Posts evicted from Sukhoi T-75 LTS (CheckMate) topic

[quellish]

I also am confused about your argument. You’re saying all composites have poor conductivity hence radars can ‘see’ through to “landing gear” “electronics” ect. Well clearly that is false, if that was the case there would be no point in making low observable aircraft since electromagnetic energy would just penetrate its outer skin anyways.

Hmmm.. false?



This is a ISAR RCS diagnostic image of an all-composite aircraft in flight.



You can easily see that the radar does not "see" the outer mold line. Instead it sees the landing gear, avionics, pushrods, etc. inside the aircraft as major scattering sources. Radar sees right through the "composites". The stuff inside the aircraft become the source of most of the RCS.

 

[Arjen]

@quellish I raised exactly that point earlier, but it apparently didn't make an impression on @Galaxy
Ho hum.
@quellish Thank you for the ISAR RCS diagnostic image!

 

[Galaxy]

This is because you can always reflect more energy away than you can possibly absorb in a material. Absorbers have physical and practical limitations. Prior to the early 1970s signature reduction techniques had focused primarily on using absorbers, with limited effectiveness.

Technically you’re wrong. General rule of thumb is the majority of stealth is achieved by shaping. For instance a F-35 can’t afford to have thick composites in the wings due to limitations in space and weight. However, larger flying wing designs can afford to use more composites and thicker composites. Some RAM can absorb over 90% of electromagnetic energy in certain frequencies.

https://onlinelibrary.wiley.com/doi/full/10.1002/advs.202303104

“For example, Zhao et al. have explored the possibility of using CNTs as RAMs.[ 44 ] They observed when the CNT content reaches 10 wt%; the epoxy‐based composites containing CNTs achieved a reflection loss (RL) below –10 dB (90% absorption) over 3.0 GHz in the range of 10.1–13.1 GHz, and the maximum value was –22.89 dB at 11.4 GHz.”

Again, these discontinuities are a known and well-solved problem. As far as I am aware there is no one trying to design an aircraft to minimize "seams" as part of RCS reduction, at least not in the way you appear to be describing where they would be using composites, whatever to make larger parts so there are fewer "seams".

Part of the reason for the one peace canopy is to reduce the bow which has multiple discontinuities. Ideally the surface should be as smooth as possible. When I worked on a DARPA projects the superstructure of the LO design was nearly one piece minus the access hatched and we used all composites meant to absorb as much radar as possible. Just for fun let’s pull up something from Chat GDP.




“Engineers have said that the move from aluminum skins to large-area composite skins made it possible to reduce radar returns by eliminating “fastener farms” and “panel seams” that plagued older designs.

• Example: The F-35’s fuselage and wing skins are among the largest composite structures ever flown specifically to minimize panel boundaries.”

“Northrop Grumman (B-2 Spirit):
Public discussions mention that its smooth, blended wing made of large graphite/epoxy composite skins is a key to keeping its radar signature low.”

As far as the F-117, the F-117 used very little composite components. It was an aluminium aircraft. The use of composites was limited to the tails and leading edges.

Wrong, I can clearly tell that there is heavy use of composites in the wood wing and other areas.

Discontinuities certainly do contribute to RCS, however your statements about using large composite parts to minimize physical seams between components have very little to do with reducing RCS and would (without additional treatment) increase RCS through the very electrical discontinuities that actually do contribute to RCS.

This is a contradiction and a discombobulated argument. Large panels with less seam, discontinuities, imperfections, ect do reduce radar cross section. That is a fact, be it on a stealth aircraft or just some panel or object being tested in an anechoic chamber. What is additional “treatment” panel alignment or serrations? Those are of course necessary however its always better to reduce those “treatments” when possible. It’s better to have one large smooth fuselage as opposed to a fuselage made of many smaller pieces regardless if those pieces are serrated.

Oh no, I am very much arguing the science and engineering. I seem to be one of the only ones.



Statements like this, while ignoring physics, do not help your case.

Thanks for sharing your opinion that has very little to do with reality. I actually posted scientific articles disproving your claims and worked on LO projects. I wasn’t anyone special but I have extensive knowledge in composites and spoke to DARPA engineers regarding composites.

 

[Galaxy]

Hmmm.. false?

View attachment 781896

This is a ISAR RCS diagnostic image of an all-composite aircraft in flight.

View attachment 781897

You can easily see that the radar does not "see" the outer mold line. Instead it sees the landing gear, avionics, pushrods, etc. inside the aircraft as major scattering sources. Radar sees right through the "composites". The stuff inside the aircraft become the source of most of the RCS.

This is just a bad argument. Composites vary wildly in performance when it comes to absorption of electromagnetic energy. What composites is that aircraft made from? Fiber glass? In that case this is just an intellectually dishonest. Is that aircraft made of carbon fiber? Carbon nanotubes? What thickness? What is the inter structure made from? What frequencies are used? What aperture? What range? This image is also a top view image, meaning the radar is perpendicular to the aircraft. Meaning it will have the strongest radar reflections meaning virtually none of the energy will be redirected. Moreover, the incident angle matters a lot.

A half inch composite panel or surface at 0 degrees will be 0.5 inches thick. However at
85 degrees it will be over 5.7 inches thick or an increase of over 1000% inches thickness. Tilt that aircraft at a different angle and the radar would have to penetrate the same materials at a 1000% greater depth in each direction which would degrade the electromagnetic energy significantly.

