Re: Concrete permeability

[Nathanael Henderson <jude@pconline.com>]

     A few thoughts on concrete....   It may be the perfect material for a
habitat, but would it's lower impact resistance make it suitable for a
submarine?   If I walk up to a steel hull and whack it with a hammer, I
can be pretty confident it's not going to crack--how well would these
concrete hulls stand up to a blow?
   Hull penetrations seem like a real nuisance to design (since it's going
to be harder to get a seal against concrete than steel.)   The idea of
concrete hulls is intriguing, but I'm a little paranoid about how unproven
the technology seems to be.  Is the cost savings really that compelling?