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

[Inst]

Well, uhhh, radar transparent versus radar absorbent materials? When do you use radar transparent (which is closer to radar translucent), when do you use radar absorbent?

If you're doing a complex optimization problem between range, payload, weight, RCS, radar, maneuverability, at some point in time you will compromise RCS, if you don't make it the #1 priority, as with the B-2.

This creates problems, meaning that you will want to try to use various materials to patch up the issue.

Further, radar absorbent paint tends to be heavy; it's impregnated with metal and adds significant weight to the airframe. Compare the YF-22 to the F-22; almost ten thousand kg were added between prototype and production.

When is the correct time to use RAM? When can you skimp on it as a cost / maintenance / weight reduction method?

 

[latenlazy]

Well, uhhh, radar transparent versus radar absorbent materials? When do you use radar transparent (which is closer to radar translucent), when do you use radar absorbent?

If you're doing a complex optimization problem between range, payload, weight, RCS, radar, maneuverability, at some point in time you will compromise RCS, if you don't make it the #1 priority, as with the B-2.

This creates problems, meaning that you will want to try to use various materials to patch up the issue.

Further, radar absorbent paint tends to be heavy; it's impregnated with metal and adds significant weight to the airframe. Compare the YF-22 to the F-22; almost ten thousand kg were added between prototype and production.

When is the correct time to use RAM? When can you skimp on it as a cost / maintenance / weight reduction method?

Again, not like Chinese analysts would be shooting in the dark. They have their own scientists and engineers. More often than not figuring out the science that tells you the ideal solution happens much sooner than realizing the engineering of the solution. In China's case we know they already have some (if not total) grasp of the engineering as well.

 

[Inst]

The way I think is that the Chinese engineers and scientists aren't God, though. If they were so good at reverse-engineering other people's technology, why is the WS-10A still in limited deployment and why is the J-10 still using AL-31FNs?

Especially with stealth, where the small details matter the most, I don't think the Chinese engineers would be able to get anything more than just a rough estimate of the counterparty RCS.

If the Americans tell you the F-22 is at peak RCS .0001 M^2, then they could be obfuscating or lying.

If the Chinese tell you the F-22 is at peak RCS .4 m^2, they could be obfuscating or lying, or they could just plain be wrong due to not having all the intelligence on the F-22 design and the micro-details on the F-22 stealth coatings.

 

[latenlazy]

The way I think is that the Chinese engineers and scientists aren't God, though. If they were so good at reverse-engineering other people's technology, why is the WS-10A still in limited deployment and why is the J-10 still using AL-31FNs?

Especially with stealth, where the small details matter the most, I don't think the Chinese engineers would be able to get anything more than just a rough estimate of the counterparty RCS.

If the Americans tell you the F-22 is at peak RCS .0001 M^2, then they could be obfuscating or lying.

If the Chinese tell you the F-22 is at peak RCS .4 m^2, they could be obfuscating or lying, or they could just plain be wrong due to not having all the intelligence on the F-22 design and the micro-details on the F-22 stealth coatings.

Because, as I said earlier, understanding how a technology works and being able to engineer the solution are two different things. The knowledge requirements for doing a computer simulation is lower than reverse engineering, since one only requires you to plug in the measurable properties of a material you're interested in into the simulation, while the other actually requires figuring out the process by which the material is made. Its not uncommon for one engineer to look at a solution and understand how it works, but still have difficulty replicating it themselves.

Frankly speaking, I would actually rank the difficulty of engine technologies as much greater than stealth technologies. Developments in the former require state of the art and difficult to replicate materials. The latter mostly just requires a very powerful computer, which was hard to come by in the 70s but common place nowadays.

Anyways, I'm simply pointing out that it's not outside reasonable possibility that China has a very good rough idea for what the F-22 looks like on radar. I addressed the trade show advertising point way back when when I said neither US nor Chinese figures give us a full picture, especially since RCS isn't one single number, but a whole set of values under specifically defined conditions.

Side note-The WS-10A isn't a reverse engineer of anything, and it's not like Chinese engineers on broad base have an attention deficit compared to their American counterparts. Attention to detail is an aspect of individuals, not the population of countries.

 

[Engineer]

The way I think is that the Chinese engineers and scientists aren't God, though. If they were so good at reverse-engineering other people's technology, why is the WS-10A still in limited deployment and why is the J-10 still using AL-31FNs?

Especially with stealth, where the small details matter the most, I don't think the Chinese engineers would be able to get anything more than just a rough estimate of the counterparty RCS.

Irrelevant question. China is not reverse-engineering anything from the F-22.

If the Americans tell you the F-22 is at peak RCS .0001 M^2, then they could be obfuscating or lying.

If the Chinese tell you the F-22 is at peak RCS .4 m^2, they could be obfuscating or lying, or they could just plain be wrong due to not having all the intelligence on the F-22 design and the micro-details on the F-22 stealth coatings.

Firstly, the Chinese documents are meant for internal use, not really meant for external consumption. As such, there would be less necessity to inflate F-22 RCS numbers to promote a product. Also, the 0.4 m[sup]2[/sup] value could be an averaged or perhaps maximum RCS value. Of course, we have no way of knowing.

