Russian Fifth-Generation Fighter to Exceed Rivals

[amalakas]

Not digging at anyone but PhDs are like bachelors, there are good ones and so-so ones.

Actually the same can be said of just about any titles.

Dude, the same can be said about anything in life.

 

[500]

Why is F-22 spherical?

Who said its scheprical?

 

[below_freezing]

Dude, the same can be said about anything in life.

agreed but a PhD, no matter how stupid, is usually better in his/her own field, than a bachelor's in that same field, due to receiving double the training. 5 years is the difference between a middle school dropout and college student after all.

 

[siegecrossbow]

Who said its scheprical?

I think Chinaowns is trying to say that the plane isn't very angular, or has a lot of facets, like the F-117.

 

[no_name]

I do think it is angular, just that the edges has been smoothed over rather than a distinctive angular turn. Edges are generally a major source of scattering.

F-117 were designed at a time when computer has limited computational power. If looks as if it is made out of low resolution triangular mesh.

 

[gambit]

I have debunked all of your arguments, while you spout gibberish to waste my time digging through sources to disprove you and making nice little MS paint diagrams to try and educate you. And ignoring the arguments that you can't disprove.


Not once have you posted a source, this entire conversation has been one sided. You make CRAZY CLAIM, I pull up a paper telling you wrong. You ignore it, strawman by stating things and claiming that I said them just to debunk them yourself (most of the time getting many theories completely wrong).

According to your crazy pseudoscience theories (WITHOUT ANY SOURCES) stealth helicopters and stealth ships should all be spherical. Obviously you know more than all the engineers at Raytheon,Northrop etc...

In another response to someone else, I said that NEVER before have I posted parts of any paywall sources. To show the readers how wrong you are about this subject, how your pride got in the way of fruitful debate and how the same pride make you look stupid over and over, I am going to break my rule just this one time.

Time Domain Analysis of Creeping Wave (1997 Asia Pacific Microwave Conference)
Jinkui Yan Changlong Xu Deming Xu
Shanghai University
Chengzhong Road 20, Jiading, Shanghai, 201800, China

Creeping wave is an important concept of stealth technique. It originated from scattering problem of metal cylinder. In fact it generally exists in shading region of ordinary smooth objects. When the geometric dimension of an object is large enough (>10lambda), the quantity of creeping wave on the backward region can be neglected. But it may cause secondary scattering when an object exists in the shading region, and give a considerable backward scattering wave indirectly. To study propagation properties of creeping wave and to seek an effective method to reduce it are very important for stealth technique.

We will examine that paragraph...

- Creeping wave is an important concept of stealth technique.
Why?

- It originated from scattering problem of metal cylinder.
What is so special about a cylinder? It has a circumference, which contain curve radii. In radar detection, the sphere is the simplest body. A flat plate or a cylinder is a complex body and assuming finite dimensions because we live in the real world, either is electrically much more complex than the sphere. Since we know that the creeping wave does not exist on a planar, that mean we can rule out the flat plate, the cube, the pyramid, and any complex body that is an assembly of planar surfaces. For them, we have specular, surface and edge diffraction waves. Edge diffraction waves come from where the planar surfaces connect to each other.

- In fact it generally exists in shading region of ordinary smooth objects.
If the surface of the object -- a flat wall, a ball or a brick -- is not 'smooth' and if said surface is sufficiently 'rough', like sandpaper or the surface of a tree or a rock, then it is very possible that cumulative edge diffraction effects from all the surface 'rough' points will radiate enough off the surface that no creeping wave can exist. The 'shading' region is the side that is not touched by the radar signal. So the sentence is saying that if there is a sphere or spheroid object and if the surface of this object is 'smooth' enough, a creeping wave can come to be on the opposite side of radar signal collision.

This lead us back to the first question on why is the creeping wave important for creating a radar low reflective body. If it is important that mean curvatures are important and if curvatures are important, that mean curvatures MUST be incorporated into the design. Not just merely in and for parts of the aircraft but that curvatures are THE most important consideration in the aircraft's shaping itself. The F-117 is retired. Its angled faceting technique worked well enough that its RCS remains publicly unknown. But that technique is also aerodynamically limiting. Aerodynamics works best when the complex body of an aircraft contains curves at strategic points to give us the great variety of performane levels we have today in aviation. So when we add the two demands together, that of the need for as low radar reflective as the F-117 and with superior aerodynamic performance, curvatures as the major component in body shaping is inevitable, hence the need to study creeping wave behavior.

