Using Concrete to build space ships...

Would it be safe to say that the propelling of the
ship is the more difficult detail? To have both
radiation shielding and artifical gravity you are
going to have high mass one way or another.

I have heard somewhere that the Russians can use
oxygen in their ion systems. If true this would
eliminate the dependency on terrestrial Xenon.

For all of the trouble of Nuclear systems, just
splitting water gives you a very respectible and well
known propellant that can be liquified. Nobody will
care if you leave a wake that falls back on earth now
or in a hundred years.

Am I missing something by this argument?

- Thor

>
> You may say that you'll use a high efficiency Ion
Engine with a high ISP. OK. Where will you get 56,400
tons of Xenon? From Earth.