tavarish palkovnik

May I ask for a source of SD-10 (PL-12) motor specifications used in DCS, 57,6kg and 11,6kg, 6 and 4 seconds, 242/236s By the way, РДТТ Р-300Э, I never found any reliable document that motor had or has this designation

Forgot to say...this method is appliacable only for velocities >0,8M !

...

…Ref.area is 8,8m2

Only for 5V21 but that should fits to 5V28 with no doubts I guess you are Russian speaking so you will not have problems with these graphs. Only I need to check what is reference area and I will share it as soon as got it. Something with wings because in that time wings were usually base

Now when have some Cx f(M) why not to make some shot to see how far it could fly. There is one nice iteration method, rough but nice, not very suitable for long active time and altitudes over 10km but I will turn a blind eye this time So 12km, horizontal flight, same velocity of fighter and target (325m/s), I want of rocket to have velocity of 600m/s when come to target, density of air is 0,3118, average chamber pressure let's say 70 bars, let's say gases will expand fully to ambient pressure of 0,02Mpa, average calculating impulse 240s, average drag coefficient 0,65 and iteration is that rocket will fly all together 37480 m and that distance will reach in 45 seconds. It means 52km is fireing distance And now method with integration... Or Mach number if more suitable And finally distance Iteration is very close to integration, or opposite, 38900m

Based on my calculations for this missile and if nozzle exit is 125mm, average difference between active and passive is 8,5% Here is two samples, one rocket with widely opened nozzle (5V55 of S-300) and one with significant difference between body cross section and nozzle exit cross section (5V27 of S-125 ; 170mm vs 381mm) While in first case body cross section is refferent area, in second it is wings (0,96m2) so roughly pick in passive would be 0,67 if cross section (dia 381mm) is refference

Shortly to explain these graphs, because I don’t believe that slight differences in form of rocket’s rear and generally slight differences in drag coefficients can change velocity in active time (motor ON) much. This program of mine is for ballistic flight, it’s true, but that shouldn’t change things much. I will explain later. Program is for single thrust models so I had to improvise a bit, four slides is one shot, two inputs and two outputs respectively. So first slide is start, 12km, 1,1M and ballistic shot with 10deg. Fourth is end and only velocity is what is subject to watch. So final velocity is 1207m/s or 4,09M. Program is based on law of Cx58, I don’t know how much you are familiar with it. Coefficients i58 active and passive are what should be relative to Cx58. So if I assume i58 as 1,3 and 1,45 and if and it is Cx58 at for example 1,1M 0,628 that means Cx (or Cd who likes more) is 0,8164 in active and 0,9106 in passive respectively (at 1,1M) Next 4 slides are simulation what if drag in active would be exactly same as in passive, no assist of flame whatsoever, base pressure drag is maximal whatever is exit diameter of nozzle. And such final velocity is 1195m/s or 4,05M. Difference of just 0,04M, just 1% ! Last 4 slides is next simulation, what if drag force would be somehow doubled, i58 2,6 instead of 1,3. Final velocity is 1103m/s or 3,74M or difference of 0,35M or decrease of 8,6% However, i58 2,6 means that rocket fly continuously overloaded with angle of attack roughly 10deg. Example, Cx58 at 4M is 0,302 and let’s assume Cy (lift coefficient) at 4M is 0,25. Cx=1,3*0,302=0,393 (zero AoA) Cx ind=10^2/57,3*0,25=0,436 Cx total=0,829 or roughly double more then unloaded Cx. Forgot to say, reference area is always cross section of rocket. So, all together, Cx in active does not influence a lot, it is insignificant in the matter of fact. Weight of fuel and impulse of fuel primarily and thrust force distribution in time secondary are the ones that change things significantly !

...........................

Comparing to photograph, motor indeed could be around 2080mm what makes this very interesting. This is situation with Mk-58 of AIM-7F, two grains burning at the beginning together and then only sustaining one. The one is 23,6kg, other 37,7kg having different burning rates. Roughly speaking in first 4,5 seconds 45 kilos of fuel burn and rest remaining 11 seconds. Not for my taste but it is as it is. If similar principle will be applied to motor of PL-12… It is about 69 kilograms of fuel in total, exactly what DCS use if I’m not wrong. But if this configuration should burn for 6 seconds using 57,6kg of fuel and remaining 11,6kg for next 4 seconds then it should looks something like this… And it looks horrible, unreal. I don’t know source of this distribution ratio, I don’t know if this perhaps is result of “squaring” thrust curves or something else but simply it doesn’t looks natural. And what influence more, exit diameter of nozzle or perhaps thrust distribution in time. Usually area of exit is around 10 times bigger then cross section area of throat so it can gives some clues about pressure in chamber and respectively burning rates

Good day to all ! Here is one rear view at operating PL-12 missile if it will be helpful Is there anyone who could translate this, is it written anything about missile this motor is related for? Motors and burning processes are interest of mine and I saw that in DCS this PL-12 or SD-10 has very awkward buster-sustain distribution and ratio. If info I got is not wrong, in buster stage of 6s 57,6kg of fuel is burned, and in sustained stage 11,6kg for 4 seconds. Interesting indeed. What exactly is length and weight of this rocket, internet gives values in contradiction, 3934mm 3850mm, 199kg, 180kg etc etc Actually what I’m looking for is origin of this motor I believe it must be somehow related with R-77 in some stages of development and using its motor for other applications (surface to air variant) and these Chinese missiles which have roots from R-77

Great, thanks a lot

...

...

...

Is anything new appeared in the meantime? Is there any new document published somewhere? About motor, ballistic, anything

...

Great sentence…”at what pressure” Pressure is the one and main only one making significant differences. In my language, pressure is the one fu..ing chickens in the yard

That’s true, impulse giving real thrust (расчетный импульс) should be calculated from specific impulse (удельный импульс) taking in consideration pressure values. Specific is like said usually given in ratio 40:1 and for example motor burning at 10km in buster phase is let’s say in ratio 100:0,265 (bars) To correct myself, coefficient K in upper formula is more related to the looses in burning process, some of fuel mass will not contribute making thrust force and with K it is included. To return on pressure, which value will be used for “pa” … it depends of how nozzle is executed and on expansion of gases. If gases will expand all to the atmospheric pressure (pressure at exit of nozzle is equal to atmospheric pressure) maximal thrust will be at disposal. That’s why motors of space rockets in upper stages have nozzles as big as bells on churches so that gas can expand to the level of low pressure as it is up there. Unfortunately for constructors of A-A missiles, they must make compromise with nozzles because those can be used at low level and high level flights. Conclusion…thrust is variable and that is a fact. Just as second fact and that is, drag coefficient in turbulent air flow, what is mostly case, for sure will be increasing with altitude (viscosity, Reynold’s number etc) Motor gives, drag takes!

...

...

...

Just from the curiosity and my wish to see it, who will be kind to show me thrust diagram of R-27ER momentarily used in DSC. For example at 10km altitude.

...

...