International Concrete Abstracts Portal

The age of space exploration is already here and it appears likely that, in the next 20 years, there will be permanent bases on the moon. Therefore, it is incumbent upon engineers designing lunar structures to become knowledgeable about the peculiar effects of gravity and relativity under extraterrestrial conditions. The purpose of the paper is to present a review of Newtonian physics in light of Einstein's special and general theories of relativity. In particular, Newton's classic laws of motion and gravitation are compared with modern concepts of space-time, time dilation, length contraction, equivalency principle, and other interesting aspects of relativity.

The United States Air Force Academy's Engineering 410 class, Spring 1989, tested the feasibility of using concrete as a lunar construction material. This was a continuation of two previous semesters' effort. Concrete specimens were tested by combining different cement types, mixing environments, and additives to determine their effects on strengths and other engineering properties of the specimens. Using 5 different variables, a total of 80 possible combinations existed. The group used a D-optimal design with 18 possible combinations to build a prediction equation to optimize the concrete design mixture. Confirmation tests were conducted on the optimal design and compared with the mathematical algorithm prediction. The results demonstrate the power of this approach in experimentation for concrete applications.

The recently established Lunar/Mars Program Office at Johnson Space Center is studying options that include construction of lunar outposts in the early twenty-first century, and subsequent structures for industrial operations. Major industrialization on the moon cannot occur without access to lunar resources. Construction of such structures as large pressurized habitats, launching facilities, lunar surface transportation systems, and liquefied oxygen storage tanks requires enormous volumes of materials. Experiments sponsored by the National Aeoronautics and Space Administration (NASA) and carried out at construction technology laboratories show the following: cements can be made from lunar anorthite and basalt; concrete made with lunar soils as aggregate has strength exceeding 10,000 psi; and a dry mixture of cement and aggregate wetted by injected steam will simplify concreting procedures and minimize needs for water and heavy equipment. In addition, a preliminary analysis of a prestressed precast concrete structure measuring 120 ft in diameter and 72 ft high shows that a properly designed concrete structure can confine atmospheric internal pressure. This project further investigates the effect of lunar temperature extremes on the behavior of precast concrete panels during the construction period. The major work involves calculations of heat flow in concrete panels exposed to the sun on the lunar surface and thermal stresses in the panels caused by the transient heat flow. Computer programs were written for the computations and results are presented.

Lunar Concrete is the exciting new symposium volume which explores the production and use of concrete on the moon. Contained within 20 technical papers from well-known authorities on lunar concrete are details on lunar base construction, use of lunar resources, lunar concrete formulation, forming and placing lunar concrete, reinforcing lunar concrete, and environmental effects of lunar concrete, optimizing lunar concrete and much more. It may at first seem outrageous that concrete could be considered as primary material of construction for use on the Moon. However, a small group of scientists and engineers, many of them represented in this collection of papers, have persevered in examining this outrageous premise. Most, perhaps all, of the materials needed to make concrete are naturally present on the lunar surface. Although they have to be extracted and transformed, the energy required to do that, and probably the cost, is much less than that which would be required to bring the same quantity of material from the Earth to use on the Moon. The technology for utilizing these natural materials of the Moon would appear to be straightforward modifications of techniques that have been developed for terrestrial applications. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP125

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.