Intake design and general stealth discussions

[pegasus]

and RCS make a big difference whether your radar is powerful or not
View attachment 620993

Pt is a variable, basically it says will depend in the radar, σ = radar cross-section [m²] is another variable, it is not fixed thus the illustration you use will depend on the radar nothing is fixed

In theory, the RCS of some simple objects, such as a perfect sphere, can be
well defined. In practice, most targets are rather complex objects and their RCS
usually fluctuates considerably, as they move with respect to a radar. In fact, the
monostatic or backscatter RCS depends on the following

Position of radar antenna relative to target
 Angular orientation of target relative to radar antenna
 Frequency of the electromagnetic energy
 Radar antenna polarization.


For the F-35, the approach was the construction of a l.o. aircraft, taking seriously
into account the cost parameter. Therefore, in the frame of cost reduction, some
capabilities were “sacrificed”: RCS is really low in the X-band (8 – 12 GHz) and in
the Ku-band (12 – 18 GHz), while it is not so low at lower frequency bands. The
scope is the break of the killing chain: even if the F-35 is detected by surveillance
radar, it will not be easy to be engaged by a fire control radar, which usually operate
in the X or Ku bands. On the other hand, the F-22 presents a lower RCS from all
aspects and at more frequency bands, of course at a considerably higher cost

The production F-35 is expected to present a higher RCS than the prototype
X-35, since more volume was required for the internal equipment and armament bays.
The curves of the redesigned fuselage will incur an RCS increase, from some certain
directions. It was calculated that the RCS will remain very low from the frontal sector
and more precisely from a sector of 29ο in front of the aircraft. However, the RCS will
not be so low from the lateral aspect and also from the rear aspect. The whole
behavior deteriorates at lower frequency bands

Very low frequency band radars, for medium to high altitude
surveillance: as the frequency decreases, the wavelength increases and becomes
comparable with major parts of the aircraft. Thus, scattering enters the resonance
region, exhibiting a higher Radar Cross Section (RCS), at least momentarily. Also, the
Radar-Absorbent Materials (RAM) are not very effective at lower frequencies. For
these reasons, radars operating, e.g., in the VHF band, are expected to see a l.o. target
at a longer distance with respect to “conventional”, higher frequency radars,
transmitting in the L or S-band.



https://www.researchgate.net/publication/259503614_Low_Observable_Principles_Stealth_Aircraft_and_Anti-Stealth_Technologies

 

[Fluff]

Please don't talk to me, im not here.

 

[kaiserd]

Given above you do know that while the F-18E/F/G and F-22 don’t technically have DSI they do have fixed geometry inlets of a different design type?
Hence not really very relevant to discussion around DSI or variable geometry inlets. And you’ve certainly made no apparent attempt to make them relevant or relate them back to DSI or variable inlets. Or form any particular approaching-coherent argument or point.
Apart from vomiting almost completely irrelevant techno-babble at anyone who shows an interest.

The intrinsic “stealth” of any particular engine inlet approach is tied up with the overall integrated aircraft design (with the exception of the designs where you can see the fan straight down the inlet), the devil is in the detail.
DSI are not somehow flawed from that perspective and dependent on their detailed design may lose less in performance loss versus variable inlets than more traditional fixed inlets, especially if the variable inlets have to make their own compromises to be a integrated into a stealth design.
Variable inlets probably have a tougher time in regard to “stealth” integration but perhaps if combined with “inlet-blockers” like seen in the F-18E then some compromise can be met between maxing performance while successfully integrating into a “stealth” design.
Hence it’s not some great philosophical argument except for those who are trying to make it so.

 

[quellish]

You can not prove the radar range formula say stealth means invisibility,

Actually, that is exactly what it says.
The radar range equation tells you the distance at which the target can be detected. When the target is farther than that, it is undetectable - invisible. It disappears into the noise. This is an important concept.

the only thing i said, is the only real limitation is the electricity an aircraft can provide to its radar,

No, there are as many limitations as there are variables in the radar range equation. Antenna efficiency is a big limiter. Increasing antenna efficiency has a higher payoff than increasing power. Decreasing the system noise would also help quite a bit, and increasing the power actually increases the noise significantly - effectively making the target harder to detect!

but ground radars do not have such limitations and aircraft work with

Ground radars are still limited by the laws of physics and what is practical to manufacture and operate. You can power your ground radar with a fusion reactor and pump more watts through it but you're going to start melting components long before the detection range is increased by any significant amount.

networks, to exemplify it, imaging you have a hall with many lamps, each light is helping you to see, passive radars basically use that, any frequency they are using to see.

And modern VLO aircraft are also optimized for bistatic and "networked" radars.

 

[pegasus]

Actually, that is exactly what it says.
The radar range equation tells you the distance at which the target can be detected. When the target is farther than that, it is undetectable - invisible. It disappears into the noise. This is an important concept.



No, there are as many limitations as there are variables in the radar range equation. Antenna efficiency is a big limiter. Increasing antenna efficiency has a higher payoff than increasing power. Decreasing the system noise would also help quite a bit, and increasing the power actually increases the noise significantly - effectively making the target harder to detect!



Ground radars are still limited by the laws of physics and what is practical to manufacture and operate. You can power your ground radar with a fusion reactor and pump more watts through it but you're going to start melting components long before the detection range is increased by any significant amount.


And modern VLO aircraft are also optimized for bistatic and "networked" radars.

you know what, i do not believe you, the Sun show us there are not such limits,


In fact math too




this graph shows a tendency to growth to the infinite small to the infinite large


Second root graph



same to the second root graph, as long as you increase power density that graph will always go up, in fact fourth-root power function graph, grows slower but will go to infinity simple because X can run to infinity, Pt can run to infinity, thus Rmax can run to infinity




Thus you technical jargon pretty much is not proven by Math.




Pt can run to infinity, and as the wavelength gets longer the target RCS grows.

Now are real problems that limit radar technology? of course, but the radar equation does not limit the detection of stealth targets, RCS is not fixed First because aircraft have fixed sizes, a 20 meter F-22 or J-20 or whatever, has also fixed geometry, plus a detail you forget in your concept
their RCS
usually fluctuates considerably, as they move with respect to a radar. In fact, the
monostatic or backscatter RCS depends on the following

1-Position of radar antenna relative to target
2- Angular orientation of target relative to radar antenna



Now are there economic limitations to radar networks? yes, stealth makes the military budget more expensive, so Stealth can limit the radar network by over spending too much money, yes stealth is good to bankrupt militaries, but our friend the sun proves you are wrong

 

[quellish]

Pt can run to infinity, and as the wavelength gets longer the target RCS grows.

No, the RCS of the target does not grow as the wavelength gets longer. RCS is independent of the physical size of the object. The electrical size of the object and its impedance matters, but the physical size can be completely independent of that.

Now are real problems that limit radar technology? of course, but the radar equation does not limit the detection of stealth targets,

Yes, it does. That is exactly what it does - it is a model of how the detection range changes with a change to the variables of the equation. One of those variables is the RCS. The other variables are characteristics of the radar.

RCS is not fixed First because aircraft have fixed sizes, a 20 meter F-22 or J-20 or whatever, has also fixed geometry, plus a detail you forget in your concept
their RCS
usually fluctuates considerably, as they move with respect to a radar. In fact, the
monostatic or backscatter RCS depends on the following

If you were to look at an accurate polar plot of a very low observable object you would see that the RCS is very, very low through more than 99% of the plot. And in the other 1% there are "spikes" - which are still low when compared to an object not engineered for observables, and this 1% covers a very small percentage of the possible viewing angles.

but our friend the sun proves you are wrong

I do not understand what point you are trying to make by introducing the sun to a discussion of radar. Please elaborate.

 

[kaiserd]

Unfortunately this is looking very much like trolling or lunacy (if it was ever anything better than that it has now devolved to this point).
Either way probably best we all now stop feeding “it”.

 

[pegasus]

No, the RCS of the target does not grow as the wavelength gets longer. RCS is independent of the physical size of the object. The electrical size of the object and its impedance matters, but the physical size can be completely independent of that.

If you were to look at an accurate polar plot of a very low observable object you would see that the RCS is very, very low through more than 99% of the plot. And in the other 1% there are "spikes" - which are still low when compared to an object not engineered for observables, and this 1% covers a very small percentage of the possible viewing angles.




I do not understand what point you are trying to make by introducing the sun to a discussion of radar. Please elaborate.

Look, you have to be realistic, the equation does not limit detectability as you are saying, RCS does grow with the wavelength, it is called resonance, Ronny even posted that diagram many many times. in fact i posted an article that says that


Very low frequency band radars, for medium to high altitude
surveillance: as the frequency decreases, the wavelength increases and becomes
comparable with major parts of the aircraft. Thus, scattering enters the resonance
region, exhibiting a higher Radar Cross Section (RCS), at least momentarily. Also, the
Radar-Absorbent Materials (RAM) are not very effective at lower frequencies. For
these reasons, radars operating, e.g., in the VHF band, are expected to see a l.o. target
at a longer distance with respect to “conventional”, higher frequency radars,
transmitting in the L or S-band.


https://www.researchgate.net/publication/259503614_Low_Observable_Principles_Stealth_Aircraft_and_Anti-Stealth_Technologies

The article is written by the greek military

So there you show you are wrong


Radars today use something similar to AESA but passive using different sources.

