Ракеты в DCS

[nighthawk2174]

13 hours ago, Маэстро said:

Yep. My mistake, should be 4nm, but typo is still here. Ok, let's suppose chart is correct, in this case new question arises - how this possible? We know that drag is correct(several sources match), motor data is correct too(from Fleeman's book for example), hence missile range should be correct too. It cannot be lower two times.

So I went and ran my own sim of this in matlab using the drag curves I gave too you and used the thrust from SMC with the assumptions that A) Boost and Sustain propellant masses were flipped B) Used 3.5sec duration for the boost instead of 4.5sec. Sref was .0325 and motor and off drag was considered.  Our results are similar but it seems your sustain thrust is lower than what is in the SMC document.

Spoiler

 

 

However I have this document that lists the burn time as 4.5/11 sec, maybe its source is the SMC, maybe not.  IMO the difference were seeing between the estimates and in game is not drag but motor related.  It could be that the boost is actually 4.5 sec but either the propellant mass or thrust is wrong.  This possibility of error in any of the motor variables unfortunately opens up a lot of variation of stats that could be right.

For the sake of argument lets say only the motor times (4.5/11), boost thrust, and total fuel mass is correct but the thrust and fuel mass is wrong for the second stage then it could look like (if the ISP values stay the same):

Spoiler

This is a massive difference in performance. 

 

Just to hammer this home further lets say the Burn times are correct for both boost-sustain and that the fuel masses are both correct (as in correct when flipped from the document).  However the Boost thrust is wrong:

Wildly different from the same boost thrust but closer to what Ed has.

 

 

TLDR

Essentially to sum up the difference were seeing between estimate and AIM-7 is almost certainly thrust related.  It's kind of unfortunate the one document with these stats has so many errors as depending on what's right or wrong could lead to very different performing missiles.  Its a rather unenviable position as we can't exactly know for sure right now what's 100% correct.  There are so many variables impacted by just one number being wrong that it can wildly impact the outcome.

[Маэстро]

5 hours ago, nighthawk2174 said:

So I went and ran my own sim of this in matlab using the drag curves I gave too you and used the thrust from SMC with the assumptions that A) Boost and Sustain propellant masses were flipped B) Used 3.5sec duration for the boost instead of 4.5sec. Sref was .0325 and motor and off drag was considered.  Our results are similar but it seems your sustain thrust is lower than what is in the SMC document.

  Reveal hidden contents

 

 

 

 

 

 

 

 

Excellent. Now you may see what there is definitely some issue with launch range charts.

 

 

5 hours ago, nighthawk2174 said:

However I have this document that lists the burn time as 4.5/11 sec, maybe its source is the SMC, maybe not.  IMO the difference were seeing between the estimates and in game is not drag but motor related.  It could be that the boost is actually 4.5 sec but either the propellant mass or thrust is wrong.  This possibility of error in any of the motor variables unfortunately opens up a lot of variation of stats that could be right.

For the sake of argument lets say only the motor times (4.5/11), boost thrust, and total fuel mass is correct but the thrust and fuel mass is wrong for the second stage then it could look like (if the ISP values stay the same):

  Reveal hidden contents

 

 

 

 

 

 

We have this document too, but at the moment the best reference for us is Fleeman's book, please pay your attention to motor data in this book.
Regarding time of work and thrust...first of all you should consider what the main thing you need to know is the total impulse of motor. Even if you change burn time(within resonable limits) and thrust, but retain total impulse the same you will not get noticeable difference in missile performance.When you change only time or only thrust Isp of fuel(and total motor impulse) became very wrong. We know exact amount of propellant from several sources and it is 133lb. We know the type of fuel and Isp so our estimations is correct. 

5 hours ago, nighthawk2174 said:

TLDR

Essentially to sum up the difference were seeing between estimate and AIM-7 is almost certainly thrust related.  It's kind of unfortunate the one document with these stats has so many errors as depending on what's right or wrong could lead to very different performing missiles.  Its a rather unenviable position as we can't exactly know for sure right now what's 100% correct.  There are so many variables impacted by just one number being wrong that it can wildly impact the outcome.

It wont lead to very different performance, because we know mass of fuel and Isp, even when you don't know the exact Isp there is still hard limits on its value and thus limits on error in performance.
But as I said above the Isp is known at least form Fleeman's book.

[nighthawk2174]

59 minutes ago, Маэстро said:

We know the type of fuel and Isp so our estimations is correct. 

