Who knows about the Roswell crash. This article claims that Werner Von Braun actually handled the materials from the Roswell crash site and they seemed something like skin except that the materials were very strong and aluminum covered. Now consider the fact that there are already bacteria that concentrate iron and manganese. Maybe there are bacteria that concentrate other pure elements. A substance like that that appears to be "like skin" might be grown on a scaffold, or form, like the experiments with replacement organs that are going on right now. Actual human skin is being grown by the square foot, also. So, if an organism can be engineered into growing very specific substances, like the chitinous shell of an insect, out of metals and silicon, then it can produce arbitrarily large pieces of material that can be used for a spacecraft hull. Maybe instead of going through all of the chemical process and heating processes to manufacture a metallic ceramic material, it would be better to build it molecule by molecule this way, using bacteria or other living material, maybe modified animal or vegetable cells. A silicon-based cellulose is an idea, and so is incorporating a thin layer of metal to deflect ultraviolet. If the manufacturing matrix is an actual skin, then it will be dependent on support from the culture medium and can't get loose like bacteria can. Maybe this isn't even a very original idea, but it's new to me. It seems like it could work out to be quite cheap and could work with lunar materials.