Experimental German radar 'tracked two U.S. F-35 stealth jet for 100 MILES' after lying in wait on a pony farm to catch them flying home from airshow

• Radar is designed with sensors and processors capable of tracking F-35 jets
• It works observing electromagnetic emissions in the atmosphere
• Then it will read how signals are bouncing off airborne objects
• German radar maker said the system tracked two US jets for nearly 100 mile

https://www.dailymail.co.uk/science...5-stealth-jet-100-MILES-hiding-pony-farm.html

their RCS
usually fluctuates considerably, as they move with respect to a radar. In fact, the
monostatic or backscatter RCS depends on the following

1-Position of radar antenna relative to target
2- Angular orientation of target relative to radar antenna


in fact this means that if a radar is exactly bellow to F-22, its wings and aft tail will send a very strong signal to the radar, why? because fluctuates means RCS grows or reduces so you are totally wrong simply using concepts without really thinking what they really mean





right below the F-22 its wings act like the flat plate in the third place from top to bottom

or like the following illustration


So if the radar is below the F-22 its RCS will increase that is the reason F-22 has to plan its flight route

 

[Ronny]

LM Aeronautics JSF Design Adopts DSI
The DSI concept was introduced into the JAST/JSF program as a trade study item in mid-1994. It was compared with a traditional "caret" style inlet. The trade studies involved additional CFD, testing, and weight and cost analyses. The new inlet earned its way into the JSF design after proving to be thirty percent lighter and showing lower production and maintenance costs over traditional inlets while still meeting all performance requirements.
https://www.codeonemagazine.com/article.html?item_id=58
System-level trade studies were performed to quantify the weight, cost, and benefits of the DSI, compared to more conventional inlets (e.g., F-22 and F/A-18E/F caret inlet systems). In these studies, a 30-percent inlet weight reduction was estimated for the DSI, relative to the reference caret inlet. The largest contributing factor was the elimination of the bleed and bypass systems. Studies performed by other ACIS contractors [25] indicated similar savings for diverter-less/bleed-less systems

https://www.lockheedmartin.com/content/dam/lockheed-martin/eo/documents/webt/F-35_Air_Vehicle_Technology_Overview.pdf

The short test program, starting in 1996, proved highly successful with the modified F-16 tested at all points of the flight envelop up to Mach 2. The tests demonstrated comparable flying qualities to the standard F-16 at all angles of attack and sideslip. In-flight engine restarts and afterburner lights were achieved without failure. The DSI test flights validated the aerodynamic properties of the inlet, which were further proved in testing on the F-35.
To test their theoretical results, Lockheed Martin modified a Block 25 F-16, serial 83-1120, with what is called a “Diverterless” Supersonic Inlet or DSI. The short test program, starting in 1996, proved highly successful with the modified F-16 tested at all points of the flight envelop up to Mach 2. The tests demonstrated comparable flying qualities to the standard F-16 at all angles of attack and sideslip. In-flight engine restarts and afterburner lights were achieved without failure. The DSI test flights validated the aerodynamic properties of the inlet, which were further proved in testing on the F-35.
https://static.dvidshub.net/media/pubs/pdf_34264.pdf
This is a Master Thesis done at the Swedish Defence Research Agency with the purpose to design and investigate how different geometries of a compression surface integrated with an intake affects the performance such as distortion, boundary layer diversion, pressure recovery and deceleration of speed. A successful design, such as that on the Lockheed Martins F-35 Lightning II, shows that a Diverterless Supersonic Inlet (DSI) compared to a conventional intake can reduce the weight, and weight is the primary driver to reduce cost and increase performance of a fighter aircraft.
The diverter separates the inlet from the fuselage and the boundary layer, but it is a design feature causing the inlet weight and drag to increase and with higher maintenance requirements. It is also a negative factor when it comes to radar issues. Boundary layer bleed is a frequently used technique where the boundary layer is diverted by suction through small holes in the structure. Bleed systems can be fixed or movable. Although these techniques are fully functional in an aerodynamic sense, they are complex and add weight and cost into the system.
http://www.diva-portal.org/smash/get/diva2:221/FULLTEXT01.pdf
These three types of loss are illustrated in the inlet shown in figure 2.3: There is the frictional loss due to the thin attached boundary layer associated with on the internal surface of the cowl; the turbulent loss due to the presence of a separation bubble on the floor; and the shock-loss due to the shock which is required to decelerate the flow from a supersonic to subsonic velocities.
2.5.3 The need for multi-shock inlet designs The way to reduce the large stagnation pressure losses associated with the Pitot inlet at high M1 is to introduce multiple shock waves into the inlet system (such as the inlets shown in figures 2.5b–d). The advantage of this approach is well illustrated in figure 2.8, which shows the variation of obtainable pressure recovery using a two and three shock system respectively. These results are based on simple planar shock theory (see Equations, tables and charts for compressible flow by Ames Research Sta↵). It can be seen that big improvements in pressure recovery are achievable using simple compression ramps upstream of the inlet cowl. For example, at Mach 2.5, with a Pitot inlet ( = 0) the recovery is 50%, with a single compression ramp this can be increased to 75%, and with two ramps this can be increased to 87%. The advantage of this multi-shock approach was first noted by Oswatitsch (1944).
https://core.ac.uk/download/pdf/42337454.pdf

The advent of supersonic aircraft powered by airbreathing engines opened up a new set of challenges for intake designers. A rule of thumb often used is that 1% pressure loss reduces thrust by 1%, but it became clear early on that the thrust loss caused by pressure losses in supersonic flight increases nonlinearly. For example, at a flight speed of Mach 2.2, a typical engine losing 8% of the freestream total pressure through the intake will suffer a reduction in thrust of 13% and a 5% increase in fuel consumption [9]. Since the mid-1950s, when this first became evident, a tremendous amount of research effort has gone into the study of supersonic intake pressure recovery and drag

Tradeoffs in Jet Inlet Design: A Historical Perspective András Sóbester∗ University of Southampton, Southampton, SO17 1BJ Hampshire, United Kingdom
4.1.1 Caret Inlet
The caret inlet technique has been understood as an academic concept for many years (Seddon and Goldsmith, 1985), but was not matured to a realistic engineering design until the 1980s. The primary trait of caret inlets is a pair of oblique compression ramps that generate a 2‐D flow field and co‐planar shock waves at the supersonic design point. Primary advantages of the caret inlet are efficient supersonic flow compression (as with the F‐14 or F‐15) and swept inlet edges that can be aligned with the aircraft planform. The challenge with the caret inlet lies at supersonic, off‐design conditions where the shocks generated by the two ramps are no longer co‐planar, resulting in shear layers and potential distortion and inlet instability. The caret inlet concept was adopted for both F‐22 and F/A‐18E/F. Design and development of the F/A‐18E/F inlet is discussed in Hall et al. 1993.
However, inlet characteristic airflow may be significantly greater than the demanded airflow. A bypass system provides a means to spill the excess airflow efficiently without impacting the inlet aerodynamic stability. Bleed and bypass systems typically exhaust the air on the upper surface of the vehicle in a location with a favorable local pressure. On occasion, diverter, bleed, or bypass airflow is utilized as a secondary air source for heat exchangers, ejector nozzles, or other such functions.
Various research efforts were undertaken to mature the bump inlet concept into a practical design, including a flight test effort on an F‐16 that lead to incorporation of such an inlet on the JSF X‐35 concept demonstrator aircraft and production F‐35 aircraft (see Hamstra, McCallum and McFarlan, 2003; and Hehs, 2000). This particular design, known as the diverterless supersonic inlet, integrated a highly three‐dimensional bump compression surface with a forward‐swept cowl. This combination produces a pressure gradient that diverts the majority of the boundary layer and provides a stable interaction between the inlet shocks and remaining boundary layer, eliminating the need for both boundary layer diverter and bleed systems. A diverterless inlet concept was also employed on the JSF X‐32 demonstrator.
https://onlinelibrary.wiley.com/doi/full/10.1002/9780470686652.eae490
Engine inlets for supersonic aircraft have complex aerodynamic requirements based on Mach number and other flight conditions. Fixed inlet geometries typically have highest efficiency at one specific Mach number and flight condition. Operation at other speeds or flight conditions results in degradation of the aerodynamic performance or efficiency of the inlet. To allow flight at varying Mach number, mechanical systems to adjust the capture area and ramp geometry of the inlet may be employed to increase efficiency. An existing solution to a variable ramps and variable capture inlet is the F-15 Eagle produced by The Boeing Company. This inlet system is highly efficient and is recognized as an optimized inlet design. However, later-generation fighters require unique shaping where the inlet aperture edges are highly swept. In such aircraft a caret-type inlet system is employed. Examples of aircraft employing such inlets are the F-18E/F Super Hornet produced by The Boeing Company and the F-22 Raptor produced by Lockheed Martin. These inlets are fixed geometry inlets and were designed for optimized operation at a particular flight Mach number. At off-design Mach numbers, a fixed-geometry inlet system may not provide the best shaping to maximize pressure recovery. In addition, because the inlet capture area is fixed, the inlet tends to capture more mass flow than the engine needs at lower speed than at the inlet sizing condition. As a result, the excess airflow will have to be spilled or dumped through a bypass; both of which will create additional inlet drag. Because the F-15 inlet system is not a caret-type inlet with the highly swept edges, it is not employed on current-generation fighter aircraft.
It is therefore desirable to provide a variable inlet which maximizes pressure recovery across the Mach envelope range to obtain higher pressure recovery at the engine face for maximizing thrust and fuel efficiency and to minimize inlet spill drag to maximize the propulsion system net propulsive force, thereby maximizing aircraft performance. It is also desirable that the variable inlet operate in an efficient manner without generating additional complexities such as opening gaps that will require more additional mechanisms or seals for closure.
http://www.freepatentsonline.com/9874144.html

