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Old 10-03-2014, 07:33 PM   #1
IASGATG
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Default DCS Missiles Mod

Version 1.2 now released

Change Log

Lift curves altered for all missiles.
Loft calculation has been adjusted, no needless high g bullshit.

https://mega.nz/#!NtwxFRoS!G7VYdiV-o...vgnkWhJ6WbQkMc


As some of you are aware by now, research has been done into the AIM-120C in an attempt to provide a more realistic flight model and gain greater understanding as to how this and other missiles behave.

Essentially two major areas that need to be assessed. Firstly is the Cd curve which means to be adjusted to fall in line with realistic expectations of performance. Secondly is the thrust and motor behaviour of the missile. Fortunately the motor information is rather easy to gain access to (Apart from the R-77 but we'll talk about that later).

As the Cd curves of the missiles are likely to be similar due to the general shape of the missile, we have made alterations from the AIM-9Variant curve and the AIM-120C curve generated through CFD. Obviously slightly more drag for the larger missiles and slightly less drag at certain envelopes for special circumstances (R-77's gridfins come to mind).

The motors have all been taken from real world sources and adjusted accordingly in game. There are certain variables that are not factored which have a large impact (Reduced drag whilst the motor is running for example) which obviously cannot be included. This gives the missiles their distinct flight characteristics. The exception to this is the R-77 where I have been able to find no legitimate sources on beyond what is currently accepted doctrine on the Russian part of the ED forums and is currently already in the game.

Where the big differences start to show are the surface area, diameter and overall mass of the missiles which impact each missile uniquely in combination with their very different rocket motors.

All in all I feel as though this is the closest approximation that we're able to generate short of CADing and CFDing every missile in the game which is unrealistic on a budget of $0.

Missiles effected: AIM-120C, AIM-120B, AIM-7M, R-77, R-27ER, R-27ET, R-27R, R-27T

EDIT: Rationale below


AIM-9M performance

The Performance Improvements With Sidewinder Missile Air-frame Variants document provides the most useful and detailed source for the flight performance of the Sidewinder. Below are graphs taken directly from the paper.







The AIM-9M was then shot in the game and compared to digitized versions of these graphs, as seen below with accompanied Cd variables and curve.

0.04 , -- Cx_k0
0.08 , -- Cx_k1
0.02 , -- Cx_k2
0.05, -- Cx_k3
1.2 , -- Cx_k4
1.2 ,










The graphs match, sort of. Two big points to note are how the missile doesn't get up to the top speed fast enough and how 10K doesn't seem to fit. The former is due to the lack of motor on reduced drag which is currently not modeled in the game. Below is a graph from the same paper that demonstrates a Cd difference with Motor On/off as well as from A Method Of Increasing The Kinematic Boundary Of Air-To-Air Missiles Using An Optimal Control Approach, both clearly showing a reduction of 10-20% in parasitic drag whilst the engine is running. This obviously varies with altitude but at current nothing is modeled in the game.





The latter point about 10k being out of a recurring theme that will be seen time and again later on and appears to be an artifact within the game.

The second curve in the graphs labelled as variant is testing the USAF did whilst developing the AMRAAM. It was to see what the flight performance of a missile with similar shape radome and fins would have. Whilst the variant doesn't fit the AMRAAM perfectly (picture below) it does have matching nose and fore fins to the AIM-120A and much reduced tail canards compared to the AIM-9L which was modified. Below are the graphs of the Cd curve designed to match the flight performance of these flyout shots along with the ingame comparisons.

0.022 , -- Cx_k0
0.047 , -- Cx_k1
0.02 , -- Cx_k2
0.027, -- Cx_k3
1.5 , -- Cx_k4
1.5 ,












AIM-120C performance

This gives us a reasonable estimation on how the AIM-120 should behave. As has been mentioned around the forum and posted in this thread, there has been CFD work done on the AIM-120C and below are the Cd curves for that and the same three comparison graphs.