To put it in to more perspective that 0.5 inch material at o degrees would be 5.7 inches at 85 degrees, once it would reach landing gear or other components the energy would scatter in many directions and off many objects and only then would the remaining energy have to penetrate back another 5.7 inches for a total of over 11.4 inches! This is however, not the most relevant point. The materials, thickness, frequency, aperture, ect all matter just as much.

 

[flateric]

I thought it was known since early 90s that "The F-117A had a conventional basic structure primarily of aluminum, except for the aft fuselage, which was constructed from titanium. Nonstructural radar absorbent material (RAM) was applied over the metal skin, except the tailfins. They were originally aluminum but later were replaced with a new thermoplastic design."

Have Blue and the F-117A: Evolution of the "Stealth Fighter"
David C. Aronstein and Albert C. Piccirillo
AIAA Library of Flight 1997

Well, you can clearly see that wings are Al alloys at any F-117A recently stripped from RAM for museum transfer. Earlier F-117A RAM used was sheet-like structure glued to surface. That's what you see burned on Zelko's aircraft remains.

 

[Galaxy]

@quellish I raised exactly that point earlier, but it apparently didn't make an impression on @Galaxy
Ho hum.
@quellish Thank you for the ISAR RCS diagnostic image!

You apparently also didn’t ask basic questions. Again as I mentioned earlier. Give us the types of composites used in the test. That makes all the difference, what was the thickness, density, inner structure, what frequencies were used? What aperture? Did you even take into account the 0 incident angle and how, for instance, at 85 degrees that radar would have to penetrate 1000% more depth of material in one direction only? Both ways that would be over 2180% increase in depth the radar would have to penetrate. Talk about being intellectually dishonest and not having any critical thinking skills.

Look it’s an ISAR image. You can’t see any engines or anything inside the aircraft. It’s almost like materials, thickness, incident angle, frequency, ect matter. Using the right materials, frequencies, ect you can manipulate results to show whatever you desire.

 

[quellish]

Technically you’re wrong. General rule of thumb is the majority of stealth is achieved by shaping. For instance a F-35 can’t afford to have thick composites in the wings due to limitations in space and weight.

That "the majority of stealth is achieved by shaping" is exactly what I stated.
The F-35 does have "thick" composites in the wings.

Some RAM can absorb over 90% of electromagnetic energy in certain frequencies.

90%. Your position is that this is significant, is that correct?

Wrong, I can clearly tell that there is heavy use of composites in the wood wing and other areas.

View attachment 781882

Can you describe exactly where in that photo you see the use of composites?

What is additional “treatment” panel alignment or serrations? Those are of course necessary however its always better to reduce those “treatments” when possible. It’s better to have one large smooth fuselage as opposed to a fuselage made of many smaller pieces regardless if those pieces are serrated.

Additional treatment? Treating the changes in conductivity and impedance using fillers, coatings, graded impedance, etc.

Serrations solve a very different problem than what we are discussing here. I have no idea why serrations are being brought up.

 

[quellish]

This is just a bad argument. Composites vary wildly in performance when it comes to absorption of electromagnetic energy.

Then how can you possibly assert that "composites reduce RCS", which is what you have been arguing throughout this thread? Now your position seems to be that the use of composites reduces RCS, unless it doesn't, because there are all kinds of different composites.

What composites is that aircraft made from? Fiber glass?

Carbon fiber, Kevlar, plastic, glass fiber.

What is the inter structure made from? What frequencies are used? What aperture? What range? This image is also a top view image, meaning the radar is perpendicular to the aircraft. Meaning it will have the strongest radar reflections meaning virtually none of the energy will be redirected. Moreover, the incident angle matters a lot.

Inner structure? The same composites. It is an all-composite aircraft.
X-band.

The image is presented in the top view but the data was collected from the frontal aspect. The ISAR aircraft was in front of the target.

Look it’s an ISAR image. You can’t see any engines or anything inside the aircraft. It’s almost like materials, thickness, incident angle, frequency, ect matter. Using the right materials, frequencies, ect you can manipulate results to show whatever you desire.

Actually, you can see the landing gear, hinges, control rods, cockpit, avionics, engines, etc. very easily.

 

[Galaxy]

That "the majority of stealth is achieved by shaping" is exactly what I stated.
The F-35 does have "thick" composites in the wings.

Shaping is the primary means to reduce RCS however some composites are extremely advanced and can absorb 90% or more electromagnetic radiation. Fighters are limited to how thick of composites they use due to limited volume and the detrimental impact weight would have on maneuverability and range. Bigger bombers have more room for error.

90%. Your position is that this is significant, is that correct?

90% is a significant reduction. Even 40% or 60% would be significant.

Can you describe exactly where in that photo you see the use of composites?

That brownish yellow looks like some type resin based composite, looking closer the sides of the flaps look like they are made of honeycomb type materials and the edges around the wings look split similar to how damaged resin based composites would look. Although it could also just be split paint or deformed alloys.

Additional treatment? Treating the changes in conductivity and impedance using fillers, coatings, graded impedance, etc.

Serrations solve a very different problem than what we are discussing here. I have no idea why serrations are being brought up.