Persus, just because DSI is lighter, easier to maintain and cheaper to produce than others kind of inlet, doesn't mean it can't also have lower RCS compared to other kind of inlet. Those advantages are not mutually exclusive

http://www.garteur.org/Technical%20Reports/AD_AG-34_%20Phase%201_TP-129_OPEN.pdf

The DSI structure complexity is greatly reduced by the removal of moving parts, a boundary layer diverter and a bleed or bypass system thus decreasing the aircraft’s empty weight, production cost, and requirements of maintenance-supporting equipment. Furthermore, by eliminating the surface discontinuity of the diverter, the forward sweep cowl lips and the S-shaped duct, which house the mental blades within the engine’s compressor, the bump can efficiently decrease the RCS. The DSI has been the focus of renewed research after initial NASA work in the 1950s. Simon et al studied an external bump inlet in a direct comparison with a traditional two-dimensional compression ramp. It was determined that the bump inlet outperformed the ramp inlet over a range of Mach numbers from 1.5 to 2, with both surfaces employing boundary layer bleed.
.....
This design is called Diverterless Supersonic Inlet (DSI). The pressure field in the vicinity of the bump compression surface shows positive pressure gradients away from the bump, which effectively blow the upstream boundary layer away from the inlet.

This design has several advantages compared to the diverter. It decreases the inlet weight, since the structure becomes less complex and it has no moving parts therefore requiring less maintenance. This further reduces the cost of the aircraft and is better concerning radar cross-section.

Diverterless Supersonic Inlet (DSI)

www.globalsecurity.org

This pattern is originally in Chinese so may be slightly harder to understand

DSI inlet (also known as non-layer separated supersonic inlet channel, English name DiverterlessSupersonic Inlet, abbreviated as DSI inlet) are raising in popularity in recent years . Because it eliminates the conventional supersonic inlet boundary layer remover, but instead rely on a pressure inlet port lateral compression gradient driven type front surface boundary layer to the outer edge of the overflow inlet port technical solution, so that supersonic inlet while maintaining the total pressure recovery coefficient of performance parameters of intake prerequisite substantially constant, simplifying the structure, reducing the weight, reducing manufacturing and maintenance cost; and because there is no attachment surface with strong RCS signal source across the inlet, it greatly improved supersonic inlet RCS stealth performance. For these reasons, DSI are ideal intake port means for hypersonic vehicles aspirated engine powered device. On the F35, and JlO modifications and other new aircraft it has been applied widely

https://patents.google.com/patent/CN204755085U/en

 

[Ronny]

Pt is a variable, basically it says will depend in the radar, σ = radar cross-section [m²] is another variable, it is not fixed thus the illustration you use will depend on the radar nothing is fixed

You know what is fixed? the ratio.
You can make your radar more powerful, but your enemy can also make their jammer more powerful. However the detection range always depends on the signal/noise ratio, which stealth aircraft always have a remarkable advantage over any conventional aircraft.

In theory, the RCS of some simple objects, such as a perfect sphere, can be
well defined. In practice, most targets are rather complex objects and their RCS
usually fluctuates considerably, as they move with respect to a radar. In fact, the
monostatic or backscatter RCS depends on the following

Position of radar antenna relative to target
 Angular orientation of target relative to radar antenna
 Frequency of the electromagnetic energy
 Radar antenna polarization.

Of course aircraft RCS change with aspect, their shapes are not spherical, how could you only figure that out just now?

For the F-35, the approach was the construction of a l.o. aircraft, taking seriously
into account the cost parameter. Therefore, in the frame of cost reduction, some
capabilities were “sacrificed”: RCS is really low in the X-band (8 – 12 GHz) and in
the Ku-band (12 – 18 GHz), while it is not so low at lower frequency bands. The
scope is the break of the killing chain: even if the F-35 is detected by surveillance
radar, it will not be easy to be engaged by a fire control radar, which usually operate
in the X or Ku bands. On the other hand, the F-22 presents a lower RCS from all
aspects and at more frequency bands, of course at a considerably higher cost

The production F-35 is expected to present a higher RCS than the prototype
X-35, since more volume was required for the internal equipment and armament bays.
The curves of the redesigned fuselage will incur an RCS increase, from some certain
directions. It was calculated that the RCS will remain very low from the frontal sector
and more precisely from a sector of 29ο in front of the aircraft. However, the RCS will
not be so low from the lateral aspect and also from the rear aspect. The whole
behavior deteriorates at lower frequency bands

Very low frequency band radars, for medium to high altitude
surveillance: as the frequency decreases, the wavelength increases and becomes
comparable with major parts of the aircraft. Thus, scattering enters the resonance
region, exhibiting a higher Radar Cross Section (RCS), at least momentarily. Also, the
Radar-Absorbent Materials (RAM) are not very effective at lower frequencies. For
these reasons, radars operating, e.g., in the VHF band, are expected to see a l.o. target
at a longer distance with respect to “conventional”, higher frequency radars,
transmitting in the L or S-band.
https://www.researchgate.net/publication/259503614_Low_Observable_Principles_Stealth_Aircraft_and_Anti-Stealth_Technologies

That paragraph is word by word copy from Carlo Kopp in APA with his infamous anti F-35 and F-22 lobby, unfortunately, it is full of crap
F-35 has lower RCS than F-22 has been confirmed by official authorities

The F-35 doesn’t have the altitude, doesn’t have the speed [of the F-22], but it can beat the F-22 in stealth.

Gen. Mike Hostage On The F-35; No Growlers Needed When War Starts - Breaking Defense

For years, the news about the most expensive conventional weapons system in US history, the F-35 Joint Strike Fighter, has been driven by its soaring costs, technical problems and schedule screw-ups. The government and Congress and the public rarely speak about what the F-35 will do, how...

breakingdefense.com

The F-35 on Final Approach | Air & Space Forces Magazine

The massive strike fighter program is less than a year from initial combat readiness.

www.airforcemag.com

 

[Ronny]

you know what, i do not believe you, the Sun show us there are not such limits,
View attachment 621016
In fact math too
View attachment 621017
this graph shows a tendency to growth to the infinite small to the infinite large. Second root graph
same to the second root graph, as long as you increase power density that graph will always go up, in fact fourth-root power function graph, grows slower but will go to infinity simple because X can run to infinity, Pt can run to infinity, thus Rmax can run to infinity

Thus you technical jargon pretty much is not proven by Math.
Pt can run to infinity, and as the wavelength gets longer the target RCS grows.
Now are real problems that limit radar technology? of course, but the radar equation does not limit the detection of stealth targets, RCS is not fixed First because aircraft have fixed sizes, a 20 meter F-22 or J-20 or whatever, has also fixed geometry, plus a detail you forget in your concept
their RCS
usually fluctuates considerably, as they move with respect to a radar. In fact, the
monostatic or backscatter RCS depends on the following

1-Position of radar antenna relative to target
2- Angular orientation of target relative to radar antenna
Now are there economic limitations to radar networks? yes, stealth makes the military budget more expensive, so Stealth can limit the radar network by over spending too much money, yes stealth is good to bankrupt militaries, but our friend the sun proves you are wrong

How far can you see a mosquito on a bright day? How far can you see an oil tanker on a bright day? Can you see both of them equally as far? That the point of stealth technology.
Your argument that because the graph can go infinite big, therefore you can detect stealth at an infinite distance because Pt can go to infinity is just utterly ridiculous. By that logic, because RCS is a variable, they can make it 0 or just infinite small to counter your infinite powerful radar. Or they can also make their jammer infinitely powerful so that your radar is useless. There are cost going along with increasing the power . The cost could be size of your radar, overheating, mobility, probably of intercept ..etc like the Sea base -X band, it is as maneuver as an oil tanker, the point is you can't just generate more and more and more power at no cost. If you can practically increase Pt to infinity then why stop at detection? why don't you design an HPW to fry your enemy from the horizon?

