Computational Modeling and Experimental Microwave Processing of JSC-1A Lunar Simulant

Microwave heating is a potential method for mitigating dust issues and creating solid regolith structures, such as landing pads, on the moon, Mars, and other extraterrestrial bodies. The advantage of using microwave heating is that regolith has the potential to be directly heated in situ. A computational model was developed that predicts the heating behavior of a lunar simulant, JSC-1A, using various methods for applying microwave energy. The efficiency of microwave heating depends on the properties of the materials. Dielectric properties are used to characterize a material’s microwave behavior, which is temperature and frequency dependent. Obtaining a variety of actual regolith samples for dielectric characterization can be challenging, which is why simulants and computational models were developed. This work used lunar simulant JSC-1A for dielectric characterization, microwave-processing studies, and computational modeling, inasmuch as this simulant is available in large quantities and has been extensively studied. The dielectric properties of JSC-1AC (a coarse sizing of JSC-1A) were previously measured at 2.45 GHz as a function of temperature up to the melting point. Only room-temperature measurements were available for actual lunar regolith, which were comparable with JSC-1AC at low temperatures. An experimental design and a computational model were developed to study surface-only heating using microwaves on a deep bed of powder. Heating was performed in a 2.45-GHz, 6-kW microwave chamber, in an argon atmosphere to avoid oxidative changes to the simulant powder on heating. The use of microwaves for surface-only heating on deep beds of simulant powder was demonstrated. Modeling used finite-element and finite-difference methods to calculate the electromagnetic and thermal heat development, using the dielectric properties of JSC-1A. The heating patterns obtained from the computer model were compared with microwave-heating experiments. The model was adjusted to achieve close approximations of JSC-1A microwave heating using different heating scenarios. The geometry of heating patterns and range of temperature agreement between the model and experimental methods demonstrated a good representation of JSC-1A microwave-surface heating.