0.016 , -- Cx_k0
0.045 , -- Cx_k1
0.02 , -- Cx_k2
0.016, -- Cx_k3
1.2 , -- Cx_k4
1.5










This validates our work as real flyout shots of a comparable missile shape matched our own analysis. Now to complete the AIM-120C would be the motor. The engine in the game is more or less bang on as information we provided months ago filtered down and ended up in the game. With an averaged Cd curve and the motor in the game we are confident and comfortable with the AIM-9M, AIM-120B and AIM-120C being the closest approximations possible with currently available information and resources.

AIM-7M performance


How does this information help with the other missiles, how can it be used further? If we look at the AIM-7E which has a wealth of information regarding we then extrapolated the Cd curve to the Sparrow. Firstly we started with generating a Sparrow Motor, the specifications can be found within the AD-A142-508 (Weapon File) and other sources validate the Weapon File's accuracy. The motor contains 42kg of 240Isp fuel which burns for 2.9s. We used this to modify the AIM-7M in the game.
The Cd curve was then altered to fall in line with what we would expect to see.

0.023 , -- Cx_k0
0.048 , -- Cx_k1
0.02 , -- Cx_k2
0.028, -- Cx_k3
1.5 , -- Cx_k4
1.5



The F-4 Phantom's Tactical Manual provides us DLZ shots for the AIM-7E which our AIM-7E falls within parameter of the curves. As graphs aren't very appropriate for this I have also attached all of the track and tacview files for the shots. This was then cross referenced with the AIM-7F Standard Missile Characteristics which lists a single instance of the AIM-7E and it matches. It should be noted that at the 40k feet shoots the missile potentially has slightly too much energy but as SL up to 25k feet match so well it may be another game artifact.

How does this impact the AIM-7M. Well we have information on the AIM-7F which has the same motor as the AIM-7M. The AIM-7's also have the same missile shape (Except for the Dogfight Sparrows but we wont talk about those). So the Cd curve is still appropriate but the engine now needs to be corrected. The SMC as previously mentioned as well as a number of other source all list the details of the Sparrow's motor. The SMC does have what we believe to be an error when listing the boost/sustain ratio. The missile has an Isp of approximately 265, has 62kg of fuel and the thrust of the two stages is sourced multiple times. This would demonstrate to us that it should be a 70% boost 30% sustain motor. Firing tests also show that this ratio to provide the longest range so that is what we opted for.

We have AIM-7F DLZ's and Rmax benchmarks from the SMC which the AIM-7F/M hits with modified motor and Cd curve.

t_statr t_b t_accel t_march t_inertial t_break t_end
-1.0, -1.0 , 4.5 , 11.0, 0.0, 0.0, 1.0e9,
0.0, 0.0 , 9.8 , 1.73, 0.0, 0.0, 0.0
0.0, 0.0 , 25577.0, 4528.0, 0.0, 0.0, 0.0,

With this validation we feel comfortable with the American missiles in the game. We felt it was unfair to modify the American arsenal and not touch the Russian side of the table so similar curves were applied.

The Russian side of the coin

The access to the Russian information is much harder for us to obtain. There are R-27R and ER DLZ's which have been posted in this thread as well as details on the R-27 family's rocket motor. Whilst we have not sourced it we feel that the rocket motors for the 27 family are accurate and match both the Isp and fuel quantities we would expect to see and what is documented on Russian websites.

There has been a lot of dispute over the DLZ RMax for the R-27ER. When a similar Cd curve is given to the missile the Raero increases dramatically. I am going to copy and paraphrase the response I gave to Chizh regarding my belief as to why that is acceptable from later in the thread here as I feel the argument is still valid as no counter-argument has been given.
I would agree though that if the Raero the missile goes as you say an extra 24km, you would expect that DLZ to be larger as the missile has quite a bit more energy. Not necessarily, but I would agree, it would be strange. What could be a limiting factor though is as I said, the life time of the missile.