Look, you have to be realistic, the equation does not limit detectability as you are saying, RCS does grow with the wavelength, it is called resonance, Ronny even posted that diagram many many times. in fact i posted an article that says that
Very low frequency band radars, for medium to high altitude
surveillance: as the frequency decreases, the wavelength increases and becomes
comparable with major parts of the aircraft. Thus, scattering enters the resonance
region, exhibiting a higher Radar Cross Section (RCS), at least momentarily. Also, the
Radar-Absorbent Materials (RAM) are not very effective at lower frequencies. For
these reasons, radars operating, e.g., in the VHF band, are expected to see a l.o. target
at a longer distance with respect to “conventional”, higher frequency radars,
transmitting in the L or S-band.
https://www.researchgate.net/publication/259503614_Low_Observable_Principles_Stealth_Aircraft_and_Anti-Stealth_Technologies
The article is written by the greek military
So there you show you are wrong

RCS doesn't always grow with wavelength, pass the Mie region into the Rayleigh region, RCS will decrease with wavelength

 

[pegasus]

Persus, just because DSI is lighter, easier to maintain and cheaper to produce than others kind of inlet, doesn't mean it can't also have lower RCS compared to other kind of inlet. Those advantages are not mutually exclusive

Diverterless Supersonic Inlet (DSI)

www.globalsecurity.org

This pattern is originally in Chinese so may be slightly harder to understand

DSI inlet (also known as non-layer separated supersonic inlet channel, English name DiverterlessSupersonic Inlet, abbreviated as DSI inlet) are raising in popularity in recent years . Because it eliminates the conventional supersonic inlet boundary layer remover, but instead rely on a pressure inlet port lateral compression gradient driven type front surface boundary layer to the outer edge of the overflow inlet port technical solution, so that supersonic inlet while maintaining the total pressure recovery coefficient of performance parameters of intake prerequisite substantially constant, simplifying the structure, reducing the weight, reducing manufacturing and maintenance cost; and because there is no attachment surface with strong RCS signal source across the inlet, it greatly improved supersonic inlet RCS stealth performance. For these reasons, DSI are ideal intake port means for hypersonic vehicles aspirated engine powered device. On the F35, and JlO modifications and other new aircraft it has been applied widely

https://patents.google.com/patent/CN204755085U/en

tell me is F-35 stealthier than F-22, first which aircraft has better RCS frontally, later laterally, and later from the rear and why?

 

[pegasus]

That paragraph is word by word copy from Carlo Kopp in APA with his infamous anti F-35 and F-22 lobby, unfortunately, it is full of crap
F-35 has lower RCS than F-22 has been confirmed by official authorities

You do not believe that simply F-22 is not for sale, and by the way, from rear views F-22 is stealthier why?

 

[pegasus]

How far can you see a mosquito on a bright day? How far can you see an oil tanker on a bright day? Can you see both of them equally as far? That the point of stealth technology.
Your argument that because the graph can go infinite big, therefore you can detect stealth at an infinite distance because Pt can go to infinity is just utterly ridiculous. By that logic, because RCS is a variable, they can make it 0 or just infinite small to counter your infinite powerful radar. Or they can also make their jammer infinitely powerful so that your radar is useless. There are cost going along with increasing the power . The cost could be size of your radar, overheating, mobility, probably of intercept ..etc like the Sea base -X band, it is as maneuver as an oil tanker, the point is you can't just generate more and more and more power at no cost. If you can practically increase Pt to infinity then why stop at detection? why don't you design an HPW to fry your enemy from the horizon?

As shown in Fig. 14, when the aircraft is flying right towards the radar from 200 km away, the detection probabilities are very low when R is beyond about 120 km, for all 3 types of variable-sweep wing aircrafts. When the distance decreases to within 100 km, the aircraft with a sweep angle of χ = 54º performs best and the aircraft with a sweep angle of χ = 15º performs worst. When the distance decreases to within 40 km, all 3 types of variable-sweep wing aircrafts perform almost the same.

CONCLUSION

This paper utilizes the physical optics and the equivalent currents methods to study the RCS characteristics of the variable-sweep wing aircraft. Based on the numerical simulations of the aircraft, the following conclusions can be obtained:

The aircraft's RCS forward peak value decreases non-linearly with the sweep angle χ.

The sweep angle of the variable-sweep wing aircraft and the azimuth angle corresponding to one of the RCS peak values are identical.

When χ = 33º, σt ±30º = -0.7 dBm2. After unit conversion, σt ±30º of the aircraft when χ = 33º is 0.644% of that when χ = 0º.

The larger the sweep angle of the variable-sweep wing aircraft is, the lower the aircraft's detection probability will be.

We hope that the conclusions of this paper provide some reference and technical support for stealth aircraft's demonstration and designing

http://www.scielo.br/scielo.php?script=sci_arttext&pid=S2175-91462015000200170

explain me this and apply that to F-35 and F-22

 

[quellish]

Look, you have to be realistic, the equation does not limit detectability as you are saying, RCS does grow with the wavelength, it is called resonance, Ronny even posted that diagram many many times. in fact i posted an article that says that

As someone who has written validated scattering simulation software I can very confidently say you are incorrect.

The article is written by the greek military

So there you show you are wrong

I am not even going to touch that one.

Radars today use something similar to AESA but passive using different sources.

You are attempting to describe bistatic radars. "Radars today" are still predominantly monostatic. And stealth aircraft can still be stealthy against bistatic radars.

Your "experimental german radar" tracked an F-35 flying with a radar reflector installed.

so you are totally wrong simply using concepts without really thinking what they really mean

Not going to touch that one either.

Again, how does the sun factor into a discussion of radar? Can you elaborate on that?

 

[pegasus]

Not going to touch that one either.

Again, how does the sun factor into a discussion of radar? Can you elaborate on that?

the Sun is the largest emitting electromagnetic wave source we have , use Pt with the Sun, you will not change the equations, the equation does not limit detectability, my eyes see F-22 pretty visible, in fact optical devices will help me to see it, many aircraft have electro optical and Infrared devices nothing is stealth, stealth is a commercial ploy to sell aircraft, but is far cheaper to build radars and SAMs, the german radar maker says for 170 km they detected F-35, so i believe them, sorry your credentials are not the only ones radar makers from Russia, China, Germany do also claim to detect stealth aircraft, in fact ask yourself if radar is so limited why they say they discover black holes with radio telescopes? you discover black holes but you can not find F-35? go figure it

 

[quellish]

the Sun is the largest emitting electromagnetic wave source we have , use Pt with the Sun, you will not change the equations, the equation does not limit detectability,

The sun is not a radar. Not even conceptually similar.

stealth is a commercial ploy to sell aircraft,

OK....

radar makers from Russia, China, Germany do also claim to detect stealth aircraft

Might that be a ploy to sell radars?

in fact ask yourself if radar is so limited why they say they discover black holes with radio telescopes? you discover black holes but you can not find F-35? go figure it

I do not see how radio telescopes, black holes, radar, and "finding" an F-35 are at all related. Can you explain?

Radio telescopes receive transmissions from radio sources very, very far away. They do not transmit.
Radars transmit signals which reflect from an object back to the radar where they are received. This makes them pretty useless for observing stars (or black holes).

You may be onto something here though. Black holes suck up everything - including radar signals. A black hole may be the ultimate stealth device! Oh wait, your radar has unlimited power to transmit, that could be a problem. Of course, only a fraction of "unlimited" can make it back to the radar, so...

 

[pegasus]

The sun is not a radar. Not even conceptually similar.

No? what type of waves allow you to see?


if you answer electromagnetic waves, you are right, so then what makes your eyes to be? passive radars are not they?

AESA radars use an array of transmitters and receivers are not they? if you have in a hall many lamps do not they act the same way to your eyes?

Hey let me see, if there are multiple sources of electromagnetic waves is not possible use use them and build a radar , a passive radar that uses those arrays to detect stealth aircraft? yes the germans did it and they detected F-35 for 100 miles around 170 km wow so you do not need a single radar you can use a network of radars ah I see the Russians did the same wow, yes the sun and our eyes do act like a radar do you see?

 

[In_A_Dream]

I would be interested to hear about what kind of real world scenario where you would find the F-35 & F-22 squaring up against a formidable IADS (that's not a pop-up) on its own, to justify the lengthy discussions you are having with everyone Pegasus about F-22/F-35 stealth.

In reality, whether you're on a SEAD mission or what have you, you're going to have jamming support. Nevermind the fact that there's a whole arsenal of classified capabilities available to the US military to minimize the effectiveness of an enemy's air defense systems.

 

[pegasus]

I would be interested to hear about what kind of real world scenario where you would find the F-35 & F-22 squaring up against a formidable IADS (that's not a pop-up) on its own, to justify the lengthy discussions you are having with everyone Pegasus about F-22/F-35 stealth.

In reality, whether you're on a SEAD mission or what have you, you're going to have jamming support. Nevermind the fact that there's a whole arsenal of classified capabilities available to the US military to minimize the effectiveness of an enemy's air defense systems.

I will say first I am not an expert, I am just an Engineer in Environmental sciences with some diplomas in software use for Computer Aided Design and other basic programs.


