April means gardening season is here again, but how about digging through some red dirt about 40 million miles away? For engineers at Honeybee Robotics Spacecraft and Mechanisms Design Company, based in New York, they've been doing just that for years. A Rock Abrasion Tool (RAT) they designed for the 2003 Mars Exploration Rover Mission is still in operation today on the red planet, responding to remote control from an office in The Big Apple. The RAT uncovers layers of soil to reveal near-surface stratigraphy by grinding the rock surface 5-mm deep.
The next mission — 2009 Mars Science Laboratory — not only calls for a RAT, but also a separate rock-coring tool called the Mini-Corer, which comes in a shoebox-sized enclosure. This outer box seals the interior from dust and acts as a rigid structural housing. Inside is a smaller box, about the size of a human fist. The nested enclosures double seal the Mini-Corer to prevent dust from entering its gears and bearings.
The smaller box, which houses the drive components that rotate the coring tool, slides on two double-wide linear bearings from NB Corp., Wood Dale, Ill., fixed within the larger box. A drive mechanism within the outer box pushes the inner box back-and-forth along the bearing track, plunging or retracting the drill as commanded. Honeybee chose the double-wide bearing because it provides more stiffness and rigidity than they could get from two standard bushings.