The AIM-54 Phoenix missile - Technology, History and Performance

[MythicPi]

@DirectSupport

My problem with this theory is that it’s based upon the assumption that the AIM-54 should obtain the best lofting profile possible with no possibility that the IRL counterpart may have had inefficient lofting profiles.

First problem with this statement is that the loft code provided by Dark_Claw is not necessarily “optimal” it is simply an improvement over the current loft code, just like the current AIM-54 loft code was an improvement over the OLD AIM-54 loft code, which was also tested by Dark_Claw:

Spoiler

Old loft code:

Current in-game loft code:

Secondly, there is no way the AIM-54 is achieving an altitude of 103 500ft needed to achieve this known shot using the current in-game loft code:

So at the very least, we can tell its not lofting enough.

Thirdly, the inefficiencies you speak of are likely more due to hardware limitations of missiles control sections, along with chosen guidance method. As tripod stated, there are more complex guidance controllers that can be used than simple PID controllers, with some modern missiles like the IRIS-T using H-infinity controllers because they are vastly more adaptable and applicable to the complex environment of an aerial intercept, but their complexity and limitation of hardware prevented it from being used until the early 2000’s for examples. There’s also the fact that gaijin does not model issues such as inefficiencies, and systems in-game are generally modelled under the assumption of ideal capabilities.

@DirectSupport

Otherwise optimum lofting codes + energy management applied to all ARHs would leave Gaijin little to no space for improvement in guidance for later missiles.

Gaijin is already playing with the loft profiles of the modern ARH along with many ground attack munitions, and all ARH’s have energy management code EXCEPT the AIM-54C. As do the R-23R, R24R, AIM-7F, AIM-7M, R-27R, R-27ER, and Super 530D. The AIM-54’s are the outliers in WT, I’m asking for them to be brought to the standards of the norm.

Your entire argument holds no water “we have no idea about any guidance control criteria’s for AIM-54 beyond the fact that we know it lofts, and has been known to achieve incredible heights during said lofting under certain criteria’s, therefore, I don’t want to see its loft profile improved even if it is changed to more closely reflect what is most likely the more realistic of 2 options”. That “justification” if it can even be called that boils down to “I don’t know and I don’t want it to be better” its childish.

Your arguments moments before that was that the loft profile change “won’t yield game impact differences unless much bigger maps is advocated for that would allow the F-14 to stretch its legs”

Spoiler

So you did a full 180 from “nah, a change to the loft profile wouldn’t change anything” to “no I don’t want the loft profile improved because I don’t think it should be”, simply from evidence coming to light that improvement to the loft code would in fact have a positive impact on the missile in the current state of the game.

Finally, to throw you a bone about the “inefficiencies in guidance”, the improved loft profile still didn’t include energy management code. It only changed 3 values of the loft code specifically, so it could very much still be refined some more, therefore fitting your idea that, for whatever reason, the AIM-54 deserves to be arbitrarily less efficient in its flight profile than all other radar missiles above 11.3 “just cuz”.

[DirectSupport]

@MythicPi

Secondly, there is no way the AIM-54 is achieving an altitude of 103 500ft needed to achieve this known shot using the current in-game loft code:

^^I can do custom testing and report this formally sometime this week if you can give me the source^^, NVM, the radar render range would limit me from making that shot. But Gaijin will need to implement the drag reduction in order for it to properly hit 100k feet in altitude and still have some meaningful velocity.

@MythicPi

So you did a full 180 from “nah, a change to the loft profile wouldn’t change anything” to “no I don’t want the loft profile improved because I don’t think it should be”

Kinda butchered my statements there. The first quote isn’t what I said. I said that a change to the loft profile would not meaningfully affect the AIM-54 unless it is paired with much larger maps arriving into the game. Larger maps would be a nerf to MRAAMs and a buff to AIM-54. Not sure why you would think I’m against AIM-54 buffs if I advocate for changes that would in effect benefit the missile to the detriment of other missiles.

