NEEP602 Course Notes (Fall 1997)
Resources from Space

 

Lecture #20: There's Helium in Them Thar Craters!


Title: Lunar Mine Planning


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

    • 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


    • 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)


    NEW INFORMATION REQUIREMENTS FOR OPTIMUM PLANNING
  • Information Constraints Prior to Mining Equipment Design and Mine Planning
  • Initial selection of most promising mine sites

    • Access cost analysis for various promising areas of the Moon
    • Orbital remote sensing [polar orbit satellite, e.g., INTERLUNE TWO (see Lecture 42)]
      • Surface distribution to within a few meters resolution of the following:
        • 3He concentration (gamma ray emission of neutron absorption)
        • Blocky crater rims (high resolution photograpy)
        • Ti concentration (spectural imaging)
      • Three dimensional distribution (radar) to within 1/2 meter depth of the following:
        • Depth of regolith
        • Block concentrations
        • Density

    Selection of first mine site

    • Surface remote sensing from automated roving platform(s)
      • Instrumented to provide three dimensional in situ analysis at one or more potential mine sites as selected from analysis of remotely sensed data [e.g. INTERLIUNE ONE (see lecture 42)]
        • Physical and geotechnical properties
          • seismic surface (R) wave tomography
          • surface radar
        • Chemical properties
          • mass spectrometry of laser sputtered ions
        • 3He in situ analysis
          • gamma ray emission of neutron absorption
        • Regolith maturity
          • backscatter Mossbauer Spectrometry
        • Natural levels of dust and micrometeroid activity
        • General
          • geological analysis/mapping of walls and ejecta of craters that penetrate to various levels of the regolith
          • high resolution sterro photography and optical spectrometry
        • Calibration of remotely sensed data for the selected sites
      • Coverage sufficient to confirm proved reserves sufficient to justify initial financial investments (see Lecture 4)

    Mine Planning and Mining Concepts for Lunar Resources 

    RECTILINEAR MINING(Cameron, 1992)

    General Concept of Rectilinear Mining
    • Mining progresses linearly, mining rectilinear blocks
      • mining block size will be related to:
        • detailed three dimensional
        • logistics of recovery of volatiles
        • maintenance plan and schedule for miner
    • All mining, beneficiation, and volatile extraction and waste heat recovery contained in miner
    • Interim storage of extracted volatiles in pressurized tanks
    • Tanks transported to central refining location
    • Refining plant and storage and shipment facilities are part of a permanent lunar base
    • Lunar base includes long duration, full service, support facilities
    • New base required when mining operations reach the practical and/or economic limits of support

    Cameron (1992) analyzed the resource base and the minability of Mare Tranquillitatis

    Useful illustration of an early stage of mine planning
    Location of Mare Tranquillitatis
    The regolith covering the 300,000 km2 of Mare Tranquillitatis is a major resource for 3He
    28% has 20-30 wppm He
    65% has 30-45 wppm He
    Mare Tranquillitatis

    Distribution of High-Ti regolith:
    Inferred Titanium Content of Regolith of Mare Tranquillitatis
    The most favorable area for initial mine operations is 85,000 km2 in the northeast

     
    		 Most favorable mine area
      Amount of Minable Regolith
      Percentage of the Total Area of Mare Tranquillitatis Occupied by Major Features
      Minable Regolith and Helium Content of Mare Tranquillitatis


     

    Rectilinear mining plan

     
    		 400m mining blocks

    		 300m mining blocks
      Minable percentage in relation to size of mining block
     
     


    Spiral Mining (Schmitt, et al., 1992)

    Another approach to mining in cratered terrain is that suggested by circular irrigation systems
    Artist view of lunar spiral (NASA art)
    Spiral Mining system

    General Concept of Spiral Mining
    • Mining progresses in a spiral, radially outward from a central, periodically mobile station.
    • Regolith is beneficiated and volatiles are extracted and waste heat recovered in the miner
    • Volatiles piped to central station for refining

    Differences from Rectilinear mining
    • Electrical power and thermal power received from central station
    • Tele-robotic operation possible along optical fiber
    • Extracted volatiles pumped continuously to central station
    • Refined volatiles can be shipped directly to users from central station
    • Unsold volatiles can be stored under central station
    • Routine maintenance and repair handled at central station
    • Less demand on lunar base support means fewer or smaller lunar bases required.

    Mobile Miner Characteristics:
    Mobile Miner Characteristics:

    Central Station Characteristics:
    Central Station Characteristics:

    Standard Duty Cycle (solar thermal only)
    • daytime: mining, beneficiation, and volatile extraction
    • nighttime: volatile refining (use thermal radiation to deep space)
    • with sufficient storage of solar energy (H2 + O2 = H 2O cycle) or with nuclear energy production rates could be doubled)

    Permanent Support Base (Logistics base)
    • location should maximize access to the highest grade, lowest cost reserves and to the regional resource base
    • permanent science base
    • permanent settlement (?)

     
    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.


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