99 replies to this topic

[Martian]

New J-20 Mighty Dragon prototype aircraft number "2002"


A new J-20 Mighty Dragon prototype has been unveiled.

[Note: Thank you to SiegeCrossbow for the picture.]

[Martian]

China waits for WS-15 supercruise engine prior to installing F-22 2D engine nozzles


China is most likely waiting for the supercruise WS-15 engine prior to installing flat F-22 style 2D engine nozzles.

There is one minor and one major stealth design deficiency on the J-20 that makes it inferior to the F-22. Australia Air Power identified a minor curve on the side airduct of the J-20, which will reflect radar at an additional (or broader) angle.

The major design problem is the LOAN engine nozzles on the J-20. In rear aspect stealth, the J-20 is comparable to the F-35. However, it does not match the F-22.

In my opinion, China already possesses the technology to build flat 2-D F-22 style engine nozzles. We've seen the pictures (see below). The problem is the power output of China's turbofan engines. The WS-10A is sufficiently reliable to be installed on Chinese fighters. However, we are years away from seeing reliable high-performance supercruising WS-15 engines.

Since flat 2-D nozzles are heavier and impose a performance & fuel efficiency penalty (which is obvious because of the constricted thrust emission), an advanced powerful engine is needed to overcome the performance penalty without compromising maneuverability, speed, and service ceiling.

Citation: http://www.angelfire.../fighterplanes/

"It's known that flat nozzles reduce the thrust of an engine from 14%-17%."

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China's "WS-10A turbofan engine is said to have 13.2 ton maximum thrust" (shown above). China needs the more advanced WS-15 supercruise engine with 18 tons of maximum thrust.

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China's great hope to match F-22 2D flat nozzle technology





The pictures are from 1995 and it shows China's research into a flat-nozzled (or F-22 type) TVC wide-band stealth design. The current J-20 and F-35 LOAN (Low-Observable Asymmetric Nozzle) technology is only narrow-band stealth (in two bands, X and Ku).

[Note: Thank you to HouShanghai for the pictures.]

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To answer your question directly, a new "2002" J-20 prototype will incorporate all of the improvements to fix the flaws that were discovered during flight tests over the past year. However, we expect a smooth process because China has previously undergone a similar procedure with the J-10 Vigorous Dragon.

I will mention just some of the areas where improvement is expected.

1. Fly-by-wire control performance. Software code was most likely tweaked to optimize performance or rewritten to overcome problems discovered during flight tests.

2. Modifications to engine.

3. Flight control surfaces.

4. RAM coating formula, thickness, or application process.

5. Changes to more tightly integrate the performance of the different subsystems.

6. Placement of location of sensors or redesign sensors to maximize performance.

7. Perhaps radar orientation needs to change to maximize coverage.

8. Changes to HUD or cockpit multi-function displays (e.g. content or display order).

9. There might have been minor changes to canard or main wing size, shape, or thickness. The internal structure might have been slightly altered to improve aerodynamic performance.

10. Second prototype could include more composite materials or other advances developed during the past year.

I could keep extending the list, but it's all speculation. These are routine issues that have to be addressed in a new combat aircraft. Unfortunately, most of these changes are all internal.

If there are external changes to the aircraft, I'll comment on them when I see a complete photograph.

[Siddharth]

Man... looks like stealthy paint is chipping already.

And these much touted silver nozzle engines looks like regular Russian engines with silver paint on them.

[Martian]

1. The chipped paint problem has been fixed. Newer pictures do not show this problem from 12 months ago.

Why are you posting old news? The chipped paint picture was first posted on April 18, 2011.

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2. The F-22 also had problems with its maintenance/RAM coating (see http://www.washingto...9070903020.html or http://www.warfaresims.com/?p=755).

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3. Regarding the silver engine nozzles, it is clear they are Chinese engines and distinct from Russian AL-31F engines. Can I prove that it is a WS-10 variant (e.g. WS-10G) beyond the shadow of a doubt? No.

However, your suggestion of silver paint is ridiculous. Paint would burn off under the tremendous heat of 3,000 degrees Fahrenheit from the jet engine exhaust (see http://www.0x4d.net/...egment%2011.pdf). A silver-colored alloy is a hallmark of Chinese engines. In contrast, your eyes can obviously see that the AL-31F engine alloy has a black color.

According to GlobalSecurity, the WS-15 core engine was first tested in April 2005 (see http://www.globalsec.../china/ws15.htm). According to Richard Fisher at International Assessment and Strategy Center, the WS-15 prototype engine was ready around 2009 (see http://www.strategyc.../pub_detail.asp).

There are two prototype J-20 Mighty Dragon stealth aircraft. One of the J-20s is equipped with Russian AL-31F engines. The other J-20 is equipped with Chinese engines.


The silver engines on the left are domestic Chinese turbofan engines. They could be a WS-10 variant or the WS-15 engine. The dark engines on the right are Russian AL-31F engines.

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WS-10A engines are already in mass production (see picture below).


Could the WS-10A engine power the J-10, J-11B, and J-15 aircraft? The answer is "yes" if two conditions are met. Firstly, Chinese production of WS-10A engines must be sufficient to meet the demand (including production of parts for maintenance and replacement engines at the end of the expected lifetime) for all three aircraft.

Secondly, I don't know if WS-10A engines are interchangeable with AL-31F engines. If they are not readily interchangeable without modifying the fuselage then the current fighters with AL-31F engines will most likely stay with AL-31F replacement engines.

J-10B Vigorous Dragon flying with WS-10A engines

J-11B flying with WS-10A engines

J-15 Flying Shark with WS-10A engines

To conclude the discussion on the use of domestic WS-10A engines on the J-10, J-11B, and J-15, there is a new photograph of a J-11BS equipped with WS-10A engines.

"A [J-11BS] tandem twin-seat combat-capable training aircraft for J-11B pilots."

[Note: Thank you to SiegeCrossbow for the J-11BS picture.]

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WS-10A engine for J-10B Vigorous Dragon fighter in mass production

WS-10A engine (with gearbox at the bottom) is designed to power the J-10B Vigorous Dragon fighter. This version of the WS-10A turbofan engine is said to have 13.2 ton maximum thrust. There are several wrapped engines near the floor.

[Note: Thank you to Pinko for the post.]

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J-10A and J-10B Vigorous Dragon evolution

The top photo is a J-10A with AL-31F engine. The second and third photos show a J-10B with DSI intake and AL-31F engine. The fourth photo is a J-10B with China's domestic WS-10A engine.

This sequence of pictures illustrates the evolution of the J-10 family from a J-10A (with AL-31F engine) into a J-10B with advanced DSI technology and WS-10A engine.

In the sequence of photographs, it is easy to distinguish between the AL-31F and WS-10A engines. The "flexible petals" on the WS-10A are a lot shorter than on the AL-31F.


Comparison of Chinese WS-10A (top) and Russian AL-31F (bottom) jet engines.

[Note: Thank you to HouShanghai for the first picture and Maya for the engine comparison picture.]

[macau boy]

Thx, Martian, for the very clear and side-by-side comparisons. A couple of pictures are better than a million words.
Let those naysayers continue their wet dreams forever.

[BaburMissile]

Marvelous rebuttal Martian. Right on the money.

[gnak]

i still think the j-20 is powered by al-31 or some derivative at the moment

these comparison pictures below (i can't read chinese, assuming the message is same engine)



video of j-20 engine start (agian i cant read chinese so i assume they saying j-20 powered by al-31)



that being said j-20 is still better than anything india can build at the moment

and eventually a domestic engine will be available

[Martian]

The argument that the J-20 Mighty Dragon is powered by two versions of the AL-31F engine is ridiculous. Our eyes can easily distinguish between a black alloy AL-31F engine and an unknown silver alloy engine. We know for a fact that the Chinese WS-10A has silver alloy engine nozzles.

The Russian media have publicized the export of only the AL-31F type engine to China. It is a crazy argument to claim there are two radically different AL-31F engines being equipped on the J-20.

