Granular Materials and Risks in ISRU

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Granular Materials and Risks in ISRU

• R. Behringer and R. A. Wilkinson
• Duke University and NASA Glenn Research Center

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Outline

• Risks of handling granular materials
• Basic properties of granular materialswhy is
  there a problem with predictability?
• What can granular research deliver?

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Practical ProblemsDense Granular Materials

• Commercial granular systems operate at only 63
  of design (Rand Corp. Study, Rept.
  R-3216-DOE/PSSP, 1986)
• Granular devices fail 100 to 1000 times more
  often than other building structures (J. Eibl,
  1984)
• Examples

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Some Examples of Granular Catastrophes
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Catastrophes, Continued
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Catastrophes, Continued
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Relevance to Martian and Lunar Exploration

• Rovers and other vehicles must negotiate
  uncertain terain
• Mining for essential life support materials (e.g.
  water) must function without fail
• Landings, including effects from rocket exhaust
  depend critically on soil conditions

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ExamplesRovers in the News
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Rovers in the News
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Rovers in the News
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Complications of Martian soil
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Some Basic Properties of Dense Granular Materials

• Forces are carried preferentially on force chains
• Deformation leads to large spatio-temporal
  fluctuations
• Preparation history of granular samples matters a
  lot
• Fluctuations are an intrinsic part of granular
  flow and responseand not generally included in
  models of dense granular materials

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Example of Force ChainsShear Experiment
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Force chains evolve and break under vehicles
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Example of Stress Fluctuations
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Statistical Aspects of Granular Fluctuations Is a
Crucial New Element
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Conclusions

• Handling and controlling granular materials is
  essential for lunar or Martian exploration
• Reliable predictive descriptions are currently
  lacking
• A key insight is the need to include statistical
  components in the description (of dense granular
  materials)
• Important goal obtain predictive models that
  will include statistical effectsand hence allow
  reliable predictions of granular behavior for
  extraterrestrial exploration.