Establishment of a base on the moon is an essential part of deep space missions. Any base on the moon should be self supporting, meaning the base should be able to mine, process, and store consumable resources on the moon to the extent possible. One of the most important aspects of establishing a base on the moon is the ability to excavate various formations for construction and mining purposes. Although the surface of the moon is covered by regolith and rock fragments, the layers below surface are more consolidated due to vibration caused by impacts or possibly freezing of condensed water vapors in the dark side and poles of the moon. The ice in the frozen soil, is possibly the most valuable resource on the moon and its excavation should be a part of advance planning of mining activities in space programs. This paper covers some of the background information on the properties of frozen regolith and discusses the extensive testing performed on lunar stimulant soils, including the compaction testing, measurement of compressive strength of frozen soil, indentation tests, and full scale cutting test of samples for development of a prototype lunar excavator.
Establishing self supporting base on the moon, which is a necessity for deep space missions, requires a constant supply of raw material that can preferably be mined on the moon surface. In addition, for construction of the base, certain excavation activities need to be performed in advance and they require machines that can cope with various types of material from soft surface regolith to consolidated soil, and possibly frozen soil. Excavation of such of distinctly variable material requires new and innovatively robust excavation system. The primary ore targeted at this time includes frozen regolith for extraction of moisture and water. Several concepts have been suggested for lunar excavation. This includes surface bucket excavator, shovels, surface miners, and roadmilling machines. Some of these machines are suitable for softer material or consolidated material when broken / fragmented, but not for rock or frozen soil. The rock like, harder formations do require an excavation system preferably with variable drum spacing to allow for excavation in various materials. To develop a viable cutting and excavation system, it is essential to develop an understanding of the characteristics of frozen regolith formations and its mechanical properties at surface and at depth. For this purpose, an extensive test plan was developed and executed within the past three years as a part of research study sponsored by NASA. This paper offers a review of the issues and general review of material properties for lunar regolith as well as the description and discussion of the testing plans and result of the studies on this subject, including the full scale cutting tests and design and testing of a prototype cutterhead for lunar excavation.
Several physical properties of dry lunar and Martian regolith have been directly measured or inferred from measurements.