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Chizh

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23 minutes ago, TaxDollarsAtWork said:

The only issue is Chizh believes these figures to have no built in safety margin or cushion of extra energy. SME's and other parts of the MiG-29/Su-27 point to there being such a provision meaning, it should ballistically, out fly numbers stated by some margin, doesn't it?

Like slightly overshoot in stern WEZ shots for example

 


Chizh believes the figures are wrong, and that he knows better.

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Alright, I'm looking and I see that the missile is about 7km short according to the DLZ, if you consider the speed cut-off at M1.   What range do you get at M0.5?  I'm asking for a specific reason.

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36 минут назад, Max1mus сказал:


Chizh believes the figures are wrong, and that he knows better.

Yes it is. Your speculations are nothing more than speculations. We have slightly more sources of information than you think.

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Единственный урок, который можно извлечь из истории, состоит в том, что люди не извлекают из истории никаких уроков. (С) Джордж Бернард Шоу

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1 час назад, TaxDollarsAtWork сказал:

The only issue is Chizh believes these figures to have no built in safety margin or cushion of extra energy. SME's and other parts of the MiG-29/Su-27 point to there being such a provision meaning, it should ballistically, out fly numbers stated by some margin, doesn't it?

Like slightly overshoot in stern WEZ shots for example

 

Another speculation.

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Единственный урок, который можно извлечь из истории, состоит в том, что люди не извлекают из истории никаких уроков. (С) Джордж Бернард Шоу

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58 minutes ago, GGTharos said:

Alright, I'm looking and I see that the missile is about 7km short according to the DLZ, if you consider the speed cut-off at M1.   What range do you get at M0.5?  I'm asking for a specific reason.

Sure, but if we remember that Russian AMRAAM chart I do recall some saying the termination parameters were something like Mach 1.5 or 1.6 on the 120A estimate. Which is why we saw the 120B balistically out fly said numbers with the CFD data.

 

Now there is error in both in the case of the CFD probably minor and academic in nature. Meanwhile the Russian 120 chart probably more so (as a result of wrong assumptions maybe).

But it could still tell us something as Russian AIM-7E/F graphs weren't too terribly off the money in many ways. (I'd also like to point out the AIM-7M is still underperforming in terms of stern WEZ)

 

Not the worst thing to work with.

 

Which is a similar issue to what I think we're seeing with the R-27ER range interpretation. What if we flip that question on its head and assume the R-27ER range table as also having a similar cut off at 1.5~1.6 mach allowing it to overshoot said figures balistically?

 

I'd also like to say 3g for a few seconds seems in line with other CFD missiles and the available G terminally they tend to have at about mach 1.5

24 minutes ago, Chizh said:

Yes it is. Your speculations are nothing more than speculations. We have slightly more sources of information than you think.

Sure but this educated guess is based on what SMEs have said and the manuals as well as other observations.

 

The purpose of this thread is also for discourse and debate right?

The burden of proof is on you Chizh I would like to see what you base your theories on I already elaborated on mine.


Edited by TaxDollarsAtWork
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2 hours ago, Chizh said:

We have slightly more sources of information than you think.

 

It would be interesting to see them. The "well known charts" you have shared with us show that the ER is underperforming at under 5.000m of altitude. Meanwhile, unlike the ER, the AMRAAM has a significant reserve of energy and range compared to any source you have shared or that is commonly known on the internet.


Edited by Max1mus
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7 hours ago, TaxDollarsAtWork said:

But it could still tell us something as Russian AIM-7E/F graphs weren't too terribly off the money in many ways. (I'd also like to point out the AIM-7M is still underperforming in terms of stern WEZ)

 

The AIM-7 should do just a little bit better, but there's no way to prove this - additionally, there's really not much more that can be done with the rocket motor configuration as we know it.  You simply can't get much more out of it and remain within the realm of physical limitations which is why:

 

7 hours ago, TaxDollarsAtWork said:

Which is a similar issue to what I think we're seeing with the R-27ER range interpretation. What if we flip that question on its head and assume the R-27ER range table as also having a similar cut off at 1.5~1.6 mach allowing it to overshoot said figures balistically?

