J-20 5th Gen Fighter Thread VI

[Totoro]

heavier than the F-22 and lighter than the SU-27.

This makes no sense. Probably an error.

 

[jobjed]

This makes no sense. Probably an error.

Did you literally stop reading seige's post immediately after "lighter than the Su-27"?

 

[Hyperwarp]

He said that he first heard about J-20's weight in 2006 and that it was supposed to be heavier than the F-22 and lighter than the SU-27. Ten years have passed and the current situation is unclear. He also later discovered that there were discrepancies regarding F-22's statistics by the Chinese intelligence and that there are problems with F-22's weight data.

Probabaly the other way around: Empty weight wise,

F-22: 19,700 kg
Su-27: 16,380 kg

 

[latenlazy]

Probabaly the other way around: Empty weight wise,

F-22: 19,700 kg
Su-27: 16,380 kg

Nope. From the sounds of his comment he’s saying in 2006 Chinese intel believed the F-22 was actually lighter than the Su-27. It’s possible they never updated their information on the F-22 after initial weight parameters were set for the program (if I recall correctly when F-22 development first started the weight target was much lower than the 19 tonnes we have today), and assumed later news about weight gain and higher weight specs in public media were head fakes until they got updates on internally used figure which they had a high confidence of fidelity for.

 

[Hyperwarp]

Nope. From the sounds of his comment he’s saying in 2006 Chinese intel believed the F-22 was actually lighter than the Su-27. It’s possible they never updated their information on the F-22 after initial weight parameters were set for the program (if I recall correctly when F-22 development first started the weight target was much lower than the 19 tonnes we have today), and assumed later news about weight gain and higher weight specs in public media were head fakes until they got updates on internally used figure which they had a high confidence of fidelity for.

So if I am getting this right... what was said is that the J-20 is meant to be lighter than an Su-27 (<16,380 kg)? To compare, the smaller F-35A/B/C are at 13,300/14,700/15,800 kg respectively. Su-57 is esimated to be between 18,000 and 18,500 kg.

So, according to what is being said the J-20 is less than 16,380 kg?

How the hell did they shave-off so much weight in a twin-engined 20m fighter?

 

[taxiya]

If 3D metamaterials were used, the layer thickness would need to be in the order of RF wavelength. I doubt it would be applied to large area due to weight penalty, it would be strategically applied on areas such as LERX, canards edges and gap, wing edge ...etc. Incidentally those area's are painted grey as well...

Not for metamaterial. The thickness thing is related to the traditional RAM. The purpose of metamaterial is to overcome that relationship. The way of metamaterial working is the micropatterns that are made by thin wires will keep the incoming waves adherent to the surface and being conducted away instead of bouncing back to the incoming direction. The design of patterns determine the band width of absorbance. Metamaterial is broadband radio absorbance relative to paint based RAM.

 

[latenlazy]

So if I am getting this right... what was said is that the J-20 is meant to be lighter than an Su-27 (<16,380 kg)? To compare, the smaller F-35A/B/C are at 13,300/14,700/15,800 kg respectively. Su-57 is esimated to be between 18,000 and 18,500 kg.

So, according to what is being said the J-20 is less than 16,380 kg?

How the hell did they shave-off so much weight in a twin-engined 20m fighter?

When they initially set the parameters for the J-20 in 2006, yes. That doesn’t necessarily mean they actually achieved those targets though. At the outset of development the F-22 was supposed to be a lot lighter too. A combination of changing requirements and difficulties with manufacturing tolerances led to a relaxation of the F-22’s intended weight.

 

[taxiya]

So what you are saying is that you don't actually have any evidence that anti-UHF metamaterials are currently being used by the J-20.

It was said by more than one source that J-20 use metamaterials. But there is no saying of exactly what frequency and where on the plane these metamaterials are used. So no, there is no evidence for UHF you can get right now. And PLA will never tell, pretty much like USAF never tell similar things about F-22 and F-35.

But if you know the principle how metamaterial works, you would not ask for the proof on UHF. You just need the proof of existence of metamaterial in mass production which has been reported few months ago (beginning of 2018 by CCTV).

The principle of RA property of metamaterial is designing a micro pattern of conducting wires (like micro antenna array). The desired bandwidth are determined by the pattern. Other than patterns there is no difference in physical dimension, and there is no more challenge between printing different patterns. It can be designed to be anti many frequency bands. Actually metamaterial is effective in a relatively broader band than traditional RAM, it is called broadband RA.

 

[taxiya]

Um, no. You could use the exact same argument to "prove" any kind of unfounded conjecture. String a couple of unrelated articles together with some random internet crap speculation, demand that evidence directly linking them is not required, make some categorically unproven statements, and voila you somehow now have access to an alleged solid J-20-prereveal type of "fact", which in reality is still just nothing but speculation hanging on the most tenuous of logical threads. And yet you have made a definitively unambiguous claim to fact, as if you were simply relating that the sun rises each day and you were merely passing this knowledge on to the rest of us.

