Lunar Micro-Rover (LMR) Project Presentation 15 July 2008

1. NASA Manager Mark Leon LMR Co-Project Manager Ames Research Center (ARC) National Aeronautics and Space Administration CMU Manager Dr. Khalid Al-Ali LMR Co-Project Manager Carnegie Mellon Innovations Laboratory (CMIL) Carnegie Mellon University LMR NASA-Carnegie Joint Management Team (JMT) New Ventures and Communications Directorate (Code V)Strategic Communications Division (Code VC) Special Projects Branch (Code VCS)Collaborative Robotics Group (Code VCS-CRG) Lunar Micro-Rover (LMR) ProjectPresentation15 July 2008

2. Missions Primary Mission: Develop a system to simulate lunar gravity for simulation purposes Secondary Mission: Research and Develop technologies related to thermoacoustic power generation

3. Lunar Gravity Simulator (LGS)Goals • Simulate accurate lunar gravity on rover with a system to offset earth’s gravity • Make it fit in the lunar regolith box already standing behind N-226 • Allow complete rover mobility and account for variations in terrain

4. LGS-Mark I • Constant Force Spring • Teflon Sliders • 90° Brackets • PVC Rails • 8-Bearing Carriage

5. LGS-Mark IShortcomings • Slider did not account for non-uniformity of the regolith box • Longitudinal sliding would bind

6. LGS-Mark IIImprovements • Redesigned rail sliders • Allows for inconsistencies • All motion on bearing surfaces • Wall mounted rails

7. LGS-Mark IIImprovements • Redesigned Carriage • Handles torque moments on the longitudinal axis more effectively

8. LGS Experiments • Coefficients of Friction • μs ≈.401 • μk ≈.310 • Driving & Handling Tests • Laterally (For Now) • Treads throw regolith on top of the rover

9. LGS Experimentsμs • Inclined Board Test • Covered wooden board in regolith and placed rover on top • Lifted board to create an incline until rover slid • Repeated multiple times • Recorded the whole test on video • Used angles to find μs ≈.401

10. LGS Experimentsμk • Drag Test • Dragged rover on the ground with spring scale • Took data while wheels slid • Repeated multiple times • Recorded the whole test on video • Used forces to find μk ≈.310

11. Driving and Handling • Drove rover laterally inside simulator • Noticed acceptable handling • Turning made rover dig into regolith as opposed to turning on it • Regolith Problems • Threw regolith all over itself • Camera lens was covered after about a minute

12. Thermoacoustic Power • Thermoacoustic Effect • Temperature gradient causes spontaneous oscillation of the working fluid

13. Thermoacoustic Power • High potential • As the devices shrink, they can utilize a smaller temperature difference to produce power • FRG Thermoacoustics has made a MEMS generator capable of 600 W/m^2—three times as much as solar panels • Traditional generators can be miniaturized. O. Symko et al. have made resonators as small as .5x1” • Relatively simple to make • The stack can be nearly any material • Random fiber stacks are very easy to manufacture

14. Thermoacoustic Engine • Key Components • Heat Exchanger • Stack • Resonator • Transducer

15. Thermoacoustic Engine • Heat Exchangers • Must conduct heat extremely well • Need good thermal contact with the stack • Also should have large surface area to heat the fluid

16. Thermoacoustic Engine • Stack • Needs to have a high surface area • Must maintain large temperature gradient • Can be “random fiber” for simplicity

17. Thermoacoustic Engine • Resonator • Must have a high quality factor • Determines the frequency of oscillation • Should have the stack at an optimal location

18. Thermoacoustic Engine • Transducer • Converts acoustic energy to electrical energy • Most commonly a piezoelectric device at one end of the resonator • Produces AC current

19. Thermoacoustic Engine • Testing • Experimented with both half-wave and quarter-wave designs • Resonator was a steel ½” pipe • Stack made of Reticulated Vitreous Carbon (RVC), asst. porosities • Heat exchangers made of 100 ppi mesh

20. Thermoacoustic Engine • Results • Quarter wave generators produced no sound • Half wave generators did not produce appreciable voltage • However, the output of the piezoelectric material exhibited a voltage oscillation around zero with an amplitude of ~10-20 mV at approx. 0.5 Hz

21. Thermoacoustic Engine • Future testing • Improve thermal contact between components • Try different stack materials • Maximize actual temperature gradient across the stack

22. Citations • Thermoacoustic engines. Swift, Greg W. 4, October 1988, Journal of the Acoustical Society of America, Vol. 84, pp. 1145-79. • Miniaturization of Thermoacoustic Devices for Thermal Management if Microelectronics. Symko, Orest G. [ed.] Gian Piero Celata. Banff, Canada : s.n., 2000. Heat Transfer and Transport Phenomena in Microscale. pp. 335-338. • A Sound Way to Turn Heat into Electricity. University of Utah News Center. [Online] 2007. [Cited: July 18, 2008.] http://unews.utah.edu/p/?r=053007-1. • Design and development of high-frequency thermoacoustic engines for thermal management in microelectronics. Symko, Orest G., et al. 2004, Microelectronics Journal, Vol. 35, pp. 185-191. • Micromachined Stack Component for Miniature Thermoacoustic Refrigerator. Tsai, Chialun, et al. 2002. The Fifteenth IEEE International Conf. on Micro Electro Mechanical Systems. pp. 149-151. • Fellows Research Group. Energy for the New Millennium. FRG Thermoacoustics. [Online] November 17, 2006. [Cited: July 18, 2008.] http://www.io.com/%7Efrg/tar.htm. • Measurements with reticulated vitreous carbon stacks in thermoacoustic prime movers and refrigerators. Adeff, Jay A., Hofler, Thomas J. and Atchley, Anthony A. 1, July 1998, Journal of the Acoustical Society of America, Vol. 104. • Energy Conversion Using Thermoacoustic Devices. Symko, Orest G. Baltimore : s.n., 1999. Eighteenth International Conference on Thermoelectrics. pp. 645-648. • Natural Engines. Wheatley, John and Cox, Arthur. 8, August 1985, Physics Today, Vol. 38, pp. 50-58.