Su-57 Stealth Fighter: News #8

284KN for both engines.... I first wrote dry thrust for two engines combined, so it is logical that written afterburner thrust is for both engines - combined.. wrote:

Oh ok yeah that is true. My bad..

In fact I would say a modern Su-35 or upgraded Su-30 with L band radar and modern AESA radar in its nose together with an IADS should be able to pick apart any stealth fighter force as long as they have modern AAMs and can also use their sensors and datalinks to find targets for long range ground launched missiles like S-350 and S-400... and I think the Su-33 and MiG-29K could do the same at sea making them rather more powerful than their numbers would indicate otherwise. wrote:

This is unlikely to happen and if it does it wouldn't be very useful. The Mig31 is really the only fighter jet/interceptor in the world that can operate L Band radars in a resolution similar to the X band radars of the average jet because its PESA radar is HUGE!!.. Unless you mean using a small short range L band radar for missile approaches.. L band on the Su35 would have to be at least 3x as large the X band N035 on the Su35 to achieve similar resolution.. Range will be better (As well as seeing through clouds) but an L band radar the size of a N035 is gonna have trouble telling things 10meters apart as different objects.. If 2 jets fly really close to each other L Band is gonna pick them up as one thing.. It also sucks for guiding missiles. Its gonna take missile 10-20m off the target.. For L Band to achieve similar resolution as the N035/N036 it would have to be 3x larger physically.. L Band is just impractical at that size... Stealth is a very complex topic that we cant address with theories sadly..The common myth is L band defeats all Stealth.. Not entirely..Frequency selective surfaces differ..

The reasons I outlined there are why S band radars are only used for Navigation on Warships and not guiding Anti ship missiles or SAMs.. Chemically treated Iron pentacarbonyl paint has no effect on them.. but they are horribly inaccurate at tracking tiny stuff relative to their wavelength..

Anyone still got the links to the PAK-FA patents?
Especially the one with the aerodynamic features.
Thanks.

Arrow wrote:

So why use L-band radars on the wings of the Su 57?

Search, track and missile midcourse guidance against low signature aircraft.
Identification Friend Foe / Secondary Surveillance Radar.
Passive angle tracking and geolocation of JTIDS/MIDS/Link-16 emitters at long ranges.
Passive angle tracking and geolocation of L-band AEW&C/AWACS and surface based search radars at long ranges.
Passive angle tracking and geolocation of hostile (i.e. Western) IFF and SSR transponders at long ranges.
High power active jamming of JTIDS/MIDS/Link-16 emitters.
High power active jamming of satellite navigation receivers over large areas.
High power active jamming of L-band AEW&C/AWACS and surface based search radars at long ranges.
High power active jamming of guided munition command datalinks over large areas.
https://www.ausairpower.net/APA-2009-06.html

Atmosphere wrote:Anyone still got the links to the PAK-FA patents?
Especially the one with the aerodynamic features.
Thanks.

http://www.su57.mariwoj.pl/su57-index.html

Links to all Su-57 patents are at the bottom of the page.

So why use L-band radars on the wings of the Su 57? wrote:

Mainly MAWS and IFF..

Arrow wrote:

So what some people wrote here, that this L-band radar is used to detect stealth, is nonsense. This means that the Su-57 has the same limitations as other aircraft when it comes to stealth detection. X-band radar that stealth suppresses the most.

It is a contentious topic but some respected people have alluded to the L band arrays having stealth detection capabilities beyond what is usually inferred.

I believe L-band is capable of detecting stealth aircraft but it's not able to pin-point.

Mir wrote:I believe L-band is capable of detecting stealth aircraft but it's not able to pin-point.

Some people think the L-band radar is able to detect the rough location of a stealth aircraft, and then the X-band radar can use that rough location to guide a concentrated set of beams towards that area to accurately detect the target and guide a missile against it. This is suspected to be used in the Su-35 for example.

This is unlikely to happen and if it does it wouldn't be very useful.

They have already decided to do it to unify the parts and components between teh Su-30 and Su-35... the Su-30 essentially becomes a two seat Su-35 with all the same bits and pieces.... radar, engines, etc etc.

Simplifies training and logistics and support.

The Mig31 is really the only fighter jet/interceptor in the world that can operate L Band radars in a resolution similar to the X band radars of the average jet because its PESA radar is HUGE!!..

The Su-35 and Su-30 and Su-57 use a linear array... a single line of elements in a mounting system that fits into the leading edge of the wing.

