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Radar 101 and DSI intakes discussion

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Ronny

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the caret intake is stealthy the fact F-22 uses it shows is very practical, you are misunderstanding DSI, the only reason Lockheed chose the DSI, was it was cheaper to build and cheaper to maintain, in fact i posted a Lockheed document where they say it, Caret intakes can be built with fixed geometries or Variable geometry, they are more expensive to build and maintain certainly, they are as stealthy as DSI but they are more expensive, trying to portrait DSI as the ultimate stealth intakes is false in fact the bump destroys the alignment the fore body chines and intake cowl have with the vertical tails, but from a frontal cross section is not a problem, but since they are spherical in nature the bump has a RCS that approaches a sphere, contrary to the caret intake that is aligned to the facets of F-22, the chines and cowl intake of F-22 are aligned with the vertical tails and wing leading edges, certainly the bump is not aligned as the caret intake is with the rest of the airplane
From frontal, DSI is stealthier than caret inlet because the smooth curve will have fewer surface scattering point than multiple sharp edges, surface discontinuity and moving parts of variable inlet. That is an advantage for VLO aircraft. Second generation of stealth aircraft use blended curve instead of flat facet like F-117 for the same reason.
C8506FC1-3DC1-45DA-B860-98605EC4E833.png
4C4EF029-4669-4FCC-8723-4C4D322AE4D1.jpeg
 
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pegasus

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From frontal, DSI is stealthier than caret inlet because the smooth curve will have fewer surface scattering point than multiple sharp edges, surface discontinuity and moving parts of variable inlet. That is an advantage for VLO aircraft. Second generation of stealth aircraft use blended curve instead of flat facet like F-117 for the same reason.
Ronny stealth is better understood if you consider light.

Light behaves like particle and wave, waves have diffraction, waves go around corners, see this point, this is very important.

I will give you what is really stealth, imagine a person in the middle of a street running from north to south, his eyes are are looking to the south and his back is facing the north.

there is a perpendicular street, running from east to west ahead of him, where a tank that is going to the west is in front of him, the tank has its cannon aiming towards the west and two lamps at the front of the tank, pointing at the west too, so the tank crew can see what is ahead of the tank.

It is a dark night, when the tank fires a shell, it is like a particle, the shell goes in a direction from east to west, then it will never harm the person standing on the street running from north to south.

Now the tank turns on the lights, and the same person standing in the middle of the street that goes from north to south can see the tank, why can that person see the lights? why? simple light does not travel only from east to west but also from north to south and south to north.

If you understand that you can see and understand stealth, light and electromagnetic waves bend around corners, they do not behave only like particles, does not matter if it is DSI or caret intakes, some part of the electromagnetic wave always goes back to the radar, always, and the creeping wave exists because light and electromagnetic waves bend around corners, so you always detect DSI or caret intakes; for a powerful radar both are as visible as the whole aircraft, in few words stealth only exist if instead of looking at the tank that person is trying to see a firefly.


If you are walking at night in a very dark night and a person ahead of you is holding a lamp facing ahead of both of you, you will still be able to see your friends back, that is the creeping wave, the shadow is not total still there is some light because light travels in all directions.


Nothing is invisible, the caret or DSI intakes for powerful radars are visible, in the same way, B-2 is not invisible either, the main reason is diffraction, not reflection, reflection concentrates the electromagnetic emission in one direction, but diffraction goes everywhere so it does not matter the round surfaces, in fact in that respect is better the facets because they tend to concentrate the electromagnetic emission into a single direction, but diffraction and power density makes even a faceted object visible either to light or other frequencies, so remember light has also constructive interference in few words two lamps will concentrate light in one direction, so several radars will unmask stealth aircraft too, nothing is truly stealthy, people fantasize about stealth, the only thing that makes something stealthy is a very weak radar only that
 
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Ronny

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Ronny stealth is better understood if you consider light.

Light behaves like particle and wave, waves have diffraction, waves go around corners, see this point, this is very important.

I will give you what is really stealth, imagine a person in the middle of a street running from north to south, his eyes are are looking to the south and his back is facing the north.

there is a perpendicular street, running from east to west ahead of him, where a tank that is going to the west is in front of him, the tank has its cannon aiming towards the west and two lamps at the front of the tank, pointing at the west too, so the tank crew can see what is ahead of the tank.

It is a dark night, when the tank fires a shell, it is like a particle, the shell goes in a direction from east to west, then it will never harm the person standing on the street running from north to south.

Now the tank turns on the lights, and the same person standing in the middle of the street that goes from north to south can see the tank, why can that person see the lights? why? simple light does not travel only from east to west but also from north to south and south to north.

If you understand that you can see and understand stealth, light and electromagnetic waves bend around corners, they do not behave only like particles, does not matter if it is DSI or caret intakes, some part of the electromagnetic wave always goes back to the radar, always, and the creeping wave exists because light and electromagnetic waves bend around corners, so you always detect DSI or caret intakes; for a powerful radar both are as visible as the whole aircraft, in few words stealth only exist if instead of looking at the tank that person is trying to see a firefly.


If you are walking at night in a very dark night and a person ahead of you is holding a lamp facing ahead of both of you, you will still be able to see your friends back, that is the creeping wave, the shadow is not total still there is some light because light travels in all directions.

Nothing is invisible, the caret or DSI intakes for powerful radars are visible, in the same way, B-2 is not invisible either, the main reason is diffraction, not reflection, reflection concentrates the electromagnetic emission in one direction, but diffraction goes everywhere so it does not matter the round surfaces, in fact in that respect is better the facets because they tend to concentrate the electromagnetic emission into a single direction, but diffraction and power density makes even a faceted object visible either to light or other frequencies,
That isn't exactly correct.
A complex object will reflect radar wave in many ways
3.jpg
But in general they can be grouped into:
Specular return: this is the most significant form of reflection, surface acts like a mirror for the incident radar pulse. Most of the incident radar energy is reflected according to the law of specular reflection ( the angle of reflection is equal to the angle of incidence).
Traveling/Surface wave return: an incident radar wave strike on the aircraft body can generate a traveling current on surface that propagates along a path to surface boundaries such as leading edge, surface discontinuous …etc, such surface boundaries can either cause a backward traveling wave or make the wave scattered in many directions
Diffraction: wave striking a very sharp surface or edge are scattered instead of following law of specular reflection.
Creeping wave return: this is a form of traveling wave that doesn’t face surface discontinuous and not reflected by obstacle when traveling along object surface , thus it is able to travel around the object and come back at the radar. Unlike normal traveling wave, creeping wave traveled along surface shadowed from incidence wave (because it has to go around the object). As a result, the amplitude of creeping wave will reduce the further it has to travel because it can’t feed energy from the incident wave in the shadow region. Creeping wave mostly traveled around a curved or circular object.

A.PNG
When the object size is at least 10 times the wavelength, we say it is in optical region, in this regime, specular mechanisms dominate. In this regime, “surface wave” mechanisms are small contributors to RCS, but are still present. If the wavelength is small relative to the surface, these waves are weak and their overlap will generate maximum backscatter when the radar signal is at grazing angles. When these currents encounter discontinuities, such as the end of a surface or change in material or sharp edge, they abruptly change and emit edge waves or edge diffraction. That why DSI is stealthier than a variable inlet, because DSI can be smooth while variable inlet must have gaps and discontinuities
Type of wave scattering.PNG
df-sos-lowf_3_diffraction.jpg



To reduce the effect of discontinuities scattering at panel gaps or trailing edge, one common solution is serration
2.png


When the wavelength approach the size of the object (for simple object such as a sphere that mean 1 < 2πa/λ < 10 ) we say the object is in Mie region, in this region, a creeping wave travels around the object and back towards the receiver where it either interferes constructively or destructively with the specular return. So it can either increase or reduce the total RCS value. With that said, the magnitude of the creeping wave return is much smaller than specular return even in this case.
5.PNG

Some objects are easier to curve around than the other, stealth aircraft are designed in a way that would minimize the creeping wave return coming back to the source, such as not using pure cylinder shape

3.PNG
1.png


so remember light has also constructive interference in few words two lamps will concentrate light in one direction, so several radars will unmask stealth aircraft too, nothing is truly stealthy, people fantasize about stealth, the only thing that makes something stealthy is a very weak radar only that
Stealth isn't invisible, stealth is making your vehicles harder to detect to the enemy so you can attack them first. Everything is stealth if you stay far enough and nothing is stealth if you are close enough. The goal of stealth design is to make this distance shorter.
noise.jpg
 

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Ronny

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improvements in radar technology render stealth useless
It doesn't as long as there are improvements in jamming technology because jamming depends on S/N ratio so stealthier aircraft cut down burn through distance

Capture.PNG

diffraction and power density output of radars make stealth useless
It doesn't, there are various ways to reduce/eliminate edge diffraction such putting RAM on trailing edge and leading edges

9.jpgedge treatment.PNG
Capture.PNG
 
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pegasus

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That isn't exactly correct.
A complex object will reflect radar wave in many ways
View attachment 620459
But in general they can be grouped into:
Specular return: this is the most significant form of reflection, surface acts like a mirror for the incident radar pulse. Most of the incident radar energy is reflected according to the law of specular reflection ( the angle of reflection is equal to the angle of incidence).
Traveling/Surface wave return: an incident radar wave strike on the aircraft body can generate a traveling current on surface that propagates along a path to surface boundaries such as leading edge, surface discontinuous …etc, such surface boundaries can either cause a backward traveling wave or make the wave scattered in many directions
Diffraction: wave striking a very sharp surface or edge are scattered instead of following law of specular reflection.
Creeping wave return: this is a form of traveling wave that doesn’t face surface discontinuous and not reflected by obstacle when traveling along object surface , thus it is able to travel around the object and come back at the radar. Unlike normal traveling wave, creeping wave traveled along surface shadowed from incidence wave (because it has to go around the object). As a result, the amplitude of creeping wave will reduce the further it has to travel because it can’t feed energy from the incident wave in the shadow region. Creeping wave mostly traveled around a curved or circular object.