Understood what are ED's current estimations?  As i'm curious as the SMC sustain is more potent and the values referenced in Fleeman match SMC.

59 minutes ago, Маэстро said:

It wont lead to very different performance, because we know mass of fuel and Isp, even when you don't know the exact Isp there is still hard limits on its value and thus limits on error in performance.

Yeah ultimately it's only small differences (of note the two blue lines have the same total impulse) were talking about here now for the Boost-Sustain motors like the AIM-7/120B.  There are far bigger issues with the missiles then this.  Which speaking of the 120B did you have a chance to examine my reddit post regarding my thoughts on its boost thrust?

59 minutes ago, Маэстро said:

But as I said above the Isp is known at least form Fleeman's book.

Yeah correct me if i'm wrong but it still is a range of values such as 220s-250s for the type of fuel used iirc.  

[Маэстро]

4 hours ago, nighthawk2174 said:

Understood what are ED's current estimations?  As i'm curious as the SMC sustain is more potent and the values referenced in Fleeman match SMC.

Our current estimation matches Fleeman's book. But Fleeman in fact does not match SMC. Look, SMC tells us

Boost 5750lb for 4.5s -> total boost impulse 25875lbs. 83lb of propellant ->  312s Isp

Sustain 1018lb for 11s -> total sustain impulse 11198lbs. 52lb of propellant ->  215s Isp
Total propellant weight 135lb, total motor impulse 37073lbs -> average Isp ~275s

 

Does not look very realistic for me. Ok, let's see what Fleeman tells us(page in attachment)... that looks ok. Note, motor data in attachment is for 20Kft altitude, at different altitude thrust(and Isp) will be different too. The reason for this is pressure losses in nozzle due to atmospheric pressure. So at SL Isp is minimal and increases as altitude increases. This modeled in DCS, and motor data you see in scripts is for SL. DCS AIM-7 motor data matches Fleeman's one(with recalculated Isp for SL 247 and 209s).

 

4 hours ago, nighthawk2174 said:

Yeah ultimately it's only small differences (of note the two blue lines have the same total impulse) were talking about here now for the Boost-Sustain motors like the AIM-7/120B.  There are far bigger issues with the missiles then this.  Which speaking of the 120B did you have a chance to examine my reddit post regarding my thoughts on its boost thrust?

Ok, will take a look

4 hours ago, nighthawk2174 said:

Yeah correct me if i'm wrong but it still is a range of values such as 220s-250s for the type of fuel used iirc

Yep, approximately. Range may be a bit wider depending on conditions(propellant temperature, chamber pressure, exit pressure etc ), but upper bound should not exceed 255-260s for real motors in normal conditions. 

[BlackPixxel]

On 4/17/2021 at 5:00 PM, Max1mus said:

 

An AIM-120 will now outspeed it at 8-10km (or, up to 6km flyout), meaning that when this distance is reached, you have 0 options left assuming equal positioning. That is quite a significant nerf.

 

 

Ok I see.

 

That makes the new motor configuration indeed far inferior to the old one.

Long range performance stays the same, but in close range the distance traveled lacks behind.

It does not make sense for the real missile to have this new configuration instead of the old one, because there is no advantage, only a disadvantage.

 

In the changelog they write that the new one provides a "more realistic velocity profile". But now I wonder if that is true.

The reason for a boost/sustain configuration is to allow the missile to accelerate faster after launch. But with the current configuration the difference in thrust between the stages is quite small. It no longer provides that effect.

It looks like ED is trying to match the Bauman graph. But the acceleration of the missile in this graph is contradicting the real values from the MiG-29 manual. (Burntime of 8,6-11 s, Thrust of up to 7500 kg). So the acceleration part of that graph is very questionable.

I don't know from what date the Bauman chart is, but in case it is from 2018 or so then maybe they have just looked at the video of the R-27ET hit on the F-15? There the motor seems to burn for roughly 8 seconds (hard to tell beyond that point, because the rocket is already so far away and the distant smoke trail covers only few pixels). Who kows how old the missile is that got fired there.

 

The values mentioned in other forums (2 seconds of 7500 kg, 8 seconds of 2238 to 2500 kg) seems like a much more reasonable configuration.

Quick acceleration (although not as much as the old DCS configuration) but then a long and strong sustain. At low altitude the missile would not slow down after 3 seconds as it did with the old config, and the missile not reaching such a high peak speed as with the new config would result in a more efficient use of the motor burn and higher flight range.

Against maneuvering targets the 10 seconds of total burn time are also more favourable than the 8 seconds.

