A sampling device and a deployment method were developed that allow collection of a predefined sample volume from up to a predefined depth, precise sampling site selection, and low impact on the deploying spacecraft. This device is accelerated toward the sampled body, penetrates the surface, closes a door mechanism to retain the sample, and ejects a sampling tube with the sample inside. At the same time the drive tube is accelerated, a sacrificial reaction mass can be accelerated in the opposite direction and released in space to minimize the momentum impact on the spacecraft. The energy required to accelerate both objects is sourced locally, and can be a spring, cold gas, electric, or pyrotechnic. After the sample tube is ejected or extracted from the drive tube, it can be presented for analysis or placed in a sample return capsule.

The drive tube assembly design (top), and prototype with the sample canister partially ejected (bottom).
The external structure houses the sample canister and will be the main body in contact with the sampled media during the penetration. Its front edges are chamfered at an angle of 30 to 40° with the longitudinal axis. The back end is attached to the decelerator and the retention and ejection mechanisms. The decelerator’s main function is to prevent the drive tube from penetrating too deep into the sampled media if the drive tube’s kinetic energy is larger than the penetration energy for the external structure. The sample canister will enclose the sample during the penetration, and houses the sample retention mechanism.

There was developed a series of sample retention mechanisms. A bistable blade sample retention mechanism is more suitable to a circular cross-section drive tube when hermetic sample canister closing is not required. It consists of a series of thin sheet blades, located in the wall of the sample canister, which bends along the long axis and provides higher buckling and bending stiffness. A pull or push guillotine blade is more suitable for a rectangular cross-section drive tube, and provides a more definite sample canister closure and sample retention. The pull guillotine blade is stowed on the sample canister wall and has the edges guided in slots in the adjacent walls. After the full penetration depth is reached, the blade is pushed and closes the bottom of the sample canister. The pull guillotine blade includes an additional cutout section to allow the sample to enter the sample canister during the penetration. The blade strips that are left from the blade on the side of the cutout section can roll on wheels to reduce blade necessary pull force during the engagement. Electromechanical actuators, constant force springs, and torsion springs can be used for actuating the blades during engagement and sample retention.

The canister ejection mechanisms eject the sample canister with the enclosed sample at the end of the sample retention mechanism engagement or when it is independently triggered. It consists of a trigger mechanism, a series of pull pins, a series of springs, and a push plate. The compressed springs push the plate against a shoulder in the sample canister and accelerate it out of the outer structure. Once the push plate has reached a desired travel, it is retained along with the springs on the decelerator and outer structure on the comet. Only the ejected sample canister is then returned to the spacecraft for further processing.

The reactionless drive tube allows for sample collection with a large strength range from the proximity of a low-gravity body with minimum disturbance to the deploying spacecraft. It includes a separate sample canister to allow for a known geometry object handling with a clean surface, a sample retention mechanism that allows stowing in a thin wall tube, and mechanisms for sample retention mechanisms actuation and sample canister ejection.

This work was done by Mircea Badescu, Nicholas Wiltsie, Robert G. Bonitz, Paul G. Backes, Anthony J. Ganino, and Nicolas E. Haddad of Caltech for NASA’s Jet Propulsion Laboratory. NPO-49371

This Brief includes a Technical Support Package (TSP).
Reactionless Drive Tube Sampling Device and Deployment Method

(reference NPO49371) is currently available for download from the TSP library.

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This article first appeared in the March, 2015 issue of NASA Tech Briefs Magazine.

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