Using Concrete to build space ships...

>--- In ssi_list@... "Valens Agnitio"
>
>> Because of the masses involved, I don't think ion thrusters would
>> work. If we are looking at bringing in several hundred thousand
>> tons, what would an ion engine have to be like to move it in a
>> reasonable amount of time?
>
>> Val
>
>I've been watching this thread unfold and I'm really curious about
>something. When Frank started it he conceded that there were a
>number of drawbacks but he wanted to look at some potential benefits.
>
>OK.
>
>But now conversations are turning to propulsion and I'm wondering
>why no one has brought up the rocket equation.

The more you get into weightlessness the less you have to lift. At
least I was talking also to get those heavy parts of the moon into
open space and take the resources were youll find a lot less gravity.

About 350 kg asteroid weight material of the asteroid 1998 SF36
would be enough to build the cycler craft.

>
>Building a spaceship from concrete will necessitate carrying more
>fuel to propel the ship. One would want to have the lowest dry mass
>possible. Radiation shielding could be achieved internally with
>hollow cylindrical tanks of water that double as repositories for
>ship water needs.

I think youll need as much mass of water for radiation protection as
youll need when using concrete. So were is the difference in fuel
efficiency when using water? The drinking water is a small fraction
compared to the masses used for shielding.

With concrete we would have a rigid hull which gives also the ability
and structural security to screw or plug on thruster/tank units from
the hulls outside.

Frank