However I am a big fan of aviation, when i say fan i say that is what I am, I usually read a lot about basic technical papers that any one can find published on the internet.

So you can see I am not an expert, but I am not a stupid fan, in that well i am proud, the information on the internet on open sources and general aviation tells you DSI intakes have design limits, they have Design Mach numbers, F-35 for example has a DSI intake good for 0 km/h to Mach 1.6 ideal operation, probably it can go further, but it will lose thrust and spend more fuel so the F-35 is limited to Mach 1.6 speed, with the best pressure recovery at around Mach 1.


Now you have fans who will say to you J-20 will be a super fast aircraft of Mach 2.0 plus operation, ultra stealthy DSI, better than F-22 or Su-57, however if you read published speeds of F-35, J-10B or JF-17 or even papers published on the internet, the Mach 1.6-1.8 limit is pretty obvious





The same type of fans think the caret Intake is less stealthy and J-20 will be faster.


Now if you are honest, DSI require less RAM due to the lack of boundary layer diverter, thus they have a plus over caret intakes, but the Bump is not the stealthiest feature, frontally is okay, frontal RCS of DSI is okay but there is diffraction so there are some imperfections of DSI as well, so both have advantages and disadvantages, caret intakes require more RAM but they adjust better to the aircraft need for planform alignment for stealth, so F-22 will be more expensive to achieve similar radar signature than F-35 but its Chines will have more armony with the caret intake in general planform alignment than F-35.

On Su-57 performance will be better, why? its pressure recovery will be at Mach 2 around 95% while DSI intakes gets around 87%-89% due to the similarities in performance to F-14 intakes, it will require more RAM too like F-22, but in planform alignment will be better.


To summarize without fan feelings both intakes are good, F-35 and F-22 exemplify it, but if you want higher speeds Su-57 has the ideal intake, if you want lower speeds below Mach 2 then DSI intakes go well.


are they invisible to radar? yes they are if they are far enough, yes they are invisible to radar, but their RCS depends in several factors, if they are facing modern defences both types of intakes will be detected, however we are talking about different aircraft so the general RCS of each aircraft will differ, F-22 is not Su-57 or F-35 is not J-20 or J-31, we do not need to fall into fan like competitions, stealth aircraft are not infallible machines nor defenceless ones, the conversation has been basically about the advantages and disadvantages and originally about the potential mesh J-20 has as boundary layer bleed and bypass.

Just looking at the boundary layer bleed porous holes on JF-17s bump and cowl, which still is a Mach 1.6-Mach aircraft you still can conjecture J-20 is a Mach 1.8 type aircraft at the most with a potential Mach 2 but losing lot of fuel and pressure recovery.

So even with WS-15 will not perform better than Su-57 at speeds beyond Mach 2, with Al-31 or WS-10 well it is unlikely can out perform F-22 or even Su-57 with 117 type engines.

However my last lines infuriate J-20 fans, but DSI intakes have limits they do not want to see.


Production
Pakistan Aeronautical Complex (PAC) holds the exclusive rights of 58% of JF-17 airframe co-production work. A comprehensive infrastructure comprising state of the art machines and required skilled human resource has very quickly been developed at the Complex. The final assembly and flight testing of the aircraft was the first JF-17 co-production activity to start at PAC. The first PAC produced aircraft was handed over to Pakistan Air Force in November 2009. Since then, aircraft are being produced regularly to meet the required schedule. The co-production of sub assemblies and structural parts has also commenced and is sequentially attaining the sustained production status. Besides upgrading the production system, PAC has also upgraded its quality, technology and archive management systems to meet the production and management standards of a 3rd generation fighter aircraft.

Specifications​ Physical Parameters Length 49 ft Height 15.5 ft Wingspan 31 ft Empty Weight 14,520 lb Performance Parameters Maximum Take Off Weight 27,300 lb​ Max Mach No 1.6​ Maximum Speed 700 Knots IAS​ Service Ceiling 55,500 ft​ Thrust to Weight Ratio 0.95​ Maximum Engine Thrust 19,000 lb​ G Limit +8,-3​ Ferry Range 1,880 NM​ Armament No of Stations 07​ Total Load Capacity 3400 l​

https://www.pac.org.pk/jf-17

 

[Jemiba]

This discussion is going round in circles now. We should stop here with the old say
"I agree to disagree" .

 

[overscan (PaulMM)]

Agreed. Reading some articles does not make one an expert, and analogies are not always helpful beyond the most superficial level of understanding of a topic. Posting huge swathes of text and pictures with only vague relevance to one's argument is just annoying.

 

[charleybarley]

Is this the Grumman Tiger bump inlet?

http://naca.central.cranfield.ac.uk/reports/1957/naca-rm-e56l19.pdf

Does anyone have anything describing the Crusader III inlet?

Thanks.

 

[aim9xray]

Yes, those are for the F11F-1F Super Tiger test aircraft.

 

[aonestudio]

https://twitter.com/x/status/1263959286171996160

 

[Ronny]

We know S-duct and intake blocker can help reduce radar cross section of aircraft, because the engine fan blade are very reflective to radar wave.
But can S-duct intake or intake blockers help reduce the infrared signature of aircraft?
I found out a day ago that even the first fan stage can be quite hot so in theory, blocking the view to them could reduce the thermal signature.
Do anyone has any additional frontal thermal images of fighter to confirm or debunk this theory ?

 

[Cool ice]

>blocker vs S-Duct : irrelevant for su-57 , it uses both S- ducts and blockers with only about 10 percent of the disk face showing , blown out of proportion by the internet to make it look like the entire face is showing. Sukhoi knows that the blades are a radar disco ball. Its obvious. Anaechoic chambers know that too. Thus , its just what kind of solution they picked to meet the requirment , if RAM on the walls plus mostly serpentine duct plus a blocker is good enough for the attenuation to be _at least_ F-22 level , (which is the requirment , the official requirment, the only official one , in vast contrast to the widely popular yet unsubstansed claim of "the russians only aimed for semi-stealth//frontal stealth//watered down stealth , and Su-57 *passed* the trials dedicated to display that, thus , checked the requirment of _at least_ F-22 level of RCS), perhaps capitalising on 10 years of advancement in materials science, then you can shave off the extra weight of that extra volume that would've been existed. Theres evzn The idea of using that weight elsewhere , such as thicker RAM ,which in return gives off less radiance.
As long as no detailed, structured , well backed up research , with test chamber data from multiple angles comes in , the whole su-57 stealth flaw story simply has no grounds. It does make for some nice clickbait there's a good reason why it was enviwaged that even anaechoic chambers would take more than 72 continuous hours of testing to assess the RCS.
It is very flawed and irrealistic to think that a people with extensive academic and practical activity in the field of radio physics and materials science , process engineering and mathematical modeling ,will commit an giant oopsie. Just like mike from downtown will never convince anyone that his garage concotion will defeat the corona virus while thousands of well established companies pulled tooth and nail to acheive some progress , internet articles about the round IRST/KS-0 bad and poor panel work will never school actual professionals.
F-35 is far bumpier than the extremely faceted F-117 , but guess which one is an order of a magnitude stealthier?
BAE systems are not morons and they went for putting a a round IRST on TAI-TFX, sukhoi are not morons for having faceted IRST on mig-25 then ditching just it , and being as extreme as to make faceted tiny engine bumps but forgetting about the mandarine in front of the cockpit, or purposefully edging panels and leaving others , the fact that they did it in certain parts and not others means they are fully aware of the principle . Mikoyan too , look at mikoyans keel-less stealth heavy fighter concept of the 90s . They perfectly grasp the principles of stealth. the fact that We dont know what solution they picked doesn't mean su-57 isnt syealthy or inferiorly stealthy to F-22/35.
As for the Criticism of the T-50 prototype then it was wrong from start. You can apply the same logic to USA's T-50's (YF-22/X-32/35 ) and the same will happen. Bottom line: requirment is at lezst F-22 level of stealth , stated by academian davidenko , Su-57 passed trials,confirmed characterstics , thats official. By elimination, it meets the goal.

