R-27ER Experiment & Findings

[Capn kamikaze]

That's all that could really do, change the chemical composition and design of the motor, without a major airframe redesign

 

Note the last bit of that line.... changing the control surface size to make them similar to the AIM-120 would be a major airframe change.

[Sweep]

Which both are not significantly different, especially compared to the difference between the surface area of the fins, in purely aerodynamic terms with the exception of the midbody fins, the AIM-120 and AIM-7 are very similar.

 

The length of each missile is the same, the body diameter difference is nearly the same, only 20mm between them, the size of the rear fins is very similar.

 

An inch makes a lot of difference at >M2.5...

 

Doesn't it?

 

Ktulu!? Where's Ktulu? You know, Mister "I Wanna Play With Rockets IRL", he can answer that.

 

:D

[GGTharos]

They are significantly different. Straight up drag force is different just due to the difference in diameter.

 

The rocket motors are also very different, the AIM-7M is boost-sustain, the 120 has boost-sustain and from C5 and on, all boost.

 

Then you run into what the guidance can do to make the missile retain energy longer, which is another huge difference. That's not to say that you can't retrofit an AIM-7 to do this as well, but since the USAF ditched the AIM-7, it's just the USN that has examples of the modernized AIM-7P that can do such things.

 

Which both are not significantly different, especially compared to the difference between the surface area of the fins, in purely aerodynamic terms with the exception of the midbody fins, the AIM-120 and AIM-7 are very similar.

 

The length of each missile is the same, the body diameter difference is nearly the same, only 20mm between them, the size of the rear fins is very similar.

[GGTharos]

Nothing, they certainly did it with an AIM-9L when they were looking to test the aerodynamic effect of using AIM-120-like fins and nosecone :)

 

However, redesigning a missile when it's being replaced by a more modern one is another story.

 

So, then, you are saying that the AIM-7 could really not have smaller control surfaces? Why is that? What prevents Raytheon from sticking the AIM-120 fins and servomotors on the AIM-7?

[Capn kamikaze]

An inch makes a lot of difference at >M2.5...

 

Doesn't it?

 

Ktulu!? Where's Ktulu? You know, Mister "I Wanna Play With Rockets IRL", he can answer that.

 

:D

 

The overall profile makes the most difference.

[Capn kamikaze]

They are significantly different. Straight up drag force is different just due to the difference in diameter.

 

I don't agree that the difference is significant compared to the difference between the control surfaces

 

The rocket motors are also very different, the AIM-7M is boost-sustain, the 120 has boost-sustain and from C5 and on, all boost.

 

Which means that the burn profile for <C5 is not that different.

 

Then you run into what the guidance can do to make the missile retain energy longer, which is another huge difference. That's not to say that you can't retrofit an AIM-7 to do this as well, but since the USAF ditched the AIM-7, it's just the USN that has examples of the modernized AIM-7P that can do such things.

 

Already mentioned better guidance during mid-course flight as being a factor.

[Capn kamikaze]

Nothing, they certainly did it with an AIM-9L when they were looking to test the aerodynamic effect of using AIM-120-like fins and nosecone :)

 

However, redesigning a missile when it's being replaced by a more modern one is another story.

 

Which would be a significant change, going from a round dome tip typical of an IR missile to a sharp point typical of a radar missile is a significant change, going from a sharp point tip to a slightly sharper point tip is not significant, remember this is all in comparison to the significance of the difference in the size of the control surfaces between the two missiles, we're looking at what contributes the main aerodynamic difference, and it is clearly the control surfaces.

[Capn kamikaze]

IMO it simply comes down to this, of all the factors that are different between the AIM-120 series and the AIM-7 the main ones are the control fins, which in the case of the mid body fins, the AIM-7 has about four times the area as on the AIM-120, and the motor.

 

Now back to the topic of the R-27R, that missile is a lot larger than the AIM-7, it is longer, wider, weighs more (so retains more momentum) and has a lot more control surface area than the AIM-7, smaller mid body fins, but larger rear body fins, but it also has the forward body fins that the AIM-7 doesn't, but it has the capacity to fit a much bigger motor, never mind the ER version.

 

That capacity for a larger motor is what makes all the difference, and is why IRL the standard R-27R should have a longer reach than the AIM-7, and the ER should have a massively longer range, so if things were modelled correctly, and they are not, then the R-27R should be the best comparison to the AIM-7, not the ER as that is taking things way beyond a reasonable comparison.

 

In my experience, R-27R's tend to be launched before I can comfortably launch AIM-7's and expect them to get to were they need to go, and ER's LONG before.

 

Trying to pretend that the AIM-7 and R-27ER are comparable is nothing but an attempt to try to stack the deck.

