IR signature versus engine thrust

Hi,

It's a very well known fact that the higher the output power (for props) or thrust (jet engines) always produce higher exhaust temperatures and thus a more intense IR signal. Although in reality the function (curve) between developed thrust, fuel flow rate and exhaust shapes which affect the infra red signature depends in a non-linear mode, in our DCS even if a linear function (gross) of output engine thrust alone (the fuel flow rate and exhaust shape being neglected) would make it brilliant in comparison to what it is right at this moment.

I've tested that no matter if my plane's engines are in full afterburner or completely shut down (well before an IR missile is fired, so the engines are cold enough), the enemy IR missile will only be confused by flares alone. The DIRCM seems to do nothing or I hardly see it being modeled, while the IR missile is fired at my plane and chases it while the engines are completely shut down like if they were in full afterburner.

My conclusion is that the IR spectrum has been very simplified in DCS, or to say, it sees all air targets no matter their engine thrust in the same way as vehicles on ground and the IR missile can home in on anything as long as it's alive and will only lose signal on flares or when being pointed at the Sun and nothing else.

Will we see IR missiles and/or IR homing capabilities depend on more than just flares and Sun into the near future? A simple linear function of the targets engines thrust (in pounds or whatever) versus output IR signature can be a strong enough key to successfully have DCS aircraft evade an IR missile easier by throttling engines to idle and very difficult to do so with afterburners lit. Is it so hard to program such a think?

Best wishes,

Mav.

I don't believe that lit afterburners will make it 'very difficult' to decoy a missile. There are real life examples of flares being decoyed despite AB - it's all in the flare type and design ... and number of flares, or point vs area flares.

I agree with you on the model, but it needs a bit more than just that to represent flares well, especially since we also have different generations of IR seekers represented in-game. For example IRCM should be effective in shortening the effective range of seeker tracking and this is evident with ETs. On the hand, up close this generation of missile will track the skin of the aircraft.

I agree that there are circumstances where the missiles track in-game when they should walk-off onto a string of flares instead as well. In particular, before FPA's there's at least a maximum target limit that a seeker can handle, among other effects - that would mean that with a certain amount of targets (not necessarily just flares), that seeker would have an almost perfect probability of being decoyed. This does not happen in-game.

I always assumed they were like the AI pilots, ie almost infallible. Must just be my crappy skills that mean an IR missile=death ;)

I'm no expert, but anyhoo... Having just spent an age dealing with RL Simulation of FLIR, and getting RSI in the process, I can guess that judging by the amount of time and data that was involved, and bearing in mind that this is probably not as complex as what is going on in a missile seeker head, that if they were using anything approaching real world figures, then I would expect to see a lot of data clogging the install folders just to deal with the subject.

As mentioned above, there is a lot more going on than just heat signatures. Different materials heat and cool at different rates, and are affected by ambient conditions in different ways. I also wonder how realistic the cooling of IR missile heads modelling is. Being a ground pounder by choice, I haven't read the manuals much on the subject, but I do know that IR missiles can have a quite limited shelf-life once they are activated, same goes for battery power on some missiles.

I'm sure there are some knowlegable people out there who can shed light on this.

I don't believe that lit afterburners will make it 'very difficult' to decoy a missile. There are real life examples of flares being decoyed despite AB - it's all in the flare type and design ... and number of flares, or point vs area flares.

 

I agree that flare and design types as well as the target's thermal dynamics widely affect the probability of loosing seeker track on the target, yet now I learn that AB won't mean too much difference and by what you say modern IR missiles use target shape comparison and other techniques to not loose target tracking. I have to admit that I don't know much about modern Chapparal, Avenger and newer manpad missile seekers and their tracking capabilities against different types of countermeasures, so the truth may lie somewhere in the middle of what I've said/thought and what the sim shows or maybe I'm not correct at all and the sim is actually much closer than what I suspect, but there's always a sense of doubt that I have to deal with!

