Chengdu J-20 pictures, analysis and speculation Part II

[quellish]

How many watts do you think it'd take to BBQ the pilot? How many years do they plan on having the T-50 in service?

The viability of such a thing is highly dependent on the system's ability to send a lot of energy in a focused beam through a turbulent atmosphere from a moving platform to a moving target. Adaptive optics are not enough to accomplish this (though they help with thermal blooming, which is a different problem), and very short wavelengths are required to drill a hole through the turbulent, dirty atmosphere to the target. The shorter the wavelength, the more power is needed. For the application described high power and non trivial dwell times are required as well as short wavelengths. Over even short air to air engagement or counter-AAM distances the power requirements alone are non trivial, and not available in the foreseeable future.

However, that is off topic.

Apparently not, given how much surprise J-20 took the pentagon by.

Why do you say that the J-20 took the Pentagon by surprise?

At the very least, I'm sure we can agree that china is seeking to hide its true capability rather than exaggerate it.

There are several physical features of their recent efforts that appear almost - cosmetic - rather than functional. There are also elements that appear to be "monkey see, monkey do" or more accurately "cargo cult stealth". At the same time, there are other things that clearly show a reasonable understanding of the underlying principals and at least some ability to apply it.

So I would for now strongly disagree with that statement, though I am certainly not calling the design teams responsible fools. And yes, I intentionally used the plural.

 

[Blitzo]

Why do you say that the J-20 took the Pentagon by surprise?

Maybe that statement is a bit too strong, perhaps "how much it seemed to take the pentagon by surprise," or rather, "how much it seemed to take the US and western military community by surprise".

I'm sure there were people in the pentagon who knew when J-20 was going to be ready to fly. Whether the non specialists were expecting something like J-20 is another matter,IMHO.

There are several physical features of their recent efforts that appear almost - cosmetic - rather than functional. There are also elements that appear to be "monkey see, monkey do" or more accurately "cargo cult stealth". At the same time, there are other things that clearly show a reasonable understanding of the underlying principals and at least some ability to apply it.

So I would for now strongly disagree with that statement, though I am certainly not calling the design teams responsible fools. And yes, I intentionally used the plural.

Are you talking about j-20 and project 310? Because I was talking about how little the PLA seeks to show off its development or capability overall (everything from Y-20 to nuclear subs to destroyers to ICBMs and even something as simple as aircraft fleet inventories), so I'm not sure how specifically looking at recent chinese efforts at stealth is directly relevant.

That is to say, my statement wasn't reflective of chinese technological competency at stealth or what not, but rather stating that the PLA has a "PR" tendency to keep a lid on all important military projects. I hope that clears up the confusion, and I'd ask if you still strongly disagree with the statement of mine which you quoted.

---

As for "cargo cut stealth," what examples of these do you see, and in what ways could similar RCS reduction be achieved but using "non" cargo cut stealth? Or are you saying they added together various RCS reduction measures without a good idea of how it may turn out (I'm sure you can be sympathetic to how ambitious a claim that is). Or are any seemingly contradictory design choices possibly simply reflective of relative inexperience in RCS reduction and/or perhaps a necessity bound by the aircraft's aerodynamic configuration?

And what features appear cosmetic rather than functional, to you? After all, I think it isn't inaccurate to say that RCS reduction shaping is probably something that can be more accurately judged via an aircraft's cosmetics (more so, than say an aircraft's aerodynamics). So if there is a "cosmetic" feature that looks like its meant to reduce RCS then chances are that's probably why it is there.
(Of course, I'm interested to hearing you elaborate on this.)
(If you have the time, I'd also be interested in hearing your opinion on how J-20 compares with T-50 (and F-35, and F-22) in regards to any examples cargo cut stealth and cosmetic features present on each aircraft. Form should follow function after all, and anything on J-20 that looks cosmetic or cargo cut should logically be seen as half baked on another aircraft as well)

 

[latenlazy]

There are several physical features of their recent efforts that appear almost - cosmetic - rather than functional. There are also elements that appear to be "monkey see, monkey do" or more accurately "cargo cult stealth". At the same time, there are other things that clearly show a reasonable understanding of the underlying principals and at least some ability to apply it.

So I would for now strongly disagree with that statement, though I am certainly not calling the design teams responsible fools. And yes, I intentionally used the plural.

