A terramechanics-based model for maximum-thrust prediction of Archimedean screw propulsion in low-cohesion terrain

A physics-based terramechanics model is developed for predicting the maximum propulsion force of a single Archimedean screw traversing granular, low-cohesion soil. Building on classical grouser wheel-soil shear theory, the model applies the Mohr–Coulomb shear-failure criterion to the screw-soil interface to obtain a closed-form expression for the longitudinal and transverse forces generated as the screw displaces the soil. A geometric analysis relates the screw flight-soil contact area to the screw’s rotation angle, sinkage depth, and flight geometry, providing the contact area required by the force model. The model is validated employing a custom test bench that measures the forces produced by additively manufactured screws of three distinct geometries moving at constant speed through Mojave Mars Simulant, a well-characterized granular medium. The predicted forces agree with experiment to within 10% for both the longitudinal and transverse components across all tested geometries. By linking soil shear properties and screw geometry to thrust in closed form, the model provides a practical basis for design, performance estimation, and future model-based control of screw-propelled off-road, planetary, and amphibious vehicles, for which conventional wheeled or tracked locomotion is poorly suited.