Is spaceship armor useless?
 

Today I was reading through Spaceships and trying to design a TL9 civilian ship that could defend itself against pirate attacks. And it seems to me that armor is nearly useless; any ship of a given size can easily mount weapons that can defeat any reasonable quantity of armor that ship could carry.

In fact, it's worse than that. The smallest conventional projectile listed - 2cm - does 6dx5 dDam, or about 100 on average, which vastly exceeds the dDR on all but the largest and more ridiculously armored ships. In other words: small fighters can kill nearly anything.

Is there something I'm missing here, or is armor really that useless?

Re: Is spaceship armor useless?
 

Armour is indeed very low, but the effect is made worse by just how much damage kinetic weapons do.

Re: Is spaceship armor useless?
 

Where are you getting this number? I see 3d dDAM as the base damage for 2 cm guns?

Edit: You're looking at 20 cm, the smallest gun is 2 cm.

Edit 2 (my signature isn't far from the truth):

I see that the smallest fighter can mount a 16 cm missile at a minimum or an 8 cm gun not counting making it smaller using rapid fire. Keep in mind, though, that civilian ships probably won't be able to survive serious weapons fire. They'll have minimal armor (one layer per hull location) and possibly even the cheapest they can get (to save on costs) meanwhile warships will carry multiple layers of expensive armor and (in many settings) shields and the simple differences in size driving the numbers upward. Look at the armor rating of a SM+15 ship with multiple layers of an expensive armor.

Personally I've found it hard to justify fighters when you're in a fleet engagement. Unless the fighters are solely tasked with targeting support vessels (cargo and tanker vessels, etc.) they really can't make a dent in heavily armored warships, either with missiles and flying like a bat out of hell before firing them. (With the exception of firing nuclear and antimatter missiles.)

Re: Is spaceship armor useless?
 

Realistic spaceships (which is the default assumption) behave much like submarines when it comes to combat, which means a small ship can take out much larger ones.

If you want to change that assumption, change it. Triple the armor and HP. Alternatively, treat each hull section independently, with its own HP.

Re: Is spaceship armor useless?
 

Well, you're missing that guns are pretty much worthless unless other options are forbidden, due to their awful range and penalties to hit, and you seem to have the damage very wrong somehow.

However, if we look at missiles, the 16 cm missile certainly does do a quite satisfactory job of smashing through the armor of anything except a quite large and heavily protected craft.
Submarines have stealth. Unless you use cloaking fields, stealth is practically impossible for a functional spaceship. I know, I've got a stealth spaceship design posted and while the stealth part appears to be sound, the thing is so limited as to be nearly useless.

Re: Is spaceship armor useless?
 

Spaceship armor is a bit screwed up due to the assumptions used in Spaceships. I believe there's rules in one of the later books for modifying DR for ships with lots of armor (as they have lower volume and thus surface area than the default rules assume).

Re: Is spaceship armor useless?
 

Both Spaceships 3 and Spaceships 4 have additional rules for various aspects of Spaceships Combat. Specifically, I think you're talking about GREATER SURVIVABILITY, Spaceships 3 Page 35, which while within the Tactical Space Combat chapter, could be applied generally.

Re: Is spaceship armor useless?
 

The Armor/Volume rule is from Pyramid 3-34 along with several other rules tweaks for Spaceships.

Essentially you get a multiplier to dDR because a ship with a large percentage of it's mass in Armor is going to have a reduced volume because of Armor's high density, and a smaller volume ship has less surface area which will increase the Armor's thickness and thus it's dDR.

Re: Is spaceship armor useless?
 

It does make sense that if most of a ship is armour, its SM should be reduced by 1 because it's a lot denser than the implicit assumption in GURPS Spaceships. But I think that's only reasonable for extreme cases, where maybe half the ship's mass units are devoted to armour. It's even something I suggested, although without specifying where the threshold should be, long before the pertinent GURPS Spaceships volume came out.

Re: Is spaceship armor useless?
 

Ooo, I'd forgotten about the extra Spaceships rules in that Alternate GURPS Pyramid - Thanks.
Are there any other Spaceships rules in Pyramid, apart from those and 3-30, the Spaceships Issue?