Spark plasma sintering and optical characterization of lunar regolith simulant

To satisfy the essential needs, including energy requirements, for human and robotic space explorations on planetary objects like Moon, Mars and asteroids, the proper exploitation of resources available in-situ represents a crucial issue. Along this line, the present work investigates the potential of a sintered lunar regolith simulant (JSC-1A) for possible solar energy harvesting and thermal energy storage applications. Regolith simulant powders are first consolidated by Spark Plasma Sintering (SPS) at 700 and 900 °C to produce bulk samples with different relative densities, i.e. 86 and 98%, respectively, and surface porosities. Negligible changes from the compositional point of view are induced by SPS at 700 °C, whereas a decrease of the original glassy phase content is observed when operating at 900 °C. The optical properties of sintered samples and pristine regolith powders are compared, considering the spectral absorptance/emittance, the integrated solar absorptance and the integrated thermal emittance estimated in a temperature range representative for the ISRU application, i.e. from 100 to 1300 K. We found that sintering changes the optical properties of regolith in a process-dependent way, with an increased solar absorptance and thermal emittance shown by sintered pellets with respect to pristine powders.