When the object size is at least 10 times the wavelength, we say it is in optical region, in this regime, specular mechanisms dominate. In this regime, “surface wave” mechanisms are small contributors to RCS, but are still present. If the wavelength is small relative to the surface, these waves are weak and their overlap will generate maximum backscatter when the radar signal is at grazing angles. When these currents encounter discontinuities, such as the end of a surface or change in material or sharp edge, they abruptly change and emit edge waves or edge diffraction. That why DSI is stealthier than a variable inlet, because DSI can be smooth while variable inlet must have gaps and discontinuities





To reduce the effect of discontinuities scattering at panel gaps or trailing edge, one common solution is serration
View attachment 620476


When the wavelength approach the size of the object (for simple object such as a sphere that mean 1 < 2πa/λ < 10 ) we say the object is in Mie region, in this region, a creeping wave travels around the object and back towards the receiver where it either interferes constructively or destructively with the specular return. So it can either increase or reduce the total RCS value. With that said, the magnitude of the creeping wave return is much smaller than specular return even in this case.


Some objects are easier to curve around than the other, stealth aircraft are designed in a way that would minimize the creeping wave return coming back to the source, such as not using pure cylinder Stealth isn't invisible, stealth is making your vehicles harder to detect to the enemy so you can attack them first. Everything is stealth if you stay far enough.
you are correct, the point is light is another electromagnetic wave, these diagram most of the time present stealth as if reflection is the only aspect of radars because diffraction while we experienced it every day is far more complex than the drawing you posted; on your every day life you see what a radar does, your eyes are radar receivers, they only happen to use a limited range of frequencies, light in fact presents what radars do, shadows, search lights, mirrors, they basically do what you are describing in those pictures, however we have a big advantage over aircraft, the sun has too much power density, aircraft radar have very limited power thus stealth seems far too complex, but is not, aircraft are more like us at night with lamps and search lights, thus RAM, faceting and creeping waves seem more complex, but they are not, radars by increasing the power density will see stealth aircraft well.

When you facet an aircraft or you add chines and flat sides, a weak radar is like a person looking at the distance trying to see details his eyes can not let him see due to distance.

Then stealth becomes "useful" most radars will see well F-22 at close ranges, it does not matter stealth treatment at short distances; at long distances then the ability gets reduced and chines, planform alignment then they become useful, why? simple because there are so little radar signals that faceting will weaken even further the signal and it will seem the aircraft has disappeared from radar.

The reality is if you have enough power density, in few words if the radar is powerful enough, it will become like daylight stealth will not work, why because on your daily life the sun let you see flat surfaces, round surfaces only some gases will appear invisible or some materials transparent like glass.


So when people think DSI or caret are really stealthy the reality is radars are so weak, that a few tricks here and there will reduce their visibility from some distances, add powerful radars and these are very visible. Is not that the creeping wave disappears by flattening the sides of F-22 forebody, if the radar signal is weak, it will be weakened enough for some types of radar to disappear from their view, but believe me your daily life at night and obscurity puts you in the same situation aircraft are, but add power density and you will discover nothing is stealth, it is only that aircraft are blind or have weak lamps aka weak radars
 
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Inst

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For Ronny and Pegasus's convo, I'll leave this here:


I.e, compromised, but otherwise jamming-immune radar.

The other thing is, Ronny has a point about how potent the jam / stealth combo is; if we go to a visible light analogy, imagine the object you're looking for is already very dark, a few lumens above black. Then someone flashes a searchlight in your eyes.

===

Regarding MFR, I'm going back to the NASA page and they're still implying that it's loss of static pressure at altitude that results in loss of thrust at altitude. Which is rather weird, because for a sufficiently sized inlet moving at a sufficient speed, you should have all the static pressure / MFR you need.

Here's a different article discussing why Turbojets (not Turbofans!) lose performance at altitude, albeit an old one:

 

pegasus

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For Ronny and Pegasus's convo, I'll leave this here:



The other thing is, Ronny has a point about how potent the jam / stealth combo is; if we go to a visible light analogy, imagine the object you're looking for is already very dark, a few lumens above black. Then someone flashes a searchlight in your eyes.



you want to pretend to see i will be jammed, the reality is you will know some one is in front of you in the middle of the night, a jammer is a good way to know where an enemy aircraft is, basically anti-radiation missiles do that, basically that is the whole point when a fighter illuminates you, you can simply let his own radar to guide you where is him, thus passive system are always a way to attack, radar silence or jumping from one frequency to another is what modern stealth aircraft do.

But at the end the best stealth is passive detection, if someone is jumping from red to green or yellow lights, in example traffic light, you still will be able to see the traffic light, well radars are the best way to know where you are that is the reason they use IRST, in fact if we are 2 or 3 people they might find me and blind me but the other 2 will see the enemy position very clear so snipper will beat the enemy.

Will a good radar now detect DS I intakes? yes it will and same caret intakes, it is only when it is very dark that stealth works, F-117 was effective for radars on MiG-21 or MiG-23, modern aircraft like Su-35, F-22 or J-20 supposedly need to find F-117 at relatively longer ranges than MiG-21 that is why F-117 was obsolete and phased out.

The major problem for radars is energy is absorbed by the atmosphere so the signal weakens , is like a lamp at night there is a limit where you lights will let you see, cars at night driving have the same problem driving on highways, their lights only let them see not very far but sometimes they can be seen by some one else at longer distance, so radar sensitivity plays a very important part
 
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pegasus

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It is a shame to see some contributors posting what appears to be little better than warmed up 90’s Russian-fan-boy “stealth is rubbish” narratives mixed in with some legitimate and interesting technical detail on this topic.
The problem is trying to unpick one from the other while the former acts to undoubtedly undermining the credibility of the latter.
Literally no one is saying that DSI are ”stealth perfection” or purporting the permanent magical powers and unquestionable immortal invulnerability of low-observatory aircraft.
But some of the generalised arguments presented above by some contributors are almost equally absurd in the opposite direction.

Radar cross-section σ is as defined as:

σ =4·π·r2·Sr/St

mit
σ: measure of the target's ability to reflect radar signals in direction of the radar receiver, in [m²]
St: power density that is intercepted by the target, in [W/m²]
Sr: scattered power density in the range r, in [W/m²]
https://www.radartutorial.eu/01.basics/Radar Cross Section.en.html






see how it is basically the formula treats energy as reflected energy, basically as particles, best example a mirror or a metal plate, however light is not only reflected but also diffracted, F-22 will be detected, yes at short ranges for some powers densities, at longer ranges it will be not detected, then if you change power density, the RCS fluctuates upon the power density reflected, it is not fixed, yes σ is based upon the geometry of the aircraft but since F-22 is close to the radar power density is enough to allow a weak radar to detect it at closer ranges, but at long ranges it will not, you change the power density you change the range you will detect it at longer ranges, is F-22 invisible to radar? no it is not, it simply says low power density will make it harder to detect.

As i told before, the simplest example is the human eye, if you look at something close you can see details, further it goes from you details disappear. and if it is very far you will not see the object at all.


Thus is not that the object is invisible because is not, it means the power density is low, in this case of light, the amount of lumens is low.

DSI intakes are very visible at short ranges, radars detect them well, it is at longer ranges when shape or RAM will aid to reduce visibility. only that, the formula gives you that


The target radar cross-sectional area depends of:

  • the airplane’s physical geometry and exterior features,
  • the direction of the illuminating radar,
  • the radar transmitters frequency,
  • the used material types.
number two tells you that a plate at different angles from the radar will reduce or increase reflection RCS thus F-22 will have different RCS to different radars positioned at different directions but at the same distance, see that because detectability is also dependant upon the radar network, so what stealth does is makes it more expensive radar networks, but F-22 is not invisible nor DSI the best intake, it is detectable
 
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kaiserd

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It is a shame to see some contributors posting what appears to be little better than warmed up 90’s Russian-fan-boy “stealth is rubbish” narratives mixed in with some legitimate and interesting technical detail on this topic.
The problem is trying to unpick one from the other while the former acts to undoubtedly undermining the credibility of the latter.
Literally no one is saying that DSI are ”stealth perfection” or purporting the permanent magical powers and unquestionable immortal invulnerability of low-observatory aircraft.
But some of the generalised arguments presented above by some contributors are almost equally absurd in the opposite direction.
is not about Russian or not is about physics,

Radar cross-section σ is as defined as:

σ =4·π·r2·Sr/St

mit
σ: measure of the target's ability to reflect radar signals in direction of the radar receiver, in [m²]
St: power density that is intercepted by the target, in [W/m²]
Sr: scattered power density in the range r, in [W/m²]
https://www.radartutorial.eu/01.basics/Radar Cross Section.en.html



see how it is basically the formula treats energy as reflected energy, basically as particles, best example a mirror or a metal plate, however light is not only reflected but also diffracted, F-22 will be detected, yes at short ranges for some powers densities, at longer ranges it will be not detected, they if you change power density, the RCS fluctuates upon the power density reflected is not fixed, yes σ is based upon the geometry of the aircraft but since F-22 is close to the radar power density is enough to allow a weak radar to detect it at closer ranges, but at long ranges it will not, you change the power density you change the range you will detect it at longer ranges, is F-22 invisible to radar? no it is not, it simply says low power density will make it harder to detect.

As i told before, the simplest example is the human eye, if you look at something close you can see details, further it goes from you details disappear. and if it is very far you will not see the object at all.


Thus is not that the object is invisible because is not, it means the power density is low, in this case of light, the amount of lumens is low.

