[RESOLVED+FIXED] Effect of launch level on AAM missile range

[Quark73]

I've tried out the effect of launch level on range/speed for AAM. Made a test scenario with two Foxhounds same load-out same doctrine one very high one very low. My assumption was, that the higher launched missile gets significantly further and faster. I learned the altitude has some impact on speed but few on range. In all cases I tested the low plane shot first and hit first.
As I understood the drag on aircraft is simulated by fuel consumption on various levels in DB. Is it possible to make something similar for AAM? I would suggest a simple matrix e.g. high vs high 100 % of max. range & high vs low makes 75 % max range and low vs. high 25% of max. range or similar. The figures are just a rough guess, since I didn't found good rule of thumb quickly.

[Dimitris]

Thanks, we'll definitely take a look.

We do in fact model variable drag at different altitudes (we dynamically calculate air pressure & temperature at any given altitude and coordinate, and base that for the drag calculations), so something else may be going on.

[Quark73]

Tried another setup, now with Eurofighters and AMRAAM with entirely different outcome. The Typhoons didn't attack each other. But both attacked the trailing AWACS. But this time with reasonable behavior, means the high flying one launched from far away while the low flying shot far later with much less speed of missile.
May be the burning time plays a role.

[amizaur]

Hi Quark73!

I tried the Mig-31 scenario.

With the Mig-31 setup, there are IMO two factors causing the unrealistic outcome. The high flying Mig is most likely limited by it's radar range against low-flying one (look-down-shoot-down situation). It simpy can't fire at the low flying Mig at max kinematic range of it's missile, it has to close the range. That's why the high flying one shot much later and was destroyed first.

edit: I loaded the scenario from Blue side and discovered, that the high Mig-31 is in fact NOT radar limited, I was wrong here. The Mig-31 flying at 18000m is DLZ limited (missile kinematics) against low flying target. And you are right, it's really strange that missile range for shot-down scenario is SMALLER than the same missile range for shot-up scenario. It can be only explained by bad missile kinematics modelling with the R-37 having so much "fuel" (burn time) that it's achieving more range by climbing quickly to target altitude and reaching max speed there (and having little drag after burning-out there) than when diving down, which reduces it's max speed, and causes it to rapidly decellerate in dense air after burn-out.
edit2: I noticed now that the AA-13/R-37 doesn't loft, which makes it even worse. Instead of arcing or cruising high and diving at the target at steep angle, frome the very launch at 18000m it makes a shallow 7deg dive at low flying target spending much of it's flight time at medium and low altitudes. This should be corrected, the R-37 certainly is a high-lofting missile, it's the only way it can reach it's reported range.

At the sime time, the low-flying Mig-31 is not radar limited (look-up situation), or only slightly, but also, it is NOT limited much by it's missile range in this extreme shoot-up situation. It's because it's missile R-37 is modelled with almost 2 minutes of engine burn time. Like a ram-jet Meteor or something like that. It means that the missile can keep it's max speed for 110 seconds and only then it starts to "glide" losing speed due to air drag. The missile as modelled, even fired from low alt in dense air has lots of time to climb up and speed up to it's max before it's "engine burns out", so it's range in shoot-up situation is not limited as much as it should.
Try to fire an R-33 or R-33s in same setup (they also have long "burn time"), and then try the AIM-54C Phoenix (which is very similar missile to R-33, with reportedly longer range, but Phoenix C in game has modeled short burn rocket motor) and you'll see how propulsion modeling alters the range in shoot-up situation.

I didn't load the Eurofighter & AMRAAM scenario, but from your description I can tell that here the situation is entirely different. Both low flyign and high flying Eurofighter would not be radar-limited against such big RCS target like an AWACS, so the only limit is kinematic AMRAAM range. And the AMRAAM, with more realistically modelled motor data (few seconds of burn to max speed, and then coast only, using parabolic trajectory to gain more range) has very limited range in shot-up situation - so the modelling is correct here.

