AstEx Microgravity Experiment: Simulating Asteroid Regoliths

AstEx is a microgravity experiment selected to fly on ESA's 51st Microgravity Research Campaign in November 2009. The experiment will investigate the dynamics of regolith on asteroid surfaces. Despite their very low surface gravities, asteroids exhibit a number of different geological processes involving granular matter. Understanding the mechanical response of this granular material subject to external forces in microgravity conditions is vital to the design of a successful asteroid sub-surface sampling mechanism, and in the interpretation of the fascinating geology on an asteroid. The AstEx experiment uses a microgravity modified Taylor-Couette shear cell to investigate granular flow caused by shear forces under the conditions of parabolic flight microgravity. It is intended to determine how a steady state granular flow is achieved in microgravity conditions, and what effect prior shear history has on the timescales involved in initiating a steady state flow in a granular material. Presented are the technical details of the AstEx experimental design with particular emphasis on how the team have designed the equipment specifically for the parabolic flight microgravity environment.

[1]  Shear transformation zone analysis of shear reversal during granular flow , 2008, 0802.1752.

[2]  W. Benz,et al.  Catastrophic disruption of pre-shattered parent bodies , 2004 .

[3]  Stationary state volume fluctuations in a granular medium. , 2005, Physical review. E, Statistical, nonlinear, and soft matter physics.

[4]  George Lake,et al.  Direct Large-Scale N-Body Simulations of Planetesimal Dynamics , 2000 .

[5]  Side effects of collisions: Spin Rate Changes, Tumbling Rotation States, and Binary Asteroids , 2002 .

[6]  D. Sears,et al.  MICROGRAVITY TESTING OF A SURFACE SAMPLING SYSTEM FOR SAMPLE RETURN FROM SMALL SOLAR SYSTEM BODIES. M. A. Franzen , 2004 .

[7]  William F. Bottke,et al.  Formation of asteroid satellites and doublet craters by planetary tidal forces , 1996, Nature.

[8]  Mario Nicodemi,et al.  Slow relaxation and compaction of granular systems , 2005, Nature materials.

[9]  Wolfgang Losert,et al.  Correlation between particle motion and Voronoi-cell-shape fluctuations during the compaction of granular matter. , 2008, Physical review letters.

[10]  J. Vilotte,et al.  Memory of the unjamming transition during cyclic tiltings of a granular pile. , 2005, Physical review. E, Statistical, nonlinear, and soft matter physics.

[11]  M. Stone,et al.  Starting to move through a granular medium. , 2008, Physical Review Letters.

[12]  Akira Fujiwara,et al.  Asteroidal surface sampling by the MUSES-C spacecraft , 2002 .

[13]  Heinrich M. Jaeger,et al.  Signatures of granular microstructure in dense shear flows , 2000, Nature.

[14]  R. M. Nedderman,et al.  Principles of Powder Mechanics. : Pergamon Press, 1970. 221 pp.,£3. , 1971 .

[15]  Wolfgang Losert,et al.  Transient and oscillatory granular shear flow. , 2004, Physical review letters.

[16]  Wolfgang Losert,et al.  Transient and steady-State Dynamics of Granular shear Flows , 2001, Adv. Complex Syst..

[17]  Eric I Corwin,et al.  Granular flow in a rapidly rotated system with fixed walls. , 2008, Physical review. E, Statistical, nonlinear, and soft matter physics.

[18]  D. Vokrouhlický,et al.  The Effect of Yarkovsky Thermal Forces on the Dynamical Evolution of Asteroids and Meteoroids , 2002 .

[19]  M. Louge,et al.  Towards a theoretical picture of dense granular flows down inclines. , 2007, Nature materials.

[20]  E. Ryan,et al.  Asteroid Impacts: Laboratory Experiments and Scaling Laws , 2002 .

[21]  D. Richardson,et al.  Modeling Cohesion in Gravitational Aggregates , 2008 .

[22]  Masahiro Toiya.  Onset of Granular Flows by Local and Global Forcing , 2006 .

[23]  W. Losert,et al.  Particle motion during the compaction of granular matter , 2008, 0802.0485.