I can already tell just by glancing at that report that it will most likely be declined. It has similar issues to reports 1 and 3 in the given examples. Gaijin has rather strict, but also somewhat understandable guidelines/restrictions on how sourcing must be done. Failure to abide by these will just have the report ignored…
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Yeah. I looked through the sources and it wasn’t telling much. After that I was thinking in doing some tests on ideal conditions(10000m altitude, headon, cooperative target…)myself using the R-77 and comparing if it can achieve the ranges rosoboronexport have shown on their video and catalog on the RVV-AE, which has the same numbers as the R-77 it seems like.
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Reports focusing on only one aspect (drag) will just be shut down as you would not know if the missile’s thrust is higher than normal to compensate for the increased drag. Hence why reports focusing on the time-to-target or range is much better overall as they look at the complete picture.
Interestingly, R-77-1 has its unique drag modeling modeled in-game. At high altitudes the R-77-1 is the best missile out of anything else currently in-game, but at low altitudes it is in the middle of the pack or even worse than the AIM-120A, so that implies the developers do have some range charts of the R-77-1 at the very least and correctly modeled it. The way grid fins work is that they do suffer extreme drag in transonic areas with much better supersonic drag. At high altitudes the grid fins would spend less time in the transonic areas compared to low altitude, so compared to regular missiles the R-77/R-77-1 should enjoy better high altitude performance while taking a hit to lower altitude performance. This seems to be modeled in-game for R-77-1 but the differences are not drastic enough for the R-77.
It could be possible that the R-77 is underperforming at higher altitudes, while overperforming at lower altitudes but the majority of gameplay (mid and late stages) are at lower altitudes. But it is complete speculation on my part.
Anyway, the only range charts I have seen on the R-77 comes from an Italian website documenting on multiple missiles and it is this one:
Spoiler
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Like, let’s say, a graph showing the speed as a function of time?
We could try to mathematically aproach the drag coefficient on the R-77, instead of using the datamined value. Here a sensor replay:
Analysing the first missile launched, I made a graph in which i registered each speed on mach numbers per second of flight(And I registered only the speed after the booster fades, but including it also can be useful):
speed x time graph
I didn’t had much time to develop the hypothesis, but the desacceleration the missile suffers forms a exponential curve, varying less as more time pass on, when it should look more like a logarithmic curve, on accord with what has been said in this topic:
Logarithmic and Exponential curves
Comparing with the graph of the speed in function of the time, the exponential curve is identical to the speed x time graph, but it shouldn’t look like that.
As we see in the graph, the missile suffers more desacceleration in high mach numbers rather than in low mach numbers, close to the transonic region. Ex: the missile stays only 10 seconds between mach 3.8 and mach 2.8 but it stays 20 seconds between mach 2 and mach 1.2 - and the duration in which the missile stays in this speed interval increases greatly if we go all way to mach 1, where it takes more 12 seconds to go from mach 1.24 to mach 1 -, even if it is in denser air, close to the bomber which is 4000m of altitude.
The graph is built around the speed as a function of time, so we can also see that there is a kind of limit forming, meaning that the variation aproaches zero in the transonic region, when it should be like the logarithmic curve, where the limit form at high, supersonic speeds, then the speed rapidly degrades when it falls in the transonic region.
If we were to consider a fix like using the logarithmic curve and its intersection as pictured in my comparison of a logarithmic curve and a exponential curve as a guide, the missile would fall under mach 3 only after 45 seconds, which would mean it would have plenty of energy to hit anything at 45Km if we consider a medium speed of 1000m/s; if we integrate correctly the speed it should have, easily it would be able to easily hit things past 55Km or 60Km, making some guestmations.
What you think of this?
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Honestly quite interesting. And yeah, I’ve understood that the grid fins would suffer the most in trans-sonic areas. I didn’t know the R-77-1 was in the files, but it seemingly is.
- War-Thunder-Datamine/aces.vromfs.bin_u/gamedata/weapons/rocketguns/su_r_77.blkx at master · gszabi99/War-Thunder-Datamine · GitHub
- War-Thunder-Datamine/aces.vromfs.bin_u/gamedata/weapons/rocketguns/su_r_77_1.blkx at master · gszabi99/War-Thunder-Datamine · GitHub
Can you tell me where the characteristics of the fins are? Or are they somewhere else? These files are a bit hard to read for me personally, since you seem knowledgeable on the subject.
But outside of that, your hypothesis is quite interesting however. The missile under-performing at higher altitudes, while over-performing at low altitudes is a claim that I feel has some merit to it. But testing would need to be done to truly come to a conclusion on the matter.
