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Research on the Use of Space Resources

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Research on the Use of Space Resources Research on the Use of Space Resources William F. Carroll Editor .. ' (NASA-CT;-"132 13) RESEAHCI! ON THE USE OF &84- 16227 ? SPACE RESOUBCES (3et Propulsion Lab.) 326 p HC A15/!!F A01 CSCL 22A Unclas G3,'12 18208 1 Natiorlal Aeronautics and Space Administratfon Jet Propulsion Laborat'ory California Institute of Technology Pasadena, Caiifomia JPL PUBLICATION 83-36 Research on the Use of Space Resources William F. Carroll Editor March 1, 1983 National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pssadena, California The research descr~bedin th~spublication was carried out by the Jet Propulsion ~aboratory,Californ~a Institute of Technology, under contract with the National Aeronautics and Space Adm~nistrat~on. ABSTRACT This report covers the second year of a multiyear research program on the processing and tqe of extraterrestrial resources. The fiscal year 1981 results are re~ortedin JPL Pub1 ication 82-41, dated A~ril15, 1982 and entitled ~xtraterrestrialMaterials processing, chief author ~olfgang H. Steurer. The reporns subsequently identified as NASA CR 169268. A multiyear research plan was also develoged in parallel with the research activity reported here, The plan was submitted to NASA under document JPL D-217, dated August, 1982. The research tasks included: 1) silicate processing, 2) magma electrolysis, 3) vapor phase reduction, and 4) metals separation. Concomitant studies included: 1) energy systems, 2) transportation systems, 3) utilization analysis, an3 4) resource exploration missions. Emphasis in fiscal year 1982 was placed on the magma electrolysis and vapor phase reduction processes (both analytical and experimental ) for separation of oxygen and metals from lunar regolith. The early experimental work on magma electrolysis resulted in gram quantities of iron (mixed metals) and the identi fic6tion of signi Cicant anode, cathode and container problems. In the vapor phase reduction task a detailed analysis of various process concepts led to the selection of two specific processes designated as "Vapor SeparationN and "Selective Ionization." Experimental work was deferred to fiscal year 1983. In the Silicate Processing Task a thermophysical model of the casting process was developed and used to study the effect of variations in material pro2erties on the cooling behavior of lunar basalt. Preliminary indications are that the power source is likely to be the most massive subsystem of an extraterrestrial materials proce:;ing facility. Based on a simple mass pay-back ration figure-of-merit, chemical propulsion systems using near-term technology and oxygen produced at the Moon can transport lunar products to low earth orbit (LEO) for net gains in mass. In the iltilizatiorl Analysis Task, lunar oxygen was identified as the most important early product to be derived from space resources. In the Resource Expl oratior, Missions Task, four important uncertainties (questions) were examined: 1) water at the lunar poles, 2) existance of Earth Trojan asteroids, 3) accessible "near-earth" asteroids, and 4) lunar transient phenomena as indicators of gas deposits, iii PREFACE This report documents the research accomplished during the second year of J multiyear program on the proc lssing and use of extraterrestrial materials. The work was sponsored by the NASA-OSSA Materials Processing Office. During the first year of the program, research was carried out under RTOP 179-29-62, "Extraterrestrial Materials Processing." Resitlts of the fi t-st year' r; efforts are reported in Extraterrestrial Material s Processi np, JPL Publication 82-41, NASA CR 169268, dated April 15, 1982, chief author ;do1 fgang H. Steurer. The work reported here was carried out under RTOP 176-46-20, "Research on the Use of Space Resources." This report, covering work com- pleted during the second year, has been compiled by William F. Carroll and Wolfgang H. Steurer from texts prepared by tne principal technical con- tributors % the program. Editorial changes have been made by the editors, but there as been no attempt to rewrite the text to produce uniform style thr3u;!iout. Names of principal authvrs for individual sections appear in the Table of Contents and in the text in order to identify them with their work, for the readers. In parallel with the research reported here, a multiyear research plan was developed. Details of the plin have been submitted to NASA under document JPL D-217, dated August, 1982. Robert A. Boundy, Task Manager EXECUTIVE SUMMARY R. A, BOUNDY This report documents the technical work completed during fiscal year 1982 under the program Research on the Use of Space Resources (RUSR). It continued the research on extraterrestrial materials