DCS: F-14 Development Update - AIM-54 Phoenix Improvements & Overhaul - Guided Discussion

[Temetre]

Tbf I dont want to downplay what you are saying, or the work you did at this stuff. Mainly its to note that there is a ton of open questions.

Frankly, I got more questions than I got answers looking at what you wrote and this stuff. But thats sometimes just how it goes  

Edited July 1, 2023 by Temetre

[tavarish palkovnik]

My fault, I didn’t write nothing to explain all these numbers. First two pages is about booster phase of R-33 just to show that specific impulse surely can in line of 270s and more at sea level. It is here mainly about chamber pressure which in correlation with all other makes specific impulse as it is. So in first 5 seconds 100kg of fuel burn out making total impulse of 264,5 kN. Geometry of fuel block follows everything, all characteristics of fuel and geometrical features are very realistic. Exit pressure at nozzle at sea level almost near to ambient pressure, ideal expansion.

Next two pages is what could/should be in AIM-54 motor to result with total impulse as in document stated, in sea level conditions. Pressure in chamber should be around 50bar (ok), burning rate should be around 6mm/s (ok), area ratio should be around 17,5 (ok although at sea level lower ratio would  be more beneficial), burning surface should be around 0,668 square meters (achievable ultimately) etc etc.

Only what is problematic to accept, fuel composition should be some with ratio of specific heats 1,1. Most of composite fuels graded (dual based with metals as well) are with ratio 1,15-1,2 (for only one composition I have data where ratio is 1,13). This result (aimed total impulse) somehow looking for 1,1. Also one more unique characteristic, if thrust is nearly continuous makes this motor as only one I know that is so much overexpanded at sea level. All others have pressure at nozzle exit somewhere near to 1 bar down there and this one is just like constructor wanted all to predefine for altitudes 

[Machalot]

1 hour ago, tavarish palkovnik said:

if thrust is nearly continuous makes this motor as only one I know that is so much overexpanded at sea level.

Wouldn't you expect the nozzle to be optimized for high altitudes?  Probably higher than any other tactical missile.  It should be greatly over-expanded at sea level. 

Edited July 1, 2023 by Machalot

[tavarish palkovnik]

Probably from same reason mentioned, loose of wider view what sides in that time considered as main threats. While one side found cruise missiles as potentially the highest threat that time, other perhaps thought focus should remain at slow flying bombers at high altitudes.

Now we can see that drones making hells and everything in counter-measuring is turned upside down 

[Machalot]

For a long range missile that flies a lofted profile, the rocket nozzle optimization doesn't care about the target altitude, only the missile altitude while the motor is burning. The Phoenix climbs during the motor burn and for some time after burnout, and with its long burn profile it probably has the highest burnout altitude of any tactical missile. 

[tavarish palkovnik]

And then for cruise missile after time lost for climbing it should goes down, it will still loose lot of energy going through the atmosphere plus velocity vector will not be so productive. I will always say punch in nose directly is more efficient, like in problematic pubs, there shouldn’t be too much talks but punch first and then talks if necessary 

[near_blind]

What altitude bands do the Kh-20, Kh-22 and KSR-5 travel in again?

[DSplayer]

On 6/29/2023 at 5:38 AM, tavarish palkovnik said:

 

Does anybody have this document in complete form? This motor will make me crazy 

Total impulse 97000 lb*s or 431477 Ns together with 376 lbs or 170,5kg of fuel (if all this will be taken as fuel weight because some small part should be igniter, ablative isolation etc) makes specific impulse of 258s. It is huge and it doesn't have any sense.

That screenshot is from the "An Outsider’s View Of The Phoenix/AWG-9 Weapon System" thesis paper. While I trust the document, it was written utilizing publicly available sources at the time (such as OSINT publishes like Janes) and mixing them in with actual specifications with the intention of being vague. This document was actually one of the documents used to create the original AIM-54 motor simulation before it was changed last year. I do have a copy of that document but I will say it will not help you in trying to get a clearer picture of the AIM-54's motor section.

[tavarish palkovnik]

@DSplayer Thanks for clarification !

Still I will continue with trying, I believe these numbers should be true, or not too much far from true. 

