starship-design: Hull Materials

["L. Parker" <lparker@cacaphony.net>]

I would like to start a discussion on a topic which I know very little 
about.

Does anybody out there know much about chemistry? Particularly refractory 
metal compounds with high molecular weight?

Any ship we design that is capable of achieving substantial fractions of c 
will be exposed to enormous amounts of radiation and material impacts. I 
have seen several proposals for using frozen deuterium ice (fuel) 
surrounding the ship and providing shielding from impacts. Of course, this 
assumes that you are using hydrogen for fuel...

I want to explore alternatives for the actual hull of the craft. What 
metals are available, what sort of melting points, etc. I think of 
particular interest would be the X-ray density, ductility, and hardness 
numbers.

Some of the most refractory metals with high melting points and high x-ray 
density are borides and carbides of Tantalum, Tungsten, and Uranium. 
Unfortunately, these metals are not very ductile, in other words they are 
extremely brittle. The ideal candidate would possess the advantages of 
Tungsten Carbide in a more malleable form. Perhaps some sort of Chobham 
type of armor with layers of metal and ceramics.

As a comparison, what is the X-ray density of deuterium ice? How much more 
ice would be required to equal the shielding of one of the refractory 
metals?

Anybody else have any thoughts?

Lee

                                                          (o o)
------------------------------------------------------oOO--(_)--OOo-----  
----
Up the airy mountain,
Down the rushy glen,
We daren't go a-hunting
For fear of little men;

William Allingham, Ireland, 1850