By: paralay
- 25th August 2019 at 16:04Permalink- Edited 25th August 2019 at 16:06
- Su-35 weights 3 tons more than Su-27? Why?
Su-35S, the volume of electronic equipment has decreased. Its density if I am not mistaken 320 kg/m3. In its place filled with fuel density of 800 kg/m3. Heavier nozzles and engines with increased resource, they are also heavier. Reinforced wing, now there can be suspended external fuel tanks 2 x 2000 liters. This required strengthening the structure, logically.
Su-57. The selected angles for the nose cone and air intakes clearly indicate a maximum speed of at least M=2.35 (2500 km/h) The selected angle of the leading edge of the wing implies a high cruising speed, probably M=1.78 (1890 km/h)
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By: panzerfeist1
- 25th August 2019 at 16:51Permalink
Su-35S, the volume of electronic equipment has decreased. Its density if I am not mistaken 320 kg/m3. In its place filled with fuel density of 800 kg/m3.
I am referring to empty weight, which in your table is 19,300 kg. I need to check in detail, but Su-27 was less than 17 tons if don't remember wrong.
Heavier nozzles and engines with increased resource, they are also heavier.
According to Rosoboronexport, the Al-41F1S is 84 kg heavier, so 168 kg difference, you are right. AL-41F1 is supposedly lighter, 150 kg less than AL-31F.
Reinforced wing, now there can be suspended external fuel tanks 2 x 2000 liters. This required strengthening the structure, logically.
True, this may be a major contributor but I assume modern production and materials should help increase the resistance of the structure with little weight increase. If not, all the progress in the engines would be negated by the increase in empty weight and Sukhoi would fail to improve the kinematic behaviour of the plane.
Su-57. The selected angles for the nose cone and air intakes clearly indicate a maximum speed of at least M=2.35 (2500 km/h) The selected angle of the leading edge of the wing implies a high cruising speed, probably M=1.78 (1890 km/h)
I tend to agree and would stretch those figures even a bit further. Latest data I saw which seemed half reliable (a supposed expert whose article I need to dig up) indicated cruise speed 2 M, max speed 2.45 M (2600 km/h). Few months before I would have thought this to be far fetched, now after reading Marchukov and the patent I tend to think it is actually realistic:
- No reason for 15 years of delay to create a weapon against F-22 which is clearly inferior from the beginning. F-22 can supposedly cruise at 1.82 M, max speed is 2.25 M IIRC
- Izd. 30 is stated as being the engine with highest specific thrust in its category available anywhere.
- Supercruising performance is one of the main design focus of the plane, as stated in the patent and obvious from many design traits.
- It makes no sense to incur the effort and expense of designing a variable intake which is only better above 2 M (as stated in the very patent) if your maximum speed is not substantially higher than that.
- F-15 is still very much in service and will continue to do so for the foreseeable future. Its max. speed is 2.5 M, so it makes sense for Su-57 to be at that level too, in order to dominate the engagements with superior range and markedly better cruising speed / acceleration.
USAF's best chance IMO is to bring AETP engines to the F-22/ F-15 / F-35 fleet, in order to counter the more than probable advantage in kinematics of the Su-57.
Hmm so I guess the stealth problem in the back will be addessed in the future regarding this mock up design of the SU-70?
Indeed it looks like this is the plan. Coherent with the design of a stealthy, subsonic deep strike and intelligence platform that cannot rely on kinematics to defeat air defence.
Su-27 early series had an empty weight 16380 kg. Later series, including Su-27SK - 17500 kg
Ok thanks, I will research a bit on that
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By: panzerfeist1
- 25th August 2019 at 19:26Permalink
I am hoping for something more grandiose like an internal scramjet missile placement for an SU-57, KRET showcasing FICs based jammers or radars, avionics layout of the okhotnik, showcase mockup model of a mig-41, etc etc. The last airshow seemed boring I hope it wont be the case for this one.
By: paralay
- 25th August 2019 at 20:27Permalink- Edited 25th August 2019 at 20:28
Su-27SK (flight manual)
27380 kg - 9220 kg (fuel) - 726 kg (2R27+2R73) - 100 kg (pilot) - 58 kg (shells) = 17276 kg
23250 kg - 5090 kg (fuel) - 726 kg (2R27+2R73) - 100 kg (pilot) - 58 kg (shells) = 17276 kg
not taken into account the links of the tape GSH-301
By: Scorpion82
- 26th August 2019 at 10:47Permalink
Su-27SK (flight manual)
27380 kg - 9220 kg (fuel) - 726 kg (2R27+2R73) - 100 kg (pilot) - 58 kg (shells) = 17276 kg
23250 kg - 5090 kg (fuel) - 726 kg (2R27+2R73) - 100 kg (pilot) - 58 kg (shells) = 17276 kg
not taken into account the links of the tape GSH-301
Not taken into account appear to be the pylons, unusable fuel and consumables incl. hydraulic fluid, lubricating oil and chaff/flare rounds for loaded dispensers.
By: LMFS
- 26th August 2019 at 21:31Permalink- Edited 26th August 2019 at 21:32
This one again confirms that 117 Engine can supercruise PAK-FA
It is unclear if they refer to Su-57 with current engines or not...
