19   Figure 2. Modified LSAS in Test Fixture with Commercial Coring Bit 

Phase 1 results indicated that the primary goal of producing a 1-cm-diameter, 10-cm-long core１ from a  variety of rocks, including hard basalt was achiev able, though not without complications. The commercial  coring bits exhibited rapid dulling, particularly with basalt and sand stone. This suggested the importance  of a bit change-out mechanism and/or the need for further bit refinement. Also, the bit and associated  performance parameters required to core basalt are evidently too aggressive for softer materials, particularly layered rock structures, resulting in brok en or even pulverized cores. As a result, a conceptual  corer was designed that included a bit change mechanism concept and a means of modifying the percussive force. Finally, it was found that relative ly large amounts of power, approximately 90 watts,  were needed to generate the cores. Although a specific  power target was not established at the time of  Phase 1 testing, it was clear this was in excess of current rover capacity. Mission requirements were to  later baseline 65 watts as the targeted value, an intimidating goal in view of the Phase 1 data.  SBIR 2006 Phase 2

The Phase 2 effort evolved the conceptual design developed in Phase 1 by evaluating each function (coring, break-off, retention, and tr ansfer), building prototypes, and ultimately generating an integrated  prototype coring mechanism incorporating each deta il function. In addition  to the 65-watt power  consumption target, mission requirements later defined in the project included a 5-kg mass budget for the integrated corer, coring performance yielding 5-6 cm  long corer samples within a Martian day, and a corer  WOB no greater than 50 N. This paper focuses on the Phase 2 design efforts to achieve such a corer.   Development of the Corer   The Phase 2 work plan was divided into four primary sections: (1) development of a custom coring bit, (2)  core handling mechanisms development, (3) protot ype corer development, and (4) corer testing. 

(1) Custom Coring Bit Development

The majority of the coring bit data from Phase 1 were produced from tests with the COTS coring bit that  showed the most promise for core generation, a 1-in ch (25-mm) diameter coring bit from Milwaukee,   P/N 48-20-5005. These co ring bits are designed for the drilling of holes, not for the ge neration of intact  rock cores. Nonetheless, the Milwaukee bits successfu lly yielded cores in testing, though the cores were  occasionally fractured. Also, the generated cores were 1.5 cm in diameter, subs tantially larger than the  targeted 1 cm.  The objective of the coring bit development was to  thus produce a custom coring bit capable of  consistently generating intact 1 cm diameter cores. A targeted core length was defined at 6 cm based on  the latest mission requirements from the science community. The coring bit development was performed in parallel with the core handling mechanisms developm ent so that the coring bit could be designed to                                                    １ Original mission requirements dictated a 1 cm x 10 cm long core, and later eased to 5-6 cm long.   NASA/CP-2010-216272