Using Concrete to build space ships...

>Good point about concrete... Need water.

Do you think there is no water on Asteroids in form of ice or
permafrost?
I think it is more likely to get it there than on the moon.
Take a look on that site for instance
http://www.k26.com/witus/What_s_New/Solar_System/Planets/Asteroids/asteroids.html

or here
http://www.canoe.ca/CNEWS/Space/2002/12/05/6550-ap.html

or for water on comets here
http://science.nasa.gov/headlines/y2001/ast18may_1.htm

If you dont find it on the moon or it is to complicate to extract
there you would need it to transport to the moon for processing first
fighting moons gravity, that is obviously not efficient.

If you dont find water on the asteroid were you get the stony
components you could find a snowball type of asteroid or comet and get
water using the almost free transportation services of solar sails.

My point here is, when using solar sails it is possible to get all
materials even from different asteroids for cheap since transportation
is cheap with them and bring those materials from different locations
to the construction base.

Our sun is out of hydrogen and ejects it all the time with the solar
wind. So you may find the main part of water not only in ice-form but
in all minor planets which get touched of the solar winds.

> I imagine that vacuum would play
>havoc with the whole mess anyway, even if water were easily available.
>

I dont see why. Vacuum isolates, yes but does it hinder the binding
process of concrete?
You need temperatures of more than the freezing point at 0 grade
Celsius or better more than 15 grade and you could warm the concrete
molds with concentrators and ordinary exposure to sunshine just to the
right temperature.

>However, a simple structural skin, possibly of composites and ver liight
>weight, could easily (relatively) be assemblede moonside, then lifted into
>orbit, set to spinning and then fill it with moon dirt to desired thickness
>and, voila, shielded shell.

That may work even if I am sceptical about the stability of such a
construct. For instance if you have some meteorite impacts.

The question in this case too is, why not get this dirt or regolith
off asteroids instead off the moon, avoiding the moons gravity well at
all?

Having a rigid hull of concrete has one more benefit. You could put
attachable/detachable thruster units consisting of tanks and the
thrusters on its outside just by screwing them on or drilling a hole
into the hulls outside were you plug part of the thruster unit in.

Those units could be filled with fuel from outside and be remote
controlled so that the craft would be able to be steered.

Frank