- When the geometric dimension of an object is large enough (>10lambda), the quantity of creeping wave on the backward region can be neglected.
First...The 'object' here is neutral. It could mean a true sphere or a spheroid. But since we are talking about the creeping wave, it could not imply an object that is an assembly of planar surfaces.

Second...Lambda λ is the symbol for wavelength and it looks like an inverted letter 'y'.

Third...Which is 'backward' and which is 'forward'...

In the illustration above, the radar is radiating away from itself -- forward. Any reflections off the aicraft would be back towards the direction of the seeking radar. It does not matter if the reflected signals actually reach the radar or not. Only the direction matter and that is called 'back scatter'. If the reflected signal is off the aircraft's underside, topside, or broadside and travels AWAY from the seeking radar, that is called 'forward scatter'. So the terms 'back scatter' and 'forward scatter' depends on perspective and the default understanding among radar engineers is the radar's position perspective.

What this sentence is saying and meaning are that if the body's dimensions, usually length and width, is greater than 10 times the wavelength of the impinging signal (>10lambda) then we need not worry about the initial creeping wave quantity because as the creeping wave travels on this curvatures enriched complex body, it will continue to lose energy via leaky waves, which would be dismissed as part of the clutter region if any are detected. The greater than 10 lambda ensures it. But the next sentence is also important...

- But it may cause secondary scattering when an object exists in the shading region, and give a considerable backward scattering wave indirectly.
The word 'object' here can be problematic in understanding what the authors meant. Since we know that a creeping wave exist only when there is a curve that create a 'shadow region', if there is a sharp interruption of path in this region, like a gap between panels or a hole created by a rock stuck on the bottom of someone's shoe, this is called 'curvature discontinuity' and will create edge diffraction effects FROM the creeping wave. That is why maintainers on the B-2, F-22, and F-35 must wear 'booties' over their footwear if they have to be on the aircraft's topside. It is even more important for the fighters because they are much more likely than the bomber to expose their topsides to seeking radars.

I told you that there is a direct relationship between object dimension and incident wavelength. If angled faceting is the superior path to RCS controls, then China would have had an F-117 equivalent flying by now. Instead, everyone in the world is going the F-22 alike path. The '>10lambda' where the creeping wave dies before completing circumference is well known. I make fun of 'Chinese physics' here but I have no doubt that Chinese engineers are smart enough to realize the F-117 is not what China should aspire to build. Your own countrymen, senors Jinkui Yan, Changlong Xu, and Deming Xu debunked you.

And this is why some people in life work designing machines while others (similar to you) are working cleaning toilets. I bet that you are one of those scum that go around telling girls that they are engineers when really they are "sanitation engineers"

I have no problems calling myself a 'sanitation engineer' among you clowns. Too bad for you that I used your own countrymen to clean up your BS. May be it is YOU who have been trying to impress women with your lies? Considering how pathetic your performance have been here, when you cannot even support your claim that the F-117 is 'much larger' than the F-22, you must still be a virgin. Whatever money you make, I recommend regular visits to the local cathouse wherever you are.

Readers...

There is a caveat to this (>10lambda) condition. We are talking about a pulsed radar system here. Take a meter measuring stick and assume that this is a pulse train. A 'pulse train' is a finite period of time of transmission where there is a grouping of pulses. The V/UHF (mhz) frequencies are meters long. The X-band frequencies (ghz), common to fighter aircraft radars, are centimetric -- centimeters long. At 40+ ghz and and we have millimetric -- millimeters long. That meter measuring stick should be helpful in visualization. A 'pulse' is also a finite period of time of transmission -- leading and trailing edge -- a characteristic called 'finite pulse length', which also mean finite amount of energy.

Many of these radar detection experiments are not actual experiments but rather theoretical against perfect electrical conducting -- PEC -- surfaces and materials. They establish various baselines of attenuation in circumferential waves and that 'lossy' surfaces and materials are introduced later. All surfaces and materials are 'lossy' to some degrees. Since it is not possible to perform experiments on nonexistent perfect anything, these 'lossy' materials and their estimated attenuation factor must be physically verified. This is one avenue in developing radar absorbent material (RAM).