Citation for Chinese purchases of only Russian AL-31F engine: http://www.9abc.net/.../archives/61933

There are only two possibilities. Either both sets of engines should be black AL-31F alloys or you acknowledge the black AL-31F engine and the Chinese silver alloy engine. I've already demolished the stupid theory of silver paint on 3,000 degrees Fahrenheit engine nozzles.

Also, if the Chinese silver alloy engines were of Russian origin then the Russian media would be crowing about it. The silence from the Russian media is deafening.

If you want to keep spreading the b.s. rumor that the silver alloy engines are Russian then prove it with a citation of a billion dollar export to China of another advanced high-performance Russian engine with silver nozzles.

Given the facts to date, the most reasonable conclusion is the J-20 silver engines are a WS-10 variant. This is consistent with Chinese technology, which results in silver engine nozzles like the WS-10A. Also, it makes sense to test a foreign engine with proven reliability and to simultaneously test a new domestic engine. We've previously seen China perform dual track engine tests on the J-10 and J-11 with Russian and Chinese engines.

The conclusion of one J-20 being equipped with Russian AL-31F engines and another J-20 being equipped with Chinese WS-10 variant engines has been reported by the media.

http://www.offiziere.ch/?p=7634

"Second Copy of Chinese Stealth Fighter Enters Testing?
Posted on April 2, 2012
by DAVID AXE
...
The appearance of “2002,” which apparently has not yet flown, follows speculation that 2001 is actually two aircraft wearing identical markings. Photographs have depicted a J-20 marked with “2001″ operating with two different engine types: apparently the Russian-made AL-31 and the Chinese WS-10, itself a derivative of the AL-31. It’s possible there’s just one 2001 and it has experienced at least one engine change, in the same way that some Western fighters such as the F-15 are compatible with more than one engine type.

If “2001″ is two aircraft each uniquely fitted with separate engine types, it’s not clear why the Chinese air force would insist on subterfuge to mask the true number of J-20 test models. It’s widely believed that the Chinese military deliberately shows off the J-20s to amateur photographers in order to impress foreign audiences. None of the scores of published photos of the Annihilator have shown two copies of the plane in a single frame.

The few photographs of “2002″ do not clearly depict the engine nozzles, so it’s not clear if the new plane is fitted with AL-31s or WS-10s. AL-31s seem more likely, as China has reportedly experienced problems building reliable fighter engines on its own and continues to import Russian-made models.

In any event, the J-20 is years from achieving operational status, if indeed it ever enter service. Stealth aircraft can require thousands of hours of development flying; in its first year the J-20 reportedly racked up an estimated 60 flights, each probably an hour or so in duration. The addition of a second J-20 could double the testing rate, but even with several airframes full development could take five years or more."

[Siddharth]

Martin buddy, why it's ridiculous? Pic I posted and which GNak elaborated on is also from Chinese source!

You flooded last page with edited images and no one said a thing.

But can you refute following image?

And how do you know poor paint on stealthy plane is fixed?

gnak, on 04 April 2012 - 02:01 PM, said:

i still think the j-20 is powered by al-31 or some derivative at the moment

?

[Martian]

1. I have already explained to you that China only imported one type of Russian engines, the AL-31F. I'm not going to explain again to you why paint cannot survive 3,000 degrees Fahrenheit. Show me a citation of paint that can survive those incredible temperatures. By definition, paint is a thin coating with an even thinner adhesive/boundary layer. No paint material can absorb those sustained levels of heat without being burned off. It's called thermodynamics.

2. I have thoroughly explained the lineage of Chinese WS-10A engines with silver alloy engine nozzles.

3. I have explained the silence from the Russian media in not claiming credit for the silver engines.

4. I have provided a reference to a published article to show that it is widely acknowledged among mainstream observers that the silver engines are a WS-10 variant.

5. The silver engine nozzles are clearly not AL-31F. The silver engine nozzles have F-35 type stealthy serrated edges/teeth. The AL-31F engines have rounded edges.

To clarify, the silver engines are not WS-10A. It could be the WS-10G variant or the WS-15. To reiterate, I cannot prove this beyond the shadow of a doubt. However, reasonable people collect all of the information and make an informed judgment.

It makes no sense to intentionally paint engine nozzles a silver color. Firstly, I don't believe paint exists that can consistently withstand 3,000 degree Fahrenheit repeatedly for an hour at a time. Secondly, painting AL-31F engines into a silver color is harmful to visual stealth.

The most likely explanation is the engine nozzles are silver and more easily seen by the naked eye of an enemy fighter pilot, because Chinese technology evolved with a silver-colored metal alloy. This is a detriment and no sane person would intentionally paint visually-stealthy black AL-31F engine nozzles into a silver color.

The bottom line is the production version of J-20 will be equipped with Chinese WS-15 supercruise engines. I do not find it useful to argue endlessly about an interim engine.

This is my last response to rabid anti-Chinese conspiracy theorists. You are always free to believe whatever you like.

[Siddharth]

We are not talking about articles you have posted or some text, but we are merely discussing picture we have posted.

All information on web regarding J-20 is till assumptions and theory (specially regarding its stealth and engines). It's not wise of you to call any other point of view "rabid anti-Chinese conspiracy theory" just because you don't agree to it.

Quote

show me a citation of paint that can survive those incredible temperatures. By definition, paint is a thin coating. No paint material can absorb those levels of heat without being burned off. It's called thermodynamics.

we are not just talking about chipped paint of stealth plane (which is a big problem), but smudge on paint in engine nozzle.

Why paint a engine nozzle in first place?

Quote

5. The silver engine nozzles are clearly not AL-31F. The silver engines have F-35 type stealthy serrated edges/teeth. The AL-31F engines have smooth edges.

In the closeup picture I don't see any serrated edges in the picture!! Or did we missed anything?

Here is the side by side comparison for you -

[Martian]

China's WS-15 turbofan engine is nearing completion


There are little teeth on the engine nozzles if you look carefully. Also, there are saw-toothed edges at the engine/fuselage interface.

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China's WS-15 turbofan engine is either ready or almost ready. The discussion of domestic or foreign engines on the J-20 is moot. It is well known that China will mass produce the WS-15 supercruise engine for the J-20 production jets.

Reference: http://www.asian-def...jet-engine.html

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http://en.wikipedia..../Shenyang_WS-15

"The People's Republic of China began development of the WS-15 in the 1990s. The engine was reported by Russian sources as the "18 ton" thrust project to power future fifth generation fighters.^[1]
...
First run 2006"

(See primary source at: http://www.strategyc...pub_detail.asp)

[Siddharth]

Looks can be deceptive my friend. Here is another close shot for you.

In this closeup, even the saw tooth at engine/fuselage interface seems to be painted!!

[Martian]

Why don't you create a thread on J-20 and post what you like in it? I created this thread to discuss the various stealth aspects of the J-20. If you want to keep making unsubstantiated claims based on rumors, create your own thread and post whatever you like.

In the last three posts, I have given you at least five different reasons why you're probably wrong. Also, I explained the issue is moot. Go make your own thread and wallow in there.

How many times do I have to discuss the multi-decade lineage of China's turbofan engines with silver nozzles? If my analysis and mainstream articles do not convince you, nothing will.

I have provided numerous citations. You have provided none.

There is nothing new for me to say. The weight of the evidence says you're wrong, but you're just going to keep raising the same point over and over again. That is not productive. You've made your claim and I've replied. We cannot go any further until official data are released by the Chinese government.

If you like, I'll give you this thread and I'll start a new one on the J-20 Mighty Dragon.

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One final technical point: Your close-up photo of the J-20 engines prove nothing. I have no idea whether they're authentic or not. Unless a photograph of the J-20 has been taken from multiple angles, we can have little confidence in its authenticity.

I have no idea when or where your close-up photo of the J-20 was supposedly taken. Do you have the name of the photographer and the date? As far as I know, your supposedly close-up photo is a photoshop. Do you have other photographs from slightly different angles to increase our confidence level?