The wing is not fixed and can be moved up and down so presumably it will be moved during a scan to look for stealthy targets (that don't appear on the main nose mounted Ka/Ku band AESA). The L band radar can't track targets but it detects targets which allows IRST and nose mounted radars to find out where to look without having a scan of the entire airspace which would light up like a lighthouse. Given precise coordinates of the reflecting stealth target the Ku band AESA can focus its full power at the target to get further information through sheer brute force.

So why use L-band radars on the wings of the Su 57?

The L band AESA in the wings of the Russian aircraft have huge elements because of the frequency they operate at so it is a single line of elements in a row along the wing that is used to send a signal. It can scan vertically by moving the surface it is mounted in... imagine having a vertical line of torches that you can manually scan horizontally looking for car reflectors in the dark... you will get hits but it is not practical for tracking... the the locational data is enough to allow you to find stealth targets and direct other sensors towards them. It is radar too so you get range and location information.

Mainly MAWS and IFF..

Bollocks. For MAWS it would be useless because it only covers the forward hemisphere, and why bother with an AESA array of L band radar elements if it is only IFF... IFF does not need to be directional... and even if it did you don't need an array of identical transceivers for that.

So what some people wrote here, that this L-band radar is used to detect stealth, is nonsense. This means that the Su-57 has the same limitations as other aircraft when it comes to stealth detection. X-band radar that stealth suppresses the most.

Search, track and missile midcourse guidance against low signature aircraft.

The Search is accurate, the track and missile midcourse guidance are speculation.

The Russians say it is to detect stealth aircraft, and I have no reason to doubt that is true.

Their ground based systems detected American F-35s on the border between Iraq and Iran from about 6,000km away so they know what they are talking about.

L band is a long wave that cannot detect shape and for a RAM coating to effect its wavelength the coating would need to be half a metre thick.

L Band waves are not redirected in a different direction from which they arrived by the shaping of the aircraft.

I believe L-band is capable of detecting stealth aircraft but it's not able to pin-point.

The Russians say it can detect but cannot track.

Some people think the L-band radar is able to detect the rough location of a stealth aircraft,

Not precise enough to fire cannon shells at, but close enough to get a missile in the vicinity of the target so its own radar or IR sensor can finish the interception.

and then the X-band radar can use that rough location to guide a concentrated set of beams towards that area to accurately detect the target and guide a missile against it.

The NEBO radar system also uses long and short wave radar together to find targets neither radar could find on its own... the signals are combined and processed to reduce the weaknesses of each radar type and maximise the advantages of each radar type.

Belisarius wrote:

Atmosphere wrote:Anyone still got the links to the PAK-FA patents?
Especially the one with the aerodynamic features.
Thanks.

http://www.su57.mariwoj.pl/su57-index.html

Links to all Su-57 patents are at the bottom of the page.

Thank you!

I believe L-band is capable of detecting stealth aircraft but it's not able to pin-point. wrote:

It can pin point the location of a low observable object if its large enough.. To get the same accuracy as a 2m diameter X Band radar, You would need it 6m large. Then it will track and search exactly like an X band radar with more range however. But it will need more power because of that wavelength.. One of the reasons why It is not particularly employed as a frequency band in the radar of a fighter jet (Fighter jet radars are already multi-band btw, they dont operate from 1 band only) is because of the size of the thing...

L Band on a Frigate or cruiser is very different.. F22 and F35 stealth is immediately 40-50% less effective in that frequency because of the massive radar.. And detection range increases..

They have already decided to do it to unify the parts and components between teh Su-30 and Su-35... the Su-30 essentially becomes a two seat Su-35 with all the same bits and pieces.... radar, engines, etc etc. Simplifies training and logistics and support. wrote:

They are not doing a L Band radar for the main search and track radar.. It is gonna have terrible resolution.. Unless they use an advanced form of SAR and inSAR where multiple radars try to simulate a higher aperture by each radar looking from different angles and triangulating the target (Very difficult to do for non-satellite based applications).. Terrible..