Here is one more document, not so much but at least wall thickness gives some direction what could be pressure range in chamber

  

 

[tavarish palkovnik]

New attempt, that from yesterday about AIM-54 is not realistic simply because fuels with such adiabatic coefficients (k=1,1) are not in practice available, especially if we are talking about CTPB  

 

 

 

This here is very achievable, these characteristics of fuel are just normal for that time and what ever some will think, there is no much difference between all these grades, either of US and Russian origin, either used in air-to-air missiles or surface-to-air missiles all away to just regular artillery rockets filled with composite. Burning rate is also very common, geometry of nozzle together with chamber pressure is in order. Continuous burning surface of 0,716 sq.m with some geometrical features is achievable indeed. And it would fit very easily to 97000 lbs*s and 4000 lbs but only with additional note that values are for let's say 40000 ft

 

 

This is rough scaled sectional view, it fits to 170kg and with some simple features continuous burning surface can be achieved. Unfortunately photo of cross cut model in better quality I haven't managed to get, author even didn't find time to answer, or good will. 

In table you can see what kind of specific impulse such overexpanded nozzle will give at sea level. This 209s should not be surprising, simply the laws are that way. I know you in this game have fixed 7%, but as you can see it depends and can vary a lot. Of course it is not easy to make in other way, it is possible but it would take a huge time of work.

 

Just one more document related to all these for eventual ones with skepticism 

 

 

 

This is similar diagram like previously given for vacuum conditions and for variety of fuels, this one is for dual based propellants (k=1,2 - 1,3) and for atmospheric pressure. You can see what is happening with overexpanded nozzle with ratio 15 and similar when pressure ratio is 33,3:1 or 50:1. Thrust coefficients drop down so much so Isp and Ct in upper calculations should not be surprising

I will not bother you anymore with this, think that I got answers I was looking for and that will be enough for me

[draconus]

Looks like good proof that it's a high alt missile and it sucks down low

[tavarish palkovnik]

13 hours ago, draconus said:

and it sucks down low

Indeed it sucks down low, and reading what you have in game with 7% practise of uniformity, seems that you have Mk47 down low in realistic numbers but significantly underrated up there, while Mk60 is opposite, up there seems correct but down low highly overrated.

This motor is different and 7% practice surely is not good way to have realistic kinematic.

Sample AIM-9D is sample which shows that 7% is more or less acceptable, however only for it and motors of similar internal ballistic 

 

  

 

[tavarish palkovnik]

I promissed not to bother anymore  but I have to 

Son of a bi..., this motor or these motors will make me crazy, but really

 

 

This is sectional view of nozzle and blast tube of AIM-54 and in same document this table

 

  

 

I was close with estimation of throat diameter, it is a bit smaller (55mm) and exit is a bit wider (238mm), so area ratio is quite bigger than from my estimation (18,5 vs 14,7). But WTF these average thrust values are now, 1000 lbf to 5000 lbf (4448 N to 22241 N)  Based on this, it can't be considered as single thrust motor, isn't it

 

[tavarish palkovnik]

So, after this of today, I’m again very much back to what was my thoughts at very first beginning. Cross cut model’s blurred photo and this data are so much related, simply that on photo “ignited” is giving such values, more or less.

Perhaps Mk47 and Mk60 are not even close in principles except having similar total thrust 

 

 

Quickly made output of already studied fuel block model, now with changed nozzle’s data according to document and with slightly reduced burning law compared to one used few months ago ( 2,2*p^0,25 ). These are sea level and 10km values and as previously with not including nozzle throat erosion.

Mates, I think dual thrust mode at least for one of these motors must be considered as reality what ever Internet says, there is more than one sign pushing in that direction 

[Despayre]

2 hours ago, tavarish palkovnik said:

So, after this of today, I’m again very much back to what was my thoughts at very first beginning. Cross cut model’s blurred photo and this data are so much related, simply that on photo “ignited” is giving such values, more or less.

Perhaps Mk47 and Mk60 are not even close in principles except having similar total thrust 

 

 

Quickly made output of already studied fuel block model, now with changed nozzle’s data according to document and with slightly reduced burning law compared to one used few months ago ( 2,2*p^0,25 ). These are sea level and 10km values and as previously with not including nozzle throat erosion.