Your bottom photo is blurry and consistent with an enhanced photo from a long distance. Why is your top close-up photo not blurry?

Until you can provide convincing proof, I certainly will not waste my time with wild goose chases.

[Siddharth]

Hey.. no need to get super offended. You can keep this whole forum for all I care.

In all your posts you have just tried to divert discussion from my original question and stating that my posts are "rabid anti-Chinese conspiracy theory"?

I am just posting pictures from Chinese sources.

You say something but pictures say otherwise, what can I do?

Quote

We cannot go any further until official data are released by the Chinese government.

Well I agree to this part, which I stated in my earlier posts as well.

[Martian]

Not just you. Gnak has been doing the same thing. It's annoying. These issues (e.g. chipped paint and foreign/domestic engine debate) are very old.

Also, I've made the point that the debate is pointless. The WS-10A currently equips new J-10, J-11, and J-15 fighters.

The WS-15 will equip the J-20 fighters. Who cares about an interim engine? It will be replaced by the WS-15 in the production J-20 models.

Look at post #41 and #42. Post #41 shows the latest J-20 numbered "2002." Post #42 discusses the lack of flat 2D nozzles and the wait for a WS-15 supercruise engine.

The general rule is to keep moving forward and post new insights. Constantly rehashing old issues will be endless and disinteresting.

[Siddharth]

Quote

The WS-15 will equip the J-20 fighters. Who cares about an interim engine? It will be replaced by the WS-15 in the production J-20 models.

Now we are on the same page.

I totally admire what Chinese have done with this plane, but all information on web (regarding J-20) is a bit puffed up.

P.S. Discussion forums are two-way highway. People will question your assessment if they have no official data supporting it.

Thread is all yours

[Martian]

I'm just saying raise new issues. Not the same old ones. Also, when a topic cannot be explored any further, it makes sense to end the discussion.

Like I said, the Russian media would be crowing about AL-31F engines on both J-20s if it were true.

In conclusion, everyone knows the WS-15 will equip the J-20. Since we already know the outcome, why the big fuss over an inferior interim non-supercruise engine?

[Archangelesk99]

ha ha ha this whole argument is stupid.  Does anyone truly believe that china is not going to have the best stealth engines and all that in a few years' time?????

Come on everyone, be realistic!!!!!!  China is already thinking of sixth generational concepts and stuff, so ws-15 engine coming out and chipping paint (most likely because of the heat from the jet engines) is not going to matter for long and will be fixed in the next year or so........china is only 10 years behind usa and in another 10 will be RIGHT THERE on usa's heels, and even exceed usa in many things like infrastructure (I think she has already surpassed usa in that actually), GPS, renewable energy, sea exploration, internet, supercomputers, UAVs, etc!!!!!

I guarantee it!!!!  

PS. How do I know this????  Because I remember all the chinese guys who were from china who were studying their masters or phd here in america were about 10 TIMES more knowledgable than the american students ha ha ha ha!!  I USED TO TALK TO MANY OF THEM AND KNOW FOR A FACT THAT THE CHINESE AND INDIAN GUYS WHO COME TO USA TO DO THEIR MASTERS AND PHD, COME TO USA BECAUSE THEY CAN'T GET ADMISSION BACK HOME, BECAUSE COMPETITION IS SO INTENSE THERE.  And if these are the "not smart enough" guys who come here, can you imagine the level of study in china and what their smart guys in china's defence industry and other industries will come up with as china burgeons into a superpower???? This isn't very complicated, use common sense!!

[gnak]

Martian, on 04 April 2012 - 10:05 PM, said:

Not just you. Gnak has been doing the same thing. It's annoying. These issues (e.g. chipped paint and foreign/domestic engine debate) are very old.

Also, I've made the point that the debate is pointless. The WS-10A currently equips new J-10, J-11, and J-15 fighters.

The WS-15 will equip the J-20 fighters. Who cares about an interim engine? It will be replaced by the WS-15 in the production J-20 models.

Look at post #41 and #42. Post #41 shows the latest J-20 numbered "2002." Post #42 discusses the lack of flat 2D nozzles and the wait for a WS-15 supercruise engine.

The general rule is to keep moving forward and post new insights. Constantly rehashing old issues will be endless and disinteresting.

man u need to get ur head out of fantasy world

only reason i post here.... cus u said the j-20 uses ws-10 engines

but the nozzles on the j-20 verses j-10b or j-11b look nothing alike in shape, apart from colour

Siddharth said:

In this closeup, even the saw tooth at engine/fuselage interface seems to be painted!!

take a look the following image



not saying nothing im reserving my opinion let the viewers decide

[marchpole]

Fools stay fools。

[macau boy]

2001, 2002, 200X,... J-10B, J-10BS, J-11B, J-11BS, J-11BH, J-15, J-16, J-XX,... are marching off the production lines with our own indigenously designed and built turbofans in their bellies.
Hats off and deep bows to Mr. Shi Changxu, Father of China's high temperature alloy and high temperature new materials.
Every time our new plane takes off, the venerable Mr. Shi smiles.

[Martian]

Authoritative People’s Daily Online: “two [J-20] prototypes have been developed, with one employing a Russian engine and the other a Chinese one...."

Direct quote from China's official government newspaper People's Daily Online: "Analysts said two prototypes have been developed, with one employing a Russian engine and the other a Chinese one. It wasn't clear which prototype flew yesterday."

Reference: http://english.peopl...76/7257512.html

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Majority opinion concludes the WS-10 variant is the silver engine on J-20 Mighty Dragon (see citation below).

http://www.andreweri...c-implications/

"Engines

Engines are critical for any aircraft. This is one type of system that either works well or does not, with little potential for significant incremental adjustment. Some Russian sources quoted in a recent Sina.com article claim that the J-20 is using AL-41 engines, but most Chinese, Russian, and English-language sources and photo imagery suggest the J-20 prototypes are likely using a version of the WS-10 (already used in the J-11B, according to China Air and Naval Power) and the Russian AL-31 engines (Exhibit 5). According to Shanghai Daily/People’s Daily Online, “two [J-20] prototypes have been developed, with one employing a Russian engine and the other a Chinese one. It wasn’t clear which prototype flew” on 11 January."

[gnak]

wen the second prototype flys and clear pictures emerge

theres a very good chance the second prototype 2002 will have genuine chinese engines

pictures of prototype "2002" only emerged last month

theres only ever been one "flying" j-20 until recently, unless someone can show me a j-20 with penal number 2000 in the air

changing the engines for any plane usually requires a lot of time and major rework of the planes interior fuselage

however its been over 1 yr since j-20 flew now a real second prototype has emerged 2002 i can already see small difference





notice they moved the antenna to the center on the nose, and some flap at the rear of the cockpit

[marchpole]

2002

[Martian]

F-22 can detect J-20 at 22 km (WVR) from front or side perspective or at 59 km (BVR) from rear perspective

An important question is: "What is the detection range of a J-20 Mighty Dragon by a F-22 Raptor?"

We need to derive the approximate equation for radar detection.

We have three data points from U.S. AWACS that describe the relationship between detection range and RCS (radar cross section).

Reference from page 221: http://www.au.af.mil...torm/kiziah.pdf

"A typical cruise missile with UAV-like characteristics has an RCS in the range of 1 m2; the U.S.'s Tomahawk air-launched cruise missile (ALCM), designed in the 1970s utilizing the fairly simple low-observable technologies then available, has an RCS of less than 0.05 m2. The U.S. AWACS radar system was designed to detect aircraft with an RCS of 7 m2 at a range of at least 370 km. Using the physics of radar detection, which dictates that detection range varies with the object's RCS raised to the one-fourth power, the AWACS radar could detect the typical, non-stealthy cruise missile at a range of at least 227 km, and the stealthy cruise missile would approach air defenses to within a range of 108 km before being detected. Traveling at a speed of 805 kph (500 mph), air defenses would have only 8 minutes to engage and destroy the stealthy missile and 17 minutes for the non-stealthy missile."