 

This would likely end up outside of the realm of physics also. 

 

7 hours ago, TaxDollarsAtWork said:

I'd also like to say 3g for a few seconds seems in line with other CFD missiles and the available G terminally they tend to have at about mach 1.5

Sure but this educated guess is based on what SMEs have said and the manuals as well as other observations.

 

The available g is highly altitude dependent.  At SL, you might be able to get 3-4g at M0.5.  The problem with these charts is that we might not know the full assumptions given.  They're like an introductory course, with detailed information hidden behind locked doors.  Absent of things like the sidewinder graphs, the CFD done by competent people is best tool we have.

 

7 hours ago, TaxDollarsAtWork said:

The purpose of this thread is also for discourse and debate right?

The burden of proof is on you Chizh I would like to see what you base your theories on I already elaborated on mine.

 

Right, so here are my arguments addressing the R-27ER in the tail-chase scenario at low altitude from the charts shown in the study: 

 

At our 'cut off' the missile has flown some 16km in 30 seconds, giving us about 530m/s (M1.56) average.  Your target aircraft has flown about 7-9km, so we're looking at a range of 25-27km.

In a tail-chase scenario, you must subtract this distance from the missile flight distance so you're looking at 7-9km launch range for a co-speed intercept.  If you want more overtake the range shrinks.

 

If you want to add enough rocket motor thrust you're probably going to run into physics problems, so that's probably out of the question.

If you want to change the rocket motor to sustain longer, you might be able to but then it won't match what we're seeing from the IRL motor graph.

You could tweak drag alone, but that would also probably push the numbers into the realm of fantasy.

 

You could tweak rocket motor and drag together and maybe keep things in the realm or reality but you'd likely be really stretching it.  (Of course, I could also be wrong, this is a ballpark educated guess which we could have easily tested within DCS in the past, but now we cannot).

 

Basically, the margins for doing anything at all and keeping it within known acceptable, reality-representing values would be very slim and might not get you anywhere near what you want.

 

There is of course the possibility that we don't know about some thing that would help here.  That's not fixable until we get new information.

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Reminder: SAM = Speed Bump :D

I used to play flight sims like you, but then I took a slammer to the knee - Yoda

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1 hour ago, GGTharos said:

 

The AIM-7 should do just a little bit better, but there's no way to prove this - additionally, there's really not much more that can be done with the rocket motor configuration as we know it.  You simply can't get much more out of it and remain within the realm of physical limitations which is why:

 

 

This would likely end up outside of the realm of physics also. 

 

 

The available g is highly altitude dependent.  At SL, you might be able to get 3-4g at M0.5.  The problem with these charts is that we might not know the full assumptions given.  They're like an introductory course, with detailed information hidden behind locked doors.  Absent of things like the sidewinder graphs, the CFD done by competent people is best tool we have.

 

 

Right, so here are my arguments addressing the R-27ER in the tail-chase scenario at low altitude from the charts shown in the study: 

 

At our 'cut off' the missile has flown some 16km in 30 seconds, giving us about 530m/s (M1.56) average.  Your target aircraft has flown about 7-9km, so we're looking at a range of 25-27km.

In a tail-chase scenario, you must subtract this distance from the missile flight distance so you're looking at 7-9km launch range for a co-speed intercept.  If you want more overtake the range shrinks.

 

If you want to add enough rocket motor thrust you're probably going to run into physics problems, so that's probably out of the question.

If you want to change the rocket motor to sustain longer, you might be able to but then it won't match what we're seeing from the IRL motor graph.

You could tweak drag alone, but that would also probably push the numbers into the realm of fantasy.

 

You could tweak rocket motor and drag together and maybe keep things in the realm or reality but you'd likely be really stretching it.  (Of course, I could also be wrong, this is a ballpark educated guess which we could have easily tested within DCS in the past, but now we cannot).