I noticed that motors of many Russian missiles are modelled differently that western ones. Western ones are given more or less correct "all-boost" profile, with 5...15s of "motor burn time" and then they coast slowing down like in real world. Many Russian missiles seem to retain the long "burn times" from before the patch, the result is they can go full-speed for most of their range and only then become to slow down. This results in much higher average speed and much greater practical kinematic range of Russian missiles. Or maybe the long burn times were used to ensure they can reach their reported max range with the max speed capped at 2375kts. Well, the result is unfortunately they have unrealistically good shoot-up characteristics, better average speed and much better no-escape-zone than those more realistically modeled ones. In general, missile data is inconsistent. Some missiles (missile variants) to get better range were given greater max speed (retaining realistic "burn time") and some other to get better range got longer burn time (retaining the same speed as shorter-ranged versions). Take a look at AIM-120 C4.
The AIM-54 in real life is a special case of a missile - it has long-burn (27-30s) medium thrust rocket motor, so it reaches it's top speed only at the end of it's burn time (and not in few seconds of boost, then keeping it in sustain phase). In game the AIM-54A variant is modelled as 27-30s burn with 2375kts speed (so it should have range similar to R-77-1 then?), but the AIM-54C variant is modelled differently - as a short 9s burn with high 2650kts speed. I understand that the database is a big project, probably many different people added/altered/fine tuned those missiles over years, using different methods to get desired performance. I hope it will be reviewed and standarised in the future.



R-27R 4s 2100kts
R-27ER 13s 2250kts
R-77 13s 2375kts
R-77-1 26s 2375kts <----
R-77M 48s 2375kts <----
R-33 52s !! 2375kts <----
R-33S 82s !! 2375kts <----
R-37 110s !! 2375kts <----

AIM-7M 4s 2100kts

AIM-120B 4s 2375kts
AIM-120C 4s 2375kts
AIM-120C4 22s !! 2375kts <----
AIM-120C5...C7 5s 2500kts
AIM-120D 19s 2650kts
AIM-54A 27-30s 2375kts
AIM-54C 9s 2950kts <----

P.S. there is more consistency in WVR missile motors:

AIM-9B 1s 1360kts (flight endurance of only 3s ?)
AIM-9L,M 1s 1475kts (flight endurance 22s)
AIM-9X 2s 1475kts (-||- 28s)

AA-2 1s 1360kts
AA-8 1s 1400kts
AA-11 1s 1475kts

AIM-9L doesn't work well with it's 1s motor burn. I wonder if AA-11 suffers too, have to check.

edit: AIM-9X also has about 800kts burn-out speed and is quickly being overtaken by the aircraft that fired it if it uses afterburner...

[Dimitris]

@amizaur Some genuinely useful feedback; thank you!

[Quark73]

Hi Quark73!

I tried the Mig-31 scenario.

Thank you very much for this comprehensive answer and effort you put into.

[Tcao]

Hi Quark73!

It's because it's missile R-37 is modelled with almost 2 minutes of engine burn time. Like a ram-jet Meteor or something like that. It means that the missile can keep it's max speed for 110 seconds and only then it starts to "glide" losing speed due to air drag. The missile as modelled, even fired from low alt in dense air has lots of time to climb up and speed up to it's max before it's "engine burns out", so it's range in shoot-up situation is not limited as much as it should.

Amen to that. And here is the missile terminal speed difference when targeting the high and targeting the low Fox

2/28/2023 8:35:18 AM - Weapon: AA-13 Arrow [R-37M, RVV-BD] #7 is attacking high Fox (MiG-31BM Foxhound) with a base PH of 85%. PH adjusted for weapon speed: 68% (pure-aerodynamic attitude control). high Fox has nominal agility: 3.5, adjusted for altitude: 1.8. Agility adjusted for proficiency (Regular): 1.44. Aircraft has a weight fraction of 0.53 - Agility adjusted to 0.98. Agility adjusted for head-on impact effect: 0.6. Final agility modifier: -6%. Final PH: 62%. Result: 65 - MISS



2/28/2023 8:35:42 AM - [BLU] New contact! Designated MISSILE #4 - Detected by high Fox (MiG-31BM Foxhound) [Sensors: Flash Dance [N-007 Zaslon-M]] at 116deg - 45.4nm


2/28/2023 8:35:48 AM - Weapon: AA-13 Arrow [R-37M, RVV-BD] #8 is attacking low Fox (MiG-31BM Foxhound) with a base PH of 85%. PH adjusted for weapon speed: 37% (pure-aerodynamic attitude control). low Fox has nominal agility: 3.5, adjusted for altitude: 3.5. Agility adjusted for proficiency (Regular): 2.8. Aircraft has a weight fraction of 0.45 - Agility adjusted to 2.04. Agility adjusted for head-on impact effect: 1.2. Final agility modifier: -12%. Final PH: 25%. Result: 41 - MISS

it looks like the missile doesn't suffer too much penalty from dense air drag when the rocket motor is still on.