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Relationship: DR = k * (RCS)^(1/4)

DR => detection range of radar
RCS => radar cross section of object
k = proportionality constant

The three data points from US AWACS can be used to determine the value of the proportionality constant "k."

DR1 = k * (RCS1)^(1/4)
370 km = k (7 m2)^(1/4)
370 km = k (1.627) [Note: I've omitted unit of square root m for RCS1 for readability.]
k = 370 km / 1.627 = 227 km / (square root meter)

DR2 = k * (RCS2)^(1/4)
227 km = k (1 m2)^(1/4)
227 km = k (1) [Note: I've omitted unit of square root m for RCS2 for readability.]
k = 227 km / 1 = 227 km / (square root meter)

DR3 = k * (RCS3)^(1/4)
108 km = k (0.05 m2)^(1/4)
108 km = k (0.473) [Note: I've omitted unit of square root m for RCS3 for readability.]
k = 108 km / 0.473 = 228 km / (square root meter)

We have a lot of confidence in our derived equation for the relationship between detection range and RCS because the proportionality constant k is the same for all three data points as we expected.

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F-22 detection range data point to verify constant k.

http://en.wikipedia....#Specifications

"Radar: 125–150 miles (200–240 km) against 1 m2 (11 sq ft) targets (estimated range)[142]"

(See primary source from AviationWeek in the footnote. Also, I used an average of 220 km detection range for calculations.)

DR4 = k * (RCS4)^(1/4)
220 km = k (1 m2)^(1/4)
220 km = k (1) [Note: I've omitted unit of square root m for RCS1 for readability.]
k = 220 km / 0.473 = 220 km / (square root meter)

So far, so good. The proportionality constant k from the F-22 datum has remained the same with less than 4% deviation from the US AWACS data.

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F-22 detection range of J-20 Mighty Dragon from frontal or side aspect.

Australia Air Power has informed us that the J-20 can match the F-22 in frontal or side aspect stealth. We will use the approximate RCS of 0.0001 m2 for the J-20 frontal and side aspect radar return.

DR5 = k * (RCS5)^(1/4)
DR5 = (220 km/sqr rt meter) * (0.0001 m2)^(1/4)
DR5 = (220 km/sqr rt meter) * (0.1 sqr rt meter)
DR5 = 22 km (or 13 miles)

Conclusion Part One:

A F-22 can detect a J-20 Mighty Dragon from a frontal or side perspective at 22 km (or 13 miles). This is WVR (within visual range) dogfight combat.

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F-22 detection range of J-20 Mighty Dragon from rear aspect.

Australia Air Power has informed us that the J-20 rear LOAN (low observable asymmetric nozzles) nozzles are comparable to the F-35 in stealth of approximately 0.005 m2 RCS.

DR6 = k * (RCS6)^(1/4)
DR6 = (220 km/sqr rt meter) * (0.005 m2)^(1/4)
DR6 = (220 km/sqr rt meter) * (0.266 sqr rt meter)
DR6 = 59 km (or 35 miles)

Conclusion Part Two:

A F-22 can use its radar to detect a J-20 Mighty Dragon from a rear perspective at 59 km (or 35 miles). This is BVR (beyond visual range) combat. A J-20 Mighty Dragon had better not permit a F-22 to fly behind it or the fight is over.

Alternatively, China needs to eventually install flat 2-D nozzles on the J-20 production version.

[Note: The proportionality constant k that happens to be the same for an US AWACS and the F-22 may be a coincidence. However, it doesn't matter. It is only of theoretical and not practical interest. This is a tangential issue that is not worth investigating without a lot of new firm data.

One possibility of reconciling the result is to assume the F-22 is using a focused-beam narrow search and the AWACS is using a wide-beam general search. This may result in the same radar intensity that appears to be independent of radar power output.

Anyway, the important insight is we now know the approximate detection range of the J-20 by either a F-22 or US AWACS. This conclusion is based on the calculation from an equation derived from empirical data.]

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General equation for power received from a radar return


General equation for power received from a radar return (Source: http://en.wikipedia....tion#Definition)

The general equation for the power received from a radar return is as we expected. We learned in high school physics that light intensity varies with the inverse square of the distance. This is obvious because the same power is distributed over the surface area of a larger sphere as we increase the distance.

Therefore, it is obvious the light intensity of the reflected radar wave is the product of two inverse squares, which varies with the inverse of the fourth power of distance (as reflected in the general equation shown above).

However, the general equation for power received from a radar return has limited utility. We do not know the values for some of the parameters in the equation (e.g. "gain of the radar transmit antenna" and "effective area of the radar receiving antenna").

[Martian]

This Russian radar blocker (twisted vanes) idea probably won't work



I am analyzing this Russian radar blocker concept of twisted vanes, because (two years ago) AviationWeek wrote an article about it. The Russians want to install this heavy mechanical device in front of the engine to deflect incoming radar waves.

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1. From a practical standpoint, this Russian radar blocker idea is terrible. Look at the rear of the device. There is a servomechanism twisting the vanes. It adds a lot of weight to the plane. This would affect the performance of the aircraft (e.g. range and maneuverability). Also, it will increase the maintenance hours between flights.

2. Look at the number of edges on those vanes. The radar return from edge diffraction will increase significantly. (See http://www.microwave...rbingradar2.cfm)

3. The theoretical concept may make sense, but it will never happen in real life. They want to apply a RAM coating to a vane and twist it to avoid radar detection. However, when you twist a formerly flat piece of material, the surface coating experiences tremendous stress and cracks will appear in the surface coating.

This concept is easily understood by applying wax material on top of a sheet of plastic. When you twist the hardened wax and plastic sheet to the degree shown in the video above, the wax (and possibly the plastic sheet) will show cracks.

The RAM material will not function properly if cracks develop on its surface. X-band radar has a wavelength of 2.4 cm. A centimeter-scale crack on the RAM material will render it unstealthy.

4. The T-50/Pak Fa is designed to supercruise. The air flowing by the vanes (even in a straightened configuration) will be supersonic. Once cracks develop in the RAM material, the supersonic air will carry little chunks into the engine. Can the engine handle little chunks of RAM material striking the engine blades at supersonic speed? Also, will the RAM material melt and accumulate inside the engine and impair its operation? These are important questions.

5. I don't know if the vanes will work at all. In its operational mode, the vanes are twisted. This means the X-band radar is reflecting off a curved surface. In contrast, X-band radar reflects off a flat smooth surface inside a S-duct on the J-20 and F-22.

On the J-20 and F-22, the engineers can be confident that the airducts are machined to the needed tolerances for a surface that is apparently smooth to X-band radar. However, for the T-50/Pak-Fa, how can the engineers ensure that the surface of every single vane is smooth after repeated twists?

We know that radar reflects very well off round objects. It may be reasonable to consider a twisted vane as the partial surface of a rounded object. Therefore, there could be a decent specular radar return from the surface of a twisted vane.

6. The flat frontal rim of the cylindrical housing (for the vanes) is not stealthy and will reflect radar.

7. The vanes themselves have a thickness. Where will the Russians find a material that has negligible thickness and can withstand repeated twists without ANY distortion. Also, the Russians have to find a RAM coating with the same dual properties of negligible thickness and no distortion after repeated twists. I think you also need a bonding agent with the same properties that is COMPLETELY resistant to distortion and has negligible thickness.

I don't think such materials currently exist. If the vanes have a horizontal thickness on a centimeter scale then they will reflect radar from their frontal face.

The vertical dimension of the frontal face of the vanes will be on the order of a meter scale and there will definitely be a X-band radar return along the length of the frontal face of the vanes.

8. In conclusion, I believe the Russians will realize it's a lot easier to redesign the T-50/Pak Fa with a S-duct than to build a radar blocker. Over two years have passed and we have not seen a Russian radar blocker installed on any of the three T-50/Pak Fa prototypes. I think the Russian radar blocker idea will be confined only to theoretical discussions.

