ActionJacksonThat’s a big statement that stealth is merely a missile countermeasure (and aircraft can detect each other just fine) when we have operational pilots across the world now saying they can’t see the f-22 or f-35 in exercises at all until they have already been shot down or until they see them visually.
I think china’s edge treatments on their leading edges suggests they do actually care about the RAM too.
ActionJacksonEyeballing aircraft isn’t going to get you any kind of accuracy at all. Dr. Kopp did that in great detail with ray tracing and got erroneous results.
Care to elaborate about specifically which part of his results? Obviously absolute RCS numbers are going to be incorrect, but imo his test gave great insight into the relatively high RCS (specular) aspects of the targets based on shaping.
ActionJacksonWas just about to post the same link….
Critical spectator after F-35 pulls a hard, post stall, instantaneous 130 degree turn: “You done lost all your energy!”
F-35: “Yup” *goes vertical and accelerates*
ActionJacksonWelcome back Trident! …. though extremely odd that just as it seems we’ve finally all been treated to a 1 month holiday from KGB’s doltish contributions to the forum, you’ve suddenly returned. You don’t post on a second account to take a break from all intellectual and social accountability from time to time do you? 😉
Can be dealt with, albeit at a weight penalty for the more elaborate treatments and coatings required
Though the removal of the cavity is featured on the YF-23, F-35 and both chinese stealth fighters (and on the Iranian monstrosity… but let’s not bother going there). F-22 has a cavity too, but covers a much smaller area than the Su’s. Negated it’s advantage over the cockpit leading edge design of the YF-23 perhaps?
In a word – blocker. Why is this old hat still a point of contention in the first place?!
But will a blocker prevent IR coming straight back out the front of the intake? TBH adding that particular pic was done with tongue in cheek mostly, I’m waiting to see the final solution for that myself and whether blockers become a real, viable solution in future Gen 6 fighter concepts. The child’s cartoon “elephant in the room” image felt fitting for the more primitive audience I knew would explode over it… and predictably, it exploded.
Even allowing that the IRST is supposed to rotate rearwards to expose a thickly RAMed back face, it forces a choice between stealthy passive sensor and stealthy airframe configuration on the pilot.
Exactly. It doesn’t make sense hanging those radar beacons from a stealth airframe. It’s a little more protected from IR missiles only to be so much more exposed to more prevalent radar guided missiles and aircraft. In combat against stealth aircraft, the front IRST is going to be operating pretty much full time, the whole stealthy back surface solution seems utterly pointless. So the OLS ball’s surface is either:
– Radar transparent, exposing the metal and glass components inside or;
– Conductive and reflective, exposing the entire sphere to specular reflection directly back to the source radar
Guess we’ll see how LM handles the F-35’s DIRCM solution a few blocks down the track.
As pointed out a while back when this subject first came up, that’s likely related to wind blast requirements in aircraft where the entire canopy (including windshield) is jettisoned rather than LO. Ever wondered why the F-22 & F-16 Block 40/42 (with the wide-angle screen) have such beefy frames?
Not totally sure what you’re referring to here… the reduced amount of clutter in the front of the cockpit being because of ejection safety instead of LO? The F-35 doesn’t jettison the whole canopy either. Det cord blows out the rear half of the canopy only.
I’m also not seeing the RAM on the F-35 canopy frame?
Its so difficult finding a decent picture of this (but I’ve seen one previously where flash photography was used), but the one below gives an indication. The front facing surface of the frame is canted away from a head on radar. The canted component also seems to be made from a different material to the frame itself (evident when looking at the frame from the outside of the canopy). The canted surface has some flexible, rubber-like material attached to it (arrow points to it in picture) that would only really be practical in that location for radar absorption, reducing solar reflection or both.
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Why are we talking about other aircraft in this thread
….because we are comparing stealth implementation techniques and I consider the F-35 the most modern and refined benchmark. There are techniques used on the F-35 that weren’t on the F-22. The Su-57’s viability over the coming decades rests almost solely on it’s ability to spot the F-35 and to a lower degree the F-22 before it itself is detected. Any issues now need to be solved before the aircraft is “useful” in it’s primary role, so identifying these and tracking their progress helps get an indication of when the Su-57 is “actually” approaching service readiness as more than just a deterant.
ActionJacksonPlenty of high bandwidth HPAs available at Wolfspeed RF (formerly Cree). 1-18GHz are fairly common and the have nice little 70W for all your jamming and high bandwidth needs.
