Su-57 Stealth Fighter: News #6

Quite well done comparison about missile from DCS. Just a simulator but it's quite well done.

It looks to me that people forget that AA missiles have much less total energy compared to their target. Speed is not an unbounded
resource for AA missiles. So it is possible to evade them with high g turns. And modern jet fighters engage their enemies at much
greater distances which substantially undermines the short-range effectiveness of AA missiles.

kvs wrote:It looks to me that people forget that AA missiles have much less total energy compared to their target.   Speed is not an unbounded
resource for AA missiles.    So it is possible to evade them with high g turns.  And modern jet fighters engage their enemies at much
greater distances which substantially undermines the short-range effectiveness of AA missiles.

High G turns make your aircraft loose speed and energy which reduce ranges of your missiles.

Then your are less prepared for the second missile coming at you.

And if you escape the second one the enemy that was firing the missiles comes with better speed and higher altitude and have the advantage in WVR.

That why range is important. First to shoot has the advantage by sending the other one in defensive position which makes him harder to attack.

LMFS wrote:You see the little penalty a missile has flying very high. The peculiarity of this analysis is the optimization of lofting that Spurts did.

Here there is another analysis, studying the influence of launch conditions too:

https://jaesan-aero.blogspot.com/2018/10/aim-120c-study-using-missile-sim-part-1.html
https://jaesan-aero.blogspot.com/2018/10/aim-120c-study-using-missile-sim-part-2.html

These are relatively easy to find analysis that I think are rather well known to the enthusiasts out there, I don't have access to AAIA or similar papers that could have more authoritative data...

So it may be that a launch under conventional conditions (4G fighters at medium altitudes, specially with not so modern missiles with not so optimized loft) follows the rules you say, while one at bigger altitude with carriers flying also very high looks a bit different. Of course a plane that is faster is always going to be more challenging to catch, given it maintains capability to maneuver.  

That is a similar fluid-dynamics simulation , even more this one use as reference model the one i have pointed to you and the results are obviously very similar.
You can observe the graph describing the speed variation at the range function (delivery conditions being a 1.3 mach supersonic delivery at 30000 ft of altitude): at 60 km the speed is about 1.4 mach, that always without a single turn but as mere A-pole range.


If you want something more professional but not specifically computational about the subject in english i point to you this work of one of the maximum western aerodynamicist expert in supersonic flow field - Lester L. Cronvich -about missile design and optimization  

https://www.jhuapl.edu/Content/techdigest/pdf/V04-N03/04-03-Cronvich.pdf

About the usefullness of TVC as aerodynamic control mean at high altitude you can read at pag 176 (third page of the extract)

"With thrust vector control, the flow leaving the exit nozzle is deflected to produce a pitching moment.
Obviously this system is operable only when the engine is delivering thrust. Such systems are well suited to quick reaction when aerodynamic forces are low, such as for turning a missile shortly after it leaves its launcher or for a rocket missile at an extremely high altitude when aerodynamic forces are small.
Control by means of side jets, augmented by natural aerodynamic interference, has been used on some short range missiles but may not be adequate for high-performance, medium- to long-range tactical missiles."

About your idea that a missile will have an easier time maneuvering after an agile aircraft at high altitude against low altitude (it is the exact opposite control authority and lift requirements multiply enormously with altutide in particular with AA missiles lacking the necessary lifting surfaces) you can read at pag. 182

" Consideration must be given early in the design process to the maneuverability requirements at the highest altitude because maneuverability depends on controllable lift. The latter depends on the configuration lift coefficient attainable with the available control authority and the dynamic pressure, q, at which
the missile will operate:

Maneuverability (in g) =     lift (lb)
                                            _________
                                             weight (lb)
                                                    
      ............................                                                 
where C L is the lift coefficient, S is the reference area upon which CL is based, W is the missile weight, pi is the static pressure at the flight altitude, and gamma  is the ratio of the specific heats of air.
For example, at the same speed and for the same maneuver, the missile needs a lift coefficient at 80,000 ft altitude that is more than 40 times the sea level value.
Dynamic pressure is also an important parameter in designing the autopilot and in selecting its gain program."

