okopanja Posted July 11 Posted July 11 11 minutes ago, tavarish palkovnik said: I kind of disagree, manual calculations of individual components of total drag and making sum of them can be quite precise. Of course wind tunnels or live firing of telemetric missiles give real and true values, but if you read old documents (when manual work was only method available) differences are not so big, actually in most cases calculations could be accepted as quite accurate. CFD is nice piece of technology, but CFD is nothing more than program where all theoretical principles are combined in one helpful tool. Nose pressure, base pressure, wings pressure, body friction and wings friction and there it is. Some of components like base pressure are with including interface of other elements, wings and boattail configuration and shape, and all that is part of calculations. Actually I think that main reason why missile with grid fins has something higher drag compared to missile with classical fins is not so much because of pressure on fins but because of higher base pressure Observer 4 long fins directly on the path of the air in front of grids... These change the behavior and likely have multiple effects, given the fact that this "bulge" was kept across 3 variants.
MA_VMF Posted July 11 Posted July 11 (edited) 20 часов назад, tavarish palkovnik сказал: I kind of disagree, manual calculations of individual components of total drag and making sum of them can be quite precise. Of course wind tunnels or live firing of telemetric missiles give real and true values, but if you read old documents (when manual work was only method available) differences are not so big, actually in most cases calculations could be accepted as quite accurate. CFD is nice piece of technology, but CFD is nothing more than program where all theoretical principles are combined in one helpful tool. Nose pressure, base pressure, wings pressure, body friction and wings friction and there it is. Some of components like base pressure are with including interface of other elements, wings and boattail configuration and shape, and all that is part of calculations. Actually I think that main reason why missile with grid fins has something higher drag compared to missile with classical fins is not so much because of pressure on fins but because of higher base pressure nullnull Спойлер Спойлер null Спойлер null Спойлер null Спойлер Спойлер null null Спойлер null Edited July 12 by MA_VMF 1
MA_VMF Posted July 11 Posted July 11 (edited) Условия теже 2.5М АоА=5 Су=0.62 Сх=0.219 Сya=0.62*cos(5)-0.219*sin(5)=0.5985 Cxa=0.219*cos(5)+0.62*sin(5)=0.272 nullK=2.2 Спойлер null Спойлер Edited July 11 by MA_VMF
MA_VMF Posted July 12 Posted July 12 (edited) Спойлер null М=1.1 АоА=0 Спойлер null null М=1.2 Спойлер null М=1.5 Edited July 12 by MA_VMF
nighthawk2174 Posted July 12 Posted July 12 A few questions regarding the R77 - What are the dimentions of the lattice fins and chord profile? -How much is known about the motor? -How much is known about the radar seeker?
tavarish palkovnik Posted July 12 Posted July 12 Motor is clear more or less Now I can just wait @MA_VMF to finish Cx and Cy functions to make пуск with more accurate data. Hope it will be done in this lifetime Until waiting, one bold prediction for rocket’s passive Cx at 1,1M AoA=0 … 1,4 with body cross section as reference area. Cy something like 0,6 1/deg
nighthawk2174 Posted July 12 Posted July 12 1 hour ago, tavarish palkovnik said: Motor is clear more or less Now I can just wait @MA_VMF to finish Cx and Cy functions to make пуск with more accurate data. Hope it will be done in this lifetime Until waiting, one bold prediction for rocket’s passive Cx at 1,1M AoA=0 … 1,4 with body cross section as reference area. Cy something like 0,6 1/deg Concerning the motor shape is there a diagram that exists your work is matched too? Do we know the propellant type as well?
tavarish palkovnik Posted July 12 Posted July 12 20 minutes ago, nighthawk2174 said: Concerning the motor shape is there a diagram that exists your work is matched too? If I say this is with 95-98% precision reconstructed motor, would it be enough? This is after all, just one more motor layout in line which I shared here, beyond others for which you will hardly find something on internet. But everything can be found, one way or other
tavarish palkovnik Posted July 14 Posted July 14 (edited) 14 hours ago, MA_VMF said: null null Sea level ; M=1,5 ; AoA=0 perhaps ? Bold prediction if it is sea level and 1,5M and of course if you extracted numbers -> Cx something about 1,25-1,3 Cn 3,7 (AoA=10deg) Cn 11 (AoA=30deg) ... or it is M=1,1 more likely ... 1,75 ; 4,4 ; 14,8 respectively Edited July 14 by tavarish palkovnik
MA_VMF Posted July 14 Posted July 14 4 часа назад, tavarish palkovnik сказал: Sea level ; M=1,5 ; AoA=0 perhaps ? Bold prediction if it is sea level and 1,5M and of course if you extracted numbers -> Cx something about 1,25-1,3 Cn 3,7 (AoA=10deg) Cn 11 (AoA=30deg) ... or it is M=1,1 more likely ... 1,75 ; 4,4 ; 14,8 respectively SL AoA=0 M=0.8
tavarish palkovnik Posted July 14 Posted July 14 25 minutes ago, MA_VMF said: SL AoA=0 M=0.8 Mach number 0,8 will not help us a lot to figure out what could be final score. Of course it would be great if you can make as much situations as possible but I think the most interesting range, and range where I expect really significant drag, is between 1,1 and 1,8M. I hope you will manage to finish this interesting piece of work, and I'm expecting curve of drag coefficients in form a little bit different then it usually looks like
nighthawk2174 Posted July 14 Posted July 14 On 7/12/2025 at 1:15 PM, tavarish palkovnik said: If I say this is with 95-98% precision reconstructed motor, would it be enough? This is after all, just one more motor layout in line which I shared here, beyond others for which you will hardly find something on internet. But everything can be found, one way or other That'd be good enough considering the limited nature of information.
