NEEP533 Course Notes (Spring 1999)
Resources from Space

Lecture #27: There's Helium in Them Thar Craters!


Title: Lunar Mine Planning

The Regolith as a Mining Environment

(Please refer to Lecture 12, Stage 7: Mature Crust for other details and photographs)

Understanding the lunar regolith and obtaining quantitative data on its "geotechnical" variables will be crucial to the planning of mining operations within it and the design of hardware and software of mining and processing equipment.

Regolith: Regolith constitutes the most important material with respect to resources on the Moon. It covers most of the surfaces of the Moon and is the most logical material to process for volatiles, metals, non-metals, and aggregate. Regolith "...is a terrestrial term, also used for the Moon. It has been defined as 'a general term for the layer or mantle of fragmental and unconsolidated rock material, whether residual or transported and of highly varied character, that nearly everywhere forms the surface of the land and overlies or covers bedrock. It includes rock debris of all kinds, including volcanic ash .. '... lunar regolith consists of particles <1 cm in size although larger cobbles and boulders, some as much as several meters across, are commonly found at the surface....much of the pulverized material is melted and welded together to produce breccias (fragmental rocks) and impact melt rocks, which make up a significant portion of the regolith ..." (Heiken, et al, 1991)

Shoemaker, et al., 1968, is a particularly important reference in regard to characterization of the lunar regolith. A particularly important part of the lunar regolith consists of aggregates of rock, mineral, and glass fragments, held together by impact melt glass, called agglutinates. Further, the lunar regolith contains adsorbed solar wind gases, meteoritic material, and the products of solar and cosmic radiation. Lateral mixing of the regolith derived from various bedrock materials is a function of the age of the separating contact.

A conceptional illustration of the initial stages of regolith development is given below in cross-section. It is important to imagine the result of continuing this cratering and mixing process for nearly 4 billion years until the surface has become saturated with craters 30-50 meters in diameter. During this time, impacts of craters smaller and far more numerous than this size continually wear down excavated boulders of bedrock, impact generated regolith breccia, and the larger craters themselves. The net result is a material that is heterogeneous and incompletely mixed in detail but homogeneous over large areas and to several meters depth with respect to processing for its resources.

Conceptual Development of Lunar Regolith in Mare Basins

This table summarizes geotechnical data necessary to plan for regolith mining operations at an optimum site on the Moon, and the source and level of our current understanding of these parameters..

This table summarizes geotechnical data necessary to design mining and processing equipment related to resources in the lunar regolith, and the source and level of our current understanding of these parameters.


Example of Mining Equipment Designed to Extract Lunar Volatiles-Example He-3

From lecture #19 it was shown that over 85% of the helium-3 could be removed from ilmenite by heating it to 700°C
The type of equipment that can accomplish the heating of large amounts of fine grain regolith is shown in the next picture. See Sviatoslavsky (1988) for more details.
In the process of extracting He-3, many other elements and compounds are produced.
The "coldness" of outer space can be used to separate the lunar volatiles.
The characteristics of the Mark-II miner are listed here.
There are at least 3 major applications for the volatile by-products from Lunar He-3 mining.

 

The Life support applications were discussed in lecture 19 and a future lecture on fusion propulsion will discuss their applications in transportation. Here, we will discuss only the possibility to use the by-products for making electricity from H2-O2 fuel cells.

The conditions for running the Mark-II lunar volatiles miner with a 200 kWe fuel cell are shown here.
In 5 earth days of operation (1/3 of a lunar day), the Mark-II miner would generate enough water which, when electrolized in a 250 kWe fixed solar array at the base camp, would provide enough H2 and O2 to keep the system running(during the lunar day) indefinetly. See Kulcinski et al., 1996.
After the first lunar day, the entire ouput of gases should be available for use on the Moon or for export to other space facilities.


