Su-57 Stealth Fighter: News #8

To keep them warm

To keep them warm

Such tarps don't generate heat, they just prevent ice buildup and snow from settling on the surface... it is like putting newspaper on your car windscreen in winter so you don't have to scrape a layer of ice off it in the morning...

Where do people get the SU57 RCS figures from? As far as I know Sukhoi hasnt released any figures yet. How do people know its less stealthy than the F35 and F22? Is it just a general hate for anything Russian in the western world?

Please introduce yourself before posting as per the site rules.

Also, starting narrow topic threads like this is frowned on as it clogs things up. It should be in the normal Su-57 thread.

They take those values from their ass mainly. Some try making rcs measurement softwares but they are stupid people with no background and take some formulas and some data they find on internet.

All the figures are not real.

Isos wrote:They take those values from their ass mainly. Some try making rcs measurement softwares but they are stupid people with no background and take some formulas and some data they find on internet.

All the figures are not real.

I think kvs called it eye-balled RCS evaluation. But here's something to consider:

Something that's poorly understood by Westerners is the Su-57's doctrine of operation, which is purely defensive (i.e. defend Russian airspace), and it's means of operating.

Because it's primary purpose is to defend Russian airspace it could rely on both 'Early Warning' and OTH radars, etc. through data links, and likely could launch R-37M's without even turning it's radar on.

Another aspect to consider is the fact that Russia never puts all it's eggs in one basket. Russia will have Su-57's with RAM coating and stealth shaping which will be quite effective against X-band radar, but there is other pieces to the jigsaw puzzle. They also have ECM systems on the ground that will mask Su-57 presence through the electromagnetic spectrum by blurring and obscuring the EM spectrum giving back poor radar signal returns. They can spoof ELINT/SIGINT/radars of OPFOR with false readings and false targets, as well as outright jamming them. There's also been talk that Su-57's will incorporate electromagnetic opaque aerosol dispensers in the rear next to the jet engine thrust nozzles.

Swgman_BK wrote:Where do people get the SU57 RCS figures from? As far as I know Sukhoi hasnt released any figures yet. How do people know its less stealthy than the F35 and F22? Is it just a general hate for anything Russian in the western world?

They got them from thin air, and wet dreams.
Sukhoi only made the very known statement that a typical stealth aircraft has an average RCS value in the 0.X range. For practical purposes.

magnumcromagnon wrote:

Isos wrote:They take those values from their ass mainly. Some try making rcs measurement softwares but they are stupid people with no background and take some formulas and some data they find on internet.

All the figures are not real.

I think kvs called it eye-balled RCS evaluation. But here's something to consider:

Something that's poorly understood by Westerners is the Su-57's doctrine of operation, which is purely defensive (i.e. defend Russian airspace), and it's means of operating.

Because it's primary purpose is to defend Russian airspace it could rely on both 'Early Warning' and OTH radars, etc. through data links, and likely could launch R-37M's without even turning it's radar on.

Another aspect to consider is the fact that Russia never puts all it's eggs in one basket. Russia will have Su-57's with RAM coating and stealth shaping which will be quite effective against X-band radar, but there is other pieces to the jigsaw puzzle. They also have ECM systems on the ground that will mask Su-57 presence through the electromagnetic spectrum by blurring and obscuring the EM spectrum giving back poor radar signal returns. They can spoof ELINT/SIGINT/radars of OPFOR with false readings and false targets, as well as outright jamming them. There's also been talk that Su-57's will incorporate electromagnetic opaque aerosol dispensers in the rear next to the jet engine thrust nozzles.

can you explain the electromagnetic opaque aerosol dispensers part?

Swgman_BK wrote:

magnumcromagnon wrote:

Isos wrote:They take those values from their ass mainly. Some try making rcs measurement softwares but they are stupid people with no background and take some formulas and some data they find on internet.

All the figures are not real.

I think kvs called it eye-balled RCS evaluation. But here's something to consider:

Something that's poorly understood by Westerners is the Su-57's doctrine of operation, which is purely defensive (i.e. defend Russian airspace), and it's means of operating.

Because it's primary purpose is to defend Russian airspace it could rely on both 'Early Warning' and OTH radars, etc. through data links, and likely could launch R-37M's without even turning it's radar on.

Another aspect to consider is the fact that Russia never puts all it's eggs in one basket. Russia will have Su-57's with RAM coating and stealth shaping which will be quite effective against X-band radar, but there is other pieces to the jigsaw puzzle. They also have ECM systems on the ground that will mask Su-57 presence through the electromagnetic spectrum by blurring and obscuring the EM spectrum giving back poor radar signal returns. They can spoof ELINT/SIGINT/radars of OPFOR with false readings and false targets, as well as outright jamming them. There's also been talk that Su-57's will incorporate electromagnetic opaque aerosol dispensers in the rear next to the jet engine thrust nozzles.

can you explain the electromagnetic opaque aerosol dispensers part?

