R-27ER Experiment & Findings

[The Black Swan]

...

I'd like to know what justification there is for ANY particular chaff rejection.

Drag charts, thrust values, and burn times give a solid foundation for accurate simulation of a flight model.

But what about chaff rejection or reaction to beaming?

Is there some documentation out there that says, my missile has a 40% chance of losing lock with chaff?

Is there solid info? Or is it just an educated guess based on which missile is newer and Pk in combat?

[GGTharos]

How about all of the above?

[captain_dalan]

Very good videos Ironhand! It's hard to argue against a scientific method. Double thumbs up :D

[Ironhand]

Here's the last one for a few days.

 

Super 530D & R-27ER with chaff 20KM range:

 

[The Black Swan]

How about all of the above?

 

Doesnt really answer my question.

I'm asking if there is hard data on how much chaff rejection a missile has, or if we kinda have to "wing it"

 

Pun most definitely intended

 

I guess what I'm getting at is...

If missiles chaff rejection in the sim creates a realistic hit percentage, what hard data do we have to say that is wrong?

Not saying estimating based on the modernness of a missile can't get close to accurate.

I'm just saying that the range and drag issues seem to be based on more facts and figures than the CM issue. Especially with the test that Ironhand did above giving a ~33% hit for the ER as he said. (Which if I remember correctly is around the average success of BVR missiles?)

[David OC]

There really is no right or wrong here, the ER should be more lethal and scare the crap out of an F15 pilot just like it would IRL (Not, pop a few chaff she'll be right). I want it as close to what we know it should be in theory, because that's all anyone has anyway. I would like to see more personality from the missiles in sim when fired from many different angles, speed and Gain the skills and experience from what we will have "theoretically" in this sim with the more "in depth" quirky missile simulation.

 

So we hope that someday someone will redesign the missiles logic using his or hers best guess with the info available in hand as most active seekers etc are classified.

Edited April 1, 2017 by David OC

[DarkFire]

DarkFire, concerning the R-27ER, the Pk across the 3 volleys in each track is higher than you think. @ 25km start Range, the Pk with chaff is 33.3% during the course of the track; no chaff it's 57.8%. With the 20 km start Range it's 28.9 with chaff and 57.8% without. The last volley is always almost 0% in all the samples.

 

Hmm, indeed it was. I re-watched the videos & manually counted all the missiles & got the same figures. Some more observations:

 

1) It appears that when the AI cranks, it really cranks, and it doesn't appear to adequately react to a target that turns away from the crank direction, therefore resulting in a dropped lock.

 

2) Other than stated sources such as USAF / USN reports from GW1 and anecdotes about admittedly still-classified British SARH missile testing at White Sands, I have no hard evidence with which to back this up, but I suspect that the Pk for missiles launched within parameters (including kinematic and geometrical considerations) should probably be somewhat higher, where no chaff is used.

 

3) I'm not entirely surprised that so many of the short range shots missed, particularly as the off-axis angle increased. I suspect that because both the R-27ER and Super-530 have huge boost motors that the necessary intercept paths went outside of the Gmax rating of the missile.

 

4) This is pure supposition on my part, but I suspect that both the R-27ER and Super-530 were designed with an intercept-the-long-range-bombers mindset, whether intended or otherwise, hence the very high top speed and acceleration values but somewhat lower Gmax performance; as opposed to something like the AIM-120 which was clearly designed as a more general air superiority missile.

 

5) I may have been wrong about the out-of-beam chaff illumination issue. Assuming a 3-degree half-power main lobe for the N-001, I'm not sure that any of the launched chaff in the videos would have been outside the illumination of the parent aircraft radar. What doesn't appear to be modelled (if it exists in reality, I don't know) is the ability of a missile to turn in again if the parent radar is able to re-acquire a target. I suspect that it may be possible while a missile is still under mid-course guidance, but possibly not after it turns on its SARH receiver.

 

I'm starting to realise just how complex a problem calculating Pk really is, and how many different factors can effect it right up to the point of impact / proximity fuse activation. I'm also starting to suspect that the necessary solution to perceived DCS missile guidance issue (separate from the range problem) is a gentle tweak rather than a radical change.

