Canards are MOVING parts. so they DO increase RCS (j20 canards are BIG one) Right ?
EVERYTHING is a contributor to the overall RCS of a body.
The above is just about my favorite and best illustration of how a radar system 'sees' a target: As a
CLUSTER of voltage spikes. The final user -- you, me, the pilot, or the radar operator -- does not see the target as such. We only see the typical 'blip' of light on a screen.
Anyway...Each of those spikes have a source and that source is a physical structure. Upon radar signal impingement,
ANY physical structure will reflect or as we in the radar field call the structure: A 'radiator' or 'emitter'. But generally the word 'radiator' is used. Since the physical structure is now a radiator, it become a 'contributor'.
Structure/radiator/contributor = contributorship.
So if you ever hear/read a radar engineer use the word 'contributor' or 'contributorship' you will know -- from now on -- he is talking about a radiation
STATUS of a physical structure belonging to a complex body while under radar bombardment. The reason I use the word 'status' is because if there is no radar bombardment, there is no radiation off the structure. Simple enough.
When you have a complex body like an aircraft with its many discrete structures that radiate, you will have destructive and constructive interference.
For example...
Principles of COSYNA Radar Modules
The scattering mechanism is known as "Braggscatter" and interprets the backwards directed part of the radar power induced by constructive interference of the electromagnetic wave with the structures of the entire radar footprint
When it comes to RCS control regarding the minimization of the overall RCS figure:
- Constructive interference = Bad. Very bad.
- Destructive interference = Good and we should strive to produce it all the time.
Constructive interference is when many radiated signals collide with each other and actually build to create a concentrated signal. Destructive interference is when they collide with each other and actually cancel or 'destroy' each other out.
Currently, there is no way for us to predict on how the many radiation patterns created by the above external stores will behave. Because an aircraft is a dynamic object, meaning it moves in space and it maneuvers, presenting different viewing angles to the radar at different times, the same cluster of physical structures may have mostly constructive interference one moment and mostly destructive the next. Or some ratio of the two types.
So the most important thing you should understand is this:
THE MORE PHYSICAL STRUCTURES THERE ARE FOR THE SEEKING RADAR, THE GREATER THE AMOUNT OF PHYSICAL CONTRIBUTORS OR CONTRIBUTORSHIPS TO THE OVERALL RADAR CROSS SECTION (RCS) VALUE.
That is why we enclosed or 'internalized' weapons such as missiles and bombs. To deny the seeking radar of these contributors.
Since we still must produce an aircraft with flight control surfaces and since those devices
WILL BE contributors, we must find some other ways to redirect as much radiation as possible away from the seeking radar's direction.
Enter 'planforming' or 'planform alignment'...
Stealth technology - Wikipedia, the free encyclopedia
Planform alignment is also often used in stealth designs. Planform alignment involves using a small number of surface orientations in the shape of the structure. For example, on the F-22A Raptor, the leading edges of the wing and the tail surfaces are set at the same angle. Careful inspection shows that many small structures, such as the air intake bypass doors and the air refueling aperture, also use the same angles. The effect of planform alignment is to return a radar signal in a very specific direction away from the radar emitter rather than returning a diffuse signal detectable at many angles.
In other words, if we cannot eliminate radiation off a physical structure, the least we can do is try to redirect their radiation patterns elsewhere, preferably away from the seeking radar's direction.
Structure/radiator/contributor + planforming = Reduced contributorship.
So how does canards threaten or increase the odds of a higher RCS? By their locations: In front of the wings, which equals to interactions of radiated signals that came off the trailing edges of the canards and the radiated signals that came off the leading edges of the wings. Because of the quite unpredictability of which type of interference that may rise, this make canards highly suspect, but not guaranteed, of being a higher RCS contributorship than other structures that may be in front of the wings.
Now...You may ask: What about the F-22's wings being in front of the horizontal stabilators? Would there be a higher risk as well?
Reasonable questions but then we have 'planform alignment' for the F-22...The leading edges of the wings have the same angle as the leading edges of the horizontal stabs. That and the horizontal stabs are much smaller than the wings. In RCS control tactics, placement of different sizes of diverse physical structures have direct effects on the energy level produced.
A surface is very much a 'conductor' or as we in the radar field call it the 'electrical path'. Sometimes we can exploit this for RCS control by using it as long as we can to redirect any portion of the radar signal that we cannot absorb, other times we should radiate the radar signal off into free space as soon as possible. Which option depends on the aircraft body design that we started off with. But usually we should try to get rid of it ASAP.
This is why most of the expert observers' attention is on the J-20's canards rather than the T-50's IRST device. The canards are much larger and they move in flight, no matter how minute those movements may be those movements do matter when it comes to interference.
Finally, do not expect this kind of foundational explanation of 'stealth' from the Chinese members here. None of them have the relevant experience and the results are the many laughable claims that damn near defy the laws of physics.
---------- Post added at 03:01 AM ---------- Previous post was at 02:59 AM ----------
At Gambit, I don't understand why you keep making moronic arguments.
J-20 canards are made of RAM-coated composite materials (which makes it stealthy) and it is carefully shaped to deflect radar. Su-30 and T-50/Pak-Fa IRST is a giant sphere of metal, glass, and electronics.
You can't seem to understand the difference.
Also, saw-toothed edges are designed to bleed radar energy away from the direction of the emitter. The IRST is simply a giant sphere that reflects substantial radar energy back to the emitter. I've already provided a citation from "How Does Stealth Technology Work?"
It is obvious you don't understand basic stealth technology.
See this post.