The EM opaque aerosols/cosmosols effectively absorb EM radiation, like RAM but far better and covers the whole entirety of EM spectrum.

I think part of it is a different approach... if you have ever seen a 2D graph showing RCS for a complex shape like an aircraft it is all spikey for each different angle so the idea that one number can describe the stealth level of an aircraft is a bit ridiculous.

Like this for instance:



As you can see the figure is massively variable depending on the angle you view the aircraft from... things like the fuselage side and vertical tail surfaces and engine and tail interactions make side and rear RCS rather bigger than the frontal aspect... but of course this chart needs a radar frequency to qualify it... against a longer wave radar the numbers would be closer to the actual size of the aircraft... BTW I do not vouch for the information in this picture... just posted it as an example.

Imagine the same view in 3D... an incredibly complex porcupine...

The core of the issue is that for marketing purposes the west tends to use peak numbers for its own stealth designs and the Russians use a more realistic average figure... so the Su-57 having a RCS of 0.1 to 0.5 might actually be better than an F-35 with a peak figure of 0.001, because that might be the best ideal angle and frequency... which may never be achieved.

Eh, there are many ways to present RCS numbers. Unfortunately in general, "public" number they are presented without context. e.g Frequency or polarization. Both Russian and US also Chinese numbers lacks frequency information and people just assume it's for X-band which is dangerous.  Even worse there are no real established standard on what to present and how, so everyone is basically doing their own thing. Thus makes the value from all sides practically useless for any purpose other than just to show "relative magnitude" of the RCS.


There is however some pointers. If one read "RCS Measurements" by E Knott particularly at Page 351-383 about Data smoothing and basically what to do with the measurement data. One would see that it has to be processed statistically.  The data will need to be presented in smoothed form or in Median or mean value.

Page 383 further elaborated about the "users" of the data and what value which may be of their interest. For radar designers and engineers it is CDF (Cumulative Distribution Function) or PDF (Probability Density Function) That serve the most important function. While other user maybe interested in something else e.g the generation mechanism or just to find which side to treat and the potential effect of say changes in design.

in "Electromagnetic Wave Scattering by Aerial and Ground Radar" by Oleg Sukharevsky, elaborated further on the method of data reduction and curve fitting for the PDF.  The book gave Median RCS for the value to go for quick calculation of radar range against certain target, which assumes the target will remain steady.  The median value provides 50% probability that one will encounter that Median RCS with 50% others are either bigger or smaller value than that.

In case of random orientation of target however PDF equation should be used, These equations however might produce unrealistic result, for which the book suggest to use data Histogram to gain the proper value or just try fit some other equation.

The simplest way however is to assume the aircraft target to be a Swerling case-1 target which is a reasonable assumption for a target which illuminated by a single frequency. The PDF equation for Swerling case-1/2 are widely known. This requires average RCS for which to calculate "the most likely encountered RCS" for the target.

Now let's assume value of 0.057 sqm of average RCS.  and No, one does not use this value directly for calculation of radar range.  Now we wish to calculate what RCS we may encounter 90% of the time with that value if the target is randomly oriented.

We can easily use MS Excel's Goalseek feature and PDF equation for Swerling case 1 target which we will arrive with the value of 0.17 sqm.  Which we can present (But dont forget the frequency information). Now what if the equation provides unrealistic result ? e.g Negative value or some unrealistic over unity value ? Then one have to use Histogram of the RCS data. The following is one example of it :



One can see value of 0.0007 - 0.54 sqm as the most occurred value.  We can present this value.

I did not use the squared RCS as suggested by Sukharevsky's book mainly to show the "raw" kind of distribution one can expect from a swerling-1 target.


So in the end we have 3 kinds of Value we can present. Or maybe 4 if Instanteneous value is desired. This instanteous value is only useful for 1 angle tho. But by no means wrong.

First is the Median value which suitable for quick looks
Second is the PDF or CDF value which derived from Average of the RCS
Third is from Histogram in case we cannot fit suitable distribution equation for our data
Fourth is the instanteneous value.

Again those values NEEDS context mainly frequency as RCS is function of frequency too.  This is my example quite sometime ago for Radar Cross Section estimates for Su-57 and F-35. I am using Median value to give the quick and easy number people can use. The angular section is 120 degrees of arc (-60 to 60 degrees) Horizontal and 65 to 110 degrees vertical Which i consider to be the most likely aspect that can be exploited along with my PC limitations back then.



Notice the different value of RCS and in general the "looks" of the pattern as frequency changes.  

Hey stealthflanker I've always heard you discuss stuff in a fairly dry, academic sort of fashion but what do you personally think of the su-57? What are your views bro??

TMA1 wrote:Hey stealthflanker I've always heard you discuss stuff in a fairly dry, academic sort of fashion but what do you personally think of the su-57? What are your views bro??

She has her charm, sexually attractive. Which is the reason i always want to know her from inside out and accept her the way she was.

