technology cut the strength of a reflected radar signal – measured in decibels – by between 10 and nearly 30dB in a frequency range from 0.3 to 40 gigahertz.
    A stealth technologist from Fudan University in Shanghai, who was not involved in the work, said a fighter jet or warship using the new technology could feasibly fool all military radar systems in operation today.
    “This detection range is incredible,” the researcher said. “I have never heard of anyone even coming close to this performance. At present, absorbing technology with an effective range of between 4 and 18 GHz is considered very, very good.”

    China’s new radar system could spot stealth aircraft from at long range

    The lower the signal frequency, the longer a radar’s detection range. But detailed information about a moving target can only be obtained with higher frequency radio waves. Militaries typically use a combination of radars working at different frequencies to establish lines of defence.
    The Medium Extended Air Defence System, Nato’s early warning radar, operates at a frequency range of 0.3 to 1 GHz. The American Terminal High Altitude Area Defence system, the missile defence radar that caught Beijing’s attention when it was deployed in South Korea in 2017, operates at frequencies around 10 GHz.
    Some airports use extremely short-range, high-frequency radars running at 20 GHz or above to monitor vehicle and plane movements on the ground, but even they might not be able to see a jet with the new stealth technology until it is overhead.
    “Materials with meta surface technology are already found on military hardware in China, although what they are and where they are used remains largely classified,” the Fudan researcher said.

    upload_2019-7-22_7-26-52.png
    Professor Luo Xiangang. Photo: Baidu

    Luo and his colleagues could not be reached for comment. But according to the academy’s statement and a paper the team published in the journal Advanced Science earlier this year, the stealth breakthroughs were based upon a discovery they made several years ago.
    They found that the propagation pattern of radio waves – how they travelled – in extremely narrow metallic spaces was similar to a catenary curve, a shape similar to that assumed by chains suspended by two fixed points under their own weight.

    China tests stealth ‘invisibility cloaks’ on regular fighter jets

    Inspired by catenary electromagnetics, the team developed a mathematical model and designed meta surfaces suitable for nearly all kinds of wave manipulation.
    These included energy-absorbing materials for stealth vehicles and antennas that can be used on satellites or military aircraft.
    Zhu Shining, a professor of physics specialising in meta materials at Nanjing University, said the catenary model was a “novel idea”.
    “The Institute of Optics and Electronics in Chengdu has conducted long-term research in this area which paved a solid foundation for their discoveries. They have done a good job,” Zhu said.
    “Scientists are exploring new features of metal materials, some of them are already in real-life applications.”
     
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  4. Air Force Brat
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    Old news Bub, the J-20 already incorporates meta-materials on leading and trailing edges of canards, intakes, main wing, nose cone, vertical stabs, leading and trailing edges... its the grey looking material. The US has been using the same technology on the F-22 and F-35, likely all L/O aircraft use similar technology..
     
  5. Equation
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    Equation Lieutenant General

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    I think you're under the misconception that the invention here is "meta-materials" in general, so you thought this is already deployed on active jets. But in reality, not all meta-materials are the same and you can certainly make superior or next generation meta-materials compared to the ones in use and this seems to be what the article is saying if you read it carefully.
     
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  6. Air Force Brat
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    The article is about meta materials, they did explain the patterning in more detail, boxing and chain curving, and no doubt meta-material patterns and material are being constantly refined... never the less, the author seems not to realize that meta-material has already been employed on numerous 5th Gen/Chinese 4th gen fighter aircraft?

    The Chinese military would have suppressed this information if it were indeed "bleeding edge" top secret..... there wouldn't be a "pressor".....
     
  7. Xsizor
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    Xsizor Junior Member
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    The F-22 uses metamaterials ? Mass producing them isn't easy and better technologies that enables mass production are under research in the US and elsewhere.
    Have to admit that this "metamaterial- stealth" had a PR boost with the J-20(and only J-20 conspicuously) I have yet to come across articles that throws light on the application of metamaterials in stealth fighters of US origin.
    Although i would be inclined to drag in F-35 into that, to be on the safe side, i am assuming that F-35 is indeed utilizing meta-materials for stealth. That jet certainly had the money flowing to support it, along with recent technological advancements.
     
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  8. zaphd
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    zaphd New Member
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    Aviation Week's special report "State of Stealth" from a few years back describes the most common RAM materials according to public knowledge. These include composites of dielectric materials with lossy filler, dielectric absorbers, magnetic ferrites and geometric absorbers (sawtooth structures). These materials are then combined to get a wide absorption frequency band. However, these traditional RAMs are bulk materials, not metamaterials. Metamaterials have built-in sub-wavelength structures like holes, waveguides or resonators, which can be used to tune their electrical properties to minimize reflection. Aviation Week's report identified metamaterials as a hot research topic in stealth, but didn't even conjencture they were used today on US aircraft.

    So from what I've read in publically available sources, China is truly innovating with its stealth metamaterials.
     
  9. Equation
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    Equation Lieutenant General

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    Why would you think that the author is unaware of the current use of meta-materials in aircraft? Show me what sentences give you that impression. There is a sentence in there that says that meta-materials are already used in the Chinese military and I can't think of one where they'd be more advantageous than in aircraft.

    This is clearly a piece of news; they are talking about new models that came out "Monday" and you're here trying to do whatever you can to make it sound like China didn't make progress; it has to be old! It's amazing that your mind can automatically wrap around news like that to protect itself from coming to obvious conclusions that it doesn't want to see.

    Well, if it were about to be used to military project, the information should be suppressed, but this looks like they've just come out with early concept and test models in the realm of basic research. Such things are not necessarily suppressed. Make no mistake, this is not something that will be applied to all of China's projects in a year or 2; this is probably the very beginning of something that might eventually be used in next gen designs. Articles like this have not reach the stage where the military needs to suppress them yet.
     
  10. taxiya
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    taxiya Major
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    Are you equating the "selective RF absorbent composite" used on F-35 and F-22 with "meta material"? There has been a lengthy and even heated debate of their difference in this forum.

    I remember Tirdent was the one sharing the same definition with you with whom I and many others had the lengthy debate. In a strict definition (not mine but published research reports), the composites are not meta-materials although to some extent they do a similar job.

    Without arguing the definition, I would agree that F-22, F-35 and J-20 all have used selective RF treatment materials, but only J-20 is rumoured to have used meta-material.
     
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