Ракеты в DCS

[Chizh]

17 часов назад, Gahab141 сказал:

Разве у 31БН по 2 пилона на проскость? Или моделька БМовская?

Да, модель БМ, а в нутри БН.

[musolo]

1 hour ago, Chizh said:

Да, модель БМ, а в нутри БН.

кабина вроде тоже от  БМ что радует)

F-14A бот имеет только одну ракету оказывается. Aim-54C. Первоначальной Aim-54A у него нет, что странно.

А почему русский парк ботов застыл в 1992 году? Ботов никто не запрещает ведь делать по закону? Хоть Су-27СМ, хоть Су-30МК, хоть Су-35 и Су-35С? Никаких легальных препон нет же, так ведь?   

Edited January 14, 2022 by musolo

[tavarish palkovnik]

11 hours ago, BlackPixxel said:

Here is the same with the R-33ED in DCS, launched at 10 km from 500 m/s:

After 60 s it has travelled about 45 km and is down to a speed of 434 m/s. The top speed it reaches is 1065 m/s. Quite a bit weaker than your estimation.

 

@BlackPixxel You are one of the rare asking questions and that is good to see, to have ones having doubts and not with taking for granted

Maybe is not right of me to comment this what you extracted, but I will anyway, with hoping of no hard feelings from the authors. But first and it will be related to this as well, you know, external ballistic and by that I mean on various coefficients of drag and lifting forces, influence however don't be surprised if I say, with keeping those in realistic levels, range of influence shouldn't be more then let's say 5-10% (non-maneuvering flight)

Internal ballistic is the one making thinks different significantly. Here you mentioned many times active time of R-27ER, believe me that is it 8 or 9 or 9,5 seconds, and with keeping basic rules, velocity and range functions shouldn’t drastically vary. You know 125kg of fuel can burn in 8 seconds and can burn in 12 seconds, it doesn't mean that in second case you will have extra 4 seconds of thrust, you will actually but take in account thrust envelope of slow and fast burning fuel because only mass of gases make thrust. I'm sure you know all that but just to be clear.

 

To return on this what you extracted, here it is simulated what should be input to get such v f(t) and D f(t)

 

 

  

 

 

Looks close isn't it. And like said with keeping Cx, Cx ind and Cy in realistic levels and with constants which are as they are (density, gravity etc) only with internal ballistic we can have such drastically different outputs.

Are you able to extract thrust to time function of this case? Is it possible or is it ''hidden'' in program?

I'm giving this could be input for presented output...

 

 

Sorry if I will disappoint someone, but this can't be case. Fuel grain in form as it is simply doesn't burn that way. We can discuss is it Isp 2300 or 2600, is it burning time in function of pressure with exponent 0,25 or 0,3 or 0,4 but some elementary rules of internal ballistic and solid rocket fuels can not be neglected

[BlackPixxel]

2 hours ago, tavarish palkovnik said:

Are you able to extract thrust to time function of this case? Is it possible or is it ''hidden'' in program?

Here is the motor configuration of the R-33 in DCS, it is close to what you read from the graphs:

Boost: 4 s, 37280 N, 15.4 kg/s

Sustain: 16 s, 13950 N, 5.9 kg/s

So it has 156 kg of rocket fuel.

In DCS the missile weighs 520 kg.

 

What do you mean with fuel doesn't burn that way? That the fuel burn is constant in each stage (simplification of the game) or something else?

 

Regarding the R-27E motor: Yes, the end result will not change, but it is just about getting a realistic value for the missile that is in line with the official data, and not taking some third party data and saying that the real manual is wrong.

What does affect the R-27E in DCS is that because of using the third party data, the boost/sustain ratio got weakened alot, so now the missile lost its initial acceleration, meaning that at closer ranges it now takes longer for it to hit. Meanwhile the manual gives a much stronger value for the boost, and also the PDF about the proposal of using the R-27 as a surface to air missile shows a much larger boost/sustain ratio than we have right now in DCS.

Edited January 14, 2022 by BlackPixxel

[Chizh]

4 часа назад, musolo сказал:

А почему русский парк ботов застыл в 1992 году? Ботов никто не запрещает ведь делать по закону? Хоть Су-27СМ, хоть Су-30МК, хоть Су-35 и Су-35С? Никаких легальных препон нет же, так ведь?  

Сразу после F-22, F-35, Rafale и Typhoon.

Но пока планов нет. В любом случае это не тема данной ветки.

[tavarish palkovnik]

23 hours ago, BlackPixxel said:

Here is the motor configuration of the R-33 in DCS, it is close to what you read from the graphs:

Boost: 4 s, 37280 N, 15.4 kg/s

Sustain: 16 s, 13950 N, 5.9 kg/s

So it has 156 kg of rocket fuel.

In DCS the missile weighs 520 kg.

 

What do you mean with fuel doesn't burn that way? That the fuel burn is constant in each stage (simplification of the game) or something else?

 

Regarding the R-27E motor: Yes, the end result will not change, but it is just about getting a realistic value for the missile that is in line with the official data, and not taking some third party data and saying that the real manual is wrong.