A note about the IRST.
Modeling its behaviour without RAM In context, especially for it, can be very misleading, as it is heavily implied that RAM does a great job attenuating its signature, as opposed to that massive EOTS in the belly of the LTS, which needed a faceted window.

Atmosphere wrote:A note about the IRST.
Modeling its behaviour without RAM In context, especially for it, can be very misleading, as it is heavily implied that RAM does a great job attenuating its signature, as opposed to that massive EOTS in the belly of the LTS, which needed a faceted window.

The calculation method for RCS gives huge differences even for relatively simple shapes. Plus gaps. Plus internals. Plus materials, dimensions and depths. Plus pitot tubes, rivets and all the rest of weak scattering sources. Plus the elephant in the room, the RADAR antenna and the rest of the apertures. Such estimations need to be taken with a HUGE pinch of salt, not to detract from stealthflanker's effort. And then of course as he says, frequency, polarization, aspect and so on are never detailed.

In summary, RCS values are simply too valuable pieces of information and they are never revealed or never in a way that allows to take tactical advantage from the disclosure. So it is one of the most stupid discussions of all the many and very stupid ones related to military technology.

LMFS wrote:

Atmosphere wrote:A note about the IRST.
Modeling its behaviour without RAM In context, especially for it, can be very misleading, as it is heavily implied that RAM does a great job attenuating its signature, as opposed to that massive EOTS in the belly of the LTS, which needed a faceted window.

The calculation method for RCS gives huge differences even for relatively simple shapes. Plus gaps. Plus internals. Plus materials, dimensions and depths. Plus pitot tubes, rivets and all the rest of weak scattering sources. Plus the elephant in the room, the RADAR antenna and the rest of the apertures. Such estimations need to be taken with a HUGE pinch of salt, not to detract from stealthflanker's effort. And then of course as he says, frequency, polarization, aspect and so on are never detailed.

In summary, RCS values are simply too valuable pieces of information and they are never revealed or never in a way that allows to take tactical advantage from the disclosure. So it is one of the most stupid discussions of all the many and very stupid ones related to military technology.

Exactly,
The collective scattering from different bits is going to have huge impacts on the RCS even as a pattern rather than raw numbers. Hence discrediting the entire "segmenting the aircraft into mere 3 or 4 sectors" discussions you find on the internet. The claiming things such as VLO from the back or from the front is fundamentally wrong, as those areas themselves are brimming with variation.

Hole wrote:

Important to notice:
It is basically a tunnel inside a tunnel, which explains why the intake is indeed curved while looking straight to the outside view.
This is once more, along with the IRST, another proof that all of the hubris around the tunnel intake was made by absolute clowns who could not read a patent.

oh no inb4 western stealth experts give their critics on this.

I did my shares on modeling the inlet and impact of the radar blocker and coatings and put it in the open. So far no real response or dispute from "western sources" They either not saying anything or just plain amazed that the radar blocker can do such amount of reduction. I am in several forums and discord servers about aviation where most members are US.



In fact there has been no real attempt in modeling them despite availability of commercial and powerful software like ANSYS HFSS.  The SBR+ Is one way to go for modelling cavities like inlet. I wonder why not many more people doing it. Which is unfortunate as visualization of RCS is an indispensable part in proper attempt of understanding the phenomenon.

I also did the 360 degrees.. which kind of like 2 doritos combined as one.

Nice work!

How do you think movements of the levcons effect stealth? What I have seen about the su-57's levcons is pretty fascinating. They are different from canards but do have some overlapping roles. Also they very good and regulating and modulating vortices and they can be stealthier than canards.

Another thing. When you are modeling the ram layers how specific can you get with that? I think there is a vague idea of what kind of ram the su-57 uses. Are these programs you use powerful enough to take into account some of this? Also how ram is applied matters, but that might be a bit too much to add to the model.

I also agree it is a sexy beast. To me one of the best things about it is it is a unique outlier of the fifth gen lineup. A completely different ideology in it's design and mission. And it doesnt hurt that it has lovely lines. As you can tell I am a fanboi, but I really think it is underrated by very many people.

lyle6 wrote:

Hole wrote:

Holy shit, is this legal? I feel like chucking myself out of a window just by looking at it

Of course, everything about this design points towards non-compromise.
It should also be factored that the Su-57's stealth includes the fact that cruise could be trimmed with TVC, thus not relying on surface actuators, these increase the RCS of an aircraft pretty much higher than any minute detail found on aircraft, in the same caliber as pitot tubes or so.
That is an extremely significant detail. The entire point of things like B2 and Okhotnik is the removal of the tail for RCS Reduction. I don't know why this detail is always left.

That is an extremely significant detail. The entire point of things like B2 and Okhotnik is the removal of the tail for RCS Reduction. I don't know why this detail is always left.

The main key clue is that the B-2 and S-70 are not ever engaged in dogfighting or extreme manouvering of any kind.

Vertical tails are useful for stability and normal flight control.