As for "cargo cut stealth," what examples of these do you see, and in what ways could similar RCS reduction be achieved but using "non" cargo cut stealth? Or are you saying they added together various RCS reduction measures without a good idea of how it may turn out (I'm sure you can be sympathetic to how ambitious a claim that is). Or are any seemingly contradictory design choices possibly simply reflective of relative inexperience in RCS reduction and/or perhaps a necessity bound by the aircraft's aerodynamic configuration?

And what features appear cosmetic rather than functional, to you? After all, I think it isn't inaccurate to say that RCS reduction shaping is probably something that can be more accurately judged via an aircraft's cosmetics (more so, than say an aircraft's aerodynamics). So if there is a "cosmetic" feature that looks like its meant to reduce RCS then chances are that's probably why it is there.
(Of course, I'm interested to hearing you elaborate on this.)

Ultimately what's REALLy missing in this discussion is specifics. It seems pretty evident (and I welcome correction on this assertion) that most of the people in this discussion don't have any particular and specific expertise on electrical engineering, and even more so on RCS management and reduction. It would be REALLY helpful to the quality of the discussion if people with such backgrounds could give specific insights to what's going on with the J-20's design, because otherwise it's just two sides pushing uninformed arguments that are based on weak (usually even irrelevant) evidence and impressions, and the subsequent discussion really doesn't go anywhere. For example, having an exact idea of what they're getting right and wrong with the J-20s design may tell us a lot about when the design itself may be ready, and how much difficulty they're having with the engineering behind the design. That sure as heck would beat the generic filler arguments we've currently been having in this thread.

 

[Blitzo]

Ultimately what's REALLy missing in this discussion is specifics. It seems pretty evident (and I welcome correction on this assertion) that most of the people in this discussion don't have any particular and specific expertise on electrical engineering, and even more so on RCS management and reduction. It would be REALLY helpful to the quality of the discussion if people with such backgrounds could give specific insights to what's going on with the J-20's design, because otherwise it's just two sides pushing uninformed arguments that are based on weak (usually even irrelevant) evidence and impressions, and the subsequent discussion really doesn't go anywhere. For example, having an exact idea of what they're getting right and wrong with the J-20s design may tell us a lot about when the design itself may be ready, and how much difficulty they're having with the engineering behind the design. That sure as heck would beat the generic filler arguments we've currently been having in this thread.

I have no background in electrical engineering or RCS management and reduction -- only logic.


Of course, if any other members such as quellish does have a background in these industries and can provide some more technically rich information to support their positions and explain any questions that may be put forward, then I obviously welcome it.




But if the best we can do is to say "this looks superficial" or "it seems like they don't know what they're doing" without substantial backup, then the responses and challenges will be naturally underwhelming as well. But I want to venture to say that even without specific technical or insider knowledge, we can still seek a "null hypothesis" as it is, using logic.


For instance, I consider RCS reduction shaping to be a domain which stands relatively susceptible to eyeballing, and where form does indeed tend to follow function more than say, aerodynamics. for instnace, it might be claimed that feature X on aircraft A is claimed to be useless for stealth, but if aircraft B (which is accepted to be known for its RCS reduction measures) also has feature X, then aircraft A's feature X should logically not be so uesless after all.


So say, this might apply to serrations, to edge alignment, to chines, to weapon bays, to clean cockpits, faceted EOTS housings.




Of course, no one can say how well all those features on aircraft A may ultimately interact to produce a final RCS return, so in terms of RCS, I think looking at the individual features are as good as we can get (although its final estimate will probably be more accurate than an estimate of a plane's aerodynamics, as previously mentioned). I'd say even someone with technical knowledge in the field wouldn't be able to tell us much about a plane like J-20, unless they have access to a RCS testing facility and an accurately scaled series of aircraft models including J-20.

 

[Deino]

Upppss... what a really strange discussion and like 'latenlazy' noted, this became very much a competition of opinions or a "fishing in a muddy pond" ...


By the way maybe we all missed (even if already known from '2002' the IFR-probe doors are visible.