 

Basically, the margins for doing anything at all and keeping it within known acceptable, reality-representing values would be very slim and might not get you anywhere near what you want.

 

There is of course the possibility that we don't know about some thing that would help here.  That's not fixable until we get new information.

I've given some thought to the possibility of a Mach 1.5 cut off at all given alts not working given how mach is different given alt and air density

Possibly a humble more realistic estimate would be 150m/s + target speed at the cut off roughly both head on and tail chase

 

Would possibly manifest itself as overshooting the cut off at different speeds based on alt Mach 1.5 at some higher alts 1.3 or 1.2 at others possibly lower

 

It would also be inline with the additional speed needed at higher alt to pull said terminal 3g. Regarding new information, while I agree with you the terminal 3g and 150m/s are important pieces of information that can't be disregarded.


Edited by TaxDollarsAtWork
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What is the point of making long snd detailed posts here. I doubt you are going to get such detailed answers in this thread. Only things like:

 

9 hours ago, Chizh said:

Yes it is. Your speculations are nothing more than speculations. We have slightly more sources of information than you think.

 

9 hours ago, Chizh said:

Another speculation.

 

21 hours ago, Chizh said:

You are wrong.

 

21 hours ago, Chizh said:

Can't you see for yourself that this is a incorrect curve diagram?

^ Im sorry. How foolish of us to not see for ourselves that the russian missile should be unable to reach the target on the chart, while the AMRAAM should have a significant energy reserve.

 

The curve diagram must be wrong. It could not possibly be that at low altitude, the differences naturally are smaller. I should have seen for myself that if there is room for speculation, the AMRAAM should be better than expected and the ER should be worse than expected.

 

Funnily enough, the R-27R and T got normally improved to the same extent as the -120 did. It is even better than the AIM-7 now. Those curve diagrams were not incorrect? They are from exactly the same manuals...

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8 minutes ago, Max1mus said:

What is the point of making long snd detailed posts here. I doubt you are going to get such detailed answers in this thread. Only things like:

 

 

 

 

^ Im sorry. How foolish of us to not see for ourselves that the russian missile should be unable to reach the target on the chart, while the AMRAAM should have a significant energy reserve.

 

The curve diagram must be wrong. It could not possibly be that at low altitude, the differences naturally are smaller. I should have seen for myself that if there is room for speculation, the AMRAAM should be better than expected and the ER should be worse than expected.

 

Funnily enough, the R-27R and T got normally improved to the same extent as the -120 did. It is even better than the AIM-7 now. Those curve diagrams were not incorrect? They are from exactly the same manuals...

I wish Chizh would tell us the other sources he has regarding the R-27ER/ET. Are those sources more accurate than the manual?

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33 minutes ago, TaxDollarsAtWork said:

I've given some thought to the possibility of a Mach 1.5 cut off at all given alts not working given how mach is different given alt and air density

Possibly a humble more realistic estimate would be 150m/s + target speed at the cut off roughly both head on and tail chase

 

Head-on is sort of not a problem, the overtake speed is there to ensure proper fusing and terminal maneuvering - IMHO you don't need it head-on.

 

Quote

It would also be inline with the additional speed needed at higher alt to pull said terminal 3g. Regarding new information, while I agree with you the terminal 3g and 150m/s are important pieces of information that can't be disregarded.

 

Sure, but they also don't tell you what you seem to believe they tell you.  At least I'm not sure what the expectation is, personally.   In my humble and limited opinion from working rocket math generically, what I'm trying to say is that any improvement in tail chase range by increasing speed is not trivial as you have to achieve it either by:

1) Rocket motor change that would make the R-27 a different missile

2) Drag change that would make the R-27 a different missile

3) Both of the above in the most optimum combination, which may not be physically possible or would again result in something that isn't an R-27.

 

Unfortunately we can no longer do this experiment easily in order to check in DCS.  I don't think the R-27 has transitioned to the new FM yet (old FM is tweaked) and there might be a few changes to observe once this happens, but don't expect miracles.

