OPENING THE HIGH FRONTIER™ FOR A BETTER FUTURE SPACE STUDIES INSTITUTE REQUEST FOR PROPOSALS Design Study: Solar Power Satellite (SPS) Built of Lunar Materials PRINCETON, NEW JERSEY
CONTENTS Chapter Page Introduction 1 Objectives 1 Scale 2 SPS History and Status 2 Lunar Resources Utilization (LRU) History and Status 5 The Lunar Surface Composition and Characteristics 6 Guidelines ....11 Scope ....12 Methodology ....13 Reporting Requirements ....14 Requirements For the Technical Section of the Proposal ....16 How Proposals Will Be Judged ....16 Requirements For the Business Section of the Proposal ....17 Additional Items of Importance ....17 References ....20
A. INTRODUCTION Energy and material resources beyond the Earth's biosphere hold great promise for improving the quality of life on this planet. Ultimately they may also enable humanity to transcend the limitations and constraints of the Earth, by establishing human colonies in space. Before space industrialization becomes a reality, however, a number of critical research projects must be carried out. The Space Studies Institute, through private funding, sponsors such research, of which this Solar Power Satellite (SPS) study is a part. The purpose of this study is to identify the most commercially feasible way to construct a Solar Power Satellite using materials obtained from the Moon. It is anticipated that if this study yields promising results, more extensive studies may be funded. B. OBJECTIVES The principal objective of this solicitation is to identify a preferred commercially feasible way to build an SPS using lunar materials, thus eliminating as far as possible the need for lifting materials from the Earth. The focus of the effort is on SPS design concepts that effectively utilize engineering materials derivable from lunar resources to maximize commercial feasibility. Most of the government-funded SPS studies in the 1976-1981 time period were constrained to consider only launch from Earth. A secondary objective of this study is to identify new ideas and alternatives that are possible when this constraint is removed.
Attainment of the commercial feasibility objective means that high- risk technical solutions should be avoided as should solutions that imply tying up large sums of capital over extended periods of time. C. SCALE The study will be funded at a level not to exceed $35,000, and must be completed, with final report delivered, within one year of contract award. D. SPS HISTORY AND STATUS The SPS allows tapping the inexhaustible energy resource of sunlight in space, to sustain human activities on Earth. The use of nonterrestrial resources for SPS construction could help meet the energy requirements of the growing global population in the 21st century, as the majority of the world's population enters the industrial revolution. Preliminary studies of the SPS concept were carried out from 1968 to 1972, when a plan for an SPS R&D program was outlined by the National Science Foundation and NASA. Between 1974 and 1978 a series of feasibility studies by NASA addressed key technological environmental and economic issues. In 1978 the U.S. Dept, of Energy evaluated the SPS concept with the objective to develop by 1981 an initial understanding of the technical feasibility, economic practicality, and societal and environmental acceptability of the SPS concept. In that concept solar cell arrays were to convert solar energy directly into electricity, and feed it to microwave generators forming part of a planar, phased-array transmitting antenna. The antenna would direct
2 a microwave beam of low power density (25 mW/cm ), precisely to one or more receiving antennas at desired locations on Earth. At the receiving antenna, the microwave energy would be safely, efficiently reconverted into electricity and transmitted to users. An SPS system would consist of many SPS1s in GEO, with outputs at the receiving antennas designed to meet power demands. NASA, in support of SPS evaluations performed by the U.S. Department of Energy, evolved an SPS reference system which assumed that 5 gW of base load output electric power would be generated at the receiving antenna. The reference system was intended as a tool for inquiry, rather than as the design for an SPS which would actually be constructed and commercialized in the 21st century. It was assumed in the reference design that all components of the SPS were to be lifted from the