Using Concrete to build space ships...

>Hi Frank

greetings Thor,
>
>1) "While those big mass numbers for concrete hulls
>seem to be steep, compare that with the material
>masses you would need to make them of steel.
>How many tons of ore you would have to dig out and to
>process?
>I guess this would be considerably more for a steel
>hull than for a concrete hull."
>
>Yes iron refining involves a lot more energy and mass
>than concrete for sure. The trick is that iron is
>useful for a lot of items concrete isn't so you would
>need iron production facilities regardless.
On the other hand concrete is used a lot on earth, not many people
live in iron houses while a lot of houses are made of/with concrete.

>The iron
>on the moon is strategically located close to the
>astronauts, easy to control from earth, and able to
>ship to orbit without much fuss. Aside from water the
>asteroids do not offer much else.
>

Didnt you read Dr. John Lewis book "Mining the Stars"?
Most metals found on the moon are from asteroid/meteroid touchdowns
since the heavier metals of the moon itself should have got into moons
core or into deeper regions of it.

So you mine just the crumbs fallen off the minor planets table when
mining on the moon. On asteroids there should be more, much more of
metals than on the moon.

>In comparison, the really big consumers of energy are
>the production of Silicon and Aluminum for solar
>panels and electrolizing water for propellant. These
>are an order of magnitude more energy intensive than
>iron production. It is not going to make that big a
>difference if you use 5% vs 10% of your power to make
>iron.

OK, no objection here.

>
>--------------
>
>2) "Yeah and you probably have to dig it out perhaps
>going underground (mining) while I think getting the
>materials for concrete is mainly picking them off the
>ground of asteroids. So youll need no mining
>gear."
>
>If you have a manned mission to an asteroid backed up
>with a pre-existing structure and processing
>facilities, then I agree - it would be a snap. Short
>of this you have long communication delays which make
>the reaction time of low gravity environments an
>action every couple of hours rather than minutes.
>Without some sophisticated robotic intelligence you
>would be reduced to a glacial pace.

I think you might have come to that rather strong :-).
The earth/sun distance is only 8 light minutes.

Since there are more than 1000 near earth asteroids now we might find
some which are only 1 or 2 light minutes away when we had prospectors
there.

So we are speaking of a delay of say about 5 minutes between actions
(getting the video data from the asteroid to earth and return a
command to the robotic prospector craft on the asteroid) for instance.
I would not call that glacial pace - the delay would be shorter than
that what we have now to Mars.

For the money youll save not having to provide for human life support
and not having to transport humans to asteroids you could engage an
army of engineers on earth which are remote controlling from here.

If you had several prospectors on the asteroid all working on it the
pace to get substantial amounts of asteroidal regolith/ materials
would be rather speedy.

>
>--------------
>
>3) "All this done with heavy gear youll need for
>gravitation disadvantaged moon operations. 200
>thousand tons of material are more
>than 30 thousand tons on the moon but you would have
>to process way more tons of ore to get a steel hull."
>
>To start a decent moon base my current estimate is you
>only need 100-200 tons of equipment. The biggest
>thing you need is electricity and for that you
>manufacture solar panels and distribute them about for
>continuous power generation. It takes a decade to
>build up giving you a solid track record and practice
>making things on the moon.

>5) "Those plates would be heavy and as the mass
>drivers payload capacity is limited youll need a lot
>of metal plates (along with an ironwork
>and a metal sheet rolling mill and a cutting facility
>to fabricate the plates which is not trivial either
>when located on the moon because you have to transport
>it first to and install it than on the moon)."
>
>Imagine a mass driver that looks like a sled that
>hurls multi-ton sized objects of irregular shape.
>Round mass drivers look to have some limitations that
>might be tricky to overcome. With enough electricity
>you can fire the thing every minute or so putting
>1400+ loads in orbit per day. My big change is to add
>an ion drive to each load to make it a guided missile.

Thats a good idea. Perhaps it would be possible to use flying
containers with several ion drives which take on the load?
Those containers could be fully steerable and dock in and out in my
carrier solar sail design with double or magazine docking station.
I will come to it in the next mail.

>
>All you need is a form and a lathe and 100-ton rollers
>for a mill are pretty easy to create. Industrial
>lasers do a pretty good job of cutting and there is
>always extrusion to create simple linear forms like
>bars and rods.

I dont see that but if you say it, may be. I just cant imagine how
to create all that gear which uses heavy electro motors also.

>6) "Since you had a whole lot of metal plates welding
>them together to a space ship hull will need a lot of
>time consuming labor while filling
>the castings with concrete to bind looks just simpler
>to me and seems to be easier to accomplish with remote
>controlled robots."
>
>You might be right about the labor to cast concrete
>into pressurized molds around the asteriods. Robots
>that do not more than weld strips of metal into
>circular hulls are easy to design as well.

I like to read that :-)

>
>Iron hulls solve the impact debris problem pretty well
>and you can cut into the structure at any point to
>make additions and modification easily. In case you
>had to make a serious repair or change, all of that
>concrete would work against you unless you have
>figured out a way to seal the cracks.

Just widen the cracks cover them with strips for instance and fill the
cavities with concrete again.

Frank