processing with emphasis on two analytical and experimental methods for extracting oxygen and metals from lunar, and other, extraterrestrial surface oxides and on analytical studies of processes for mixed-metal separation. Work was also continued on methods for fabricating useful shapes from indigenous oxides (silicates; and a study was initiated on mixed-metal separation, Studies were completed which clarified the constraints and the roles of propulsion and energy technology on extraterrestrial materials processing. Additional studies addressed the limits of feasibility for extraterrestrial products, and the requirements and approaches for missions to extend our knowledge of space resources. Si 1icate Processing Prior analyticai and experimental work on fabricating useful shapes from mixed lunar oxide powders established the attainable properties as a function of compaction, processing temperature, and cooling rate. During this past reporting period a thermophysical model of the casting process has been developed which incorporates temperature-dependent properties of materials, the liberaticn of heat on going from liquid to solid (heat of solidification), and a capability to vary the properties of the mold, 1iquid, and solid independently of one another. This model has been utilized to study the effect of variations in material properties on the cooling behavior of a lunar basalt. The thermophysical model data demonstrate that for material with an emissivity greater than approximately 0.7 the rate-1 imiting step in the heat-transfer process is not the radiation of heat from the surface but rather the rate of heat transfer through the solid (free surface) and the mold. At present the thermal history of the cast basalt has been determined over the time period required for the last remaining liquid to reach the solidus temperature. The model, however, is quite general in nature and can be used to follow cooling behavior of any material for which sufficient pro~ertydata are available. The predictions of the thermophysical casting model are based on the results of the prior experimental coolifig rate studies. Although the present work is discussed in the context of lunar materials and processes, the program scope also includes asteroids and Martian moons as sources of silicate materials for study. Magma Electrolysis Magma means "molten rock." Usually we understand, in t$e context of Magma Electrolysis, a melt composition similar to basalt, or to minerals separated from basalt. Magma Electrolysis, though similar in principle, differs considerably in practice from "electrowinning" of metals as carried out on Earth. Even if we compare only processes conducted at high temperature, there are basic differences. For example, Magma Electrolysis employs no fluorides or other fluxes to lower viscosity and alter reduction voltages. Also, it does not employ a consumable anode (e.g., graphite) to increase the driving force of the reaction or to avoid the expense of a permanent anode capable of withstanding the high temperature of the process. For Magma Electrolysis to work, one must first melt the rock, using heat alone (no flux). This puts the grocess in the range 1500-2000 K, or mors realistically, 1800-2000 K. The strain this puts on materials of construction is extreme. Fortunately, much of this strain can be relieved, on the works scale, by properly designiny the thermal c~radientswithin trle cell. However, on the laboratory scale the problems can be severe. Analysis has shown that semiconduction, as opposed to ionic conduction, must be avoided. Semiconduction is essentially a parasitic process detracting from the manufacture of useful products, namely oxygen and metals. During the reporting period several experimental studies were initiated. Thsse included conductivity measurements of magma samples in molybdenum crucibles and direct-current magma electrolysis experiments. These conductivity experiments established that molten basalt is conductive encugh to support electrolysis, even at temperatures just above the 1 iquidus 1ine. Since these and related studies have shown that the conductivity of magma increases with temperature, the feasi bi1 ity of Magma Electrolysis was thus firmly established. Represeotative experimental data are given in the report. The experimental work on Magma Electrolysis using bitsalt resulted in the production of gram quantities of iron (mixed metal) and the identification of significant anode, cathode, and container problems. These are discussed in detail in the body of this report. Vapor Phase Reduction An alternate process for the extraction of metals and oxygen from basaltic raw material, most abundant in near-space, is "Vapor Phase Reduction." This process employs the gaseous state, either in the form of dissociated vapor, or in
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