 

The MiG-29 manual has some of the key motor values black and white, and those are from real missile tests more likely than not. They should more or less match the DCS motor, but now they no longer do.

 

Here it even says that the thrust is gradually reduced, instead of two discrete thrust outputs.

http://militaryrussia.ru/blog/topic-103.html

Edited April 18, 2021 by BlackPixxel

[Hoarfrost]

17.04.2021 в 18:00, Max1mus сказал:

As i said, test with a jamming target where EOS does not turn on. ER-27 will still loose track. Its the countermeasure coefficient of the missile, not the radar mechanic, that is at fault. For the most part.

 

Тем не менее это хоть какое то улучшение в + р27эр, и ЕД обещали его в текущем обновлении, ждём в следующем. Пока о р77 можно только мечтать когда найдут время. 

[nighthawk2174]

 

5 hours ago, Маэстро said:

Does not look very realistic for me. Ok, let's see what Fleeman tells us(page in attachment)... that looks ok. Note, motor data in attachment is for 20Kft altitude, at different altitude thrust(and Isp) will be different too. The reason for this is pressure losses in nozzle due to atmospheric pressure. So at SL Isp is minimal and increases as altitude increases. This modeled in DCS, and motor data you see in scripts is for SL. DCS AIM-7 motor data matches Fleeman's one(with recalculated Isp for SL 247 and 209s).

 

Good to see that this detail has been modeled in DCS.  It is significantly more detailed than the older missiles.

 

[TotenDead]

4 часа назад, BlackPixxel сказал:

 

I don't know from what date the Bauman chart is, but in case it is from 2018 or so then maybe they have just looked at the video of the R-27ET hit on the F-15? There the motor seems to burn for roughly 8 seconds (hard to tell beyond that point, because the rocket is already so far away and the distant smoke trail covers only few pixels). Who kows how old the missile is that got fired there.

 

 

Так там же не ЭТ, просто Т

[BlackPixxel]

5 minutes ago, TotenDead said:

Так там же не ЭТ, просто Т

 

The video is an ET. Check the ratios (for example length from nose tip to canards divided by canards to rear end).

[tavarish palkovnik]

Всем привет !

 

Interesting discussion you have here, regarding R-27ER and generally. Just to explain diagram you are talking about, velocity in function of time for R-27ER with maximal launching velocity values. That diagram is from year 2013, and authors of the text are more then relevant. As reference to the diagram is written ''Авиационные управляемые ракеты Р-27 и Р-27Э. Техническое описание. Часть 2, 1987.'' More then enough to me.

Unfortunately that ТО и ИЭ is still very carefully hidden, I hope in soon time at least some graphics will be published so then all will be much more clear how those rockets look inside. R-27R and T are available as cutaway models, but nobody to make clear photo of motor chamber, just one photo would be enough for determination of how that motor works. For ER versions seams cutaway models are not available, or I haven't seen such.

 

In any case, this is how I estimate motor of ER from inside, in part of solid fuel block. More or less estimation is done based on similar missiles in sizes and times of design. It is monoblock of composite, with inhibited external surface, burning from inside and from ends. Part with slots is with degressive burning, cylindrical part is with progressive burning and together it makes near to neutral burning in all 8 seconds.

 

Total weight of block in estimated dimension and with density of 1,75 is 130kg what with estimated impulse of 250s gives near to 40kN of thrust, continuously. I will say nominal pressure rate in chamber would not be over 70 bars and let's say nozzle diameter could be 70mm...70*70**3,14/4*7*1,6=43080N...fair enough.

Burning velocity of composite at 7 MPa should be around 10mm/s...and based on these inputs I draw fuel block and result is that fuel comsumpition is almost constant 16,25 kg/s.

 

Very similar configuration is in motors of R-33, Kh-58, Neva and many others, same degressive/progressive principle is used in construction of Smerch rocket. I truly believe same is with R-77 as well, and of course R-27ER. 

 

Of course, estimation don't need to be correct but also can be near to actual. There are number of options, 4 slots or maybe 5, 6 or maybe 3, longer and/or shorter, part of external surface also can be burning what will give more thrust in start and less with end. But thrust of 7,5 tons in period of 2 seconds for me is not realistic. Eventually that could be force peak like every other motor has, in very first beginning of active time, after around 0,1-0,3 seconds counting from burning start.

