US Patent 8656760 Impact penetrometer systems for characterizing soil properties

A dual aerial-drop penetrometer system includes a high-velocity (>30 m/s) penetrometer aerial unit combined with a low-velocity (<10 m/s) penetrometer aerial unit. The primary penetrometer is formed as an outer shell having the secondary penetrometer received in telescoping fashion within, which is ejected by a spring ejection mechanism upon impact of the outer shell. Both penetrometers provide deceleration information as they penetrate the soil of interest. The data from the two penetrometers, after analysis, can be used to assess soil strength as well as trafficability for the deployment of remotely-controlled vehicles, for example.