 

[BLACK_MAMBA]

>blocker vs S-Duct : irrelevant for su-57 , it uses both S- ducts and blockers with only about 10 percent of the disk face showing , blown out of proportion by the internet to make it look like the entire face is showing. Sukhoi knows that the blades are a radar disco ball. Its obvious. Anaechoic chambers know that too. Thus , its just what kind of solution they picked to meet the requirment , if RAM on the walls plus mostly serpentine duct plus a blocker is good enough for the attenuation to be _at least_ F-22 level , (which is the requirment , the official requirment, the only official one , in vast contrast to the widely popular yet unsubstansed claim of "the russians only aimed for semi-stealth//frontal stealth//watered down stealth , and Su-57 *passed* the trials dedicated to display that, thus , checked the requirment of _at least_ F-22 level of RCS), perhaps capitalising on 10 years of advancement in materials science, then you can shave off the extra weight of that extra volume that would've been existed. Theres evzn The idea of using that weight elsewhere , such as thicker RAM ,which in return gives off less radiance.
As long as no detailed, structured , well backed up research , with test chamber data from multiple angles comes in , the whole su-57 stealth flaw story simply has no grounds. It does make for some nice clickbait there's a good reason why it was enviwaged that even anaechoic chambers would take more than 72 continuous hours of testing to assess the RCS.
It is very flawed and irrealistic to think that a people with extensive academic and practical activity in the field of radio physics and materials science , process engineering and mathematical modeling ,will commit an giant oopsie. Just like mike from downtown will never convince anyone that his garage concotion will defeat the corona virus while thousands of well established companies pulled tooth and nail to acheive some progress , internet articles about the round IRST/KS-0 bad and poor panel work will never school actual professionals.
F-35 is far bumpier than the extremely faceted F-117 , but guess which one is an order of a magnitude stealthier?
BAE systems are not morons and they went for putting a a round IRST on TAI-TFX, sukhoi are not morons for having faceted IRST on mig-25 then ditching just it , and being as extreme as to make faceted tiny engine bumps but forgetting about the mandarine in front of the cockpit, or purposefully edging panels and leaving others , the fact that they did it in certain parts and not others means they are fully aware of the principle . Mikoyan too , look at mikoyans keel-less stealth heavy fighter concept of the 90s . They perfectly grasp the principles of stealth. the fact that We dont know what solution they picked doesn't mean su-57 isnt syealthy or inferiorly stealthy to F-22/35.
As for the Criticism of the T-50 prototype then it was wrong from start. You can apply the same logic to USA's T-50's (YF-22/X-32/35 ) and the same will happen. Bottom line: requirment is at lezst F-22 level of stealth , stated by academian davidenko , Su-57 passed trials,confirmed characterstics , thats official. By elimination, it meets the goal.

The Russians are always going to say that the Su-57 is "at least F-22" level of stealth. They boast about this plane as "the best in the world" in their propaganda videos when there is plenty evidence they still committed a few stealth no-no's.

At the end of the day it comes down to their requirements which from an outsiders perspective is affordable stealth. They didn't fuss and spend millions on evey single feature of the aircraft to decease its signature. The spent the money where big gains are to be had and accepted the losses brought by other aspects. It simplifies production quite a bit if you don't facet every single joint on the airframe for example.

So yes, I have no doubt that Sukhoi met the requirements expected of them but those requirements were not "at least F-22 level" as they like to claim in the media.

Just an after thought - the reason the construction of the X-32/35 is ignored by many is because they were experimental concept demonstrators designed to prove how they would meet the VSTOL requirements. The ATF program on the other hand delivered prototypes in the shape of the YF-22/23. This should be clear from the designation and the difference in attention to finish and design detail of their construction compared to the experimental JSF demonstrators. The T-50's were clearly prototypes more inline with the YF-XX's than experimental demonstrators of the X-XX's hence construction criticsm although the fit and finish of production aircraft seem of very high quality - western levels of fit and finish I would say.

 

[Cool ice]

>blocker vs S-Duct : irrelevant for su-57 , it uses both S- ducts and blockers with only about 10 percent of the disk face showing , blown out of proportion by the internet to make it look like the entire face is showing. Sukhoi knows that the blades are a radar disco ball. Its obvious. Anaechoic chambers know that too. Thus , its just what kind of solution they picked to meet the requirment , if RAM on the walls plus mostly serpentine duct plus a blocker is good enough for the attenuation to be _at least_ F-22 level , (which is the requirment , the official requirment, the only official one , in vast contrast to the widely popular yet unsubstansed claim of "the russians only aimed for semi-stealth//frontal stealth//watered down stealth , and Su-57 *passed* the trials dedicated to display that, thus , checked the requirment of _at least_ F-22 level of RCS), perhaps capitalising on 10 years of advancement in materials science, then you can shave off the extra weight of that extra volume that would've been existed. Theres evzn The idea of using that weight elsewhere , such as thicker RAM ,which in return gives off less radiance.
As long as no detailed, structured , well backed up research , with test chamber data from multiple angles comes in , the whole su-57 stealth flaw story simply has no grounds. It does make for some nice clickbait there's a good reason why it was enviwaged that even anaechoic chambers would take more than 72 continuous hours of testing to assess the RCS.
It is very flawed and irrealistic to think that a people with extensive academic and practical activity in the field of radio physics and materials science , process engineering and mathematical modeling ,will commit an giant oopsie. Just like mike from downtown will never convince anyone that his garage concotion will defeat the corona virus while thousands of well established companies pulled tooth and nail to acheive some progress , internet articles about the round IRST/KS-0 bad and poor panel work will never school actual professionals.
F-35 is far bumpier than the extremely faceted F-117 , but guess which one is an order of a magnitude stealthier?
BAE systems are not morons and they went for putting a a round IRST on TAI-TFX, sukhoi are not morons for having faceted IRST on mig-25 then ditching just it , and being as extreme as to make faceted tiny engine bumps but forgetting about the mandarine in front of the cockpit, or purposefully edging panels and leaving others , the fact that they did it in certain parts and not others means they are fully aware of the principle . Mikoyan too , look at mikoyans keel-less stealth heavy fighter concept of the 90s . They perfectly grasp the principles of stealth. the fact that We dont know what solution they picked doesn't mean su-57 isnt syealthy or inferiorly stealthy to F-22/35.
As for the Criticism of the T-50 prototype then it was wrong from start. You can apply the same logic to USA's T-50's (YF-22/X-32/35 ) and the same will happen. Bottom line: requirment is at lezst F-22 level of stealth , stated by academian davidenko , Su-57 passed trials,confirmed characterstics , thats official. By elimination, it meets the goal.

The Russians are always going to say that the Su-57 is "at least F-22" level of stealth. They boast about this plane as "the best in the world" in their propaganda videos when there is plenty evidence they still committed a few stealth no-no's.

At the end of the day it comes down to their requirements which from an outsiders perspective is affordable stealth. They didn't fuss and spend millions on evey single feature of the aircraft to decease its signature. The spent the money where big gains are to be had and accepted the losses brought by other aspects. It simplifies production quite a bit if you don't facet every single joint on the airframe for example.

So yes, I have no doubt that Sukhoi met the requirements expected of them but those requirements were not "at least F-22 level" as they like to claim in the media.

Just an after thought - the reason the construction of the X-32/35 is ignored by many is because they were experimental concept demonstrators designed to prove how they would meet the VSTOL requirements. The ATF program on the other hand delivered prototypes in the shape of the YF-22/23. This should be clear from the designation and the difference in attention to finish and design detail of their construction compared to the experimental JSF demonstrators. The T-50's were clearly prototypes more inline with the YF-XX's than experimental demonstrators of the X-XX's hence construction criticsm although the fit and finish of production aircraft seem of very high quality - western levels of fit and finish I would say.

Friend ,
Which russians? Propaganda news outlets made to speak good of russian equipment and trash US equipment are *entirely* separated entities from Sukhoi and Academians such as Alexander davydenko which make accurate and reasonable statements in contrast to propaganda sources.
we can make an exact same analogy with western sources and pretty much an enormous amount of western news websites showering us with endless "su57 bad" and "su 57 cancelled" articles , and then say that because those outlets lie , Lockheed must be lying too. again , separate entities.
by the way , being state funded or not has no relation , it still does not eliminate the point that news outlets made to propagate ideas or make money from clickbait are separate from the guys that actually make the plane.
"the russians are lying and boasting" argument is quite a misconception , news agencies can lie , not multi million dollar companies that will have their equipment checked over and over in all kinds of trials by both domestic and foreign countries to actually sign contracts. Lying about military products will just shoot you in the foot. Had there been any scandlas regarding su-35s not being as good as advertised ? or Su-30SM? T-90S tanks being sold like hot cakes? Did the russian MoD care about bad press when they aimed to pick the Felin individual soldier pack instead of russian equipment in the early 2000's?
if an official source directly from the company states something then there are very high chances that its true because they do not have any right to lie, and do not have any gain from lying since its trials and tests that will win the deal and bring money , not the claims.
Of course i am aware of the chances of scandals happening now and then , like literally any company , but its not something sukhoi is particularly famous for , and if someone wants to claim the su57 is worse than advertised , evidence is needed , if not , its a guess.
and that evidence is to be in form of solid concrete data gained from real tests with appropriate equipment.Anything less than that does not qualify as evidence , let alone photograph observations. then at that time we can conclude that they are lying. Apart from that anyone can say any company is lying.

the official requirment is no less than F-22 level because there is a non propaganda source telling so:

i dont see any stealth no nos with the su57 , what is considered evidence is not a photograph , RCS testing need an echo chamber , hours upon hours of irradiation , and accurate data from all angles, nothing short of that will ever be evidence
''But how about the gaps that are non aligned ?'' a sealant is Used. ''But all stealth planes use sealants yet they have edged panels !'' except that there is a sealant from another and it all depends on its quality and the level of attenuation ,glazing coatings on the SU57 are twice as absorbant as previous models , there are ten years between the F22 and Su57 , also , note that the edged panels on the su57 are on moving parts , landing gear and weapon bay doors , meanwhile , the straight ones are the ones on non moving parts , hence tighter cavities.That may only need a good enough sealant to hide
Just think about it this way ; Sukhoi knows about the importance of panel serrations , which is why they implemented them , if they did not implement them in other panels then they must have a very good reason for it , the fact that we dont know why doesnt mean they are necessarly wrong. why would they purposely pick certain panels to edge and leave others?