DSI are very visible at short ranges, radars detecte them well, it is at longer ranges when shape or RAM will aid to reduce visibility. only that, the formula gives you that


The target radar cross-sectional area depends of:

  • the airplane’s physical geometry and exterior features,
  • the direction of the illuminating radar,
  • the radar transmitters frequency,
  • the used material types.
number two tells you that a plate at different angles from the radar will reduce or increase reflection RCS thus F-22 will have different RCS to different radars positioned at different directions but at the same distance, see that because detectability is also dependant upon the radar network, so what stealth does is makes it more expensive radar networks, but F-22 is not invisible nor DSI the best intake, it is detectable
I hope it is clear my comments are not in anger but in bewilderment.

Yes I assume literally everyone reading this understands the basics of most of what you are saying above, we understood it well before you said more or less the same thing 3-4 previously above.

It’s the conclusions that you choose to draw that are where you start loosing me completely.

The echo of Russiab-fan-boy-nonsense is various extremely self-serving (to your argument - no offence meant) assumptions around the availability, close proximity, and power of various powerful radars (plus associated command and control issues) and the required lack of counter measures (passive and active) by the low observatory aircraft in question. That remains an unlikely scenario and the worlds combat aircraft producers continue to produce new aircraft that are to lessor or greater extents low observatory in nature.

And going back to the actual topic here; what on earth does your argument actually have to do with DSI inlets?
DSI inlets are understood to be be superior to other more traditional “fixed” inlet designs, including but not limited to from a “stealth” perspective, as part of the overall integrated design of the aircraft in question.
And while you are correct a fully variable inlet with moving parts etc. should still have some advantages over a DSI in some parts of an aircraft’s performance envelope it also has other disadvantages such as weight, complexity and a greater difficulty in managing signature management.
As such statements like “DSI are very visible a short range” make little real sense.
More visible than an equivalent variable geometry inlet? More visible than an equivalent more traditional fixed inlet?
As I previously mentioned
 

Ronny

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you are correct, the point is light is another electromagnetic wave, these diagram most of the time present stealth as if reflection is the only aspect of radars because diffraction while we experienced it every day is far more complex than the drawing you posted; on your every day life you see what a radar does, your eyes are radar receivers, they only happen to use a limited range of frequencies, light in fact presents what radars do, shadows, search lights, mirrors, they basically do what you are describing in those pictures, however we have a big advantage over aircraft, the sun has too much power density, aircraft radar have very limited power thus stealth seems far too complex, but is not, aircraft are more like us at night with lamps and search lights, thus RAM, faceting and creeping waves seem more complex, but they are not, radars by increasing the power density will see stealth aircraft well.

When you facet an aircraft or you add chines and flat sides, a weak radar is like a person looking at the distance trying to see details his eyes can not let him see due to distance.

Then stealth becomes "useful" most radars will see well F-22 at close ranges, it does not matter stealth treatment at short distances; at long distances then the ability gets reduced and chines, planform alignment then they become useful, why? simple because there are so little radar signals that faceting will weaken even further the signal and it will seem the aircraft has disappeared from radar.

The reality is if you have enough power density, in few words if the radar is powerful enough, it will become like daylight stealth will not work, why because on your daily life the sun let you see flat surfaces, round surfaces only some gases will appear invisible or some materials transparent like glass.


So when people think DSI or caret are really stealthy the reality is radars are so weak, that a few tricks here and there will reduce their visibility from some distances, add powerful radars and these are very visible. Is not that the creeping wave disappears by flattening the sides of F-22 forebody, if the radar signal is weak, it will be weakened enough for some types of radar to disappear from their view, but believe me your daily life at night and obscurity puts you in the same situation aircraft are, but add power density and you will discover nothing is stealth, it is only that aircraft are blind or have weak lamps aka weak radars
The wavelength of visible light is too small compared to human size object for the creeping wave return phenomenon to happen and human eye doesn't suffer from side lobes clutter like a radar so I don't think they are really that similar.
clutter.png


personally, I think of stealth aircraft as camouflage sniper. They both trying their best to reduce signature, only a very small part of the total signature comming back to the observer and that signature is harder to distinguish from clutter. You see, even with a powerful emitter like the sun, it is still very hard to detect a camouflaged sniper at long range. That isn't because the sun isn't bright enough, but because the surrounding scenery will also reflect signals to you. Similarly, a powerful radar will not only see stealth aircraft, but its wave will also be reflected from birds, insects, ground, sea surface. ..etc. Doppler shift help mitigate this issue somewhat, but not totally because it also depends on aspect angle with the threat. An aircraft moving 700 km/h perpendicularly to your radar can easily has less Doppler shift than a bird flying straight at your radar. An insect 50 meters from your radar can have bigger reflection strength than an F-16 from 300 km away. So stealth work not only with very weak radar. The aim isn't 100% invisible, the aim is cut down detection range short enough so you can attack first. A stealth aircraft isn't invisible but it doesn't have to, like a sniper, if your enemy can detect you from dozen meters away that is already enough
ghillie-suit-FRGS-1800.jpg


you want to pretend to see i will be jammed, the reality is you will know some one is in front of you in the middle of the night, a jammer is a good way to know where an enemy aircraft is
Who say the jammer and the aircraft have to be at the same location? There are many methods to separate the physically distance between the jammer and the thing it supposed to protect.
From stand off jammer like EA-18G, EA-6B, B-52 CCJ to stand in jammer such as MALD-N, SPEAR-EW
SPEAR-EW.PNG
mald.png

They can also operate jamming between 2 or more jammers



basically anti-radiation missiles do that, basically that is the whole point when a fighter illuminates you, you can simply let his own radar to guide you where is him
While that sounds like a great method in theory, in practice, it is very terrible. Because aircraft can fly very fast, A2A missile have to aim at a predicted location of target instead of its current location. This predicted location is calculated base on the range to enemy aircraft as well as their direction of travel, speed and altitude. All these vital information is normally measured by your radar or LRF. But when your radar is jammed, using RWR you only get the direction, you do not know how far is your enemy or how fast they travel. Anti radar missiles must use pure pursuit guidance so, they have almost zero chance of hitting a maneuvering aircraft and they will miss if your enemy happens to turn off their radar in terminal phase.
A.PNG
 
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Ronny

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Will a good radar now detect DS I intakes? yes it will and same caret intakes
Can you see an ant with your eye? yes
Can you see an elephant with your eye? yes
But they are not equally visible at the same range.

F-117 was effective for radars on MiG-21 or MiG-23, modern aircraft like Su-35, F-22 or J-20 supposedly need to find F-117 at relatively longer ranges than MiG-21 that is why F-117 was obsolete and phased out
The major reasons for F-117 phase out were:
_ Limited weapon load and weapons of choice: only 2 internal LGB or JDAM
_ Limited sensors: only FLIR no Radar, no RWR, no IRST, no MWS
_ Limited defense: no supersonic speed, no agility, no chaff, no flares, no ECM system
_ High maintenance cost.
But F-117 stealth was very effective
 

pegasus

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The wavelength of visible light is too small compared to human size object for the creeping wave return phenomenon to happen and human eye doesn't suffer from side lobes clutter like a radar so I don't think they are really that similar.
our eyes while use small wavelength high frequencies, radar also use small frequencies , in fact an F-16 is pretty huge for radar frequencies, to understand waves you have to see them as waves, they are not particles, they are not rays or arrows, in fact the fact you can jam a radar means they are having diffraction interference, basically a shadow explains you why light is not a particle but a wave, objects generate shadows, but if you are behind the shadow you still can see, electromagnetic waves try to fill everything, even a laser is visible some of its light is not coherent some of its light comes to our eyes, the net effect is creeping waves exist in light.

Creeping waves exist because electromagnetic waves interact with objects and diffraction exist, in particles to bend its trajectory you need a magnetic or electric field, in big objects gravity, but objects are not waves.

Particles by nature a bullet for example can not generate an interference pattern, so basically can not be jammed so if light was a particles you will have perfect darkness in a shadow and once you enter a shadow zone you will not be able to see even in daylight, but light bends around corners, so you can see

As the wavelength gets bigger waves behave more like waves and not like particles with respect aircraft, so the current effect stealth loses its meaning.

basically the facets or flat walls of the F-22 sides are mirrors for radar frequency so what they do is if the creeping wave is weak, they focus it in the direction of the flat sides of the chines or sidewalls, but it does not get eliminated 100% because radar is like light and not particles, some will go back to the radar, chines offer aerodynamic benefits too so not everything is stealth,
 
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Ronny

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our eyes while use small wavelength high frequencies, radar also use small frequencies , in fact an F-16 is pretty huge for radar frequencies, to understand waves you have to see them as waves, they are not particles, they are not rays or arrows, in fact the fact you can jam a radar means they are having diffraction interference, basically a shadow explains you why light is not a particle but a wave, objects generate shadows, but if you are behind the shadow you still can see, electromagnetic waves try to fill everything, even a laser is visible some of its light is not coherent some of its light comes to our eyes, the net effect is creeping waves exist in light.

Creeping waves exist because electromagnetic waves interact with objects and diffraction exist, in particles to bend its trajectory you need a magnetic or electric field, in big objects gravity, but objects are not waves.