In any case it is not the same to "supercruise" at 1.8 or 2 M than barely maintaining M > 1 for some minutes. The first has a clear tactical value, the later, not really. We don't know what the izd. 117 allows to do. The designers said that it fulfilled the MoD requirements, but clearly an engine as izd. 30 (designed for supercruise) should improve over that by a big margin, so what were the original requirements? Was there a "nice to have" requirement that latter evolved into a "must", as the progress with the design of the izd. 30 allowed for more ambitious goals? IMHO and all that being considered, the Su-57 with the current engine maybe cruises at 1.2 - 1.3 M, maybe 1.5 M being very optimistic, with the second stage engines should be close to 2 M.
By: RadDisconnect
- 26th August 2019 at 21:53Permalink- Edited 26th August 2019 at 22:07
I tend to agree and would stretch those figures even a bit further. Latest data I saw which seemed half reliable (a supposed expert whose article I need to dig up) indicated cruise speed 2 M, max speed 2.45 M (2600 km/h). Few months before I would have thought this to be far fetched, now after reading Marchukov and the patent I tend to think it is actually realistic:
- No reason for 15 years of delay to create a weapon against F-22 which is clearly inferior from the beginning. F-22 can supposedly cruise at 1.82 M, max speed is 2.25 M IIRC
- Izd. 30 is stated as being the engine with highest specific thrust in its category available anywhere.
- Supercruising performance is one of the main design focus of the plane, as stated in the patent and obvious from many design traits.
- It makes no sense to incur the effort and expense of designing a variable intake which is only better above 2 M (as stated in the very patent) if your maximum speed is not substantially higher than that.
- F-15 is still very much in service and will continue to do so for the foreseeable future. Its max. speed is 2.5 M, so it makes sense for Su-57 to be at that level too, in order to dominate the engagements with superior range and markedly better cruising speed / acceleration.
USAF's best chance IMO is to bring AETP engines to the F-22/ F-15 / F-35 fleet, in order to counter the more than probable advantage in kinematics of the Su-57.
Only reference to "Mach 2" supercruise has been hearsay from "radioscanners" that Berkut (who got banned here for some reason) states to be false. I've asked on Secret Projects and both flateric and Berkut (he's called Flanker on Secret Projects) reject it. Besides, flateric points out the ORIGINAL max speed requirement was Mach 2.35, and in 2006 that was actually reduced a bit because of structures and materials. Also I don't think there would be dedicated PAK-DP program if PAK-FA is meant to have Mach 2 supercruise.
Though in all honesty the king of speed for fighters would probably have been F-23, that has better area ruling than any fighter, but it didn't get chosen.
Also, AETP is meant to improve acceleration and fuel efficiency in F-22 and F-35, not speed. In fact if you see F-35 flight envelope you see that the flight performance just cuts off at Mach 1.6 instead of having a curve that stops at Mach 1.6. This means F-35 is not limited to Mach 1.6 by drag, but it's an "imposed" limit, so even with more powerful engine the max speed is not going to change.
Supercruise is at least Mach 1.78 according to LM. https://aviationweek.com/awin/f-22-design-shows-more-expected
Most publications such as AFM and Air International puts it at Mach 1.82 and general consensus is Mach 1.8. But F-22 makes some pretty big sacrifices to supercruise at this speed, such as quite low bypass engines that are pretty thirsty, and also very tapered rear fuselage which reduce wave drag but also reduces quite a bit of fuel volume, so range is not great. Also weapon bay is quite shallow.
By: RadDisconnect
- 26th August 2019 at 21:57Permalink
It is unclear if they refer to Su-57 with current engines or not...
In any case it is not the same to "supercruise" at 1.8 or 2 M than barely maintaining M > 1 for some minutes. The first has a clear tactical value, the later, not really. We don't know what the izd. 117 allows to do. The designers said that it fulfilled the MoD requirements, but clearly an engine as izd. 30 (designed for supercruise) should improve over that by a big margin, so what were the original requirements? Was there a "nice to have" requirement that latter evolved into a "must", as the progress with the design of the izd. 30 allowed for more ambitious goals? IMHO and all that being considered, the Su-57 with the current engine maybe cruises at 1.2 - 1.3 M, maybe 1.5 M being very optimistic, with the second stage engines should be close to 2 M.
If izd.117 allows supercruise of Mach 1.3, then it's VERY unrealistic for izd.30 to give Mach 2 supercruise because once you're out of transsonic and in supersonic, drag is pretty much increases with square of speed, so Mach 2 drag is 78% higher than Mach 1.5 and 136% higher than at Mach 1.3. So while izd.30 will definitely be big improvement over izd.117, it won't be THAT big.
By: LMFS
- 27th August 2019 at 01:41Permalink- Edited 27th August 2019 at 01:50
Only reference to "Mach 2" supercruise has been hearsay from "radioscanners" that Berkut (who got banned here for some reason) states to be false.
I have read it as of late a couple of times, once from a guy that had name and reputation. I will try to find it.
I've asked on Secret Projects and both flateric and Berkut (he's called Flanker on Secret Projects) reject it.
Well, don't forget that perspective and available sources change with time. Besides those two persons, which I just know by reference, may not know all about PAK-FA. And if they know, they will better not say anything because they know for sure what consequences disclosing info in forums can have.
Besides, flateric points out the ORIGINAL max speed requirement was Mach 2.35, and in 2006 that was actually reduced a bit because of structures and materials.
The keels would have needed reinforcement, this is a known story. But were they meaning max speed or max cruising speed without time limitations? I cannot be 100% sure. The argument of the intakes speaks IMO quite clearly in favour of max speed beyond 2 M.