Edited March 6, 2017 by Cap'n kamikaze

[GGTharos]

I don't agree that the difference is significant compared to the difference between the control surfaces

 

It's 10-11%, just by (presumably correct) back-of-the-envelope calculations. That difference is very significant. R-27R has 40% more drag force, the R-27ER will be more.

 

This is before we ever get around to fins, which have a much smaller effect on the drag force compared to the body in a zero-alpha environment.

 

So there's already a gigantic difference in drag force, and we also know from the DLZs that the R-27R doesn't have any sort of advantageous range capability over the AIM-7. What it does have is better time-to-target under certain circumstances.

 

Which means that the burn profile for <C5 is not that different.

 

Maybe, maybe not. It's a similar rocket motor setup, it's a similar burn profile, but 'not that different' is going a bit far since the setup and thus results on both missiles can be quite different.

Edited March 6, 2017 by GGTharos

[Capn kamikaze]

The difference in diameter translates to frontal surface area, but the effect of that can easily be less than the skin friction drag coefficient of an aircraft or in this case a missile, and that is dependent on "wetted area", which having much more control surface area will contribute to.

 

The missile is hardly going to be at zero alpha except for fleeting moments during the flight.....

[GGTharos]

Yes, but back-of-the-envelope math doesn't lend itself well to adding alpha as nicely as using Cd0 :)

[OnlyforDCS]

No disrespect to anyone, but please don't make this into another aerodynamics thread. Aerodynamics requires something called mathematics, something most people have a hard time understanding, let alone using. Generally speaking a longer, thinner object will have less drag than a thicker, shorter one. Thats about as much as anyone can say generally about the aerodynamics of anything without going into some serious maths. As ggtharos has already mentioned you can do back of the envelope stuff, but most people won't even bother with that. So a discussion about this is pointless. This thread is about the ER and its chaff rejection (or lack thereoff) anyway. So lets stick to that topic shall we?

[Seaeagle]

 

That capacity for a larger motor is what makes all the difference, and is why IRL the standard R-27R should have a longer reach than the AIM-7, and the ER should have a massively longer range, so if things were modelled correctly, and they are not, then the R-27R should be the best comparison to the AIM-7, not the ER as that is taking things way beyond a reasonable comparison.

 

Depends on the situation I think - the AIM-7M has a dual-stage motor and lofting capability, while the R-27R has a single-stage(boost only) motor and no lofting. So in the right launch conditions against a high altitude, non-maneuvering target, the AIM-7M may outrange the R-27R.

 

The R-27ER when launched at high altitude against a similar target would indeed far exceed both(up to some 100 km) due to the massive two-stage motor. But against a maneuverable target, it barely exceeds the range performance of the R-27R - against a "fighter type of target" the official quotes state up to 50-60 km for the R-27R and just above 60 km for the R-27ER.

 

Personally I think the R-27ER is more of a specialised bomber-intercept version, than the "super R-27R" that seems to be the general perception.

[*Rage*]

The aerodynamics discussion is interesting so perhaps that could be split off into another thread.

 

A reminder of the OP:

Well... This all started when I got really bored, however I think these findings should be shared, discussed and possibly have action taken to improve some aspects of the missile.

 

I am no missile expert and thus is why I'd like to get some input from people in the know or at least educated guesses/opinions on this matter.

 

I have attached 5 TacView tracks that you should have a look at to determine for yourselves if the experiment is valid. I was able to get consistent results for each.

Each experiment was conducted with an Su-27 as the launching aircraft and a drone using a Mirage M2000 on a static course deploying chaff.

 

Basically this shows the ineffectiveness of the R-27 and I believe to an unrealistic level. Furthermore I can only assume that the modelling of how the semi-active missiles track are incorrect, possibly on part of the radar's modelling.

 

Behaviour of the R-27 appears to mimic the behaviour of an active missile apart from requiring constant lock from the launching aircraft. The missile recognises all chaff and can guide to chaff that are not being illuminated by radar, chaff that are outside the radar cone. If someone can clarify this and has information on the area of radar illumination when the radar is in STT mode would be much appreciated.

 

In a 1v1 situation all the opposing aircraft is required to do is crank on gimbal limits at low cruise speed and chaff without any evasive manoeuvre while closing for the kill.

If someone has any history documentation on the testing of the R-27 would be awesome. I would assume the R-27 in testing would have hit chaff deploying non-manoeuvring drones with ease.

 

Thanks for your input.

[apocom]

In my experience, R-27R's tend to be launched before I can comfortably launch AIM-7's and expect them to get to were they need to go, and ER's LONG before.

 

Trying to pretend that the AIM-7 and R-27ER are comparable is nothing but an attempt to try to stack the deck.

 

Sorry, but your experience doesn't matter. The missiles in this game behave the same for all of us. No matter if you are a veteran or if this is your very first day.

