On Sun, Nov 30, 2014 at 08:43:59PM -0600, Grimmund wrote:
> Tim-  Any significant difference for just using scrap iron?  Maybe
> with a little DU or tungsten cap?

Iron is quite a bit less dense than tungsten, so less than half the
mass (and impact energy) per unit volume.  Apart from that, at that
size there wouldn't be much difference.  Smaller projectiles might
have to worry about melting, but by the time those things are through
the atmosphere, the interior won't even be warm.

- Tim