Why would a surface with multiple joints and seams be considered as good or better than a smooth surface with no discontinuities? Clearly the latter would be a better solution because there would be less surface disruptions, less maintenance, less cost, less weight ect. Why on earth would I ever want fillers and the cost weight, maintenance, and cracking associated with it when I can just manufacture one smooth large surface?

 

[quellish]

Shaping is the primary means to reduce RCS however some composites are extremely advanced and can absorb 90% or more electromagnetic radiation. Fighters are limited to how thick of composites they use due to limited volume and the detrimental impact weight would have on maneuverability and range. Bigger bombers have more room for error.

Fighters use composites extensively. The F-35 and F-22 are two examples. Composites are often used for weight savings - not to add weight as you assert.

90% is a significant reduction. Even 40% or 60% would be significant.

"90%" is about a 10db reduction. I am sure you are familiar with the radar range equation. A "90%" reduction is not significant.

That brownish yellow looks like some type resin based composite, looking closer the sides of the flaps look like they are made of honeycomb type materials and the edges around the wings look split similar to how damaged resin based composites would look. Although it could also just be split paint or deformed alloys.

So you're not actually certain you see the use of composites? Clearly the primary material of that wing is aluminum.

Let me give you a hand.

Why would a surface with multiple joints and seams be considered as good or better than a smooth surface with no discontinuities? Clearly the latter would be a better solution because there would be less surface disruptions, less maintenance, less cost, less weight ect. Why on earth would I ever want fillers and the cost weight, maintenance, and cracking associated with it when I can just manufacture one smooth large surface?

Because your large, smooth monolithic composite structure would have all the same problems and require coatings and fillers to fix them. You would be dealing with discontinuities within the material itself as the electrical properties change throughout the composite structure. Composites by their nature are not homogeneous.

 

[flateric]

"The wing box is an aluminum structure with three full depth beams. There are twenty ribs located throughout the box. The wing is a fuel tank out to rib 14. The wing box planks are all flat machined integrally stiffened panels. The upper panels are removable while the lower panels are permanently attached."

 

[overscan (PaulMM)]

90% is a significant reduction. Even 40% or 60% would be significant.

Even a 90% reduction in RCS is only a 44% reduction in detection range. Hardly "stealthy".

 

[Bounce]

What happened to my post?

 

[overscan (PaulMM)]

It was deleted as offtopic, but I guess this is the offtopic topic so...

 

[donnage99]

I actually posted scientific articles disproving your claims and worked on LO projects. I wasn’t anyone special but I have extensive knowledge in composites and spoke to DARPA engineers regarding composites.

If you did, your cubicle had the furthest distance from the RCS guys, consider only a few months ago you confused between platform and edge alignment with the imaginary tilt of the nozzle axis. This was your drawing on may 3rd 2025:

 

[donnage99]

I'd like people to cut out this lowly slander that countries other than the US cannot possibly create a stealth aircraft. It's unbecoming of you.

No one is saying they couldn't create stealthy aircraft because they're russians.

Overscan is refuting original laughable claim that"russians know all there is to VLO techniques" without knowing what VLO techniques different firms have discovered out there in the world. One can reasonably assumed french VLO techniques are probably not in the same class as the Americans or Chinese and yet I doubt anyone can confidently say that whatever the french has discovered, the americans already know. That would require comprehensive knowledge into both countries' various LO programs many are classified or proprietary protected.

I myself made the claim that russians obviously know all the basic principle of stealth such as smooth surface with edge alignments. The glaring lack of edge alignments on radome this late into the program can be deduced to a lack of maturity in associated technologies to make smoothing of the surfaces and edge alignments a worthwhile investment. Shaping is always the starting point, but it works in conjunction with the material science side as inseprable package to provide significant rcs reduction. Further reinforced is the proposal of t75 has the radome edge alignment, suggesting that the material science has caught up to make such shaping work in significant rcs reduction

First. the basic shaping of the Su-57 is sound for a VLO design, as indenpendently confirmed by the French, when they presented their research for their next-gen stealth jet, and they basically came up with the exact planform of the Su-57

the french windtunnel model is nothing like the su-57 except for the use of LERX. It has the same commonality to the su-57 as it is to the indian tejas.

I'm sure if the Russian requirements didn't call for VLO, but just the other stuff, they'd have had an easier time making another advanced Flanker variant.

That's such a binary black and white take. it's not stealthified version of the flanker therefore requirements must have been VLO on the same level of the americans or chinese. Most likely it is somewhere inbetween these 2 ends.

Somehow people in this thread (and the internet in general) are implying that small details like radome, the IRST or DIRCM ball, the exposed rivets or joints, partially visible engine faces 'ruin' the otherwise good VLO design. My assertion is that this is not the case, I'm sure each of these problems has a technical solution that adequately eliminates it, and prevents RCS 'hotspots' destroying the VLO nature of the design.

No one should think that russian designers just accidentally forgot these basic details. However, these lack of alignments exist to highlight the level of stealth the requirements must have been. Example - We do not see every panels and apertures aligned on the super hornet or kf-21 because outside of RAM treatment of hotspot there isn't the neccesary commplex layering of materials and RAS solutions that specifically target localized sets of frequencies depending on how the surface waves interact with the bulges and bumps of the aircraft. As I have repeated multiple times, the lack of stringent edge alignment on panels, apertures are not accidental or lapse of judgement. they are intentional and they do reveal about the lack of associated techs that are not visible to the naked eyes.