Deino

 

[Hanse]

The viability of such a thing is highly dependent on the system's ability to send a lot of energy in a focused beam through a turbulent atmosphere from a moving platform to a moving target. Adaptive optics are not enough to accomplish this (though they help with thermal blooming, which is a different problem), and very short wavelengths are required to drill a hole through the turbulent, dirty atmosphere to the target. The shorter the wavelength, the more power is needed. For the application described high power and non trivial dwell times are required as well as short wavelengths. Over even short air to air engagement or counter-AAM distances the power requirements alone are non trivial, and not available in the foreseeable future.

I trust you've heard of DIRCMs? One doesn't need to turn the pilot into a charcoal briquette to take him out of the game long enough to deal with his plane.

Why do you say that the J-20 took the Pentagon by surprise?

I seem to recall a certain SecDef telling us we could cancel the F-22 because it would take 20 years for China to come up with a stealth fighter. Whoops. (On the other hand, at times I've wondered if they did know about it and thought to themselves, "we better start working on the next generation NOW".)

 

[bobbymike]

http://i50.photobucket.com/albums/f307/Bengt123/Tacit_Blue.jpg

Ultimately what's REALLy missing in this discussion is specifics. It seems pretty evident (and I welcome correction on this assertion) that most of the people in this discussion don't have any particular and specific expertise on electrical engineering, and even more so on RCS management and reduction. It would be REALLY helpful to the quality of the discussion if people with such backgrounds could give specific insights to what's going on with the J-20's design, because otherwise it's just two sides pushing uninformed arguments that are based on weak (usually even irrelevant) evidence and impressions, and the subsequent discussion really doesn't go anywhere. For example, having an exact idea of what they're getting right and wrong with the J-20s design may tell us a lot about when the design itself may be ready, and how much difficulty they're having with the engineering behind the design. That sure as heck would beat the generic filler arguments we've currently been having in this thread.

I have no background in electrical engineering or RCS management and reduction -- only logic.


Of course, if any other members such as quellish does have a background in these industries and can provide some more technically rich information to support their positions and explain any questions that may be put forward, then I obviously welcome it.




But if the best we can do is to say "this looks superficial" or "it seems like they don't know what they're doing" without substantial backup, then the responses and challenges will be naturally underwhelming as well. But I want to venture to say that even without specific technical or insider knowledge, we can still seek a "null hypothesis" as it is, using logic.


For instance, I consider RCS reduction shaping to be a domain which stands relatively susceptible to eyeballing, and where form does indeed tend to follow function more than say, aerodynamics. for instnace, it might be claimed that feature X on aircraft A is claimed to be useless for stealth, but if aircraft B (which is accepted to be known for its RCS reduction measures) also has feature X, then aircraft A's feature X should logically not be so uesless after all.


So say, this might apply to serrations, to edge alignment, to chines, to weapon bays, to clean cockpits, faceted EOTS housings.




Of course, no one can say how well all those features on aircraft A may ultimately interact to produce a final RCS return, so in terms of RCS, I think looking at the individual features are as good as we can get (although its final estimate will probably be more accurate than an estimate of a plane's aerodynamics, as previously mentioned). I'd say even someone with technical knowledge in the field wouldn't be able to tell us much about a plane like J-20, unless they have access to a RCS testing facility and an accurately scaled series of aircraft models including J-20.

Take a look at that picture any 'logic' in it for you?

 

[Blitzo]

http://i50.photobucket.com/albums/f307/Bengt123/Tacit_Blue.jpg

Take a look at that picture any 'logic' in it for you?

Yes, and it is rather telling that few other modern stealth aircraft show great similarities with features unique to tacit blue. Although there are a few elements of tacit blue that are in common with other VLO and LO planes, such as chines, and canted tails, recessed intake and engine.

Besides, using tacit blue as an example is cheeky, considering it is very much an exception among the stealth demonstrators, and I wonder if its task as a sensor platform determined its rather unique shape as well, not to mention it first flew in 1982, when stealth design was still in its early days, and no stealth aircraft since has fielded quite a geometry like it (although some stealthy cruise missiles could be argued to have a similar configuration).

 

[bobbymike]

http://i50.photobucket.com/albums/f307/Bengt123/Tacit_Blue.jpg

Take a look at that picture any 'logic' in it for you?

Yes, and it is rather telling that few other modern stealth aircraft show great similarities with features unique to tacit blue. Although there are a few elements of tacit blue that are in common with other VLO and LO planes, such as chines, and canted tails, recessed intake and engine.

