Scarab Design Carnegie Mellon December 2007

CMU | 13 December Unique combination of drilling & driving on the moon Central issuesSolutions Drilling loads Weigh enough Mount drill on center Lower drill to ground Lunar terrain Agile suspension Adjustable suspension Low cg

CMU | 13 December Design approach Strong, slow & reliable Serial work machine Face disparate needs of drilling & driving Arrive at capabilities that complement each other

CMU | 13 December Weighing enough Robot weight on lunar surface must support drilling operation Up to 250 N downforce & 50 Nm torque required for drilling Reserve 150 N passing through wheels for stability, torque & margin against uplift and spin  Total weight on lunar surface > 400 N 400 N / m/s 2  250 kg vehicle mass

CMU | 13 December Mounting drill Fixed to chassis vs. articulated Strength & stiffness of load path through chassis & suspension back to the ground Dual as instrument mast

CMU | 13 December Mobility design 4 wheels, directly driven Skid steered –Simplicity & Lunokhod precedence Passive kinematic suspension 1 mechanical release Differential –Maintain rectangular stability pyramid base Linkage differential –Suspension provided attach points –Frees drill workspace –Stiffness Pose adjustment –Actuate height of each side –Outboard of differencing effect

CMU | 13 December Suspension 1.3 m 1.4 m CG h = 0.6 m Stability pyramid

CMU | 13 December Wheel actuation Local amplifier Brushless motor 5:1 planetary 80:1 harmonic drive 400:1 total reduction Rim pull ~ vehicle weight

CMU | 13 December Agile suspension Passive matching of terrain Large stroke for terrain approaching wheel diameter in size Steady platform for sensing

CMU | 13 December Agile suspension Twist course video

CMU | 13 December Underbody shape Maintains 30 cm belly clearance with a wheel on 30 cm positive obstacles Keeps drill tip closest to ground when kneeling 30 cm

CMU | 13 December Lowering drill Major benefit for drill system Sensors inspect site prior to kneeling Scarab poses with belly just above ground

CMU | 13 December Pose adjustment mechanism Raises & lowers by actuating wing angle (independent L & R) Center link bisects wing angle: enables lift-and-level body averaging Retains advantages of passive rocker bogie Many ways to implement

CMU | 13 December Mobility benefits Climbing slopes otherwise unable to Leaning into cross-slopes for stability Autonomous body roll leveling Raising to avoid or recover from high centering Changing wheelbase in reaction to periodic terrain Inch-worming out of dug- in condition

CMU | 13 December Scalability Body is readily modifiable to suit payloads Configuration is scalable in both directions

CMU | 13 December Specifications Mass: 280 kg Weight:460 N  2750 N  Power (driving): 200 W (peak)  Power (posing):380 W (peak)  Power (idle): 78 W Speed: 5.0 cm/s (6.0 cm/s max) Height (with drill tower): 2.2 m high stance, 1.6 m low stance Width (wheelbase):1.4 m Length (wheelbase): m Aspect (track/wheelbase):1:1 low stance, 1:2 nominal, 1:7 high Wheel diameter:60 cm

Additional Material

CMU | 13 December Specifications CG height: 0.64m nominal, 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 Breakover angle:115° nominal stance Rim pull (single wheel): 2500 N Drawbar pull:1560 N (medium-coarse grain sand)

CMU | 13 December Design solution Drill implementation –Central location on vehicle to maximize weight for downforce –Direct mounting to chassis –Fixed drill structure Reduced actuation Functions as navigation mast Simplifies kinematics & mass properties Adjustable kinematic suspension –Body roll averaging over terrain –Bring drill to surface to operate –High stiffness platform to react drilling forces Skid steering –Reduced actuation –Increased stiffness Thermal approach –Utilize heat from radioisotope power supply –Shunt excess heat to radiator surface

CMU | 13 December Vehicle requirements Drill dominated design –Bring drill to surface to operate –High stiffness platform to react forces Mobility over rough terrain –30 cm obstacles –Steep soil slopes Environments –Fine, abrasive dust –Vacuum, 40 K ground, 3 K sky Power –Radioisotopic power supply

CMU | 13 December NORCAT coring system 1 meter drilling, sampling & processing system –Lab R&D maturity Specs –ø30 cm borehole –ø1.5 cm continuous core –~50 kg –0.5 m x 0.5 m x 1.5 m volume Operations: –Drill to depth –Capture core, transfer –Meter core into pieces –Crush into fines –Transfer to oven Issues: –Loads, torques, vibrations –1500 – 3000 cc cuttings pile

CMU | 13 December Drill cuttings

CMU | 13 December Potential attributes Internal actuation: shafts through shoulder & shaft-drive to hubs Actuated suspension to surmount extreme obstacle or extricate from twist Space-relevant wheels & tread: design, fab, mount Hosting more of RESOLVE subsystems Upscale chassis and body-averaging beam Thermal isolation of cold drill and warm body

CMU | 13 December Nominal ride height

CMU | 13 December Nominal ride height

CMU | 13 December Nominal ride height

CMU | 13 December JPL Sample-Return Rover SRR1 –4-wheel skid, rotary actuated shoulder, differential body pose SRR2K –4-wheel steering added