Particles by nature a bullet for example can not generate an interference pattern, so basically can not be jammed so if light was a particles you will have perfect darkness in a shadow and once you enter a shadow zone you will not be able to see even in daylight, but light bends around corners, so you can see
At this point, I think everyone in this discussion understands the particles-wave duality of radio wave so I don't think it is necessary for you to re-explain the same thing.
Visible light doesn't curve a full circle around human size object (creeping return) because the wavelength isn't big enough.
A.PNG5.PNG
 

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At this point, I think everyone in this discussion understands the particles-wave duality of radio wave so I don't think it is necessary for you to re-explain the same thing.
Visible light doesn't curve a full circle around human size object (creeping return) because the wavelength isn't big enough.
CREEPING-WAVE DIFFRACTION CONCEPT When a wave is incident upon an opaque object which is large compared to the wavelength, a shadow is formed. However, some radiation penetrates into the shadow region due to diffracted rays as shown in figure 5. (See refs. 12 to 16.) These rays are produced by incident rays which are tangent to the surface of the body. Each tangent ray splits at the point of tangency with one part continuing along the path of the incident ray and the other traveling along a geodesic on the surface of the body. At each following point, it splits again with one part traveling along the geodesic and the other reradiating along a tangent to the geodesic. rays are produced, one of which is reradiated at each point of the geodesic. These waves traveling around the opaque body have been designated as creeping waves introduced first by Franz and Deppermann (ref. 12) for the interpretation of scalar diffraction by circular cylinders and spheres.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19700009872.pdf
On your dally life you see shadows, in fact as i said to you, if light was particles, once you enter in the shadow region you will not be able to see, the radiation penetrates the shadow because light bends around corners,

1571754749558.png

Going back to DSI intake , the DSI intake since it has round bumps, they help the creeping wave


1571755186611.png

see the two DSI intake are pretty round, they will aid the creeping wave


The concept is a flat surface has only one tangent since it is flat, however DSI have huge circular bumps with turning sets of tangents, like any circle, so you see the flat Caret plates go better with stealth, just remember with enough light you can see pretty well in the shadow side, in fact every time you have a lamp in your hand, and it is facing ahead of you can see thanks to creeping waves
 
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Ronny

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CREEPING-WAVE DIFFRACTION CONCEPT When a wave is incident upon an opaque object which is large compared to the wavelength, a shadow is formed. However, some radiation penetrates into the shadow region due to diffracted rays as shown in figure 5. (See refs. 12 to 16.) These rays are produced by incident rays which are tangent to the surface of the body. Each tangent ray splits at the point of tangency with one part continuing along the path of the incident ray and the other traveling along a geodesic on the surface of the body. At each following point, it splits again with one part traveling along the geodesic and the other reradiating along a tangent to the geodesic. rays are produced, one of which is reradiated at each point of the geodesic. These waves traveling around the opaque body have been designated as creeping waves introduced first by Franz and Deppermann (ref. 12) for the interpretation of scalar diffraction by circular cylinders and spheres.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19700009872.pdf
On your dally life you see shadows, in fact as i said to you, if light was particles, once you enter in the shadow region you will not be able to see, the radiation penetrates the shadow because light bends around corners,

View attachment 620522
Ok, I see where your confusion come from.
I didn't say there are no radiation penetrated into the shadow region. I said very specifically: "Visible light doesn't curve a full circle around human size object (creeping return) because the wavelength isn't big enough". That is to help you distinguish between Traveling wave scattering return and Creeping wave return.
The former is generated when the wave travels along the surface of the aircraft hitting some discontinuities and they scatter in many directions
1.pngdf-sos-lowf_3_diffraction.jpg
while the Creeping wave return happens when the traveling wave doesn't strike any discontinuities and not reflected by obstacle when traveling along object surface so it is able to travel a full circle around the object and either interfered instructive or destructive with the specular return. The two phenomena are very closely related but they are not exactly the same thing. The creeping wave return only happen when the wavelength of the radar closer to the size of the object
2.PNG



Going back to DSI intake , the DSI intake since it has round bumps, they help the creeping wave
see the two DSI intake are pretty round, they will aid the creeping wave
The concept is a flat surface has only one tangent since it is flat, however DSI have huge circular bumps with turning sets of tangents, like any circle, so you see the flat Caret plates go better with stealth, just remember with enough light you can see pretty well in the shadow side, in fact every time you have a lamp in your hand, and it is facing ahead of you can see thanks to creeping waves
DSI inlet has a smooth bump with no gaps, so it reduces surface scattering from surface discontinuities and edges compared to a variable inlet. The same reasons more modern stealth aircraft all have blended circular shape unlike the F-117 with flat facets.

design_change1.png2.jpg

Creeping wave return isn't an issue because radar wave curve a full circle into and around the inlet duct won't go back to the illuminate radar.

IDMS-EDMS-Hardware-Configuration-for-F-35.png
 
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pegasus

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Ok, I see where your confusion come from.
I didn't say there are no radiation penetrated into the shadow region. I said very specifically: "Visible light doesn't curve a full circle around human size object (creeping return) because the wavelength isn't big enough". That is to help you distinguish between Traveling wave scattering return and Creeping wave return.
The former is generated when the wave travels along the surface of the aircraft hitting some discontinuities and they scatter in many directions

while the Creeping wave return happens when the traveling wave doesn't strike any discontinuities and not reflected by obstacle when traveling along object surface so it is able to travel a full circle around the object and either interfered instructive or destructive with the specular return. The two phenomena are very closely related but they are not exactly the same thing. The creeping wave return only happen when the wavelength of the radar closer to the size of the object
View attachment 620531



DSI inlet has a smooth bump with no gaps, so it reduces surface scattering from surface discontinuities and edges compared to a variable inlet. The same reasons more modern stealth aircraft all have blended circular shape unlike the F-117 with flat facets.



Creeping wave return isn't an issue because radar wave curve a full circle into and around the inlet duct won't go back to the illuminate radar.
Ronny the illustrations you give do not really show you what is diffraction since basically the illustration can be confused for reflection of electromagnetic waves
1571805660760.png

this illustration shows you what is diffraction, basically it means now the light rays moving in new trajectories

my first comment about the tank can be explained like this
1571805813937.png

the creeping wave exists due to diffraction in fact the nasa document says it all:

CREEPING-WAVE DIFFRACTION CONCEPT When a wave is incident upon an opaque object which is large compared to the wavelength, a shadow is formed. However, some radiation penetrates into the shadow region due to diffracted rays as shown
1571805957166.png


the last illustration tells you why you can detect targets with radars, since the waves do not follow a narrow strait path, but an angular one, thus the document says


These rays are produced by incident rays which are tangent to the surface of the body. Each tangent ray splits at the point of tangency with one part continuing along the path of the incident ray and the other traveling along a geodesic on the surface of the body. At each following point, it splits again with one part traveling along the geodesic and the other reradiating along a tangent to the geodesic. rays are produced, one of which is reradiated at each point of the geodesic.



So basically radars do the same

1571806336338.png


You are thinking DSI ntakes can eliminate creeping waves, no they can not in fact the sharp pointy lip cowls are helping diffraction, stealth is simply a way of reducing RCS using distance, low power density and wave control, no object is invisible none, DSI intakes are not perfect, they are visible, and their bumps are not flat.

But do not get me wrong with the right shaping they make harder to detect by radars at longer ranges, so stealth is no visibility at long ranges aided by shaping and materials, can they reduce their RCS? yes they can, are they visible all the time? yes they are, can they confuse radars? yes they can, can they be undetected if proper shaping materials and tactics are used? yes they can
 
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Ronny

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Ronny the illustrations you give do not really show you what is diffraction since basically the illustration can be confused for reflection of electromagnetic waves
this illustration shows you what is diffraction, basically it means now the light rays moving in new trajectories
my first comment about the tank can be explained like this
the creeping wave exists due to diffraction in fact the nasa document says it all:
CREEPING-WAVE DIFFRACTION CONCEPT When a wave is incident upon an opaque object which is large compared to the wavelength, a shadow is formed. However, some radiation penetrates into the shadow region due to diffracted rays as shown
the last illustration tells you why you can detect targets with radars, since the waves do not follow a narrow strait path, but an angular one, thus the document says
These rays are produced by incident rays which are tangent to the surface of the body. Each tangent ray splits at the point of tangency with one part continuing along the path of the incident ray and the other traveling along a geodesic on the surface of the body. At each following point, it splits again with one part traveling along the geodesic and the other reradiating along a tangent to the geodesic. rays are produced, one of which is reradiated at each point of the geodesic.
So basically radars do the same
Pegasus, yes radar wave can bend around the corner ( diffraction) but like I said how much it can bend around the corner depend on the relative size of wavelength versus the object size. If the wavelength is small compared to the object, such as visible light versus human, there is very little diffraction and there is no creeping wave return. Because the diffraction isn't enough for the wave to go a full circle around the object. Only when the wavelength is very close to the object in size that we have the creeping return effect.
2.PNG
1.PNG



You are thinking DSI ntakes can eliminate creeping waves, no they can not in fact the sharp pointy lip cowls are helping diffraction, stealth is simply a way of reducing RCS using distance, low power density and wave control, no object is invisible none, DSI intakes are not perfect, they are visible, and their bumps are not flat.
I don't think DSI eliminate creeping wave, DSI reduce surface discontinuities diffraction compared to variable inlet because it doesn't have as many gaps and discontinuities. Like I explained, that the same reason B-2, F-35, F-22 doesn't have as many sharp edges as F-117.
Beside, creeping wave effect is often reduced by RAM.
 

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I'm losing the will to live with the argument on how radar works. I may split it off the topic or just delete it.

Shadows are not truly black on earth due to atmospheric scatter effects, its got nothing to do with wave interference. Its not the same on the moon, for example.
 

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Pegasus, yes radar wave can bend around the corner ( diffraction) but like I said how much it can bend around the corner depend on the relative size of wavelength versus the object size. If the wavelength is small compared to the object, such as visible light versus human, there is very little diffraction and there is no creeping wave return. Because the diffraction isn't enough for the wave to go a full circle around the object. Only when the wavelength is very close to the object in size that we have the creeping return effect.
View attachment 620544





I don't think DSI eliminate creeping wave, DSI reduce surface discontinuities diffraction compared to variable inlet because it doesn't have as many gaps and discontinuities. Like I explained, that the same reason B-2, F-35, F-22 doesn't have as many sharp edges as F-117.
Beside, creeping wave effect is often reduced by RAM.
There are important aspects you forget, if you are in a shadow still there is light, the concept of creeping wave is also related to power density, you are comparing an antena to the sun, the sun can fill the whole horizon, basically, no mountains will stop it can not compare, you are giving me an antena with very limited radiation power, remember light is also absorbed by the atmosphere, radar too, it weakens plus the human body is not homogeneous, is not perfectly smooth, there is plenty of diffraction around it, there are creeping waves in human body, creeping waves exist simply because the Huygens principle.