Besides, using tacit blue as an example is cheeky, considering it is very much an exception among the stealth demonstrators, and I wonder if its task as a sensor platform determined its rather unique shape as well, not to mention it first flew in 1982, when stealth design was still in its early days, and no stealth aircraft since has fielded quite a geometry like it (although some stealthy cruise missiles could be argued to have a similar configuration).

Of course I was referencing it in relation to seeing it in 1982 and having a layman talk about the 'logic' of it. Would have been very interesting.

 

[_Del_]

http://i50.photobucket.com/albums/f307/Bengt123/Tacit_Blue.jpg

no stealth aircraft since has fielded quite a geometry like it (although some stealthy cruise missiles could be argued to have a similar configuration).

Or perhaps, at least not the ones we know of...

 

[Blitzo]

Of course I was referencing it in relation to seeing it in 1982 and having a layman talk about the 'logic' of it. Would have been very interesting.

I think back then the logic of it would have been sound, given it was still the formative years of stealth.

 

[bobbymike]

Of course I was referencing it in relation to seeing it in 1982 and having a layman talk about the 'logic' of it. Would have been very interesting.

I think back then the logic of it would have been sound, given it was still the formative years of stealth.

Really? You think an aircraft enthusiast let's say born in 1950 seeing the developments in civil and military aviation would have 'glimpsed' Tacit Blue in 1982 and said 'The design is so logical'?

 

[Blitzo]

Really? You think an aircraft enthusiast let's say born in 1950 seeing the developments in civil and military aviation would have 'glimpsed' Tacit Blue in 1982 and said 'The design is so logical'?

That would depend on how well informed he or she was before glimpsing it.


However I think you're misinterpreting the context in which I used the word "logic." I used an example of saying "if feature X on aircraft A is claimed to be useless for stealth, but if feature X is also present on aircraft B which is known to have good RCS management, then it is likely feature X on aircraft A is also meant to produce similar RCS management."


I never said anything about judging a plane or even a plane's feature individually and saying whether the design was logical, only that if two aircraft both feature a specific design feature and one of the planes is known to have that feature for a particular use, then the other plane likely has that design feature for a similar use.
Of course, this was in response to quellish saying some design features on j-20 were "cosmetic" rather than functional.

 

[overscan (PaulMM)]

Judging from US experience with F-22 and F-35, the two piece canopy was lighter and also allowed a faster ejection (no waiting for the canopy to be jettisoned, just punch through). These were considered detirmining factors for F-35 especially given the VTOL version.

 

[bobbymike]

Really? You think an aircraft enthusiast let's say born in 1950 seeing the developments in civil and military aviation would have 'glimpsed' Tacit Blue in 1982 and said 'The design is so logical'?

That would depend on how well informed he or she was before glimpsing it.


However I think you're misinterpreting the context in which I used the word "logic." I used an example of saying "if feature X on aircraft A is claimed to be useless for stealth, but if feature X is also present on aircraft B which is known to have good RCS management, then it is likely feature X on aircraft A is also meant to produce similar RCS management."


I never said anything about judging a plane or even a plane's feature individually and saying whether the design was logical, only that if two aircraft both feature a specific design feature and one of the planes is known to have that feature for a particular use, then the other plane likely has that design feature for a similar use.
Of course, this was in response to quellish saying some design features on j-20 were "cosmetic" rather than functional.

Thank you for the thoughtful responses much clearer to me what you meant. As Heinlein said 'Any technology advanced enough is indistinguishable from magic'

I may be admitting my own limitations in terms of knowledge but logic only gets me so far

 

[kcran567]

I wonder if the Chinese are trying to figure out a way to get a directed energy weapon onto the J-20 eventually to counter the f-35. The J-20 could be a really good platform for one as well due to its speed and range advantage over the F-35... Or would the Chinese develop that for their own 6th gen design. It would make sense to put one on the J-20 first as a deterrent to the F-35.

 

[Reaper]

Why give up on a famous and recognised brand image?