The other conclusion I made was that a drag reduction would benefit the AIM-54 more than a loft profile change.

Perhaps some of the logic I used was faulty, but the end conclusions were correct.

[DirectSupport]

@MythicPi

Secondly, there is no way the AIM-54 is achieving an altitude of 103 500ft needed to achieve this known shot using the current in-game loft code:

Also, quick question, since the radar render range is much less than 110nm, how do you conclusively decide that the missile cannot achieve this climb? You could not have tested this.

[DirectSupport]

Testing:
F-14: 44,000 feet Mach 1.5
AI Target: 50,000 feet Mach 1.5
Launch range: 110 nautical miles or 203km
Missile climbs 59,500 feet

Currently it is nearly impossible to make an AI target travel at 50,000 feet and Mach 1.5, I’ve tried this in custom missions, it results in them tumbling out of the sky.

The other problem is that the render ranges is set to somewhere around 105km for the radar.

How did you conclude that the missile does not loft enough?

[_ShadowFang]

Nvm, I didn’t read well enough.

It climbed 59,500ft or its peak altitude was 59,500?

[legocubed]

One of the conclusions that I came to after the tests pictured here + some others afterwards is that TargetOmegaMax more or less determines how gradual the pitch down maneuver is at the top of the loft. With a low TargetOmegaMax as found on Phoenix the curve is so gradual that changes in climb/dive angles makes little difference in the overall loft shape, as seen in the screenshots pictured. Increasing TargetOmegaMax made a much more noticeable impact on time to target and impact velocity, even when keeping the climb and dive angles the same.

For reference, 0.25 is the value currently used for Phoenix and in the tests pictured in the reply above, and 0.75 is whats used for AIM-120A, R-77 and MICA EM. Climb and dive angles were left unchanged from how Phoenix is implemented currently (15.5 and -7.75 degrees respectively). Combining both a steeper climb/dive angle and a higher TargetOmegaMax (for example, matching that of AIM-120A) would result in an even larger improvement in overall performance.

[MythicPi]

I’ll correct my statement on that point, I highly doubt the AIM-54C would manage to climb to 103500ft on a 15° loft angle, particularly when restricted like it is by the other loft parameters from the in-game code, but I have no proof to argue that point with.

[MythicPi]

So a change from 0.25 to 0.75 for loftTargetOmegaMax without changing any other code increased impact velocity of your test by ~19.6% and a decrease in time to target of around 3% (2.7 sec) on a 6km alt launch at M1.03, out to 80km, and thats without changing the loft target elevation or the loft elevation.

Meanwhile, the test I posted above from Dark_Claw used:

Its almost as if like I had mentioned, an improved loft code improves missile performance at impact…

[SE_8749236]

You also need to work on terminology. You need to define what maximum effective range is, since obviously the “maximum effective” in your vocabulary does not match with other’s interpretation: maximum launch range at which missile can pull meaningful Gees to keep up with target that only defends at last minute (e.g. Aim-54 currently in game has maximum effective of around 38km against a co-altitude Mach 1 target, with improved loft code by Dark_Claw, maximum effective range increases to 75km)

[_ShadowFang]

No one is debating whether or not having a different loft will affect a missile’s performance, this has been established already. The issue with the Pheonix has less to do with the loft and more to do with drag, if I am understanding the issue correctly. This impacts range and performance metrics quite a bit more than adjusting the loft profile.

[SE_8749236]

@MiG_23M

Testing by others doesn’t show such a large improvement in performance with slightly higher loft angles

I understand, but not everyone agrees.

Right now I see two arguments.

1. Aim-54 has too much drag thus it can’t hit long range targets.
2. Aim-54’s lofting is bad and that’s what causing it to have shorter range.

