A paper describes a method of using microwave heating experiments on lunar simulants to determine the mechanism that causes lunar regolith to be such an excellent microwave absorber. The experiments initially compared the effects of sharp particle edges to round particle edges on the heating curves. For most compositions, sharp particle edged samples were more effective in being heated by microwaves than round particle edged materials. However, the experiments also showed an unexpected effect for both types of particles. Upon heating the sample surface above 400 °C, the sample experienced some sort of internal structure change that caused it to heat much more efficiently. This enhancement may be associated with the unique microwave volumetric heating that can produce a large temperature gradient within the sample leading to melting of some components at the center of the sample. This new effect that may also be happening in lunar regolith samples is probably the cause of the previously observed enhanced heating of a sample of lunar regolith. Properly designed microwave applicators could heat and solidify the lunar regolith to form roads and building blocks for structures needed on the Moon.
This work was done by Martin B. Barmatz and David E. Steinfeld of Caltech for NASA’s Jet Propulsion Laboratory. NPO-48895
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Method for Processing Lunar Regolith Using Microwaves
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Overview
The document titled "Technical Support Package for Method for Processing Lunar Regolith Using Microwaves" presents research conducted by Martin B. Barmatz and David E. Steinfeld from the Jet Propulsion Laboratory, California Institute of Technology. It focuses on the innovative use of microwave energy to process lunar regolith, the fine dust and soil found on the Moon's surface.
The research builds on earlier studies that indicated lunar regolith's exceptional ability to absorb microwave energy, which was initially thought to be due to the presence of nanophase iron. However, recent measurements suggest that this may not be the sole reason for the high absorption rates. The document outlines the objectives of the study, which include understanding the mechanisms behind this absorption and exploring the potential applications of microwave processing for lunar soil.
Key findings from the experiments indicate that dielectric heating of the regolith occurs at significantly faster rates compared to magnetic heating, particularly above temperatures of approximately 400°C. This rapid heating is associated with material property changes, such as melting or the formation of new compositions, which enhance the heating process. The reflected power behavior during these experiments also showed a notable increase above 400°C, indicating a significant reduction in power levels in the microwave cavity.
Figures included in the document illustrate the temperature versus time curves for dielectric and magnetic heating of lunar regolith samples, highlighting differences in heating rates for samples with sharper and rounder particle shapes. The results suggest that maintaining a constant power level in the cavity could allow samples to reach even higher temperatures.
The document emphasizes the potential of microwave processing techniques for in-situ resource utilization on the Moon, which could support future lunar missions and the establishment of a sustainable human presence. It also acknowledges the need for further validation of the findings with actual lunar regolith samples.
Overall, this research represents a significant step forward in understanding and utilizing lunar resources, with implications for both scientific exploration and practical applications in space technology. The document serves as a valuable resource for those interested in aerospace developments and the future of lunar exploration.
