Throughout the construction process and during DL4’s lifetime, there will be multiple materials used that can be synthesised from non-terrestrial sources. Of particular interest to construction are lunar glass-ceramics as well as ‘lunarcrete’ and ‘astercrete’. Internally such materials can be used to make structural beams, walls, floors, pipes and electrical insulators while externally as waveguides on SPSs and communications antenna farms. Also glass will be used for solar cell covers and, as detailed in 2.2 Torus – lighting, for windows (ref. 26).
While the hull of DL4 will be constructed using a high tension aluminium stressed skin, other equipment onboard will require high compression materials. Lunar ceramics, such as calcia (CaO), silica (SiO2 – glass), magnesia (MgO), alumina (Al2O3), and titania (TiO2), offer themselves for this purpose. Their resistance to heat and oxidation makes them suitable not only for many industrial processes onboard but also for much of the settlement maintenance equipment (e.g. 17 Life Support Systems). Their low thermal expansion levels are perfect for DL4’s space environment where wide ranges of temperatures are experienced. Such an environment also offers advantageous conditions to carry out the sintering of ceramics with the availability of large solar ovens and high vacuums, which lead to pristine surfaces and minimal impurities of oxygen or water.
Space also offers near perfect conditions for the manufacture of fibreglass. Lunar glass, which is optically superior to its terrestrial counterpart and readily available on the Moon’s surface due to a lack of ‘devitrification’ (decomposition by the chemical action of water in the environment), will prove an excellent source material for such fibre composites. The possibilities of containerless melting and high vacuum facilities on DL4 lend themselves to the processing of high purity glass fibres. Such fibre optic products will be laid internally, during construction, for communications and used externally on large communications satellite platforms. (Some of the materials required for these procedures could also be mined from asteroids, see 11 Industry.)
For the purposes of internal structural support, foamed glass beams could be easily produced and, in cases of high tension or compression, could be reinforced using asteroidal nickel-iron steel. Such strength improvement would lead to tensile strengths in excess of 344,827.6kPa (ref. 26), enabling the beams to be used for floor support and sub-floor water storage.