 

In any case, if someone has opportunity to make short look in ТО и ИЭ, there should be graphic of the missile and only one single graphic would be enough. Plus I hope also someone will make cultural  photo of cutaway model of R-27R  

 

 

  

 

 

 

[BlackPixxel]

The MiG-29 manual says thrust of up to 7500 kg, so it could indeed be a peak thrust and not a constant thrust of the boost.

 

This is what the manual says:

Quote

Ракета Р-27Э комплектуется двухрежимным твердотопливным двигателем массой 192,5 кг повышенной тяги (до 7500 кг), работающим в течение 8,6—11 с.

 

Not sure if this is of any help:

[tavarish palkovnik]

Thanks for photos.

I've been few times in Kecskemet but never with exposed R-27R-UR on display, pity.

Photos, this last one especially, is the finest what can be found on the Internet. Seams like regular ''star'' configuration, more ore less it should be in line with R-60, R-73, R-24 etc. They all have approximately same D/L ratio and star all way long can give neutral burning.

 

[BlackPixxel]

@tavarish palkovnik

What configuration of boost/sustain would you expect the R-27E to have?

 

Right now after the DCS update it is 2,5 s of 54935 N followed by 5,5 s of 34335 N. So the difference between boost/sustain is rather small, and the missile no longer benefits from a rapid acceleration.

 

Whether they are accurate or not, here are some other examples of boost/sustain missiles from DCS:

 

R-27ER before the update:

3 s of 73500 N, 7 s of 14560 N

 

Aim-7:

3.7 s of 25200 N, 10.8 s of 4142 N

 

Aim-120B:

2.1 s of 20076 N, 5 s of 12617 N

 

R-33E:

5 s of 70000N, 15 s of 12000 N

 

Super 530D:

2 s of 38000 N, 8 s of 15250 N

 

With exception of the Aim-120B they all have a much stronger boost compared to the sustain.

[FoxAlfa]

Will HOJ missiles get PN since it is not range depended? Currently they just go directly at the target which is not efficient. 

[tavarish palkovnik]

These number for R-33 are for me absolutely unreal. From several reasons.

First is just regular mathematic of the weight, if it is 70kN in period of 5 sec and 12kN in next period of 15 sec it means that total weight of the fuel should be 220kg (28,5 kg/s + 5kg/s) and all that with quite high specific impulse value of 250 kgs/kg. It is 45 kg more then my estimation about fuel weight.

Next is this 12kN ... seams like R-33 has very tight nozzle diameter, could be even 70mm. Thrust is always in correlation with pressure and 12kN of thrust means that pressure is very low, under 20 bar (not sure if burning is even regular on such pressure rate).

 

With available cutaway model and estimated dimension as below, I'm getting close but still different numbers. It is indeed motor with two regimes, I'm giving 6 seconds of boost phase and 9 seconds of sustain. In first regime fuel consumption without effect of erosion could be 18kg/s and in rest 7,5kg/s what makes total of 175kg as drawn and calculated by denisty of 1,75 kg/m3. It is 35% of missile weight, fair enough for period of design.

 

First regime is with 18*250*9,81= 44145 N => pressure 44145/1,6*4/3,14/70/70=7,2 MPa => burning rate estimated 72^0,36*2,1=9,8mm/s

Second regime is with 7,5*250*9,81= 18395 N => pressure 18395/1,6*4/3,14/70/70=3 MPa (still low) => burning rate estimated 30^0,36*2,1=7,2mm/s 

 

 

 

 

[Арсений]

Товарищи, я правильно понимаю, что все измы пока в бетте? 

[tavarish palkovnik]

Можешь ли упростить значение «измы пока в бетте»

Мой русский не на очень высоком уровне чтобы понимает такое выражение.

[KBAC]

18 минут назад, tavarish palkovnik сказал:

Можешь ли упростить значение «измы пока в бетте»

Мой русский не на очень высоком уровне чтобы понимает такое выражение.

Изменения пока в бета-версии DCS.

[Арсений]

Спасибо

 

[tavarish palkovnik]

If it is not problem, at least asking is not a problem  , is it possible to have complete scan of the pages from this manual where launching zones and missile to fighter distances are described for these few missile types (27R,T,ER,ET,73). Graphics and diagrams without explanations are only one part for full understanding.

I'm interested in internal ballistic but also if not even more in external ballistic, and fact is one of other are undividable.

 

In text following diagrams for missiles of subject airplane should be something about character of the trajectory. Is it flight with kinematic overload, with kinematic and dynamic overload, is it eventually initial ''gorka'' involved, how velocity values are included, true or instrumental speed, what is the character of the target beside it's velocity, altitude and parameter. What makes end limits of the zones, should not be total active time of gas-generator but something related with available (reserve of) overload of the missiles and kill probability. 