1571825676206.png

in Fig 4 you have a description of concentric circles for long waves and a narrow ray for microwave, however both have the same nature,


DSI intake can deal with creeping waves to an extent like i said to you because at 100 km the atmosphere has absorbed enough power density that it is very weak,.
The caret intake you still do not want to admit, is for higher speeds, so it can keep pressure recovery of 95% at Mach 2, DSI can not do that does not matter how much you want to argue about its smoothness, in aerodynamic terms it will not help you compared to caret variable geometry intakes.


The bump and sharp edges are diffraction sources, you still think the bump by being smooth is invisible to radar, it is not. in fact you have a contradiction F-22 has chines good for eliminating creeping wave, F-15 has round cross section no good for creeping wave, but you say the bump is good


To understand stealth you have to see with distance the radar sensibility and power density go down, that is why stealth works.


If you look a Boeing B-787 aircraft from 5 meters you see lots of details on it, at 100 meters you can not see so many details, at 8km you can not see the eye color of a person looking through one its windows, radar is the same farther the target is, less detail you can see, stealth only is weakening the same signal.

Basically if you consider when an object is very far. an aircraft at 200 km from you, you can not see it, however it is not invisible for a person at 30 meters from it, he or she see it well, but you at 200 km you can not see it, radar is the same.
 
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Ronny

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There are important aspects you forget, if you are in a shadow still there is light, the concept of creeping wave is also related to power density, you are comparing an antena to the sun, the sun can fill the whole horizon, basically, no mountains will stop it can not compare, you are giving me an antena with very limited radiation power, remember light is also absorbed by the atmosphere, radar too, it weakens plus the human body is not homogeneous, is not perfectly smooth, there is plenty of diffraction around it, there are creeping waves in human body, creeping waves exist simply because the Huygens principle.


View attachment 620547

in Fig 4 you have a description of concentric circles for long waves and a narrow ray for microwave, however both have the same nature,


DSI intake can deal with creeping waves to an extent like i said to you because at 100 km the atmosphere has absorbed enough power density that it is very weak
Firstly, there are light behind a mountain because light hitting others object, terrains behind the mountain will scattered back in a wide cone, so some of that will hit the mountain. If you go to the true shadow region, aka the side of the hemisphere not facing the sun, there is no light from the sun. This is particularly evident when planet near the sun have half of their hemisphere at 400-500 degree Celsius and the other half at -150 degree Celsius. If light/ radio wave can always fully curve a whole circle around the object regardless of their size then we would never have radar horizon limit, there will be no night time, and you will always see object around corner. As none of those are possible, we know that the diffraction angle/creeping potency is depending on the wavelength size and the object size. If the wave is too small compare to the object, the diffraction angle is narrow. If the wavelength approach the size of the object, then it start to curve around. There is very good reason, they divide RCS into 3 regions: Optical/Mie/Rayleigh and very low frequency radar are considered better against stealth aircraft.





The caret intake you still do not want to admit, is for higher speeds, so it can keep pressure recovery of 95% at Mach 2, DSI can not do that does not matter how much you want to argue about its smoothness, in aerodynamic terms it will not help you compared to caret variable geometry intakes.
I have never say caret inlet isn't for high speed so please don't strawman my argument.





The bump and sharp edges are diffraction sources, you still think the bump by being smooth is invisible to radar, it is not. in fact you have a contradiction F-22 has chines good for eliminating creeping wave, F-15 has round cross section no good for creeping wave, but you say the bump is good
The angular edge redirect creeping wave so that it less likely to come back to the source. The smooth curve eliminate surface wave scattering. Please distinguish between the surface wave scattering and the creeping wave return.
To mitigate both surface wave scattering and creeping wave return, you want a design that isn't circular or tube like but also doesn't have many sharp edges and discontinuities. Sort of an angular shape with blunt edge. That why F-22, F-35, B-2 doesn't have tube body like B-52, F-16 but they also doesn't have a full facet body like F-117. To further reduce the effect of edge diffraction, their wing leading and trailing edges are treated with RAM.
 

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There are important aspects you forget, if you are in a shadow still there is light, the concept of creeping wave is also related to power density, you are comparing an antena to the sun, the sun can fill the whole horizon, basically, no mountains will stop it can not compare, you are giving me an antena with very limited radiation power, remember light is also absorbed by the atmosphere, radar too, it weakens plus the human body is not homogeneous, is not perfectly smooth, there is plenty of diffraction around it, there are creeping waves in human body, creeping waves exist simply because the Huygens principle.


View attachment 620547

in Fig 4 you have a description of concentric circles for long waves and a narrow ray for microwave, however both have the same nature,


DSI intake can deal with creeping waves to an extent like i said to you because at 100 km the atmosphere has absorbed enough power density that it is very weak
Firstly, there are light behind a mountain because light hitting others object, terrains behind the mountain will scattered back in a wide cone, so some of that will hit the mountain. If you go to the true shadow region, aka the side of the hemisphere not facing the sun, there is no light from the sun. This is particularly evident when planet near the sun have half of their hemisphere at 400-500 degree Celsius and the other half at -150 degree Celsius. If light/ radio wave can always fully curve a whole circle around the object regardless of their size then we would never have radar horizon limit, there will be no night time, and you will always see object around corner. As none of those are possible, we know that the diffraction angle/creeping potency is depending on the wavelength size and the object size. If the wave is too small compare to the object, the diffraction angle is narrow. If the wavelength approach the size of the object, then it start to curve around. There is very good reason, they divide RCS into 3 regions: Optical/Mie/Rayleigh and very low frequency radar are considered better against stealth aircraft.





I have never say caret inlet isn't for high speed so please don't strawman my argument.




The angular edge redirect creeping wave so that it less likely to come back to the source. The smooth curve eliminate surface wave scattering. Please distinguish between the surface wave scattering and the creeping wave return.
To mitigate both surface wave scattering and creeping wave return, you want a design that isn't circular or tube like but also doesn't have many sharp edges and discontinuities. Sort of an angular shape with blunt edge. That why F-22, F-35, B-2 doesn't have tube body like B-52, F-16 but they also doesn't have a full facet body like F-117. To further reduce the effect of edge diffraction, their wing leading and trailing edges are treated with RAM.
Ronny

DSI intakes as you already say it can not compete with a variable geometry intake for speeds beyond 0 km to Mach 2, in fact your average DSI has its best pressure recovery at Mach 1.7, a regular F-14 has an intake with its best pressure recovery at Mach 2.1, so definitively if you have a more complex one like SR-71 the pressure recovery can go to Mach 2.5 easily.

So there is no comparison regardless you say it is more stealth or not, a variable geometry caret will give you better performance but at higher price both in maintenance and stealth.


Now remember this
1571954740583.png
1571957144564.png

when an object is far away from a light source light rays are parallel, when it is close they are divergent, if you place a ball at 1 meter from a lamp the shadow side of the ball has enough light to be very visible, you can stay in the shadow side and it is pretty visible, as the light source is farther the shadow becomes darker, if you see that you will understand stealth, the amount of creeping wave is higher when the light source is closer, but when it is farther, less and less light enters the shadow, stealth is that so chines or trapezoidal shapes reduce radar waves creeping effect, but because it is darker and farther in few words the radar is farther away.

Now if you remember a leopard in Africa can hunt at night, why? remember for us our eyes are not so sensitive, but for a leopard his eyes allow it to hunt at night, in a very dark night that for us will not let us see, so even on earth it is not absolute darkness, so radars need to become as the eyes of a leopard more sensitive to lower power density and more powerful as emitters, but stealth does not mean not visible, it means less visible as the distance grows and such technologies just makes it harder as the distance grows.

remember the eyes of a leopard concentrate light so the beams become convergent, a parabola does the same thing that a retina does to our eyes


1571963061395.png

The DSI makes J-20 a hybrid of F-15 and F-22 to some extent since the flat chines of F-22 are better to deal with creeping waves, both caret and DSI have aerodynamic compromises the caret has a boundary layer diverter but DSI a bump that reminds us of the round cross section of F-15
 
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quellish

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Just remember stealth is not radar invisibility,
Yes, stealth is not invisibility. It is reducing detection range and probability to increase aircraft survivability. Instead of being able to engage you 10 miles away, they can't until you are right on top of them. That is the point.

is lower signature treatment, and improvements in radar technology render stealth useless, diffraction and power density output of radars make stealth useless
Stealth aircraft are already designed to account for diffraction. They have been for a long time, even before there were computational tools.
Modern stealth aircraft have been around for nearly 40 years, yet they are not yet "useless" in the face of improvements in radar technology, wether those improvements are increased power density, better signal processing and software, or bistatic radars.
 

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Ronny
DSI intakes as you already say it can not compete with a variable geometry intake for speeds beyond 0 km to Mach 2
I think it depends, I think variable inlet can be optimized to wider range of speed so generally most of them are better than DSI at high Mach, but I don't think DSI is necessarily worse than all kinds of variable inlets. For example. according to this chart F-4D inlet isn't better than J-10 DSI.
TWUDq.jpg







Now remember this
View attachment 620597

when an object is far away from a light source light rays are parallel, when it is close they are divergent, if you place a ball at 1 meter from a lamp the shadow side of the ball has enough light to be very visible, you can stay in the shadow side and it is pretty visible, as the light source is farther the shadow becomes darker, if you see that you will understand stealth, the amount of creeping wave is higher when the light source is closer, but when it is farther, less and less light enters the shadow, stealth is that so chines or trapezoidal shapes reduce radar waves creeping effect, but because it is darker and farther in few words the radar is farther away.
The fact that wave only curve a whole revolution around the object when they approach the size of the object has nothing to do with whether the source is powerful or not. If your wavelength is too small compare to the object, there will be no creeping wave return regardless of how powerful the source is. Case in point, in an anechoic chamber the emitter is only few meter away from the aircraft. Please don't confuse between creeping wave return and surface wave scattering. In your ball example, the shadow side of the ball could be visible due to backscatter from object behind the ball. If the wave truly creeping a whole circle around the ball, you will be able to see its shadow side from the light side.







