Spaceships hull armor…solid?

[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.