The reason majority of fighter aircraft, the layout of which is not designed and optimized for very high altitude high mach regimes, to attempt anti-missile manouevre at lower altitude with the aim to bleed missile speed instead of capitalising aerodynamic limits is that theirs conficuration will mostly suffer the same penelties of the incoming missile itself.

A Typhoon and an F-16, at example, are worlds a part in terms of high-altitude high-mach aerodynamics performances for the completely different layout ; the former will surely capitalize that to outturn inbound missiles at high-altitude and high speed the latter will be forced to lower abruptly its altitude in the hope to manage to bleed missile's energy in denser air layers.

@Mindstorm:

Thanks for the link, I have seen some of those illustrations before but I am not sure I have read the text.

You can observe the graph describing the speed variation at the range function (delivery conditions being a 1.3 mach supersonic delivery at 30000 ft of altitude): at 60 km the speed is about 1.4 mach, that always without a single turn but as mere A-pole range.

I agree with those analysis (as in general I am in agreement with your points) and I am not sure they are in contradiction, the high speed of the missiles in Spur's analysis is maybe the biggest difference, he might be overestimating fuel's Isp maybe, but he knows those references the other guys are using. The main thing with the other analysis is that it is not very focused on lofting optimization and high altitude, high speed launching (only one example at 13 km altitude 1.5 M with only one lofting trajectory while Spurs launches at 1.6 M 60 kft, clearly thinking in the F-22). I am not sure right now if there was any significant change in the rocket engine between C5 and C7 versions of AMRAAM, maybe you remember this. The main, relevant difference between high and medium altitude is that a missile flying in very thin air is going to keep speed much longer (and need less steep climb), which in turn (lift grows quadratically with speed) makes it able to maneuver better, despite falling air density. Otherwise I totally agree with you, a missile flying 2.5 M against a target which may be close to 2 M is going to be relatively easy to defeat: first, because a bit of maneouvering is going to bleed its energy to the point that it cannot close in on the target at all; Second, because the slow closure rate gives the defending plane much more time to perform any evasive maneuver and exposes the missile to energy bleed for way longer; Third, because the slower speed of the missile forces it to fly with higher AoA and therefore bleeds its energy even faster. So it is quite normal that far shots are only going to allow the attacking side to force the opponent into defensive moves but not really get a kill. But with a delta of say 2 M, the missile just has to manoeuvrer minimally because the defending aircraft is not capable to generate separation fast enough. The relevance of the speed delta between missile and target cannot be easily overstated.

Control by means of side jets, augmented by natural aerodynamic interference, has been used on some short range missiles but may not be adequate for high-performance, medium- to long-range tactical missiles

As far as I know it is used for the 9M96 family which is a medium-long range SAM. I am not aware of MRAAMs using it though, maybe it is a too big, complex system considered prohibitive or unnecessary for them.

About your idea that a missile will have an easier time maneuvering after an agile aircraft at high altitude against low altitude (it is the exact opposite control authority and lift requirements multiply enormously with altutide in particular with AA missiles lacking the necessary lifting surfaces) you can read at pag. 182

See above, lift generated by the surfaces increases with the square of speed while air density does not decrease quadratically with altitude,at least not between 30 and 60 kft (*). The aircraft also has a hard time finding lift and thrust at high altitude so performance of non-optimized planes in such conditions is dismal, that is for sure. What the missile has but the plane does not is the possibility of flying very fast. You do not agree in general with the missile speed values I have given, I think they do not apply to a missile launched by a low kinematics platform like legacy fighters or F-35 but, depending on the distance to the target of the actual launch (we all know real BVR launches happen normally within 50 km and this may actually get worse with low RCS aircraft), a modern missile carried by a high performing airframe like F-22 or Eurofighter may cover that distance with a good portion of its speed intact. With Meteor that is even more the case of course but I suggest we leave it out for now. Against such fighters the Su-57 will have, I believe, a substantial advantage, platform wise, but I am not sure it compensates in case the missiles are at least not equivalent (Meteor seems to be the big issue here) and additionally as I said I think Russia, with a rational defensive approach, counts on using the IADS and specially OTH radars to always place their planes in the position from which they can attack but not being attacked.