Earth. The Office of Technology Assessment (OTA) carried out an independent review of the SPS concept, which was published in August, 1982 (reference #1). This review was not restricted to the NASA SPS reference design, but covered a broad range of possible SPS concepts as well as many policy issues. The review concluded that SPS is a viable alternative energy system, but that decisions to proceed with further funding depend on the future availability of other energy sources, which could not be adequately assessed at the time of the report. The OTA suggested to Congress that if it decided not to start a dedicated SPS research effort, it might dedicate an agency to track generic research applicable to SPS, to review trends and electricity demand, and to monitor the progress of other electrical supply technologies. Such a mechanism would provide the basis for periodic assessment of whether to begin an SPS research program. Another
option would be to fund a dedicated SPS effort at $5-$10 million, to gather the minimum necessary information, or to fund a program at $20-$30 million to gain the maximum information at the earliest possible time. SPS research in the United States was effectively brought to a halt by the publication in 1981 of a study carried out at a cost of $500,000 by the National Research Council, acting for the National Academy of Sciences. That study focused on the NASA SPS Reference Design, and concluded that the SPS concept was economically impractical because of: 1) Costs of lifting components from the Earth. 2) Costs of fabricating single-crystalline silicon solar cells for the SPS reference system. However, the NAS report stated, "there is a possibility that some future combination of high demand and constrained supply would make a more advanced SPS an important option in the more distant future." A brief remark was made in the NRC Study Report to the effect that the NRC conclusions would not be altered by the substitution of lunar- derived materials for Earth-derived materials. In a subsequent exchange of letters between Dr. Frank Press, President of the NAS, and Dr. Gerard O'Neill, President of Space Studies Institute, the Academy acknowledged that its study had not, in fact, addressed the potential cost savings associated with removing SPS mass constraints and using primarily lunar materials. The studies of 1968-1982 recognized that development of a commercially attractive SPS might require advances in materials and generic space technologies, but not discoveries of new science. Developmental advances of that kind are taking place, for example in amorphous thin film solar cells, materials processing in space, improved magnetrons, waveguide lasers, and automated assembly methods.
The success of the Space Shuttle enlarged space capabilities. In spite of the negative conclusions of the NRC study, the SPS concept is of increasing international interest. SPS related studies are being carried out in Japan, Europe, the Soviet Union and Canada. Several UN Conferences discussed the SPS, and a symposium on the SPS was held in conjunction with UniSpace '82. International technical conferences featured sessions on the SPS, most recently at the I.A.F. Congress, Budapest, October 1983. The Space Solar Power Review, published by Pergamon Press on behalf of the Sunsat Energy Council, communicates important new developments to an international readership. SSI, through the research it funds and through its newsletter, "SSI Update," has supported SPS- related development since the late 1970's. E. LUNAR RESOURCES UTILIZATION (LRU) — HISTORY AND STATUS In 1978, a NASA-sponsored study was conducted to evaluate the extensive use of lunar materials, rather than all materials obtained from Earth, for construction of solar power satellites (reference #2). In this concept, lunar surface material would be mined, brought to high orbit, processed to obtain useful elements such as silicon, oxygen, aluminum and iron, and fabricated into satellites capable of providing useful electrical power on Earth, thereby generating revenue. Potential benefits associated with lunar resource utilization include: 1) Lower energy requirements for delivery of material from Moon to geosynchronous orbit (GEO) than from Earth to GEO, resulting in reduced transportation costs. 2) Significantly reduced Earth material requirements since the majority of construction materials are obtained from the Moon.