Also I don't think there would be dedicated PAK-DP program if PAK-FA is meant to have Mach 2 supercruise.
PAK-DP will be an interceptor where the constraints of a multirole design will be cast aside. That means, min drag instead of max lift, huge fuel load, specialised engines and so on. It is supposed to be highly supersonic (4 M) and have long range, probably quite a big beast born out of the need to fight future hypersonic threats, very different to the PAK-FA.
The 2 M supercruise would respond to the reality that F-22 is essentially there already, so being in that ballpark is a need. And PCA is claimed to be about speed, range and payload again, so Russia needs a bit of margin beyond F-22.
Though in all honesty the king of speed for fighters would probably have been F-23, that has better area ruling than any fighter, but it didn't get chosen.
And not less importantly, YF120 was also not chosen. But now time has passed and Russia may decide differently to the US and go for a more ambitious approach.
Also, AETP is meant to improve acceleration and fuel efficiency in F-22 and F-35, not speed.
Cruising speed yes, since it will notably increase the thrust in mil settings. Ratio between mil and max thrust will change greatly as far as I know.
Beyond the gains due to pure technological progress between engine generations, the layout change will bring more subsonic range to the F-22 and maybe some lelvel of supersonic cruise to the F-35.
In fact if you see F-35 flight envelope you see that the flight performance just cuts off at Mach 1.6 instead of having a curve that stops at Mach 1.6. This means F-35 is not limited to Mach 1.6 by drag, but it's an "imposed" limit, so even with more powerful engine the max speed is not going to change.
Probably true, maybe due to maintenance requirements for the coatings or restrains on dynamic pressures (maybe born of weight-out measures?). It seems self-imposed in any case, so may be changed in the future if the conditions change too.
Most publications such as AFM and Air International puts it at Mach 1.82 and general consensus is Mach 1.8. But F-22 makes some pretty big sacrifices to supercruise at this speed, such as quite low bypass engines that are pretty thirsty,
That is the crucial question, do you sacrifice operational cost and range for the whole operational life of the aircraft to be a beast in kinematics during some brief fight moments? Or do you favour a high bypass engine, even when it will not be capable of supercruising? Russians seem to be convinced of wanting both range and speed, at least from what I read this is the key behind izd. 30.
and also very tapered rear fuselage which reduce wave drag but also reduces quite a bit of fuel volume, so range is not great. Also weapon bay is quite shallow
That is why the layout of the PAK-FA is so special. They managed big bays but placed them one after the other along the longitudinal axis of the plane and in the shadow of the unavoidable, drag-generating nose & cockpit sections, so pretty much got that volume for free. Fuel capacity is granted by the extremely developed blended wing-body design. The rear fuselage usually holds not much fuel in almost any plane, with maybe the F-35 holding a bit more than normal. The problem with the fuel in the F-22 is that it has a very short middle fuselage section, together with volume-eating S-shaped air ducts and outright huge side weapon bays. Together with the low BPR engines, this creates a certain lack of range which poses a challenge if the plane has to operate in a contested airspace of a certain depth, a good reason why PCA is being fast tracked instead of modernizing the 22.
If izd.117 allows supercruise of Mach 1.3, then it's VERY unrealistic for izd.30 to give Mach 2 supercruise because once you're out of transsonic and in supersonic, drag is pretty much increases with square of speed, so Mach 2 drag is 78% higher than Mach 1.5 and 136% higher than at Mach 1.3. So while izd.30 will definitely be big improvement over izd.117, it won't be THAT big.
First of all, I don't have any proof and also have not made numbers, good or bad about that speed. But I think others would go along that figure of M1.3 for izd. 117 so I will follow your reasoning.
The drag question: what you say is true but not all the truth, since Cd changes with the speed and decreases notably, well beyond the transonic region. This change depends on the particular design, and judging by the wing sweep for instance, supersonic performance was a big issue for the Su-57, as the patent also confirms. Area rule is very apparent too.
The issue with izd. 30 and izd. 117 is that the first is not a further evolution of the later or even keeping the same layout, so you cannot estimate its thrust as a pure linear progression from the older model. Not only has it a very much reduced number of stages but most crucially it has been designed specifically for supercruise. This is proven not only by the many times this requirement is argued by officials and designers as the justification for spending even more money after the already modern izd. 117 was completed and tested, but the words of its lead designer confirm the crucial parameter of such an engine, specific thrust, to be the highest available in any engine of that category. So either they have way higher temps and compression than the F119 (improbable) or they have lower BPR.
Think of it this way: what mil thrust does F-22 need to fly 1.82 M? 11-12 tf/engine, to account for detuned specs. Izd 117S, which is a bit worse than 117 but of the same design, 8.8 tf. That is a massive 25% - 35% difference. That level of thrust is similar to what an engine of the F100-AL-31F generation needed to propel 4G jets beyond 2 M. Intakes in the Su-57 are simply huge with the best pressure recovery due to adjustable ramps and relatively straight air ducts, and besides the ram compression will keep adding thrust to the engines as the speed increases. So not so crazy IMHO to think that a carefully designed fighter whose cross-sectional area is not bigger than that of a Flanker can get to that speed with engines capable of 12 or more Tf. The exact number will maybe never known but this estimation makes reasonably good sense to me...
It is unclear if they refer to Su-57 with current engines or not...
