Flowability of lunar soil simulant JSC-1a

We have done a complete flowability characterization of the lunar soil simulant, JSC-1a, following closely the ASTM-6773 standard for the Shulze ring shear test. The measurements, which involve pre-shearing the material before each yield point, show JSC-1a to be cohesionless, with an angle of internal friction near 40°. We also measured yield loci after consolidating the material in a vibration table which show it to have significant cohesion (≈ 1 kPa) and an internal friction angle of about 60°. Hopper designs based on each type of flowability test differ significantly. These differences highlight the need to discern the condition of the lunar soil in the specific process where flowability is an issue. We close with a list—not necessarily comprehensive—of engineering rules of thumb that apply to powder flow in hoppers.