[Chizh]

К этим диаграммам нет никаких пояснений.

Принимается гипотеза, цель прямолетящая, не маневрирующая. Дальность указана с учетом запаса по минимально необходимой для перехвата цели располагаемой перегрузке 3-5g, минимальной скорости сближения 150 м/с, либо по окончанию работы энергосистемы 60 секунд. Что наступит раньше.

[BlackPixxel]

On 4/20/2021 at 11:58 AM, tavarish palkovnik said:

These number for R-33 are for me absolutely unreal. From several reasons.

 

 

 

I think the DCS R-33 is more or less unchanged from the old Flaminc Cliffs days, where it was more a game than a simulation.

I believe that the R-33 in DCS even lofts, which I doubt it will do in the real world.

 

Here is how the R-27ER flew with the previous version of DCS. A clear boost-phase, accelerating the missile quickly up to speed.

 

Here is how the R-27ER looks with the new motor values. The boost is barely noticeable, the acceleration is almost constant.

 

The Bauman-chart shows an almost constant acceleration as well:

 

There is a tiny decrease in acceleration after 2..4 s, but such a decrease is also present in this Aim-9 chart, for example.

 

 

To me it looks more like Bauman chart does not have any boost at all. Maybe the focus of this chart was more on the overall long range performance, including a boost would not change no real difference in that regard.

Edited April 22, 2021 by BlackPixxel

[Teknetinium]

It is very important how fast the missile reach the target, at the moment it seams it take longer time then it should. 

Edited April 22, 2021 by Teknetinium

[TotenDead]

23 минуты назад, BlackPixxel сказал:

 

I think the DCS R-33 is more or less unchanged from the old Flaminc Cliffs days, where it was more a game than a simulation.

I believe that the R-33 in DCS even lofts, which I doubt it will do in the real world.

В жизни, как и в игре, у Р-33 имеется возможность полета по навесной траектории. 

23 минуты назад, BlackPixxel сказал:

 

 

Here is how the R-27ER looks with the new motor values. The boost is barely noticeable, the acceleration is almost constant.

 

Действительно, вообще почти не видно. Выглядит как минимум странно

 

[tavarish palkovnik]

Few observation with graphical explanations regarding external ballistic of R-27ER. Those diagrams and monograms from manual are indeed for horizontal flight of the rockets, it means flight with kinematic overload. Overload is not continuous but it is present most of the flight time, later a bit more about it. The fact about such kinematic overload and profile of the flight makes calculations much more difficult then what is case with rockets of surface to air systems.

 

 

 

Sample cases, equal speed of fighter and target, 250m/s (900km/h). Nomogram gives flight time and maximal distance of the rockets from fighter, and those points are of course points when velocity of the rocket become equal and less then velocity of the fighter, 250m/s.

In numbers for three altitudes, 30,5s ; 40,8s and 57,4s (8000m ; 18000m and 21000m)

In graphic it is like this...

 

 

Red lines are flight of the fighter, blue lines flight of the target and green lines are flight of the rockets when having speed over constant speed of the fighter. It can be seen that at altitude of 5km terminal velocity (impact velocity) is near to 250m/s, at 1km and 10km velocity of the rockets when approaching target is less then speed of the targets...this is for ground systems absolutely unacceptable. This also gives many answers why these rockets are questionable for any kind of manuvarable target.

In addition with black lines are presented trajectories of ''gorka'' , flight without overload, just initial angle. Those trajectories can be easily calculated and it helps to understand and to have comparison with horizontal flight.

 

   

 

Finally diagram of the velocity, black lines are for those gorka trajectories and green dashed for flight with overload. Speed reduction is significant as expected to be. And red trajectories are for comparison with diagram presented by Bauman. These two are speed in function of time with maximal launching velocity (480m/s and respectively 600m/s) at 5km and 10km...and flight with gorka, without overload.

When compare these two with functions of Bauman's diagram for same input, can be seen that their have significantly lower terminal velocities and that means only one, those are velocities for horizontal flight with overload.

 

Making integration of such horizontal flight without functions Cy f(M) Cn f(M) Cx f(alfa) and others is not possible, can be done with assumptions and with data of some other similar rockets and using ''hard method of convincing rocket to keep it horizontal''

''Curvings'' of the Bauman's diagrams in active time for me are from that reason, angle of attack is present all the active time. Curvings in passive as well