In any case it is not the same to "supercruise" at 1.8 or 2 M than barely maintaining M > 1 for some minutes. The first has a clear tactical value, the later, not really. We don't know what the izd. 117 allows to do. The designers said that it fulfilled the MoD requirements, but clearly an engine as izd. 30 (designed for supercruise) should improve over that by a big margin, so what were the original requirements? Was there a "nice to have" requirement that latter evolved into a "must", as the progress with the design of the izd. 30 allowed for more ambitious goals? IMHO and all that being considered, the Su-57 with the current engine maybe cruises at 1.2 - 1.3 M, maybe 1.5 M being very optimistic, with the second stage engines should be close to 2 M.
IF you read the full quote they are referring to current engine , You cannot talk about something that does not exist other than prototype.
The interview of Deputy Chief of RuAF I posted also spoke of Supercruise exist for PAK-FA.
As far as SC at what mach number I think that would vary depending on Fuel load and weapons load it is carrying.
By: RadDisconnect
- 27th August 2019 at 07:34Permalink- Edited 27th August 2019 at 08:37
That is why the layout of the PAK-FA is so special. They managed big bays but placed them one after the other along the longitudinal axis of the plane and in the shadow of the unavoidable, drag-generating nose & cockpit sections, so pretty much got that volume for free. Fuel capacity is granted by the extremely developed blended wing-body design. The rear fuselage usually holds not much fuel in almost any plane, with maybe the F-35 holding a bit more than normal. The problem with the fuel in the F-22 is that it has a very short middle fuselage section, together with volume-eating S-shaped air ducts and outright huge side weapon bays. Together with the low BPR engines, this creates a certain lack of range which poses a challenge if the plane has to operate in a contested airspace of a certain depth, a good reason why PCA is being fast tracked instead of modernizing the 22.
F-22 does have two major fuel tanks in rear fuselage by engine bays where it is much slimmer compared to YF-22 prototype.
First of all, I don't have any proof and also have not made numbers, good or bad about that speed. But I think others would go along that figure of M1.3 for izd. 117 so I will follow your reasoning.
The drag question: what you say is true but not all the truth, since Cd changes with the speed and decreases notably, well beyond the transonic region. This change depends on the particular design, and judging by the wing sweep for instance, supersonic performance was a big issue for the Su-57, as the patent also confirms. Area rule is very apparent too.
When you get out of transsonic and into supersonic at Mach 1.2 or more drag coefficient does not decrease that much.
Look at even some of the most area ruled aircraft ever made like RA5C and XB-70, these have much better fineness ratio than any 5G fighter.
The issue with izd. 30 and izd. 117 is that the first is not a further evolution of the later or even keeping the same layout, so you cannot estimate its thrust as a pure linear progression from the older model. Not only has it a very much reduced number of stages but most crucially it has been designed specifically for supercruise. This is proven not only by the many times this requirement is argued by officials and designers as the justification for spending even more money after the already modern izd. 117 was completed and tested, but the words of its lead designer confirm the crucial parameter of such an engine, specific thrust, to be the highest available in any engine of that category. So either they have way higher temps and compression than the F119 (improbable) or they have lower BPR.
Think of it this way: what mil thrust does F-22 need to fly 1.82 M? 11-12 tf/engine, to account for detuned specs. Izd 117S, which is a bit worse than 117 but of the same design, 8.8 tf. That is a massive 25% - 35% difference. That level of thrust is similar to what an engine of the F100-AL-31F generation needed to propel 4G jets beyond 2 M. Intakes in the Su-57 are simply huge with the best pressure recovery due to adjustable ramps and relatively straight air ducts, and besides the ram compression will keep adding thrust to the engines as the speed increases. So not so crazy IMHO to think that a carefully designed fighter whose cross-sectional area is not bigger than that of a Flanker can get to that speed with engines capable of 12 or more Tf. The exact number will maybe never known but this estimation makes reasonably good sense to me...
Obviously dynamic thrust is harder to estimate but assuming izd.30 can get twice the dynamic thrust of izd.117, which was already much more optimized for supercruise compare to base AL-31F is questionable. You can't directly compare afterburning thrust of F100 to military thrust of F119, their dynamic thrust profile will be different since afterburner increases exhaust temperature behind the turbine where the combustion gasses already went through some expansion.
By: LMFS
- 27th August 2019 at 13:47Permalink- Edited 27th August 2019 at 14:01
IF you read the full quote they are referring to current engine , You cannot talk about something that does not exist other than prototype.
The interview of Deputy Chief of RuAF I posted also spoke of Supercruise exist for PAK-FA.
I am not so sure, but it is just my opinion. In any case they are not being precise. A said, it is not the same 1.1 M than 1.8. And they by now know for sure the final performance of the plane with the second stage engine with almost total certainty.
If it was not because izd. 30 brings much better cruising speed, why would they bother designing it, so close after having done the izd. 117 with a max thrust almost in the level of the F119?
As far as SC at what mach number I think that would vary depending on Fuel load and weapons load it is carrying.
Would vary indeed but I assume it would be by a small margin, given the internal carriage of weapons and low wing loading of the plane.
F-22 does have two major fuel tanks in rear fuselage by engine bays where it is much slimmer compared to YF-22 prototype.
I will check that, thanks
When you get out of transsonic and into supersonic at Mach 1.2 or more drag coefficient does not decrease that much.
Look at even some of the most area ruled aircraft ever made like RA5C and XB-70, these have much better fineness ratio than any 5G fighter.
