1. The J-20 is designed for stealth. Rafale is not. We can expect J-20 canards to be made of composites. The Rafale probably has a much lower composite content to minimize cost.
The much higher use of composites for the J-20 canards and canard-fuselage junction will lead to a significantly smaller RCS than the Rafale.
true rafale is not a stealth fighter everyone knows it ,but the motto of my posting rafale pics is to
clear say that angulation of canards with respect to it's body in rafale is more ideal for stealth
than j20 's canards .Thats why i posted a pics in my above post clearly saying the importance
of angulation of canards with respect to stealth
2. The J-20 canards and junction have RAM (radar absorbent material) coating. Rafale does not.
good but it has no role or atbest minimal role in preventing backscattering of reflected radar
waves from a constantly mobile canards
ram coating are not always effective clear example is F117 shot down by serbian due to weather
changes
Radar-absorbent material, or RAM, is a class of materials used in stealth technology to disguise a vehicle or structure from radar detection. A material's absorbency at a given frequency of radar wave depends upon its composition. RAM cannot perfectly absorb radar at any frequency, but any given composition does have greater absorbency at some frequencies than others; there is no one RAM that is suited to absorption of all radar frequencies.
A common misunderstanding is that RAM makes an object invisible to radar. A radar absorbent material can significantly reduce an object's radar cross-section in specific radar frequencies, but it does not result in "invisibility" on any frequency. Bad weather may contribute to deficiencies in stealth capability. A particularly disastrous example occurred during the Kosovo war, in which moisture on the surface of an F-117 Nighthawk allowed long-wavelength radar to track and shoot it down. RAM is only a part of achieving stealth.
3. I have already calculated that the fraction of radar return for J-20 canard junction/gap is incredibly miniscule at 1.1745 x 10E-23 of the original power emission (see post #1262) prior to additional reduction from the RAM coating.
well the calculation of reflected is based upon static condition only but the calculation abrupty
changes when the plane moves at different angulation or manuveurs
4. Australia Air Power has already simulated the J-20 radar return across nine radar bands and concluded it can achieve all-aspect stealth across all nine radar bands (see post #1277).
again that god damned PO algorithm drama that is based upon static condition only &
mathematical equations ,which automatically changes when the target is mobile or at different angulation .It has not been tested in real time with radar frequencies of all range .It is based on
calculation only.
One more thing i like to say is Kaapo is an alarmist.his ploy is to delibertley sully the image of JSF-35 & to acquire F22 from US for australian air force .
5. Since the J-20 is in the test flight stage until 2018, the Chinese engineers could easily modify the J-20 design to include a "structure to hide the canard gap" if they felt it was necessary.
yes it is in protype stages so u can say that changes can be made on it & i have to accept it.But my view is they should remove canards & have 3 axis TVC instead .But it wont happen i think
6. The shape of the junction between the J-20 canard and fuselage is absolutely critical. My calculation was based on a flat surface junction. If, as I suspect, the J-20 canard junction is shaped at a 45-degree angle like the F-22 (see below) then the incoming radar signal will become similarly attenuated beyond detection and also deflected away.
yes thats the key which j20 dont have but rafale has ,as their is abrupt change in angulation due
to DSI intake in j20 & that's what i am trying to say that these provide corner reflecting surface which is detrimental for stealth purpose
F-22 Raptor airduct-fuselage gap is not a stealth hindrance
Normally, the gap between the F-22 Raptor airduct and the fuselage is poor stealth design. A gap permits additional radar reflections and it should be avoided. However, a close examination of the F-22 Raptor's airduct-fuselage gap shows no penalty in stealth.
The gap between the F-22 Raptor airduct and fuselage is clearly noticeable.
F-22 Raptor underside. The back of the airduct and fuselage gap is intentionally angled at approximately 45 degrees.
A ray-trace analysis of a radar beam shows a minimum of four reflections from the RAM-coated surface of the F-22.
The effectiveness of RAM coating is a 99.684% reduction (or 0.00316 left) in radar energy (see citation below).
