Tech Briefs

NASA’s plans for a lunar outpost require extensive excavation. The Lunar Surface Systems Project Office projects that thousands of tons of lunar soil will need to be moved. Conventional excavators dig through soil by brute force, and depend upon their substantial weight to react to the forces generated. This approach will not be feasible on the Moon for two reasons: (1) gravity is 1/6th that on Earth, which means that a kg on the Moon will supply 1/6 the down force that it does on Earth, and (2) transportation costs (at the time of this reporting) of $50K to$100K per kg make massive excavators economically unattractive.

A percussive excavation system was developed for use in vacuum or near-vacuum environments. It reduces the down force needed for excavation by an order of magnitude by using percussion to assist in soil penetration and digging. The novelty of this excavator is that it incorporates a percussive mechanism suited to sustained operation in a vacuum environment.

A percussive digger breadboard was designed, built, and successfully tested under both ambient and vacuum conditions. The breadboard was run in vacuum to more than 2 times the lifetime of the Apollo Lunar Surface Drill, throughout which the mechanism performed and held up well. The percussive digger was demonstrated to reduce the force necessary for digging in lunar soil simulant by an order of magnitude, providing reductions as high as 45:1.

This is an enabling technology for lunar site preparation and ISRU (In Situ Resource Utilization) mining activities. At transportation costs of $50K to$100K per kg, reducing digging forces by an order of magnitude translates into billions of dollars saved by not launching heavier systems to accomplish excavation tasks necessary to the establishment of a lunar outpost. Applications on the lunar surface include excavation for habitats, construction of roads, landing pads, berms, foundations, habitat shielding, and ISRU.

This work was done by Jack Wilson, Philip Chu, Jack Craft, Kris Zacny, and Chris Santoro of Honeybee Robotics Ltd. for Kennedy Space Center. KSC-13398

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