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** AIM-54 Phoenix CFD Whitepaper! **


Cobra847

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You're reading it wrong. This is for either a ballistic or appropriately guided flight. The missile can achieve this by lofting all by itself, though if you pitched up you save it a bit of energy doing so. N/A DCS until there's appropriate guidance.

 

I think the real take-away from this is that if you want range, you need to loft - ie. the missile has to spend a bunch of time gliding down to target from high altitude.

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You're reading it wrong. This is for either a ballistic or appropriately guided flight. The missile can achieve this by lofting all by itself, though if you pitched up you save it a bit of energy doing so. N/A DCS until there's appropriate guidance.

 

IIRC, pitching up enables the loft to begin with. Not applying any launch elevation will have the missile fly in a simple PN fashion. At least that's how it works for the AIM-7.

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I believe that it depends on the on-board software, even for the 7. I've read (or maybe misinterpreted? :D ) at least a couple of versions of 'how to loft' the 7. The 120 has a TTG counter deciding if it will loft or not as one of the parameters - it may or may not have more. :)

 

IIRC, pitching up enables the loft to begin with. Not applying any launch elevation will have the missile fly in a simple PN fashion. At least that's how it works for the AIM-7.

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I believe that it depends on the on-board software, even for the 7. I've read (or maybe misinterpreted? :D ) at least a couple of versions of 'how to loft' the 7. The 120 has a TTG counter deciding if it will loft or not as one of the parameters - it may or may not have more. :)

 

The 120 also, most likely, goes off RTR. As in whether the target is inside or not. No point in lofting below RTR, really.

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Last I checked in the -34 it was ttg and the ttg was suspiciously close to the rocket burn time :D

 

TTG is the most likely determinate of wether the missile lofts or not. High loft energy management ascent profiles can lead to a miss due time to climb, especially in a tail chase scenario.

 

http://ac.els-cdn.com/S2405896316301197/1-s2.0-S2405896316301197-main.pdf?_tid=ad09ee42-6fec-11e7-b48d-00000aacb35d&acdnat=1500844976_b7e03651cbf08601fa7a225b3c6a8320

 

It seems like the DCS missiles only have two guidance phases at the moment, boost and terminal. Some midcourse guidance laws designed to manage energy would probably lead to more realistic results. Solutions are publicly available ranging in complexity from keeping the missile flying at L/D max

To something more complex like optimal control theory or even more intricate like Singular Perturbation. The missile probably should only go P/N with in the seeker range in the terminal phase.

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The 7g limit was used for testing loft. When ED introduces better guidance, this sort of limit will be temporary for the duration of the loft only. So I hope :)

 

Are we expected to believe that that will happen in the foreseeable future?

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Ideally, but the time/cost of such an exercise is pretty massive for something like this. Also you have to consider the limitations in the game engine, making such an exercise likely pointless. It'd would help justify the g-limit, but beyond that you wouldn't get much out of it.

This tests should be conducted just to get drag force rule for specific missile or plane. Calculations of this kind could be done in matter of less than 2 weeks in moderate(adaptive) mesh resolution. Once AoA[deg] vs Drag[F] chart is complete the rest is on coders. Noo need for realtime calculations because they all would look very similar. Missile flight envelope looks like this: drop-burn-glide-manouver-(hit or die) and physics looks like this: accelerate max speed (burn time, drag from normal pylon hinged to max free flight)-0deg AoA(standard straight drag force slowly depletes energy)-max G/AoA (drag force on maxG/AoA max energy loss) per time segment-until all maneuverable energy lost - ballistic. So in general we have initial velocity vs drag force per altitude/air density combined with drag increment by AoA in specific turn under 1G global vectored field. Its very simple but most important data can be gained by CFD or expensive wind tunnel data. Tunnel is for professionals, no need for that. Just extract drag force chart and make that work on everything that flies.

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Are we expected to believe that that will happen in the foreseeable future?

 

I guess we'll just have to use them against bombers and cruise missiles only. How will we be able to tell which is which, is another topic ;)

Modules: FC3, Mirage 2000C, Harrier AV-8B NA, F-5, AJS-37 Viggen, F-14B, F-14A, Combined Arms, F/A-18C, F-16C, MiG-19P, F-86, MiG-15, FW-190A, Spitfire Mk IX, UH-1 Huey, Su-25, P-51PD, Caucasus map, Nevada map, Persian Gulf map, Marianas map, Syria Map, Super Carrier, Sinai map, Mosquito, P-51, AH-64 Apache

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Are we expected to believe that that will happen in the foreseeable future?

 

one of the most important questions in DCS

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rest is on coders.

 

This is where the problem comes in. The coders can't do anything as it's all DCS engine hardcode. It's pointless doing 2 weeks of high cost work that then cannot be used.

 

Whilst I would love to have the drag force for different AoA's at different airspeeds at different altitudes, the fact remains that from a third party dev's perspective, the most they can change is the max Cl at <M1 and max Cl at >M4, the game engine calculates the rest.