[macau boy]

Martian, on 12 April 2012 - 08:21 AM, said:

I believe the Russians will realize it's a lot easier to redesign the T-50/Pak Fa with a S-duct than to build a radar blocker. Over two years have passed and we have not seen a Russian radar blocker installed on any of the three T-50/Pak Fa prototypes.

Given the size of the plane, there should be enough room inside T-50 for the reconfiguration of the air intake ducts along with other necessary equipment relocations and structural changes, but it won't be a simple or easy job. In addition to the rearrangement of duct systems, the redesign would no doubt involve work from the air intakes to the engine bays. Besides money issues (not sure any potential customer would be willing to foot the bills), the biggest concern is time and time is the one thing that Russia doesn't have. They need to sell the plane as fast as possible in order to survive in this brutal business environment.
It reminds me of the TVC farce on the MKI from the late '90s. No one else, including Russia, use that crap today.

[marshall]

Martian, on 12 April 2012 - 08:21 AM, said:

This Russian radar blocker (twisted vanes) idea probably won't work
...
...
This concept is easily understood by applying wax material on top of a sheet of plastic. When you twist the hardened wax and plastic sheet to the degree shown in the video above, the wax (and possibly the plastic sheet) will show cracks.

I don't think the idea is to "twist" the radar blocker. I believe the Youtube video was simply to illustrate how the vanes would block radar. I don't know how a moving twisting vane would work anyways. So, there would be no cracking from any twisting. Edge diffracted radar would be minor compared to no radar blocker at all and most of the specular reflections would deflect back into the inlet to be repeatedly absorbed off the RAM coated walls. Agreed that this would add more weight than simply designing this with an S-shaped inlet. However, that would change the entire internal weapons layout and create more drag.

[Martian]

My reply to the post above consists of three points.

1. The YouTube video clearly shows twisting of the vanes as the servomechanism in the rear changes the vane position to block direct-line-of-sight to the engine fan blades behind it.

Instead of the elegant rotary servomechanism shown in the video, you are arguing for a more complex mechanical system to create a different configuration for the vanes without twisting. Your proposal is likely to fail due to additional weight and mechanical complexity problems.

2. The vanes HAVE TO BE twisted to provide a smooth flow of air. You can't use flat-paneled vanes angled at 30 degrees (e.g. the video shows six vanes over an 180 degree arc), because it will disrupt the airflow by creating vortices at supersonic speed during supercruise.

3. The specular radar reflections would strike an adjacent vane and some of the radar energy would be re-transmitted through the edges of the vanes through "creeping waves" or edge diffraction (see http://www.microwave...rbingradar2.cfm). These vanes are not stealthy.

[marshall]

Martian, on 14 April 2012 - 06:16 AM, said:

1. The YouTube video clearly shows twisting of the vanes as the servomechanism in the rear changes the vane position to block direct-line-of-sight to the engine fan blades behind it. Instead of the elegant rotary servomechanism shown in the video, you are arguing for a more complex mechanical system to create a different configuration for the vanes without twisting. Your proposal is likely to fail due to additional weight and mechanical complexity problems.

That's not what I'm saying. I believe many are misinterpreting the Youtube video by taking the twisting servomechanism literally as the way it would operate in practice while I believe it was purely for illustration purposes.  The only reason for a mechanical regime would be to allow unimpeded air flow for maximum speed when supercruising, but this would expose the engine blades. The rationale doesn't make much sense given the speed wouldn't be affected that badly which is why the mechanical illustration is probably there to simply allow the viewer to better understand conceptually what was trying to be conveyed. I believe the vanes are permanently fixed at an angle because that is their functional design.

Martian, on 14 April 2012 - 06:16 AM, said:

2. The vanes HAVE TO BE twisted to provide a smooth flow of air. You can't use flat-paneled vanes angled at 30 degrees (e.g. the video shows six vanes over an 180 degree arc), because it will disrupt the airflow by creating vortices at supersonic speed during supercruise.

I never argued the vanes have to be flat. I do agree that this would create a vortex that, absent the counter vortex of the other engine radar blocker, would create "pull" to one side of the aircraft. It would make more sense for each individual vane to be S-shaped to eliminate the sort of forces you're talking about. In effect, each individual air path of each respective vane would be like a small S-shaped inlet. I think there was another such radar blocker design that did exactly that. Mind you that the edges and center could be easily tweaked with sharper angles and nose cone.

Martian, on 14 April 2012 - 06:16 AM, said:

3. The specular radar reflections would strike an adjacent vane and some of the radar energy would be re-transmitted through the edges of the vanes through "creeping waves" or edge diffraction (see http://www.microwave...rbingradar2.cfm). These vanes are not stealthy.

True, but these creeping waves would be a very small fraction of what otherwise would be a monumental radar return if there were no radar blocker at all. What you're describing is also present with a traditional S-shaped inlet that we find on the F-22A and J-20.  I know there are more surfaces and thus more of a return but absent a traditional S-shaped inlet, there is no other viable solution.

[Martian]

Russian radar blocker idea fails on aerodynamic and stealth considerations

I've already analyzed the other Russian radar blocker idea last year and concluded it won't work. Below is a series of posts from my previous analysis. Additionally, I want to mention that a micro-S duct design will never work aerodynamically for two reasons.

1. The large hub and spokes of the micro-S duct design radar blocker obscure too much surface area and significantly impair the amount of air flowing into the engines.

2. The small S-duct pipes are like little straws. The engine has to draw air through a multitude of little S-shaped straws. There is a boundary drag problem. The air will rub against the massive collective surface area of the S-duct pipes and slow down.

The small portion of the air right in the middle of the S-duct pipes will be almost unimpeded. There will be a serious airflow problem because the air is flowing at different speeds. When the plane travels at supersonic speed, the air will bounce off the curves in the tiny S-ducts and create vortices.

The implementation of a mini-S duct design will be at the cost of relinquishing supercruise ability.


Even without an in-depth physics analysis, it is obvious the Russian radar blocker is not stealthy to X-band radar with 2.4 cm wavelength. Remember, this radar blocker device has to be robust to withstand supersonic speed during supercruise. The structural hub and spokes will always be detectable to X-band radar.

If you make the spokes thinner then you weaken them structurally and you'll need more spokes (which makes it more easily detectable to X-band radar). If you use fewer and stronger spokes then you'll have more easily detectable thick spokes.  Either way, you're not stealthy.

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Objections to the mythical Russian engine blocker

1. Lack of a scientific basis (i.e. not a single peer-reviewed scientific paper) for outrageous claim of a mythical Russian engine radar blocker.

2. There are constant press releases from Sukhoi. Show me a Sukhoi press release on the mythical Russian engine blocker. The Chinese are tight-lipped and we can't get any information from them. The Russians have the opposite problem. They are always making boasts, such as "our plane is just as good as the F-22. My reaction: "sure it is. Did you spend $63 billion on research like the F-22?"

3. Why is there no mention of a Russian engine radar blocker in any of the mainstream Western articles on the T-50? For example, GlobalSecurity wrote a glowing article on the T-50 and ignored all of its major shortcomings. Why did they not mention this incredible 6-inch Russian engine radar blocker?

PAK FA / T-50 / Project 701

"The aircraft of the fifth generation is equipped with the fundamentally new complex of avionics, that integrates the function "electronic pilot", and by promising phased-array radar. This to a considerable degree reduces load on the pilot and makes it possible to be concentrated on the fulfillment of tactical missions. Onboard equipment of new aircraft permits implementation of the exchange of data in the regime of real time both with the ground-based systems for control and inside the air group. The application of composite materials and innovation technologies, the aerodynamic layout of aircraft, measure for reduction in distinctness of engine ensure the unprecedented low level of radar, optical and infrared distinctness. This makes it possible to considerably increase combat effectiveness in the work both along the air and ground targets, at any time twenty-four hours, in the simple and adverse weather conditions."

4. How did the Russians manage to leapfrog the United States and China in stealth technology with the smallest research budget among the three countries? The Russians have a tiny economy of about $1.5 trillion, which is four times smaller than China and about ten times smaller than the U.S.

