NASA Workshop on Granular Materials in Lunar and Martian Exploration

CONVENERS

• Allen Wilkinson,
• NASA John H. Glenn Research Center
• Philip Metzger,
• NASA John F. Kennedy Space Center

HOSTED BY

• John F. Kennedy Space Center

SPONSERED BY

• Army Research Office
• National Aeronautics and Space Administration
• KSC Spaceport Technology Development Office
• GRC Exploration Systems Division
• American Institute of Aeronautics and Astronautics

SCIENTIFIC ORGANIZING COMMITTEE

• Robert Behringer, Duke University
• James Jenkins, Cornell University
• Michel Louge, Cornell University
• Philip T. Metzger, NASA Kennedy Space Center
• Enrique Rame, NASA Glenn Research Center
• Allen Wilkinson, NASA Glenn Research Center
• David M. Cole, U.S. Army Cold Regions Research and Engineering Laboratory
• Jerome B. Johnson, U.S. Army Cold Regions Research and Engineering Laboratory

Purpose and Scope

For humans to explore the Moon and Mars, most mission scenarios require that we shall make use of in-situ resources. This requires us to understand the properties and mechanics of the extraterrestrial regoliths, to predict the behaviors of granular geomaterials in lunar and Martian environments, and to design technology capable of reliably controlling the various complex fluid flow regimes of these materials. Dealing with granular materials in an extraterrestrial environment, where we have limited experience and limited experimental access to the materials themselves, present a unique challenge to the human exploration of the solar system. This workshop will bring together scientists, engineers, and mission managers to identify the key challenges and the necessary research directions that must be pursued to answer them.

An example of in situ resource utilization (ISRU) is to make propellant for the return journey from Mars to Earth using carbon and oxygen from the Martian atmosphere and hydrogen from water ice excavated beneath the Martian surface. This would make a human-tended Mars mission more economically feasible since it avoids the excessive cost in lofting the propellant from the Earth’s surface and transporting it to Mars. Most of the relevant in-situ resources of the Moon and Mars are found in the regolith (the loose layer of sand and rocks covering the surface). Developing technology to work with these geomaterials is therefore of paramount importance to human exploration of the solar system.

Other related challenges are the need to excavate beneath the lunar and Martian surfaces for scientific objectives, and the need to control the high-speed blast of sand and microscopic grit when a rocket lands on the surface in the vicinity of other mission-critical hardware. The program is also considering ways to use the regolith in the construction of habitats and for radiation shielding.

Designing technology to work with the Martian or lunar regolith is challenging for several reasons. First, we have limited knowledge of the mechanics of the Martian regolith (more so than the lunar regolith) over the range of locations and seasonal conditions that are important to exploration, especially at the scale of depth beneath the surface required for ISRU. Robotic exploration of Mars is advancing our knowledge of the regolith, but effective planning of the robotic program requires that we know what are the specific questions to be answered and how we may design spacecraft to effectively answer them.

Second, predicting soil mechanics is difficult because there is no fundamental understanding of the physics – no physical law with the pedigree of the Navier-Stokes equation to predict how any granular material will behave. Geotechnical descriptions of terrestrial soils have traditionally treated them as a plastic continua using material parameters fitted to match the experimental behavior of the soil. This method provides predictive capability, but extrapolating the method to lunar and Martian conditions (atmospheric and subsurface gas inventory and pressures, ice inventory and micromechanical structure, and heterogeneous variability in a region of unknown geologic history) injects significant uncertainty into the fidelity of the predictions. Furthermore there are practical problems even in terrestrial civil engineering such as those related to scale-up, which make robust predictions difficult without practical experience in the relevant applications and environments.

Third, the mechanics of granular materials present a spectrum of unique technological challenges due to their self-organizing, fragile, and non-homogeneous flow behaviors. Various manifestations of these phenomena have long been known to industry and agriculture, including the frequent collapse of grain silos, the jamming of hoppers or other equipment, human death by burial in an unexpected slumping of material, and the inability to smoothly mix granular materials together. Many of these problems have come into investigative focus only during the past several decades, largely due to advances in computing power which have made it possible for the first time to simulate the internal state of granular materials to discover why they behave as they do. These internal state behaviors include jamming and arching, non-uniform convection and flow patterns, directional stress propagation, vibration-induced pattern formation, the heterogeneity of the stress field including the formation of percolating force-chain networks, auto-segregation or auto-stratification, and self-organized criticality. As a result, scientists and engineers from a wide variety of interrelated disciplines are actively using new theoretical, experimental and modeling techniques to understand these aspects of granular and soil physics and to apply their new advances into improved granular material technology. These disciplines include civil engineering (especially geotechnical), mechanical engineering, mining and excavation, soft condensed matter physics (and statistical mechanics), chemistry and chemical engineering, geology, planetary science, terrestrial soil science, and cold regions / permafrost science, among others.
This workshop will bring together a group of researchers from this spectrum of disciplines to identify the challenges and necessary research in granular and regolith mechanics to make lunar and Martian exploration successful.

Call for Abstracts

Abstracts are requested for contributed talks. Abstracts must consist of not more than 500 words describing the content of the talk and its relevance to the purpose and scope of the workshop. Abstracts shall be emailed in electronic format (doc or pdf file) to Philip.T.Metzger@nasa.gov by 12/31/04. Acceptance notification will be by e-mail on or before 1/10/05. Accepted speakers must register on or before 1/17/05.

Clearance Required for all Workshop Materials

You are responsible for obtaining the relevant clearance for materials that you publicly release at the workshop. This means that your abstract, Powerpoint or other presentation, overhead transparencies, oral presentation, paper copies, and any other medium, including all data contained therein, must be properly cleared through the procedures in effect at your university, company, or government installation. Materials must be reviewed for export compliance and potential intellectual property. All participants must provide appropriate documentation of such clearance to Melanie Chan, fax number 321-867-4446 – or e-mail a scanned copy of the signed documentation to Melanie.R.Chan@nasa.gov . For NASA KSC personnel this document must be the DAA, NASA Form 1676 “Document Availability Authorization”. Employees at other NASA Centers may provide the same form or contact your Center Export Administrator. Material belonging to any presenter and containing NASA-related, export-controlled information that has not been cleared for public release cannot be presented at the workshop nor included in the published proceedings.

Meeting Format

The workshop will occur over two days. The first day will consist of primarily invited overview talks and group discussions. The second day will consist of primarily contributed talks followed by final group discussions. If the response for contributed talks is very large, the overflow will be accommodated by a poster session on the second day (summarized by a rapporteur in order to facilitate completeness in the discussion sessions).

The conclusions drawn after the close of the second day’s discussions will be broadcast to the attendance list after the workshop and a report will be published and provided to NASA officials for serious consideration.

The preliminary agenda will be made available on the website.

Presenter Information

Contributed talks will be planned to take 10 minutes followed by an additional 5 minutes of discussion. Invited talks will be planned to take 20 minutes followed by an additional 5 minutes of discussion. Two overhead projectors plus a computer with a single LCD projector will be available to all speakers.

Meeting Location

The meeting will occur at the Kennedy Space Center in Florida. See the website ( http://weboflife.nasa.gov/regolith.htm ) for further information.

Contact Information

Philip Metzger

NASA / Kennedy Space Center

telephone: 321-867-6052

e-mail: Philip.T.Metzger@nasa.gov.