Now if you remember a leopard in Africa can hunt at night, why? remember for us our eyes are not so sensitive, but for a leopard his eyes allow it to hunt at night, in a very dark night that for us will not let us see, so even on earth it is not absolute darkness, so radars need to become as the eyes of a leopard more sensitive to lower power density and more powerful as emitters, but stealth does not mean not visible, it means less visible as the distance grows and such technologies just makes it harder as the distance grows.

remember the eyes of a leopard concentrate light so the beams become convergent, a parabola does the same thing that a retina does to our eyes
Leopard can sometimes hunt at night because his eyes are sensitive enough to capture photons from the moon, the stars and not because sunlight curve around the earth. Secondly, no one here ever said stealth is invisible, it really pointless to argue against that.




The DSI makes J-20 a hybrid of F-15 and F-22 to some extent since the flat chines of F-22 are better to deal with creeping waves, both caret and DSI have aerodynamic compromises the caret has a boundary layer diverter but DSI a bump that reminds us of the round cross section of F-15
Creeping wave return are traveling wave that able to travel a whole circle around the object. As long as your object isn't a sphere or cylinder, the effect of creeping wave are already mitigated a lot. F-35 nose isn't a cylinder so it already reduce the effect of creeping wave return. The bumps here help reduce surface wave scattering. Why else do you think among all modern stealth aircraft F-22, F-35, B-2, X-47, RQ-170, MQ-25, none of them have as many sharp facets as the F-117 ?. Pretty much their only sharp edges are at trailing and leading edges but those are treated with RAM

1.PNG
 

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I think it depends, I think variable inlet can be optimized to wider range of speed so generally most of them are better than DSI at high Mach, but I don't think DSI is necessarily worse than all kinds of variable inlets. For example. according to this chart F-4D inlet isn't better than J-10 DSI.
View attachment 620603










Leopard can sometimes hunt at night because his eyes are sensitive enough to capture photons from the moon, the stars and not because sunlight curve around the earth. Secondly, no one here ever said stealth is invisible, it really pointless to argue against that.




[
Creeping wave return are traveling wave that able to travel a whole circle around the object. As long as your object isn't a sphere or cylinder, the effect of creeping wave are already mitigated a lot. F-35 nose isn't a cylinder so it already reduce the effect of creeping wave return. The bumps here help reduce surface wave scattering. Why else do you think among all modern stealth aircraft F-22, F-35, B-2, X-47, RQ-170, MQ-25, none of them have as many sharp facets as the F-117 ?. Pretty much their only sharp edges are at trailing and leading edges but those are treated with RAM

View attachment 620604
the drawing you have of the creeping wave is not accurate, in fact remember the title of the document i gave you

CREEPING-WAVE DIFFRACTION CONCEPT When a wave is incident upon an opaque object which is large compared to the wavelength, a shadow is formed. However, some radiation penetrates into the shadow region due to diffracted rays as shown


they say diffraction, in fact you have to see how they explain it
1571984992248.png
These rays are produced by incident rays which are tangent to the surface of the body. Each tangent ray splits at the point of tangency with one part continuing along the path of the incident ray and the other traveling along a geodesic on the surface of the body. At each following point, it splits again with one part traveling along the geodesic and the other reradiating along a tangent to the geodesic. rays are produced, one of which is reradiated at each point of the geodesic.


It basically due to the curvature of the leading edge, (it has tangents ) you just need to see a graph and you will see the fact a cylinder or sphere has many tangents


1571985274026.png

thus as you can see, a circle has no one, no 360 tangents, it has many thus as the title says CREEPING-WAVE DIFFRACTION CONCEPT is diffraction what causes the creeping wave



Any way you are free to believe diffraction is not the cause, the only thing i can tell you, is DSI intakes are visible, F-22 can be detected at ranges of at least 40-60km by radars on Su-35, at 120 km well it may not be detected.

You insistence on DSI intake might have better performance is not real, as speed grows more boundary layer is ingested, thus you need bleeding mechanical systems

1571985720318.png

there you can see the bleeding system of an F-14, faster speeds also need bypass doors

1571985805920.png


The DSI of J-20 has no mechanical system, no bleeding system why? simple the speeds it manages, if it goes at higher speeds not only more boundary layer will ingest but it will have a mass flow of air that needs to be removed, so no, DSI intakes can not compete if you go from 0 km to more than Mach 2+ , the capture area, throat area and shock ramps are variable because of the speed and some times they need bypass flow.

1571986049201.png
the pointy cowl of X-35 is good for reflection, but not good for diffraction, stealth aircraft always send radar waves back to the radar emitter, but since power is low, well at 100 km the signal might be too weak for a radar to recognize it as a F-22, is like if we try to see details at 100 km, can you see the eye color of a person at 1 km from you? can you see if she has moles at 2000 meters? to do that you need convergent rays. or a parabola

The bump on DSI are not perfect circles they are half cones, by frontal cross section are half circles, good for diffraction but diagonally they are wedges, that are good for reflection away from the radar, on a head to head approach they reduce RCS, but not from the sides, chines and flat sidewalls are good for the sides, so they are good for reflection away from the radar

1571986992411.png

a wedge has several facets like F-117 to send energy away from the radar, by wedge i mean they have an acute shape a pointy parabola or, consider the DSI`s bump on 3 axis, X and Y axis are a semi circle but Z and Y axis are a parabola


1571987959841.png

so the parabola has an angle of reflection that sends energy away from the radar ahead of the aircraft due to this simple formula

The angle of reflection
of a ray or beam is the angle measured from the reflected ray to the surface normal. From the law of reflection,
, where
is the angle of incidence.
is measured between the ray and a line normal to the surface that intersects the surface at the same point as the ray.

http://140.177.205.24/physics/AngleofReflection.html
 
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Ronny

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the drawing you have of the creeping wave is not accurate, in fact remember the title of the document i gave you
CREEPING-WAVE DIFFRACTION CONCEPT When a wave is incident upon an opaque object which is large compared to the wavelength, a shadow is formed. However, some radiation penetrates into the shadow region due to diffracted rays as shown
they say diffraction, in fact you have to see how they explain it
These rays are produced by incident rays which are tangent to the surface of the body. Each tangent ray splits at the point of tangency with one part continuing along the path of the incident ray and the other traveling along a geodesic on the surface of the body. At each following point, it splits again with one part traveling along the geodesic and the other reradiating along a tangent to the geodesic. rays are produced, one of which is reradiated at each point of the geodesic.
It basically due to the curvature of the leading edge, (it has tangents ) you just need to see a graph and you will see the fact a cylinder or sphere has many tangents
View attachment 620609
thus as you can see, a circle has no one, no 360 tangents, it has many thus as the title says CREEPING-WAVE DIFFRACTION CONCEPT is diffraction what causes the creeping wave
Any way you are free to believe diffraction is not the cause
When did I ever say diffraction is not the cause for creeping wave? I only explain one thing and one thing only to you, how much wave can diffract into shadow region depend on its wavelength size compared to the object. If the wavelength is too small compared to the object, then the effect of diffraction is minimal and there is no creeping wave return. So just because creeping wave return is the result of diffraction doesn't mean all diffraction will generate creeping wave return. Why else do you think they have to divide RCS of an object into 3 separate regions to calculate: Optical/Mie/Rayleigh?. Why else do you think RCS of a sphere only fluctuated significantly when the wavelength approaches its radius?. Why else do you think the double-slit experiment is done with a slit instead of a large gap?. Why else do you think very low frequency radar is considered better against stealth aircraft?. All the question have the same answer. The amount of diffraction depending on the size of object versus the wavelength. To have creeping wave return effect, the illuminating wave must have wavelength similar to object size.
1.PNGRCS2.PNG

rcs.PNG




the only thing i can tell you, is DSI intakes are visible, F-22 can be detected at ranges of at least 40-60km by radars on Su-35
If that was possible there is no need for anti stealth radar. Any random AEW&C or SAM radar will detect stealth aircraft from 300-400 km because Su-35's radar even though strong, still pitifully weak compared to ground radar


You insistence on DSI intake might have better performance is not real, as speed grows more boundary layer is ingested, thus you need bleeding mechanical systems
there you can see the bleeding system of an F-14, faster speeds also need bypass doors
The DSI of J-20 has no mechanical system, no bleeding system why? simple the speeds it manages, if it goes at higher speeds not only more boundary layer will ingest but it will have a mass flow of air that needs to be removed, so no, DSI intakes can not compete if you go from 0 km to more than Mach 2+ , the capture area, throat area and shock ramps are variable because of the speed and some times they need bypass flow.
When did I ever say J-10 DSI is better than F-14 or SR-71 inlet at high speed?
I said it is better than F-4D based on the chart.






the pointy cowl of X-35 is good for reflection, but not good for diffraction, stealth aircraft always send radar waves back to the radar emitter, but since power is low, well at 100 km the signal might be too weak for a radar to recognize it as a F-22, is like if we try to see details at 100 km, can you see the eye color of a person at 1 km from you? can you see if she has moles at 2000 meters? to do that you need convergent rays. or a parabola
The bump on DSI are not perfect circles they are cones frontally by frontal cross section are half circles, good for diffraction but diagonally they are wedges, that are good for reflection, on a head to head approach they reduce RCS, but not from the sides, chines are good for the sides, so they are good for reflection away from the radar

a wedge has several facets like F-117 to send energy away from the radar, by wedge i mean they have an acute shape a pointy parabola or, consider 3 axis, X and Y axis are a semi circle but Z and Y axis are a parabola

so the have an angle of reflection that sends energy away from the radar ahead of the aircraft due to this simple formula
The angle of reflection
of a ray or beam is the angle measured from the reflected ray to the surface normal. From the law of reflection,
, where
is the angle of incidence.
is measured between the ray and a line normal to the surface that intersects the surface at the same point as the ray.

