Measurement of the three-dimensional shape and size distribution of 17 lunar regolith simulants: Simulant shape and size inter-comparison and simulant shape comparison with Apollo 11 and Apollo 14 lunar regolith

Lunar regolith simulants are manufactured in order to provide a higher volume, much less expensive and more available source of material, compared to real lunar regolith material, with which to test various instruments and machines designed to operate on the lunar surface. The particle size distribution and mineralogy of these materials is engineered but not the particle shape, although particle shape does play an important role in many engineering applications. Thus, the three-dimensional (3D) shape of these materials has rarely been characterized and never compared to each other and to real lunar regolith material. The focus of this paper is to provide 3D shape and size distribution of 17 different simulants, use this data to compare these materials against each other and provide these data in a NIST database. Over 1.1 M particles are in this database, with their 3D shape stored as STL files. The particle size range considered is roughly 7 μm to 1 mm. With the recent publication of 3D characterizations of lunar regolith material from the Apollo 11 and Apollo 14 missions, these characterizations are also compared to equivalent data for the real lunar regolith material. Both mare and highland simulants are studied using graphical comparisons as well as size and shape figure of merit analysis. This kind of 3D characterization provides the information that new engineering manufacturing techniques will need to enable the engineering of particle shape for new lunar regolith simulants, since the ability to make particle shape measurements relevant to manufacturing and use is a prerequisite for any such engineering. This database can also serve as a source of “digital twins” or “virtual simulants” for modeling studies both of individual particle properties and of packed particle geometry and properties.