3) Much reduced Earth launch vehicle requirements due to lower payload requirements. This results in reduced propellant consumption and atmospheric pollution. Launch vehicle size and flight schedule can also be reduced greatly. 4) Economic and environmental gains accruing from these reduced Earth activities, assuming that equivalent revenue-generating satellites can be produced with lunar resources. The SPS design baseline used for the lunar resources utilization study was a 10 gW satellite assembled in space entirely of Earth-manufactured components (reference #3). Minor material substitution and design modifications were imposed to increase the amount of lunar material utilization to approximately 90% of total SPS mass. With this revised SPS design, the study concluded that LRU was economically competitive with an SPS constructed totally of Earth materials. It is anticipated that an SPS configured specifically to utilize lunar resources will have an LRU mass fraction much greater than 90%, and may therefore represent a commercially attractive investment option. F. THE LUNAR SURFACE — COMPOSITION AND CHARACTERISTICS The surface of the Moon is characterized by large dark areas, designated Maria, and light colored areas generally a kilometer higher in elevation than the Maria. These highland areas are severely cratered as a result of meteorite impacts. Chemical analyses of surface and slightly subsurface soil and rock samples have been performed on material collected by six Apollo and two Luna spacecraft (reference #4). The composition of the lunar crust, insofar as the sampling to date permits, is somewhat similar to that of Earth's in that oxygen and silicon comprise the major elements, and at least eight of the ten most abundant elements in the Earth's crust are also among the most prevalent in the lunar crust. Of the ten most abundant elements in the Earth's crust (see Table I)
Table I: Earth and Lunar Crustal Compositions only hydrogen, at approximately 50 ppm, exists in only trace quantities on the Moon. In addition, sodium and potassium are only one-twenty-fifth to one-tenth as plentiful on the Moon as on Earth. A distinguishing characteristic of the lunar crustal surface is its relatively homogeneous composition as compared to Earth. While there is some distinctive difference in composition between mare and highlands soil, particularly with respect to titanium, iron and aluminum, there is little variation from location to location within each of the two areas, insofar as determined by soil analyses conducted to date.
Unlike the mineral distribution on Earth, no concentrations of specific minerals have thus far been found on the Moon. For example, while the carbon content of the Earth's crust is only twice that of the Moon's 200 ppm versus 100 ppm, large deposits of nearly pure carbon (coal) occur in many locations on Earth, while the Moon's carbon appears to be quite uniformly distributed over the entire lunar surface. The principal lunar-derived elements potentially required for the SPS, namely oxygen, silicon, aluminum and iron, all occur in lunar soil in quantities varying from 5% to 45% by weight, with oxygen and silicon being relatively uniform in distribution regardless of location. Aluminum is more prevalent in highlands soil and iron in mare regions. Other metallic elements found on the Moon, which may be useful as alloying agents in aluminum and iron alloys, or for various other applications, include calcium, magnesium, titanium, chromium, sodium, manganese and potassium. A third source of lunar materials is basin ejecta which consists of a combination of lunar rock and meteoric material. The lunar material is lunar soil which has been lithified by meteoric impact. This material is also referred to under the acronym KREEP, because it tends to be high in potassium (J<), Rare Earth Elements, and Phosphorus. The lunar surface and near subsurface are anhydrous and essentially devoid of carbon and organic material. They consist of rock, complex metal oxides and silicates. As described in the Handbook of Lunar Materials (reference #4), the principal lunar minerals consist of plagioclase feldspars, olivine and pyroxene. Significant amounts of ilmenite occur in mare regions, and small amounts of spinels and lesser amounts of many other minerals are widely distributed over the lunar surface. Table II lists the principal minerals in lunar materials.
Table II: Percent Occurrence of Minerals in Lunar Materials All minerals listed in Table II contain appreciable amounts of oxygen, the element used in all LRU systems concepts as transfer vehicle propellant. Three of the four minerals contain silicon, the element most extensively used in SPS concept designs so far. While aluminum is a basic constituent only of plagioclase feldspars, it may also be dissolved to an appreciable extent in pyroxenes. Iron is present in ilmenite, olivine, and to a lesser extent, in pyroxenes. Depending upon the location, these four elements of interest occur in the concentration ranges shown in Table III. Other prevalent element percentages are also identified. While the concentrations of oxygen and silicon are fairly uniform in their distribution throughout the lunar surface, the concentrations of aluminum and iron vary by factors of approximately 3 to 4, each being highest in areas where the other is lowest. Aluminum is most abundant in highland locations and iron in mare regions.