So what some people wrote here, that this L-band radar is used to detect stealth, is nonsense. This means that the Su-57 has the same limitations as other aircraft when it comes to stealth detection. X-band radar that stealth suppresses the most. wrote:

Its not nonsense. Its just that Russia has never envisioned the SU57 with a L band search and track radar.. L Band does get affected by RAM but to a lesser degree than X Band. Bands that are free from absorption are VHF or the under 1GHz ones.. They don't even bounce off a jet sometimes, they can go through it and get reflected by some stuff bring back a weak return signal with terrible resolution (Failing to tell a fighter jet apart from the trees if its flying a bit lower..

and then the X-band radar can use that rough location to guide a concentrated set of beams towards that area to accurately detect the target and guide a missile against it. wrote:

I dont know if you have played around with CST Suite or ANSYS HFSS but shaping that lobe is not easy.. Even computers struggle to estimate an optimal design to shape it (And you want as many narrow beams as you can fire out there). Most of the best beam shaping is through trial and error and not some straight forward mathematical formula like Electronic beam steering. So is switching between Frequency bands mid scan. Ok switching is easy but the signal processing isnt..You need to either have many oscillators working through all your preferred frequencies (Needs a lot of power) or you can just have 1 doing the phase shifting and stuff (Slow and impractical as radars need to swap frequencies in nanoseconds).. Mordern jets have multiple..

It can pin point the location of a low observable object if its large enough..

You are not understanding... radar cross section has nothing to do with the actual size of something... it is an indication of how reflective that something is.

If you create a corner reflector you can make something that reflects radar back to its source like a light reflector on the back of a car reflects back the headlights of your car.

If you decorate the front of your aircraft with corner reflectors you could have a radar cross section measured in kilometres if you wanted to.

Russia uses its old SAMs as targets for air defence training and they take things out like the HE payload and the guidance radar in the nose if it has one and so they just have a sheet metal nose which is actually quite stealthy compared to a radar invisible nose cone with a big flat round radar antenna reflecting back a big radar signal.

The Peniye system is based on the SA-6 SAM and uses three standard missiles on the standard TEL, and with a sheet metal aerodynamic nose fairing the RCS of the missile is 0.1 to 0.3m squared. With the original radar transparent nose cone the radar waves from the enemy radar go straight through and hit the flat surface where the radar antenna in the missile would be and of course radar shining back from a flat surface like that is 1m square. Putting a luneberg lens or corner reflector in the nose with the radar transparent nose cone can get a radar cross section of 3 to 5m square.

In terms of light the sheet metal fairing redirects the light in all directions so it isn't exactly bright coming back at you. With the flat surface and radar transparent dome it is like a flat shiny surface reflecting the light back, and with the corner reflector it looks like you put the reflector from a car in there... it actually looks like there is a light inside that is shining back at you.

The thing is that L band radar is not the same as the high frequency radar used to find and track targets... it is like the difference between normal visible light and heat, so stealth is camouflage paint that makes the target hard to see, but in L band the entire aircraft or object just reflects the signal... the whole thing glows and energy is not redirected in other directions because of the stealth shaping of the object.

To get the same accuracy as a 2m diameter X Band radar, You would need it 6m large.

A stealth object stands out like any other object in its field of view stands out... and the angle precision is good enough to be able to point the main radar at it and find it with a powerful burst, or the IRST could be directed at the target to find it too.

Then it will track and search exactly like an X band radar with more range however. But it will need more power because of that wavelength..

Finding stealth aircraft with an L band does not need extra power because the wavelength is too long to be redirected by the stealth shaping of the target so the entire beam sent to the target is returned to the radar antenna. At Ku or Ka band much of the energy is redirected away from the source radar so more power is needed to detect a stealth target, but with L band there is no degrading of range.

One of the reasons why It is not particularly employed as a frequency band in the radar of a fighter jet (Fighter jet radars are already multi-band btw, they dont operate from 1 band only) is because of the size of the thing...

A 2D array of elements would be a ridiculous size and would not fit well in the nose of a fighter and more importantly would take up space that can be used by a more useful radar like a Ku or Ka band set.

If you are having trouble understanding look at this... this is NEBO.



From right to left is the high frequency radar on a truck and then a low frequency radar on a truck and then high frequency and low frequency.

NEBO is the mobile version... the static version can look like this:

They are not doing a L Band radar for the main search and track radar.. It is gonna have terrible resolution..

Nobody said they were. The L Band AESA radar is a single line of elements along the leading edge of the wing, as part of the leading edge flap I believe so it can be moved to mechanically scan vertically while horizontal scan would be electronic.

I dont know if you have played around with CST Suite or ANSYS HFSS but shaping that lobe is not easy..

I am confident the Russians know exactly what they are doing...