Secondly, and most importantly, there is no need to have all details regarding the F-22 down to the molecular structure to generate good RCS estimates. The reason has already been explained multiple times in the past.

 

[Skywatcher]

Secondly, and most importantly, there is no need to have all details regarding the F-22 down to the molecular structure to generate good RCS estimates. The reason has already been explained multiple times in the past.

People use all sorts of ridiculously outside the context claims all the time even in internal and official solicitation/update documents (usually for funding purposes). Ask the DoD about various contractor shenanigans, chances are that its just as common in the PRC.

After all, if NRIET/Raytheon claimed that the F-22A/J-20 had a RCS of 0.1m2, they could be telling the truth, but the major caveat is that such an RCS figure comes from the rear angle (where the engine fan blades are directly exposed to enemy radar).

A 0.1m2 RCS is nice and all, but it won't be very helpful in BVR combat at 30 km, 40 km out.

 

[rhino123]

The way I think is that the Chinese engineers and scientists aren't God, though. If they were so good at reverse-engineering other people's technology, why is the WS-10A still in limited deployment and why is the J-10 still using AL-31FNs?

First off... how do you know that WS-10A is a reverse engineered product. Plus, you do know that one of the most important thing about modern engine is material science which is almost impossible to reverse engineered, unless you already process the manufacturing infrastructure, knowledge and skills... and if you already have the above three, then you wouldn't need to reverse engineered other people's products, right?

Especially with stealth, where the small details matter the most, I don't think the Chinese engineers would be able to get anything more than just a rough estimate of the counterparty RCS.

If the Americans tell you the F-22 is at peak RCS .0001 M^2, then they could be obfuscating or lying.

If the Chinese tell you the F-22 is at peak RCS .4 m^2, they could be obfuscating or lying, or they could just plain be wrong due to not having all the intelligence on the F-22 design and the micro-details on the F-22 stealth coatings.

Well... I pointed that out too in the past, Engineer and Latenlazy had given very good explanation, I would urge you to read those.

As to the American might be lying... well... you must first have knowledge on the topic, which I believe the Chinese did, or their won't have developed their own RAM coating, so the lies can easily be broken or the Chinese don't even need to know the true exact property of the RAM because it is science and it wouldn't go that far out.

Although Stealth shapes of aircraft is very important, but... if you looked at different stealth design, they all somehow shared some very similar shapes, because it is only these shapes that you can actually improve the stealth capability of an aircraft, so the Chinese again doesn't really need to know everything of F-22 or F-35 to get a rough idea of the RCS.

And lastly... (I really don't want to bring this up, but... well... what the heck), as some good forum member had never failed to point out... there are still the case of cyber-episonage.

 

[Skywatcher]

Frankly, all we have is a defense contractor claim that the F-22A has a RCS of 0.1m2. Which, if actually applicable to combat situations, would mean that the USAF has wasted billions of dollars on a fighter that is about as stealthy as the Eurofighter Typhoon.

Now, a comparable example would be this. Lockheed Martin could claim that they can take out the targeting system and communications of the AShBM using the electronic warfare suite of the AEGIS system because of the digital architecture of Chinese C41 system.

Of course, in that case, LM would have to definitively know all about the Chinese C41SR system's operations, a system which just like the F-22, is undergoing continual upgrades and modifications.

Does that sound rational?

 

[Engineer]

Frankly, all we have is a defense contractor claim that the F-22A has a RCS of 0.1m2. Which, if actually applicable to combat situations, would mean that the USAF has wasted billions of dollars on a fighter that is about as stealthy as the Eurofighter Typhoon.

An alternate possibility is that the stealthiness of the Eurofighter Typhoon was very inflated, just like the 0.0001 m[sup]2[/sup] value quoted for F-22. However, that would be an entirely different discussion.

Now, a comparable example would be this. Lockheed Martin could claim that they can take out the targeting system and communications of the AShBM using the electronic warfare suite of the AEGIS system because of the digital architecture of Chinese C41 system.

Of course, in that case, LM would have to definitively know all about the Chinese C41SR system's operations, a system which just like the F-22, is undergoing continual upgrades and modifications.

Does that sound rational?

The C4ISR doesn't have an external shape to being with. Even if there is, the performance of the C4ISR is not related to the external features. So your example isn't a valid comparison.

 

[TerraN_EmpirE]

The USAF has and operates foreign radar systems as part of its R&D assets and labs. When raptor was designed they ran models of her though testing using those same systems. Same for F35 and every other stealth assets in the inventory. Those who question the level of the raptors stealth I remind you that both the J20 J21 and Russian Pak FA use almost identical architectural to achieve there stealth. I also remind you that Lockheed martin invented stealth as we know it today, stealth however is not perfect. You need the right tactics. Point a radar at the bottom or top of any stealth and its visible. Stealth is optimized for head to head side to side sweeps. An we have yet to develop true counter IR and visual stealth. The science is of course always changing. New coatings defended counter defended are always on the work.