I noticed that motors of many Russian missiles are modelled differently that western ones. Western ones are given more or less correct "all-boost" profile, with 5...15s of "motor burn time" and then they coast slowing down like in real world. Many Russian missiles seem to retain the long "burn times" from before the patch, the result is they can go full-speed for most of their range and only then become to slow down. This results in much higher average speed and much greater practical kinematic range of Russian missiles. Or maybe the long burn times were used to ensure they can reach their reported max range with the max speed capped at 2375kts. Well, the result is unfortunately they have unrealistically good shoot-up characteristics, better average speed and much better no-escape-zone than those more realistically modeled ones. In general, missile data is inconsistent. Some missiles (missile variants) to get better range were given greater max speed (retaining realistic "burn time") and some other to get better range got longer burn time (retaining the same speed as shorter-ranged versions). Take a look at AIM-120 C4.
The AIM-54 in real life is a special case of a missile - it has long-burn (27-30s) medium thrust rocket motor, so it reaches it's top speed only at the end of it's burn time (and not in few seconds of boost, then keeping it in sustain phase). In game the AIM-54A variant is modelled as 27-30s burn with 2375kts speed (so it should have range similar to R-77-1 then?), but the AIM-54C variant is modelled differently - as a short 9s burn with high 2650kts speed. I understand that the database is a big project, probably many different people added/altered/fine tuned those missiles over years, using different methods to get desired performance. I hope it will be reviewed and standarised in the future.

take a look at PL-15 and PL-21 when you get a chance.

[Tcao]

1

[Dimitris]

Responding to the OP plus amizaur's very helpful follow-up:

R-77-1 26s 2375kts <----
R-77M 48s 2375kts <----

This is caused by the missiles not being set to loft currently in the DB. We have been able to confirm that, contrary to the original R-77, the -1 and -M variants can indeed loft. This will be fixed in DB v499.

R-33 52s !! 2375kts <----
R-33S 82s !! 2375kts <----

This is an "interesting" case. The R-33 is, by all references we have found, not able to loft; this would reasonably explain a large burn duration to compensate for that and be able to reach its relatively long range. The R-33S OTOH, does not appear to be in any appearance physically different than the R-33 (with the exception of miniature strakes/fins near the nose, see example: https://twitter.com/DnKornev/status/1385880060964528128 ). Therefore a reasonable explanation for the significantly increase range is that it has obtained lofting ability. This will be reflected in DB v499.

R-37 110s !! 2375kts <----

This is caused by the missile not being set to loft currently in the DB. We have been able to confirm that it can indeed loft. This will be fixed in DB v499.

AIM-120C4 22s !! 2375kts <----

Another "interesting" edge case. For the purposes of dynamic calculation of burn time, AAW missiles that are not part of any aircraft loadout are considered surface-launched, and so their burn times are usually much larger. The vast majority of AAMs are in loadouts and thus do not have this issue, but this example is not currently covered. We'll check if there is any legit loadout this missile should be a part of (suggestions?).

AIM-54A 27-30s 2375kts
AIM-54C 9s 2950kts <----

This _probably_ stems from the higher terminal speed afforded by the improved Aerojet Mk60 motor on the -C. We'll need to take a closer look at this case as there may be other similar examples which have yet to be unearthed. We may have to tweak drag coefficient values depending on fineness ratio (the AIM-47/54 design sacrificed some aerodynamic efficiency in order to be tightly-packed, initially in the YF-12 & F-111B internal bays and subsequently on the F-14 ventral rails).

edit: AIM-9X also has about 800kts burn-out speed

This is something we'll need to investigate separately.

[Dimitris]

Testing the AIM-9X-2 now and it doesn't seem to be limited to 800 knots:



Is anyone able to provide a save where the 800 knots (at burnout) happens?

[Dimitris]

Never mind, investigated and solved on another thread: https://www.matrixgames.com/forums/view ... 2#p5087642