Wow XB-70's Cd is ridiculous... I have seen other drawings with much steeper reductions of Cd as speed increases, it depends on the design and I cannot make statements about how it behaves in the Su-57. Keep in mind the trimming options they have with the TVC and LEVCONS to reduce drag in supersonic flight too, everything in the design has been conditioned by this flight regime. Of course, I am aware that drag increases non linearly with speed, but the fact that F-22 can cruise so fast with an engine size and cross sectional area very close to Su-57 despite allegedly not being as aerodynamic as the YF-23 supports that a cruising speed in that ballpark for the Su-57 is perfectly possible, besides being a logical design goal both for the plane and for the second stage engine, designed as said above immediately after the 117 was developed and hence still up to date. As argued other evidence suggest that the installed thrust of the 30 is equal or bigger than F119, maybe the radar blockers being the only negative issue I can think of.
Obviously dynamic thrust is harder to estimate but assuming izd.30 can get twice the dynamic thrust of izd.117, which was already much more optimized for supercruise compare to base AL-31F is questionable. You can't directly compare afterburning thrust of F100 to military thrust of F119, their dynamic thrust profile will be different since afterburner increases exhaust temperature behind the turbine where the combustion gasses already went through some expansion.
Why twice the dynamic thrust of izd. 117? I simply assume it will be equal or better than F119's, that has as said 25-35% more uninstalled mil thrust, mainly due to lower BPR. A change in BPR between izd. 117 and 30 would get most of the work done, I assume.
Re. the different thrust profiles w/ and w/o AB, I am aware the comparison is decidedly rough but still applicable. Do you have some data to help refining it?
BTW, it seems today is a busy day showing the Su-57 :D
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By: RadDisconnect
- 27th August 2019 at 14:44Permalink- Edited 27th August 2019 at 18:21
If it was not because izd. 30 brings much better cruising speed, why would they bother designing it, so close after having done the izd. 117 with a max thrust almost in the level of the F119?
One of the stated goals of izd.30 is lower maintenance and operating cost. Especially since izd.117 is considered not economical to run. More power is not the only goal of izd.30, higher MTBO and better operating economy are major goals.
Wow XB-70's Cd is ridiculous... I have seen other drawings with much steeper reductions of Cd as speed increases, it depends on the design and I cannot make statements about how it behaves in the Su-57. Keep in mind the trimming options they have with the TVC and LEVCONS to reduce drag in supersonic flight too, everything in the design has been conditioned by this flight regime. Of course, I am aware that drag increases non linearly with speed, but the fact that F-22 can cruise so fast with an engine size and cross sectional area very close to Su-57 despite allegedly not being as aerodynamic as the YF-23 supports that a cruising speed in that ballpark for the Su-57 is perfectly possible, besides being a logical design goal both for the plane and for the second stage engine, designed as said above immediately after the 117 was developed and hence still up to date. As argued other evidence suggest that the installed thrust of the 30 is equal or bigger than F119, maybe the radar blockers being the only negative issue I can think of.
The much steeper reduction in drag coefficient when Mach increases is for only individual components like the wing or a generic object. When you have a whole aircraft the total supersonic parasite drag buildup will include things like shockwave interference and total area rule and volume distribution. So even with a dedicated interceptor like F-106 where drag reduction was emphasized over pretty much everything else you don't see that steep kind of drag coefficient reduction of just a component.
XB-70 drag coefficient is low because wing is huge (drag force is drag coefficient times dynamic pressure times wing area), and also that aircraft is optimized to the extreme for supersonic flight. Also small wings is why F-104 drag coefficient is so high even though actual drag is actually very low.
Why twice the dynamic thrust of izd. 117? I simply assume it will be equal or better than F119's, that has as said 25-35% more uninstalled mil thrust, mainly due to lower BPR. A change in BPR between izd. 117 and 30 would get most of the work done, I assume.
Re. the different thrust profiles w/ and w/o AB, I am aware the comparison is decidedly rough but still applicable. Do you have some data to help refining it?
~35% increase in thrust will get you from Mach 1.3 to Mach 1.6-1.7 at best. For example YF-22 supercruise speed is Mach 1.43 with YF119 and Mach 1.58 with YF120 which is 20% more powerful because of the YF119 didn't have the bigger fan for increase mass flow of production F119, while YF120 did.
Posts: 1,344
By: paralay - 25th August 2019 at 16:04 Permalink - Edited 25th August 2019 at 16:06
Su-35S, the volume of electronic equipment has decreased. Its density if I am not mistaken 320 kg/m3. In its place filled with fuel density of 800 kg/m3. Heavier nozzles and engines with increased resource, they are also heavier. Reinforced wing, now there can be suspended external fuel tanks 2 x 2000 liters. This required strengthening the structure, logically.
Su-57. The selected angles for the nose cone and air intakes clearly indicate a maximum speed of at least M=2.35 (2500 km/h) The selected angle of the leading edge of the wing implies a high cruising speed, probably M=1.78 (1890 km/h)
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By: panzerfeist1 - 25th August 2019 at 16:51 Permalink
thanks lmfs for the guys twitter account. https://twitter.com/MuxelAero/status/1165216612338868230
I hope they have more newer weapons than just those 2.
Posts: 484
By: LMFS - 25th August 2019 at 17:35 Permalink
I am referring to empty weight, which in your table is 19,300 kg. I need to check in detail, but Su-27 was less than 17 tons if don't remember wrong.