And I agree with what you say regarding reports, that is a very good point and it’s something to keep in mind.
Either way, thank you a lot for the insightful information!
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Gszabi/Johnwick9 maintain a spreadsheet called Missile Guidance data and you can find those characteristics here:
Keep in mind I am not claiming either way that the missile is overperforming or underperforming. I don’t have any R-77 data, it could be underperforming in every range aspect, I was just giving a hypothetical to demonstrate lattice fin modeling.
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You do have a point. But we will have to do some more experimenting honestly.
I found a relatively interesting/in-depth declassified source from NATO: https://apps.dtic.mil/sti/pdfs/ADA509444.pdf
Which actually says that the fins are folded until launch? Which doesn’t seem to be the case in-game… Though, I am not sure how it actually is, the document does mention it though.
The given source confirms mostly what we know so far of course. It goes into some pretty good detail about the performance effects of the grid fins, but if I’m being honest a lot of the math and physics shown does fly over my head a bit. A summary from what I understand is that, as this image states; they do have greater drag than normal fins.
I see. That’s fair enough. I guess we will just have to test it out and find it out ourselves. But as @NoobHue80073 outlined in his post, the missile shouldn’t de-accelerate the way it does currently. The source I linked does back that up, and so does most of the discussion regarding it. So I guess we have that at least, well, we knew it to begin with, but still.
IIRC the folding fin version was a prototype for internal carriage. Photos always show the missile being carried with fins deployed:
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The equation for drag is:
F_D = \frac{1}{2} C_D \rho v^2 A
As it scales with velocity squared (i.e. drag scales exponentially with speed) you would always expect an element of exponential speed loss regardless of drag coefficient. Obviously the way drag coefficient changes with speed for grid fins complicates the matter, but I very much doubt a simple logarithmic curve for velocity Vs time would be correct.
There’s a photo circulating the Warthunder discord servers. It seems that this may be what Gaijin used to model the R-77? I’m not exactly sure. I only have the picture, not the cover. It seems to claim that the R-77 has the same range as that of R-27R.
We know the R-27Rs range according to the MiG-29 manual.
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I have been reading into the subject regarding the drag characteristics of grid fins for some time now, and I have made some findings; which I feel have been ignored a bit.
This honestly does make me question if the issue people have been discussing about is as prevalent as it has been made out to be. It has been discussed a lot that the issue lies in with excessive drag, but based on my findings on multiple sources; I have come to conclude that grid fins have a lot more drag in general than normal planar fins.
Multiple studies regarding the subject confirm the matter as being such. This particular study I am looking at right now, made by the Air Force Institute of Technology (https://scholar.afit.edu/cgi/viewcontent.cgi?article=4918&context=etd) regarding the subject matter puts it rather straight:
Figure 11: Flow around Missile with Mach Number Greater than 1 (13)
Figure 12: Axial Force Coefficient: Planar vs. Grid Fin (14)
But the TLDR from what I’ve understood is that the drag in almost all condition is notably greater than in normal planar fins. Multiple studies seem to conclude that as being the case. An averaging out of all the various drag values comes to around 39% increase compared to planar fins. Which is what I have seen people propose Gaijin did with the fins.
The trade off for this extra drag is the extra maneuverability, and the other advantages grid fins provide (smaller motors required, and also the possibility of folding them which feels like it was a key thing with the missile…)
Conclusion of Marco Debiasi's Forces and Moments Generated by Swept-Forward Grid Fins and Planar Fins
NASA: Analysis of Grid Fins for Launch Abort Vehicle Using a Cartesian Euler Solver
Legend:
M∞ = free-stream mach number
CA = axial force in missile axis
CN = normal force in missile axis frame
Cm = pitching moment in missile axis frame (with respect to c.g.)
The general consensus/summary from what I’ve gathered now is the following:
Drag Table
- Below 0.8 mach: 20-30 percent increase compared to planar fins, caused by wetted surface area
- 0.8 to 1.2 mach range: 80-100 percent increase in drag compared to planar fins. This is the transonic region, which is a known weakness of grid fin design. The excess drag is caused by flow choking, shockwave formation inside lattice and severe wave drag
- 1.2 to 2.0 mach: 30-50 percent more drag compared to planar fins. The shockwaves realign, but the drag is still greater than that of planar fins.
- 2.0 to 3.0 mach: 30-40 percent greater drag than planar fins. The inefficiency of gridded fins still persists, but is less noticeable than before.
- 3.0 mach and above: 0-10 percent increased drag compared to planar fins. At these speeds the drag becomes around on-par with regular planar fins.
