J-20... The New Generation Fighter II

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delft

Brigadier
Re: Final estimate for J-20 canards' radar return energy is 3.276x10^-19

Martian said:
Since you're a new member and appear totally clueless, I would appreciate it if you clicked on the link that I provided before giving me an offhand and flippant reply. The Answers.com link is to an article by McGraw-Hill encyclopedia. McGraw-Hill is one of the largest publishers in the United States and they were the owners of Businessweek, until its recent sale to Bloomberg. My citation on RAM effectiveness is McGraw-Hill Science and Technology Encyclopedia, not Answers.com.



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Your reference to the McGraw-Hill Encyclopedia gives 50 dB for the pyramid field type of absorber, more than 25 dB for a ram coating. I'm no expert in this field, but I would then expect 99.9 % absorption rather than 99.999 %.
 
C

Centrist

Junior Member
Re: Final estimate for J-20 canards' radar return energy is 3.276x10^-19

Martian said:
My analytic process, citations of reputable open-source material, and calculations have been thoroughly detailed. If you are unhappy with the result, feel free to criticize the step-by-step analysis on its merits.

Your attempt to deflect the discussion from my painstaking analysis is irrelevant.

When I began my calculation of the radar energy return on the J-20's canards, I had no idea what the result would be. If the conclusion was a significant radar signature, I would have docked points from the J-20's stealthiness. However, the conclusion showed that the effect of the J-20's canards requires 19 decimal places to see an effect.

To answer your question, from my meticulous calculations, it should be obvious to you that I have an engineering background. I have a bachelor's degree in electrical engineering and I'm a member of Eta Kappa Nu (e.g. American electrical engineering honor society).
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His question was a reasonable one, how are we supposed to know what your background is?
 
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latenlazy

Brigadier
Re: Final estimate for J-20 canards' radar return energy is 3.276x10^-19

Martian said:
My analytic process, citations of reputable open-source material, and calculations have been thoroughly detailed. If you are unhappy with the result, feel free to criticize the step-by-step analysis on its merits.

Your attempt to deflect the discussion from my painstaking analysis is irrelevant.

When I began my calculation of the radar energy return on the J-20's canards, I had no idea what the result would be. If the conclusion was a significant radar signature, I would have docked points from the J-20's stealthiness. However, the conclusion showed that the effect of the J-20's canards requires 19 decimal places to see an effect.

To answer your question, from my meticulous calculations, it should be obvious to you that I have an engineering background. I have a bachelor's degree in electrical engineering and I'm a member of Eta Kappa Nu (e.g. American electrical engineering honor society).
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I wasn't trying to deflect the discussion. It's just good to know where people get their knowledge. That's good scientific method, but thanks for answering.

And no, unfortunately that you are an EE major is not completely obvious. For all we know you could have been someone with no knowledge of EE except that you took a class on it for college general requirements. And even so, we'd have no way of confirming until another person whom we know is an EE major corroborate your method. It's always good to know for sure someone's credentials. In academia it's called peer review.
 
Martian

Martian

Senior Member
China's J-20 will require at least 630+ hours of flight testing

Assuming the development of China's J-20 approximates the F-22, we can expect the J-20 to undergo at least 630+ hours of flight testing.

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"In addition to aircraft ground testing, engine and aircraft subcomponent testing is also used to verify performance and durability. The amount of subcomponent testing and modeling completed easily makes the F-22 the most tested aircraft system ever developed by the Air Force (Figure 1). This includes more than 45,000 hours of wind tunnel testing, 12,000 plus hours of flight control simulation, over 10,000 hours of radar testing and more than 4,000 hours of signature testing.

Fqacm.jpg

Figure 1. F-22 Testing to Date"​
 
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challenge

Banned Idiot
Re: Final estimate for J-20 canards' radar return energy is 3.276x10^-19

according to russian aerospace magazine,J-20 has 0.05m RCS...(bbs.wforum.com/wmf)
so martian, you speculate that in the end, J-20 may have to abandone canard control?
in fact,a lot of blogger wondering why Chinese engineer selected canard control for J-20.
 
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latenlazy

Brigadier
Re: Final estimate for J-20 canards' radar return energy is 3.276x10^-19

challenge said:
according to russian aerospace magazine,J-20 has 0.05m RCS...(bbs.wforum.com/wmf)
so martian, you speculate that in the end, J-20 may have to abandone canard control?
in fact,a lot of blogger wondering why Chinese engineer selected canard control for J-20.
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Erm...I believe his conclusion was that with the proper materials and coating, the canards don't add much at all to its return signature...
 
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cataphract

New Member
WOah, calm down.

I do agree that Canards don't do much in terms of adding RCS, especially if properly designed. What I objected to was the 99.999% figure. If that were the case, trust me, there will be no need for stealth shaping.
 
Spartan95

Spartan95

Junior Member
Re: Final estimate for J-20 canards' radar return energy is 3.276x10^-19

Nice effort on the calculation for the J-20's RCS.

Martian said:
I don't have the faintest idea of the illumination cone for a directed military radar. However, to be of any use, I'll estimate that the illumination cone is 1km in radius. If the illumination cone is significantly smaller than 1km, I don't see how you can find an enemy fighter within a reasonable amount of time.
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The illumination cone is based on angle from the radar. This means that the radius of the illumination cone changes as the range changes.

It also means that AESA operating in search mode illuminates in a wider angle for search purposes, while in tracking/targeting mode it illuminates in a smaller angle thereby increasing the energy returned since there will be more power density.

Martian said:
After hitting the canards, we know that 99.999% of the reflected energy is reduced by the military-grade RAM. (See
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) This means that only 0.00001 (e.g. 1 - 0.99999 = 0.00001) of the impacting radar energy survives contact with the canard's RAM surface.
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The thing about RAM is that it is usually targetted at a very specific band of radar frequencies. It does not have the same radar absorbing quality for all frequencies. Hence, the radar energy absorption of the RAM is dependent on the frequency used. And clearly, these are very closely guarded secrets.
 
Asymptote

Asymptote

Banned Idiot
Re: Final estimate for J-20 canards' radar return energy is 3.276x10^-19

challenge said:
according to russian aerospace magazine,J-20 has 0.05m RCS...(bbs.wforum.com/wmf)
so martian, you speculate that in the end, J-20 may have to abandone canard control?
in fact,a lot of blogger wondering why Chinese engineer selected canard control for J-20.
Click to expand...

Actually, I am with Martian on this one. If F-22 or T-50 can designed with the traditional LARGE wings and smaller tail-wings and still achieved stealth, I am sure the same can apply to the canards - considering canards are so much smaller than the large main wings, its actually going to reduce the RCS.

The real problem I can see is most likely to the the radar return differentials created by the canards and the main wings - so when the radar wave hits edge of the canard THEN the main wing, there will be a differential created between those 2 surfaces. The traditional F-22 and T-50 does not have this problem because the main wings hides smaller tail-wings thus eliminating the problem of radar return differentials. (Until F-22/T-50 is being tail chased from the behind...in which case heat signatures from the engines become a bigger problem than the radar return)
 
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siegecrossbow

siegecrossbow

General
Staff member
Super Moderator
Re: Final estimate for J-20 canards' radar return energy is 3.276x10^-19

challenge said:
according to russian aerospace magazine,J-20 has 0.05m RCS...(bbs.wforum.com/wmf)
so martian, you speculate that in the end, J-20 may have to abandone canard control?
in fact,a lot of blogger wondering why Chinese engineer selected canard control for J-20.
Click to expand...

From what I've heard on Chinese website the reason was that Chinese engines may not be powerful enough to achieve supermanueverability using a conventional configuration.
 
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