J-20... The New Generation Fighter III

Originally Posted by Martian

Typical endless criticism. You go draw the V-tails. These things take forever. I made the post to educate the majority of readers on planform alignment. That is the purpose. I don't care whether the reader concludes which plane is better. That is not the point.

After an objective analysis, the Pak-Fa/T-50 clearly had more reflective angles than the J-20 and F-22. It is silly to withhold a conclusion to be politically correct. However, the value of the post is to shed light on the topic of planform alignment.

Well then post the information in the military FAQ thread or something, because what I see is superficially blowing J-20s horn while prodding T-50 with a stick. The premises are fine, the conclusion from them isn't. It's not like people don't have access to wikipedia themselves either...
You should join key forums and post these analyses up there, I'd be interested to see some of the members' reactions over there.
And I believe line black is parallel to purple/scarlett and light blue.

EDIT:

It might've been wiser to use this picture as your PAK FA case study, given there's less of an tilt of the actual aircraft from the camera. I think in this case it's still hard to tell if red is indeed parallel with white. But black is definitely parallel to purple.

This thread is about J-20 and stealth technology. If you don't like my posts, don't read them. How many times do I have to keep saying that? And I couldn't care less what you think, I'm going to keep posting until a moderator tells me that I have violated a forum rule, which has never occurred.

Got it? I'm tired of repeating myself over and over again.

Latenlazy's criticism was wrong. Since he magnified the picture, his eyes should have easily seen that my analysis was correct. Instead, he tried to inject uncertainty into my analysis and wasted my time to prove him wrong. He already knew the truth. The answer is easily discernible with his eyeballs.

You two are constant burrs on my tail. I'm trying to illuminate the topic of stealth for the majority of the readers and you two keep posting comments with no insightful information. Go bother someone else.

Originally Posted by Martian

This thread is about J-20 and stealth technology. If you don't like my posts, don't read them. How many times do I have to keep saying that? And I couldn't care less what you think, I'm going to keep posting until a moderator tells me that I have violated a forum rule, which has never occurred.

Got it? I'm tired of repeating myself over and over again.

Getting back on topic, in the latest image that Blitzo posted, the black does look aligned with the purple, and you're right that the red still doesn't look aligned to the white.

Originally Posted by Martian

This thread is about J-20 and stealth technology. If you don't like my posts, don't read them. How many times do I have to keep saying that? And I couldn't care less what you think, I'm going to keep posting until a moderator tells me that I have violated a forum rule, which has never occurred.

Got it? I'm tired of repeating myself over and over again.

It's not that you shouldn't post, but that if you post you should be mindful of accuracy. These are valid and constructive criticisms, and good things to think about to get a broader understanding of a subject.

J-20 Mighty Dragon DSI and S-duct design is superior to F-22 S-duct-only design

The J-20 Mighty Dragon is a truly modern design. The old F-22 Raptor really shows its age when we compare the S-ducts for the world's two premier stealth fighters.


J-20 Mighty Dragon incorporates advanced DSI to dramatically increase the stealthiness of its S-duct design.


J-20's combined DSI and S-duct design forces radar waves to travel a circuitous path of five reflections before they can strike the engine fan blades.


Lacking an advanced DSI, the F-22 is helpless from preventing radar waves in traversing the shortest path to reach the F-22 engine fan blades in only two reflections.

The following calculations will show the massive advantage in the stealthiness of the J-20 S-ducts, when compared to the F-22.

The effectiveness of RAM coating is a 99.684% reduction (or 0.00316 left) in radar energy (see citation below). For radar energy entering the J-20 S-duct, it must undergo a minimum of five reflections before it strikes the engine fan blades. The shortest path to exit the J-20 S-duct is to reverse course and escape in another five reflections. The total minimum number of reflections is ten.

To calculate the amount of the original radar energy that entered the J-20 S-duct and was able to egress/reflect out of the S-duct after striking the engine fan blades, we have to reduce the original radar energy by 10 reflections from the RAM coated S-air duct walls.

Amount of original radar energy that can escape J-20 S-duct = (0.00316) ^ 10 = 9.93 x 10E-26

Since incoming radar waves can escape the F-22 S-duct in only four reflections, the attenuation of the enemy radar waves is inferior to the J-20 by many magnitudes.

Amount of original radar energy that can escape F-22 S-duct = (0.00316) ^ 4 = 9.97 x 10E-11

The effectiveness of the J-20 DSI and S-duct design is approximately 1 x 10E15 times better than the F-22 S-duct-only design or 1,000,000,000,000,000 times stealthier.

Admittedly, the amount of radar energy escaping from the S-ducts of the J-20 and F-22 are both extremely low and virtually undetectable. Nevertheless, from a stealth design standpoint, the J-20 is clearly far superior.

----------

Citation for RAM coating reduction of 99.684% reduction in radar energy.

From my February 12, 2011 post:

Revised final estimate for J-20 canards' radar return energy is 1.035 x 10^-17

I find Gambit's arguments for a -25 dB reduction, instead of -50 dB, from RAM coating to be convincing. I have revised my calculations for the effect from China J-20's canards. Quickie is correct that -25 dB is equivalent to 99.684% reduction (e.g. 10^2.5; take inverse; and convert to percentage). Thank you to Delft for highlighting the issue.
...
After hitting the canards, we know that 99.684% of the reflected energy is reduced by the military-grade RAM. (See Radar-absorbing materials: Definition from Answers.com) This means that only 0.00316 (e.g. 1 - 0.99684 = 0.00316) of the impacting radar energy survives contact with the canard's RAM surface.

