ISRU THERMAL-DRIVEN PROCESSES ON INTERPLANETARY SURFACES AND CHARACTERISTICS ON PRODUCTION OF COMMODITIES
Dominguez, Jesus A.
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Extraterrestrial In-Situ Resource Utilization (ISRU) is a primary area of interest to enable successful exploration, mining, and human settling in space missions. Native extraterrestrial conditions, such as vacuum conditions and low gravity are challenging as their effects on workable-scale ISRU operations are basically unknown. This dissertation research work studied three thermal-driven properties on JSC-lA lunar regolith simulant at pilot-plant-scale under vacuum (a native ambient condition on the moon and asteroids): (1) gasification and decomposition of regolith's components that have the potential of generating gaseous oxygen, metals, and alloys without the necessity of terrestrial precursors, (2) vacuum void formation during the regolith sinter-melt transition that imposes new design and operation considerations on regolith melting processes including gasification and decomposition stated in (1) as the melt expands due to the void formation within the melt's core, and (3) thermal upwards migration in uniformed thin-film pattern of the regolith melt that, as in the case of vacuum void formation phenomenon, also imposes new design and operation considerations on regolith melting processes including gasification and decomposition stated in (1) as the melt migrates along the sample receptacle's wall removing sample originally housed in the receptacle. Gasification and subsequent decomposition of some JSC-IA's components yielding gaseous oxygen was proved by direct measurement via Residual Gas Analyzer (RGA) analysis on the vacuum line and Scanning Electron Microscopy - Energy-dispersive X-ray (SEM/EDX) analysis on the melt sample. Vacuum void formation on the JSC-IA's sample core during the sinter-melt transition was experimentally observed without any indication of degassing causing the voids, as RGA readings did not indicate H2O, CO2, CO, 02, 03 or other 100-AMU gas; as in experimentally observed silicate melts, vacuum voids in JSC-1 A sinter-melt transition phase seem to be dictated strongly by the surface tension. Thermal upwards migration phenomenon on JSC-IA's melt also is formulated as a thermal Marangoni effect in which temperature gradients within the melt's bulk and along the crucible's wall yield the surface force large enough to supersede the gravitational force and yield the upwards thin-film migration. As far as the author knows, upwards thermal migration of JSC-IA (or other lunar regolith simulant) melt under vacuum has not been reported in the literature. This thermal migration capability of the JSC-1 A melt revealed in this dissertation work presents novel and valuable potential ISRU applications without the necessity of terrestrial precursors as the migration occurs evenly in thin-film pattern; among these applications are 3D printing feedstock, film coating, manufacturing of micro and MEMS devices, and separation and purification of valuable solid crystals including silicon. As the temperature distribution profile on the melt cannot be directly measured since the melt sample is housed inside a vacuum thermal chamber, a rigorous thermal mathematical model was developed and validated ( using experimental temperature values along the chamber's surface) to allow the determination of the temperature distribution profile within all elements inside the thermal chamber, including not only the melt sample but also the crucible housing the sample, the crucible holder, and the porous alumina block used inside as internal insulation. Additionally, a second mathematical model was developed and applied to verify the Marangoni effect on melt samples with properties similar to the JSC-1 A melt. The formation of the meniscus on the bulk-wall-vacuum surface interface and an incipient melt migration on the wall experimentally observed and documented were reproduced by the model.