http://140.177.205.24/physics/AngleofReflection.html
The DSI smooth cowl on F-35 has no gaps unlike a variable inlet, so DSI minimizes the amount of scattering from surface traveling wave. The curvature mean wave can curve/diffract around it easier. But the cowl is not a sphere, when the surface wave curve/diffract around it, the do not make a full circle back to the radar, they go into the inlet instead. The internal of the inlet will scatter the wave inside multiple time, with each bounce further reduce the wave strength when it hit the RAM surface
F35B STOVL.jpg
 

pegasus

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When did I ever say diffraction is not the cause for creeping wave? I only explain one thing and one thing only to you, how much wave can diffract into shadow region depend on its wavelength size compared to the object. If the wavelength is too small compared to the object, then the effect of diffraction is minimal and there is no creeping wave return. So just because creeping wave return is the result of diffraction doesn't mean all diffraction will generate creeping wave return. Why else do you think they have to divide RCS of an object into 3 separate regions to calculate: Optical/Mie/Rayleigh?. Why else do you think RCS of a sphere only fluctuated significantly when the wavelength approaches its radius?. Why else do you think the double-slit experiment is done with a slit instead of a large gap?. Why else do you think very low frequency radar is considered better against stealth aircraft?. All the question have the same answer. The amount of diffraction depending on the size of object versus the wavelength. To have creeping wave return effect, the illuminating wave must have wavelength similar to object size.





When did I ever say J-10 DSI is better than F-14 or SR-71 inlet at high speed?
I said it is better than F-4D based on the chart.







The DSI smooth cowl on F-35 has no gaps unlike a variable inlet, so DSI minimizes the amount of scattering from surface traveling wave. The curvature mean wave can curve/diffract around it easier. But the cowl is not a sphere, when the surface wave curve/diffract around it, the do not make a full circle back to the radar, they go into the inlet instead. The internal of the inlet will scatter the wave inside multiple time, with each bounce further reduce the wave strength when it hit the RAM surface
View attachment 620623
Ronny ask you self this


With light it is possible to see the intake bump, light is a shorter wave length than the wavelengths used by radar, your eyes can see the bump, you have no problem, now the problem with these theoretical graphs or concept you are using is you are not using more practical examples with light, the creeping wave exists simply because at each and every new tangent, light is diffracting, in fact splitting into new directions every time it moves from one tangent to the next tangent in the 180 degrees of shadow of a cylinder

1572010244646.png

Your analogy of wavelengths does not take into account, any electromagnetic wave will diffract, it will enter into the shadow zone, all this stealth concepts work only because power density is very low.

Now at night as you can see is very hard to see details, many details of F-35 have disappeared from our eyes

1572010840377.png

now see, you are seeing a F-35, the fuselage does not emit light but the engine does, you now can see why power density is important, the engine has high power density, emmits lots of light, the rest of the fuselage emits almost no light
1572011020476.png


Radar is the same, lots of light, you see the bump, easily you can see is round, no light it becomes invisible.


Stealth masking just use some basic laws to help low power density reflection to get more invisible

for a radar close to the F-35 the inlet is as visible as the next picture, far from it, it is like the F-35 at night
1572011369024.png
now at night the pilot has LCD screens with light but from the previous pictures you can not see the light they emit at night and from far away

1572012236013.png thus power density plays the biggest role in stealth
 
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icyplanetnhc

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Why do some still insist on using analogies from the visual spectrum for radar behavior, considering the orders of magnitude difference in wavelength?
 

RanulfC

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Why do some still insist on using analogies from the visual spectrum for radar behavior, considering the orders of magnitude difference in wavelength?
Because it is easier to illustrate and relate and MOST people will understand it a bit better that way.

Having two experts "vigorously discuss" (argue :) ) the mechanics while amusing to watch/listen to did not in fact enhance my knowledge any faster of the subject which also didn't help me pass the next test to move on in studying the subject :)

Randy
 

Fluff

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Fortunately big liz sent me to her second school of technical training, hence emboldened I shall try to enter the fray.....

Stealth-cautious and surreptitious action or movement.

The aim of stealth is, much the same as for camouflage.

In a perfect world camo will mean you, your tank, your aircraft will not be detected, while you complete your destructive mission.

In a less than perfect world, it will delay your detection, thus minimising the time for the enemy to respond. Increasing the probability of success, and survival.

A few comments on the points made.

Stealth can be detected with a big enough radar. True. Assuming we are in a shooting war, how long do you think your huge super doper radar is going to have before it eats a missile, either emission or gps guided, as huge radars don’t move much, except ship based. Alternatively I will simply knock out your super huge power station.

‘Passive radars’ this came up on another site, germans tracking f35 in peacetime. Upon looking at the radar companies website, it becomes apparent it needed tv, fm radio or similar transmitters operating, and mapped to the detector. Again in a hot war your enemy isn’t going to let you keep transmitting tv, it’s not a human right. The system doesn’t work from phone masts etc.

You can fly here, if your over my city we will see you, etc.

Any military flight, using a stealth aircraft, in a hostile- meaning peer or near peer, is going to be planned ‘to death’. It’s probably already planned. I’m not going to zoom in with my f35 until I have zapped as much of your radars, tv transmitters, power stations etc as I can.

Then I’m going to have stand off jamming, drones, etc, and my manned aircraft is only going to get close enough to launch its guided weapon.

Pretty unlikely I’m coming over your city, with my f35.

F22 can be detected by su35- at 40km. Uhu, which means f22 can detect the su35 ( because his radar is emitting) at maybe 160kms, so he changes course and avoids detection, thus completing his mission to destroy the su35 base fuel dump. I know which aircraft and force I would sign up to.

There’s my two peneth worth.
 

pegasus

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F22 can be detected by su35- at 40km. Uhu, which means f22 can detect the su35 ( because his radar is emitting) at maybe 160kms, so he changes course and avoids detection, thus completing his mission to destroy the su35 base fuel dump. I know which aircraft and force I would sign up to.

There’s my two peneth worth.
I agree with you totally, however the Su-35 and Su-57 are based upon speed and manoeuvrability.


the DSI intake is for lower speeds, speeds of Mach 1.7 while the Russian patent claims Su-57 has an intake for speeds up to Mach 3.


The six generation fighters are ought to have less aerodynamic controls, BVR missiles do not have a kill rate of 100% specially if the aircraft firing them can not recognize if the target is an authentic friend or foe.


What i mean is Su-57 is designed to supercruise very likely at high speeds up to Mach 1.8 and it has very likely top speeds of Mach 2.4, if materials allow it.

What are the chances F-22 will surprise a Su-57? in my opinion BVR missiles are limited in number on 5th generation aircraft, I think 6 BVR AAM will not hit 100% of the time and these aircraft will carry 2 short range AAM, in my opinion these aircraft either use speed and go back after firing their BVR missiles and go home just keeping the 2 short range in the case they need them.


So then is why the caret intake of Su-57 will allow better acceleration and faster speeds than using DSI






I agree with Ronny that at lower speeds the DSI has more practicality, simplicity, so for a lower speed aircraft like F-35 remain unseen will be more important than for Su-35 or Su-57, Stealth needs always speed, because the stealth aircraft needs to enter and exit the area where it can be detected quickly to minimize loses.


J-20 also must fly at around Mach 1.6, and the porous intake holes located in the intake cowl very likely are ways to bleed boundary layer and very likely increase pressure recovery and allow it higher speeds of Mach 1.8 or mach 2, but i do not think it will be as efficient as PAKFA aka Su-57, thus i think DSI suffer limitations in speed that force F-35 or J-20 to remain unseen longer than fighters like Su-57


The diverterless supersonic inlet (DSI) of the Lockheed Martin joint strike fighter (JSF), which operates mostly at transonic speeds, has been designed taking whatever is mentioned above into enough account. Fundamental researches on this inlet configuration have been continued since the mid-1990s.
The inlet cowl lips are so designed as to allow most of boundary layer flow to spill out of the aft notch. The DSI structure complexity has been greatly reduced by the removal of moving parts, a boundary layer diverter and a bleed or bypass system thus decreasing the aircraft’s empty weight, production cost, and requirements of maintenance-supporting equipment[1-2].

the effects of the free stream Mach number on the mass flow coefficient and total pressure recovery when D = 0º and E = 0º. As the free stream Mach number increases, the mass flow coefficient decreases, and, after reaching the minimum at Mach number 1.000, it increases. Fig.7 also shows that the total pressure rises and remains constant when the free stream Mach number is up from 0.600 to 1.000, and, afterwards, drops sharply while the free stream Mach number approaches the supersonic.

4 Conclusions A wind-tunnel test of a ventral diverterless high offset S-shaped inlet has been carried out to investigate the aerodynamic characteristics at transonic speeds. Some conclusions can be drawn as follows: (1) There is a large region of low total pressure at the lower part of the inlet exit caused by the counter-rotating vortices formed at the second turn of the S-shaped duct. (2) The performances of the inlet reach almost the highest at Mach number 1.000. This renders the propulsion system able to work with high efficiency in terms of aerodynamics. (3) As the mass flow coefficient increases, the total pressure recovery decreases; the distortion increases at Ma0 = 0.850, but fluctuates at Ma0 = 1.000 and 1.534. (4) The total pressure recovery increases slowly first, and then remains unchanged as the Mach number rises from 0.600 to 1.000. (5) The performances of the inlet are generally insensitive to angles of attack from –4º to 9.4º and yaw angles from 0º to 8º at Mach number 0.850, and angles of attack from –2º to 6º and yaw angles from 0º to 5º at Mach number 1.534.