Table III: Lunar Materials Available The depth of the lunar soil, or regolith, varies considerably with location. The regolith depth of mare surfaces ranges from 2 to 10 meters (references #5 and #6). The highland areas, which are by far the oldest lunar features, have developed regoliths hundreds of meters to possibly kilometers deep (references #7 and #8). Mining, beneficiation, and processing of lunar materials to produce propellants and useful construction materials has received significant study and some experimental work. Recent SSI-funded laboratory experiments by Rockwell International Corporation have demonstrated that chemical processing techniques can successfully separate needed elements with very little loss of reagents. For the purposes of this lunar material constructed SPS study, it should be assumed that if a needed element exists in lunar material, it can be successfully recovered and used for SPS fabrication.
Transportation and logistics techniques for delivery of lunar and Earth materials to the SPS construction site have been studied extensively. Viable lunar material delivery techniques include use of a lunar surface Mass- Driver, or a chemical or ion propelled rocket that employs some (or all) lunar derived propellants. An SPS constructed primarily of lunar resources still requires some small percentage of Earth materials and sophisticated components. Delivery of these Earth supplies is assumed to be accomplished by the Space Shuttle or a Shuttle-derived vehicle, and an upper-stage vehicle of conventional near-term design. For purposes of this study, it should be assumed that these techniques are adequate. No evaluation or assessment of transportation or logistics methods is required as part of this study. Lunar surface or in-space manufacturing methods using lunar materials have also been studied. Favored approaches are highly automated and take advantage of the space environment, i.e., use of vacuum deposition to produce sheet stock, and foamed glass production in zero-gravity. For this proposal, it should be assumed that suitable stock production techniques do exist, and that proposed end products only need be assessed for their applicability to manufacture and/or assembly via automated methods. G. GUIDELINES Nine guidelines are offered, based on a few overall lessons learned in prior studies. These are not intended to constrain new thinking, but a bidder who wishes to modify any of the guidelines should present, in his proposal, the rationale for doing so. 1) The study is intended to identify concepts for production as a commercial profit-making venture on the earliest possible time scale.
2) Accordingly, existing or known technology should be used whenever possible, unless identifiable severe cost impacts result. 3) Transportation logistics and space construction operations are not intended as subjects for the study. Bidders should assume that costs of space transport from Earth to GEO are not greatly different than those attainable through use of Shuttle/Centaur capabilities, i.e., no fleet of high-capacity, low-cost heavy lift systems. 4) The primary power conversion method is not limited to photovoltaic; any solar conversion system may be considered. A preferred design will minimize the total mass of components or materials required from the Earth. 5) Mass should not be a design driver. Mass is not necessarily to be ignored, but rugged, simple, high-mass designs are much more practical for an SPS derived from lunar materials than for SPS concepts based on Earth launch. 6) The hardware making up the design concept should be adaptable to automated production in space or on the Moon. A commercially- feasible concept will require that annual mass throughput of finished hardware from production machines far exceeds the mass of the machines themselves. 7) Power transmission to Earth may use RF or coherent infrared means. Preferred wavelengths fall in the range of about 5 micrometers to 12 centimeters. Some wavelengths in this general range are, of course, precluded by excessive atmospheric absorption. Transmission maximum beam intensities must be non-destructive nominally 30 mW/cnr (300 watts/m^) for RF bands and 200 mW/cm? (2 kW/m^) for IR bands. 8) Earth-based receiving stations need not be defined beyond the area required to capture the beam and the assumed efficiency of conversion of beam energy to electrical energy. (Efficiency estimates are available in existing literature.) 9) SPS size range of interest is 100 megawatts to 5 gigawatts delivered electric power to the power grid on Earth. H. SCOPE The scope of the work is to produce a design for the most practical, commercially viable solar power satellite built primarily out of lunar materials. A cost analysis is not required, but the design will be evaluated for simplicity, low technical risk, and minimized mass of Earth-required materials.