5. You claim there is a 6-inch Russian engine radar blocker. Are you aware that it practically defies the laws of physics to accomplish the task as you claim?

From high school or college physics, everyone knows about the double-slit experiment. When the gap between the metal grates are comparable to the size of the wavelength of the photons, the photons act like waves (and not like particles anymore) to create an interference pattern.

The wavelength of L-band radar ranges from 15 to 30 cm. Looking at the numerous micro-S ducts in your picture, they look to be at least 30 cm across. Upon impact with L-band radar, your micro-S duct system will create a massive interference pattern and reflect a huge amount of the incoming photonic radar energy. You are going to have a serious backscatter problem.

http://www.globalsec...-22-stealth.htm

"However, multiple-reflection cases have not yet been looked at, which change the situation considerably. It is fairly obvious that energy aimed into a long, narrow, closed cavity, which is a perfect reflector internally, will bounce back in the general direction of its source. Furthermore, the shape of the cavity downstream of the entrance clearly does not influence this conclusion.

However, the energy reflected from a straight duct will be reflected in one or two bounces, while that from a curved duct will require four or five bounces. It can be imagined that with a little skill, the number of bounces can be increased significantly without sacrificing aerodynamic performance. For example, a cavity might be designed with a high-cross-sectional aspect ratio to maximize the length-to-height ratio. If we can attenuate the signal to some extent with each bounce, then clearly there is a significant advantage to a multi-bounce design. The SR-71 inlet follows these design practices.
However, there is a little more to the story than just the so called ray tracing approach.

When energy strikes a plate that is smooth compared to wavelength, it does not reflect totally in the optical approximation sense, i.e., the energy is not confined to a reflected wave at a complementary angle to the incoming wave.

The radiated energy, in fact, takes a pattern like a typical reflected wave structure. The width of the main forward scattered spike is proportional to the ratio of the wavelength to the dimension of the reradiating surface, as are the magnitudes of the secondary and tertiary spikes. The classical optical approximation applies when this ratio approaches zero. Thus, the backscatter - the energy radiated directly back to the transmitter increases as the wavelength goes up, or the frequency decreases.

When designing a cavity for minimum return, it is important to balance the forward scatter associated with ray tracing with the backscatter from interactions with the first surfaces. Clearly, an accurate calculation of the total energy returned to the transmitter is very complicated, and generally has to be done on a supercomputer."

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Important points from the GlobalSecurity article above:

1. A micro-S duct does not maximize the length-to-height ratio. To the contrary, a micro-S duct minimizes the length-to-height ratio. It cannot attenuate an incoming radar wave.

2. The micro-S duct gap size is comparable to the wavelength of the L-band radar and most of the radar energy will be reflected in a huge backscatter signal.

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Mythical Russian radar blocker won't work

Quote

It's alright there's no need. You aren't going to convince me the PAK FA can not be fitted with an engine blocker. It's not super advanced technology, the F-18E/F uses it and we all know how long it has been around for.

As for six inches... Lol I never said the engine blocker was six inches, I was basing it off eyeballing this picture:


I actually think it's probably a good deal longer than six inches, considering the diameter needed to cover the entire front of the engine.

If you want to read more up on it the picture first posted came from here Sukhoi T-50 PAK FA first flight - pictures, videos and analysis and there's a good bit of discussion to go along with it.
I would go onto some of the other forums like key or secretprojects for testimonials from people there who probably know much more than me and you, but I can't really be bothered.

My discussion with Blitzo on the Russian radar blocker ended a while ago. I am not resurrecting the debate. However, while my mind is clear, I want to write down and share a few new observations.

1. Based on physics, the Russian radar blocker won't work. The specular reflection from the mostly perpendicular surfaces will be enormous and easily detectable.

2. The idea of using micro-ducts is patently silly. The principle of stealth behind the F-22, J-20, and F-35 is to use a large cavity (e.g. the long "S" air duct) to reflect an incoming radar wave multiple times towards the inside of the long S-duct. With each bounce inward, the RAM coating converts some of the radar energy into heat energy. The process is the same with the radar-wave bounce back out of the interior of the long S-duct.

With micro-ducts, it is impossible to have multiple bounces to attenuate an incoming radar wave. The cavity is too small.

3. A micro-duct design will create a broad and diffuse specular radar return. Based on physics, the cavity has to be large and smooth to reflect an incoming radar wave. With a micro-duct, the surface will not appear to be smooth, because it is curved on a small-scale (which is noticeable to the wavelength of S/C/L/X band radar).

4. Look at Blitzo's picture (see above). Do you see that giant round disk in the middle? There goes your stealth. Also, the large perpendicular metal spokes radiating from the giant round hub in the middle will also create a massive radar return.

In conclusion, due to physics problems, the Russian radar blocker won't work and it's a fantasy.

(Sorry Blitzo, but I believe I possess more analytical power on stealth than all of the forum members at KeyPublishing combined. They came up with a stupid claim and I'm here to debunk it.)

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Mythical Russian radar blocker's "broad and diffuse specular radar return"

I will explain point #3 in greater detail to make it easily understandable.

Imagine that photons (which include radar waves) are a group of ping pong balls. If you throw a group of ping pong balls against the wall in a long hallway, they'll just bounce down the hallway/cavity.

Now, try throwing a group of ping pong balls into a Mythical Russian radar blocker with micro-ducts, which are roughly the size of the ping pong balls. Most of the ping pong balls will bounce back out. There is your "broad and diffuse specular radar return."

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Reason for analyzing Mythical Russian radar blocker


Purported Mythical Russian radar blocker (Source: Blitzo)

I want to make it clear that my analysis and debunking of the Mythical Russian radar blocker did not arise out of a desire to pick on the Russian T-50/Pak Fa.

Blitzo is a well-known member among defense forums. Blitzo stated that the entire Key Publishing forum membership had debated the Russian radar blocker issue and arrived at the collective judgment that it was an effective stealth device to block enemy radar.

I had no choice but to debunk the stupid conclusion of the entire Key Publishing forum community. In my opinion, their collective judgment on stealth design is not worth much and I had to analyze the Mythical Russian radar blocker in detail to set the record straight.

Give me a break. How hard is it to look at the picture and notice the giant non-stealthy metallic disc in the center of the drawing? The entire Key Publishing forum community is blind as a bat.

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L-band radar wavelength is 24cm or almost one foot


L-band radar wavelength is almost 1 foot. (Note: 1 inch = 2.54 cm)


Purported Mythical Russian radar blocker (Source: Blitzo)

Those micro ducts are roughly the same size as, or smaller than, L-band radar wavelength. A microduct design will not work and it is clearly detectable with L-band and probably S-band radar. As I have already stated, the microducts will produce a "broad and diffuse specular [radar] reflection."

As you move from the outer rim and towards the hub, the spacing between spokes become smaller. As you near the central non-stealthy gigantic metallic hub, the smaller cavities mean those portions of the Mythical Russian radar blocker become detectable to smaller radar wavelengths, such as C-band and X-band.

[marshall]

Martian, on 15 April 2012 - 07:54 AM, said:

1. The large hub and spokes of the micro-S duct design radar blocker obscure too much surface area and significantly impair the amount of air flowing into the engines.

2. The small S-duct pipes are like little straws. The engine has to draw air through a multitude of little S-shaped straws. There is a boundary drag problem. The air will rub against the massive collective surface area of the S-duct pipes and slow down.
...
The implementation of a mini-S duct design will be at the cost of relinquishing supercruise ability.

I would agree if a MICRO s-duct were used of the kind pictured.  However, my original message was concerning how the Youtube video of the animated servo-mechanical radar blocker could work as a fixed s-duct style radar blocker.  I only posted the picture of the micro s-duct radar blocker to illustrate the idea of the s-shaped ducts in a multi-vane configuration.  The way I could see this working would be to use a long radar blocker of at least 3-4 feet with reduced number of individual vanes to maybe 5 or 6.  This would lessen the aerodynamic impact dramatically while blocking the exposed engine blades.