The R-27ER DLZ Curve says the Rmax is 66km. If translate this into nmi that comes out to be around 35.5nmi.

If we say that the DLZ is about as far as the missile can go on average as it is a DLZ and an Raero diagram, this would give you the maximum most useful range of the missile (Which you could say gives reasonably good Pk but that's another argument). So there are two limiting factors, how far the missile can fly, and how long the missile can fly for (Not aerodynamically, but due to internal lifetime functions). It's been agreed (Although I cannot source it) that the missile has approximately 60 seconds of life time in it (Battery life from what I hear. Possibly hydraulics in the same way as the AIM-7).

So lets say that missile flies for the max of 60 seconds before the electronics/hydraulics/whatever run out. The target moves at your speed of 1100km/h for 60s = 9nmi. So the missile in 60s has to make up the remaining 26.5nmi. The diagram below of how my missile behaves hits 26nmi at 60s. Aerodynamically, the missile can continue but in it is just drifting now as the fins cannot actuate to generate enough lift.



Missile launched at 10km ASL at 1100kph


Similarly it matches quite closely with the Tail-Chase diagram as well. Looking at the 400m/s at 60s for 10km ASL, both launcher and the target are moving at 400m/s, 10km ASL. The target will move 24km. The missile will move 16km. The missile also has to be doing at least 400m/s to make the intercept. If we translate this into imperial numbers. 400m/s ~ 800kts. The graph below shows that the missile at the 60s is doing just over 800kts, which is required to make the kill. It all fits within the realm of reason.



Missile launched at 10km ASL at 1100kph


This all assumes that the 60 second rule is correct and is factored into the Russian R-27ER DLZ curve. If it isn't then I have I would have to drastically alter the drag curve of the R-27ER to something of similar range to the AIM-7E. Based on the size and shape similarities between the AIM-7 and the R-27 a similar drag curve would be expected. With the much larger motor on the R-27ER a greater range would be expected which is what we see.

The only dark horses are the R-27ET which should probably have a curve that fits the Sidewinder more than the AIM-120/Sparrow due to the rounded seeker head and the R-77 due to it's grid-fin design.

The R-77 was compromised to give it higher drag in the sub-sonic region and much lower drag in the supersonic region which is what would be expected from the grid-fin design.


Bilbliography

AIM-120
General Missile Specifications
Air to Air Intercept Procedures Workbook Naval Air Training Command 2010 Pg: 149
Navy Training System Plan for the AIM-120 Advanced Medium Range Air-to-air Missile 1998 Pg: 13
Distributed Simulation Testing for Weapons System Performance of the FA-18 and AIM-120 AMRAAM, Tom Watson, 1998, Pg: 3
Motor Specification
AMRAAM PEP Propulsion System, www.atk.com, Pg: 2
Hazard of Classification of Unite States Military Explosives ans Munitions Revision 14 2009, Pg: 143
Rocket Propulsion Elements, George P Sutton, 2001, Pg: 492
Aerodynamic Performance
Performance Improvements with Sidewinder Missile Airframe Variants 1979, Pg: 7
A Method Of Increasing The Kinematic Boundary Of Air-To-Air Missiles Using An Optimal Control Approach, Robert D. Broadston, 2000, Pg: 40 

AIM-7E
General Missile Specifications
AD-A142-508 (Weapon File) , 1984, Pg: 9
Rocket Motor Specifications
Shrike and Sparrow Missile Baseline Cookoff Tests, Anthony San Miguel, et all, 1974 Pg: 46
Hazard of Classification of Unite States Military Explosives ans Munitions Revision 14 2009 Pg: 44
Rocket Propulsion Elements, George P Sutton, 2001, Pg: 492
Aerodynamic Performance
F-4 Tactical Manual, 1972, Pg: 223
AIM-7F Standard Missile Characteristics, 1977, Pg: 2

