International Concrete Abstracts Portal

In the lunar environment, the use of solar thermal energy has obvious advantages over any combustion or electrical furnace for driving high-temperature processes. However, extremely high temperatures, in the range of 1700 to 2000 C, will be necessary to produce cement from lunar minerals and will, in turn, require very high levels of solar flux concentration. Such levels can only be achieved in practice with some form of ideal or near-ideal nonimaging concentrator that can approach the maximum concentration permitted by physical conservation laws. In particular, very substantial gains in efficiency can be generated through the incorporation of a properly designed ideal or near-ideal nonimaging secondary concentrator in a two-stage configuration with a long focal ratio primary concentrator. A preliminary design configuration for such a high-flux nonimaging solar concentrating furnace for lunar applications is presented. It employs a tracking heliostat and a fixed, off-axis, two-stage concentrator with a long focal length utilizing a nonimaging trumpet or CPC-type secondary deployed in the focal zone of the primary. An analysis of the benefits associated with this configuration employed as a solar furnace in the lunar environment shows that the thermal conversion efficiency can be about 3 to 5 times that of the corresponding conventional design at 2000 C. Furthermore, this configuration allows the primary collecting aperture to remain unshaded by the furnace or any associated support structure.

Presents the concept of Moonbase #1--its objectives, financial structure, facilities, functions, and scientific/engineering merits. In accordance with a Florida state goal of encouraging commercial enterprise, a consortium of corporations is in the proce

Effects of a vacuum environment on properties of hardened mortar made with cement-based materials are discussed. In this study, mortar specimens were exposed to a vacuum environment after various water curing periods. Several characteristics of the specimens, such as weight, strain, porosity, and strength, were measured before and after the vacuum exposure. A significant water loss and shrinkage strain were observed in tested specimens after specific vacuum exposure. Therefore, some measures are required to prevent shrinkage-induced cracks. In some cases, strengths for some vacuum-exposed mortar specimens were higher than water-cured companion specimens. Based on these experimental results, possible applications of concrete on the moon are recommended in this study.

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.

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.