Spaceships: Is Defensive ECM worthwhile on big ships?

[VonKatzen]

I can see that the -2 to hit would be useful on an SM5 fighter, but it seems a bit less useful on an SM11 battleship. In the first it cancels out almost half the SM modifier, in the second it's less than a fifth.

[Agemegos]

Perhaps range modifiers can produce circumstances where it becomes significantly advantageous.

[VonKatzen]

Originally Posted by Agemegos

Perhaps range modifiers can produce circumstances where it becomes significantly advantageous.

Maybe. And you can have up to 3, so a carrier with 3 ECMs might make sense (since carriers mostly have guns for point defense and depend on fighter/bombers for offense). In a battleship, though, that's just 3 spaces that could be 30x 1GJ turret lasers doing point defense, or 10 nuclear missile tubes.

[Anthony]

Originally Posted by VonKatzen

I can see that the -2 to hit would be useful on an SM5 fighter, but it seems a bit less useful on an SM11 battleship. In the first it cancels out almost half the SM modifier, in the second it's less than a fifth.

It's all a matter of range and other penalties. If ECM reduces hit probability from 18 to 16, not worth it. If it reduces hit probability from 10 to 8, worth it.

[VonKatzen]

Originally Posted by Anthony

It's all a matter of range and other penalties. If ECM reduces hit probability from 18 to 16, not worth it. If it reduces hit probability from 10 to 8, worth it.

Makes sense. In the first case all you've done is fiddle with his critical range and he'll still probably hit, in the second you've given him a good chance of critical fail and high probability of missing.

OTOH big ships tend to be slower to accelerate and bank anyway, so they're less likely to have further penalties against the target. Of course if your big ship has a massive spinal laser cannon you can shoot from so far away they can barely see you, which means huge range penalties.

GURPS Spaceship combat seems like it'd look a lot like Macross...nuke, nuke, laser, everything's dead.

[Anthony]

Originally Posted by VonKatzen

GURPS Spaceship combat seems like it'd look a lot like Macross...nuke, nuke, laser, everything's dead.

I haven't really done combat with GURPS Spaceships, but it's very hard to come up with a model for space combat that isn't boring. Beam combat is mostly a slugging match, missile combat tends to be resolved on the first attack (either you launch enough missiles to swamp point defense and he melts, or you don't and you wasted your ammo. Either way, you likely don't have ammo enough to do it again).

[VonKatzen]

Originally Posted by Anthony

I haven't really done combat with GURPS Spaceships, but it's very hard to come up with a model for space combat that isn't boring. Beam combat is mostly a slugging match, missile combat tends to be resolved on the first attack (either you launch enough missiles to swamp point defense and he melts, or you don't and you wasted your ammo. Either way, you likely don't have ammo enough to do it again).

That's pretty much what modern naval combat is already like - any competently armed navy can hurl cruise missiles at the biggest aircraft carrier you have and destroy it with 1-2 lucky hits. And cruise missiles are a lot cheaper than aircraft carriers!

In space it's the same thing but with no cover, perfect visibility, no air resistance to muddle your targeting, etc. And far lower consequences for using nukes! Nukes are absolute killers in space combat, unless you have Woo^ powered shields. You don't even have to hit with a nuke!

It's funny in Star Trek, etc. where they have these supposed continent melting particle beams and yet somehow when you hit someone it just 'disables their engines'. BS! The radiation scatter and IR bleed alone just turned everyone into cancer puddles. And what about microwave refraction sending lighting bolts through every deck? There's really no way you can use a weapon that powerful and just get 'disabled', it's all dead or dying or you missed.

Space combat is the extrapolation of the trends 'weapons > armor' and 'nukes > all material substances' taken into a horrifying combat environment where dodging is almost impossible because lasers hit you before you see them.

[RyanW]

Originally Posted by VonKatzen

Nukes are absolute killers in space combat, unless you have Woo^ powered shields. You don't even have to hit with a nuke!

You've got to get pretty close, though. Any sort of shielding would make most nuclear weapons practically useless beyond a few kilometers, which in terms of expect space combat ranges is practically contact. It would mostly be soft x-rays, which drop off rapidly if there isn't an atmosphere to absorb them (superheating said atmosphere in the process).