In other developments Cree have now released an extremely tiny uhf Radar amplifier capable of a whopping 900W output. 900W per TR module!
https://www.wolfspeed.com/cghv1j070d
These guys are doing amazing stuff still and their GaN product line is huge. It’s good to see other companies have finally progressed past prototype phase though, just not sure they’ll be disrupting the market any time soon.
ActionJacksonNice to know that the OLS and its inside is then invisible if rightly treated…
I think you mistake travelling waves caused by incident beams hitting a surface at a low angle vs direct illumination, front on.
And for B-2 ?
a) Does not have to go head to head against fighters and b) is not as stealthy as the F-117, F-22, F-35 front on. Also, it’s designed primarily to penetrate VHF, UHF, L-Band protected areas where small features such as window’s etc are not as important due to the wavelength.
I must say it’s refreshing being in this thread now with KGB on ignore, it’s done wonders to level of the post I read in here.
ActionJacksonYou mean like these ?
You know that’s all inside the cockpit right? The canopy’s a single, continuous piece of glass. Surface waves travel on… surfaces.
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ActionJacksonSee the screen?
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The YF-23 was an initial protoype and would most certainly have changed in design during development. Nobody ever said it had a better frontal RCS specifically than the YF-22, just that it was better overall which can be seen clearly by it’s way more highly canted sides and hidden exhaust. The F-22’s canopy leading edge is different to the YF-22’s.
ActionJacksonThat is nothing to do with curves, but surfaces and edges which point directly at the source radar. Whether it was straight or curved, no difference, it is not sharply angled. It is a simple fact that that having very little forward facing edge and diverting most of the echos well away from the source radar is a better solution.
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ActionJacksonI think you’ve missed something, my post was not related to curves at all.
BTW it’s not my posts that get threads removed, just the children who lose their temper in frustration at themselves because they can’t form a mature, coherent and informed argument. Hence why I now backup my posts in case the threads delete. Some people find them informative as they based on science fact rather than fantasy.
ActionJacksonIf there was only one way to do stealth, all planes would look like an F-117 …none would have curves like the B-2, the F-35 or the F-22…and the Su-57
Why would they not have curves? As long as the curves are gradual, the angles low, and as long as the aircraft can be affordably maintained, everyone would build the same thing, and it would be far stealthier than the F-117….oh wait…
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nfortunately the stealthness is not solved by a simple fuselage curve, a HUD reflecting the electronic waves or an outgrowth not inclined enough. The material used, its composition, its coating, its degree of absorption/reflection, …, are all elements to know to define the degree of stealthness.
Good shape plus materials will always beat just materials, not disputable.
ActionJackson….cont
Although the aircraft’s canopy is covered in a very slightly attenuating, but conductive film, some radar waves do still penetrate the canopy and can reflect off objects inside. This image shows a number of cockpit features which will cause signal return back through the canopy. The HUD and the components in front of it, rear view mirrors, the helmet material…all contributors to RCS. Another side note: Also note the OLS. From the aspect this photo was taken, the feature presents an undeniably massive challenge for side aspect RCS.
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One of the features of the F-35’s and future US aircraft is the lack of a HUD and clean cockpit layout.
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The pilot’s helmet is made of carbon fibre (known for radar absorbing properties) and the canopy frame, even though concealed internally is faceted away from the source radar and is further concealed from the front behind a very thick piece of foam-rubber-like RAM. All other metallic frame components in the photo are concealed from site of incoming radar.
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In summary: Low, frontal observability requires meticulous attention to detail, but also must be affordable by operators who choose to adopt aircraft with it as a feature. The F-35 program is such a large, multinational program with an equally as large amount of support infrastructure. While building the aircraft with a lot of additional care may cost a bit extra in procurement, it’s the support costs of high end stealth over time which would be absolutely untenable without modernised maintenance systems that reduce man hours maintaining the aircraft’s stealth features. The massive F-35 program has invested billions in tooling and robotic systems that are used in depots throughout the world.
For relatively low GDP countries such as Russia that are going it alone with their own, much smaller stealth fighter programs, compromises must be made to reduce the amount of required stealth maintenance infrastructure while at the same time maximising aircraft availability rates. This is why Russia built the aircraft to their economic and tactical needs. The Su-57 is an affordable stealth fighter which is suited to defensive air to air operations over long distances unaided against the current European gen 4+ fighters.