The reason majority of fighter aircraft, the layout of which is not designed and optimized for very high altitude high mach regimes, to attempt anti-missile manouevre at lower altitude with the aim to bleed missile speed instead of capitalising aerodynamic limits is that theirs conficuration will mostly suffer the same penelties of the incoming missile itself.

Agreed

A Typhoon and an F-16, at example, are worlds a part in terms of high-altitude high-mach aerodynamics performances for the completely different layout ; the former will surely capitalize that to outturn inbound missiles at high-altitude and high speed the latter will be forced to lower abruptly its altitude in the hope to manage to bleed missile's energy in denser air layers.

Agree too, I meant 4G fighters in the sense of planes like F-16, F-18 etc which were in service in the 80's. The Eurocanards are 4.5G and the Eurofighter specifically was designed for air superiority with focus on supersonic high altitude performance.

(*) EDIT:

I have seen this is not actually true, see standard atmosphere data that proves the extreme reduction in air density:

10,000 m - 0.4135 kg/m3
20,000 m - 0.08891 kg/m3
30,000 m - 0.01841 kg/m3

No wonder the little lift and thrust planes find at that altitude, and also the big difference in drag for missiles.

LMFS wrote:I assume the far coupled canards + AoA + canard in higher plane should avoid that downwash from being detrimental, in fact canards are normally designed to improve lift through downwash and that they were using the Eurofighter in the paper as example simply because ITP works on the EJ2000 and therefore has real data, not as an assumption that the plane would not use the canards for supersonic trimming (maybe there is some confirmation available on the web about how this is actually done ?) At the moment it remains just my opinion too...

Sorry for the late replay, I tried to answer yesterday but couldn't manage the time!

Nobody is saying that the EF2000 is not using the canards for supersonic trimming, they just claim that: "Daniel Ikaza, ITP project manager - nozzles, says Dasa's study shows that a Eurofighter flying at 30,000ft (9,150m) and a speed of M1.8 requires a 4° upward flaperon deflection to maintain level flight. A 5° upward nozzle deflection instead would enable the aircraft to fly "clean" and reduce the required engine thrust by 3%.

It only means that even if the EF2000 has canards, upward flaperon deflection is required for such flight conditions, and as such the TVC would enable the increase in performance. I only think that the problem lies in your interpretation of the way how things work.
EF2000 canards are in fact considered as control canards: "In a control-canard design, almost all of the weight of the aircraft is carried by the wing and the canard is used primarily for pitch control during manoeuvring. In other words, a control-canard is predominantly a control surface and is usually at zero angle of attack.
In some combat aircraft such as the Eurofighter, control-canards are used to intentionally destabilize the aircraft in order to make them more manoeuvrable. In this case, electronic flight control systems use the pitch control function of the canard to create artificial static and dynamic stability."

Unlike the close coupled canards, EF canards which are further away from the main wing provide greater moment arm and consequently they need less deflection for the trimming thus further reducing the drag which is very useful for the high speed interception for example.
But they don't have the same properties of the close coupled canards, and that can be seen by the placement of the small strakes/vortex generators close and above the main wing.

I have found NASA's unclassified document regarding "CANARD WING LIFT INTERFERENCE RELATED TO MANEUVERING AIRCRAFT AT SUBSONIC SPEEDS"
I will quote some part of the text which is in relation to my proposed explanation in my previous post regarding the use of the flaperons for the EF2000 supersonic trimming:

"The results indicated that although downwash from the canard reduced the wing lift at angles of attack up to approximately 16°, the total lift was substantially greater with the canard on than with the canard off. At angles of attack above 16°, the canard delayed the wing stall. Changing canard deflection had essentially no effect on the total lift, since the additional lift generated by the canard deflection was lost on the wing due to an increased downwash at the wing from the canard. There was a favorable wing-on-canard lift interference if the canard was located longitudinally near the wing leading edge and in the wing chord plane or above the wing plane. A favorable body-on-canard interference effect was found that delayed canard stall."
This is not supersonic flight condition, but like I said, I can't do supersonic airflow simulation in my head, and this NASA document is the next best thing I can find with limited time on my hands.