I’ve seen test result by Dark_Claw proving Aim-54 can have dramagic range improvement by simply adjusting loft code.
The counter arguments I’ve seen are “loft doesn’t do that, since other tests that didn’t have the same change has different results”, and “this is separate from excessive drag, both problem exists at same time”.

[DirectSupport]

In the document, the missile climbed 59,500 feet for a target that was 200km away. I did some testing with the Phoenix just now. I’m not able to replicate the testing in the document due to some game engine limitations, so I did it on a smaller scale. Here’s the testing done:

Target: 8,000 meters Mach 1.5
My aircraft: 6,000 meters Mach 1.3

Launch range: 110km

Phoenix climb: 6,500 meters or 21,000 feet.

It seems to me to be performing as expected in line with the source. At 110km, it would climb roughly nearly 7km. In the 203km range, it should climb 17km to maintain the same 17.5 degree angle to the target. I suspect this would be possible for the missile to do with the current loft code.

[legocubed]

I was just attempting the 110nmi shot myself, but I have yet to figure out a good way of finding the altitude of a missile in the replay. How have you gone about this?

[SE_8749236]

The shape of trajectory is very important too. Given that missile flies about 30km when burn ends, if target is far enough, when launched at 10,000m, when target is far enough, missile will climb to 10,000 + sin(15) * 30 = ~17,700m.

However, with 15 degree loft, the missile will waste so much time in lower altitude and experiences higher drag, comparing to missile that climbs at 45 degrees and reaches 17,700m as early as possible.
Also from historical footage we know Aim-54 climbs very aggressively.

[DirectSupport]

110nm shot is not possible due to radar render range but a smaller scale trial is possible.

What it took to find the altitude of the missile was that I would launch the missile, record the altitude that the plane was in, follow the missile until it reaches the apex of its climb, then place your camera where the apex of the climb was located. Then record the distance between your position at the apex climb and the distance of your own plane passing beneath you. Your plane’s altitude would also be recorded in the top left. In my case, the plane climbed about 1km, so I added 1km to that distance.

[legocubed]

I see, interesting way of doing things. I really wish Gaijin had given us a missile altitude readout in the sensor view.

In the user missions I created to test missile range, I have no issues with locking targets well outside render range. Granted I had to modify the AWG-9 radar in order to hold a lock above ~180km, but it works.

[MythicPi]

Seems odd gaijin didnt add “altitude” to the missile data card in sensor view…

Also, as stated by SE, its possible whats wrong with the loft is not so much the loftAngle code but the restrictions (loftTargetElevation and loftTargetOmegaMax). We know for a fact that large missiles benefit more from being at high altitudes, due to a mix of reduced drag and increased impulse from the motor due to the reduction in pressure. It is therefore best for a missile using a solid rocket motor to spend as much of its time in flight at a high altitude.

Likely why the correct term for what missiles do is “trajectory shaping” and not “lofting”. Its not as quick to write though.

[DirectSupport]

@legocubed

Granted I had to modify the AWG-9 radar in order to hold a lock above ~180km, but it works.

I never considered this until now, so this is worth a shot.

@MythicPi

Seems odd gaijin didnt add “altitude” to the missile data card in sensor view…

Imo, I think this is worth pestering about to have more tools/info available to bug report with.

[legocubed]

I do wonder if it’s somehow possible to extract missile altitude from the replay file itself. Unfortunately I’m nowhere near knowledgeable enough about the game’s code to even begin figuring that out myself, though someone else may be.

[DirectSupport]

@SE_8749236

The shape of trajectory is very important too.

I think that so long as the the loft reaches the altitude, and that the missile is fast enough to travel 72.5 nautical miles in the test scenario before striking the target, then the modeling of the missile should be good enough.

https://cdn.discordapp.com/attachments/955829235493273680/1222404292812738631/725.png?ex=661617b6&is=6603a2b6&hm=9e4a9335bd4008cfb6b1ffd1f37bf95d93eaa507a42f9d1ca3a3e6468865abe8&