Using Concrete to build space ships...

> Concrete is an excellent building material. it is strong, offers
> excellent radiation protection and we have allot of experience
> working with concrete. We understand it physical properties and
> limitations. As man continues to move into space, we will also use
> concrete when appropriate.

Charles has already addressed this point, so I'll echo his comments.

> For structures on the moon and mars I believe that it is an
> obvious choice. Assuming that there is a source of calcium
> available that is not too toughly bonded in minerals such as
> plagioclase feldspar.

I've already placed two files on lunar concrete construction in the
FILES section.

> For spaceships, concrete is heavy. I believe the mass issue is
> less of a concern than Tango man has indicated. If we build a
> cycle for sending colonist to mars, it will be massive. whether
> it is made of iron, cast basalt, or concrete, it will have
> considerable mass. Even if it was built out of aluminum or
> titanium, it would be massive enough that blasting it into the
> cyclic orbit would a great expense.

Massive isn't a fixed term, like "everything over 1,000 tons is
massive, so it matters not whether the ship is 1,000 tons or a
1,000,000 tons. They're both massive."

These considerations are all relative. If your ship is a tenth the
mass of the alternative, then your fuel requirements will also be
reduced proportionately.

> The trick is to build the cycle out of material that is in an
> orbit closer to the orbit that we need. That way the amount of
> deltav can be reduced.

Which is my point. If you're going to build a cycler, then it's
better to find an asteroid that approximates such an orbit. Strip
the asteroid while it plies it orbit, and build yourself the ship,
or convert the asteroid into a cycler. The building material is
already moving at the delta-v.

The proposal to get material from an asteroid, ship it to cislunar
space, fabricate it into concrete, and then launch it on a cycler
orbit, is just wasteful of energy, and because it's wasteful it's
also expensive.

TangoMan