Section 3 is the Market Assessment/Market Analysis section, it contains the following sections:
3.1 Communications Market 3.2 Space Manufacturing 3.3 Remote Sensing 3.4 Government Missions 3.5 Transportation Missions
3.6 Entertainment 3.7 New Missions 3.8 Space Utilities 3.9 Extraterrestrial Resources 3.10 Advertising

Table of Contents for Section 3.8

3.8 Space Utilities
3.8.1 Introduction
3.8.2 Space Utilities Markets
3.8.2.1 General Market Description
3.8.2.2 Space Utility Market Areas
3.8.2.3 Prospective Users Contacted
3.8.2.4 Overall CSTS Needs and Attributes
3.8.2.5 Market Assessment/Business Assessment
3.8.2.6 Conclusions and Recommendations
References
The Full Section Index is at the end of this Section

Commercial Space Transportation Study


3.8 Space Utilities

3.8.1 Introduction

The production of power in space and transmission to terrestrial users has long been recognized as a large potential market for future space transportation systems. Over the past decade, world use of energy has continued a slow but steady growth, averaging about 2.4% per year. This growth is directly related to worldwide standard of living and population, with per capita energy consumption continuing to grow as higher portions of the world population achieve a higher standard of living.

Worldwide, over 11 billion kWh of energy were produced in 1991 from primary sources-petroleum, natural gas, coal, hydroelectricity, and nuclear electricity (Fig. 3.8.1-1). In 1991, three countries-the United States, the former USSR, and China -were the leading producers and consumers of energy. These three countries produced 47% of the world total and consumed 48%. The United States was the largest single producer and consumer of energy, consuming 23% of the world's total energy consumption. Of the U.S. energy consumption, over one-third (36.3%) is consumed to generate electric power. In the United States, the energy power industry's revenues were about $175 billion in 1992, of which about 71% were paid for residential or domestic uses.



Figure 3.8.1-1. World Energy Production by Type

The energy industry has also been the object of significant environmental attention. The primary sources of power for terrestrial use-the fossil fuels of petroleum, natural gas, and coal-have been challenged as being environmentally unfriendly due to their production of carbon dioxide and its probable contribution to global warming trends. Scientific studies indicate that the percentage of carbon dioxide in the Earth's atmosphere has been steadily rising, and since carbon dioxide is one of several gases that tend to absorb reflected solar radiation, the Sun's heat is increasingly trapped within the atmosphere. This process may cause the average temperature of the planet to rise, causing uncertain, but potentially significant changes in global climate. Coal emits 80% more carbon dioxide per unit of energy consumed than natural gas, 20% more than fuel oil, and has particularly been singled out as a concern.

Nuclear power, since it does not produce greenhouse gases, offers a viable alternative to fossil fuels, but has several large political obstacles. The first is the "not in my backyard syndrome" which causes local bureaucracies to place countless obstacles in the path of licensees, sometimes increasing the time and cost of construction to the point at which ground-based nuclear plants are no longer competitive economically with fossil fuel plants. The second is the very real problem of nuclear proliferation and nuclear waste disposal. If these issues could be resolved, nuclear power could provide a major portion of the Third World's energy.

The use of renewable resources, such as solar, wind, geothermal, and hydroelectric resources, can provide some of the required resources. But these sources typically are much higher cost and have difficulty providing the baseload power requirements. While their use continues to grow, in 1990, renewable sources accounted for only about 10% of the total U.S. energy production. Figure 3.8.1-2 indicates the composition of the U.S. power generation in 1990.



Figure 3.8.1-2. U.S. Electric Power Production by Energy Source

Space-based power systems have received much attention for their ability to transmit clean, solar-derived energy to ground stations. But these systems have always been challenged by the provision of low-cost space transportation. Space-based solutions offer potentially attractive options for providing future power.

The space utilities segment considered in the CSTS market study included the provision of power and other services to in-space and terrestrial users. Primarily, the service provided is power, using beamed power techniques to deliver power from a collection and processing point in space to in-space or terrestrial users.

These solar power satellites (SPS) offer inexhaustible, nonpolluting power but require construction of very large space structures. Options to reduce the large size and mass of the satellites necessary for base-power generation include addressing high-revenue niche markets, using extraterrestrial resources to bootstrap the production requirements, and entering into an initial space-to-space power market.

The CSTS analysis indicates that this market segment, under current market conditions, requires a very inexpensive space transportation system to produce a substantial amount of Earth-to-orbit space transportation demand. Of the market areas examined, the most promising is to address a niche market to provide power to high-latitude users using satellites in Molniya orbits. Other market areas, such as geosynchronous Earth orbit (GEO) power satellites and lunar-based power beaming systems, can produce power at market-competitive rates, but require such large upfront investments in development and infrastructure that they are not assessed as competitive in the reasonably near term (less than 20 years). Space-to-space power beaming may be attractive in some applications, but the market for this application does not produce a substantial space transportation demand.