Fire that pulse train of X-band frequency pulses at the Goodyear blimp. As each pulse impact the blimp, a portion of the pulse's energy will create the initial specular reflection because there is always a small spot on any curve that is flat enough to reflect directly back to incident direction. The rest of the pulse's energy will become circumferential waves. The blimp's circumference is much greater than '10lambda'. Finite amount of energy per pulse. Finite amount of energy per pulse train. The blimp's surface material, as a 'lossy' material, will absorb and convert to heat some of each pulse's energy. The result is that each pulse will die on the blimp's surface via tangentially radiated leaky waves and material related loss before it will make any significant distance in travel.

The caveat here is if we go to a continuous wave (CW) transmission mode, where there are no pulses, hence a continuous amount of energy hitting the blimp, then there will be a creeping wave that will complete the blimp's circumference and emerge from the shadow region.

 

[amalakas]

The caveat here is if we go to a continuous wave (CW) transmission mode, where there are no pulses, hence a continuous amount of energy hitting the blimp, then there will be a creeping wave that will complete the blimp's circumference and emerge from the shadow region.

And that is why the F22 is designed the way it is. Because a lot of russian Anti aircraft systems utilise X and L and K band radars that have CW modes. This is suprisingly effective to a degree most people do not realise. It does take a lot of power and it does advertise the seeker radar location to SEAD planes but if you are looking for a needle, it finds it. (where needle /= F22)

 

[gambit]

And that is why the F22 is designed the way it is. Because a lot of russian Anti aircraft systems utilise X and L and K band radars that have CW modes. This is suprisingly effective to a degree most people do not realise. It does take a lot of power and it does advertise the seeker radar location to SEAD planes but if you are looking for a needle, it finds it. (where needle /= F22)

Air defense radars, guns or missiles, have always the benefit of producing multiple antennas and assigning them different function. The counter to that is the low altitude approach because ground radars are limited to line-of-sight. It depends on who has the better intel and response time.

 

[amalakas]

Air defense radars, guns or missiles, have always the benefit of producing multiple antennas and assigning them different function. The counter to that is the low altitude approach because ground radars are limited to line-of-sight. It depends on who has the better intel and response time.

The also have the advantage of utilising each cell in a multi cell arrangement forming a pseudo-"multi static" configuration. The S-300 is such an example.

As I said before, a lot of people do not realise the amount of factors designers have to take into account in making a "low observability" asset.

The F22 was not made out of thin air or anyones' *ss. A lot of very clever people put a lot of man hours into it. despite of what i think about stealth as a pursuit .. I cannot dismiss the effort and brain power behind these things.

perhaps our asian friend is a bit wiser now....

 

[SQ8]

Air defense radars, guns or missiles, have always the benefit of producing multiple antennas and assigning them different function. The counter to that is the low altitude approach because ground radars are limited to line-of-sight. It depends on who has the better intel and response time.

But then again.. isnt the fact that the F-22 will have to get very close to any one of these sensors for them to actually pick it up its greatest strength??
It can stay at medium altitude and simply take out emitting systems via JDAMS... too bad the production cap will keep the F-22 as a silver bullet force.

 

[amalakas]

But then again.. isnt the fact that the F-22 will have to get very close to any one of these sensors for them to actually pick it up its greatest strength??
It can stay at medium altitude and simply take out emitting systems via JDAMS... too bad the production cap will keep the F-22 as a silver bullet force.

I did say "where needle /= (does not equal) F22" , I was talking about semi stealth or semi low observable targets, such as the EF2000, Rafale and any (if any) potentially low observable choppers, also UAVs and cruise missiles are kind of hard to pick up.

The F22 will not be easily picked up by these sensors whatever its flight path. And even if it is, it'll be way too close for comfort.

 

[STD]

India's gotta get a high no. of these russian 5th gen fighters in about 1-2 years after they are developed.
India's gotta get it at a time,when Pakistan and China would not be having 5th gen fighters.

 

[STD]

Lambda is also the symbol of wavelength,ask any questions if you want related to military,i have a great knowledge of military related things and have a doctorate in Applied Mechanics from IIT DELHI

 

[Patriot]

Lambda is also the symbol of wavelength,ask any questions if you want related to military,i have a great knowledge of military related things and have a doctorate in Applied Mechanics from IIT DELHI

and you still act like a retard.

 

[siegecrossbow]

and you still act like a retard.

IQ is very different from EQ. A man could get be a genius and get high degrees in Engineering but still act like a child.