 

Lastly, it's possible that the CFD contains egregious errors - stuff happens, anything from a poor 3D model to a bad skin drag factor.  Without ED fully publishing its methods and data we couldn't hope to do this analysis, although if someone had the knowledge and the desire, time and resources to put in the effort, an independent CFD could be done to at least settle some issues.

 

The takeaway here is that no matter how much you want to stick to the DLZ graph as the source of all truth, such things have been shown to contain errors as well.


Edited by GGTharos

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Reminder: SAM = Speed Bump :D

I used to play flight sims like you, but then I took a slammer to the knee - Yoda

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5 minutes ago, GGTharos said:

Unfortunately we can no longer do this experiment easily in order to check in DCS.  I don't think the R-27 has transitioned to the new FM yet (old FM is tweaked) and there might be a few changes to observe once this happens, but don't expect miracles.

 

Lastly, it's possible that the CFD contains egregious errors - stuff happens, anything from a poor 3D model to a bad skin drag factor.  Without ED fully publishing its methods and data we couldn't hope to do this analysis, although if someone had the knowledge and the desire, time and resources to put in the effort, an independent CFD could be done to at least settle some issues.

With what we've seen and not seen I'd be inclined to believe there is a lot of uncertainty on dimensions of the missile as well but also about the motor

@tavarish palkovnik Has been helpful in pointing out issues with the boost sustain distribution and how the motor exactly burns

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10 минут назад, Fuerte сказал:

А F-16 давно уже возят компактные планирующие бомбы GBU-39, но у нас их тоже нет. 

Они ж вроде с 2006-го года на вооружении, а у нас всё до 2005-го.

ПОЗОР ВОЕННЫМ ПРЕСТУПНИКАМ!!! ПОЗОР "АРМИИ" ДЕТОУБИЙЦ!!! ПОЗОР ТРУСАМ, СПОСОБНЫМ ВОЕВАТЬ ТОЛЬКО С МИРНЫМ НАСЕЛЕНИЕМ!!!

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Snimka zaslona (90).png

 

May I ask about this diagram, what is used as referent area while taking these values of Cx? Ussally it is normal cross section of the body, area of exposed diameter, but in that case those Cx values aren't correct. Unless area of wings or something else is referent area.

Some times ago I was interested in calculations of drag and lifting coefficients of the rockets, I even made one simplified program which calculate Cx function. For R-27R I was getting values i58 around 1 in active and 1,3 in passive at 0 m altitude. It means 1*0,308 and 1,3*0,308 or Cx=0,308 and Cx=0,4 at 0,5M and so on.

 

Let me show you one trick 😉

It is not truly correct but for the purpose precise more then enough.

 

164443_69614519_8F7A04E2-8E9D-4BC2-B2A6-A0810CB52670.jpeg   

 

 

This diagram shows for how much axial drag coefficient of Mig-29 is increased with two rockets R-27R on its launchers (APU)

Again, it is mathematically not correct but no matter, at 0,5M difference is 0,0024 or when take only rockets 0,0017 (0,0024-0,0007).

Those delta Cx values are based on referent area of the airplane and that is area of the wings which are for Mig-29 38 m2. All right then, just replace it with area of two rockets which is 0,23*0,23*3,14/4*2=0,083 m2 and result is 0,0017*38/0,083=0,79. That could be Cx for pair of rockets or in single case 0,395. Fair enough, i58 is 1,28 at 0,5M.

 

There is also another way...

 

164443_200141888_EAFD3E4F-FBF4-4D93-8397-1AFF72F9C833.jpeg 

 

Again Mig-29...it says that Mig-29 has 13,5 times higher drag coefficient then pair of R-27R rockets (230/17)

Now what is necessary is to have drag function of the airplane and here it is...

 

164443_84270287_509CB3E3-0E9B-445D-9DED-3DEC4BAA7B69.jpeg  

 

 

It is again with referent area of the airplane and at 0,5M it is 0,024 or for pair of rockets 0,0018 (0,024/13,5). Close to previous, all right.

0,0018*38/0,083=0,82 for pair or Cx=0,41 for single, i58=1,33.