Against emerging and current 5th gen class fighters, it will be almost totally depend on Russia’s large IADS and jamming systems to try to approach parity in combat. It’ll not be produced in large enough numbers to justify the massive investment Russia needs to make in maintenance infrastructure to bring it up to the next level – full frontal VLO or ~-40dBsm or better frontal RCS
ActionJacksonThe Su-57’s Frontal RCS
Cockpit and Aircraft Nose
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Travelling wave echo occurs when waves of the incident radar beam meet a surface at a shallow angle and run along the surface until they meet an object, different material, surface discontinuity or surface edge. They then bounce from the object/material/edge at an angle dependant on the incident angle. If they bounce from an object perpendicular to the direction of propagation of the waves, then the waves are bounced directly back along the path they came (towards the source radar).
In the case of an Su-57 flying towards and adversary’s radar there are a number of areas on the top of the aircraft which will cause travelling waves to bounce directly back to source. This occurs because the features that travelling waves reflect from are all at a normal to the aircraft’s longitudinal axis.
The diagram below shows how the OLS, canopy leading edge, canopy frame and the rear of the canopy will cause a large proportion of travelling surface waves to reflect back in the direction of the source radar. Green arrows represent the original direction of the travelling surface waves from the source radar and red are the echoed return. While the amount of energy returned from echoing waves is rather small compared to return from specular reflection (such as from the metallic pitot tubes seen above), undisputable science fact dictates that the features shown in the Su-57 top view below could be handled better to further reduce the aircraft’s overall frontal RCS.
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A sample of how other manufacturers handle surface waves travelling down the aircraft’s length can be seen in the image below. Multiple layers of faceting leading up to the canopy glass surface, the lack of a frame to echo the waves and finally a faceted trailing edge cause the surface waves to reflect off at an angle that is consistent with the aircraft’s plan-form design. The angles of the F-35’s facets are designed to direct all reflected return (Specular and travelling waves) to a limited number of angles.
The sensors on top of the aircraft are built into a gradually curving surface, but generally that will not be an issue as surface waves tend to stick to gradually and continuously curving surfaces (tip: the sky is blue because EM energy at the wavelength of blue light curves around drops of vapour in the atmosphere).
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The image below shows the faceting on the F-35’s canopy leading edge nice and clearly.
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Other aircraft also adopt this principle.
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This one too. I love this picture of the F-22 which is long overdue for a re-coat. The state of the surface really allows you to see the faceting and angle consistency in the magnetic RAM surface and fuselage features that are usually painted over.
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Even the Iranians sort of have it…. but oh my gosh, what a beauty :stupid:
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In summary in regards to travelling wave return:
There can be no dispute, based on real physical laws, that angled surface edges are preferred to surfaces at a normal to the aircraft axis for the purposes of reducing surface wave return in the context of frontal aspect stealth. Materials will go a long way to reducing radar return from poorly angled surfaces, but materials plus faceting will always be far superior.
According to the Su-57’s canopy’s manufacturers, the surface coatings of the Canopy and presumably the 101KS-V (judging by it’s colour) are coated with a combination Idium-Tin Oxide and Gold (and some other substances to make it a particularly thin film). It is a conductive but slightly absorbent film that reduces the radar return of the canopy material itself by 40-60%.
The OLS’s transparent surface helps hide the highly radar reflective, metalic components and lens of the IRST within (observable while it’s being operated… ie. all the time). If the surface happened to be completely radar transparent then the OLS’s internal components, having an RCS many dozens of times larger than the entire frontal aspect of most stealth aircraft would be exposed.
101KS-V
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On a side note, the aircraft also has two other spherical pods under the nose and on it’s spine for it’s IR countermeasures. These do certainly seem to be a major RCS issue as can be seen by their internal components. It seems these cannot be coated with lossy material as they would potentially melt when in use.
101KS-O
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…..to be continued
ActionJacksonWhen you’ve obtained multiple bearings to a signal source from known locations over a short period of time then you have located the origin of the source – in real time to a small region of uncertainty.
Who knows the means of locating the F-22’s or whether it was real time or after analysis of mission data, it’s largely irrelavent. For all we know they could have rolled a UHF radar up to the test area to track the F-22’s movements and reactions…. simple fact is, in multiple translations on translation tools, we get this….