Edited April 2, 2017 by DarkFire

[IASGATG]

3) I'm not entirely surprised that so many of the short range shots missed, particularly as the off-axis angle increased. I suspect that because both the R-27ER and Super-530 have huge boost motors that the necessary intercept paths went outside of the Gmax rating of the missile.

 

4) This is pure supposition on my part, but I suspect that both the R-27ER and Super-530 were designed with an intercept-the-long-range-bombers mindset, whether intended or otherwise, hence the very high top speed and acceleration values but somewhat lower Gmax performance; as opposed to something like the AIM-120 which was clearly designed as a more general air superiority missile.

 

Just have to interject here and politely disagree. All of these missiles will be able to pull 35g within the first couple of seconds of launch. This is more than enough to get the missile into lead pursuit of a non manoeuvring target at any range longer than about 1.5nmi.

 

The days of jets out manoeuvring missiles ended in the 60s.

[Ironhand]

Hmm, indeed it was. I re-watched the videos & manually counted all the missiles & got the same figures. Some more observations:

 

1) It appears that when the AI cranks, it really cranks, and it doesn't appear to adequately react to a target that turns away from the crank direction, therefore resulting in a dropped lock.

 

2) Other than stated sources such as USAF / USN reports from GW1 and anecdotes about admittedly still-classified British SARH missile testing at White Sands, I have no hard evidence with which to back this up, but I suspect that the Pk for missiles launched within parameters (including kinematic and geometrical considerations) should probably be somewhat higher, where no chaff is used.

 

3) I'm not entirely surprised that so many of the short range shots missed, particularly as the off-axis angle increased. I suspect that because both the R-27ER and Super-530 have huge boost motors that the necessary intercept paths went outside of the Gmax rating of the missile.

 

4) This is pure supposition on my part, but I suspect that both the R-27ER and Super-530 were designed with an intercept-the-long-range-bombers mindset, whether intended or otherwise, hence the very high top speed and acceleration values but somewhat lower Gmax performance; as opposed to something like the AIM-120 which was clearly designed as a more general air superiority missile.

 

5) I may have been wrong about the out-of-beam chaff illumination issue. Assuming a 3-degree half-power main lobe for the N-001, I'm not sure that any of the launched chaff in the videos would have been outside the illumination of the parent aircraft radar. What doesn't appear to be modelled (if it exists in reality, I don't know) is the ability of a missile to turn in again if the parent radar is able to re-acquire a target. I suspect that it may be possible while a missile is still under mid-course guidance, but possibly not after it turns on its SARH receiver.

 

I'm starting to realise just how complex a problem calculating Pk really is, and how many different factors can effect it right up to the point of impact / proximity fuse activation. I'm also starting to suspect that the necessary solution to perceived DCS missile guidance issue (separate from the range problem) is a gentle tweak rather than a radical change.

I wouldn't read anything into the third volley results. By then, the AI and missiles are both thick as flies jammed into a small space. And I'm flying set to immortal so missiles are exploding and the "debris" might be attracting other missiles, etc.

 

I was really most curious about the 1st and 2nd volleys. I figure any missiles that missed in the first non-chaff volley should also be counted as "missed" for non-chaff reasons in the chaff volley. Think of the non-chaff run as the control run.

 

I'll pull the tracks together and post them as soon as I get a chance.

Edited April 2, 2017 by Ironhand

[DarkFire]

Just have to interject here and politely disagree. All of these missiles will be able to pull 35g within the first couple of seconds of launch. This is more than enough to get the missile into lead pursuit of a non manoeuvring target at any range longer than about 1.5nmi.

 

The days of jets out manoeuvring missiles ended in the 60s.

 

Could well be the case. I also agree with Ironhand that the situation for the 3rd wave is so chaotic that anything could be happening. Probably nowhere near controlled enough by that point to be able to draw valid conclusions.

[jackmckay]

Great job Ironhead. Good scientific approach on case. All we need now is hit-counter and numbers in charts.

