J-20 5th Gen Fighter Thread IV (Closed to posting)

[Engineer]

And how would China get a F22 replica, plus the exact RAM formula? Each country's formula is different, unless you are implying that China somehow got hold of US RAM technology and successfully replicate (reverse engineered) and used it on their own aircraft.

So far, to my understanding, US had not release details on the F-22, its dimensions, tolerance, every single details, so if China is going to just based off a few photos they receive either from the net or otherwise, they are not going to be very accurate.

There is no need for China to produce a replica identical to the F-22 down to the molecular level. You and others who conjured up such a ridiculous requirement are committing a fallacy called

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[Engineer]

There is a good reason we vacuum away from the so call china's cyber espionage, it is a dirty hole and we do not want to dig. I mean, there is no real evidence of that happening. I believe countries are spying on each other though... (look to Snowden and you will know what I am talking about).

Firstly, you are limiting espionage to cyberspace when no such limitation was set when espionage was first brought up. Secondly, there is no evidence that China did not obtain useful data on the F-22 through espionage. Vacuuming away from espionage is simply a convenient way to ignore the reality that China has means to obtain information about the F-22.

Secondly... how do China know the properties of US RAM if they don't know what make up that RAM coating and how effective that coating was except for some publicly available information which can actually throw the calculation off by quite a bit.

Knowing the properties of RAM coating and knowing the composition of the RAM coating are different concepts. For example, a material engineer can take the chemical formula for a paint and calculates what color that paint will give. I can tell you what color the paint gives by simply looking at the surface without knowing the chemical composition; or if I want to be accurate, I can take a spectrometer and tell you exactly what kind of red it is, and I still do not need to know the chemical composition.

Also... if cyber espionage can produce that much information and China had been doing it for decades, shouldn't the J-20 and the J-31 already started mass production, since they would already by now get all the information they needed. Also... they could also be mass producing engines rather than having that much issues with WS-10A until recently.

Analyzing a design is different from realizing a design.

Again... how would China know for sure the effectiveness of the RAm coating used on latest US aircraft? By public information or as what Latenlazy seemed to bent on saying - cyber espionage? Again... a replica although look alike, will be totally wrong in terms of calculation and if China is basing on that data, it is not going to work. You need accuracy in this area...

See above.

 

[rhino123]

There is no need for China to produce a replica identical to the F-22 down to the molecular level. You and others who conjured up such a ridiculous requirement are committing a fallacy called

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Ahhh... stop coming in with your big words like whatever fallacy this and fallacy that. I am not as well verse in engineering as you are. I am merely asking a question if that is alright with you. From what limited knowledge I have, I believe that a big part of stealth is in its shape, angles and things like that. These are not easily available unless you have the blue print of the said aircraft. It might be wrong, and if that is the case, I am sorry.

Do you have to always come out with all these silly terms and accusing others of something that is totally not what we meant in the first place... geez!

 

[rhino123]

Firstly, you are limiting espionage to cyberspace when no such limitation was set when espionage was first brought up. Secondly, there is no evidence that China did not obtain useful data on the F-22 through espionage. Vacuuming away from espionage is simply a convenient way to ignore the reality that China has means to obtain information about the F-22.

First, look who I am replying to before you come in here and blast me. I am not the one who mentioned about cyber espionage and I am merely saying that we do not want to go there. And I believe that every nations are spying on each other whether you like it or not. US too are involved in this (eg. Snowden), and frankly I do not believe China is that innocent either.

Knowing the properties of RAM coating and knowing the composition of the RAM coating are different concepts. For example, a material engineer can take the chemical formula for a paint and calculates what color that paint will give. I can tell you what color the paint gives by simply looking at the surface without knowing the chemical composition; or if I want to be accurate, I can take a spectrometer and tell you exactly what kind of red it is, and I still do not need to know the chemical composition.

Ok. I make a mistake here and I am happy to admit to that mistake. So you don't need to know the exact composition of the RAM coating to know its actual effectiveness, you could just take and trust whatever information you can find on the net or from official announcement by the US. Got it.

(PS. You didn't say that but I think if you don't know what actually make up of the RAM coating of the US, then all the information you have are either from the net or press release or company release or with references to your own RAM coating).

Analyzing a design is different from realizing a design.

I understand that too. But how are you going to analyse a design without actually having touched one to get actual reading from that? But since you are the engineer, you know better than me. So I will take it as that.

See above.

See above.

 

[latenlazy]

Ahhh... stop coming in with your big words like whatever fallacy this and fallacy that. I am not as well verse in engineering as you are. I am merely asking a question if that is alright with you. From what limited knowledge I have, I believe that a big part of stealth is in its shape, angles and things like that. These are not easily available unless you have the blue print of the said aircraft. It might be wrong, and if that is the case, I am sorry.

