Wave velocity measurement in granular materials under micro-gravity

Experiments were conducted at NASA Glenn Research Center on the 2.2 second drop tower facility to measure velocities of P and shear waves using piezoelectric sensors. A large amount of interesting data was generated, which showed a clear dependence of wave velocities on gravity. The measured wave velocities can be used to characterize mechanical properties of granular materials. This method offers a promising technique which is light-weight, non-intrusive, reliable, and continuous for monitoring performance and determining properties of granular materials under a wide range of gravities. Potential applications in space flight and surface exploration on the moon and Mars are discussed.