• Large flat, planform aligned surfaces have been used for stealth on US aircraft such as the F-22 or B-21, they work by only reflecting the energy back to the radar when they are perpendicular to the surface, causing the 'spiky' RCS of these aircraft. Geometry is enough in this case, there's no need for advanced materials, just a simple coductive skin.

Please google close up views of these aircrafts. There are plenty of curved surfaces.

B-22 and YF-23 are the prime examples of manipulation of surface waves towards the leading edges which also align nicely with area ruling. The skin wraps smoothly over the engines and inlets with no discontinuity with curvatures where different platform angles meet. The only aircraft that just resort almost entirely to flat surfaces to handle specular waves and just coat hotspots in heavy RAMs is the f-117. An outdated approach that result worse stealth and worse kinetic performances. F-22 despite having more curvatures, used less RAMs and utilized more advance techniques that do not compromise weight as much.

• This 'converting specular waves to surface waves' business ....I'm sure this approach works as well, and might explain why the F-35 has such a bumpy underside, but sounds expensive and finicky....That the Americans went back to simple geometric shapes with the B-21 might be also telling.

F-35 is confined by the jack of all trade requirements packed into a a small airframe with somewhat ok drag, so lots of bumps and lumps that have tailored rcs management solutions. B-21 is a bomber unrestricted by the drag and size confinement of a single engine fighter so yes simple geometric shape is of course a better solution

• Russians could make something like this if they really wanted to, but there's reasons for not going down this route.

A fanboism type of statement. There's no proof either for or against.

 

[yeetmahboi]

The basic metric now for VLO is (bombing opposition parliament building with a 20nm range glide bomb). The victim mentality card is refreshing for a celebrated technical forum turning into guilt-tripping others, but the F-117, F-22 and now B-2 set the standards.

Unlike some, I'm not working in RF theory and I'm not pretending that my opinion is worth a damn over what is simply corroborating from historical/technical evidence evidence versus finger pointing towards some imaginary capabilities.

Fundamentally the entire Su-57 program reflects a Schrodinger in action: either the requirements was not competitive to the F-35 in certain aspects or the engineering basis was limited to execute so. The exact cause is out of reach for the next 20 years or so, but none of it refutes the fact that what the Su-57 had in shortcomings presents it as an inferior equipment to the F-35 in the Western mind. Of course over the years this has become accepted that the bird trades stealth for other specs but some people with presupposed allegiances probes through the agreement hence continuous debates about "it's a trash kit" or "it's actually ultra stealthy see".

In this current case, the problems lies on the latter, if some actually looks back to the original troublemakers. None is arguing that the Russians are dumb or that they can't make stealthy vehicles, because those a definite expressions without a marker like "in the year of 1990-2002" like what's actually being said here, that early on Russia didn't have the experience or the knowledge like what known VLO builders has in the SAP dossiers.

Of course how blunt other posters were only poured more oil into the fire.

 

[Galaxy]

Fighters use composites extensively. The F-35 and F-22 are two examples. Composites are often used for weight savings - not to add weight as you assert.

I was referring to thick composites as they add weight. Something like so called honeycomb composites. There are obviously thin and lightweight composites but that was not what I was referring too.

"90%" is about a 10db reduction. I am sure you are familiar with the radar range equation. A "90%" reduction is not significant.

The source I posted cited over −40 dB reduction as well. Is that also insignificant? This is all subjective, -10db or -30db may not seem significant to you but it is to me as it could be the difference between staying undetected and being engaged by enemy fire.

So you're not actually certain you see the use of composites? Clearly the primary material of that wing is aluminum.

Let me give you a hand.

View attachment 781930

The yellow areas are where speculated was the composites and I never seen an F-117 diagram before. So I was correct in identifying the areas with composite material but not correct in that it composites made the majority of the wing

Because your large, smooth monolithic composite structure would have all the same problems and require coatings and fillers to fix them. You would be dealing with discontinuities within the material itself as the electrical properties change throughout the composite structure. Composites by their nature are not homogeneous.

That is correct, a smooth monolithic composite would still require coatings, filler’s, perhaps adhesive strips, ect but the advantage is it would require less and have less imperfections. The other issue is not every panel or rivet can be covered up, for instance areas around access ports or heat sensitive areas. Here is an example using aluminum. Notice the middle (light green) area uses a large panel, the sides use smaller panels (light red) notice how much less rivets the middle has?

 

[Galaxy]

If you did, your cubicle had the furthest distance from the RCS guys, consider only a few months ago you confused between platform and edge alignment with the imaginary tilt of the nozzle axis. This was your drawing on may 3rd 2025:

The engine axis lined up perfectly with the vertical stabilizers even if my lines which was just for illustration purposes did not perfectly match. And my entire argument was that the axis matches with and aligned with vertical stabilizers, fuselage, intakes ect.

Let’s see what AI says about platform alignment:

“Planform alignment means designing an aircraft (or other stealth vehicle) so that all major edges — wing leading/trailing edges, tail surfaces, intakes, access panels — are aligned along a small set of common angles. By doing this, radar energy hitting the aircraft tends to scatter in only a few predictable directions instead of back to the radar antenna.”


Edge alignment and edge diffraction are interchangeable. While platform alignment is similar to edge alignment in that it’s a predictable design meant to direct energy away in a predictable manner.

 

[Galaxy]

View attachment 781933

Even a 90% reduction in RCS is only a 44% reduction in detection range. Hardly "stealthy".

