Pneumatic Sampling in Extreme Terrain with the Axel Rover

1. Pneumatic Sampling in Extreme Terrain with the Axel Rover Yifei Huang. 8.23.12 Frank W. Wood SURF Fellow

2. Overview • Motivation • Pneumatic Sampling • Concept, and feasibility • Design & Testing • Nozzle • Cyclone • Sample Container • Pressure Container • Instrument Deployment • Conclusions

3. Sampling in Extreme Terrain • Satellite images suggest liquid brine flow • Spectroscopy images – negative results for water • Difficulties in sampling • Newton Crater: 25-40 degree slopes • MER:15 degree slopes • Curiosity: 30 degree slopes • Solution • Axel rover: vertical slopes Figure: http://mars.jpl.nasa.gov/. Sources: http://ssed.gsfc.nasa.gov/sam/curiosity.html, http://usrp.usra.edu/technicalPapers/jpl/HooverMay11.pdf

4. The Axel rover DuAxel rover Traversing cliffs Instrument deploy Goal: Develop a sampling system on Axel

5. What is pneumatic sampling? • 1. Release pressurized air • Actuator opens and closes a cylinder of pressurized air • 2. Air flows down the outer tube of the nozzle • 3. Air enters inner tube, carrying soil with it • Nozzle is already embedded in dirt • Up is the path of least resistance • 4. Soil and air flow up into sample container Figure: Zacny et al. (2010)

6. Why Pneumatics? • Fewer moving components, low number of actuators, less risk for failure • Closed tubing: low instrument contamination • Energy efficient • A small amount of air can lift a large amount of dirt • 1 g of gas lifted 5000g of soil [Zacny and Bar-Cohen, 2009] • Easier soil transportation

7. Design: Nozzle • Round #1 Nozzle #2 Soil Level Nozzle #3 Nozzle #1

8. Design: Nozzle • Nozzles built on the 3D printer (ABS plastic) • Tests with loose sand (400um size) • 25psi air was released for 2 sec

9. Design: Nozzle • Round #2 Sand: Dirt: Nozzle #4 Nozzle #5

10. Design: Cyclone Separator • Used to separate air and soil • Dusty air will enter tangential to cyclone • Larger particles have too much inertia • Hit the side of cyclone and fall down • Smaller particles remain in the cyclone • Pushed up into the Vortex Finder by pressure gradient Vortex Finder Cylindrical portion Conical portion Small Particle Large Particle Design by Honeybee Robotics Figure: DB Ingham and L Ma, “Predicting the performance of air cyclones”

11. Design: Sample Container • Objective: Minimize actuation with springs Concept: Design: Cyclone Sample Container Spring

12. Design: Instrument Deployment • Second 4-bar linkage attached to original 4-bar • Motion of 2 4-bars are coupled • Advantages: No actuator on deployed plate Nozzle is attached here

13. Benchtop test stands • Instrument deploy • Sample Caching

14. Design: Pressure Container

15. Benchtop Test • Tests with loose sand (400um size) • 25psi air was released for 2 sec

16. Contamination • In sand • Weighed cyclone, tubing, and nozzle before and after tests • Negligible mass: ~0.2% of lifted mass remained in cyclone/tubing/nozzle • In dirt • Soil is stuck inside nozzle and cyclone • Cyclone: 50-300% of lifted mass • Nozzle: 50-150% of lifted mass

17. Effects of Pressure • Tests with loose sand (400um size) • Air from wall was released for 2 sec

18. Conclusions • Pneumatics is feasible • Successfully acquired 2g of soil • Improvements needed: • Acquiring moist soils (dirt) • Taking multiple samples • Placing system inside Axel

19. Acknowledgements • Kristen Holtz, co-worker • Funding: • Keck Institute for Space Studies • Caltech Summer Undergraduate Research Fellowship (SURF) • Mentoring: • Melissa Tanner, Professor Joel Burdick, Caltech • JPL Axel Team • Kris Zacny, Honeybee Robotics • Prof. Melany Hunt, Prof. Bethany Elhmann • Paul Backes, Paulo Younse, JPL