[Phoenix_Dragon]

ECM is good when the enemy has a middling chance of hitting. If your enemy has an effective skill of 10, it halves their chance of hitting, and that effect gets larger as the effective skill gets lower. Above that, the effect starts diminishing; at an effective skill of 12, you only drop their chance to hit by a third, and at 15, you only drop it by a tenth. Also keep in mind that you can stack ECM up to three times, even if they do hit you it can reduce the number of hits you take from bursts, and that if the enemy takes a tactical sensor array, the effect of ECM gets cut pretty hard.

So it probably depends on the role of your craft. For beam duels, if you can be sure that the enemy will be kept at a range where their shots are at mid to low effective skill while yours are higher, then ECM is good. Arranging that seems a little more difficult. If you've got more powerful engines and can ensure distant-scale engagements (X-range weapons), ECM might be a good idea.

On the other hand, if your enemy uses ballistic weapons where range doesn't matter, small craft could get pretty good effect from ECM; lower SM means more likely to be in the good range for ECM, and low armor probably makes ECM more effective pound-for-pound than armor against large guns. Complicating this is that stripping armor might make you more vulnerable to lighter point-defense weapons, but weapons damage is so high relative to armor values that the loss might be of little consequence. For example, a ship using tertiary very-rapid-fire electromag guns firing against a single layer of TL 10 nanocomposite armor will just penetrate against:

A ship of equal size (Unhardened armor and direct strike)
A ship of 1 SM less (Hardened armor or proximity burst)
A ship of 3 SM less (Hardened armor and proximity burst)

Now, it'll do fairly little damage (Around 10% of HP per hit), but a single tertiary battery could be throwing out 150 of those rounds per second. They'll only hit with a few of those, and even if they do hit you, each ECM effectively removes one hit. But being unarmored would mean each hit is vastly more destructive. So if you're a small craft in this situation, a single layer of armor on any facing you expect to take fire from, plus as many ECMs as you can pack in, probably gives you the most staying power.

Though if you're a smaller ship within ballistic gun range of a larger ship, 'staying power' probably isn't a winning strategy...

Overall? I'd say once you've got a layer of armor on each section, an ECM probably gives you more survivability than another system of armor so long as you're not getting up-close and tanking a ton of shots. And considering how many layers of armor you'd need for that to be viable (2+ hardened against beams, maybe 4+ hardened against ballistics!), that's probably not a situation you ever want to be in. Maybe if you're something like 3+ SM larger than all your enemies.

One further note, though; if you're in a large formation of ships, having a dedicated electronics-warfare ship using area jammers (Spaceships 4) is a great idea. An entire battlegroup built around a core of SM +13 battleships can be covered by a single EW ship (Though you'll probably want a few for maneuvering). -3 to be hit to your entire fleet is pretty nice. Give them a bunch of armor (Especially if you're using the Armor and Volume rule in Pyramid #34!), and they might even draw significant amounts of fire off your damage-dealers.

[Rupert]

Originally Posted by Phoenix_Dragon

ECM is good when the enemy has a middling chance of hitting. If your enemy has an effective skill of 10, it halves their chance of hitting, and that effect gets larger as the effective skill gets lower. Above that, the effect starts diminishing; at an effective skill of 12, you only drop their chance to hit by a third, and at 15, you only drop it by a tenth. Also keep in mind that you can stack ECM up to three times, even if they do hit you it can reduce the number of hits you take from bursts, and that if the enemy takes a tactical sensor array, the effect of ECM gets cut pretty hard.

Also, ECM gives bonuses to your Dodge roll as long as the enemy isn't higher TL than you.

For example, a ship using tertiary very-rapid-fire electromag guns firing against a single layer of TL 10 nanocomposite armor will just penetrate against:

A ship of equal size (Unhardened armor and direct strike)
A ship of 1 SM less (Hardened armor or proximity burst)
A ship of 3 SM less (Hardened armor and proximity burst)

This is incorrect - hardening doesn't do anything vs proximity attacks, as they have no armour divisor to reduce.