[img] high quality cartoon images[/img]

We can see that the tip of the EF2000 canard is very close to the wing level and by using positive deflection in order to create the lift, trailing edge of the canard is going even lower [directing the downwash in different manner compared to negative deflection], and at the same time producing the lift induced drag in the form of very strong vortices.
This is also from the NASA paper: "When the canard is in the lower position, the vortices pass below the wing, where they encounter a retardant flow with an unfavorable pressure gradient which accelerates the forward progression of the vortex breakdown."

Like I said, this is my proposed explanation for the aditional use of the flaperons regarding the EF2000 supersonic trimming, that might or might not be wrong

PeregrineFalcon wrote:Sorry for the late replay, I tried to answer yesterday but couldn't manage the time!

No worries, we all answer when we can, if we can  

Nobody is saying that the EF2000 is not using the canards for supersonic trimming, they just claim that: "Daniel Ikaza, ITP project manager - nozzles, says Dasa's study shows that a Eurofighter flying at 30,000ft (9,150m) and a speed of M1.8 requires a 4° upward flaperon deflection to maintain level flight. A 5° upward nozzle deflection instead would enable the aircraft to fly "clean" and reduce the required engine thrust by 3%.

I made my assumption because I saw no such explicit mention, can you point out where exactly this is said? Actually for "reading friendliness" I used a pdf of that paper that I have in local drive, maybe it is a bit different to your version.

I only think that the problem lies in your interpretation of the way how things work.
EF2000 canards are in fact considered as control canards: "In a control-canard design, almost all of the weight of the aircraft is carried by the wing and the canard is used primarily for pitch control during manoeuvring. In other words, a control-canard is predominantly a control surface and is usually at zero angle of attack.
In some combat aircraft such as the Eurofighter, control-canards are used to intentionally destabilize the aircraft in order to make them more manoeuvrable. In this case, electronic flight control systems use the pitch control function of the canard to create artificial static and dynamic stability."

I see no problem, see the "static stability" part in the text you quote. In general I am making no assumptions as to how much lift the canard generates at a given speed, altitude, load etc. in the Eurofighter. My point is that canard is creating a positive contribution to lift instead of a negative one.

Unlike the close coupled canards, EF canards which are further away from the main wing provide greater moment arm and consequently they need less deflection for the trimming thus further reducing the drag which is very useful for the high speed interception for example.
But they don't have the same properties of the close coupled canards, and that can be seen by the placement of the small strakes/vortex generators close and above the main wing.

Agreed

I have found NASA's unclassified document regarding "CANARD WING LIFT INTERFERENCE RELATED TO MANEUVERING AIRCRAFT AT SUBSONIC SPEEDS"
I will quote some part of the text which is in relation to my proposed explanation in my previous post regarding the use of the flaperons for the EF2000 supersonic trimming:

Do you have information about the relative (vertical) position of the canard under study in that document or drawings of the general aero layout in general? For canards on the same plane (the case of the J-20 for instance and of other LO designs) of course the positive deflection is going to be detrimental to the wing's lift.

"The results indicated that although downwash from the canard reduced the wing lift at angles of attack up to approximately 16°, the total lift was substantially greater with the canard on than with the canard off. At angles of attack above 16°, the canard delayed the wing stall. Changing canard deflection had essentially no effect on the total lift, since the additional lift generated by the canard deflection was lost on the wing due to an increased downwash at the wing from the canard. There was a favorable wing-on-canard lift interference if the canard was located longitudinally near the wing leading edge and in the wing chord plane or above the wing plane. A favorable body-on-canard interference effect was found that delayed canard stall."

Some figures here would help, I am not quite sure what is de deflection of every control surface and AoA of the plane. Other statements look logical.

This is not supersonic flight condition, but like I said, I can't do supersonic airflow simulation in my head, and this NASA document is the next best thing I can find with limited time on my hands.

