Characterization & Modeling of Spacecraft Regolith Interactions

Transcription

1 Characterization & Modeling of Spacecraft Regolith Interactions Technical Development Start date: 10/01/2012 Technical Development End date: 01/31/2016 Final Technical Report submission date: 2/17/16 Team Leads: José Andrade California Institute of Technology Brian Trease Jet Propulsion Laboratory/University of Toledo Karl Iagnemma Massachusetts Institute of Technology

2 Table of Contents I. Technical Development List of Participants II. III. IV. Executive Summary a. Goal of program b. Key areas of accomplishment Introduction a. Initial KISS study and how opportunity emerged b. Scientific motivation and opportunities c. Technical motivation and opportunities Outcomes of the technical development program a. Results of the technical development program b. Papers, published work, presentations to important organizations resulting from technical development program V. Conclusions VI. Acknowledgments 2

3 I. Technical Development Team Leads and List of Participants Jose Andrade, Caltech Professor and Campus PI Brian Trease, University of Toledo Professor and JPL PI Karl Iagnemma, MIT Researcher and Co-Investigator Dan Arthur, Caltech/JPL Postdoc (former) Aaron Buysse, JPL Summer Intern Julie Castillo-Rogez, JPL Research Scientist Ryan Hurley, Caltech Graduate Student (former) Michael Lamb, Caltech Professor Jason Marshall, Caltech Postdoc Chris Miller, JPL Summer Intern Carmine Senatore, MIT Research Scientist (former) Leslie Timms, JPL Summer Intern Ivan Vlahinic, Caltech/JPL Senior Postdoc (former) II. Executive Summary a. Goal of program In the coming years NASA and JPL will be investigating geomaterials and regoliths on multiple celestial bodies including asteroids and Mars. The goal of this study was to investigate the interactions of these materials in the microgravity environments that will be encountered and to enhance our current understanding of regolith strengths with applications to future space mission plans. b. Key areas of accomplishment Experimental apparatus development and implementation: The xterramechanics team successfully completed the design and implementation of the experimental device shown in Figures 1 and 2, in time for the flight in the Fall of Figure 1 Passive earth pressure experimental device for micro gravity experiments. 3

4 Figure 2 Sand compression chamber on experimental device. Reduced gravity data collection: The team successfully deployed the experimental equipment on a Zero-G Corporation Boeing 727 microgravity flight in the Fall of 2016, see Figures 3 and 4. Data was collected on 3 Martian, 2 Lunar, and 20 zero gravity parabolas. This comes after an extensive development cycle in coordination with a previous reduced gravity flight. F i Figure 3 Caltech-JPL-MIT team members with other researchers at Zero-G Corporation headquarters following a 2013 test flight. 4

5 Figure 4 Caltech-JPL team members in front of the 727 before embarking on the 2015 flight. Strength parameter characterization (friction angle): Preliminary analysis of the data has captured the friction angles for a coarse, uniformly graded, un-confined sand at Earth, Mars, and Lunar gravity levels. An example of the internal friction angle captured using digital image correlation (DIC) is shown in Figure 5. The results show the peak friction angle to be independent of gravity level, see Figure 6. Figure 5 Calculation of internal friction angle and classical log-spiral failure at Lunar gravity. 5

6 Figure 6 Peak internal friction angle with 95% confidence interval of estimated value Strength parameter characterization (angle of repose): An additional analysis of the data using video from the experiment shows that the angle of repose (see Figure 7 for an example) for the chosen regolith simulant is independent of the gravity level, see Figure 8. Figure 7 Calculated angle of repose on left side of pile at Lunar gravity. 6

7 III. Introduction Figure 8 Angle of repose with 95% confidence interval of estimated value. Development of video of experiment for public viewing (in progress): The team successfully captured all aspects of the experiment in preparation for and on the reduced gravity flight. This footage is currently being developed into a video short about the experiment and its scientific merit for distribution to the public at large. a. Initial KISS study and how opportunity emerged This study emerged as a result of Greg Davis and Randel Lindemann s encouragement to J.E. Andrade to initiate a workshop on Terramechanics issues to address mobility challenges (after MER being stuck on Martian soils), as well as other physical interactions ranging from landing to sampling. b. Scientific motivation and opportunities The peak internal friction angle of a soil is direct measure of the strength of the soil. Understanding this property in reduced gravity environments has a direct connection to soil penetration experiments currently planned to occur on Mars and on an asteroid in the near future. Additionally, a complete understanding of the soil strength properties, of which the 7