the point that they are doing it to simplify production does not stand. For starters there is no source claiming it , furthermore , can someone calculate the cost saving of using non aligned panels vs using aligned panels and ration that with the signature increase related to it if there is any ? what is the pourcentage of any potential cost incrase related to edging all of the panels , ill have to remind people that if a plane costs 100 million dollars , and edging all of the panels adds an entire million on its own , that is a measly 1 percent cost increase , not something you'd wanna care about if it gives you Rcs drawbacks. and last but not least , it goes in absolute contrast to the su57 patent which purposely state that they are eliminating all of the inhomogenities in the signature , which totally kills the ''panel alignment flaw" argument:

It says , literally : eliminate , entirely remove.
literally all of the "flaws" seen on the su 57 follow the same model , weather it be the round IRST or the 101KSO bulbs or others.
they all have the flaw of assuming that hundereds of experts with hundereds of hours of RCS testing data in their hands will make rookie mistakes , which is not conceivable , or assume that they did it on purpose because the requirment is ''semi stealth / watered down stealth / partial stealth" which not only have zero evidence from the company , but also , goes in absolute contradiction with the actual official statement on the matter. Which means that by elimination , they simply found solutions to go around any potential drawbacks of the traditional solutions.(although i can talk about each part , the IRST , Optics , etc , it will result in a very long post)

the logic that states that the su57 is inferior in stealth to things like F-22 / 35 also implies that the F-35 is less stealthy than the F-117. The F35 has many rounded up shapes , such as the back of the engine , the massive cylinder where the gun lays, the countless lumps and bumps on its underside , by any means , the extremely faceted F-117 should be stealthier , but the F-35 actually is stealthier than.

 

[Cool ice]

X-35 and 32 are full of what are to be considered , by the Logic usually hammered upon the Su-57 , big RCS flaws.

Sure their point was to demonstrate VSTOL requirments and other matters , but that point is exactly appliable to the T-50 prototypes , that had specefic goals of construction that were not necessaily stealth. Some of them were made purely to validate flight performance, others to test weapons and radio electronics, therefore , stealth details were out of concern. Yet we've seen some media outlets literally criticise the stealth of T-50-1.

 

[overscan (PaulMM)]

If you believe the RCS requirement for F-22 was 0.3-0.4 sq m, then you may be interested in an investment opportunity in Nigeria I recently received in my email.

 

[Cool ice]

If you believe the RCS requirement for F-22 was 0.3-0.4 sq m, then you may be interested in an investment opportunity in Nigeria I recently received in my email.

If you believe that RCS is a single value then then you might be interested in a post as a janitor in my recently built company over at Nigeria

 

[LMFS]

Since apparently a couple of rivets ruin the Su-57 as VLO design, I am genuinely interested in knowing how this AESA of almost 1 sqm:

...can have a much smaller RCS than a metal ball of 5.6 mm radius? Or to put it differently, if the Su-57 was carrying a huge plate full of metal spikes on the fuselage, could it be considered a VLO-compatible design? Genuine question, please let me know how this is done if you know it because I am not seeing it that easy.

 

[Cool ice]

Since apparently a couple of rivets ruin the Su-57 as VLO design, I am genuinely interested in knowing how this AESA of almost 1 sqm:

...can have a much smaller RCS than a metal ball of 5.6 mm radius? Or to put it differently, if the Su-57 was carrying a huge plate full of metal spikes on the fuselage, could it be considered a VLO-compatible design? Genuine question, please let me know how this is done if you know it because I am not seeing it that easy.

I dont know about F-35(although im sure they do have a solution.) but the Su-57 is going to have an easy time giving the fact that it has a flat antenna tilted upwards.

I wouldnt get too carried away with the 0.0001 sqm idea , Lockheed is right about anything they specefy about their plane , but Lockheed states that as a frontal value. They never said anything regarding other angles.

Imagine any stealth airplane irradiated by enemies from above , like six different angles from the sides , possibly ground radars from below , all networked , one may understand why sukhoi likes to use more pragmatic values during their interviews. Im sure lockheed is just as knowledgable , the only entity blowing things out of proportion is the internet.

 

[overscan (PaulMM)]

The short answer is frequency selective radomes. Which are very difficult to get right.

 

[overscan (PaulMM)]

If you believe the RCS requirement for F-22 was 0.3-0.4 sq m, then you may be interested in an investment opportunity in Nigeria I recently received in my email.

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Of course it’s not a single value. However stealth only works with reductions in RCS of multiple orders of magnitude. Reducing RCS from 10 sq m (F-15) to 0.4 sq m would not be tactically very significant.

Averaging the RCS in every possible direction isn't meaningful because the stealth aircraft RCS has large spikes in certain specific directions. Any radar energy not absorbed by RAM/RAS must reflect somewhere!

The art of stealth design is arranging the spikes in the least useful direction for the enemy, and also planning your flight to minimise the chance of your "spikes" pointing in tactically useful directions.

If you imagine a stealth aircraft with a large spike pointing directly down to the ground - this isn't tactically very useful to its opponent as you won't detect it until it passes directly overhead - and that assumes the radar even has a useable elevation capability of 90 degrees.

Every air-air fight is going to start at a certain geometry (roughly equal heights, heading at each other) which means frontal RCS is very important.

A frontal RCS of 0.3 to 0.4 sq m would be less ambitious than Typhoon or later model F-16/18 and result in no useful stealth capability at all.

 

[Josh_TN]

If you believe the RCS requirement for F-22 was 0.3-0.4 sq m, then you may be interested in an investment opportunity in Nigeria I recently received in my email.

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Do you have a dental plan?

 

[BLACK_MAMBA]

Friend ,
Which russians? Propaganda news outlets made to speak good of russian equipment and trash US equipment are *entirely* separated entities from Sukhoi and Academians such as Alexander davydenko which make accurate and reasonable statements in contrast to propaganda sources.
we can make an exact same analogy with western sources and pretty much an enormous amount of western news websites showering us with endless "su57 bad" and "su 57 cancelled" articles , and then say that because those outlets lie , Lockheed must be lying too. again , separate entities.
by the way , being state funded or not has no relation , it still does not eliminate the point that news outlets made to propagate ideas or make money from clickbait are separate from the guys that actually make the plane.
"the russians are lying and boasting" argument is quite a misconception , news agencies can lie , not multi million dollar companies that will have their equipment checked over and over in all kinds of trials by both domestic and foreign countries to actually sign contracts. Lying about military products will just shoot you in the foot. Had there been any scandlas regarding su-35s not being as good as advertised ? or Su-30SM? T-90S tanks being sold like hot cakes? Did the russian MoD care about bad press when they aimed to pick the Felin individual soldier pack instead of russian equipment in the early 2000's?
if an official source directly from the company states something then there are very high chances that its true because they do not have any right to lie, and do not have any gain from lying since its trials and tests that will win the deal and bring money , not the claims.
Of course i am aware of the chances of scandals happening now and then , like literally any company , but its not something sukhoi is particularly famous for , and if someone wants to claim the su57 is worse than advertised , evidence is needed , if not , its a guess.
and that evidence is to be in form of solid concrete data gained from real tests with appropriate equipment.Anything less than that does not qualify as evidence , let alone photograph observations. then at that time we can conclude that they are lying. Apart from that anyone can say any company is lying.

the official requirment is no less than F-22 level because there is a non propaganda source telling so:View attachment 647335

i dont see any stealth no nos with the su57 , what is considered evidence is not a photograph , RCS testing need an echo chamber , hours upon hours of irradiation , and accurate data from all angles, nothing short of that will ever be evidence
''But how about the gaps that are non aligned ?'' a sealant is Used. ''But all stealth planes use sealants yet they have edged panels !'' except that there is a sealant from another and it all depends on its quality and the level of attenuation ,glazing coatings on the SU57 are twice as absorbant as previous models , there are ten years between the F22 and Su57 , also , note that the edged panels on the su57 are on moving parts , landing gear and weapon bay doors , meanwhile , the straight ones are the ones on non moving parts , hence tighter cavities.That may only need a good enough sealant to hide
Just think about it this way ; Sukhoi knows about the importance of panel serrations , which is why they implemented them , if they did not implement them in other panels then they must have a very good reason for it , the fact that we dont know why doesnt mean they are necessarly wrong. why would they purposely pick certain panels to edge and leave others?

the point that they are doing it to simplify production does not stand. For starters there is no source claiming it , furthermore , can someone calculate the cost saving of using non aligned panels vs using aligned panels and ration that with the signature increase related to it if there is any ? what is the pourcentage of any potential cost incrase related to edging all of the panels , ill have to remind people that if a plane costs 100 million dollars , and edging all of the panels adds an entire million on its own , that is a measly 1 percent cost increase , not something you'd wanna care about if it gives you Rcs drawbacks. and last but not least , it goes in absolute contrast to the su57 patent which purposely state that they are eliminating all of the inhomogenities in the signature , which totally kills the ''panel alignment flaw" argument:View attachment 647334

It says , literally : eliminate , entirely remove.
literally all of the "flaws" seen on the su 57 follow the same model , weather it be the round IRST or the 101KSO bulbs or others.
they all have the flaw of assuming that hundereds of experts with hundereds of hours of RCS testing data in their hands will make rookie mistakes , which is not conceivable , or assume that they did it on purpose because the requirment is ''semi stealth / watered down stealth / partial stealth" which not only have zero evidence from the company , but also , goes in absolute contradiction with the actual official statement on the matter. Which means that by elimination , they simply found solutions to go around any potential drawbacks of the traditional solutions.(although i can talk about each part , the IRST , Optics , etc , it will result in a very long post)

the logic that states that the su57 is inferior in stealth to things like F-22 / 35 also implies that the F-35 is less stealthy than the F-117. The F35 has many rounded up shapes , such as the back of the engine , the massive cylinder where the gun lays, the countless lumps and bumps on its underside , by any means , the extremely faceted F-117 should be stealthier , but the F-35 actually is stealthier than.