Thank you for picturing/clarifying things better, I was looking only at one or tow aspects when in fact there are indeed dozens which affect the final result, yet we hope that at least what can be done (what the simulator is capable of computing) will be done giving the real life information.

I agree that flare and design types as well as the target's thermal dynamics widely affect the probability of loosing seeker track on the target, yet now I learn that AB won't mean too much difference and by what you say modern IR missiles use target shape comparison and other techniques to not loose target tracking.

If by modern you mean FPA-based missiles then they do some image processing stuff, yes ... but I wouldn't go as far as claiming shape comparison. The huge advantage of the FPA seeker is insane image resolution compared to everything that came before. It can easily separate decoys from the real target by all kinds of image processing methods - ie. blob tracking, size, etc.

And pre-FPA seekers - ie everything in-game, is not subject to this. They don't have the resolution to accomplish the same stuff, but they still have a bunch of ECCM like directional tracking etc. However, once you saturate that ECCM circuit the seeker's done.

I have to admit that I don't know much about modern Chapparal, Avenger and newer manpad missile seekers and their tracking capabilities against different types of countermeasures, so the truth may lie somewhere in the middle of what I've said/thought and what the sim shows or maybe I'm not correct at all and the sim is actually much closer than what I suspect, but there's always a sense of doubt that I have to deal with!

There are things to be fixed for sure - your gut feeling is right IMHO, you're just off on the details.

Thank you for picturing/clarifying things better, I was looking only at one or tow aspects when in fact there are indeed dozens which affect the final result, yet we hope that at least what can be done (what the simulator is capable of computing) will be done giving the real life information.

I hope so too but it's not quite that simple translating reality to efficient, fast game code :)

It seems that after the last updates, the IR missiles got even better. It became more difficult to make the IR seeker (of Chaparral and Avenger) break it's lock with the initially required number of flares (before the last updates) and high-G maneuvers. Now you need to puff a lot more flares giving the same conditions of distance between IR missile and target, target's heading, alt and speed. Judging by the simulation, I understand that these missiles (of Chap and Avenger) can still be deluded with flares, so they're not in the category of image processing target recognition? Or even the imaging seekers can still be deluded with flares (if the Chap and Avenger have such advanced missile seekers)? If the FIM-92 and MIM-72 seekers are still older ones (not IR imaging seekers), why have they been made more resistant to flares now?

Wikipedia's (quickest info helper) description on FIM-92 and MIM-72 can be useful for enhancing the performance levels of our missiles in DCS. For instance the MIM-72 seems to be much easier to trick with flares, requires more time to lock and is generally worse than Stinger (FIM-92). Although it says that the F and G(used in DCS) models have been improved, i'm not sure about how greatly was their performance increased over the A/B/C versions. In DCS, the performance between MIM-72 and FIM-92 seems almost the same, expect for max range, max. speed and possibly G-loads.

Thanks you for your time and patience!

Chapparal and FIM-92 use a UV channel in addition to IR, giving them better ECCM. In DCS this is all represented in a relatively simple manner - probability of decoying the missile per decoy in FoV, with some modifications for look up/down, aspect and a couple other factors.

IIRC chapparal has the only missile in the AIM-9 family that is known to have received a seeker with a UV channel.

The main difference between the two missiles mentioned here is indeed maneuverability, and the fuze - the FIM-92 only has a graze/impact fuze, while AIM-9 has a proximity fuze in addition to those.

There are other technical differences which are probably of no great importance. And IIRC there might be some hesitation modeled in the presence of pre-emptively released decoys but don't quote me on that. Bite-off on pre-emptive decoys is not modeled.

Thanks for letting us know about the Chap and appreciate your replies!;)

Is there a detailed documentation of how exactly the ir model / ir missile effectiveness is currently coded in DCS?

Is it true that the ir signature is the same, regardless the exhaust temperature / aspect angle ?

Are there any effective denial tactics for head on engagements?

(As an example can I use cranked entry + throttle idle / low power to avoid or at least delay an ir lock close / inside the rmin and survive the head on pass ?).