Date of Award

Spring 5-5-2023

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Advisor

Justin Lapp

Second Committee Member

Senthil Vel

Third Committee Member

Bashir Khoda

Abstract

Since the Apollo missions in the late 1960's, there has been a growing interest shared by many countries around the world to return to the Moon and establish a permanent Lunar settlement. The first phase of temporary Lunar bases will be established over the next several years. For a permanent human presence on the Moon, it will be necessary to use locally available resources for the construction of Lunar habitats and other infrastructure. Sintering Lunar regolith has been shown to be a promising method for producing structural material with a variety of desirable properties from strength to radiation shielding. While many experiments have been done to develop new methods of sintering, little progress has been made on producing usable construction material. Furthermore, a wide variety of sintering methods have been proposed which represent a range of strengths and weaknesses. This research aims to fill a gap in the existing literature with regard to evaluating the characteristics of usable sintered regolith and the performance of associated sintering methods in the context of selecting a suitable method for early Lunar development. A literature review was conducted to investigate existing sintering methods and to define the most important parameters relating to usability. This information was used to compile the Usability Criteria, a novel evaluation tool for comparing sintering methods and their products across seven fundamental categories. For sintered bricks or structural material; strength, hardness, and uniformity are considered. Sintering methods and equipment are assessed based on energy efficiency, versatility, labor requirement, and a combination of production rate and mass efficiency. Four grade levels were designated within each criterion as well as an overall importance factor ranging from 1-5. Two promising sintering methods, selected for their unique processes and resulting products, were then reproduced at laboratory scale to make bricks from Lunar regolith simulant. The first method made use of a high-temperature furnace and custom molds to make bricks using radiant heating. The second method involved forming bricks by applying consecutive thin layers of regolith on top of one another in between periods of concentrated solar radiation exposure. Data was collected from the sintered bricks as both a contribution to the existing body of sintered regolith research and for evaluation under the Usability Criteria. Considering that the Usability Criteria are intended for full-scale sintering system evaluation, the numerical scores applied to the laboratory-scale systems are only valid for comparison purposes. The furnace-sintered samples performed better in energy efficiency and had a significantly higher average compressive strength. The solar-additive-manufacturing samples outperformed the furnace samples in most system-based categories, particularly in production rate and mass efficiency. While some criteria will likely be adjusted, and others may be added or removed, the proposed evaluation tool may be beneficial in guiding future research and eventually the selection process for Lunar sintering and construction equipment.

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