That western audiences don't understand is honestly a good thing because if they realised how exposed western stealth fighters are going to be against Russian air defences there would be panic and then there might actually be changes and solutions that matter a damn.... but I wont hold my breath.

Most of the best beam shaping is through trial and error and not some straight forward mathematical formula like Electronic beam steering.

With the ground based NEBO system they take AESA radars of different frequencies and process their signals through some computers and can have astounding results against a range of objects.

Not ideal for very small targets, but for big targets pretending to be small like a stealth fighter or stealth bomber they are amazing.

You are not understanding... radar cross section has nothing to do with the actual size of something... it is an indication of how reflective that something is. wrote:

I meant the radar. Not the object. To get a narrower beam out of a low frequency radar you need a larger antenna physically. IF you dont do this then SAR is the next way to do it.. Triangulate the target with multiple arrays pointing at it and averaging their results (Much harder to do in real life). A smaller one will still detect a target but with terrible bearing and range discrimination.. It forms a kind of wide and blunt beam shape that shows objects close to each other as 1 object.. How close depends on the frequency band. L band isn't that bad though.. 10m should be the max. But its still bad.. For stealth aircraft with RAM and Frequency selective surfaces, Absorption Cross sections should be considered.. All Frequencies reflect the same but don't get absorbed the same.

The far left is what a small fighter jet sized L Band beam pattern would look like. Thats what you dont want. Thats what engineers spend hours trying to not have. But that's what you get when you have a tiny Low frequency radar (L band/S Band).. The far right is what happens when you go up the frequencies or up the physical size ladder of a low frequency radar.. Of course it won't end there. Lots of phase shifting and beam forming after that.. But these play a big role in that.. That is primarily why you wont find a fighter jet using L Band for its main radar.. It takes a lot of power.. Bad beam forming.. And you would need some crazy compilation of code to run the oscillator so it jumps across frequency bands in nano seconds.. No way you staying in La Band the whole time. If you value your life anyway.. Only the Mig31 can do this at the moment. But even it is not perfect..


FUN FACT: The far right pick tells you why more T/R Modules is beneficial but not instrumental. More of those pointy beams coming out of your radar is good for its range and resolution.. And being able to use Time delays to steer them all in different directions in 1 go is even better..

Finding stealth aircraft with an L band does not need extra power because the wavelength is too long to be redirected by the stealth shaping of the target so the entire beam sent to the target is returned to the radar antenna. At Ku or Ka band much of the energy is redirected away from the source radar so more power is needed to detect a stealth target, but with L band there is no degrading of range. wrote:

This is a little right but not entirely. L band radars need more power to achieve a similar resolution to X band radars. You are always gonna get more range out of L band compared to an equivalently sized X band radar. But the X band radar will know when 1 F35 is 50m ahead of another.. And would clump them as 1. The X Band radars waves get absorbed by a lot of stuff such as dense and humid atmospheres so you wont get radar returns of tree tops either..

I should add, stealth aircraft with no RAM will have negligible success against even high frequency radars.. Those kind of jets just have faceted body shapes that send the reflection somewhere else..Not entirely at least but the intensity is reduced as some of the wave still reflects back while the other deflects.. When it comes to RAM, its more complicated..L Band is also affected by RAM.. Just not like X band and higher frequencies. All frequency bands are affected by RAM. Depending ON, Yes you guessed it size!! If the beam length is longer than the radius or diameter of what its going through then there will be some return (Long wavelengths) A small L band radar will feel the effects of chemically treated Iron Pentacarbonyl too. Upsizing the radar will require more power..Its basic RF engineering, Longer wavelengths when using a specified radar size will ALWAYS demand more power. Thats why the Zaslon P800 requires 600kw and the Irbis needs like 20kw.

GarryB wrote:
The Su-35 and Su-30 and Su-57 use a linear array... a single line of elements in a mounting system that fits into the leading edge of the wing.

The wing is not fixed and can be moved up and down so presumably it will be moved during a scan to look for stealthy targets (that don't appear on the main nose mounted Ka/Ku band AESA). The L band radar can't track targets but it detects targets which allows IRST and nose mounted radars to find out where to look without having a scan of the entire airspace which would light up like a lighthouse. Given precise coordinates of the reflecting stealth target the Ku band AESA can focus its full power at the target to get further information through sheer brute force.

So why use L-band radars on the wings of the Su 57?