“We were probably able to clarify a number of possible and accompanying data on the ability of the F-22 and F-35 to detect our aircraft in the short-term stay of our Su-57s in Syria in February this year – telemetry provided a significant reason for their improvement,” – said V.Gutenev.
to detect our aircraft – Unambiguous, nothing lost in translation
telemetry provided a significant reason for their improvement – Same, also specific
Then we get the full treatment in this thread of the typical deny, deny, discredit the source, deny, try to interpret it in 200 completely unrelated ways, deny, discredit…etc by the local bots. Enough to convince me it’s right on the money and worthy of tipping to defence media to see if they want to run it.
I’ve been saying it for a long time, “stealth” is not “just stealth”. There’s varying degrees of observability between LO to true VLO. The question of which aircraft would more often prevail in an encounter comes down to exploitation of the radar max range equation. If aircraft A has a lower RCS from operationally relevant angles (noticed some of the uneducated in the last thread were talking about the RCS of the very bottom of the aircraft… clueless) and a better radar than aircraft B then more often than not it’s going to get the first shot in an encounter, immediately putting the opponent on the defensive where their SA and low RCS quickly disappear.
At a certain point in stealth design, it comes down to tiny details to get to actual VLO. Turning of screws to a particular angle to prevent the most minute amount of specular return, removal of a canopy frame causing surface discontinuity diffraction, stealth shaping of the inside of the cockpit (as well as a small jammer built “inside” the cockpit at a concentration point), extreme sharpening of all leading edges, closing of airgaps, removal of cavities between the airframe and intakes, mm perfect laser directed application of ram strips to the skin to consistently achieve the highest level of effectiveness.
Meanwhile….
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1 – surface discontinuity, corner reflector – causes both specular and diffraction return to source radar … forget the ram, a recent video on Su-57 canopy treatment only stated a 60% reduction in RCS from the metalized treatment
2 – surface discontinuity at a normal to the aircraft’s axis causes diffraction return to the source radar
3 – surface discontinuity at a normal to the aircraft’s axis causes diffraction return to the source radar
4 – HUD (inside) – specular return through canopy
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1 – cavity – causes resonance
2 – cavity – causes resonance
3 – cyclindrical pitots – massive specular return
4 – large levcon cavity – causes resonance
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1 – cavity, surface discontinuity – causes diffraction and resonance – not blended with airframe
2 – no sawtoothing and pinching of control surface edge, cavity – causes resonance
3 – fat, rounded leading edges – causes high specular return compared to extremely sharp (1mm diameter) leading edges
4 – cavity – causes resonance
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1 – Multiple sources of specular and surface discontinuity return – resonance depending on wavelength
2 – massive surface discontinuity almost at normal to axis – the gaps in these areas are quite large, inches in size
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Almost forgot… radar disco ball/infrared headlamp
ActionJacksonThe thing is, if you are interpreting this correctly then such a scenario actually benefits the Russians. This implies that the Russians know that they were likely detected. There are two ways this could have happened. 1) F-22s and/or F-35s placed a radar lock on the Su-57. 2) The Su-57 allowed itself to approach the known threat radar to were it would have a reflected SNR (for that specific test aircraft) high enough so that detection was likely. Then, the Russians used target motion analysis to gain the precise distance to the US stealth platform. The Su-57 could have done this by itself by performing a rapid maneuver or they were also using a second platform to track the USAF aircraft’s emissions. Either way you get two bearings from two known locations, and where they cross is where your target is (the whole principle of TMA).
This benefits the Russians because 1) it proves that their Himalayas system can keep up with our low probability of intercept radars. 2) The radar signature of the production variant of the Su-57 will change drastically from the test aircraft sent to Syria due to final touches on the absorbent coat, ITO treated canopy, product 30 engines, etc. This means that the RuAF has gained known signature information on the F-22 and F-35 and can develop engagement and avoidance tactics for the production model to use. The USAF did not gain similar useful information from the encounter and can only use guesswork when formulating tactics.
….. or as suggested from the “telemetry data” (his comment suggesting collected data being analysed post mission) they performed analysis of recorded signal data from multiple, distributed receivers. After months of post mission data analysis were able to detect the transition of the source radar from search to lock mode (prf and power changes) from an apg-79-like radar (a radar they should be familiar with and have the ability to identify due to unstealthy platform)
With enough signal data from multiple receivers, plenty of compute power to detect a main lobe and correlate it with much lower powered side lobes arriving at different receivers, they were able to use time of arrival techniques to determine range from the sources.
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