RB24J / 9P missiles inaccuracies

[MysteriousHonza]

Hello
after recent changes to swedish RB24J, there are still some things off according to robotmuseum in sweden. They also provide closer information on seeker heads and its sensitivity in microns, iam sorry but its not easy to find charts for this but overall what i found out. Seekerhead of 2.3-2.9 microns cant really see anything besides hot parts of engine. 
That would mean, its current tracking angle of 120° (off tail - 30° into frontal hemisphere) in DCS is about double of what it should actually be. It cant really see IR signatures of planes 
images 3/4/5 are from this research https://www.mdpi.com/1996-1944/15/21/7726

Spoiler

Images from research PDF below. As shown, 3-5micron sensitivity is barely capable of seeing plane itself, let alone below. Its main source are heated engine parts. 

Missile info from robot museum says 2.3-2.9 microns, it should be cooled PbS seeker like on 9Ps, i sadly dont have any closer documentation on aim-9P but even if promotional papers shows increased acquisition angles or improved, it really shouldnt go above 90° unless they changed seeker to InSb seekers. Max 90 might be possible if they cross into 3.0+ microns territory but certainly not frontal hemisphere. I already made a post for R13M that eventually includes R60 and in that chart, we can see Aim-9H angles, which is cooled PbS seekerhead and missile is limited to 60-70° off tail. 

Another issue is engine. Papers from robotmuseum are stating 17 000N for 3,5 seconds instead of 5sec with 11 020Ns like in DCS, its using SAO-109 propellant which is indeed reduced smoke (correct as is) 
- 9P3/5s engine might be wrong too, swedish engine is probably just license built SR116, they share same composition. 

report for R60/R13M with Aim-9H

Spoiler

 

RB24J paper from robotmuseum (can be also found on their internet pages https://robotmuseum.se/robotar/rb-24j-sidewinder/)
+ SAO-109 reduced smoke confirmation

Spoiler

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Edited April 20 by MysteriousHonza

[Harlikwin]

Yeah, 2.3-2.9 is very much not in the traditional MWIR region (3-5  microns) associated with all aspect missiles. So undoubtedly a cooled PbS seeker head. And at least if I understand the 120 degree reference as being 120 degrees forward of the rear of the jet then there is little chance of the seeker seeing the tail from most aspects in any reliable fashion. Whatever data exists for the 9H seeker should be generally reliable for  cooled PbS seeker heads and generic acquisition angles, though of course that's all actually geometry and image dependent on the specific aircraft and its nozzle configuration. 

The one IR101 comment about the paper listed above is that while MWIR seekers can see IR plumes centered around 4 microns (plume is predominantly hot CO2), plume is RAPIDLY absorbed in atmosphere (as you can see the transmittance is near 0 in that region). And this seeker if it can see from 2.3-2.9 microns it can't see anything at 4 microns. The major advantage of MWIR seekers (PbSe and InSb was to be able to see things like plume and cooler airframe components from all aspects) But even there plume is basically undetectable past about 10km due to atmospheric absorption. 

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Edited February 15 by Harlikwin

[Маэстро]

Thanks, we will look into this

[MysteriousHonza]

On 4/19/2024 at 4:28 PM, Маэстро said:

Thanks, we will look into this

If you consider changing these angles. Looking at 9B/R3S would be nice too. Even though in most PERFECT conditions, they could see targets +-60° off tail, this angle would be literally impossible in any sort of teeny tiny bit worse weather than clear skies and perfect engine/plane. 
In case of jets in combat that move, change RPMs and so on, achieving that lock on angle is literally impossible. Hit rates and out of parameter shots from real life pretty much supports it. 
They are early super trash missiles and they are too reliable in DCS, you could literally slash their tracking angles by half to +-30° off tail until some IR missile rework can be introduced to make dynamic lock angles dependant on multiple factors. (9B still uncages on F5E)

Edited April 25 by MysteriousHonza

[Harlikwin]

Honestly the issue with this is what "hot" part the missile sees.

The uncooled 9B/R3S PbS seeker literally has to see the "inside" of an engine since its the only stuff hot enough for it to see. Hence the tracking angles being so bad.

Once you get to cooled PbS seekers, then its the exterior parts of the engine, i.e. the exterior petals and such and depending on how much insulation there is and what the actual look angles are. In theory if you are under a head on target you could likely get tone frontally if the seeker could see the rear of the jet from underneat, the problem being it will start guiding, and rapidly loose sight of it if its "leading" the target.   

Also, you guys really need to revisit this idea of "afterburners" increasing the lock on ranges all that much. Its partly true since the actual metal gets hotter, but the actual AB plume which is CO2 and H2O, gets rapidly absorbed by the atmosphere within a few km (and almost entirely by like 10km). Its a fairly complex set of phenomenon, cuz it sorta does matter at high alt (less atmosphere) versus (low alt, lots of atmosphere to absorb it). If you want to model it offline to get a feel for it try MODTRAN. And missiles like the 9B can't even see the AB plume. Thats just basic IR physics. 

 

Edited April 27 by Harlikwin