The L band AESA in the wings of the Russian aircraft have huge elements because of the frequency they operate at so it is a single line of elements in a row along the wing that is used to send a signal. It can scan vertically by moving the surface it is mounted in... imagine having a vertical line of torches that you can manually scan horizontally looking for car reflectors in the dark... you will get hits but it is not practical for tracking... the the locational data is enough to allow you to find stealth targets and direct other sensors towards them. It is radar too so you get range and location information.

In the whole Flanker family as well as the Su-57, aren't they mounted inside the actual leading edge flaps themselves, and not in the fixed section of the wing?  So they're function can't be just limited to the fixed position of the flaps but also as the flaps move up and down when actuated by the FBW system.  The way I understand it is that being within the operating edge flaps, they need to be able to beam & scan in whichever position the flaps are in at the time which in almost all cases, those things are down for aerodynamic reasons.  But they also move up and down especially during the aircraft's maneuvering.

These illustrations are from 2009 so things might've changed a bit by now, but I think the initial overall concept is still the same.

 


L-Band AESA Components and Integration


Figure L-band AESA general layout (Tikhomirov NIIP).




L-Band AESA Performance Modelling and Growth Potential


L-Band Array Angular Coverage
The basic array design and integration into the leading edge flap structure are well documented via a wealth of imagery produced at the MAKS 2009 event. Each array employs twelve antenna elements. Three quad TR modules each drive four antenna elements, for a total of twelve elements per array, in three subarrays. The linear array is embedded in the leading edge of the wing flap, with the geometrical broadside direction normal to the leading edge. The leading edge skin of the flap covering the AESA is a dielectric radome which is conformal with the flap leading edge shape.

The flaps must straighten out or retract to the fixed position once the arrays start beaming.  Either that or they're able to rotate and scan with the movement of the flaps.



Source.

Well bye bye 3D nozzle. I will miss it.. But at least the AL51 is looking great.

I meant the radar. Not the object. To get a narrower beam out of a low frequency radar you need a larger antenna physically.

No, lower frequency radar transmit and receive modules are bigger than for higher frequency radars. Look at NEBO photos I posted above... the AESA array for the High frequency Ku and Ka band radar looks like a solid board, while the low frequency radar looks like a chain link fence and its much much bigger in area.

Both are intended to work together over similar ranges to find targets.

IF you dont do this then SAR is the next way to do it.. Triangulate the target with multiple arrays pointing at it and averaging their results (Much harder to do in real life).

What is SAR?

My understanding of SAR is synthetic aperture radar, which involves computer processing from a single moving radar that measures the target multiple times from different locations and then collates the data it collects and processes it. Essentially it is like taking a photo while moving and then taking another photo and then taking another photo and then combining the images together so instead of a 3 megapixel camera you are effectively using 9 megapixels to collect the data and provide processed information from the result. Synthetic aperture means making the diameter of the radar bigger than it actually is. A bit like using 20 radio telescopes all together to pretend to be one big radio telescope... except they can't move so they use their different locations to simulate having a bigger radar dish.

Having lots of different radar all scanning the same area from different angles is having an IADS, but having one transmitter and multiple antenna in different locations just listening and gathering reflections... like a radio telescope array does is called bistatic radar isn't it?

How close depends on the frequency band. L band isn't that bad though.. 10m should be the max. But its still bad.. For stealth aircraft with RAM and Frequency selective surfaces, Absorption Cross sections should be considered.. All Frequencies reflect the same but don't get absorbed the same.

A 10m error in target location would be astoundingly good and easily enough to direct the nose mounted PESA (in the Su-35) or AESA (in the Su-57) to then direct a high energy beam of energy at the location to spot the stealth target and get a lock.

Ground based long wave radar used to have errors of 2-3km... which was good enough to get a flight of fighters close enough to see the enemy bombers and attack them.

The far left is what a small fighter jet sized L Band beam pattern would look like. Thats what you dont want.

My understanding of the Russian L band wing mounted radar is that it has multiple transmitter receivers... so it should just be fine...

Well bye bye 3D nozzle. I will miss it..cry But at least the AL51 is looking great.

We really don't know what that is for... they might have an increased stealth option nozzle for Su-57 and or Su-75 and S-70, while the rest just use a round nozzle with sawtooth edges for good enough stealth but less loss of thrust.

Reminder for folks: the F-22 has a one dimensional nozzle: up/down. vertical dimension.