No problem, this seems a good contribution. I have found the document and will try to check it

We can see that the tip of the EF2000 canard is very close to the wing level and by using positive deflection in order to create the lift, trailing edge of the canard is going even lower [directing the downwash in different manner compared to negative deflection], and at the same time producing the lift induced drag in the form of very strong vortices.
This is also from the NASA paper: "When the canard is in the lower position, the vortices pass below the wing, where they encounter a retardant flow with an unfavorable pressure gradient which accelerates the forward progression of the vortex breakdown."

Like I said, this is my proposed explanation for the aditional use of the flaperons regarding the EF2000 supersonic trimming, that might or might not be wrong

You have a point there, I had not fully realized the plane of the canards is higher than the wing but the tips are quite low, I wonder why this very marked anhedral angle... maybe for roll stability reasons?

A pronounced plane AoA could help the downwash clear the wing but I don't know. I also do not have time to research much, even when there should be a bit of material available about the Eurofighter

Those are placed at the CoG and therefore they need little compensation to be used. Something like that would allow lift to be produced in a plane that could massively help maneouvering, I think the Harrier in fact used their nozzles that way.

Shifting the entire mass of the missile sideways requires a bit of energy... certainly a lot more energy than canards and tail surfaces that just rotate the aircraft around its cg countered only by the slipstream of air flow over the aircraft body.

There was a lot of talk about the Harrier so called Viffing... (ie (engine) Vectoring In Forward Flight), but the reality is that they just were using better model Sidewinders than the Argentines and a subsonic plane manouvers better at subsonic speeds than planes designed for supersonic flight potential flying at subsonic speeds like the Mirage III.

BTW Nice post as usual Mindstorm.... I knew the Hollywood depiction of AAMs as fighter planes that fly at similar speeds to fighter aircraft and almost dogfight their targets.... if they miss they come around again was bullshit... the real world is that it is a slashing attack that comes in super fast... it can veer quite a bit but it does not chase you... it is travelling too fast to turn hard and by this stage has no propulsion to do a 180 degree turn to reacquire you as a target and have another go.

Of course, if the speed of the missile is not substantially higher than that of the aircraft under attack, things change and if they are similar, a chase like the one you describe would happen. On the other hand, if the speed delta between the missile and the aircraft is substantial, then the missile has an easy time predicting where the plane is going to be and will undercut its movements with its superior speed, so it does not actually need to perform such tight turns and bleed so much energy (the target is, so to say, almost "static" compared to itself)

If their speeds are similar but the altitude means the aircrafts control surfaces struggle to impart enough energy to make sharp high g turns then imagine the situation the missile is in with its complete lack of a wing to create lift to keep it airborne and its tiny control surfaces used to steer...

GarryB wrote:If their speeds are similar but the altitude means the aircrafts control surfaces struggle to impart enough energy to make sharp high g turns then imagine the situation the missile is in with its complete lack of a wing to create lift to keep it airborne and its tiny control surfaces used to steer...

If the missile is not substantially faster it is almost guaranteed to fail, high altitude and low altitude. As said they generate lift by speed, not by having big lifting surfaces.

Arrow wrote:So the EF-2000 is also, like the F-22 and Su-57, an aircraft adapted to maneuvering at supersonic speeds at high altitudes?

The Eurofighter was intended as the air superiority platform while Tornado was the strike plane and therefore high kinematics and high altitude performance were prioritised. Wing load is very low with the discussed canard advantages, TWR is very high and the engines have low BPR like it is needed for supersonic flight which in turn helps flying (and turning!) at thigh altitude. AAMs are carried recessed, too. Of course it should be still well behind of what F-22 and especially Su-57 should be capable of, the lack of internal weapons carriage, reduced fuel amount (need to carry EFTs) and therefore limited range, plus clearly lack of TVC are serious limitations. A heavy fighter in the end is best for that role but in terms of wing loading and therefore sustained turn rates delta canard is one of the best options.