Which is a lot. That is the difference between staying undetected and being shot down. By the way my source also quoted a -40db reduction.

https://onlinelibrary.wiley.com/doi/full/10.1002/advs.202303104

“Meanwhile, Wu et al. fabricated polyaniline-based composites with a 30 wt.% of CBs to obtain a maximum absorption of −40 dB for the frequency range of 9.0–13.0 GHz (the X-band)”

 

[overscan (PaulMM)]

Which is a lot. That is the difference between staying undetected and being shot down.

It's not "stealth", which involves multiple orders of magnitude reductions.

By the way my source also quoted a -40db reduction.

https://onlinelibrary.wiley.com/doi/full/10.1002/advs.202303104

“Meanwhile, Wu et al. fabricated polyaniline-based composites with a 30 wt.% of CBs to obtain a maximum absorption of −40 dB for the frequency range of 9.0–13.0 GHz (the X-band)”

That is not carbon fibre. It's an article about carbon-based RAM, with the best performers using graphene, carbon nanotubes etc. Carbon-fibre based RAM is described as a moderate absorber at best, and thats when explicitly designed as RAM.

Carbon fibers

-Easy to single-layer and multi-layer structures -Moderate microwave absorbing performance

-Difficult to dry -High cost -Difficult to use for large-scale

 

[donnage99]

The engine axis lined up perfectly with the vertical stabilizers even if my lines which was just for illustration purposes did not perfectly match. And my entire argument was that the axis matches with and aligned with vertical stabilizers, fuselage, intakes ect.

Let’s see what AI says about platform alignment:

“Planform alignment means designing an aircraft (or other stealth vehicle) so that all major edges — wing leading/trailing edges, tail surfaces, intakes, access panels — are aligned along a small set of common angles. By doing this, radar energy hitting the aircraft tends to scatter in only a few predictable directions instead of back to the radar antenna.”


Edge alignment and edge diffraction are interchangeable. While platform alignment is similar to edge alignment in that it’s a predictable design meant to direct energy away in a predictable manner.

You meant the inner walls of the engine which is entirely covered by everything else surrounding it minus a narrow set of angles from behind?

Or (please oh God please help it not to be true) you're still doubling down on the imaginary axis of the engine tilt being part of platform alignment 'cause you keep referring back to the word "axis"?

The rest of your response I crossed out because it seems your tactic of response is posting basic uncontroversial definitions or word salad irrelevant to the specific point of contention.

 

[Elysium]

I'm sure there is, every aircraft has a requirements document it is built to.



Umm, let's put in a 'theoretically' there. So that line becomes 'hitting these requirements is theoretically the prerequisite for the plane being accepted into service.'

The history of aviation is full of aircraft that missed their targets, and many of these still went into service. Often this was in wartime and anything sufficiently better than what was in service was still worth having, while nowadays we have the issue where aircraft development is so expensive governments may be unwilling to bear the cost of starting over (a variation on 'sunk cost' issues).

In some cases the aircraft may completely fail to meet the original requirement, but can still meet other needs, for instance the Hawker Typhoon, which was supposed to be a medium/high altitude interceptor to replace the Hurricane, turned out to be a dog at altitude, but was a fast low-level interceptor, and kept in production as a low-level fighter-bomber. (ETA: and never mind it's occasional tendency to have the tail fall off)

TLDR: Just because a requirement set a target doesn't mean the aircraft built to it actually met the target.

If you believe that Russians didn't manage to mitigate the issues that people keep pointing out, the onus of proof is on you. Believing that an army of professionals either didn't think of the issues that keep getting raised by enthusiasts, or just shrugged their shoulders doesn't seem very plausible to me.
Let me reiterate - given the fact, that the program had numerous delays and problems, which were widely discussed even in official reports, and very little was said about signature management, leads me to believe they hit their performance targets easily. Otherwise I'd suspect there would've been both discussion from the aforementioned sources, and visible reworks (for which they both had the time and opportunity).

 

[Galaxy]

You meant the inner walls of the engine which is entirely covered by everything else surrounding it minus a narrow set of angles from behind?

Or (please oh God please help it not to be true) you're still doubling down on the imaginary axis of the engine tilt being part of platform alignment 'cause you keep referring back to the word "axis"?

The rest of your response I crossed out because it seems your tactic of response is posting basic uncontroversial definitions or word salad irrelevant to the specific point of contention.

How convenient that you crossed out the part were I disproved your fake accusations. It’s also YOU that keeps going around and bringing up this topic and it’s YOU that has the burden of proof to disprove what was said. You can’t make accusations and then ignore responses.

Inner wall, outer wall, it makes no difference. Look at the axis of the nozzle and the orientation of the vertical stabilizers or other canted surfaces.

 

[Galaxy]

It's not "stealth", which involves multiple orders of magnitude reductions.


That is not carbon fibre. It's an article about carbon-based RAM, with the best performers using graphene, carbon nanotubes etc. Carbon-fibre based RAM is described as a moderate absorber at best, and thats when explicitly designed as RAM.

The article states the following:

“Due to its favorable properties, CB has been the most commonly applied reinforcing carbon filler in the manufacture of composites since the First World War, and is used in applications such as a reinforcing agent to provide mechanical strength to absorber materials. Moreover, the electrical properties of a composite can be enhanced by adding CB with a low particle density (high porosity), small particle size (large surface area), low volatility (few oxygen groups), and favorable structure (better aggregation). This section covers some examples of CB-based RAMs as composites, single- and multi-layer composites.