According to Rosoboronexport, the Al-41F1S is 84 kg heavier, so 168 kg difference, you are right. AL-41F1 is supposedly lighter, 150 kg less than AL-31F.
True, this may be a major contributor but I assume modern production and materials should help increase the resistance of the structure with little weight increase. If not, all the progress in the engines would be negated by the increase in empty weight and Sukhoi would fail to improve the kinematic behaviour of the plane.
I tend to agree and would stretch those figures even a bit further. Latest data I saw which seemed half reliable (a supposed expert whose article I need to dig up) indicated cruise speed 2 M, max speed 2.45 M (2600 km/h). Few months before I would have thought this to be far fetched, now after reading Marchukov and the patent I tend to think it is actually realistic:
- No reason for 15 years of delay to create a weapon against F-22 which is clearly inferior from the beginning. F-22 can supposedly cruise at 1.82 M, max speed is 2.25 M IIRC
- Izd. 30 is stated as being the engine with highest specific thrust in its category available anywhere.
- Supercruising performance is one of the main design focus of the plane, as stated in the patent and obvious from many design traits.
- It makes no sense to incur the effort and expense of designing a variable intake which is only better above 2 M (as stated in the very patent) if your maximum speed is not substantially higher than that.
- F-15 is still very much in service and will continue to do so for the foreseeable future. Its max. speed is 2.5 M, so it makes sense for Su-57 to be at that level too, in order to dominate the engagements with superior range and markedly better cruising speed / acceleration.
USAF's best chance IMO is to bring AETP engines to the F-22/ F-15 / F-35 fleet, in order to counter the more than probable advantage in kinematics of the Su-57.
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By: paralay - 25th August 2019 at 17:51 Permalink
Su-27 early series had an empty weight 16380 kg. Later series, including Su-27SK - 17500 kg
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By: LMFS - 25th August 2019 at 19:00 Permalink
Indeed it looks like this is the plan. Coherent with the design of a stealthy, subsonic deep strike and intelligence platform that cannot rely on kinematics to defeat air defence.
Ok thanks, I will research a bit on that
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By: panzerfeist1 - 25th August 2019 at 19:26 Permalink
Damn not even the MAKS airshow has started and we are getting information like this https://twitter.com/KomissarWhipla/status/1165310972661252097 an IL-76 using scramjet missiles.
I am hoping for something more grandiose like an internal scramjet missile placement for an SU-57, KRET showcasing FICs based jammers or radars, avionics layout of the okhotnik, showcase mockup model of a mig-41, etc etc. The last airshow seemed boring I hope it wont be the case for this one.
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By: JSR - 25th August 2019 at 19:54 Permalink
Su-27SK weight is about 16.8 tons. range with 9.4 tons fuel and 4AAM 3530 km.
http://www.sukhoi.org/products/earlier/251/
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By: paralay - 25th August 2019 at 20:27 Permalink - Edited 25th August 2019 at 20:28
Su-27SK (flight manual)
27380 kg - 9220 kg (fuel) - 726 kg (2R27+2R73) - 100 kg (pilot) - 58 kg (shells) = 17276 kg
23250 kg - 5090 kg (fuel) - 726 kg (2R27+2R73) - 100 kg (pilot) - 58 kg (shells) = 17276 kg
not taken into account the links of the tape GSH-301
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By: Scorpion82 - 26th August 2019 at 10:47 Permalink
Not taken into account appear to be the pylons, unusable fuel and consumables incl. hydraulic fluid, lubricating oil and chaff/flare rounds for loaded dispensers.
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By: paralay - 26th August 2019 at 16:18 Permalink
fuel 9400 kg - 9220 kg = 180 kg
2 APU-410 + 2 P-72 = 2 * 70 kg + 2 * 49 kg = 140 kg + 98 kg = 238 kg
96 traps (thick fins) * 1 kg = 96 kg
17276 kg - 180 kg - 238 kg - 96 kg = 16762 kg
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By: LMFS - 26th August 2019 at 21:31 Permalink - Edited 26th August 2019 at 21:32
It is unclear if they refer to Su-57 with current engines or not...
In any case it is not the same to "supercruise" at 1.8 or 2 M than barely maintaining M > 1 for some minutes. The first has a clear tactical value, the later, not really. We don't know what the izd. 117 allows to do. The designers said that it fulfilled the MoD requirements, but clearly an engine as izd. 30 (designed for supercruise) should improve over that by a big margin, so what were the original requirements? Was there a "nice to have" requirement that latter evolved into a "must", as the progress with the design of the izd. 30 allowed for more ambitious goals? IMHO and all that being considered, the Su-57 with the current engine maybe cruises at 1.2 - 1.3 M, maybe 1.5 M being very optimistic, with the second stage engines should be close to 2 M.
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By: TR1 - 26th August 2019 at 21:32 Permalink
https://missiles2go.ru/
Interesting, might this be Orion-2 drone?
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By: RadDisconnect - 26th August 2019 at 21:53 Permalink - Edited 26th August 2019 at 22:07
Only reference to "Mach 2" supercruise has been hearsay from "radioscanners" that Berkut (who got banned here for some reason) states to be false. I've asked on Secret Projects and both flateric and Berkut (he's called Flanker on Secret Projects) reject it. Besides, flateric points out the ORIGINAL max speed requirement was Mach 2.35, and in 2006 that was actually reduced a bit because of structures and materials. Also I don't think there would be dedicated PAK-DP program if PAK-FA is meant to have Mach 2 supercruise.