The receiving device on Earth (rectenna or other) is not a part of this study, except as much as its efficiency and the stated power density limitations may affect the satellite design. In producing the satellite design, the following are required within the scope of the study: a) Estimates (with calculations or references) of key technical parameters and reasons for choices. b) Explanation of trade-offs leading to design decisions. c) Identification of potential technology problems, and ways to avoid new development as far as possible. d) Concept description. e) Rationale for concept choice and for sizing choice, if a one- point design is chosen. f) Description of recommended design, with drawings, mass summaries by components and by chemical elements, and supporting calculations. The mass summaries must be subdivided into lunar-available elements and elements which must be obtained from the Earth. I. METHODOLOGY Throughout the study the contractor shall employ certain methodologies deliberately selected to enhance the ultimate usefulness of the study. These include the following: 1) All explicit assumptions shall be justified, or if they rely on previous work, that work shall be fully referenced and the assumptions verifiable and traceable in the literature. In the case when several assumptions are used to derive a subsequent result, the input assumptions must be explicitly stated and referenced and the path to the final result clearly spelled out. In summary, the analysis must be transparent and all results fully traceable so that they can be readily verified at a later time.
2) Parametric designs are preferred over one-point designs. 3) The results of the study must be presented in a clear, readable and intelligent fashion. Graphics should be employed wherever possible, and in particular the selected SPS configuration should be illustrated. 4) Recognizing that funding and time constraints will preclude fully optimizing the design, "best engineering judgment" should be used for design decisions. 5) The study conclusion should include a list of potential problem areas or areas in which insufficient effort has been expended to achieve a reasonable level of confidence in the proposed design configuration. 6) The study should not address environmental issues associated with the energy beam, and for this reason, if a microwave beam is used, the power density at the surface must not exceed 2 2 30 mW/cm , or if a laser is used, 200 mW/cm . 7) The conclusions should include a list of recommendations for further study and logical next steps. This may include a list of possible developmental items. 8) The final design must reasonably be expected to be able to withstand the rigors of the geostationary orbit environment, including the thermal shock of eclipses and the energetic charged particle and plasma environments. 9) SI (MKS) units shall be used throughout. J. REPORTING REQUIREMENTS Periodic progress payments will be negotiated between SSI and the contractor. Payments will be contingent upon receipt of timely reports on the progress
of the study. The following are the minimum reporting requirements: 1) Monthly Letter Progress Reports The contractor shall provide to SSI by first class mail five copies of a brief monthly letter progress report, postmarked no later than the fifth of each month. Letter progress reports should not exceed five double-spaced pages, and should cover the following: a. A brief summary of technical progress and milestones. b. A summary of problems encountered and plans for resolution, c. A summary of effort expended to date. 2) Midterm Report The contractor shall provide to SSI by first class mail five copies of a midterm report, postmarked no later than August 6, 1984. The midterm report shall include draft writeups for all tasks completed by midterm, suitable as first draft material for the final report. The midterm report shall also include a synopsis of plans for completion of the study. The midterm report shall be prepared in narrative format, with graphics as appropriate for complete and clear exposition of work completed. 3) Final Report The contractor shall provide to SSI by first class mail five copies of a final report, postmarked no later than February 6, 1985. The final report shall include the following: a. Executive Summary not to exceed 20 pages; this need not be separately bound. b. Study conclusions and recommendations, with particular attention to recommended further work. c. A narrative description of the results of each study task. d. References used during the course of the study.