Kwon et al. investigated the reinforcing effects of varying compositions (5, 10, 20, and 30 wt.%) of CB (Vulcan XC-72) fillers in the silicone rubber matrices of single-layer composites.[76] The optimum CB content was identified as 10 wt.%, giving a maximum RL of −22.2 dB in the frequency range of 11.6 GHz at a sample thickness of 1.9 mm (Figure 7a). Similarly, Oh et al. studied the effects of various contents (5, 6, 7, 8, 10, 15, and 20 wt.%) of CB (Vulcan XC-72) filler in the grass fabric/epoxy prepreg of multi-layer composites to conclude that the incorporation of 7 wt.% CB significantly enhanced the microwave absorbing properties of the composite, giving an RL of less than 10 dB in the frequency range of 2.4 GHz with a 0.6 mm thick sample.[77] Meanwhile, Lee et al. reported the fabrication of polypropylene-based composites with inner diameters of 3 and 7 mm and various contents of CB (Xyui Zongze) via fused deposition modeling technology, as shown in Figure 7b.[78] The optimal CB content was found to be 10 wt.%, giving a maximum RL of –62.6 dB at 10.6 GHz with a 2.8-mm thick sample. The authors concluded that the microwave attenuation capacity was mainly due to conductive loss, interfacial polarization, dipole polarization, and multiple internal reflections, and that these properties were affected by the distribution of the CB particles.“


It looks like they impregnated carbon black into resin. The best results were -62db at 10.6GHz. Maybe Im just reading it wrong but it does sound like they used various amounts of carbon black by weight in composite materials.

 

[donnage99]

How convenient that you crossed out the part were I disproved your fake accusations. It’s also YOU that keeps going around and bringing up this topic and it’s YOU that has the burden of proof to disprove what was said. You can’t make accusations and then ignore responses.

Inner wall, outer wall, it makes no difference. Look at the axis of the nozzle and the orientation of the vertical stabilizers or other canted surfaces.

It's crossed out because it has nothing to do with the point of contention. If it's irrelevant it's not proving anything. I'm starting to doubt you might be foreign asset of some sort trying to trigger some of us into a war thunder type of moments. No way someone who can articulate his thoughts quite well, can get themselves through certain technical articles, and yet just fail to comprehend the most basic and simplistic concepts.

Let me help you by asking you this, so the radar waves make contact and bounce off from imaginary axis of the nozzle or with the physical outer and inner surfaces of the nozzle?

 

[overscan (PaulMM)]

If you believe that Russians didn't manage to mitigate the issues that people keep pointing out, the onus of proof is on you. Believing that an army of professionals either didn't think of the issues that keep getting raised by enthusiasts, or just shrugged their shoulders doesn't seem very plausible to me.
Let me reiterate - given the fact, that the program had numerous delays and problems, which were widely discussed even in official reports, and very little was said about signature management, leads me to believe they hit their performance targets easily. Otherwise I'd suspect there would've been both discussion from the aforementioned sources, and visible reworks (for which they both had the time and opportunity).

All evidence suggests the RCS targets were not very challenging and only really applied to the front quadrant. It's quite possible Sukhoi achieved them just fine. Clearing the bar isn't challenging when you set it low.

Russian insistence on quoting large RCS values for US Stealth aircraft (e.g 0.1 sq m for F-117, 0.3 sq m for F-35) suggests one of the following to be true:

1) US has been routinely lying about stealth RCS values for 40 years
2) Russia uses a method of measuring RCS that minimises apparent differences between stealthy and normal designs e.g. quoting maximum RCS in "spike" directions while US quotes RCS in 'non-spike" directions.
3) Russia is unable to calculate RCS correctly
4) Russia is able to calculate RCS correctly but intentionally lies about US Stealth achievements

 

[donnage99]

If you believe that Russians didn't manage to mitigate the issues that people keep pointing out, the onus of proof is on you. Believing that an army of professionals either didn't think of the issues that keep getting raised by enthusiasts, or just shrugged their shoulders doesn't seem very plausible to me.

Refer to my response post #95

There exists an explanation that avoid both ridiculous conclusions of either 1) russian engineers miss the most basic and obvious stealth features that even enthusiasts know, or 2) russians invented alternative physics that bypass general stealth features that the rest of the world, US, China, etc. adhere to.

 

[overscan (PaulMM)]

The article states the following:

“Due to its favorable properties, CB has been the most commonly applied reinforcing carbon filler in the manufacture of composites since the First World War, and is used in applications such as a reinforcing agent to provide mechanical strength to absorber materials. Moreover, the electrical properties of a composite can be enhanced by adding CB with a low particle density (high porosity), small particle size (large surface area), low volatility (few oxygen groups), and favorable structure (better aggregation). This section covers some examples of CB-based RAMs as composites, single- and multi-layer composites.

