|MadSci Network: Engineering|
Hi Bill You certainly need not worry about the vacuum of space getting inside the concrete. It is there already inside EVERYTHING. Even an atom like uranium, that you might think is packed full of all those electrons, is by volume 99.99% vacuum (space). So space is NOT "out there" sucking things outwards! Concrete is made of stones stuck together with cement. On earth we find the stones as sand lying around (e.g. on the beach). It comes in various grain-size (sand, shingle, pebbles) and we make mortar and cement by burning chalk (to make quicklime) and slaking this with water. It sets irreversibly by reacting with the carbon dioxide in the air. So the answer is we use as building material anything we can find lying around. On a watery planet like ours man's ingenuity, cutting stone and inventing Portland cement (Edison stole that from a German inventor! : see Google and Wikipedia), has provided the materials to build PROTECTION from that same watery and windy weather that created those materials. On the moon and mars it is probable there was water in the past and the crusts are silaceous (silicon, aluminium, iron based) like ours. So there is plenty of base material, and fortunately plenty of man's ingenuity to solve "trivial" problems like "short of CO2" and "no longer rains". On mars there IS weather to contend with, but on the moon that is not a problem (neither wind, rail, hail nor sleet). What is needed , especially on the moon, is RADIATION protection and a means to contain a breathable atmosphere. You might think a bubble of thin plastic, inflated after arrival on the moon would do. Unfortunately the protection required is from a nuclear reactor (the sun for a starter and cosmic rays to follow) and to stop those radiations takes MASS. Of course on the moon mass will not be heavy! A good start might be a plastic film as an inflated bubble covered with a layer of moon-dust. (The dust is there even on a never-had-water planet because of the huge temperature difference between sunshine and night.) Remember there is no wind to blow the dust away on the moon. A real hazard, especially on the moon, is the destructive arrival of meteors! It is a bit energy-expensive, but a determined moon-dweller, and especially a mars dweller could split rocks (or search for them!) to build a dry wall - an igloo if you like but made of stone. There are all sorts of new shape- remembering sheet plastics a few ounces of which would internally seal such an "igloo" and make it airtight. These you'd bring with you from earth. You'd need an air-lock of course - and Velcro (see Google) might help there. On the moon such dry walls would be fragile - against you bashing against them - but would have no storm, tempest or flood to put up with. If your space ship is to stay with you it too really needs an igloo-hangar, or underground garage, to protect it from meteor-damage. Have a good trip! David
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