18 Corer Tool Background 

The Low-force Sample Acquisition System (LSAS)   Previous design efforts were leveraged during the dev elopment of the rotary-percussive coring tool. In  2006, the Space Division of MDA Information Systems, Inc. (formerly Alliance Spacesystems) produced a  rotary percussive drill designed for space use under a NASA-funded Mars Instrument Development  Program (MIDP) project – the Low-force Sample Acquisition System (LSAS) in Figure 1. The flight-like  drill prototype that was the end result  of the project successfully drill ed and acquired 1-cm³ sample fines  from a variety of rocks and soils, including the hardest anticipated Martian rock (basalt) and frozen soil. This ability was demonstrated in ambient conditions and in a thermal/vacuum ch amber replicating Mars  pressure and extreme temperatures. The rotary perc ussive approach was demonstrated to be simple,  robust, and highly efficient in power and mass. 

Figure 1. Original Low-Force Sample Acquisition System (LSAS) 

The successful performance of the LSAS drilling sy stem, along with the difficulties encountered by  existing coring devices, led MDA Information Systems to consider applyi ng LSAS and its rotary  percussive action to the coring problem. The LSAS prototype was simply adapted to accommodate a  commercial coring bit (see Figure 2), and no attempt was made to optimize the drill for the new coring operating conditions. The results were surprisingly  positive. When drilling in limestone, 1-cm-diameter  cores were readily produced up to 1 cm long in as little as 20 minutes while mounted on a rover-mounted robotic arm. The drill readily began coring without a p ilot hole, probably because of the low applied force  and compliance of the robotic arm/rover platform.  SBIR 2006 Phase 1

Following the encouraging results with the modifi ed LSAS drill, a Phase 1 SBIR effort commenced in  2006 that took this heritage device and expanded its potential to include coring against a variety of rock materials anticipated to be encountered on Mars. An industry and literature search was conducted to identify best practices in rotary percussive coring, and commercial off-the-shelf (COTS) bits were located for test. An extensive test program was performed to  evaluate these bits with accompanying performance  parameters such as rotational speed, WOB, hammer frequency, and hammer force. Through the use of a  breadboard fixture (see Figure 3), coring bit designs  and coring parameters were evaluated to identify  optimum combinations. The breadboard fixture, with separate motors for driving rotary and hammering  action, allowed drilling parameters to be independently varied during testing.   Brushless Motor (22mm dia.)Planetary Gearbox Drilling Force/Vibration Isolation Spring Hammer Force Spring Sample Bin Volume=1.3cm3Hammer/Cam profile Max Depth SensorCam FollowerDrill Preload Limit Sensor Angular Contact Bearing PairSquare Spline Drive Shaft Bushing/Dust SealSample Bin Seal Brushless Motor (22mm dia.)Planetary Gearbox Drilling Force/Vibration Isolation Spring Hammer Force Spring Sample Bin Volume=1.3cm3Hammer/Cam profile Max Depth SensorCam FollowerDrill Preload Limit Sensor Angular Contact Bearing PairSquare Spline Drive Shaft Bushing/Dust SealSample Bin Seal NASA/CP-2010-216272