 

[shivering]

" As Heinlein said 'Any technology advanced enough is indistinguishable from magic' "

Actually, that statement is attributed to Arthur C. Clarke.

http://en.wikipedia.org/wiki/Clarke%27s_three_laws

 

[bobbymike]

" As Heinlein said 'Any technology advanced enough is indistinguishable from magic' "

Actually, that statement is attributed to Arthur C. Clarke.

http://en.wikipedia.org/wiki/Clarke%27s_three_laws

Thanks appreciate the correction

 

[Deino]

 

[Radical]

If the J-20 really is around 20.5 meters long, then the Chinese people seem to be unusually short.

 

[latenlazy]

If the J-20 really is around 20.5 meters long, then the Chinese people seem to be unusually short.

Average height of men in China is 5'7" in the city and 5'5" in the country side as of 2002, and 5'8" as of 2010. Average height is shorter for older demographics due to poor nutrition in those age cohorts, especially in China's interior provinces.

That said, I think in this case it could be a matter of the lenses being used and perspective.

 

[overscan (PaulMM)]

You also can't actually see their feet in that pic, unless the whole crew are amputees.

 

[Radical]

If the J-20 really is around 20.5 meters long, then the Chinese people seem to be unusually short.

Average height of men in China is 5'7" in the city and 5'5" in the country side as of 2002, and 5'8" as of 2010. Average height is shorter for older demographics due to poor nutrition in those age cohorts, especially in China's interior provinces.

That said, I think height in this case it could be a matter of the lenses being used and perspective.

Perhaps. When I was in China in 2006, they did seem to be about 2 inches or so shorter than Americans on average. It could also be that the J-20 has higher landing gears. I think satellite images and comparisons with other known vehicles pin the old J-20 to be roughly 20.5 meters or so.

 

[overscan (PaulMM)]

In Beijing, I was about average height (I'm 1.75m).


In some part of the south I was notably taller than most. My wife (1.78m) was taller than pretty much everyone.


Regardless, I would be careful working from this image into any great conclusions. Note the tyre of the vehicle is cut off like the feet of the people.

 

[latenlazy]

In Beijing, I was about average height (I'm 1.75m).


In some part of the south I was notably taller than most. My wife (1.78m) was taller than pretty much everyone.


Regardless, I would be careful working from this image into any great conclusions. Note the tyre of the vehicle is cut off like the feet of the people.

I brought up the statistics because the height thing has been brought up before. At 5'11" in Beijing I'm slightly above average, but in Shanghai I'm noticeably taller. It's also very common for most kids to be taller than their parents in China. The cohort born between the 1950s-70s did not have it good back in the day.

 

[J.A.W.]

Too true, I recently saw some of my old school photos for the 1st time - in decades..

.. & the 'fat' kid we used to call 'porky' aint at all.. really - by current standards the rest of us look hungry..

 

[Deino]

 

[overscan (PaulMM)]

Interesting...

 

[Deino]

Interesting...

This One too ... But in its original size with 2.5 MB too big, anyway I hope You like it.

Deino

 

[overscan (PaulMM)]

Original res.

 

[Deino]

Another Nice Shot ...

 

[Sundog]

Based on Pauls pic just above, is that a small exhaust vent on the chine right at the trailing edge of the canard? Maybe a bleed air vent for the inlet?

 

[SOC]

You mean the hexagon-shaped thing? That's believed to be a bleed air vent, yes.

 

[Deino]

... Not sure if These latest Images were From the Maiden-flight ... iMO it Looks like a demonstration for CAC members.

 

[Sundog]

You mean the hexagon-shaped thing? That's believed to be a bleed air vent, yes.

No, I mean on the top of the chine, right where the trailing edge of the canard root fairing intersects the chine. If you look at the big picture it looks like some sort of vent there.

 

[latenlazy]

You mean the hexagon-shaped thing? That's believed to be a bleed air vent, yes.

No, I mean on the top of the chine, right where the trailing edge of the canard root fairing intersects the chine. If you look at the big picture it looks like some sort of vent there.

That was there in 2001/2 as well. My guess is that it's a vent for the APU, gas vent for the gun, or cooling vent for electronics.

 

[Trident]

Yes, that would be my guess as well. Looking at the size of the F-22's dorsal bleed vents that opening on the J-20 doesn't seem to be big enough to handle a meaningful bleed flow.
Something else that struck me with that photo though is that the flaperon hinges appear to have a Rafale-style serrated RAM strip.

 

[Deino]

Intresting view ...

 

[Grey Havoc]

Intresting view ...

"Not the blades again!"

;D