Using Concrete to build space ships...

Good point about concrete... Need water. I imagine that vacuum would play
havoc with the whole mess anyway, even if water were easily available.

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. An addtional membrane on the interior surface
could be emplaced to stabilize the moon dirt against longitudinal
accelerations. Think of a spinning toilet paper tube with the inside coated
with dirt, and a saran wrap covering to hold it in place.

Val

>Date: Thu, 19 Feb 2004 11:26:06 -0800 (PST)
>
>Greetings Frank,
>
>I'm pleased to see your post. Here are a few items
>for your consideration.
>
>1) "How about building the hull of a space ship out of
>concrete and completely in space derived from
>asteroidal resources using molds to
>concrete it near the material source and bring the
>ready made hull back to earth orbit or into an
>earth-mars cycler orbit?"
>
>Concrete is legitimate material if you have easy
>access to water. In the near term, this would compete
>with water for propulsion and habitat (growing food)
>so there might not be much available.
>
>2) "The advantage would be that we could handle
>masses .. (which) have practically no weight in space
>with very weak propulsion devices (ion drives for
>instance). And we dont have to launch this tremendous
>weight from the moon again because its already
>there."
>
>Launching things from the moon by chemical means is
>expensive (have to make the propellant) though a small
>fraction of the cost from Earth. Launching things
>from a built up mass driver on the moon would be
>different as all you need is electricity and some
>guidance system to get the objects to their
>destination. This requires the size of each piece to
>be fairly small though the total capacity to move mass
>to orbit is huge.
>
>3) "What has to be launched from earth are relatively
>lightweight molds and lightweight space crafts because
>they only use fuel effective
>electric propulsion instead of chemical propulsion or
>atomic reactors."
>
>You may have a significant problem with control and
>communication. The moon is close enough for near
>real-time remote control of robots (2.5 sec delay).
>Everything else is too far so you get into the game of
>intelligent robots to 'know' what they are supposed to
>do with infrequent commands. The cost and complexity
>of a robotic asteroid mission would be huge. Notice
>how slow the rovers are on Mars.
>
>4) "I figure that we could pick up most of the
>materials needed for concrete from stony asteroidal
>surfaces, not having to dig down...So asteroid
>prospecting devices (in fact little space crafts like
>flying container with arms or flying scoops with
>hatches) would deliver the materials (sands, water,
>cement) to refining and processing units in space from
>were the different materials get to the space based
>rotating cement/concrete mixer units."
>
>To make concrete you still need to sinter some rock to
>make cement so you will need a fair bit of power.
>Making fiberglass pieces on the moon and shipping them
>to orbit via a mass driver may be just as cost
>effective. Asteroids are very complex and you may
>have to dig down quite a ways just to anchor to it.
>
>5) "I figured about 214 thousand tons for a 108 meters
>diameter pretty flat cylindrical hull of only 18
>meters length and 4 meters wall thickness.."
>
>It's good to big numbers like 214,000,000kg's of mass.
> Metal has more flexibility and is easier to join
>things too by welding. Iron is roughly 4 times as
>compact and could be formed into lots of small
>compartments giving additional protection from space
>debris. There is a desire to minimise the debris from
>an impact as even a stray sandgrain can cause
>considerable damage. Concrete crumbles while soft
>iron would deform leaving fewer if any additional
>fragments.
>
>6) "Now we could let lift those rings (the bigger ones
>weighting about 3100 "tons on earth) through robotic
>space crafts without gravity at all."
>
>Mass drivers are fully robotic :)
>
>Cheers, Thor
>

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