Though in all honesty the king of speed for fighters would probably have been F-23, that has better area ruling than any fighter, but it didn't get chosen.
Also, AETP is meant to improve acceleration and fuel efficiency in F-22 and F-35, not speed. In fact if you see F-35 flight envelope you see that the flight performance just cuts off at Mach 1.6 instead of having a curve that stops at Mach 1.6. This means F-35 is not limited to Mach 1.6 by drag, but it's an "imposed" limit, so even with more powerful engine the max speed is not going to change.
https://i.imgur.com/mhUOqyV.png
No weight for this envelope was given, so we don't know what load it is.
Also, the F-22 numbers seem a bit inaccurate in this sheet.
http://paralay.world/paralay_tab.xls
Supercruise is at least Mach 1.78 according to LM.
https://aviationweek.com/awin/f-22-design-shows-more-expected
Most publications such as AFM and Air International puts it at Mach 1.82 and general consensus is Mach 1.8. But F-22 makes some pretty big sacrifices to supercruise at this speed, such as quite low bypass engines that are pretty thirsty, and also very tapered rear fuselage which reduce wave drag but also reduces quite a bit of fuel volume, so range is not great. Also weapon bay is quite shallow.
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By: RadDisconnect - 26th August 2019 at 21:57 Permalink
If izd.117 allows supercruise of Mach 1.3, then it's VERY unrealistic for izd.30 to give Mach 2 supercruise because once you're out of transsonic and in supersonic, drag is pretty much increases with square of speed, so Mach 2 drag is 78% higher than Mach 1.5 and 136% higher than at Mach 1.3. So while izd.30 will definitely be big improvement over izd.117, it won't be THAT big.
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By: LMFS - 27th August 2019 at 01:41 Permalink - Edited 27th August 2019 at 01:50
I have read it as of late a couple of times, once from a guy that had name and reputation. I will try to find it.
Well, don't forget that perspective and available sources change with time. Besides those two persons, which I just know by reference, may not know all about PAK-FA. And if they know, they will better not say anything because they know for sure what consequences disclosing info in forums can have.
The keels would have needed reinforcement, this is a known story. But were they meaning max speed or max cruising speed without time limitations? I cannot be 100% sure. The argument of the intakes speaks IMO quite clearly in favour of max speed beyond 2 M.
PAK-DP will be an interceptor where the constraints of a multirole design will be cast aside. That means, min drag instead of max lift, huge fuel load, specialised engines and so on. It is supposed to be highly supersonic (4 M) and have long range, probably quite a big beast born out of the need to fight future hypersonic threats, very different to the PAK-FA.
The 2 M supercruise would respond to the reality that F-22 is essentially there already, so being in that ballpark is a need. And PCA is claimed to be about speed, range and payload again, so Russia needs a bit of margin beyond F-22.
And not less importantly, YF120 was also not chosen. But now time has passed and Russia may decide differently to the US and go for a more ambitious approach.
Cruising speed yes, since it will notably increase the thrust in mil settings. Ratio between mil and max thrust will change greatly as far as I know.
Beyond the gains due to pure technological progress between engine generations, the layout change will bring more subsonic range to the F-22 and maybe some lelvel of supersonic cruise to the F-35.
Probably true, maybe due to maintenance requirements for the coatings or restrains on dynamic pressures (maybe born of weight-out measures?). It seems self-imposed in any case, so may be changed in the future if the conditions change too.
That is the crucial question, do you sacrifice operational cost and range for the whole operational life of the aircraft to be a beast in kinematics during some brief fight moments? Or do you favour a high bypass engine, even when it will not be capable of supercruising? Russians seem to be convinced of wanting both range and speed, at least from what I read this is the key behind izd. 30.
That is why the layout of the PAK-FA is so special. They managed big bays but placed them one after the other along the longitudinal axis of the plane and in the shadow of the unavoidable, drag-generating nose & cockpit sections, so pretty much got that volume for free. Fuel capacity is granted by the extremely developed blended wing-body design. The rear fuselage usually holds not much fuel in almost any plane, with maybe the F-35 holding a bit more than normal. The problem with the fuel in the F-22 is that it has a very short middle fuselage section, together with volume-eating S-shaped air ducts and outright huge side weapon bays. Together with the low BPR engines, this creates a certain lack of range which poses a challenge if the plane has to operate in a contested airspace of a certain depth, a good reason why PCA is being fast tracked instead of modernizing the 22.
First of all, I don't have any proof and also have not made numbers, good or bad about that speed. But I think others would go along that figure of M1.3 for izd. 117 so I will follow your reasoning.
The drag question: what you say is true but not all the truth, since Cd changes with the speed and decreases notably, well beyond the transonic region. This change depends on the particular design, and judging by the wing sweep for instance, supersonic performance was a big issue for the Su-57, as the patent also confirms. Area rule is very apparent too.
The issue with izd. 30 and izd. 117 is that the first is not a further evolution of the later or even keeping the same layout, so you cannot estimate its thrust as a pure linear progression from the older model. Not only has it a very much reduced number of stages but most crucially it has been designed specifically for supercruise. This is proven not only by the many times this requirement is argued by officials and designers as the justification for spending even more money after the already modern izd. 117 was completed and tested, but the words of its lead designer confirm the crucial parameter of such an engine, specific thrust, to be the highest available in any engine of that category. So either they have way higher temps and compression than the F119 (improbable) or they have lower BPR.