MORE GENERAL MINING CONSTRAINTS


Principal Mining and Beneficiation Constraints


Principal Resource Refining Constraints

  • Initial mining requirements for one tonne 3He =
    • 22 km2 mined to a depth of 3m
    • recoverable grade in fines assumed: 45 ppb (assuming that initial mine site selection has maximized recoverable grade relative to age and ilmenite abundance)
    • regolith density assumed: 1.5 g/cm3
    • usable regolith assumed: 50%

    Regolith and Pyroclastic Volatiles Mining Approach

    • Surface Bulk Tonnage Continuous Mining (similar to terrestrial bucket wheels, dredges, and draglines)
    • Robotic with human intervention and maintenance
    • In situ beneficiation and thermal extraction of volatiles
    • Waste heat recovery
    • Regolith waste disposal in mined track
    • Blocky rim craters avoided to average of one crater diameter
    • Craters less than 10 meters in diameter destroyed
    • No major change in surface albedo expected
  • Centralized volatiles refining choices


    • REGOLITH MINERALS (extraction of metals, oxygen, aggregate, and sintering material might be combined with regolith volatiles mining)


    PRIMARY MINERALS (as layers in basalt cooling units)

    Lava tube (NASA art S88-33546)

    Mining and Sealing Concept (after Chamberlain, et al., 1993)


    POSSIBLE NEW INFORMATION REQUIREMENTS FOR OPTIMUM PLANNING AND TO MEET INVESTOR REQUIREMENTS
     
    Requirements for planning initial mining operations
     Requirements for selecting initial support base site


    Questions:


    1. Outline the types of geotechnical (geological engineering) data that would be required to design a Mark II-type miner.


    2. Define the basic characteristics required by a cryogenic storage system placed within the lunar regolith and how could an impact crater be adapted to contain such a system.


    3. Outline the trade-off considerations necessary to be able to choose between rectilinear and spiral mining concepts for mining 3He from the lunar regolith.




    Text:

    Cameron, 1993, pages 3 (Objectives of an Exploration Program) through end

    Schmitt, et al., 1992, pages 1163-1170

    Neal, et al., 1988, pages 16-18, Table 2-3




    References:

    Agosto, W.N., 1985, Electrostatic concentration of lunar soil minerals,in W.W. Mendel, editor, Lunar Bases and Space Activities of the 21st Century, 453-464.


    Cameron, E.N., 1993, Evaluation of the Regolith of Mare Tranquillitatis as a Source of Volatile Elements, WCSAR-TR-AR3-9301-1, 15p.


    Cameron, E.N., 1992, Helium Resources of Mare Tranquillitatis, Technical Report, WCSAR-TR-AR3-9207-1, 67p.


    Chamberlain, P.G., et al., 1993, A review of possible mining applications in space, in Resources of Near-Earth Space, edited by J. Lewis, et al., University of Arizona Press, 51-68.


    Ehricke, K. A., 1985, Lunar Industrialization and Settlement, in W.W. Mendel, editor, Lunar Bases and Space Activities of the 21st Century, p. 845, figure 3.

    Kulcinski, G. L., Mogahed, E. A., Santarius, J. F., Sviatoslavsky, I. N., and Wittenberg, L. J., 1996, Impact of Lunar Volatiles Produced During He-3 Mining Activities, Paper AIAA-96-0490 in 34th Aerospace Sciences Meeting, january 15-18, 1996, Reno, NV.


    Neal, V., et al., 1988, Extravehicular Activity at a Lunar Base, Report on Advanced Extravehicular Activity Systems Requirements Definition Study, NASA-17779.


    Schmitt, H.H., et al., 1992, Spiral Mining for Lunar Volatiles, in Engineering, Construction, and Operations in Space III (SPACE 92), edited by W.Z. Sadeh, et al., v 1, 1162-1170.

    Sviatoslavsky, I. N. and M. Jacobs, 1988, Mobile Helium-3 Mining System and its Benefits Toward Lunar Base Self-Sufficiency, in Engineering, Construction, and Operations in Space (SPACE 88), edited by S. W. Johnson and J. P. Wetzel, p. 310.


    NEEP533 Syllabus

    University of Wisconsin logo

    University of Wisconsin Fusion Technology Institute  · 439 Engineering Research Building  · 1500 Engineering Drive  · Madison WI 53706-1609  · Telephone: (608) 263-2352  · Fax: (608) 263-4499  · Email: fti@engr.wisc.edu

    Copyright © 2003 The Board of Regents of the University of Wisconsin System. For feedback or accessibility issues, contact web@fti.neep.wisc.edu.
    This page last updated August 18, 2003.