What does affect the R-27E in DCS is that because of using the third party data, the boost/sustain ratio got weakened alot, so now the missile lost its initial acceleration, meaning that at closer ranges it now takes longer for it to hit. Meanwhile the manual gives a much stronger value for the boost, and also the PDF about the proposal of using the R-27 as a surface to air missile shows a much larger boost/sustain ratio than we have right now in DCS.

 

 

That is not manual of Mig-29, that is just text on the Internet wrote by someone. If you mean by third source at the v f(t) diagram from MGTU, that source is at least from veeeery respectable institution signed by colonel, assistant professor, candidate of technical sciences...by someone in position of ТО и ИЭ. And beside that, the most reliable source is video showing R-27ER in flight, and for sure that one was not started at +60 degC.

The most recently I was doing something about S-24B and took some data from Internet, everywhere is that weight of the fuel is 72 kg and after one day of struggling what the F I'm doing wrong not having expected outputs, I realized that it can be only 42 kilograms. Internet is great and in same time full of nonsense.

R-33...that is with so many issues that you are complaining with reason. This rocket here is given with fuel weight almost equal to what is in 5V27 of Neva system, total impulse is just a bit over to what 5V27 has, maximal thrust force is just a bit over to what H-25ML gives, distribution and transition between buster and sustain is unreal, second's impulse is without corrections due to expected to be chamber pressure, seams that atmosphere pressure at altitude is not included etc etc. My by opinion, R-33 here is with many faults.

Just as sample three well known rockets in caliber 380mm scaled and side by side 

 

 

    

[tavarish palkovnik]

 

 

Отличный пример сжигания канально-щелевого заряда с двухрежимной тяги. 
Посмотрите на длину пламени и посчитайте секунды, это диаграмма тяги.

[Chizh]

1 час назад, Gahab141 сказал:

Еврофайтер уже на горизонте. Так может хоть одного полусовременного бота добавим красным? Хоть тот же 31БМ, раз уж моделька уже есть

Это будет иметь смысл если в планах появится Р-37. 

[okopanja]

@Chizhgiven the fact, that more and more sources and calculations are done on the subject which contradict the DCS burn time of R-27ER, would it be possible to present your own calculation and sources, given the great work you did for AIM-120?

IMHO: this would be a way better way to prove/dispute the currently implemented DCS values, other than simply disputing the matter.

P.S. apologies for using English, but I prefer not to write using google translate.

[Chizh]

2 часа назад, okopanja сказал:

@Chizhgiven the fact, that more and more sources and calculations are done on the subject which contradict the DCS burn time of R-27ER, would it be possible to present your own calculation and sources, given the great work you did for AIM-120?

IMHO: this would be a way better way to prove/dispute the currently implemented DCS values, other than simply disputing the matter.

P.S. apologies for using English, but I prefer not to write using google translate.

When we done full wind-tunnel tests of the missile, we'll make a report as for AIM-120.

[tavarish palkovnik]

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. 


 

[BlackPixxel]

4 hours ago, tavarish palkovnik said:

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. 

Boost: 2.5 s with 5600 kg and 22.86 kg/s

Sustain: 5.5 s with 3500 kg and 14.8 kg/s

 

Ratio of boost to sustain thrust is a bit less than I would expect. The other simulated chart in the R-27 SAM proposal also suggests a higher boost/sustain ratio:

[tavarish palkovnik]

I just hope by ratio you didn’t think on ratio of seconds 

Forget those 1 or 2 seconds and honestly forget this diagram you attached at least for a while till and when eventually it comes in focus.

These numbers are interesting…but…

I tried to figure it out, however unsuccessfully. I can’t see nothing to get those numbers.

Guess that is again thrust diagram created “with lines” , 2,5 seconds of buster and then drop in no time to sustain. Like said, it doesn’t work that way and that is the most probably reason for such a small difference in thrust force values.

Thrust is in direct correlation with pressure so it means pressure ratio is also with small differential. But even and with that, difference between impulses (2400 vs 2320) is unexplainable small. 
 

These two facts are first issue. 
Second one is…those impulses are not case at 10km altitude (pa=0,0265 MPa) !

Let’s say density of fuel is 1,8. That is reality. From these numbers I see 138,5 kg of fuel in game. That is a lot!

And that is third issue. Let’s see what would be volume of such fuel grain.

 

 

Available volume of chamber is as it is, and this cylindrical grain is that fuel mass. Diameter of inner hole is minimal to fulfill criterium of Pobedonoscev. Of course real grain is not cylindrical, this is just to show that fuel weight is unreal and I understand it is compensation of impulses and thrust distribution ratio. Simplification to be direct.

And I will finish with sustaining thrust of 3500kg and with guess it is constant in 5,5 seconds.

 

 

Let’s return to “normal” configuration, and it is always good when having doubts to make reverse observation. This would be 14,8 kilos of fuel burned in last second. Burning rate 13,5 mm/s ! and now if anybody is willing I’m challenging him to try to go in reverse all to the buster 

 

Is it 8 or 9 seconds active time and what is true Cx f(M) … near to irrelevant 

[BlackPixxel]

The constant thrust in the two stages is just a simplification. So instead of having a complex curve, divide it into two sections and take the average values of those sections.