tavarish palkovnik Posted July 15 Posted July 15 For comparison when numbers from CFD arrive...Cx58 added just for pictorial representation of differences
tavarish palkovnik Posted July 15 Posted July 15 Not sure which kind of results for comparison will be the most suitable so few more, situation 1,5M and 10km
tavarish palkovnik Posted July 17 Posted July 17 It’s kind of hard to find some texts with given numbers of drag coefficients for full assembly, for rocket with grid fins instead of for fins only. This is from one of such rare paperworks. Configuration is some sticklike wingless rocket with not very aerodynamic nose and they made and gave numbers for three different diameters, 500, 700 and 900mm. Table shows numbers for 500mm configuration where Cx_rocket are drag coefficients for rocket without fins and Cx_full coefficients for rocket with included grid fins. Interestingly, and not surprisingly to me actually, added fins increase drag coefficients making them as much as twice higher in average. In finless configuration only pressure on nose, pressure on base and body friction participate. With adding fins, two more components appear, pressure on fins and fins friction. While second should not be something significant, first could be. But I think the biggest difference could be base pressure. The lowest base pressure will be of course always in finless configuration. Classic fins increase base pressure of course and I think grid fins increase it significantly
HFXLegion Posted Saturday at 04:43 PM Posted Saturday at 04:43 PM Does DCS have combined guidance for SAMs (Radio Command + SAR)? If not, is it planned? I also can't find any possible values for the `Head_Type` missile configuration anywhere
MA_VMF Posted Sunday at 09:31 AM Posted Sunday at 09:31 AM (edited) Edited Sunday at 09:31 AM by MA_VMF 1
tavarish palkovnik Posted Sunday at 03:15 PM Posted Sunday at 03:15 PM 5 hours ago, MA_VMF said: New tricks, single image for two different situations ? Bottom is sea level seems like, and top side something higher altitude, and looks like some higher velocity then 0,8 mach number. And I'm very curious to see how this ''blue'' part (vacuuming) will develope with velocities
MA_VMF Posted Sunday at 05:51 PM Posted Sunday at 05:51 PM 2 часа назад, tavarish palkovnik сказал: New tricks, single image for two different situations ? Bottom is sea level seems like, and top side something higher altitude, and looks like some higher velocity then 0,8 mach number. And I'm very curious to see how this ''blue'' part (vacuuming) will develope with velocities нет, это просто изображение на двух плоскостях 1 расчетного случая
tavarish palkovnik Posted Sunday at 06:15 PM Posted Sunday at 06:15 PM @MA_VMF Don't take me wrong but it would be fair to write few words with applied image, otherwise images become -> 2
tavarish palkovnik Posted Monday at 11:35 AM Posted Monday at 11:35 AM I was questioning why and how comes there is no yet on internet drag function for R-77. Really it is not easy to calculate such configuration, actually I'm giving up of it. Simply I don't have enough literature to make some reasonable, at least approximative calculation. All other rockets with normal fins can be quite easily calculated and results were not so bad, actually where had valid data to compare, not bad at all. There are several paper works but mostly they have focus on drag of individual fin, and I'm interested in full assembly. I was mentioning base pressure, one of the easiest parts of total drag calculation, but here with grid fins I just stuck and don't know how to proceed. And like said already, I'm expecting this part together with pressure on fins to be significantly higher then what is case with classic fins or wings whatever is in aft zone Few such aft section surfaces, Phoenix, Sidewinder and Sparrow For all these configurations base pressure can be easily calculated, and this ''c'' number (ratio between wing thickness and aerodynamic chord) is for these samples approximately 0,036 ; 0,046 and 0,09. What grid fins make on body base I have no idea ...
tavarish palkovnik Posted yesterday at 05:27 PM Posted yesterday at 05:27 PM When mentioned Sparrow, I don’t know if already had conversations about this drag function attributed to Sparrow Don’t like this “all altitudes” but never mind, differences are not so dramatic. But this function without reference area is not much useful… In any case, it should be area of two fins making peak as 0,84 counting with body cross section area
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