(340c) From Bouncing Space Probes to Toner Powders

Ever since the near-failure of the Philae lander of the Rosetta spacecraft mission in 2004, the behavior of Granular Materials (Bulk Solids) under conditions of low- or even microgravity has been an object of intense research scrutiny. Considering the planned future manned missions to the Moon and Mars, it is also likely to continue.

Due to the difficulty of actual experiments in microgravity, this work is so far mostly calculative and theoretical.

The applied stress towards a powder column is the most important parameter in the study of the flow (and non-flow) behavior of bulk solids, whereby the significance of the total applied force cannot be understated.

In the framework of the Mohr-Coulomb failure criterion applied normal stress is the key determinator of the behavior, often likened to temperature in soft matter rheology.

The key word here is applied stress, as the theory as well as the employed measurement techniques (Jenike or ring type shear cells) do not factor in artifacts that are contingent upon the powder’s own weight.

In this fashion a common problem is shared between space physics and chemical engineering as this leads to artifacts, especially in the measurement of bulk solid of high density such as metal powders.

Utilizing sub-fluidized system to selectively counteract gravity in a fluidization column and measured by a modern Rheometer, we aim to reconcile experimental data with published calculative data obtained by various model systems of different density.

In contrast using applied vacuum under the powder column we intend to simulate applied stress within the same system and compare it to shear cell data.