A swivel-head drill bit has been invented for use in acquiring a sample of a possibly hard material at a predetermined depth. This mechanism is a simpler and thus potentially cheaper alternative to deep-coring and sampling mechanisms that contain secondary actuators to open doors and/or to drive internal sampling features. The only actuator needed to operate the swivel-head drill bit is the drill motor.
To be useful, a sampling mechanism must prevent mixing of sample material from the desired depth with material from other depths. Specifically, the present mechanism was developed subject to a requirement to limit mixing to a depth range of no more than 2 cm bracketing the desired depth. The challenge lay in satisfying this requirement without using secondary actuators.
The swivel-head drill bit includes (1) a body containing two identical sample chambers with openings at the front end capped by (2) the swivel head, which holds two cutters and can be rotated, relative to the body, to cover or uncover the openings. An integral shaft extends from behind the head through the body and is captured with a nut at the back end of the body. Small posts restrict the rotation of the head to a 90° range between the fully open and fully closed positions. The drill body and swivel head are made of MP35N alloy; the cutters are tungsten carbide inserts.
The head remains in the fully closed position as the drill bit is rotated clockwise during drilling. When the desired sampling depth has been reached, the bit is rotated counterclockwise, causing the head to swivel to the open position. The counterclockwise rotation is continued for a total of ten revolutions to move sample material into the sample chambers. Then the bit is rotated clockwise and pushed forward to swivel the head to the closed position. Finally, while rotating the bit clockwise slowly to keep the head in the closed position, the bit is withdrawn from the hole.
Swivel-head drill bits could be used to acquire subsurface samples from such diverse sources as geological sites, hazardous-waste dumps, structures, remote planets, comets, and asteroids. For example, they could be used to sample the walls and interiors of the Chernobyl nuclear reactors. In tests, the prototype swivel-head drill bit performed successfully in the acquisition of samples from the bottoms of holes in rock, plaster, and loose olivine sand.
This work was done by Greg R. Gillis-Smith of Caltech for NASA's Jet Propulsion Laboratory. NPO-20390
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Swivel-head sampling drill bit
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Overview
The document discusses the Swivel-Head Sampling Drill Bit, an innovative tool developed by Greg R. Gillis-Smith at NASA's Jet Propulsion Laboratory. This drill bit is designed for acquiring subsurface samples from hard materials at predetermined depths, addressing the need for efficient and accurate sampling in various environments, including geological sites, hazardous waste dumps, and extraterrestrial bodies like comets and asteroids.
The primary challenge in subsurface sampling is to avoid vertical mixing of materials from different depths. Traditional deep-coring methods often rely on complex mechanisms with secondary actuators to manage sample collection, which can increase costs and complexity. The swivel-head drill bit offers a simpler solution by utilizing a single actuator—the drill motor—while effectively preventing mixing within a 2 cm range around the desired sampling depth.
The drill bit features a body with two identical sample chambers, each capped by a swivel head that can rotate to cover or uncover the chamber openings. The head remains closed while drilling to the desired depth. Once the target depth is reached, the bit is rotated counterclockwise (CCW) for ten revolutions, allowing fresh sample material to enter the chambers. Afterward, the bit is rotated clockwise (CW) while applying downward pressure to close the head, and it is then slowly withdrawn from the hole.
Constructed from MP35N alloy for the body and swivel head, and featuring tungsten carbide inserts for the cutters, the drill bit is designed for durability and effectiveness. The mechanism allows for low-power, low-mass drilling, making it suitable for small hole applications. Tests have demonstrated its successful performance in various materials, including rock, plaster, and loose olivine sand.
The document highlights the potential applications of the swivel-head drill bit in sampling environments that require precision and minimal contamination. Its design represents a significant advancement in drilling technology, particularly for planetary and cometary sample return missions, where traditional methods may be impractical. Overall, the swivel-head drill bit exemplifies innovation in aerospace engineering, providing a reliable tool for future exploration and research.