Mates, I think dual thrust mode at least for one of these motors must be considered as reality what ever Internet says, there is more than one sign pushing in that direction 

If the missile performance is close (and getting even closer all the time) to what SME's say the actual missile was like... what difference does it make to the sim whether the missile is single or dual thrust as long as it acts like it is supposed to?

[GGTharos]

Because the performance won't be the same.  Dual thrust has very different behavior in specific cases, and also top speed tends to be lower.  Look at sparrow for example.

[Oberst Struppi]

Regarding Phoenix and flying BVR engagements i´ve been wondering for the past 2 years and asking myself -> WHY DO WE HAVE A DATALINK WHICH IS LIMITED TO SHOW A MAX AMOUNT OF 8 CONTACTS?

During Mike "Nasty" Manazir´s Q&A Session done by "Aircrew Interview" on Youtube i had the opportunity to ask Mike directly.
He just answered that this limitation is just a DCS thing.

Anyone here wo knows more about this? 

Maybe i can direct my question right to the developers of HB.

[Naquaii]

55 minutes ago, Oberst Struppi said:

Regarding Phoenix and flying BVR engagements i´ve been wondering for the past 2 years and asking myself -> WHY DO WE HAVE A DATALINK WHICH IS LIMITED TO SHOW A MAX AMOUNT OF 8 CONTACTS?

During Mike "Nasty" Manazir´s Q&A Session done by "Aircrew Interview" on Youtube i had the opportunity to ask Mike directly.
He just answered that this limitation is just a DCS thing.

Anyone here wo knows more about this? 

Maybe i can direct my question right to the developers of HB.

All information and manuals we have about Link 4A all say 8 tracks was the limitation for how many tracks the AWACS or ship could send to the aircraft. You have to remember that Link 4A was first introduced over 50 years ago.

So afaik this is correct and not a DCS limitation. I'd say it's likely he's confusing it with Link 16 that had no such limitation, afaik he did fly the F-14D and that had Link 16.

Edited July 4, 2023 by Naquaii

[Despayre]

4 hours ago, GGTharos said:

Because the performance won't be the same.  Dual thrust has very different behavior in specific cases, and also top speed tends to be lower.  Look at sparrow for example.

You may have missed the last half of my question... "as long as it acts like it is supposed to"... do you have any reason to believe they are not reasonably accurate?

[GGTharos]

1 hour ago, Despayre said:

You may have missed the last half of my question... "as long as it acts like it is supposed to"... do you have any reason to believe they are not reasonably accurate?

I didn't.  It won't behave correctly if the rocket motors are vastly different.  Some particular trajectories may end up being more or less a match, but most won't.

[tavarish palkovnik]

As @GGTharos explained, single and dual thrust concepts (with same total impulse) will result with different ballistics. It is of course individually what is acceptable and accurate enough, for my taste, it is significant difference

Imaginary case of AIM-54 flying horizontally at 10km, values of Mach number and travel in meters while total impuls is same (26000N*11s+10000N*14s=426000Ns=17040N*25s)

 

 

Edited July 12, 2023 by tavarish palkovnik

[Karon]

These are the AIM-7s in game at the moment.

And this is a broader comparison of some missiles from the 70s

You can see right away how the AIM-7 behaves very differently.

[tavarish palkovnik]

This AIM-7E should go on serious reconstruction and overhaul. Mk38 Mod 0,1,2 as well as Mod 3 and later should give much more speed than presented 

[tavarish palkovnik]

Although this topic is not related to Sparrow, just to ask about this AIM-7E-2 because based on this graph it seems so wrong. AIM-7E2 should be very much related to Skyflash isn't it? If I'm not wrong, both are equipped either with motor type Mk52 or motor Mk38 Mod.4 

@Karon what motor is behind this graph?

Motors of Sparrow 7E family can be divided in three groups:

Mk38 Mod.0, 1 and 2

Mk38 Mod.3 and 4

Mk52

and between some of these groups difference is significant. If there will be interest we could shortly go through these motors, although all looks same from outside, inside they are very different, especially these Mods 0, 1 and 2 compared to others   

[GGTharos]

Mk38 and 52 is 2.9s ~8000lbf.  They're made by different producers as was required in order to protect production against one producer having problems etc.