A report proposes brush-wheel mechanisms for acquiring samples of soils from remote planets. In simplest terms, such a mechanism would contain brush wheels that would be counter-rotated at relatively high speed. The mechanism would be lowered to the ground from a spacecraft or other exploratory vehicle. Upon contact with the ground, the counterrotating brush wheels would kick soil up into a collection chamber. Thus, in form and function, the mechanism would partly resemble traditional street and carpet sweepers. The main advantage of using of brush wheels (in contradistinction to cutting wheels or other, more complex mechanisms) is that upon encountering soil harder than expected, the brushes could simply deflect and the motor(s) could continue to turn. That is, sufficiently flexible brushes would afford resistance to jamming and to overloading of the motors used to rotate the brushes, and so the motors could be made correspondingly lighter and less power hungry. Of course, one could select the brush stiffnesses and motor torques and speeds for greatest effectiveness in sampling soil of a specific anticipated degree of hardness.
This work was done by Tommaso Rivellini of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Mechanics category. NPO-30665.
This Brief includes a Technical Support Package (TSP).
Brush-Wheel Samplers for Planetary Exploration
(reference NPO-30665) is currently available for download from the TSP library.
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Overview
The document is a technical support package prepared by Tom Rivellini and Fabian Nicais for NASA's Jet Propulsion Laboratory (JPL), detailing a concept for a brush-wheel sampler designed for the Gulliver Deimos Sample Return Mars Scout Proposal. The primary focus of the document is on the innovative design and functionality of the brush-wheel sampler, which aims to efficiently collect soil samples from planetary bodies, particularly Mars.
The brush-wheel sampler introduces compliant contact elements, specifically brush bristles, which allow for adaptability in performance based on soil properties. This design addresses two main challenges: the need for a short sampling time and tolerance to jamming. Traditional sampling methods often face issues with jamming when encountering harder materials, but the compliant elements in this design can deflect rather than jam, ensuring continuous operation.
Key design drivers for the sampler include the ability to handle loose, unconsolidated regolith with a density of 1.5 g/cc, the implementation of stand-off sampling to protect the spacecraft, and minimizing the required depth of surface material needed for sample collection. The sampler is designed for open-loop operation, requiring only momentary contact with the surface, and operates at low contact forces to collect samples effectively.
The document emphasizes the importance of a simple and robust handoff mechanism to the Entry Vehicle, ensuring that the collected samples are balanced regardless of the final sample mass. The operational parameters include touch-and-go velocity assumptions, with vertical and horizontal velocities specified to ensure effective sampling.
Additionally, the document includes disclaimers regarding the nature of the review, clarifying that it is not a design review but rather a concept review of a point design. It also notes that references to specific commercial products do not imply endorsement by the U.S. Government or JPL.
Overall, this technical support package outlines a novel approach to planetary sampling that leverages compliant technology to enhance efficiency and reliability, contributing to the broader goals of planetary exploration and sample return missions. The brush-wheel sampler represents a significant advancement in the field of extraterrestrial soil collection, with potential applications in future Mars missions and beyond.
