The Regolith Advanced Surface Systems Operations Robot (RASSOR) excavator robot is a teleoperated mobility platform with a space regolith excavation capability. This more compact, lightweight design (<50 kg) has counter- rotating bucket drums, which results in a net-zero reaction horizontal force due to the self-cancelation of the symmetrical, equal but opposing, digging forces.

This robot can operate in extremely low-gravity conditions, such as on the Moon, Mars, an asteroid, or a comet. In addition, the RASSOR system is designed to be easily transported to a space destination on a robotic precursor landing mission. The robot is capable of traversing over steep slopes and difficult regolith terrain, such as an impact crater on the Moon, and has a reversible operation mode so that it can tolerate an over-turning incident with a graceful recovery, allowing regolith excavation operations to continue.

The RASSOR excavator consists of a mobility platform with tread belts on the port and starboard sides that are each driven by electrical motors, but it could also operate with a wheel system to further reduce mass. Two batteries are mounted in a “saddlebag” configuration on either side. Two counter-rotating bucket drum digging implements are held by a rotating cantilever mechanism at the fore and aft ends of the mobility platform. The cantilever arms are raised and lowered to engage the bucket drum into the soil or regolith. A variable cutting depth is possible by controlling the angles of the cantilever arms.

The unit has three modes of operation: load, haul, and dump. During loading, the bucket drums will excavate soil/regolith by using a rotational motion whereby scoops mounted on the drum’s exteriors sequentially take multiple cuts of soil/regolith while rotating at approximately 20 revolutions per minute. During hauling, the bucket drums are raised by rotating the arms to provide a clearance with the surface being excavated. The mobility platform can then proceed to move while the soil/regolith remains in the raised bucket drums. Finally, when the excavator reaches the end-user or dump location, the bucket drums are commanded to reverse their direction of rotation to the opposite spin from digging, causing the gathered materials to be expelled out of each successive scoop. It can also stand up in a vertical mode to deliver regolith over the edge of a hopper container.

The RASSOR can operate with either side up in a reversible mode and it can flip itself over. This means the unit can drive directly off of the deck of a lander to deploy in low gravity, eliminating a deployment mechanism, which saves mass and increases reliability due to decreased complexity. The RASSOR system is scaleable and may be mounted on mobility platforms of various sizes, and has control equipment — wireless signal router, computer, joystick, E-stop, and associated software.

This work was done by Robert P. Mueller, Jonathan D. Smith, Tom Ebert, Rachel Cox, Laila Rahmatian, and James Wood of Kennedy Space Center; Jason Schuler of EASI; and Andrew Nick of Sierra Lobo. For more information, contact the Kennedy Space Center Innovative Partnerships Office at 321- 867-5033. KSC-13664

NASA Tech Briefs Magazine

This article first appeared in the January, 2013 issue of NASA Tech Briefs Magazine.

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