AIM-7F/AIM-7M
General Missile Specifications
AD-A142-508 (Weapon File) , 1984, Pg: 10
Air to Air Intercept Procedures, 2010, Pg: 146
Rocket Motor Specifications
AIM-7F Standard Missile Characteristics, 1977, Pg: 2
Sparrow Propulsion System, ATK, Pg: 2
Hazard of Classification of Unite States Military Explosives ans Munitions Revision 14, 2009, Pg: 143
Rocket Propulsion Elements, George P Sutton, 2001, Pg: 492
Study of the deposition of ammonium perchlorate following the static firing of MK-58 rocket motors, 2008, Pg: 19
Aerodynamic Performance
AIM-7F Standard Missile Characteristics, 1977, Pg: 2 
AAM-6 Sparrow III SMC, 1960, Pg: 5


AIM-9M
General Missile Specifications
AIM-9L Standard Missile Characteristics 1974, Pg: 2
Performance Improvements with Sidewinder Missile Airframe Variants 1979, Pg: 2
AD-A142-508 (Weapon File) , 1984, Pg: 12
Rocket Motor Specifications
Sidewinder Propulsion System, ATK, Pg: 2
Performance Improvements with Sidewinder Missile Airframe Variants 1979, Pg: 7
Hazard of Classification of Unite States Military Explosives ans Munitions Revision 14, 2009, Pg: 143
Rocket Propulsion Elements, George P Sutton, 2001, Pg: 492
Aerodynamic Performance
Performance Improvements with Sidewinder Missile Airframe Variants 1979, Pg: 7
AIM-9L Standard Missile Characteristics 1974, Pg: 2
Attached Files
File Type: zip Replay Shots.zip (1.15 MB, 1014 views)

Last edited by IASGATG; 03-05-2016 at 09:58 PM.
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Old 10-03-2014, 09:18 PM   #2
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Holy crap, nice job! Testing it now!
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Old 10-03-2014, 09:38 PM   #3
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this mod will be blocked immediately by the integrity check, just saying
so you will able to use it only in singleplayer missions or in multiplayer only if both the server and clients using this (exactly the same) mod as well
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Old 10-03-2014, 09:42 PM   #4
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Quote:
Originally Posted by NRG-Vampire View Post
this mod will be blocked immediately by the integrity check, just saying
so you will able to use it only in singleplayer missions or in multiplayer only if both the server and clients using this (exactly the same) mod as well
Only testing in single player
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Old 10-03-2014, 09:50 PM   #5
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I tested this live with IASGATG a few weeks back (we set up a private server), it's pretty incredible to see what the accurate modeling is like. Find a friend and set up a server and hop into a private TS, fire a Slammer off at 30-35nm and prepare to have your mind blown.

Again, very impressive work IASGATG.
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Old 10-03-2014, 09:56 PM   #6
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I don't know enough about air-to-air stuff to be super-annoyed by the current missile state, but even so I think you're doing the community a huge service. Thanks.
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Old 10-03-2014, 10:28 PM   #7
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Thank you for the effort. Installing now and loading up the R-series.
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Old 10-03-2014, 10:36 PM   #8
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IASGATG, are you planning on posting the Range vs Time and Velocity vs Time plots at 0/5/10KM MSL? Just wondering, because I think that would be better suited for a tactics development thread after people get a feel for what the missiles really do. The whole "reshaping the sword" changing how people fight eachother thing.
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Old 10-03-2014, 10:41 PM   #9
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Just got done fooling around with it and wow, what a world of difference these changes make. If we could only now get their trajectory systems updated that would be fantastic. Either way, nice job, I hope ED will look at this more deeply as you have done. Can't wait to see the publications for these changes you have made once it is out
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Old 10-03-2014, 10:44 PM   #10
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This one time, at band camp, 104th started hosting their server with some legit missiles and explicit instructions to download the mod...
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