A Ventral Diverterless High Offset S-shaped Inlet at Transonic Speeds Xie Wenzhong*, Guo Rongwei College of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China Received 13 September 2007; accepted 18 December 2007


Boundary-layer bleed in supersonic inlets is typically used to avoid boundary layer flow separation f_m adverse shock-wave/boundary-layer interactions and subsequent total pressure loss in the subsonic diffuser and to stabilize the normal shock


https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19950013353.pdf
 
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Ronny

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Ronny ask you self this
With light it is possible to see the intake bump, light is a shorter wave length than the wavelengths used by radar, your eyes can see the bump, you have no problem, now the problem with these theoretical graphs or concept you are using is you are not using more practical examples with light, the creeping wave exists simply because at each and every new tangent, light is diffracting, in fact splitting into new directions every time it moves from one tangent to the next tangent in the 180 degrees of shadow of a cylinder
If your theory is correct or in other words if wave can always diffracting a whole circle around the object regardless of the wavelength size compare to the object, then you will be able to see with your eye not just the DSI cowl but also what behind it. You will actually always able to see an object behind a corner. And when you cover the sun with a soccer ball 1 cm from your eye, you will still see the sun. None of that is possible.


any electromagnetic wave will diffract, it will enter into the shadow zone
[/QUOTE]
Yes but how much it can enter the shadow zone depend on the size of the wavelength versus the size of the object.
Seriously though, just think about all the questions I mentioned earlier
Why they have to divide RCS of an object into 3 separate regions to calculate: Optical/Mie/Rayleigh?.
Why the double-slit experiment is done with slits instead of a large gap?.
Why very low-frequency radar is considered better against stealth aircraft than high frequency radar?.

Look at this measured data why RCS of a sphere only fluctuated significantly when the wavelength approaches its radius?
156299-43555c4c8cd95f327ac2b37305877fcf.png
 

pegasus

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[
If your theory is correct or in other words if wave can always diffracting a whole circle around the object regardless of the wavelength size compare to the object, then you will be able to see with your eye not just the DSI cowl but also what behind it. You will actually always able to see an object behind a corner. And when you cover the sun with a soccer ball 1 cm from your eye, you will still see the sun. None of that is possible.



Yes but how much it can enter the shadow zone depend on the size of the wavelength versus the size of the object.
Seriously though, just think about all the questions I mentioned earlier
Why they have to divide RCS of an object into 3 separate regions to calculate: Optical/Mie/Rayleigh?.
Why the double-slit experiment is done with slits instead of a large gap?.
Why very low-frequency radar is considered better against stealth aircraft than high frequency radar?.

Look at this measured data why RCS of a sphere only fluctuated significantly when the wavelength approaches its radius?
Ronny you did not read well the nasa document? see what it says

CREEPING-WAVE DIFFRACTION CONCEPT When a wave is incident upon an opaque object which is large compared to the wavelength, a shadow is formed. However, some radiation penetrates into the shadow region due to diffracted rays as shown in figure 5. (See refs. 12 to 16.) These rays are produced by incident rays which are tangent to the surface of the body. Each tangent ray splits at the point of tangency with one part continuing along the path of the incident ray and the other traveling along a geodesic on the surface of the body. At each following point, it splits again with one part traveling along the geodesic and the other reradiating along a tangent to the geodesic. rays are produced, one of which is reradiated at each point of the geodesic. These waves traveling around the opaque body have been designated as creeping waves introduced first by Franz and Deppermann (ref. 12) for the interpretation of scalar diffraction by circular cylinders and spheres

The light as well radar frequencies and wavelength do fill those requirements

1572065063370.png

1572065178453.png
1572065478904.png
1572065510520.png
see what the Chinese document says about DSI intake like the one of J-10 but also applies to J-20:


the effects of the free stream Mach number on the mass flow coefficient and total pressure recovery when D = 0º and E = 0º. As the free stream Mach number increases, the mass flow coefficient decreases, and, after reaching the minimum at Mach number 1.000, it increases. Fig.7 also shows that the total pressure rises and remains constant when the free stream Mach number is up from 0.600 to 1.000, and, afterwards, drops sharply while the free stream Mach number approaches the supersonic

4 Conclusions A wind-tunnel test of a ventral diverterless high offset S-shaped inlet has been carried out to investigate the aerodynamic characteristics at transonic speeds. Some conclusions can be drawn as follows: (1) There is a large region of low total pressure at the lower part of the inlet exit caused by the counter-rotating vortices formed at the second turn of the S-shaped duct. (2) The performances of the inlet reach almost the highest at Mach number 1.000. This renders the propulsion system able to work with high efficiency in terms of aerodynamics. (3) As the mass flow coefficient increases, the total pressure recovery decreases; the distortion increases at Ma0 = 0.850, but fluctuates at Ma0 = 1.000 and 1.534. (4) The total pressure recovery increases slowly first, and then remains unchanged as the Mach number rises from 0.600 to 1.000. (5) The performances of the inlet are generally insensitive to angles of attack from –4º to 9.4º and yaw angles from 0º to 8º at Mach number 0.850, and angles of attack from –2º to 6º and yaw angles from 0º to 5º at Mach number 1.534.

A Ventral Diverterless High Offset S-shaped Inlet at Transonic Speeds Xie Wenzhong*, Guo Rongwei College of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China Received 13 September 2007; accepted 18 December 2007


Boundary-layer bleed in supersonic inlets is typically used to avoid boundary layer flow separation f_m adverse shock-wave/boundary-layer interactions and subsequent total pressure loss in the subsonic diffuser and to stabilize the normal shock


1572066423605.png

1572067430955.png

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19950013353.pdf

Basically the DSI intake loses pressure recovery, becoming less capable as the intake goes supersonic
 
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quellish

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radars by increasing the power density will see stealth aircraft well.
No, they will not. You can't change the laws of physics.
Double the power output and you get a less than 20% increase in detection range under ideal conditions.

RCS is the most important variable in the radar range equation. The aircraft always has the advantage.
 

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No, they will not. You can't change the laws of physics.
Double the power output and you get a less than 20% increase in detection range under ideal conditions.

RCS is the most important variable in the radar range equation. The aircraft always has the advantage.
1572082746337.png


The equation does not say that exactly because as any equation everything depends in the values you input on it

it says


1572083115138.png

Radar range equation for search (S/N = signal to noise ratio) • S/N of target can be enhanced by – Higher transmitted power Pav – Lower system losses L – Minimize system temperature T The design of radar transmitter/receiver affects these three parameters directly Pav = average power Αe = antenna area ts = scan time for Ω Pav = average power σ = radar cross section Ω = solid angle searched R = target range Ts = system temperature L = system loss
 
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kaiserd

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No disrespect but some contributors comments are still coming across as Russian-fan-boy ideas but now dressed up with extensive and somewhat pseudoscientific trappings. This may not be any intended or recognised by these contributors.
Why does everything seem to come back to the allegedly weakness of “stealth” versus “more powerful” radars, and the alleged superiority of variable inlets over DSI (and an alleged major flaws of DSIs)?
All of which nicely and conveniently tallies back to and with current Russian approaches versus everyone else’s (US, China etc.)
No offence is intended; I‘d be equally questioning of such conveniences if a contributor was doing the same re: US, UK etc.
(Other contributors can attest I have done do.)
 

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It is a very narrow discussion, as I was trying to point out, theoretical super radars won’t last long. You go to war with what you have. I’m doubtful intake design will have a major impact upon the outcome of future conflicts, I’m also of the opinion that us, Russia, China, nato are all too powerful to have a conflict, it will all be proxy, flip flop enemies, or religious strife, where one persons stealth aircraft will be used as safe bomb trucks.
 

pegasus

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No disrespect but some contributors comments are still coming across as Russian-fan-boy ideas but now dressed up with extensive and somewhat pseudoscientific trappings. This may not be any intended or recognised by these contributors.
Why does everything seem to come back to the allegedly weakness of “stealth” versus “more powerful” radars, and the alleged superiority of variable inlets over DSI (and an alleged major flaws of DSIs)?
All of which nicely and conveniently tallies back to and with current Russian approaches versus everyone else’s (US, China etc.)
No offence is intended; I‘d be equally questioning of such conveniences if a contributor was doing the same re: US, UK etc.
(Other contributors can attest I have done do.)
Rezonans-NE
Stealth air target early warning radar
Mission
The Rezonans-NE very high frequency counter-stealth early warning phased-array radar is designed to effectively detect a wide range of current and future air targets, including low-observable cruise and ballistic missiles, hypersonic aerial vehicles, as well as stealthy ones, in severe electronic countermeasures (ECM) and clutter environment.
Tasks
  • detect and track a wide range of air targets at long ranges, including small and stealthy ones;
  • automatically determine the location and motion parameters of air targets as well as classify them;
  • automatically provide designations to weapon systems;
  • generate and send information about the tracked targets for taking operational decisions;
  • analyze the ECM situation and automatically adjust to the actual ECM conditions.
http://roe.ru/eng/catalog/air-defence-systems/radar-and-electro-optical-equipment-for-air-target-detection/rezonans-ne/
 

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It is a very narrow discussion, as I was trying to point out, theoretical super radars won’t last long. You go to war with what you have. I’m doubtful intake design will have a major impact upon the outcome of future conflicts, I’m also of the opinion that us, Russia, China, nato are all too powerful to have a conflict, it will all be proxy, flip flop enemies, or religious strife, where one persons stealth aircraft will be used as safe bomb trucks.
Nebo-SVU
Surveillance radar surface surveillance standby conditions 2D Radar
The Nebo-SVU radar is designed for use in Air Defence forces and provides:
  • automatic detection, positioning, and tracking of a wide range of current air targets, including ballistic and low-signature stealthy targets;
  • identification friend-or-foe interrogation;
  • location of active jammers;
  • target identification when operating as part of both advanced automated Air Defence command and control systems and non-automated control systems.
Radar design features:
  • an active electronically scanned array (AESA) with analog-to-digital data signal conversion in each array row;
Fighter-type target detection range (RCS=2,5 km²), at the flight altitude of, not less than, km:
500 m 60
10000 m 270
20000 m 360
 
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