It would be far better for you to directly link the articles you mentioned instead of obscuring them inside 268 pages of J-20 thread, and point out exactly in these articles where the J-20 is speculated to be currently using UHF-specific metamaterials. Current metamaterials "research" is insufficient, speculation on current metamaterials use is insufficient. What is needed is evidence that research on UHF-specific metamaterials has already been finished, along with some kind of evidence that J-20 is currently using UHF-specific metamaterials; these don't have to be present in the same article but they should both be present in some form for your claim to have any iota of legitimacy at all. Your mere personal opinion that this is the case is wholly insufficient.

I suggest you google for a few days. I am sure you will find more concrete evidence that you are demanding. I have done that and have found research papers by not only Chinese, but also US and Dutch scientists. US was the early starters (if that makes you feel more believing?) The only thing that China was specially successful is "mass production". There are videos showing the sheet in meters dimension. The videos have been posted in this forum. Other countries (US included) can make the material too, but only in smaller size that is not feasible to be put on operational aircraft.

By your logic, the RCS of F-22 being a pingpong ball is unfounded conjecture because USAF did not release measurement data to the world, but only saying so?

 

[Iron Man]

It was said by more than one source that J-20 use metamaterials. But there is no saying of exactly what frequency and where on the plane these metamaterials are used. So no, there is no evidence for UHF you can get right now. And PLA will never tell, pretty much like USAF never tell similar things about F-22 and F-35.

But if you know the principle how metamaterial works, you would not ask for the proof on UHF. You just need the proof of existence of metamaterial in mass production which has been reported few months ago (beginning of 2018 by CCTV).

The principle of RA property of metamaterial is designing a micro pattern of conducting wires (like micro antenna array). The desired bandwidth are determined by the pattern. Other than patterns there is no difference in physical dimension, and there is no more challenge between printing different patterns. It can be designed to be anti many frequency bands. Actually metamaterial is effective in a relatively broader band than traditional RAM, it is called broadband RA.

So you admit to no evidence for UHF-specific metamaterials use on the J-20. Current use of metamaterials in general on the J-20 is not a topic that interests me nor was it the reason I was prompted to respond to plawolf. If you look back a few pages plawolf had been claiming that the J-20 was nigh invisible to AWACS. I had responded by saying that stealth fighters in general are not designed for UHF-band RCS reduction, and subsequently the stealth features of the J-20 are significantly attenuated against AWACS which uses the UHF band. He subsequently slipped in a comment a few pages later that the J-20 is currently using UHF-specific metamaterials, clearly an indirect response to my post. And here we are now at this juncture, with still neither of you having any tangible evidence that the J-20 is using UHF-specific metamaterials despite all the innuendo and pages of back and forth.

I suggest you google for a few days. I am sure you will find more concrete evidence that you are demanding. I have done that and have found research papers by not only Chinese, but also US and Dutch scientists. US was the early starters (if that makes you feel more believing?) The only thing that China was specially successful is "mass production". There are videos showing the sheet in meters dimension. The videos have been posted in this forum. Other countries (US included) can make the material too, but only in smaller size that is not feasible to be put on operational aircraft.

By your logic, the RCS of F-22 being a pingpong ball is unfounded conjecture because USAF did not release measurement data to the world, but only saying so?

You honestly think I have not done my due diligence prior to posting in this thread? I have no doubt that you have also done your due diligence, but the real question is whether you really understand what you're reading and how you think any of it applies to the J-20's current use of UHF-specific metamaterials. Research papers are INSUFFICIENT in and of themselves. The ones I have seen read like feasibility studies, as in significant reductions in the thickness of UHF-specific metamaterials are possible, or even have been successfully demonstrated in the lab, and could in the future be used in real world applications. Lab work is the foundation for real world applications, but these two are not even remotely the same things. In the case of China publications on real world applications will of course not be forthcoming, in which case we would have to look at each paper and what conclusions/statements they are making about their specific contributions to eventual operational fielding of UHF-specific metamaterials, as well as the date of publication. Remember that UHF-specific metamaterials have an extra step that X-band metamaterials do NOT have, namely the requirement for size/thickness reduction. Just demonstrating that "metamaterials" research is complete or even that such materials are currently in use on the J-20 is insufficient evidence of UHF-specific metamaterials in use on the J-20. If you think any of the articles you have read constitutes "concrete evidence" of the J-20 currently using UHF-specific metamaterials, please link them here and we can discuss the merits of the papers you have linked.

And BTW, the RCS of the F-22 is quoted as being that of a metal "ball bearing" or "steel marble", not a pingpong ball, and yes, it IS conjecture and always will be.