Firstly, the F-35 is certainly stealthier than the F-117 simply because the computer used to design the 117 filled the basement of an entire building and it still could not process radar returns of triangles smaller than what are visible on the aircraft. In both cases the same effort was put into construction (Sukhoi certainly stepped up their effort in fit and finish as both I and others have mentioned). The F-35 is simply billions of infinitely small triangles coupled together to form a round shape - such is the power of modern computers.

Secondly, the only source of aircraft specifications I trust less than propaganda outlets are manufacturers specifications they release publicly. Why would they smear their own product compared to its competitors in a public arena? The only reliable source would be an independent country evaluating say Su-57 and F-35 for acquisition. The bids handed to that selection committee will be the most accurate and they are also not public knowledge hence we can only speculate.

Thirdly, if Sukhoi managed to find such simple solutions to RCS issues using only coatings why didn't LM pick them up on F-35 and why are the Chinese putting such effort into "Western" style details like faceted covers instead of just coating round shapes for optical sensors etc? Like with nearly all LO details it is the combination of coatings and shape that give the end result. Ben Rich stated 60% air frame and 40% coatings for LO on the 117. The ratio undoubtedly has changed by today with advances in both RCS design and coatings but certainly not fully to either direction or we would see multiple solutions converging to simply using coatings and sealants. Instead we still see effort being put into both shape and coatings. If anything the big advance would have been in air frame design being able to calculate RCS for ever more complex objects instead of just for faceted objects.

These are the details pointing to Sukhoi being willing to accept less "stealth" which means their requirements were not "F-22 levels". Perhaps we could see changes when Su-57M with the new engines start production in a similar way to how the Chinese continually iterate their J-20.

 

[Ronny]

>blocker vs S-Duct : irrelevant for su-57 , it uses both S- ducts and blockers with only about 10 percent of the disk face showing , blown out of proportion by the internet to make it look like the entire face is showing. Sukhoi knows that the blades are a radar disco ball. Its obvious. Anaechoic chambers know that too. Thus , its just what kind of solution they picked to meet the requirment , if RAM on the walls plus mostly serpentine duct plus a blocker is good enough for the attenuation to be _at least_ F-22 level , (which is the requirment , the official requirment, the only official one , in vast contrast to the widely popular yet unsubstansed claim of "the russians only aimed for semi-stealth//frontal stealth//watered down stealth , and Su-57 *passed* the trials dedicated to display that, thus , checked the requirment of _at least_ F-22 level of RCS), perhaps capitalising on 10 years of advancement in materials science, then you can shave off the extra weight of that extra volume that would've been existed. Theres evzn The idea of using that weight elsewhere , such as thicker RAM ,which in return gives off less radiance.
As long as no detailed, structured , well backed up research , with test chamber data from multiple angles comes in , the whole su-57 stealth flaw story simply has no grounds. It does make for some nice clickbait there's a good reason why it was enviwaged that even anaechoic chambers would take more than 72 continuous hours of testing to assess the RCS.
It is very flawed and irrealistic to think that a people with extensive academic and practical activity in the field of radio physics and materials science , process engineering and mathematical modeling ,will commit an giant oopsie. Just like mike from downtown will never convince anyone that his garage concotion will defeat the corona virus while thousands of well established companies pulled tooth and nail to acheive some progress , internet articles about the round IRST/KS-0 bad and poor panel work will never school actual professionals.
BAE systems are not morons and they went for putting a a round IRST on TAI-TFX, sukhoi are not morons for having faceted IRST on mig-25 then ditching just it , and being as extreme as to make faceted tiny engine bumps but forgetting about the mandarine in front of the cockpit, or purposefully edging panels and leaving others , the fact that they did it in certain parts and not others means they are fully aware of the principle . Mikoyan too , look at mikoyans keel-less stealth heavy fighter concept of the 90s . They perfectly grasp the principles of stealth. the fact that We dont know what solution they picked doesn't mean su-57 isnt syealthy or inferiorly stealthy to F-22/35.
As for the Criticism of the T-50 prototype then it was wrong from start. You can apply the same logic to USA's T-50's (YF-22/X-32/35 ) and the same will happen. Bottom line: requirment is at lezst F-22 level of stealth , stated by academian davidenko , Su-57 passed trials,confirmed characterstics , thats official. By elimination, it meets the goal.

Su-57 doesn't use S-duct to hide the blade, at best you can call it a extremely slightly curved duct, but the curve is negligible, the front part that might be mistaken with the curve is the inlet ramp used for pressure recovery, technically speaking, it can be used as a form of blocker to reduce the amount of radar wave hitting the turbine blade, but it isn't as good as an S-duct because the ramp is a discontinuity so there are some surface wave traveling back when they hit the gap

A true S-duct look more like this:

While the advance on material science can help you make RAM with better absorbing capability, an S-duct is still better than a blocker from the signature perspective because it makes radar wave bounce multiple time and therefore accumulate the radar absorbing rating of the radar absorbing material (absorbing rating of 10 dB can be accumulate to 60 dB)

The requirement of Su-57 isn't "at least F-22 level". What A.Davidenko said is " we have similar visual requirement" which can mean many things. For example: if the requirement is to have RCS lower than -20 dBsm and Su-57 has RCS value of -30 dBsm while F-22 has RCS value of -40 dBsm, then they both satisfy the requirement and they both have the same requirement, yet their RCS is still not the same. Or their requirement can be something like "able to get within X distance from a specific radar system without being detected" then they can still have very different RCS and still the similar requirement. And to what extend can we count as similar? is the different of 5-10 dB still count as similar?
Secondly, just because Su-57 has higher RCS than F-22 and F-35 doesn't mean it is a flawed fighter . Because Russian and USA have different doctrine and different requirements for their fighter, as their force structure are very different. For example: S-duct is better for signature but take up more space and heavier, while blocker are not as good for signature but much lighter and allow a lighter aircraft and more space for fuel. But USA has many more aircraft carrier and tankers compared to Russia, so USA combat radius requirement doesn't need to be as high as Russia. In that case F-22, F-35 can scarify some fuel space for S-duct while Su-57 might opted to use a blocker because it must satisfy the range requirement as well. In the field of engineering, "best" is the enemy of "good enough", let say the investor set 5 requirements for your aircraft, it is better to pass all 5 requirements, than to pass one at very high score and fall all the other 4.

F-35 is far bumpier than the extremely faceted F-117 , but guess which one is an order of a magnitude stealthier?
the logic that states that the su57 is inferior in stealth to things like F-22 / 35 also implies that the F-35 is less stealthy than the F-117. The F35 has many rounded up shapes , such as the back of the engine , the massive cylinder where the gun lays, the countless lumps and bumps on its underside , by any means , the extremely faceted F-117 should be stealthier , but the F-35 actually is stealthier than F-117

The F-35 isn't randomly bumpier than F-117, it has the blended edges, the shape are still faceted but the edge where the facets connect are blended in a curve , it is done that way to reduce edge diffraction, which is an issue especially at low frequency. All stealth aircraft after F-117 use this sort of blended facets design so that their design can be VLO over a wider range of frequency.

But don't confuse a blended facets which make up of facets and only blended at the edge with circular or tube body, because a tube or spherical will lead to creeping wave return travel back to the source and it also have much wider specular lobes

 

[GARGEAN]

If you believe the RCS requirement for F-22 was 0.3-0.4 sq m, then you may be interested in an investment opportunity in Nigeria I recently received in my email.

At what aspect? At what frequency? With which emitting pattern?

Please, stop sticking to all those 0.0001m^2. You are a sane man after all! Thing has CANOPY. Huge perfect reflector visible from by far most relevant hemispheres. Yeah, metal coating, fancy material and what not, but it is NOT radar absorbant. It is a perfectly reflecting shape with quite huge forward profile and defined by basic reflection laws RCS. It alone is much bigger that all those numbers full of zeros.