Sintering lunar regolith pellets: a comparison of four samples from Apollo 11, 15, and 16

Lunar regolith sintering is proposed as a technique to produce consolidated objects on the lunar surface from locally sourced materials. Understanding the sintering behaviour of real lunar regolith is necessary to optimise this process, however, due to the precious nature of samples it is rare for material to be allocated for such destructive studies. This paper describes the sintering of eight 0.5 g pellets from four Apollo regolith samples (10084, 15601, 60501, and 67461), selected to examine the compositional differences between mare and highland material, as well as the differences due to sample maturity. All samples were sintered with incrementally increasing temperatures; x-ray computed tomography examination of the pellet internal structure was used to monitor sintering progression and showed final porosities of 19–31 %. The mare regolith was well sintered between 1120 and 1140 °C, approximately 80 °C lower than the highland samples, which required 1200–1215 °C, excluding two samples that experienced minor oxidation. Variation in the sintering temperature was shown to be related to both composition and sample maturity, with the particle size having more influence than glass content, based on the data presented. X-ray diffraction and scanning electron microscopy were used to examine the mineralogy, showing no significant changes after sintering. These results show that real lunar regolith sinters at temperatures comparable to lunar regolith simulants sintered under the same conditions. This work represents the first detailed examination of sintering real lunar regolith.