1. Scarab Design Carnegie Mellon 13-14 December 2007

2. CMU | 13 December 20072 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

3. CMU | 13 December 20073 Design approach Strong, slow & reliable Serial work machine Face disparate needs of drilling & driving Arrive at capabilities that complement each other

4. CMU | 13 December 20074 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 / 1.622 m/s 2  250 kg vehicle mass

5. CMU | 13 December 20075 Mounting drill Fixed to chassis vs. articulated Strength & stiffness of load path through chassis & suspension back to the ground Dual as instrument mast

6. CMU | 13 December 20076 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

7. CMU | 13 December 20077 Suspension 1.3 m 1.4 m CG h = 0.6 m Stability pyramid

8. CMU | 13 December 20078 Wheel actuation Local amplifier Brushless motor 5:1 planetary 80:1 harmonic drive 400:1 total reduction Rim pull ~ vehicle weight

9. CMU | 13 December 20079 Agile suspension Passive matching of terrain Large stroke for terrain approaching wheel diameter in size Steady platform for sensing

10. CMU | 13 December 200710 Agile suspension Twist course video

11. CMU | 13 December 200711 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

12. CMU | 13 December 200712 Lowering drill Major benefit for drill system Sensors inspect site prior to kneeling Scarab poses with belly just above ground

13. CMU | 13 December 200713 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

14. CMU | 13 December 200714 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

15. CMU | 13 December 200715 Scalability Body is readily modifiable to suit payloads Configuration is scalable in both directions

16. CMU | 13 December 200716 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):0.8 - 1.3 m Aspect (track/wheelbase):1:1 low stance, 1:2 nominal, 1:7 high Wheel diameter:60 cm

17. Additional Material

18. CMU | 13 December 200718 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)

19. CMU | 13 December 200719 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

20. CMU | 13 December 200720 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

21. CMU | 13 December 200721 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

22. CMU | 13 December 200722 Drill cuttings

23. CMU | 13 December 200723 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

24. CMU | 13 December 200724 Nominal ride height

25. CMU | 13 December 200725 Nominal ride height

26. CMU | 13 December 200726 Nominal ride height

27. CMU | 13 December 200727 JPL Sample-Return Rover SRR1 –4-wheel skid, rotary actuated shoulder, differential body pose SRR2K –4-wheel steering added