Kwon et al. investigated the reinforcing effects of varying compositions (5, 10, 20, and 30 wt.%) of CB (Vulcan XC-72) fillers in the silicone rubber matrices of single-layer composites.[76] The optimum CB content was identified as 10 wt.%, giving a maximum RL of −22.2 dB in the frequency range of 11.6 GHz at a sample thickness of 1.9 mm (Figure 7a). Similarly, Oh et al. studied the effects of various contents (5, 6, 7, 8, 10, 15, and 20 wt.%) of CB (Vulcan XC-72) filler in the grass fabric/epoxy prepreg of multi-layer composites to conclude that the incorporation of 7 wt.% CB significantly enhanced the microwave absorbing properties of the composite, giving an RL of less than 10 dB in the frequency range of 2.4 GHz with a 0.6 mm thick sample.[77] Meanwhile, Lee et al. reported the fabrication of polypropylene-based composites with inner diameters of 3 and 7 mm and various contents of CB (Xyui Zongze) via fused deposition modeling technology, as shown in Figure 7b.[78] The optimal CB content was found to be 10 wt.%, giving a maximum RL of –62.6 dB at 10.6 GHz with a 2.8-mm thick sample. The authors concluded that the microwave attenuation capacity was mainly due to conductive loss, interfacial polarization, dipole polarization, and multiple internal reflections, and that these properties were affected by the distribution of the CB particles.“


It looks like they impregnated carbon black into resin. The best results were -62db at 10.6GHz. Maybe Im just reading it wrong but it does sound like they used various amounts of carbon black by weight in composite materials.

Carbon black ≠ carbon fibre ≠ carbon nanotubes ≠ graphene

RAM made with any of the above ≠ standard carbon-fibre composite structural material.

you might as well say carbon fibre must be as hard as a diamond and transparent, after all, diamonds are made of carbon too.

 

[Elysium]

Apologies for answering your points out of order.

the french windtunnel model is nothing like the su-57 except for the use of LERX. It has the same commonality to the su-57 as it is to the indian tejas.

The windtunnel model is exactly like the Su 57 except that the wing has moved back, probably to compensate for the lack of tail - anyway let's see what the flying article looks like compared to an idealised, simplified shape they can get away with at this stage.

That's such a binary black and white take. it's not stealthified version of the flanker therefore requirements must have been VLO on the same level of the americans or chinese. Most likely it is somewhere inbetween these 2 ends.

I agree, I don't think the Russians aimed for the same level of stealth, but that does not mean it's not VLO. If we assume a radar that can see an 1m2 target at 250km, that will be able to see a 1cm2 target (F-35 assumption) at 25km. If we assume the Su-57x is 10x worse (or 5x worse when normalized to area, maybe?), that range increases to 44km, which is still VLO.

No one should think that russian designers just accidentally forgot these basic details. However, these lack of alignments exist to highlight the level of stealth the requirements must have been. Example - We do not see every panels and apertures aligned on the super hornet or kf-21 because outside of RAM treatment of hotspot there isn't the neccesary commplex layering of materials and RAS solutions that specifically target localized sets of frequencies depending on how the surface waves interact with the bulges and bumps of the aircraft. As I have repeated multiple times, the lack of stringent edge alignment on panels, apertures are not accidental or lapse of judgement. they are intentional and they do reveal about the lack of associated techs that are not visible to the naked eyes.

I am not prepared to address, or speculate about how the Russians addressed every problem, but I'd assume they did, and the final design has no hotspots that dominate the signature of the aircraft.

B-22 and YF-23 are the prime examples of manipulation of surface waves towards the leading edges which also align nicely with area ruling. The skin wraps smoothly over the engines and inlets with no discontinuity with curvatures where different platform angles meet. The only aircraft that just resort almost entirely to flat surfaces to handle specular waves and just coat hotspots in heavy RAMs is the f-117. An outdated approach that result worse stealth and worse kinetic performances. F-22 despite having more curvatures, used less RAMs and utilized more advance techniques that do not compromise weight as much.

The F-22s body ahead of the engines is flat as a washboard. The F-117s underside is also quite flat. So is the B-21 which is SOTA. Geometric stealth might not be the only game in town, but its still clearly a top contender. By 'flat' I mean minimizes, the number of angles in which it presents a large surface mostly perpendicular to the radar, so this includes gently sloped suraces as well.

Overscan is refuting original laughable claim that"russians know all there is to VLO techniques" without knowing what VLO techniques different firms have discovered out there in the world. One can reasonably assumed french VLO techniques are probably not in the same class as the Americans or Chinese and yet I doubt anyone can confidently say that whatever the french has discovered, the americans already know. That would require comprehensive knowledge into both countries' various LO programs many are classified or proprietary protected.

I have not made any claims about the relative advancement of Russian and US stealth tech, as this is the territory of pure unfounded speculation. I will readily accede that US tech is probably, better, the question is by how much. Here are a couple assumptions.

1. The B-21 relies on geometric stealth meaning there's not been a discovery that reduces the signature by orders of magnitude.
2. Stealth has been a thing for decades, and the field is fairly mature, so eking out tens of percents of signature reduction is a monumental achievement.
3. The main way of 'doing stealth' is by embedding fibers with special electrical properties into the composite skin of the aircraft. The layering and composition of the skin is the scecret sauce. All major aerospace nations have access to automated fiber-laying robots, and have a a decent understanding of how to do this.
4. Let's say US RAM is twice as good as Russian. Due to the radar equation, that confers only a 15% reduction in detection range.

 

[overscan (PaulMM)]

If we assume a radar that can see an 1m2 target at 250km, that will be able to see a 1cm2 target (F-35 assumption) at 25km.