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I guess we'll just have to use them against bombers and cruise missiles only. How will we be able to tell which is which, is another topic ;)

 

I wouldn't jump to conclusions. I've tested the current DCS AIM-54 against fighter targets and it rarely pulls many G during the intercept, even with direct hits when the fighter is maneuvering hard.

 

The energy retention may have some advantages anyway. I also have faith that Heatblur will test this thoroughly. If it has trouble with fighters due to the G limit, they may decide to relax things a bit. :thumbup:

 

-Nick

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So we have aerodynamics in the ball park, but guidance after launch is simply not there for DCS and is simulated by DCS as if it were guided?

If so, and we have a launch with preset INS and the guiding aircraft turns away, will we have magic guidance from DCS, meaning the missile in DCS will then become much more capable than it could ever be unless the guidance via AWACS is also a synthetic layer of simulation?

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So we have aerodynamics in the ball park, but guidance after launch is simply not there for DCS and is simulated by DCS as if it were guided?

If so, and we have a launch with preset INS and the guiding aircraft turns away, will we have magic guidance from DCS, meaning the missile in DCS will then become much more capable than it could ever be unless the guidance via AWACS is also a synthetic layer of simulation?

 

I don't quite follow what you're asking.

 

The missile follows the same guidance logic as the AIM-120 does in the game, with a slightly modified loft variables to smooth the loft parabola.

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I wouldn't jump to conclusions. I've tested the current DCS AIM-54 against fighter targets and it rarely pulls many G during the intercept, even with direct hits when the fighter is maneuvering hard.

 

The energy retention may have some advantages anyway. I also have faith that Heatblur will test this thoroughly. If it has trouble with fighters due to the G limit, they may decide to relax things a bit. :thumbup:

 

-Nick

 

Don't get me wrong, i intend to fly the F-14 guns only in MP, so for me the 54 won't be an issue. In SP though...... it might. But it won't matter as much, as the AI isn't very good at missile evasion anyways. :thumbup:

 

EDIT: did you check the latest update on FB? It looks awesome!

Modules: FC3, Mirage 2000C, Harrier AV-8B NA, F-5, AJS-37 Viggen, F-14B, F-14A, Combined Arms, F/A-18C, F-16C, MiG-19P, F-86, MiG-15, FW-190A, Spitfire Mk IX, UH-1 Huey, Su-25, P-51PD, Caucasus map, Nevada map, Persian Gulf map, Marianas map, Syria Map, Super Carrier, Sinai map, Mosquito, P-51, AH-64 Apache

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Don't get me wrong, i intend to fly the F-14 guns only in MP, so for me the 54 won't be an issue. In SP though...... it might. But it won't matter as much, as the AI isn't very good at missile evasion anyways. :thumbup:

 

EDIT: did you check the latest update on FB? It looks awesome!

 

Yeah, I saw the FM charts. Super impressive as usual! No doubt the FM is going to be outstanding for this module. A lot of blood, sweat, and tears has gone in to it. :)

 

-Nick

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Yeah, I saw the FM charts. Super impressive as usual! No doubt the FM is going to be outstanding for this module. A lot of blood, sweat, and tears has gone in to it. :)

 

-Nick

 

The -54 better launch at 25000ft -35000ft.:book:

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Yeah, I saw the FM charts. Super impressive as usual! No doubt the FM is going to be outstanding for this module. A lot of blood, sweat, and tears has gone in to it. :)

 

-Nick

 

Yep..HB's really making waves and being super impressive.

 

I'd say probably as near as possible to a maximum fidelity simulator outside of the sims at Oceana..which were dumbed down when released to the public at Pensacola.

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Man, the amount of research going into this simulation is impressive. This is awesome, great stuff!

 

 

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mark my words, half a year later nobody is going to remember this.

 

but when they file their bogus report about how wrong it is that the aim-54 isnt getting them the sure kills they think the history channel promised them, some smartass is going to drag out this paper and point out the guidance deficiencies mentioned within, and half the thread will all of a sudden be in an uproar about the lack of fidelity and how they're mothballing or refunding the module because of it.

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My takeaway from this is under normal DCS conditions, the missile either hits within 30-32 seconds at any normal altitude or it does not hit. I think that makes it the longest ranged air to air missile in DCS.

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mark my words, half a year later nobody is going to remember this.

 

but when they file their bogus report about how wrong it is that the aim-54 isnt getting them the sure kills they think the history channel promised them, some smartass is going to drag out this paper and point out the guidance deficiencies mentioned within, and half the thread will all of a sudden be in an uproar about the lack of fidelity and how they're mothballing or refunding the module because of it.

 

Probably so :(

 

And it's not like the missile issues is a new or obscure one...... :huh:

Modules: FC3, Mirage 2000C, Harrier AV-8B NA, F-5, AJS-37 Viggen, F-14B, F-14A, Combined Arms, F/A-18C, F-16C, MiG-19P, F-86, MiG-15, FW-190A, Spitfire Mk IX, UH-1 Huey, Su-25, P-51PD, Caucasus map, Nevada map, Persian Gulf map, Marianas map, Syria Map, Super Carrier, Sinai map, Mosquito, P-51, AH-64 Apache

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