Old roadmap for turbine technologies allowing for gas temperatures > 2000K like in F135. I don't know where Russia stands here but related to izd. 30 I find it interesting that the ideas to reach such temperatures seem to be so clear...

If posted before

I have heard that the S-400 have Tracked Israeli- F-16s at a 230km+ range.

Venezuelan su-30mk2 has tracked f-16 at such distance.

S-400 can track f-16 at greater range. Maybe it was only a matter of radar horizon.

To not be hiden by radar horizon the f-16 must have flown above 2300m in altitude.

Those softwares sucks.

A part of the rcs depend on the materials use to build the aircraft and their radar absorbing caracteristics.

The materials use are highly classified, specially for RAM coatings.

The geometry is also not taken into account because they don't materialize stuff like rivets, the front radar transparant nose cone that let pass radar waves for aircraft's own radar but also the real geometry of the engibe that reflects also radar...

Only the design bureau can make such simultion software.

What you find online is bullshit. And most of the time they will use horseshit values from internet like US fanboy estimates of 0.000...002 or 0.0000000...01 for f-35 and f-22 as a scale.

@thegopnik:

Stealthflanker is your guy, I think he has played around with such tools and knows more than a couple of things about radars and RCS.

I believe you have found yourself entertainment for a few years, those issues are not trivial at all. And once you have the 3D model (which is very difficult to get right) you will find the RAM application and depth is not known and you have to assume it, and then you will notice the tool is very limited and is going to produce very different results to professional tools, which in fact are also probably not 100% how the real thing works as seen from a military secret point of view. Just my impression from what I have read and seen, I have not actually had the time, the energy and the balls to go for this seriously. Good luck!

EDIT: Isos has a point, properly simulate apertures can get you a well paid job at a design bureau. This is seriously difficult.

EDIT: Isos has a point, properly simulate apertures can get you a well paid job at a design bureau. This is seriously difficult.

Well that's usefull only before you start producing the prototypes.

Then you can just send the aircraft in the air and turn on a hundred of radar on the ground and in the air to see how good it is.

RAM coating can be tested on old birds. They already painted a mig-21 with radar absorbing paint and showed the indian the difference behind a radar screen. I saw that on a forum and it was made when they bought upgraded for their mig-21Bison.

Isos wrote:Well that's usefull only before you start producing the prototypes.

The layout, forms, finishing and materials need to be chosen out of an infinite variety of options and then go to HW so well, of course the final measurements are needed but the actual design happens before. Now almost all design bureaus are using digital engineering and "digital twins" as the Russians call it (on the last "Horizons" UAC magazine they explain how they created this for the first time for restarting the production of the Tu-160), so each time more time and more tests will be performed on virtual models and less in real world.

@Isos:

There are estimations online about the F-35 RCS, maybe you want to use them instead? I think Mindstorm linked one little time ago

In simulations, one golden rule applies: GIGO (Garbage In, Garbage Out)

Meaning, if your input data is crap and you don't have the actual knowledge (as from a highly trained specialist) it does not matter how much you simulate and with what precision, results are going to suck. I remind a paper addressing the compared aero of F-22 and Su-57, where the physical models were not even close to the real thing and, to make it worse, the aero surfaces were not even deflected as they should for high AoA. The result was close to useless. I say this because simulation is not an easy thing, even when tools are readily available.

@GarryB, @PeregrineFalcon:

the guy linked by zepia keeps delivering, watch this about the foreplanes:

https://www.youtube.com/watch?v=Ny0NjjjJqaA

Isos wrote:

I have heard that the S-400 have Tracked Israeli- F-16s at a 230km+ range.

Venezuelan su-30mk2 has tracked f-16 at such distance.

S-400 can track f-16 at greater range. Maybe it was only a matter of radar horizon.

To not be hiden by radar horizon the f-16 must have flown above 2300m in altitude.

I remember that Israeli F-16i got shot down on the outskirts of Syria in Feb 2018. F-16i's are supposedly loaded with counter measures but the story is that Syria shot it down with an old s-200 missile. This was at a moment where Russia/Israel relations were at a low so it isn't out of possibility that Russia aimed up the s-400 and shot it out of the sky.