8 internal friction angle is one important aspect, is required before any sort of habitat design can be completed for future Mars manned explorations. The team s successful investigation of this strength measure builds upon existing knowledge of regolith properties and allows the team to pursue related opportunities to characterize other aspects of regolith strength parameters. c. Technical motivation and opportunities The technical aspects of designing and conducting experiments on microgravity flights are quite challenging. The team successfully overcame these challenges to conduct experiments that had not occurred in this environment before. The team looks forward to future opportunities to utilize the technical knowledge gained in this research program for conducting enhanced experiments in reduced gravity environments. IV. Outcomes of the technical development program a. Results of the technical program The technical program resulted in a unique, previously uncharacterized set of soil strength parameters at microgravity environments. These results will help in the development of future NASA and JPL plans and provides enhanced insight into geomaterial experiments currently planned to occur on an asteroid and on Mars. b. Papers, published work, and presentations Published papers: Vlahinic, Ando, Viggiani, Andrade (2014). Towards a more accurate characterization of granular media: extracting quantitative descriptors from tomographic images. Granular Matter 16, F. Zhou, R.E. Arvidson, K. Bennett, B. Trease, R. Lindemann, P. Bellutta, K. Iagnemma, C. Senatore (2014). Simulations of Mars Rover Traverses, J. of Field Robotics, Volume 31, Issue 1, pages , January/February 2014 C. Senatore, M. Wulfmeier, I. Vlahinic, J.E. Andrade, K. Iagnemma (2013). Design and implementation of a PIV method for analyzing running gear-soil interaction, Journal of Terramechanics 50, I. Vlahinic, J.E. Andrade, E. Ando, and G. Viggiani, From 3d tomography to physics-based mechanics of geomaterials (2013). Conference Proceedings, ASCE International Workshop in Computing in Civil Engineering, Los Angeles, CA. Top 3 paper award. 8

9 Papers Under Review / In Preparation: Vlahinic, R. Kawamoto, J.E. Andrade, E. Ando, and G. Viggiani (2014). Level set bridge: From computed tomography to grain-scale mechanics of geomaterials. Acta Geotechnica. In review. J. Marshall, J.E. Andrade, D. Arthur, R. Hurley, K. Iagnemma, C. Senatore, B. Trease, I. Vlahinic (2016). Investigation of friction angles and shear banding in reduced gravity environments. In preparation. Presentation / Conferences: D. Arthur, C. Senatore, I. Vlahinic, R. C. Hurley, K. Iagnemma, and J. E. Andrade. Fundamental characterization of microgravity geomechanics. International Planetary Probe Workshop, Pasadena, CA, USA, June, Vlahinic, J.E. Andrade, E. Ando, and G. Viggiani, From 3d tomography to physics-based mechanics of geomaterials. Conference Proceedings, ASCE International Workshop in Computing in Civil Engineering, Los Angeles, CA, June, J. E. Andrade and KW Lim, Modeling failure at the grain scale: Critical State, Complas XII, XII International Conference on Computational Plasticity, Fundamentals and Applications, Barcelona, Spain, 3-5 September, KW Lim and JE Andrade, The granular element method: From tomographic data to discrete computations, EMI 2013 Engineering Mechanics Institute Conference, Northwestern University, Evanston, IL, USA, August 4-7, KW Lim and JE Andrade, The granular element method: From tomographic data to discrete computations, SES 50th Annual Technical Meeting and ASME-AMD Annual Summer Meeting, Brown University, Providence, RI, USA, July 28-31, Vlahinić, J. Andrade, E. Ando, G. Viggiani. From tomography to physics-based mechanics of porous media. ASCE Int. Workshop on Computing in Civil Engineering, Los Angeles, CA, July V. Conclusions The team successfully conducted an important regolith strength experiment in reduced gravity environments. The analysis of the results from this experiment provides important technical and scientific clarity to regolith strengths. The knowledge gained from this program will directly benefit current and future NASA/JPL missions in the solar system. VI. Acknowledgements We would like to acknowledge the encouragement from Dr. Greg Davis and Randel Lindemann to do this study. Also, we thank Prof. Ravi Ravichandran who was the cognizant member of the Keck Institute for Space Studies steering committee during our study. We thankfully acknowledge the support of Prof. Tom Prince and Michele Judd during our study their encouragement and continuous support for our project was key to our success. Finally, we would like to acknowledge the generous support of the Keck Foundation for providing the funds that made this study possible. 9