 

We can all jump in an F15 fly at 2000m ASL, 800kph and 15°C and fire a M7 and the missile will behave the same for everyone.

 

And the way how it's implemented in the game at the moment is simply that the performance difference between a M7 and a R27R is bigger than the difference between a M7 and a R27ER.

 

Everyone can test it, and it can be repeated over and over again with the same results.

[Sweep]

Sorry, but your experience doesn't matter. The missiles in this game behave the same for all of us.

 

Is there anything that makes your experiences more valid than his?

 

Or is this just missile discussion threads fallacy #9876?

[Cik]

the mathematics of the missiles i'd guess.

 

saying "in my experience" doesn't matter when we know the mathematical framework within which the game operates, and we can do repeatable, empirical testing to determine objective missile behavior.

[Dudikoff]

Is there anything that makes your experiences more valid than his?

 

Or that the experienced behavior is more "off" from real life performance than the first one?

[apocom]

Is there anything that makes your experiences more valid than his?

 

Or is this just missile discussion threads fallacy #9876?

 

I'm not talking about my own experience, but the missile performance charts other people have made. And everyone can validate those charts or point out mistakes. Saying experience is different is just pointless. Flying under the same conditions missiles behave the same.

[*Rage*]

I'm not talking about my own experience, but the missile performance charts other people have made. And everyone can validate those charts or point out mistakes. Saying experience is different is just pointless. Flying under the same conditions missiles behave the same.

 

+1

 

Anyone and everyone can test for themselves the missile dynamics in a scientific matter. Experience can formulate a hypothesis, but it can't prove it.

 

As it stands, IN DCS, the R has far worse performance than the 7M. Which in turn has marginally worse performance than the ER. Fire the missile. Watch the Tacview. Tacview will even draw you a chart.

[Sweep]

I'm not talking about my own experience, but the missile performance charts other people have made. And everyone can validate those charts or point out mistakes. Saying experience is different is just pointless. Flying under the same conditions missiles behave the same.

 

Ahhh it was just the wording of what I quoted!! I understand now. :)

[JunMcKill]

If someone want to make the maths, take the CAD or 3D Studio Max's DCS missiles models (or design yours based in the designer data available online) and put them in this wind tunnel simulators.

 

http://www.aerorocket.com/AeroCFD/Instructions.html

 

http://microcfd.com/3d.htm

 

http://www.qualitysimulations.com/rcs/manual.php

 

https://www.grc.nasa.gov/www/k-12/TunnelSim/index.htm

Edited March 6, 2017 by JunMcKill

[Fri13]

Without any specific testing, I found out that AIM-7M is the most matching missile from western side to R-27ER.

 

The AIM-120B/C are then totally another class by engagements where R-27ER is just made obsolete with chaff, by not requiring the other party to maneuver at all so much like target of AIM-120 is required to do.

 

The R-27ER is very strange thing, as it really locks on the chaff from the moment it leaves the pylon and it is just lost. Doesn't make sense to even fire that missile as single chaff just most likely renders it obsolete.

 

This simply puts me so that when ever I need to engage F-15C in BVR and I have R-27 family missiles, it is just best to get full speed and go straight to F-15C and use R-73. And that is where the dangerous game is that if F-15C manages to launch AIM-9 (and usually do) the game play turns different as you just need to turn off after burners and flare to survive.

 

And R-27ET is the best thing just on same time as AIM-9 when engaging with 1x Su-27S vs 4x F-15C (AI max skill level) from 60km range and moving to 1-2km knife fight, that you can toss couple of those toward the other F-15C than what you are focusing.

 

But you are limited to 2x R-27ET so there is just a few changes what you need to choose, what target is the priority to get off from your back for few seconds?

 

So the fight is like a typical Kung-Fu fight, where you just spread hits to everyone in different order to keep them all getting on you at once.

 

The BVR is never the problem, as all missiles are so easy to avoid without notching etc. But when it comes to WVR combat, it is the one where kills are done.

 

Once I tested a lot of beaming, chaffing etc against AIM-7M and AIM-120C from max launch ranges, flying at 8km altitude and F-15C at 2km altitude. And no matter of what, their missiles always got me, even when they launched at 500km/h and I launched at 1250km/h. My R-27ER were just obsolete missiles. Chaff and it was straight heading on it.

 

So fighting a BWR combat at altitude was just nearly impossible against AIM-7M or AIM-120B/C missiles.

It was just way easier in Nevada even, get to ground level and fly at low altitude by denying the LOS and then hit when close.

 

 

Is there something wrong with the R-27 family?

 

Yes.... I can't proof it. I don't even care so much about it. But just thinking that how much Soviets has used it and sold it, even to countries that has in use the AIM-7 and AIM-120 family and still being in use. So it can not be so bad as it is in DCS.

