30 on rock samples cored by the integrated corer reflect the rapidly-repeating strike pattern. A variable strike  pattern will erode the rock more efficiently.  The performance and life of the coring bits can definit ely be improved. A bit design with an asymmetrical  tooth spacing arrangement would also help to avoid a rapidly-repeating strike pattern. Other cutting teeth geometry and material variations could be investig ated to help address the robustness issue since the  basic bit configuration is defined.  The containment sleeve concept was demonstrated to be effective along with the rear exit path of the  contained sample. The eccentric core  break-off/retaining feature likewis e worked successfully. However,  more statistically significant testing must be done to  determine how well these mechanisms perform over  time with varied rock materials.  A mass goal of less than 5 kg was established wh en requirements were re-baselined early in the  program. The final configuration wa s significantly under this goal, the corer weighing 2.5 kg without  mounting features. This leaves considerable room for future improvements which could include increased margins (though the motors in particular are currently oversized), and additional functionality such as motorized tool change, additional spare bits or bits for other functions, etc. The low mass also potentially  reduces strength and stiffness require ments for the robotic arm or other mount device, resulting in further  mass savings. Depending on the actual mission applicat ion, the motors could be readily reoriented at a  90° angle or even doubled back upon the assembly to reduce length.   Though commercial components were used, the design has a direct path to flight with vacuum and  temperature compatible materials and lubricant. The current prototype is capable of environmental testing in a laboratory environment.  Early component and subassembly testing certainly reduced risk. Individual testing of the core handling mechanisms allowed definition of the design parameters needed to complete the integrated corer design while giving confidence that the integr ated corer would function successfully.   Additional telemetry and improved data are requi red for fully understanding the rotary-percussive  problem. As mentioned earlier, the analysis done while designing the hammer cam profile on the integrated corer yielded insight to the critical timing  nature of the rotary-percussive mechanism. A rotarypercussive mechanism can only operate within a na rrow speed range and still be effective. Excessive  hammer energy losses can occur if  the mechanism rotates too slowly, and rotating too fast can prevent  the hammer from contacting the bit. The rotary-percu ssive events occur over a period of milliseconds.  Having hammer position and/or impact feedback, for ex ample, would enable better assessment of what is  really happening in the mechanism and prevent erroneous conclusions.  

Acknowledgements 

The authors would like to thank Paul Backes of JPL and Adam Armstrong, Jason Bardis, Jason Bean,  Amanda Bright, Dan DiBiase, Rene Espinosa, Richard Fleischner, Jay Harland, Brett Lindenfeld, Richard  McKenzie, Roy Nakagawa, Bill Reed, Stephanie Smith, and Chris Thayer of the Space Division of MDA Information Systems, Inc. for their work and support on this project. 

References 

1. Ng, T.C. & Yung, K.L. “Mars Rock Corer and Planetary Micro Sampling Tools.” Proceedings of the  33 rd Lunar and Planetary Science Conference , (2002).  2. Fleischner, R. ”Concurrent Actuator Developm ent for the Mars Exploration Rover Instrument  Deployment Device.” Proceedings of 10th European Space Mechanisms and Tribology Symposium ,  (2003).  3. Maurer, William C. Novel Drilling Techniques.  New York: Pergamon Press, ©1979  NASA/CP-2010-216272