Think of it this way: what mil thrust does F-22 need to fly 1.82 M? 11-12 tf/engine, to account for detuned specs. Izd 117S, which is a bit worse than 117 but of the same design, 8.8 tf. That is a massive 25% - 35% difference. That level of thrust is similar to what an engine of the F100-AL-31F generation needed to propel 4G jets beyond 2 M. Intakes in the Su-57 are simply huge with the best pressure recovery due to adjustable ramps and relatively straight air ducts, and besides the ram compression will keep adding thrust to the engines as the speed increases. So not so crazy IMHO to think that a carefully designed fighter whose cross-sectional area is not bigger than that of a Flanker can get to that speed with engines capable of 12 or more Tf. The exact number will maybe never known but this estimation makes reasonably good sense to me...
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By: Austin - 27th August 2019 at 06:12 Permalink
IF you read the full quote they are referring to current engine , You cannot talk about something that does not exist other than prototype.
The interview of Deputy Chief of RuAF I posted also spoke of Supercruise exist for PAK-FA.
As far as SC at what mach number I think that would vary depending on Fuel load and weapons load it is carrying.
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By: RadDisconnect - 27th August 2019 at 07:34 Permalink - Edited 27th August 2019 at 08:37
F-22 does have two major fuel tanks in rear fuselage by engine bays where it is much slimmer compared to YF-22 prototype.
When you get out of transsonic and into supersonic at Mach 1.2 or more drag coefficient does not decrease that much.
Look at even some of the most area ruled aircraft ever made like RA5C and XB-70, these have much better fineness ratio than any 5G fighter.
Obviously dynamic thrust is harder to estimate but assuming izd.30 can get twice the dynamic thrust of izd.117, which was already much more optimized for supercruise compare to base AL-31F is questionable. You can't directly compare afterburning thrust of F100 to military thrust of F119, their dynamic thrust profile will be different since afterburner increases exhaust temperature behind the turbine where the combustion gasses already went through some expansion.
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By: LMFS - 27th August 2019 at 13:47 Permalink - Edited 27th August 2019 at 14:01
I am not so sure, but it is just my opinion. In any case they are not being precise. A said, it is not the same 1.1 M than 1.8. And they by now know for sure the final performance of the plane with the second stage engine with almost total certainty.
If it was not because izd. 30 brings much better cruising speed, why would they bother designing it, so close after having done the izd. 117 with a max thrust almost in the level of the F119?
Would vary indeed but I assume it would be by a small margin, given the internal carriage of weapons and low wing loading of the plane.
I will check that, thanks
Wow XB-70's Cd is ridiculous... I have seen other drawings with much steeper reductions of Cd as speed increases, it depends on the design and I cannot make statements about how it behaves in the Su-57. Keep in mind the trimming options they have with the TVC and LEVCONS to reduce drag in supersonic flight too, everything in the design has been conditioned by this flight regime. Of course, I am aware that drag increases non linearly with speed, but the fact that F-22 can cruise so fast with an engine size and cross sectional area very close to Su-57 despite allegedly not being as aerodynamic as the YF-23 supports that a cruising speed in that ballpark for the Su-57 is perfectly possible, besides being a logical design goal both for the plane and for the second stage engine, designed as said above immediately after the 117 was developed and hence still up to date. As argued other evidence suggest that the installed thrust of the 30 is equal or bigger than F119, maybe the radar blockers being the only negative issue I can think of.
Why twice the dynamic thrust of izd. 117? I simply assume it will be equal or better than F119's, that has as said 25-35% more uninstalled mil thrust, mainly due to lower BPR. A change in BPR between izd. 117 and 30 would get most of the work done, I assume.
Re. the different thrust profiles w/ and w/o AB, I am aware the comparison is decidedly rough but still applicable. Do you have some data to help refining it?
BTW, it seems today is a busy day showing the Su-57 :D
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https://twitter.com/Ozkok_A/status/1166287074540118018
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By: RadDisconnect - 27th August 2019 at 14:44 Permalink - Edited 27th August 2019 at 18:21
One of the stated goals of izd.30 is lower maintenance and operating cost. Especially since izd.117 is considered not economical to run. More power is not the only goal of izd.30, higher MTBO and better operating economy are major goals.
Here is diagram of F-22 fuel tanks, you can see the two rear tanks by the engine bays.
https://www.nap.edu/books/0309053331/gifmid/62.gif
The much steeper reduction in drag coefficient when Mach increases is for only individual components like the wing or a generic object. When you have a whole aircraft the total supersonic parasite drag buildup will include things like shockwave interference and total area rule and volume distribution. So even with a dedicated interceptor like F-106 where drag reduction was emphasized over pretty much everything else you don't see that steep kind of drag coefficient reduction of just a component.
XB-70 drag coefficient is low because wing is huge (drag force is drag coefficient times dynamic pressure times wing area), and also that aircraft is optimized to the extreme for supersonic flight. Also small wings is why F-104 drag coefficient is so high even though actual drag is actually very low.
~35% increase in thrust will get you from Mach 1.3 to Mach 1.6-1.7 at best. For example YF-22 supercruise speed is Mach 1.43 with YF119 and Mach 1.58 with YF120 which is 20% more powerful because of the YF119 didn't have the bigger fan for increase mass flow of production F119, while YF120 did.
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By: paralay - 27th August 2019 at 15:50 Permalink
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