Spaceships hull armor…solid?

[Varyon]

Originally Posted by Fred Brackin

In Spaceships aluminum is "Light Alloy TL7" and it generally gives 50% more dDR per 5% of ship's mass used as armor. On that basis (comparing aluminum to the Gurps standard RHA) 1/2 inch of aluminum should give something like dDR3 (or 30 in regular Gurps).

For an SM+6 ship (100 tons like the Space Shuttle) dDR 3 is what an unstreamlined ship gets for 5% of its' mass as armor. A streamlined vehicle would need more mass than that to hit dDR3 (but Whipple plating doesn't usually work very well with streamlining)..

So half an inch of aluminum would be only _part_ of a armor layer on a much bigger ship.

So covering your outer hull with half an inch of aluminum is only "not very much at all" on very large Spaceships. On small sapceships it's an entire armor module all by itself.

Note that's dDR 3 on only 1/3rd of the vessel; to cover an entire SM+6 spaceship with half an inch of aluminum, you're looking at 15% of the ship's mass being armor. Meanwhile, for an SM+10 unstreamlined vessel, where each module of light alloy armor provides dDR 15 to 1/3rd of the vessel, you could get away with roughly 3% of the vessel's mass to get that half-inch layer of aluminum over the entire surface (1 module - 5% of mass - over the entire surface would provide dDR 5, and we only need 3/5ths of that).