And as such, I honestly raise into question if the “incorrect” modeling of the grid fins would have that much effect to begin with? My findings personally seem to indicate that they do suffer a lot more drag than regular planar fins to begin with, which makes sense. Obviously, if it was modeled to always have the transonic drag, then it would be problematic. But the issue is that the fins suffer from more drag practically in every possible flight profile.
But what do you all think? Is this something we have overlooked?
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iirc, grid fins only have improved drag characteristics over planar fins at “high supersonic” speeds, or at high AOA’s. This arguments been had over and over for some 2 years with many papers cited and compairisons made, but the grid fin crowd continues to refuse to believe that they arent the greatest thing to have ever happened to missiles.
Theres also the question of why gaijin would bother modelling a highly complex non-linear drag profile for fins that are only ever seen on 2 AAM’s (R-77/-1) instead of spending their time and ressources on other tasks.
End of the day, unless ppl have actual test data, or primary source data on what the R-77 should be able to acheive, every complaint about its range amounts to just being assumptions made based on peoples feelings that have been canonized by group conciousness. ie: if some ppl repeat something enough, others will begin to believe its true without actually questionning it.
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Based on my own research, in the drag table section; even that is not true. The range disadvantage is prevelent at all mach speeds; but at mach 3.0 and above the disadvantage is minimal. (Around 0-10 percent increase in drag compared to planar fins…) Essentially, at these speeds, the drag becomes only on-par/equivalent to planar fins.
The advantage of the grid fin design doesn’t lie in the range, but in the maneuverability advantage it provides especially at higher mach numbers and ranges. Most of the papers I read seem to come to that conclusion regarding them. There is also the interesting side of swept/slanted grid fins which the NASA paper touches and focuses on quite a bit.
From the understanding I’ve reached, there’s a reason the grid fin design isn’t really used outside of Russia; because it has that disadvantage in range. However, a swept/slanted grid fin design seemingly does mitigate some of these issues. I think it’s around a 30% performance increase in general? The swept and slanted grid fin design in particular helps with the transonic issue.
Of course, this isn’t relevant to the R-77 as it doesn’t use slanted grid fins; but it’s still somewhat interesting nonetheless.
And honestly, yeah. That is the unfortunate truth. But as I outlined in my post – I think people have hyperfixated on this aspect a bit too much. From my current understanding, I think the performance increase in the missile’s performance would be minimal, even if it would be implemented. But do not quote me on that!
I need to do some testing myself to figure out just how the missile is modeled currently in-game. Because I still am not entirely sure just how Gaijin modeled it. The averaged out drag theory does seem to be the most prominent, but I can’t be sure yet.
But I think ultimately what speaks the most of this is the fact that Russia never really adopted the initial R-77 in the first place. Instead, operating the upgraded R-77-1 which we hopefully get soon in the game. But that missile obviously still suffers from the same issues as the R-77 due to it’s unswept/unslanted grid fin design. It’s no wonder in my opinion that Russia is trying to phase the R-77-1 out in favor of the R-77M which has traditional planar fins, because the range/drag performance in grid fins is just that much worse. As said, the advantage lies in maneuverability; but we all know that in modern air combat range is what matters most.
Ultimately, I have to do some testing myself before I can come to a definite conclusion regarding the subject myself. But I do not think my hypothesis/understanding regarding how grid fins really do hamper range quite drastically is unfounded, as practically every source I’ve read on the subject seems to support this claim.
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The only ultimate performance test I can think of is the bomber headon on high altitude:
Range
Rosoboronexport tells us the max launch range the RVV-AE has against bombers is 80Km, which is the same in this chart.
That chart states a max launch range of 100km, not 80km. Also iirc that chart isnt official at all.
Also of note, the highest launch conditions you might see in-game are in the ballpark of 10km alt, likely against targets below you as well. The engagement envelope according to that chart for such altitudes in head-on shots is like, 40km.
All of these studies baselessly assume the grid fins on the R-77 are quite thick compared to the real life dimensional data and use wrong taper ratios etc.
The data for the R-77 in there is incorrect as mentioned above comparisons for generic grid fin are valid but cannot be assumed that the R-77 matches the data. They could have also used a planar fin that was more indicative of what we see on real air to air missiles instead of the one they used.
Spoiler
Even this 2020 thesis study is incorrect;
Spoiler
Rosoboronexport states 80Km
I know, what Im saying is the chart doesnt match rosoboronexport numbers, it exceeds them by 25%, and that even if the chart was accurate, which is a massive if, the launch ranges according to it in-game would be at most in the ballpark of 40km.