Spaceships hull armor…solid?

[weby]

Originally Posted by Phantasm

Pretty sure this is a "changed my thought halfway through"; it's 6 rear, not 2.

But yes, an armor module - like all modules - takes up 5% of the ship's overall mass.

Indeed, wrote the thing in a different order first but was less clear so then had a copy paste error on rewrite.. :)

[Polydamas]

When I saw the original thread topic, I thought it was about whether the GURPS Spaceships rules assume thick solid armour like in space opera or Whipple Shields like on some real spacecraft.

There are some quibbles whether spaceships with a lot of armour should have their SM reduced because so much mass is in high-density armour, but any simple rule has limits.

[Varyon]

Originally Posted by Polydamas

When I saw the original thread topic, I thought it was about whether the GURPS Spaceships rules assume thick solid armour like in space opera or Whipple Shields like on some real spacecraft.

I don't think there's an option for Whipple Shields anywhere in Spaceships. Such probably wouldn't count as high-density systems anymore, but would have much better performance against hypervelocity impactors.

Originally Posted by Polydamas

There are some quibbles whether spaceships with a lot of armour should have their SM reduced because so much mass is in high-density armour, but any simple rule has limits.

As I mentioned upthread, Pyramid #3/34 has official rules for this. Basically, if you have 25% (5 systems) or more of armor, the surface area of the vessel decreases enough that a given mass of armor actually gives more protection. If you have 60% (12 systems) or more of armor, the volume of the vessel decreases enough for an outright reduction of -1 to SM. If you have 90% (18 systems) or more of armor, the volume of the vessel decreases enough for an outright reduction of -2 to SM.

[Fred Brackin]

Originally Posted by Varyon

I don't think there's an option for Whipple Shields anywhere in Spaceships. Such probably wouldn't count as high-density systems anymore, but would have much better performance against hypervelocity impactors.


.

They might for certain values of impactor size and velocity compared to equal masses of solid armor but not for all impactors. If the striking object is either too bg or too fast Whipple Shields would be ineffective. Also, they are ablative though against crater-making impacts (or ionizing radiation) all armor should be.

[Varyon]

Originally Posted by Fred Brackin

They might for certain values of impactor size and velocity compared to equal masses of solid armor but not for all impactors. If the striking object is either too bg or too fast Whipple Shields would be ineffective. Also, they are ablative though against crater-making impacts (or ionizing radiation) all armor should be.

I mean, they'd still provide DR, not outright immunity. An object that was too large and/or too fast would simply do too much damage for the improved DR to make much difference. Maybe it would be more realistic for there to only be a certain range in which the multiplier (whatever it is) applies, but I feel it would be simpler to just set a speed limit beyond which the Whipple Shield gets a sizable DR multiplier, and let the fact this doesn't work effectively against really big and/or fast targets come about naturally (from such targets dealing enough damage they basically ignore the DR, multiplier or not). Or maybe make the multiplier all-or-nothing?

And, yeah, a lot of threats spaceships face should probably ablate most if not all armor materials, but for simplicity GURPS generally reserves that option for corrosive damage.

[Rupert]

Originally Posted by Varyon

I don't think there's an option for Whipple Shields anywhere in Spaceships. Such probably wouldn't count as high-density systems anymore, but would have much better performance against hypervelocity impactors.

If you're feeling generous, call that 'hardened'. Personally, given the mass and energy of the weapons we're looking at, I don't think they'd help much unless both layers of armour were quite think and the gap quite large - enough you couldn't really even call it 'spaced armour', but more like two complete hulls.

[Rupert]

Originally Posted by Varyon

I mean, they'd still provide DR, not outright immunity. An object that was too large and/or too fast would simply do too much damage for the improved DR to make much difference. Maybe it would be more realistic for there to only be a certain range in which the multiplier (whatever it is) applies, but I feel it would be simpler to just set a speed limit beyond which the Whipple Shield gets a sizable DR multiplier, and let the fact this doesn't work effectively against really big and/or fast targets come about naturally (from such targets dealing enough damage they basically ignore the DR, multiplier or not). Or maybe make the multiplier all-or-nothing?

And, yeah, a lot of threats spaceships face should probably ablate most if not all armor materials, but for simplicity GURPS generally reserves that option for corrosive damage.

Once it becomes ineffective it will likely rapidly become less effective for a given mass than a single layer. Given how abstract Spaceships is, I'd just assume the designers chose the best (or least bad) option against the threats they expect the ship to face, and that this is built into the stats the system produces.

[Polydamas]

Originally Posted by Rupert

If you're feeling generous, call that 'hardened'. Personally, given the mass and energy of the weapons we're looking at, I don't think they'd help much unless both layers of armour were quite think and the gap quite large - enough you couldn't really even call it 'spaced armour', but more like two complete hulls.

My understanding is that since the 1960s, armour schemes against anything more powerful than an autocannon or roadside bomb have focused on spaced layers with air gaps or soft material between them, and that its even less plausible that solid armour would help against threats to high-powered spaceships. But its not my field.

And its not "both layers" but "all n layers" (the Stardust probe on Wikipedia seems to have at least four). Each breaks up and scatters the oncoming projectile until the fragments can be stopped by a feasable thickness of armour.

[Agemegos]

Originally Posted by Polydamas

My understanding is that since the 1960s, armour schemes against anything more powerful than an autocannon or roadside bomb have focused on spaced layers with air gaps or soft material between them, and that its even less plausible that solid armour would help against threats to high-powered spaceships. But its not my field.

And its not "both layers" but "all n layers" (the Stardust probe on Wikipedia seems to have at least four). Each breaks up and scatters the oncoming projectile until the fragments can be stopped by a feasable thickness of armour.

Furthermore, the faster an impactor is, the more damage it takes from a thin outer layer. What you need to deal with a super-duper-hypervelocity impactor is not thicker layers but more space for the fragment plume to spread out through.

[The Colonel]

Originally Posted by Polydamas

My understanding is that since the 1960s, armour schemes against anything more powerful than an autocannon or roadside bomb have focused on spaced layers with air gaps or soft material between them, and that its even less plausible that solid armour would help against threats to high-powered spaceships. But its not my field.

And its not "both layers" but "all n layers" (the Stardust probe on Wikipedia seems to have at least four). Each breaks up and scatters the oncoming projectile until the fragments can be stopped by a feasable thickness of armour.

I think modern layered armour is more about different materials to counter different forms of penetration and mess with energy transfer.

Old school battleship armour demonstrated pretty thoroughly that single plates were more effective than greater thicknesses of laminated plate - no-one bothered to create a battleship grade HEAT round.