 

Next I would like to see Pk on maneuvering targets and ECM effectiveness booth on SARH and ARH missile groups. And also it could be great if we could have charts with general data for each missile like geometrical data, weight, initial speed, Gmax, seeker cone angle etc. to compare missiles. Also, good option would be if we could have some Cd/AoA charts for each missile but that's the CFD problem case.

 

Also I have some questions regarding the way SARH missiles are fired in initial phase. Do they drop, turn and fire engine or drop, fire and turn? Most SAMs use first case.

Edited April 3, 2017 by jackmckay

[OnlyforDCS]

Might I add a request for a repeat of the tests? While I applaud your efforts Ironhand there is simply too much going on here to make a more complete analysis possible. The changing angles of the shots are the biggest culprit IMO.

 

Could you do a test for a target approaching offset by only a 5 or 10 degrees, instead of almost 45 degrees like in this test, then passing the firing platforms and beaming away?

[Ironhand]

I was curious as to how two identical scenarios would play out, if one dispensed chaff and one did not...Not meant to prove anything. Just interesting to watch and see, among other things, the effect of range and angles among other things...

 

...

While I was curious about the chaff/non-chaff behavior, I was also interested in seeing how the missiles behaved given the various positions of the target aircraft and the 30 launching platforms. The one thing that is impressed upon you is that 1) range matters and 2) angles matter. A single missile shot doesn't do that nearly as well as do massed missiles from similar angles. To anyone versed in this stuff, it makes sense. To a newby, it puts an exclamation mark on the point....

These started out as an experiment to see if I could blend the tracks as part of a tutorial on the Su-27's radar I've been working on. I found the results both intriguing and impressive. And posted them in this thread because of the subject matter.

 

Anyway, I have no intention of making this my life's work. :) There are all sorts of things that can be done with the ME and Notepad++ to generate more reliable test results. The biggest problem is consistency. So to whatever extent you can keep the test tracks identical, the more reliable the outcome is. In these tracks, for my purposes, there was a need for both my flight profile and the release of chaff be identical across all tracks. What follows is my methodology.

 

1) I recorded the initial track of my flight with the 30 AI aircraft and flew the mission pressing the "Q" key throughout the flight (even after all chaff was expended). (I also added a smoke cannister to make me easier to spot in external views.) Once saved, this track became the only flight that I actually flew.

 

2) After making backups, I changed the TRK suffix to ZIP and unzipped the file. Opened the mission file in Notepad++ and changed the chaff quantity from the default to 396. Saved the file and re-zipped the mission. Changed the resultant ZIP file's suffix back to TRK. This gave me enough chaff that I never ran out.

 

3) The no chaff version was even easier. Open the mission in the ME and change the chaff quantity to "0".

 

4) Varying ranges were accomplished by moving my aircraft closer to the AI in the ME.

 

5) Opening the TRK file in the ME, you can change the aircraft and missiles involved.

 

There are a lot of things that you folks would like to know and these are the ways you can find some of the answers. I'm attaching the tracks I've created so far from that original mission for your perusal. PM me if you'd like to set up any experiments of your own and I'll be more than happy to brainstorm on methodology.

 

But, for now I need to get back to life. :)

 

EDIT: Well, almost. I do have a few more videos that I captured this weekend. I'll blend them (I no have it set up so it only takes a few minutes) and post them later today--assuming nothing blows up at work.

Edited April 3, 2017 by Ironhand

[OnlyforDCS]

Fair enough. :thumbup:

[Ironhand]

The last few with the AIM-7M and R-27R (not ER):

 

AIM-7M & R-27R, 20KM:

 

 

 

 

AIM-7M & R-27R, 15 KM:

 

 

 

Hadn't realized how much faster the AIM-7M is. Just never paid attention.

[Breakshot]

 

Hadn't realized how much faster the AIM-7M is. Just never paid attention.

 

The effective practical range of 27R vs a hard maneuvering target is <8km

 

Seems Aim-7 has slightly better chaff rejection as compared to 27 series of missiles.

