J-20 5th Gen Fighter Thread V

[FORBIN]

Experience isn't a durable or insurmountable gap.

My point is no for the future yet with China for have infos to present it is difficult !!! so useless going for riddles.
Time is necessary for it no in severals years i am in the reality

 

[Inst]

@latenlazy: The J-31, if it's designed with attention to its RCS, is potentially stealthier than the J-20, not only because of its cleaner design, but also because it is a somewhat smaller aircraft.

As to the J-31 being preferred over the J-20's configuration, the J-31 is not considered supermaneuverable with neither canards nor TVC. It is designed for TVC, but we have yet to see a TVC Chinese aircraft.

Regarding epistemology, what you're basically saying is that mathematics is impossible because you can't compile axioms into theorems. Between the Kopp simulation, the Taiwanese simulation, and the Chinese simulation of the F-22, it's reasonable to assume that the J-20, without RAM, is 5-10 dBsm less stealthy than comparable US fighters.

 

[latenlazy]

My point is no for the future yet with China for have infos to persent it is difficult !!! so useless goind for assertions.
Time is necessary for it no in severals years i am in the reality

You assume their first stealth fighter is also when they first began to build their capabilities on stealth, and that before that they had no prior knowledge or capability. That's not how R&D cycles work. You also assume that R&D and knowledge development go at the same pace for every player at any point in time. That has generally not been true, historically.

 

[FORBIN]

You assume 1) their first stealth fighter is also their first foray into stealth. That's not how R&D

You invent things to try to make them believe, answer to your own questions , better don' t bored me with it.

 

[latenlazy]

You invent things to make them believe, answer to your own questions , better.

I accidentally hit submit before finishing that post. You may want to read it again.

And I'm not inventing anything. I pay attention to how technology and innovation works, and the historical record tells us that technological laggards don't always stay laggards, and state of the art is never durable. The Soviets beat the Americans to space. Did that last?

 

[FORBIN]

@latenlazy: The J-31, if it's designed with attention to its RCS, is potentially stealthier than the J-20, not only because of its cleaner design, but also because it is a somewhat smaller aircraft.

As to the J-31 being preferred over the J-20's configuration, the J-31 is not considered supermaneuverable with neither canards nor TVC. It is designed for TVC, but we have yet to see a TVC Chinese aircraft.

Regarding epistemology, what you're basically saying is that mathematics is impossible because you can't compile axioms into theorems. Between the Kopp simulation, the Taiwanese simulation, and the Chinese simulation of the F-22, it's reasonable to assume that the J-20, without RAM, is 5-10 dBsm less stealthy than comparable US fighters.

The 1st J-31 is very bad for RCS especialy rear now the 2nd frontal i think better but the rest ?
but he have more clean shapes than J-20 no canards etc...

 

[latenlazy]

@latenlazy: The J-31, if it's designed with attention to its RCS, is potentially stealthier than the J-20, not only because of its cleaner design, but also because it is a somewhat smaller aircraft.

As to the J-31 being preferred over the J-20's configuration, the J-31 is not considered supermaneuverable with neither canards nor TVC. It is designed for TVC, but we have yet to see a TVC Chinese aircraft.

So are you saying we have no reason to believe China can't achieve RCS designs comparable to the F-35 or F-22?

Regarding epistemology, what you're basically saying is that mathematics is impossible because you can't compile axioms into theorems. Between the Kopp simulation, the Taiwanese simulation, and the Chinese simulation of the F-22, it's reasonable to assume that the J-20, without RAM, is 5-10 dBsm less stealthy than comparable US fighters.

In mathematics you compile axioms into theorems by proving the logical self consistency of the axiom. If your axioms are wrong your theorems are nonsense. The axiom of a model is the model assumptions. Model assumptions, unless rigorously and comprehensively mapped to the actual case they are trying to model, maintain consistency with itself but may have no bearing on reality. Drawing conclusions off models that haven't had their assumptions proven true to reality is circular logic. It doesn't tell us anything about the actual thing we're interested in. If you presume something can be described by some equation but you get the equation wrong the output is going to tell you nothing about the thing you're interested even if it can tell you plenty about itself. Garbage in garbage out. Kopp knew this, which is why he heavily caveated his study, and yet even he concluded the J-20's basic design is capable of VLO RCS. To boot, the model he tested turned out to be a demonstrator design, and not the modified production design we see today.

Furthermore, if you have no actual method or process for comparing models outcomes that employ different methodologies you have no grounded epistemology to conclude how to weigh and reconcile different results. All you're doing is arbitrarily inventing baseless ways to fit model outcomes together with no reasoned grounds. If you want to average the model outcomes, what is your basis for believing that reality reflects the average? If you want to give one model outcome more weight than the other, what is your basis for concluding the degree of the weighting?

 

[latenlazy]

The 1st J-31 is very bad for RCS especialy rear now the 2nd frontal i think better but the rest ?
but he have more clean shapes than J-20 no canards etc...

RCS can't be eyeballed by noting superficial features and details. Older VLO designs employed simpler rules and heuristics in part because computing wasn't as powerful, so it was harder to optimize RCS for complex shapes. That's not the world we live in today.

 

[vesicles]

Typically with models, everything has to be taken with a grain of salt. Because of that, each model must be validated extensively to see if the model can replicate known data and experimental outcome. Once the validation is done, then we can move on to predicting the unknown.

In this case, has the Taiwanese team validated their model? How did they do the validation? Did they use their model to calculate the F-22 and F-35 RCS? Did they have any control in their modeling, such as the F-15/F-18?

Using rumored data from other sources is not the correct way to evaluate a model's validity. Everything must be generated from a single model in question and then compared. The J-20, along with the F-22, F-35, F-15 and a Boeing 747 (positive control) and possibly some kind of stealthy UAV as a negative control. Everything must be compared together.

So has the Taiwanese model in question done these? If they have and their data for positive and negative controls are close to those known in the industry, then their data on the J-20 is believable. If not, then no need to discuss further. If they haven't done any validation, then no need to talk about any of this.

Showing/generating a single data point without any controls and reference is pointless.

 

[FORBIN]

Typically with models, everything has to be taken with a grain of salt. Because of that, each model must be validated extensively to see if the model can replicate known data and experimental outcome. Once the validation is done, then we can move on to predicting the unknown.

In this case, has the Taiwanese team validated their model? How did they do the validation? Did they use their model to calculate the F-22 and F-35 RCS? Did they have any control in their modeling, such as the F-15/F-18?

Using rumored data from other sources is not the correct way to evaluate a model's validity. Everything must be generated from a single model in question and then compared. The J-20, along with the F-22, F-35, F-15 and a Boeing 747 (positive control) and possibly some kind of stealthy UAV as a negative control. Everything must be compared together.

So has the Taiwanese model in question done these? If they have and their data for positive and negative controls are close to those known in the industry, then their data on the J-20 is believable. If not, then no need to discuss further. If they haven't done any validation, then no need to talk about any of this.

Showing/generating a single data point without any controls and reference is pointless.

As with submarine for noise for these stealth aircrafts ofc you can't be completely certain but your point is good
In more with the progress of radars they can be in danger to mid term for about 10 years ? actualy seems sometimes some are detected during a moment but don't means tracked in fact the SAM have a fire solution can really destroy Aircraft.

Now if Chinese have build a stealth proof they are not outdated... in more SAMs sytems are much less expensive but less versatile mainly defensive despite that the last S-400 with such a range are capable do air interdiction even over ennemy countries i means.

And solution for this type is surely now with new active systems to provide better stealth, some say B-2 use plasma ??? in anyways no Aircraft is invulnerable, less clearly but less detectable.