To calculate the amount of the original radar energy that entered the F-22 airduct-fuselage gap and was able to egress/reflect out of the gap after striking the angled surface in the back, we have to reduce the original radar energy by four reflections from the RAM-coated airduct and fuselage walls.
Amount of original radar energy that can escape F-22 airduct-fuselage gap = (0.00316) ^ 4 = 9.97 x 10E-11
The maximum amount of radar energy that can escape from the F-22 airduct-fuselage gap is identical to the maximum radar energy that can escape from the F-22 S-duct. The radar reflections are both extremely low and virtually undetectable at 9.97 x 10E-11 of the original incoming radar energy.
true but it doesnt act as corner reflecting surface like canards while it's backscaterring is absorbed 90-95% by body while canards 's back scaterring of radar waves is impossible to absorb 100% even if it may be build of 100% composites & have RAM coating in canard fuselarge juntion while it
is mobile constantly
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I don't understand why Dr. Somnath thinks the J-20 canard junction could be a stealth hindrance. Australia Air Power has already modeled it across nine radar bands and concluded there is no design problem to match the F-22 in all-aspect stealth.
well thats why i clearly posted the pics explaining the importance of canards location with respect
to it's body regarding stealth & also u can see from the pics below as there is abrupt changes in
alignment angle of canards due to gap between DSI & CANARDS
The key question is the lack of stealthy flat nozzles on the J-20. Will China be able to develop stealthy flat nozzles without significantly impairing the thrust output/engine performance of the J-20 by 2018?
well this is another factor, but JSF also has round nozzles with saw tooth edges & also u cannot
have 3 axis TVC if u have 2d nozzles.But most important aspect of stealth is Frontal radar cross
section as this is the key for most aerial bvr combat & that's why canard has always raises doubt
regarding stealth aspects of plane as compare to rear tail fins of F22 & pakfa though canards have
more advantage in manuverabilty as compare to rear tail fins of F22 & pakfa
Australia Air Power: J-20 is a "genuine Very Low Observable design"
J-20 Mighty Dragon is a "genuine Very Low Observable design" except for round engine nozzles, which can be fixed.
"This study has therefore established through Physical Optics simulation across nine radio-frequency bands, that no fundamental obstacles exist in the shaping design of the J-20 prototype precluding its development into a genuine Very Low Observable design.
Engineers and Scientists who work in stealth (AKA Low Observable) designs have a way for explaining it to lay people: Stealth is achieved by Shaping, Shaping, Shaping and Materials (Denys Overholser).
The F-22A is clearly well shaped for low observability above about 500 MHz, and from all important aspects. (article continues)"
well same thing as i said above no reapeat on this
BUt i want to ask a simple question answer me
ARE CYLINDERS LESS STEALTHY COMPARE TO FLAT SURFACE?
In this context it should also be noted that a flat plate focuses its backscattering
on a very narrow angular sector, with a high RCS value.
A sphere, by contrast, has a low RCS value which is uniform at all angles.
Thus, on a limited angular sector around the specular direction, spheres
and cylinders give the lowest RCS values. If otherwise, RCS must be kept
low on a wide angular sector, then it is better to use very narrow-beam
shapes such as the flat plate, correctly aimed in order to avoid the specular
flash [7].
http://hamwaves.com/stealth/contents/chapter_01.pdf
can the jet engine have stealth features it self?
are single piece canopies more stealth than two pieces if so what about F-35, B-2 or F-117?
F-22 flat nacelles only give a very big RCS when the radar is on a perpendicular direction to the radar,
Square trihedral corner reflector Strongest radar return due to triple reflection of incident wave
Right dihedral corner reflector Second strongest radar return due to double reflection of incident wave; decreases from maximum slowly with changing θ and rapidly with changing φ
Flat plate Third strongest radar return due to direct reflection of incident wave; decreases rapidly as incidence angle changes from perpendicular
Right circular cylinder Strong radar return as aspect (θ
changes, but decreases rapidly as azimuth (φ
changes
Aerospaceweb.org | Ask Us - Radar Cross Section
From a frontal view the F-22 is very stealthy
however radars will see the F-22 from angles more like this
now i have tried my level best to explain my POV regarding stealth aspect as clearly as possible within my capabilties.though