 

No one would use a such missile that is rendered obsolete straight after launch.

 

Well, no one but a fool.... And that is always possible (look at the M2 Bradley development).

[DarkFire]

Without any specific testing, I found out that AIM-7M is the most matching missile from western side to R-27ER.

 

The AIM-120B/C are then totally another class by engagements where R-27ER is just made obsolete with chaff, by not requiring the other party to maneuver at all so much like target of AIM-120 is required to do.

 

The R-27ER is very strange thing, as it really locks on the chaff from the moment it leaves the pylon and it is just lost. Doesn't make sense to even fire that missile as single chaff just most likely renders it obsolete.

 

This simply puts me so that when ever I need to engage F-15C in BVR and I have R-27 family missiles, it is just best to get full speed and go straight to F-15C and use R-73. And that is where the dangerous game is that if F-15C manages to launch AIM-9 (and usually do) the game play turns different as you just need to turn off after burners and flare to survive.

 

And R-27ET is the best thing just on same time as AIM-9 when engaging with 1x Su-27S vs 4x F-15C (AI max skill level) from 60km range and moving to 1-2km knife fight, that you can toss couple of those toward the other F-15C than what you are focusing.

 

But you are limited to 2x R-27ET so there is just a few changes what you need to choose, what target is the priority to get off from your back for few seconds?

 

So the fight is like a typical Kung-Fu fight, where you just spread hits to everyone in different order to keep them all getting on you at once.

 

The BVR is never the problem, as all missiles are so easy to avoid without notching etc. But when it comes to WVR combat, it is the one where kills are done.

 

Once I tested a lot of beaming, chaffing etc against AIM-7M and AIM-120C from max launch ranges, flying at 8km altitude and F-15C at 2km altitude. And no matter of what, their missiles always got me, even when they launched at 500km/h and I launched at 1250km/h. My R-27ER were just obsolete missiles. Chaff and it was straight heading on it.

 

So fighting a BWR combat at altitude was just nearly impossible against AIM-7M or AIM-120B/C missiles.

It was just way easier in Nevada even, get to ground level and fly at low altitude by denying the LOS and then hit when close.

 

 

Is there something wrong with the R-27 family?

 

Yes.... I can't proof it. I don't even care so much about it. But just thinking that how much Soviets has used it and sold it, even to countries that has in use the AIM-7 and AIM-120 family and still being in use. So it can not be so bad as it is in DCS.

 

No one would use a such missile that is rendered obsolete straight after launch.

 

Well, no one but a fool.... And that is always possible (look at the M2 Bradley development).

 

It's been convincingly demonstrated here on this forum that SARH missiles are being decoyed by chaff bundles that are not even in the main emitter lobe of the attacking aircraft radar, i.e. chaff decoying missiles where the radar on the launch aircraft shouldn't even be able to 'see' the chaff.

 

Decoys in DCS appear to work on a simple cumulative probability system so the more that are launched, irrespective of relative position, relative velocity to the desired target or any other factors, eventually a SARH missile will be decoyed. It should also be noted that all SARH missiles suffer from this: The R-27s do, the AIM-7 does as does the Super 530.

 

With great respect to all, the discussions about various missile ranges are distracting from the real problem. All missiles have artificially low ranges in DCS but the reason for this is well known: they all have artificially large Cd. The reasons why this is the case are well known and have been stated many times by ED, even by Wags in a Youtube video. Missile range problems affect us all equally and that is not the real issue.

 

The real problem here is the effect that chaff has on SARH guidance. It's demonstrably unrealistic and all SARH missiles currently in the game have a Pk, even when launched in parameters, that is about 5% - 10% of the best real world figures that are publicly available.

 

My personal opinion is that this should be a critical priority to be fixed. We need SARH missiles to work realistically before we get any F-14s, F-18s or EF-2000's, otherwise when we do get those 4th gen NATO fighters nobody (outside of a few die hards :music_whistling: ) will every fly a Russian fighter again. I think we can all agree that limited viable choices would be bad for everyone..?

 

Hopefully the review that ED are doing on missile guidance will bear fruit. I'm confident that we'll see some sort of improvement in due course.

[Sweep]

The way some of us have interpreted the "chaff bug" is that it simulates what we don't have in the sim (chaff vs radar, jamming vs radar/seeker, etc.), so I wonder this:

 

If ED fixes the chaff bug, what of the actual CM rejection value? Can *that* be 'turned down' to simulate the non-existent countermeasure effects?*

 

You'd have less "chaff outside seeker FOV" and more realistic Pks for given scenarios, right?

 

Seems like the best idea until we get better EW/CM modeling.

 

*And that's not just for the ER, of course!