Spaceships hull armor…solid?

[Rupert]

Originally Posted by Anthony

I suspect HEAT wouldn't do much against battleships, because by ground vehicle standards they actually have pretty thin armor for their size.

Their guns were also quite small for their size - a WWII medium tank would have a gun of about 3" bore, and 50-70 calibres long. A WWII battleship would have main guns of 14-18" and about 45-50 calibres long (though they had many more, of course). The latter massed very roughly a thousand times to former.

So with 1000+ times the mass with guns only ~5 times the calibre and lower velocity into the bargain it's not surprising their main armour layers were relatively thin, especially as they could use their great size to hide some of their vital components behind many empty compartments to allow fragments and blast to dissipate before reaching them. Also, unlike tanks a warship's structural plating can provide protection from blast and fragmentation, because there's room for complementation, etc. (this, BTW, makes comparing ships of different times and navies hard, because the people designing them split up what counted as 'hull' or 'frame' or 'structure' vs 'protection' or 'armour' differently).