Carnegie Mellon | 13 December Testing and Characterization December 2007 Carnegie Mellon

Scarab Testing & Characterization Carnegie Mellon December 2007 Scott Moreland

Carnegie Mellon | 13 December Characterization Mobility –CG xyz, Static tip-over angles –Drawbar Pull –Side slope  lean (level) vs. baseline –Straight incline ascent, lowering CG –Obstacles: trenching, boulders, etc.. Drilling –Gravity off-load  Can enough thrust be produced? Resist torques? –Drill thrust/torque extremes simulation –Slopes

Carnegie Mellon | 13 December Vehicle Center of Gravity X-Y CG Total Weight: 280 kg Drill system mass/CG stand-in ASRG used to center vehicle CG Z CG Pose Dependent *nominal *low *high

Carnegie Mellon | 13 December Static Tip-Over Angles *low *nominal *high (values from tilt-table testing)

Carnegie Mellon | 13 December Side Slope Side Slopes –Significant increase in traction while body leveling on side slopes –25° cross slope results 52% decrease in downhill slip Important sources of beneficial effects (side hill lean) –Edging of wheels –Equalize wheel pressure distribution Actively centering CG over track-base center Traction and control

Carnegie Mellon | 13 December Side Slope Side Slopes –Significant increase in traction while body leveling on side slopes –25° cross slope results 52% decrease in downhill slip Important sources of beneficial effects (side hill lean) –Edging of wheels –Equalize wheel pressure distribution Actively centering CG over track-base center Traction and control

Carnegie Mellon | 13 December Straight Hill Ascent Straight Ascent (pose vs. angle of refusal) –25° incline tests: refuse at high pose, ascends at nominal/low pose –Lowering CG through pose change promotes equal normal force distribution in wheels  increases angle of refusal

Carnegie Mellon | 13 December Drawbar Pull Tested at full vehicle weight, 280 kg XY-CG centered Rubber skid loader tires 60 cm diameter 17 cm tread width Coarse Sand: 160 kg pull 0.57 vehicle weight High Traction Cement 240 kg pull 0.85 vehicle weight

Carnegie Mellon | 13 December Trenching –50 cm Trench capability –Wheel Diameter, 60 cm Boulders Periodic obstacles Obstacles

Carnegie Mellon | 13 December Drilling Nominal Drilling Test –Support 1 m drilling into OB-1 lunar regolith simulant with NORCAT system Gravity Off-loading –Drill reaction forces simulated while under lunar g Drill reaction forces –350 N max. thrust –30 Nm torque 250 kg Earth  42 kg Lunar (gravity off-loaded) 42 kg weight – 350 N thrust  6.0 kg Mass Reserve –Capabilities Expanded wheel base resists high drill torques –Failures Combined loading: Lunar gravity while drilling on slopes > 15°, leads to downhill slippage Down hill force rapidly increasing with slope angle

Carnegie Mellon | 13 December Specifications Drill tower (upright): 2.2 m high stance, 1.6 m low stance Mass: 280 kg Weight:460 N  2750 N  Nominal power: 200 W (driving), 380 W (pose change)  Idle power: 78 W Locomotion speed: 5.0 – 6.0 cm/s Track width:1.4 m Wheelbase: m Aspect ratio (track/wheelbase):1:1 low stance, 1:2 nominal, 1:7 high CG height: 0.64m nominal stance, 0.60m low, 0.72m high Static pitchover: 42° nominal stance, 29° high, 45° low Static rollover: 53° nominal stance, 48° high, 55° low Maximum / minimum straddle:57 cm, Belly contact Approach / departure angle:105° nominal stance Wheel diameter:60 cm Rim pull (single wheel): 2500 N Drawbar pull:1560 N (medium-coarse grain sand) } with full drill system payload