Martian, on 15 April 2012 - 07:54 AM, said:

4. How did the Russians manage to leapfrog the United States and China in stealth technology with the smallest research budget among the three countries? The Russians have a tiny economy of about $1.5 trillion, which is four times smaller than China and about ten times smaller than the U.S.

$1.5 trillion is not "tiny" and it's concentrated in a relatively small population with a very long and established aeronautics tradition who already had two 4+ generation (SU-47 & Mig 1.42) technology demonstrators.

Martian, on 15 April 2012 - 07:54 AM, said:

"...It is fairly obvious that energy aimed into a long, narrow, closed cavity, which is a perfect reflector internally, will bounce back in the general direction of its source. Furthermore, the shape of the cavity downstream of the entrance clearly does not influence this conclusion.

Only in some situations, but it would NOT be for an S-shaped duct designed for stealth because the curvature would reflect radar inwards, with each reflection gradually absorbed by the RAM on the inside walls. By the time any radar came back out, there would be nothing but the greatly reduced EM waves travelling off the surface.

Martian, on 15 April 2012 - 07:54 AM, said:

The radiated energy, in fact, takes a pattern like a typical reflected wave structure. The width of the main forward scattered spike is proportional to the ratio of the wavelength to the dimension of the reradiating surface, as are the magnitudes of the secondary and tertiary spikes. The classical optical approximation applies when this ratio approaches zero. Thus, the backscatter - the energy radiated directly back to the transmitter increases as the wavelength goes up, or the frequency decreases.

Like I said, it was for illustration purposes. I agree that a micro-duct would dramatically affect the top speed and that alone would rule it out.  But that is not what I was explaining.  A larger version of the "micro" S-duct with fewer vanes and stretched out to a couple of feet would be a viable tradeoff.

Martian, on 15 April 2012 - 07:54 AM, said:

1. Based on physics, the Russian radar blocker won't work. The specular reflection from the mostly perpendicular surfaces will be enormous and easily detectable.

As I said earlier, that can be largely mitigated with sharper edges and nose cone, best composed of RAM material.

Martian, on 15 April 2012 - 07:54 AM, said:

2. The idea of using micro-ducts is patently silly. The principle of stealth behind the F-22, J-20, and F-35 is to use a large cavity (e.g. the long "S" air duct) to reflect an incoming radar wave multiple times towards the inside of the long S-duct.

I never insinuated otherwise. Given the straight inlet design of the PAK FA, there is no other choice, unless you believe the claims that the Russians have a RAM coating that can be applied to the blades to fix the problem, which I do not. Any such coating would be a good 1 trick pony given the forces involved and very high likelihood that such coating would eventually start flaking off.  Good luck maintaining that sort of solution.  Having said that, a larger S-duct radar blocker with a couple of individual vanes is a perfectly reasonable alternative absent a total redesign of the PAK FA.  Yes, it would reduce the speed but it would still be able to supercruise, albeit slower, and wouldn't be the issue you're insinuating in the subsonic and transonic regimes.

[Martian]

Bottom line: Russian "twisted vanes" and "hub and spokes" radar blockers are not stealthy

I have no idea which radar blocker you're discussing. You keep mixing the discussion between the "twisted vanes" and the "hub and spokes."

The bottom line is both radar blockers are not stealthy. I don't care what imaginary super-thin and super-strong structural and RAM material that you fantasize can withstand supersonic speed. Those materials don't exist.

By the way, the "twisted vanes" video (in post #67) is extremely misleading. All of those vanes are being twisted around a pencil-thin central axis. That's virtually impossible. There is a tremendous amount of torque being exerted on the central axis when all of the vanes are being twisted by the servomotor in the rear.

The "twisted vanes" video is missing a large central hub to absorb the torque when the vanes are twisted. Without a strong and large central hub, all of the vanes will snap off when they are twisted.

The following facts are indisputable:

1. A radar blocker will impede airflow to the engine. The straight vanes were an attempt to keep the airflow unimpeded. However, whenever a radar blocker tries to block the engine fans from view, it will almost certainly prevent supersonic flight due to air vortices. You have a small curved cavity with flowing supersonic air. That's almost impossible. You try to suck air through a short curved straw at supersonic speed.

An engine operating at supersonic speed needs a minimum cubic feet per minute (CFM) airflow. I don't think it's attainable when there is a large convoluted device (aka Russian radar blocker) blocking and disrupting the airflow to the engine.

Let's discuss fluid mechanics for a moment. What happens when you stick an object into the middle of a flowing stream? It creates eddies and slows the water around the object from friction. Similarly, when you stick a Russian radar blocker in front of an engine intake, there will be a multitude of eddies and obstructed airflow from the hub and spokes/vanes. This is not a viable solution for a supercruising aircraft.

2. A radar blocker needs a hub. You need to have a large central hub for the spokes/vanes and a large cylindrical rim anchor at the edge for the spokes/vanes. A central hub makes sense, because it lessens the length of the spoke/vane and the stress placed on it.

The spoke/vane will have to be thick and strong. There will be severe pressure differences between the opposite sides of a spoke/vane. There are air turbulence pockets. Also, when the T-50/Pak Fa is trying to evade a missile at 9Gs, the banking maneuvers will create sudden pressure differences laterally.

3. The argument that the "giant hub and spokes" or the "cylindrical anchor and vanes" could be made paper-thin (below the 2.4 cm X-band wavelength) is plain stupid. To withstand the stresses of supersonic flight and radical evasion maneuvers of 9Gs, a radar blocker needs a strong structure with multiple layers of RAM. Multiple layers of RAM are necessary to absorb a wider range of frequencies and also for cancellation of radar waves that reflect off a deeper layer.

References:

http://www.globalsec...ft-material.htm

"One common technique to improve the broad band response of a specular RAM is to use multiple coatings separated by some kind of a band pass filter."

http://www.warfaresims.com/?p=755

"A former LockMart engineer who worked on the F-117, B-2 & F-22 programs is to file a lawsuit against the company for allegedly concealing deficiencies on the radar-absorbent material (RAM) coatings of the stealth fighter...."

http://www.airplaned...dar-stealth.htm

"It is the thickness of your airplane’s skin, and the relationship between the skin and the internal components, that will determine whether you’ll reflect radar in such a way that it will cancel itself off."

4. The total thickness of the underlying structure (e.g. central hub or cylindrical anchor), multiple layers of RAM material, and multiple layers of bonding material will easily exceed 2.4 cm in thickness. This means X-band radar can easily detect the supposed radar blocker.

This is the reason that you have never seen a prototype American or Russian radar blocker flight tested. No one is crazy enough to place a complex mechanical device in front of the engine intake. (Note: The grill on the F-117 Nighthawk is a simplistic mesh that is suitable only for subsonic aircraft and radar from thirty years ago. The extended partial S-duct on the F-18 E/F Super Hornet is also a simplistic extender without complex mechanical parts.)

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In conclusion, I become annoyed when people keep changing the subject (e.g. Is he arguing "twisted vanes," "hub and spokes," or some other theoretical b.s. radar blocker?) and their arguments. This is my last response to Marshall on this matter unless he can provide reputable citations for super-strong and super-thin structural and RAM materials on a millimeter scale (which I don't think exist) that can withstand supersonic speed.

Last year, I explained the Russian "hub and spokes" radar blocker would not work and it's a terrible idea. This year, I've explained the Russian "twisted vanes" radar blocker also would not work. If AviationWeek or some other mainstream publication is willing to publish an article on another hypothetical Russian radar blocker idea then I will examine it on its merits. Otherwise, I'm finished wasting my time on b.s. Russian radar blockers and Marshall's arguments of imaginary materials to circumvent the physics problems.