Do you have to always come out with all these silly terms and accusing others of something that is totally not what we meant in the first place... geez!

Specific geometry is actually incredible easy (though very tedious!) to figure from just a few picture. That's how 3D artists and model makers do their thing. The more pictures you have and the higher the resolution, the more refined your model. If the internet isn't sufficient, you send a spy to an air show and take pictures.

First, look who I am replying to before you come in here and blast me. I am not the one who mentioned about cyber espionage and I am merely saying that we do not want to go there. And I believe that every nations are spying on each other whether you like it or not. US too are involved in this (eg. Snowden), and frankly I do not believe China is that innocent either.

I brought up espionage to point out that China may know more about the F-22 design than we think. Wasn't trying to assert any moral equivalency.

Ok. I make a mistake here and I am happy to admit to that mistake. So you don't need to know the exact composition of the RAM coating to know its actual effectiveness, you could just take and trust whatever information you can find on the net or from official announcement by the US. Got it.

Not just from the internet or official US announcements! They have chemists and material scientists for this sort of thing too.

(PS. You didn't say that but I think if you don't know what actually make up of the RAM coating of the US, then all the information you have are either from the net or press release or company release or with references to your own RAM coating).

Or you could steal the formula from a computer, and have your own scientists analyze it. Not a certainty of course, just a hypothesis.

I understand that too. But how are you going to analyse a design without actually having touched one to get actual reading from that? But since you are the engineer, you know better than me. So I will take it as that.

Well, for the sake of RCS simulations, you really only need to know geometry, material properties, and maybe internal structures. Educated guess work can fill in the gaps and get reasonably close to reality.

 

[Engineer]

From what limited knowledge I have, I believe that a big part of stealth is in its shape, angles and things like that. These are not easily available unless you have the blue print of the said aircraft. It might be wrong, and if that is the case, I am sorry.

Multiple pictures from multiple angles of the aircraft are taken. These are then processed on the computer to extract corners and edges. Minimization is then performed on these features using mathematical equations that govern the projection physics. This essentially projects the 2D features back into the 3-dimensional world. The more photos are used, the more precise the calculation will be. It works even better when the images are taken far away, such as when the aircraft is maneuvering in the sky, as this essentially simplifies the projection equations.

I understand that too. But how are you going to analyse a design without actually having touched one to get actual reading from that? But since you are the engineer, you know better than me. So I will take it as that.

Analysis are conducted by using prior design experience, as well as by applying mathematical models to known physics. This is done all the time. This is what engineering is about.

 

[Lion]

which then begs the question where is 2003, 2004 etc or do we have more than one bird with the same number?

2004 , 20003 and probably others are doing more intensive test in Inner Mongolia away from public eyes. There is no way we need 4 pt for stastic test.

 

[vincent]

Ok. I make a mistake here and I am happy to admit to that mistake. So you don't need to know the exact composition of the RAM coating to know its actual effectiveness, you could just take and trust whatever information you can find on the net or from official announcement by the US. Got it.

(PS. You didn't say that but I think if you don't know what actually make up of the RAM coating of the US, then all the information you have are either from the net or press release or company release or with references to your own RAM coating).

The US government must have done studies on the effectiveness of the RAM coatings (any competent manager would have requested that) before they decide on which one to choose. Those studies may not be guarded as zealously as the coatings' compositions. Lockheed Martin claimed their computer systems had been hacked, so the possibility of Chinese got their hands on those info exists

 

[latenlazy]

Multiple pictures from multiple angles of the aircraft are taken. These are then processed on the computer to extract corners and edges. Minimization is then performed on these features using mathematical equations that govern the projection physics. This essentially projects the 2D features back into the 3-dimensional world. The more photos are used, the more precise the calculation will be. It works even better when the images are taken far away, such as when the aircraft is maneuvering in the sky, as this essentially simplifies the projection equations.



Analysis are conducted by using prior design experience, as well as by applying mathematical models to known physics. This is done all the time. This is what engineering is about.

Btw Engineer, did you ever complete the translation of that long essay on the J-20 started by pugachev_diver? I was digging around to reread it, but it seems the copy I found in the older J-20 threads seemed to end at Part 1.

 

[Engineer]

Btw Engineer, did you ever complete the translation of that long essay on the J-20 started by pugachev_diver? I was digging around to reread it, but it seems the copy I found in the older J-20 threads seemed to end at Part 1.

It was never completed. By the way, the author wrote another essay a while ago which goes into more details about how vortexes positive reinforce one another to enhance lift.