Vibration-assisted granular flow under simulated lunar conditions: parabolic flight validation of lunar regolith feed system

Abstract Reliable transport of granular materials through hoppers presents significant challenges in reduced-gravity environments due to diminished driving forces and increased susceptibility to flow blockages. This study reports results from parabolic flight experiments evaluating whether vertical vibration can maintain continuous regolith flow under simulated lunar gravity and vacuum conditions. Eight parallel feed assemblies were tested inside vacuum chambers, spanning four outlet geometries ranging in diameter from 11 to 45 mm and hopper angles from 46.5° to 90°. Vibration was applied at frequencies of between 43 and 65 Hz with displacement amplitudes from 0.2 to 0.8 mm. Across 60 reduced-gravity parabolas comprising 480 individual experiments, continuous material discharge was observed whenever vibration was active, regardless of outlet geometry. When vibration was disabled, all configurations exhibited flow termination within seconds. Reactivating vibration promptly restored flow without manual intervention. A rotary pocket feeder at each hopper outlet provided proportional flow rate control, yielding mass flow rates of 0.3 to 1.0 g/s with a lunar highlands regolith geotechnical simulant. These results demonstrate that vertical vibration effectively prevents flow blockages in reduced gravity, establishing validated design parameters for regolith handling systems intended for lunar surface operations.