[Martian]

F-22 is irrelevant in a Sino-American conflict

The F-22 Raptor is a marvelous piece of engineering. On a scale of 1 to 100 for stealth, I would rate it a "99" (e.g. lose one point for RAM-coated mechanical adjuster for airduct flow). For the J-20 Mighty Dragon, I would rate it a "97" (e.g. lose one point each for canard, ventral fin, and slight bump along exterior airduct; I'm assuming they'll eventually install flat engine nozzles.).

The important insight is that F-22s will never be a factor in a Sino-American conflict. The F-22 has a short combat radius of only 479 miles or 759 km (see http://en.wikipedia....#Specifications).

Fuel drop tanks can't be used in a Sino-American scenario, because the F-22 will become vulnerable and easily detected by Chinese KJ-2000 AWACS. You can try to use somewhat stealthy drop tanks, but it won't matter as I will shortly explain.

A fighter with a short combat radius is dependent on an airbase close to the Chinese coastline. Without a base to resupply fuel or ordnance, a fighter is useless. This is precisely the problem confronting the United States in a conflict scenario with China. Looking at the map below, you will see that the U.S. only has a few bases in Japan and South Korea. These U.S. bases can be easily wiped out by a coordinated strike from Chinese ballistic and cruise missiles.

To avoid this problem, U.S. aircraft will have to be moved to Guam. Unfortunately, Chinese missiles can also destroy Guam and any US fighter aircraft based on Guam will be too far away to engage in combat near the Chinese coastline. Therefore, the only conclusion is that the F-22 Raptor is not a factor in a potential Sino-American conflict.


The US only has a few bases in Japan and South Korea. These bases are extremely vulnerable to coordinated Chinese ballistic and cruise missile strikes.

US missile defense is useless when the other side is launching hundreds or thousands of missiles at you. Furthermore, no one has claimed 100% effectiveness for US missile defense under battlefield conditions. US missile defense is further complicated by the prospects of stealthy Chinese cruise missiles (e.g. HN-2000) and ballistic MARV (maneuverable re-entry vehicle) warheads.

The largest U.S. airbase in Asia is Kadena Air Base in Japan.

http://www.kadena.af.mil/index.asp

"Kadena Air Base is the hub of airpower in the Pacific, and home to the Air Force's largest combat wing -- the 18th Wing -- and a variety of associate units. Together they form "Team Kadena" -- a world-class combat team ready to fight and win from the Keystone of the Pacific.

Nearly 18,000 Americans and more than 4,000 Japanese employees and contractors make up Team Kadena. The base's estimated economic impact upon Okinawa's economy is more than $700 million annually."


U.S. Kadena Air Base, "the hub of airpower in the Pacific," can be destroyed by 34 Chinese missiles with submunition warhead. China has approximately 1,800 short-range ballistic missiles (SRBMs) aimed at Taiwan alone.

http://www.defensene...es-Taiwan-2012-

"China 'To Target 1,800 Missiles at Taiwan In 2012'
May. 20, 2011 - 06:00AM   |  By AGENCE FRANCE-PRESSE

TAIPEI - The number of Chinese missiles targeted at Taiwan is likely to reach 1,800 next year, despite improving ties between the former arch-rivals, Taiwanese media said May 20.

The Liberty Times newspaper cited a military intelligence report as providing the forecast.

Taiwanese experts have estimated that China currently has more than 1,600 missiles aimed at the island, mostly deployed in Fujian and Jiangxi provinces in the mainland's southeast."

[Note: Thank you to Mil-Avia for the pictures.]

[marchpole]

Martian, on 22 April 2012 - 03:21 PM, said:

F-22 is irrelevant in a Sino-American conflict

The F-22 Raptor is a marvelous piece of engineering. On a scale of 1 to 100 for stealth, I would rate it a "99" (e.g. lose one point for RAM-coated mechanical adjuster for airduct flow). For the J-20 Mighty Dragon, I would rate it a "97" (e.g. lose one point each for canard, ventral fin, and slight bump along exterior airduct; I'm assuming they'll eventually install flat engine nozzles.).

The important insight is that F-22s will never be a factor in a Sino-American conflict. The F-22 has a short combat radius of only 479 miles or 759 km (see http://en.wikipedia....#Specifications).

Fuel drop tanks can't be used in a Sino-American scenario, because the F-22 will become vulnerable and easily detected by Chinese KJ-2000 AWACS. You can try to use somewhat stealthy drop tanks, but it won't matter as I will shortly explain.

A fighter with a short combat radius is dependent on an airbase close to the Chinese coastline. Without a base to resupply fuel or ordnance, a fighter is useless. This is precisely the problem confronting the United States in a conflict scenario with China. Looking at the map below, you will see that the U.S. only has a few bases in Japan and South Korea. These U.S. bases can be easily wiped out by a coordinated strike from Chinese ballistic and cruise missiles.

To avoid this problem, U.S. aircraft will have to be moved to Guam. Unfortunately, Chinese missiles can also destroy Guam and any US fighter aircraft based on Guam will be too far away to engage in combat near the Chinese coastline. Therefore, the only conclusion is that the F-22 Raptor is not a factor in a potential Sino-American conflict.


The US only has a few bases in Japan and South Korea. These bases are extremely vulnerable to coordinated Chinese ballistic and cruise missile strikes.

US missile defense is useless when the other side is launching hundreds or thousands of missiles at you. Furthermore, no one has claimed 100% effectiveness for US missile defense under battlefield conditions. US missile defense is further complicated by the prospects of stealthy Chinese cruise missiles (e.g. HN-2000) and ballistic MARV (maneuverable re-entry vehicle) warheads.

The largest U.S. airbase in Asia is Kadena Air Base in Japan.

http://www.kadena.af.mil/index.asp

"Kadena Air Base is the hub of airpower in the Pacific, and home to the Air Force's largest combat wing -- the 18th Wing -- and a variety of associate units. Together they form "Team Kadena" -- a world-class combat team ready to fight and win from the Keystone of the Pacific.

Nearly 18,000 Americans and more than 4,000 Japanese employees and contractors make up Team Kadena. The base's estimated economic impact upon Okinawa's economy is more than $700 million annually."


U.S. Kadena Air Base, "the hub of airpower in the Pacific," can be destroyed by 34 Chinese missiles with submunition warhead. China has approximately 1,800 short-range ballistic missiles (SRBMs) aimed at Taiwan alone.

http://www.defensene...es-Taiwan-2012-

"China 'To Target 1,800 Missiles at Taiwan In 2012'
May. 20, 2011 - 06:00AM   |  By AGENCE FRANCE-PRESSE

TAIPEI - The number of Chinese missiles targeted at Taiwan is likely to reach 1,800 next year, despite improving ties between the former arch-rivals, Taiwanese media said May 20.

The Liberty Times newspaper cited a military intelligence report as providing the forecast.

Taiwanese experts have estimated that China currently has more than 1,600 missiles aimed at the island, mostly deployed in Fujian and Jiangxi provinces in the mainland's southeast."

[Note: Thank you to Mil-Avia for the pictures.]

Make sure these missiles are based close to Taiwan but are targeted at Japanese and US forces。

[Martian]

Latest J-20 Mighty Dragon pictures during ground tests











[Note: Thank you to Greyboy2 for the pictures.]

[Martian]

J-20 Mighty Dragon flight on April 27, 2012


J-20 with extended landing gear


J-20 retracts landing gear wheels.


J-20 closes wheel bay doors.


J-20 saw-toothed doors close flush against the fuselage.


J-20 flaunts its cleanly designed stealthy underside.


J-20 is silhouetted against colorful buildings in the background.


Engineers and technicians make constant adjustments to the J-20 during tests.


Cool picture of flame shooting out of one J-20 engine.

[Note: Thank you to Greyboy2 for the pictures.]

[Martian]

Clearest picture of J-20 Mighty Dragon cockpit from recent flight test


You won't find a clearer picture of the J-20 Mighty Dragon cockpit.


A view of the J-20 cockpit from the port side.


A wider view of the J-20 cockpit on April 27, 2012.

[Note: Thank you to Greyboy2 for the pictures.]

[macau boy]

That flame shooting pic is a never before seen extremely rare photo. Thx!