Evaluating and advancing scaling methods for reliable wheel mobility prediction in low-gravity environments

Predicting wheel mobility in low-gravity environments through Earth-based gravity tests offers a practical alternative to expensive parabolic flights and computationally intensive numerical simulations. However, an optimal scaling method for varying wheel speeds remains unidentified. This study systematically evaluated three scaling methods—Granular Scaling Laws (GSL), reduced-weight tests, and equal-mass tests—using Discrete Element Method simulations at three wheel angular velocities ( π / 10 , π , and 2 π rad/s). The methods were assessed based on their accuracy in predicting horizontal velocity, slip ratio, sinkage, and power consumption under free-driving conditions. GSL maintained errors below 5% across all conditions, while the equal-mass test showed velocity-dependent degradation with errors reaching 234% at high speeds. The reduced-weight test underestimated sinkage by over 100%, risking vehicle immobilization. An analytical framework employing an inertial number was developed to quantify soil flow characteristics, facilitating a comprehensive comparative analysis of the scaling methods. This analysis revealed that the equal-mass test inadequately captured dynamic flow phenomena, accounting for its velocity-dependent degradation. Conversely, GSL accurately reproduced soil flow characteristics under all conditions, enabling precise mobility predictions over a broad velocity range. These findings establish GSL as the most accurate and practical scaling approach for extraterrestrial rover mobility design and analysis. • Granular Scaling Laws predict wheel mobility within 5% across wide velocity ranges. • Reduced-weight test underestimates sinkage, increasing immobilization risk. • Equal-mass test loses accuracy as velocity increases, especially above π rad/s . • Inertial number analysis confirms GSL accurately reproduces movility and soil flow.