Correct

If we assume the Su-57x is 10x worse (or 5x worse when normalized to area, maybe?), that range increases to 44km, which is still VLO.

And the evidence that suggests Su-57 has a 10 sq cm RCS is what, exactly? What's the basis of the assumption?

There is as much evidence that its 0.1-0.3 sq m, which would mean a range of 140.5 - 185 km - and put it definitively outside the definition of VLO.

I am not prepared to address, or speculate about how the Russians addressed every problem, but I'd assume they did, and the final design has no hotspots that dominate the signature of the aircraft.

An assumption based on what observation?

We don't know that the Russian even tried to make Su-57 truly stealthy other than some front quarter shaping. They might have looked at the cost of developing US-equivalent stealth and decided it wasn't worth it. And don't get me wrong - that might be a valid position to take!

 

[overscan (PaulMM)]

We are simply rehashing the same arguments made many times before.

 

[Elysium]

Correct

And the evidence that suggests Su-57 has a 10 sq cm RCS is what, exactly? What's the basis of the assumption?

There is as much evidence that its 0.1-0.3 sq m, which would mean a range of 140.5 - 185 km - and put it definitively outside the definition of VLO.

No there's a lot of regurgitated wishful thinking with no clear factual source mentioned. If you link back to either a reputable source from either the Russian military or Sukhoi engineering (people who would know this sort of thing), or a decent enough independent engineering (not military 'analysis') academic paper I will readily accept that claim. You can probably find a ton of Quora posts and War Zone articles to support that claim, but I'm sure we don't have to go there.

An assumption based on what observation?

An assumption if you spend 90% of the effort to make a stealth aircraft, you don't mess up the small details, especially if you have 15 years to get them right,.
I repeat: there's tons of official news that paint Russian technological competence in a bad light (I mentioned them before), there's very little to suggest they couldn't make stealth work.

 

[DWG]

If you believe that Russians didn't manage to mitigate the issues that people keep pointing out,

Not my point. My point is the existence of a requirements document does not mean the requirements were met. You can't argue from that point because of the extensive evidence that requirements=requirements met is not the general case.

given the fact, that the program had numerous delays and problems, which were widely discussed even in official reports, and very little was said about signature management

The first rule of stealth club is we don't talk about stealth club.

 

[DWG]

An assumption if you spend 90% of the effort to make a stealth aircraft, you don't mess up the small details, especially if you have 15 years to get them right,.

Is this where we bring A-12 into the discussion?

 

[Elysium]

Just let me get into a quick tech argument about said details.
Let me demonstrate a few bad assumptions, in some more professional articles such as these:
https://basicsaboutaerodynamicsanda...2022/09/26/su-57-radar-scattering-simulation/
It looks pretty professional, and concludes the median RCS of the fighter is 0.4 sqm in the X-band.
But it makes few very basic errors, such as assuming the whole aircraft is made of metal, including the DIRCM and IRST balls, which look like ~30cm in size. Guess what, if your aircraft includes a 30cm diameter metal ball, it's RCS cant be smaller than that.
People also constantly mention the lack of S-ducts - I'd like to point out you probably have a microwave at home in the ~1000W category. The wire mesh on the door manages to absorb 99.99% of its energy, otherwise it'd be illegal to sell and a health hazard. I'm sure if you have jet fighter money, you can do at least as well as that.

Btw, there are other anomalies with that article, like it claims the Su-57s RCS is bigger when the radars are positioned in the front(Case 2), as opposed to when they're positioned to the side (Case 1).
Even with all this considered, the X-band RCS is only 7x that of the F-35. Not saying it's a good article, but at least some effort went into it.

 

[TMA1]

The mod who deleted Bounce's post is a shameless knave. I am genuinely pissed off.

 

[Galaxy]

It's crossed out because it has nothing to do with the point of contention. If it's irrelevant it's not proving anything. I'm starting to doubt you might be foreign asset of some sort trying to trigger some of us into a war thunder type of moments. No way someone who can articulate his thoughts quite well, can get themselves through certain technical articles, and yet just fail to comprehend the most basic and simplistic concepts.

Let me help you by asking you this, so the radar waves make contact and bounce off from imaginary axis of the nozzle or with the physical outer and inner surfaces of the nozzle?

I’m a “foreign asset” now? Im flattered that I’m living in your head rent free
Electromagnetic energy can bounce off the sides of a nozzle, the insides, pass over the front, sides ect depending on aspect angle or interference from flight control surfaces or creeping wave phenomena. My theory is the nozzle is off set to align with other structures of the aircraft to achieve a more predictable radar scatter.

 

[Null]

I think it is just down all to stealth material technology that might determine the costs, the US is no longer the only country that possesses radio wave chambers in how they should structure their aircrafts. Like AFAIK I don't see anyone bashing the Su-75, Su-70 or the TAI TFX. If their military still finds it noteworthy to produce Su-57s and even modify them to Su-57Ms then that probably means they have a use for them for whatever conflicts they might engage later.

 

[donnage99]

I’m a “foreign asset” now? Im flattered that I’m living in your head rent free
Electromagnetic energy can bounce off the sides of a nozzle, the insides, pass over the front, sides ect depending on aspect angle or interference from flight control surfaces or creeping wave phenomena. My theory is the nozzle is off set to align with other structures of the aircraft to achieve a more predictable radar scatter.

so does it bounce off with the imaginary axis or not? Answer the question