 

And after making same for every Mach value you can get approximate function Cx f(M) in passive (engine out). Simple as that.

 

 

Book1-page-001.jpg 

 

Blue is first method, red is second and green is Cx58 function...referent area is always cross section of the rocket.

 

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Спасибо Маэстро !

It is true, not precise, not truly correct, but still it should be matter of percentages, percentages in level under 5, not more than that.

Pick value is at 1,1 Mach number, it is as it is and we can’t change it a lot or at all. There you have 0,05 which converted to cross section makes Cx 1,08 or i58 1,72 what is huge taking in consideration that R-27R is with all its aerodynamic disadvantages still nicely done.


While making step by step calculation, I’m still getting Cx 0,875 at 1,1 M or i58 1,4 and all that at 10km altitude where friction is higher. Coefficient i58 is what I use and although it seems irrelevant, for flights of 60 seconds long especially down under slightly increased Cx makes a lot of changes.

 

In that 0,875 friction of the body makes 18%, nose pressure 21%, bottom pressure 27%, and rest 34% is friction and pressure at wings. 
What ever try to disadvantage, Cx 1,08 is far a way.

 

Don’t take me wrong, I have no intentions whatsoever to change anything, just expressing my thoughts. In any case this new Cx function is significant improvement compared to previous function which at least as per my humble opinion was horrible 🤨

 

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@Маэстро

Hello,

 

What are the plans for development on the R-27? They fail to achieve the numbers on the official charts at 1.000m, and as i showed in DM they even fail to do so at 10.000m of altitude.

This is now especially worse due to the range reduction at low altitude mentioned in your recent newsletter.

On the non-kinematic front, there is of course the bug with the missile maneuvering when lock is lost. It would be interesting to hear about the progress on that too.

Thank you in advance.


Edited by Max1mus
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.....

 

And it was like this....

 

There is one old project rocket from late 50's of last century, it's interesting because for this one everything is available, from geometrical features to plenty of diagrams and of course Cx functions included. Not only project data but also results confirmed in live tests. And size is comparable to R-27R, this one was in calibre 280mm.

Drawn in scale together with R-27R with estimated measures is for comparison. Wings of R-27 are really huge, bigger then what I used yesterday so after taking some more papers and calculator I got slightly higher values.

 

Graph is of all three together with reference area of this antique one (0,0615m2). Red one is yours, green my calculation. Close, either green will get up a bit or red will get down a bit, but difference is very acceptable. All in passive, green at 10km altitude.

This 10% difference gives me nothing more then to say that as much as per me, I think Cx function of R-27R that you applied is very correct and very very close to real state. Even those genius form 50's and 60's had significant deviations between calculated and measured in flight. Some digits down or up is fair by all means.

 

I hope I'm not boring too much with this, it's just very interesting theme to me...and now I'm out...hope this time computer will not eat my words 

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14 часов назад, Jack1nthecrack сказал:

Hi Chizh,

Is there a possibility of reducing the CCM value for the R-27ET, currently it is easily defeated with only a few flares. Two flares is enough to defeat it. This cannot be realistic?

It depends on the target IR signature. If the IR signature is quite small, for example a MiG-21 in military mode, then a few flares will be enough to cover it. If the signature is large, for example a MiG-25 with afterburner, then a lot of flares are needed.

Единственный урок, который можно извлечь из истории, состоит в том, что люди не извлекают из истории никаких уроков. (С) Джордж Бернард Шоу

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It depends on the target IR signature. If the IR signature is quite small, for example a MiG-21 in military mode, then a few flares will be enough to cover it. If the signature is large, for example a MiG-25 with afterburner, then a lot of flares are needed.
Are flare rejection coefficients same for Aim9m vs 73/ET?

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15 минут назад, Breakshot сказал:

Are flare rejection coefficients same for Aim9m vs 73/ET?

Yes

Единственный урок, который можно извлечь из истории, состоит в том, что люди не извлекают из истории никаких уроков. (С) Джордж Бернард Шоу

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