Originally Posted by gambit

Even if you do not have relevant experience in the field, IF you actually read your source carefully, scant as it is, you would not have made the ridiculous claim that an airborne absorber would affect up to five-9s of the impinging signal.

Your quite general source reads...


The quarter wavelength rule is quite applicable to airborne absorber. As material DECREASING thickness approaches quarter wavelength of the targeted freq, absorber performances decreases. In most cases, the targeted freq is the X-band, which is the centimetric (cm) band. We found out a long time ago that increasing thickness to greater than quarter wavelength would incur an unacceptable weight penalty, especially if the absorber is of the magnetic type, which are ferrite particles in a dielectric containment, aka sheet or liquid applique.

Here is a source to prove that...

HYFRAL™ CATALOGUE - Types of absorbers (THEOREMS AND PRINCIPES) - ELECTROMAGNETIC ABSORBERS


The only type of absorber that can affect up to five-9s of the impinging signal would be the pyramidal type...



Absorber performance is highly dependent upon the targeted freqs, even if it is 'wideband'.

Here is an F-22 in an EM anechoic chamber...



All those pyramidal absorbers would give us the most accurate RCS measurement of any object since they will absorb any chamber walls reflections that could constructively interfere with the reflections off the aircraft.

If absorber in general would affect five-9s of the impinging radar signal as you (falsely) claimed, there would be no need for shaping at all since whatever left of the signal -- the echo -- would lose even more energy on the way back to the seeking radar. What is that about energy loss to the square of the distance rule? Why not coat the whole aircraft with the stuff instead of just the canards? If this is true, we would have never built the F-117 in the first place looking funky as it is?

Originally Posted by Martian

This thread is about J-20 and stealth technology. If you don't like my posts, don't read them. How many times do I have to keep saying that? And I couldn't care less what you think, I'm going to keep posting until a moderator tells me that I have violated a forum rule, which has never occurred.

Got it? I'm tired of repeating myself over and over again.

Of course I'm not saying you can't, heaven forbid. But I'll challenge specific conclusions of these analyses which I believe are flawed. As you said it was to educate the majority of readers, well we dont' want a legion of readers that believe a few more aligned edges inherently results in being more susceptible to detection (ie greater RCS), without taking in other factors yes?

Nevermind what bias prevalent for J-20 and against T-50 >_>

Latenlazy's criticism was wrong. Since he magnified the picture, his eyes should have easily seen that my analysis was correct. Instead, he tried to inject uncertainty into my analysis and wasted my time to prove him wrong. He already knew the truth. The answer is easily discernible with his eyeballs.

You two are constant burrs on my tail. I'm trying to illuminate the topic of stealth for the majority of the readers and you two keep posting comments with no insightful information. Go bother someone else.

Maybe you should look over your analyses a bit more carefully before posting it for people to criticize or take criticism without complaining? It's not like we're taking a cheap shot to you, just pointing out a few places where you might want to edit. Sheesh.

Originally Posted by kyanges

Getting back on topic, in the latest image that Blitzo posted, the black does look aligned with the purple, and you're right that the red still doesn't look aligned to the white.

I am willing to concede that in Blitzo's picture, the Black does look aligned with the Purple edge. This reduces the Pak-Fa/T-50's distinctive wing edges from 11 to 9. It is still four more than the J-20 and F-22. My purpose is to illuminate the topic of planform alignment and let you analyze it yourself, which you have just done.

Ps. A correction. When I said purple and white I meant pink and white. Didn't realize you used a different shade on another edge.

Originally Posted by Martian

J-20 Mighty Dragon DSI and S-duct design is superior to F-22 S-duct-only design

The J-20 Mighty Dragon is a truly modern design. The old F-22 Raptor really shows its age when we compare the S-ducts for the world's two premier stealth fighters.


J-20 Mighty Dragon incorporates advanced DSI to dramatically increase the stealthiness of its S-duct design.


J-20's combined DSI and S-duct design forces radar waves to travel a circuitous path of five reflections before they can strike the engine fan blades.


Lacking an advanced DSI, the F-22 is helpless from preventing radar waves in traversing the shortest path to reach the F-22 engine fan blades in only two reflections.

I would challenge this analysis solely base on the fact that we don't have a cutaway of the plane and therefore don't know the geometry of each respective plane's inlet tunnel.

Both the J-20 and PAK-FA are currently prototype aircraft. I wouldn't read too much into it until the production variant is out.

^^some do try very hard doing otherwise
spending hours in fact
what are they usually called? hmm... fanboys!

Originally Posted by latenlazy

I would challenge this analysis solely base on the fact that we don't have a cutaway of the plane and therefore don't know the geometry of each respective plane's inlet tunnel.

How about common sense? The engines require a massive amount of air. There exists a large duct to allow air to flow from the air inlet to the engines.

so common sense gives you extra sensory vision capable of lining out F-22's intake and inlet shape from a JPEG

There exists a large duct to allow air to flow from the air inlet to the engines. (in almost every high performance jet fighter aircraft)

sorry making cheapshots at you Martian, others are quite tolerant to you, but your posts are just as cheap
SDF does not need them

Originally Posted by Martian

How about common sense? The engines require a massive amount of air. There exists a large duct to allow air to flow from the air inlet to the engines.

You don't need to squeeze the inlet tunnel volumetrically to geometrically block radar signals. Besides, we know for a fact that the inlet tunnel is also meant to help compress the air going to the tunnels. Volumetric compression can serve that purpose.

Furthermore, knowing the internal structure of the inlet tunnel would help us understand how internal features can dissipate radar energy. Remember it's not about how much radiation goes in, but how much comes out.