DB request: Revise AAW missile max/avg speeds at lower altitudes

[amizaur]

MOD: Continuation of discussion from here: https://forums.matrixgames.com/viewtopic.php?p=5266605
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Well, I would personally disagree with that 475kts (mere 0.72M, and should be around 1.5M) but it's a game design decision.

If you are interested in some real world data regarding to AIM-9L/M performance, here is is:

AIM-9L performance compared to some project.jpg (97.17 KiB) Viewed 164 times

This is real world test data of standard AIM-9L Sidewinder compared to some experimental variant of it (with different nosecone). As you can see when launched at sea level, platform speed M0.9 (around 975ft/s, 577kts) AIM-9L accelerates to around 2700ft/s which is 823m/s, 1599kts, Mach 2.5.

Speed gain due to motor action is 1599-577=1022kts = ~Mach 1.6. Launched from stationary helo (or a ground launcher like Chapparal) it should reach a higher speed than 1022kts, as it would be less affected by drag when accelerating.
Rough calculations of missile/fuel mass and motor data with some ballistic software give results of a bit over Mach 2 for stationary launch at sea level (and almost Mach 2.5 theoretically without any air drag).

A Chapparal MIM-9 missiles are usually credited with at least Mach 1.5 speed (sometimes as Mach 2.5 but it's probably wrong number taken from air-launched AIM-9 data).

Reading from the graph again, max speed of AIM-9L launched at alt of 20kft at 0.9M is about 3200ft/s = 975m/s = 1895kts = 3.07M. This means delta V of 658m/s = ~2M = 1278kts. At 30-40ktf altitude speed would be even bit higher, bit closer to theoretical no-drag value.

The other very interesting thing in those graphs are the velocity profiles, which may be used to asses how realistic DLZ calculations are.

In second .7z attachement is same graph plus AIM-9L motor data and example real life DLZ data (10kft 0.9M) for AIM-9L.

[amizaur]

Two more graphs - CMO AIM-9L performance measured some time ago, after AirDrag for missiles was introduced, but before Variable Burnout Velocity.

In-game AIM-9L sea level performance compared to RL test data.jpg (34.89 KiB) Viewed 153 times

In-game AIM-9L 20kft performance compared to RL test data.jpg (37.17 KiB) Viewed 153 times

Performance of AIM-9L then was 983kts max speed at 200ft and 1185kts at 20kft.

I measured this as I wanted to raport poor AIM-9L/M performance at low altitudes, (in fact poor performance of all short range IR AAMs), but I didn't raport due to lack of time.
This low initial velocity - further decrasing due to drag - caused VERY low usefull range of AIM-9L/M or R-73 near sea level (for example when hunting cruise missiles), in order of ~3nm head-on to reliably hit, and almost non-existant in pursuit.

The problem is caused by the missile artificial speed limit at the lower altitude bands.
This max velocity limit was ment to reduce missile range and performance at low altitudes long ago, when the velocity was constant and the range depended only on flight time.
As can be seen in the graphs, the velocity retention of in-game Sidewinders is even better than in RL (the simulated drag is lower), but the low initial speed causes abysmal performance, especially in pursuit.

Now, as the missiles quite-realistically slow down due to air drag, those artificial limits are just not needed, the beta version could use just the velocity of highest altitude band for all calculations, and range reduction on low altitudes would came naturally from quick velocity loss due to drag. Some drag values might need tweaking but that's natural, it will came cradually as DB fine-tuning always was.

As for now (beta) the performance at low alt is effectively reduced TWICE - first by reduced max velocity, next further by high air drag and rapid decceleration at low altitudes.

I hope you plan to remodel all A2A missiles one day to a single-standard (short 5-10s burn and coast in nearly all cases (with exception for ram-jet weapons and VERY FEW medium burn-time weapons like some AIM-54 variants). And that you plan to improve ram-jet modeling and introduce multiple-pulse rocket motors - as it's impossible to simulate realistic performance of most modern missiles like PAC-3MSE, AIM-260 or PL-15 without that. Simulating them as very long burning rocket motors (as now in some cases - like R-33 for example) would result in very unrealistic DLZ and NEZ calculations. Please compare two versions of the same missile - R-33 vs R-33S, they are modelled in two very different ways resulting in drastically different DLZ / NEZ performance. Same for different variants of AIM-54 , R-77, AIM-120. Some are setup as short-burn, some "long burn". It gave similar max range in older game versions (with constant missile velocity) but gives drastically different results after introduction of air drag, especially in low2high and high2low scenarios.

Regards !