Snow Micro Penetrometer Applications for Winter Vehicle Mobility

The U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) provides cold regions research and development in support of the U.S. military and the nation. For winter military operations this support includes vehicle mobility modeling over snow. Many factors relate to vehicle performance, fuel efficiency, and operation efficiency, including the vehicle specifications and the land surface conditions. Comprehending snow macromechanical characteristics—such as elastic modulus, stiffness, and strength—is critical in understanding how effectively a vehicle will travel over snow covered terrain. Vehicle instrumentation data (inertial measurement units and vehicle telemetry) and observations of the snow pack (both satellite and ground-based) are leveraged to improve the modeled index for winter vehicle performance. Currently, the available mobility models are physically-based and consider numerous factors related to cross country mobility such as slope, soil type, terrain strength, land classification, and vegetation. The algorithms related to the impact of snow, however, are driven by snow depth and bulk snow density alone. This research deployed a SnowMicroPenetrometer (SMP) whose capabilities were expanded to measure several types of snow, including virgin snow, vehicle tracked snow, and processed or groomed snow roads. The SMP high-resolution snow structural profiles show the value of the instrument as a tool for mobility studies. Correlation analysis was conducted between the SMP and Rammsonde penetrometer using median values from different snow types at a particular site. The data express a trend that rupture force, penetration force, density, strength, and ram hardness increases when the snow is deformed by the vehicles. Instrument modifications were assessed with recommendations made to further improve SMP performance for use in mobility studies.