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Shining light on optical mining: an experimental and modeling investigation for asteroid resource extraction
Broslav, Timofey V.
Broslav, Timofey V.
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2024
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Abstract
One of the main challenges faced in asteroid mining is being able to adequately, and efficiently, excavate material in an extremely low gravity environment. The reactive forces imposed by physical excavation methods can make it difficult to gather materials or keep the system anchored to the body. Additionally, tool wear and the need for extra spare parts increase mission costs and complexity. Heating asteroid bodies to temperatures required for water release from hydrated minerals can also prove time-consuming depending on the size of the body. To address these challenges, the Trans Astronautica Corporation (TransAstra) is developing Optical Mining, a contactless mining method designed to simultaneously excavate the surfaces of captured carbonaceous chondritic asteroids and extract water from hydrated minerals without relying on mechanical drills or bits. Asteroid fragments produced by an Optically induced thermal spalling process are concurrently heated to dehydroxylate the minerals and generate water which is trapped using trapping mechanisms aboard a spacecraft. This method hails to effectively harvest asteroid resources without running into issues of micro-gravity excavation using physical tools and significantly reduces the energy required compared to bulk heating of larger monolithic asteroid bodies.
This work explores the Optical Mining excavation process, a part of the overarching Optical Mining method, through both experimental and numerical investigations. Experimentally, the work examined how different irradiance distributions of the mining beam affect excavation and water production rates when applied to an asteroid simulant. Results have demonstrated that the Optical Mining excavation process can effectively excavate material and extract water from an asteroid simulant. Crucially, it was found that water production rates from hydrated minerals in the simulant are directly correlated with excavation rates. Using these experimental insights, a predictive Excavation model was developed. The Excavation model estimates excavation rates and the response behaviors of a body subjected to the Optical Mining excavation process, drawing on principles of thermal spalling and statistical failure theory. Moreover, the model incorporated a variety of stress-relief mechanisms to explain experimental observations of the spallation process on the tested simulant - including differences in excavation rates, and trends in the excavation rate as a function of beam irradiance. The combined experimental and modeling efforts addressed key questions about optimizing the Optical Mining method and mitigating adverse effects, such as preventing surface temperatures from exceeding the brittle-to-ductile transition zone and minimizing organic vapor deposition on optical surfaces.
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