International Concrete Abstracts Portal

During the NASA 90-day study, in response to the President's statement on the space exploration initiative, the Jet Propulsion Laboratory conducted a study of potential astronomical observatories that could be situated on the lunar surface in conjunction with the lunar outpost. The scientific objectives were derived from the four NASA discipline management and operations working groups, several special workshops and symposia on lunar astrophysics, and the NASA Office of Space Science and Applications (OSSA). The overriding premise in selecting and defining the lunar observatories was that the moon must provide some unique advantage in performance, cost, or other significant parameter, such that the experiment could be executed better there than anywhere else. The unique properties of lunar siting include 1/6 gravity, a large stable platform, long continuous viewing times, and low nighttime temperatures. The four observatories were: a seven-element optical interferometer with a 1- to 2-km baseline; a seven-element submillimeter interferometer with coherent detectors and a 1-km baseline; a very low-frequency interferometer (ó 30 MHz) with 100 elements and a 200-km baseline on the lunar far side; and a gravitational wave detector with two 50-km arms, perhaps operating in conjunction with an earth-based gravitational detector. Advanced technology needs associated with the four observatories have been identified and include advances in optical delay lines and beam combiners, coherent heterodyne detectors, instrument cryogenic systems, and methods for construction on the moon, such as building foundations, trenching building roads, etc. In particular, the problems of construction and civil engineering commonplace on earth present a new class of problem for the lunar surface. The paper addresses some of these civil engineering needs and suggests precursor experiments that should be done to provide a firm basis for the construction of astronomical observatories on the moon.

Conventional structural engineering philosophy and experience can be inappropriate when it comes to designing structures for the moon. This paper illustrates the authors' adaptation of design philosophy for concrete, which involves changing the whole value system for this material. Far from being readily available, common, and plentiful, concrete will be an exotic and precious material on the moon. The use of concrete is proposed for such efficient structures as thin shell rather than the more common planar structures more suitable for earth. The structure containing one atmospheric pressure inside must be pressurized to resist such pressure, and a new value system must be derived.

Provides an overview of engineering studies performed in support of the Space Exploration Institute (SEI). Topics addressed include background on the SEI, lunar construction phases, lunar habitats, lunar oxygen, mechanical concepts, and lunar power. Although the topics do not relate equally to concrete construction, they do identify selected issues that must be addressed before a lunar outpost can evolve to the emplacement and operation phases. In these phases of lunar outpost development, maximum use will be made of native materials, such as lunar concrete.

This paper suggests establishing the applicability and manufacturing technique of GFRP, particularly dimethylisophtalate glass-filament rod. The use of GFRP reinforcement in lieu of conventional steel rods and wires has great potential for precast structural concrete elements. GFRP may be cheaper, lighter, and formed from materials found in abundance on earth and on the moon, namely silica (SiO2). GFRP can be manufactured with the same, if not higher, tensile properties of steel. If synergically composed with a plastic carrier, a new science in construction and structural analysis could be born. No doubt remains that lunar soil is cementitious. Rocks for aggregate and silica are also abundant on the moon. Heavy fabricated steel rods are counterproductive for transport to the moon. Glass fibers fabricated on the moon have great potential. Permanent settlement/habitats on the moon are within the realm of possibility and may be considered immediate projects. Therefore, the idea of using local materials is appropriate within the concept of a third phase of permanent underground reinforced concrete construction facilities, the first being the Apollo landings and the second a temporary above-ground lunar establishment yet to come. This analysis could lend itself not only to permanent reinforced concrete structures on the moon, but to any other planet where silica is abundant and cement could become a local product, through refining and reducing appropriate local ores. Manufacture of glass-fiber filaments is incomparably cheaper than steel. Additional research, at a later date, will encompass the application of pre- and post-tensioned GFRP reinforcements, using the same structural form elements. This paper proves the positive applicability of GFRP as reinforcement for precast concrete elements.

An important aspect of lunar concrete production will be the production of lime (CaO) from lunar rocks. Chemical and thermodynamic data show that lime could most easily be distracted from abundant lunar anorthite (CaAl2Si2O8) the major mineral in the anorthositic lunar highlands. If fluorine gas, produced on site by electrolysis of molten NaF, is used as the extracting agent, oxygen, silicon, and aluminum can be recovered at the same time. Of these, oxygen is likely to be the most valuable product. Lime is recovered from fluorite, CaF2, by reaction with soda, Na2O; the resulting NaF is recycled into fluorine production immediately before use. No fluorine gas is transported or stored in this process; it is used up as soon as it is made.