Graphics should be used as appropriate for complete and clear exposition of work completed, and to economize on the amount of narrative needed to present results. K. REQUIREMENTS FOR THE TECHNICAL SECTION OF THE PROPOSAL The bidder shall provide a study plan which will include: 1) A summary of the technical approach that will be utilized to access candidate SPS designs. (Bidder shall refer to Section H, "Methodology" for initial guidance in preparing the study plan.) 2) A preliminary outline of the proposed candidate SPS configurations subsystems to be assessed in the course of the study. 3) A list of key areas of research to be conducted during the course of the study. 4) A proposed timetable for the study, delineating the major milestones and reporting points (which shall not be less than two). L. HOW PROPOSALS WILL BE JUDGED The primary goal of the study is to design the most effective, practical, commercially viable SPS built primarily out of lunar materials. The evaluation committee will select the bidder most likely to achieve that goal. Their criteria will be: 1) Clear understanding of the problem. 2) Clarity and quality of the approach. 3) A convincing case that the proposed approach will lead to a design satisfying the guidelines. 4) Professional credentials of the bidder and any proposed associates.
5) Track record of the bidder in previous work. Proposals should not exceed 40 pages (double-spaced, 12-point type). The contract award will be made by February 6, 1984 (four weeks from the deadline for proposals). M. REQUIREMENTS FOR THE BUSINESS SECTION OF THE PROPOSAL The business section should include the following: 1) Name, business address and resumes for the principal investigator and co-investigators. 2) Principal address of the business where research will be conducted. 3) Name and address of the Business Manager of the proposing organization. 4) Detailed budget proposed for the study. 5) Detailed breakdown of responsibilities and work time to be allocated to each named investigator and co-investigators. 6) Preprints and reprints of existing articles and research reports by members of the organization, insofar as they are relevant to the proposed work. N. ADDITIONAL ITEMS OF IMPORTANCE Proposals not accepted for funding by SSI are considered proprietary to the proposing groups and will be returned following completion of the review process. Reviews and evaluations of submitted proposals are proprietary information of SSI. Leveraged Grants: Often government and private funding organizations will support research efforts by university, nonprofit and small business groups on a cost-sharing basis. It is not unusual for the funding agency to request that a contribution on the order of 10% of the program cost
be provided by the recipient. This may be a difficulty for some organizations, especially for small businesses. The Space Studies Institute will consider funding the cost-sharing portion of such research, applicable to the processing of nonterrestrial materials, if a firm case for need of such support is made. SSI should be provided with a copy of the proposal, prior to its submission to the main funding agency, for review by technical advisors to SSI. If the proposal objectives conform to the Institute's aims, SSI may then commit itself, in writing, to provide the cost-sharing contribution pending acceptance of the proposal by the primary funding agency. SSI will not support funding of proposal preparation. A maximum cost-sharing fraction of 20% will be considered and a maximum contribution limit of $10,000 will be imposed. It is possible that more than one proposal may be accepted under this portion of the SSI program. A11 publications resulting from this support must acknowledge the contribution by SSI. Patents, Copyrights, Proprietary Knowledge and Techniques: The Space Studies Institute is funded through private contributions and is a nonprofit organization. Its objective is to advance the leading-edge research programs essential to opening the High Frontier501 of space for human benefit within this century. Some research and development programs funded in whole or in part by the Institute could result in revenue-producing patents, industrial procedures and devices. SSI's intent is to retain a proportion of the profits which may result from licenses, royalties, sales of products, or other successful commercial outgrowths of programs supported by SSI. Any such profits will be used to increase the effectiveness and scope of SSI-supported programs. SSI will require a position in the economic benefits which reflects the
fraction and amount of support supplied to the various funded programs. These agreements will be negotiated on a case-by-case basis and will consider the relative restrictions imposed by funding contributions from other private and governmental organizations. Disclaimers: SSI shall have sole and final authority in granting of contract and may, at its discretion, award none, one, or more than one contract. SSI shall, at its discretion, negotiate changes in scope, time scale, or other revisions either prior to or during the time frame of its contract. If you have any questions about this REP, please contact Erin Medlicott at Space Studies Institute, (609) 921-0377.
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