[FIXED][1328.18] Ship defence against sea skimmer subsonic anti-ship missiles

[MistahIggy]

See attached save file. A group of 8 F/A-18E are set up to shoot 20 AGM-84G Harpoons against the Arleigh Burke (20 is the supposed missile defence value). On average, 8-12 Harpoons make it through the anti-air defenses and sink the ship. This seems like a lot?

I've loaded up the Arleigh Burke with plenty of SAMs. All radars and OECM are on. Only doctrinal change was reducing range on relevant SAMs to 50nm to avoid shooting at the aircraft for testing purposes.

When trying to manually fire against the incoming Harpoons I get the following messages on the weapon allocation screen (all within 15 nm):

• Out of DLZ range

• Est. intercept point is outside weapon's valid altitude envelope

• Firing unit must obtain a high-quality track on the target before firing

Is this expected behaviour against a wide spread of concurrent missiles? The ship's defences seem much more effective when testing against a linear string of incoming anti-ship missiles.

[Nikel]

With automatic fire, the destroyer seems to lose always or near, not sure why.


In this case the best solution is just to shoot down manually all the aircraft before they fire

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Now the objective of the test is not that as you said, if you want to let them shoot their missiles, again shoot all of them manually when the target is certain.

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[Nikel]

OK, now that I know the weapons used, you may succeed automatically changing the WRA of both weapons that by default are limited for the incoming barrage:

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This is the result

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[Nikel]

Another test, the course of the ship is very important.

If you "run away", the ship will defend without changing anything.

Perhaps more time for defense or the weapons fire better with the stern to the targets. The automatic position of the ship is perpendicular to the missiles when the attack is detected.

[thewood1]

I think expectation setting might be in order. A single DDG without any early warning against 20 sea-skimming and very low altitude SSMs is not going to ever be guaranteed to come out unscathed. On top of that, the ship was stock still. I set all SAMs to follow standard USN doctrine of allocating two SAMs per SSM. I also extended out the firing range just to make sure. I'm not sure that made a difference. The VLS loadout probably needs to be reviewed also. The last thing I did was just set the ship in motion at approximately 90 deg to the attack axis. That little bit of extra time and distance for the SSMs to track a moving ship make a difference.

After doing that, in five runs, only one SSM made it through.

One thing to note is that the ESSMs sometimes don't fire at all. It happened twice and will have to look at that. It seems to be caught in an interpretation of min altitudes. In the original and unmodded tests, the SSMs get into minimum SAM range quickly for the SM-2s and -6s. Without the ESSMs, you will get leakers now and then. But in the majority of tests, the ESSMs do fire.

The short of it is that you can set up a scenario to overcome any unit's defense capabilities.

[MistahIggy]

Thank you for the prompt review and responses.

That's interesting, if I set the DDG to move perpendicular at the very start (before Harpoon launch), it develops a clear unambiguous radar detection of all the Harpoons around 18nm. All of the incoming missiles show as green and available to fire at. Without changing any WRA settings from default, the DDG is able to defend itself in almost all repeated tests.

In my original test, the DDG detects the anti-ship missiles being launched and goes defensive setting a perpendicular course. The incoming missiles are detected around 18nm, but the DDG can only seem to engage half of them even with manual targeting. A group of ~10 Harpoons in an eastern pack are untargetable from 6nm through to impact even by ESSM.

The trajectories are slightly different between the two scenarios. In the original test, the Harpoons track to the original ship location then turn and track directly into the ship once they find it. When setting up the DDG to move from the start, the Harpoons lead the target and track directly for the ship. I'm not sure how this is impacting the calculations, but it seems to make a big difference.

The minimum altitude issue is what first made me wonder if there's an underlying bug. The "outside DLZ range" rational also seems odd since other Harpoon missiles in the same salvo are engageable.

[thewood1]

I think the best thing that comes out of this is the built-in variability. Even though CMO builds a large number of variables, its good to still see a little variability in repeated runs.

[blu3s]

This issue is fixed in the new beta (and soon the new stable version)