 

According to this table, the impulse per weight of the R-27ER should be 94.

So if you say that in DCS it carries to much fuel, does the its fuel mass have to be reduced while increasing the average ISP to keep that value at 94?

[tavarish palkovnik]

Question to you and others willing to contribute in this conversation: for which condition энерговооруженность of 94 is valid? 

Formula is clear Isp*mt/m0 … for example 256*130/354=94 or 238*140/354=94 or perhaps 266*125/354=94, maybe 277*120/354=94

Isp impulses are very questionable but in same time very easy to understand. Usually calculating Isp is given in ratio 40:1, ratio of chamber pressure vs pressure at the nozzle exit. Usually as 40 bar pressure in chamber and 1 bar atmospheric pressure, and some regular composite fuels based on AP with aluminum and hexagon could be with 245 s. OK, that is impulse at 40:1

These kind of rockets fly up there as well, don’t they. There atmospheric pressure is less than 1 bar, and chamber pressure is at least in buster stage over 40 bar, we all will agree in that.

So which Isp should be used for calculating thru thrust values? The ones for ratio 40:1 or some others individually calculated? That’s why I asked for data at 10km altitude.

I=K*Isp+190,3+76*pk-3,058*pk^2-7000*pa+25484*pa^2

This is a formula how to convert calculating Isp at 40:1 ratio to thru one taking in consideration chamber pressure and atmospheric pressure. K coefficient is variable and can be 0,96 or 0,94 or 0,9, can be called coefficient of thrust losses, depends of nozzles construction…does gas goes to full expansion or not, simplifying expressed term.

I know this is complication to the very end but I like to observe things that way, in thru technical form.

One example to show you…rocket 9M21 of Luna-M system.

 

Таблица стрельбы…it says impulse is 221 and fuel is NMF-2D

OK, Perm is giving for NMF-2D 208,4 (40:1)

 

 

And I’m giving to chamber pressure 100 bar…

I=0,96*208,4*9,81+190,3+76*10-3,058*10^2-7000*0,1+25484*0,1^2=2162/9,81=221

How much would be true impulse and thru thrust if this rocket would be lifted and burned up there at 10km…

 

 

[tavarish palkovnik]

No willing to contribute and discus 

It would be 249s. So true impulse and thrust respectively increase with increasing of altitude and increase is significant.

It would be great if there wouldn’t be other side of mathematic. 
I found paperwork about AIM-120 for DCS and there this 

 

Rocket is with almost same or with even slightly decreased drag coefficient with increasing of altitude in supersonic 

Based on this air friction is lower up there 

Edited January 21, 2022 by tavarish palkovnik

[BlackPixxel]

7 hours ago, tavarish palkovnik said:

No willing to contribute and discus 

I think you are the only one who knows the missile maths, so we cannot contribute to that, only read

You mean at higher altitude the rocket motors have more impulse than at lower altitudes? I wonder if that is simulated in DCS.

[tavarish palkovnik]

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!

[GGTharos]

16 hours ago, BlackPixxel said:

I think you are the only one who knows the missile maths, so we cannot contribute to that, only read

You mean at higher altitude the rocket motors have more impulse than at lower altitudes? I wonder if that is simulated in DCS.

It was certainly simulated for the 'Missile SFM' and it's likely so for the new FM they're using right now.   Missiles in 'SFM' had somewhere around +7% thrust at 12km compared to SL.  Don't quote me on the numbers though, it's been a very long time.

The change of altitude/pressure also changes the burn time along with manufacturing tolerance realities, and thus you have two sources for the cause of this range.

So any number you see for thrust, burn time etc should be followed by a question like 'at what pressure'.  

Edited January 22, 2022 by GGTharos

[tavarish palkovnik]

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 

 

[Чарик80]

Основным оружием бомбардировщиков Ту-95МС и Ту-160 на протяжении нескольких десятилетий остается изделие Х-55 и его модификации, в т.ч. новейшая ракета Х-555. Нет такой ракеты как Х-65, пытались сделать Х-65С противокорабельную.

[Chizh]

11 часов назад, Чарик80 сказал:

Основным оружием бомбардировщиков Ту-95МС и Ту-160 на протяжении нескольких десятилетий остается изделие Х-55 и его модификации, в т.ч. новейшая ракета Х-555. Нет такой ракеты как Х-65, пытались сделать Х-65С противокорабельную.

Считай что Х-65 это Х-555.

[Чарик80]

Вот это Х-555

 

[Чарик80]

Х-65СЭ,разница очень заметна

[Vladimir_V_T]

После обновления Феникс перестал поражать цели с дистанций близких к максимальным. Понятное дело, что по маневрирующим целям стрелять с 70-ти миль - бесполезное занятие, но всякие Ту-160 и Ил-76 он раньше с 70-ти миль сбивал без проблем. Сейчас же ракета (при пуске с таких расстояний) теряет цель сразу после включения своей ГСН. Такое впечатление, что её ГСН не хватает угла обзора, т. к. она пытается пикировать на цель, практически, под прямым углом. К сожалению не могу выложить трек, т.к. на F-14 они у меня никогда не совпадают.