 

Conclusion: 27ER is much on Par with Aim-7M with one having slightly more legs, vs the other better tracking and PK %

 

 

@Ironhand: Could you run a comparison between 530D and Aim 7M?

Edited April 5, 2017 by Breakshot

[TAW_Blaze]

To a point they look pretty even and then later on the 7 seems much better. Is that because the R has shorter burn time? Looking at the video that's the only thing that would explain such a sharp dropoff.

[Breakshot]

To a point they look pretty even and then later on the 7 seems much better. Is that because the R has shorter burn time? Looking at the video that's the only thing that would explain such a sharp dropoff.

 

Correct!

 

However once any maneuvers are employed by the target, the difference is almost doubled kinematically, due to 27R basically being modelled as a "flying brick" drag wise.

 

The only thing that keeps ER on par is the extended burn time pushing it to M4.5

[JunMcKill]

To a point they look pretty even and then later on the 7 seems much better. Is that because the R has shorter burn time? Looking at the video that's the only thing that would explain such a sharp dropoff.

 

Reading the missiles_data.lua, they have differences in the burn time and thrust

 

R-27R (one stage motor six seconds accel)

-- t_statr t_b t_accel t_march t_inertial t_break t_end

-1.0, -1.0 , 6.0 , 0.0, 0.0, 0.0, 1.0e9, -- time interval

 

AIM-7M (dual-thrust solid rocket, 3.26 seconds accel and 10.86 march )

-- t_statr t_b t_accel t_march t_inertial t_break t_end

-1.0, -1.0 , 3.26 , 10.86, 0.0, 0.0, 1.0e9, -- time interval

 

The difference in the thrust, it's 25620 (R-27R with 11.3 kg/sec flow rate) vs 30645.0 (AIM-7M with 11.8 kg/sec flow rate)

Edited April 5, 2017 by JunMcKill

[Ironhand]

...

 

 

@Ironhand: Could you run a comparison between 530D and Aim 7M?

I can with the videos I have on hand. That only allows something for the 20KM Range:

 

 

 

And since I can't seem to resist:

 

Edited April 5, 2017 by Ironhand

[IASGATG]

All of these missiles make me sad. The R-27R is so slow compared to what it should be, the 7M and 27ER hide it a little with the long burn times but it's still really depressing.

[apocom]

I really like this kind of visualisation of the missile performance. It adds great to the performance charts.

[Seaeagle]

Reading the missiles_data.lua, they have differences in the burn time and thrust

 

R-27R (one stage motor six seconds accel)

-- t_statr t_b t_accel t_march t_inertial t_break t_end

-1.0, -1.0 , 6.0 , 0.0, 0.0, 0.0, 1.0e9, -- time interval

 

AIM-7M (dual-thrust solid rocket, 3.26 seconds accel and 10.86 march )

-- t_statr t_b t_accel t_march t_inertial t_break t_end

-1.0, -1.0 , 3.26 , 10.86, 0.0, 0.0, 1.0e9, -- time interval

 

The difference in the thrust, it's 25620 (R-27R with 11.3 kg/sec flow rate) vs 30645.0 (AIM-7M with 11.8 kg/sec flow rate)

 

The first part is clear - the R-27R has a single-stage boost engine with 6 sec burn time, while the AIM-7M has a two-stage boost-sustain engine with 3.26 and 10.86 sec burn time respectively.

 

But what does those thrust and flow rate figures mean? - the boost thrust is much higher than in sustain stage, so why is there only one figure for the AIM-7...is it some sort of "accumulated engine power"?

[IASGATG]

The first part is clear - the R-27R has a single-stage boost engine with 6 sec burn time, while the AIM-7M has a two-stage boost-sustain engine with 3.26 and 10.86 sec burn time respectively.

 

But what does those thrust and flow rate figures mean? - the boost thrust is much higher than in sustain stage, so why is there only one figure for the AIM-7...is it some sort of "accumulated engine power"?

 

There is separate numbers on the next line below for the different thrust values.

[Seaeagle]

There is separate numbers on the next line below for the different thrust values.

 

Ah ok that makes more sense - thanks.