3.8.1.1 Results Summary

The expected demand for energy is expected to grow worldwide. As world population continues to grow, and as the standard of living per capita increases, the demand for energy and electrical power will also grow. As pressures are put on the global energy usage system to reduce the consumption of fossil fuels, and as fossil fuel prices increase, there will be pressure to use more nonfossil fuel power sources. It also should be noted that as more and more electric vehicles are encouraged, electric power usage will also increase. Global energy production has increased by roughly 50% over the last two decades, with fossil fuels (coal, oil, and gas) together accounting for over 90% of production.

In the developing countries, total consumption of commercial energy has almost tripled since 1970, with coal and oil being the major new sources. A further tripling of energy demand in developing countries is expected between 1985 and 2025, with fossil fuels expected to be the major energy source. Environmental damage can be expected to increase as the harder-to-reach and lower-grade deposits are recovered and used. Without the introduction of a new source of energy the fossil fuel deposits will be depleted within the next 40 to 400 years.

Coal is the most abundant of the three commercial fuel types and has proven reserves-to-production ratio of 390 years. Over 60% of world coal reserves are found in developing countries, 50% in China alone. North America has a proven coal reserves-to-production ratio of 201 years. The world's ratio is 40 years. Developing countries account for over 86% of the world's reserves. The world's industrialized countries have a proven oil reserves-to-production ratio of only 10 years, with North America's ratio also 10 years. For natural gas, the proven reserves-to-production ratios are 155 years and 39 years for the developing and industrialized nations, respectively, with each group having approximately 50% of the reserves; the North American ratio is 10 years. As these reserves dwindle, prices will rise and less economically desirable deposits will be recovered.

3.8.1.2 Associated Market Segments (Market Area Mapping)

Market area brainstorming, reviews of the literature, and contacts within the market, suggest that there are at least five different potential market approaches to space power utilities.

Power satellites in geosynchronous orbit provide base power to major population centers. Similar systems were extensively studied in the late 1970s by NASA and the Department of Energy, including significant contractual studies of the systems and the required developments. Staying in a constant position in the sky over the Equator, these very large satellites would beam back large quantities of power to terrestrial receivers. But, since these are very large satellites in a high-Earth orbit, they would require installation of large system infrastructures at high cost. For these satellites to offer a competitive rate of return, the price paid for energy would have to greatly increase.

Power satellites in Molniya-type orbits provide base electrical power to isolated industrial sites and settlements in the high latitudes. Power users in remote locations in the Arctic region currently pay high prices for power. Furthermore, these users cannot use solar power alternatives due to the long winter Arctic nights, and there are distinct environmental problems in transporting and burning fossil fuels into the Arctic regions. The Molniya orbits allow a series of power-generating satellites (either nuclear or solar powered) to hover in the sky over the Arctic regions, where they could deliver power. However, transportation and development costs still require a very low transportation cost for this market area to be viable.

Power satellites in Sun-synchronous orbits provide peaking power worldwide during the 6 a.m. to 9 a.m. and the 6 p.m. to 9 p.m. power peaks. Electric utilities pay higher rates for power provided at peak demand periods. Using a Sun-synchronous orbit, satellites can be positioned to provide power only during these peak periods. Unfortunately, during most of the orbit the satellite is not in position to provide power to a utility (since 70% of the time the satellite is over water), and this market approach does not appear to be viable.

Lunar-based power stations provide base power to major population centers and isolated industrial sites and settlements. During the DOE- and NASA-sponsored GEO SPS studies in the late 1970s it was realized that most of the recurring costs of installing a system of GEO-based SPSs were driven by the transportation costs to ship equipment and components upwards in the Earth's gravitational well. Since that time several studies have generated an interest in producing SPS components and system on the lunar surface or mining the Moon to provide construction material for solar power satellites.

The specific venture examined here is to produce and install large solar power generation and transmission systems on the lunar surface, and transmit power back to the Earth for terrestrial use. While this system offers the potential for large economies of scale in power production, the upfront developments and infrastructure required to accomplish this (including a large lunar base) require an upfront development estimated at hundreds of billions of dollars. Due to this large upfront investment cost, this concept was not justified as a viable commercial venture.

Space-to-space power beaming, as identified from the current literature, and as suggested by several of the organizations contacted in the market surveys, may serve an initial, smaller market by providing power from a centralized power generating station to other co-orbiting satellites. Satellite power generation and storage systems are typically among the most expensive components of satellite systems. However, the market assessment indicates that unless there is a very large concentration of power usage in a very limited location in orbit, this option is not cost competitive with typical distributed satellite power generating and storage systems.

Several other areas were suggested for in-space power utilities. Some, such as the beaming of power from ground-based lasers to satellites to replace power storage systems when the system was in eclipse periods, were judged not to drive space transportation significantly and were not examined in detail.

3.8.1.3 Assessment Approach

The overall assessment approach for this market area followed a two-pronged approach. The first path identified market data to assess the current status and market drivers for the market area. This included contacts with potential users in the market area, identification of key players and regulators in the market, competing technology for the space market areas, and market factors that might drive the feasibility and competitiveness of a space solution.

The second prong of the assessment approach was to develop a business and technical feasibility model of potential ventures in this business area. In particular, these models were developed to answer the question, Is this approach a good business deal? That is, Does this approach fit within current business ranges for investment size and returns? As part of this, technical feasibility assessments were performed on the market concepts; assessing if the project could be built and launched, identifying critical technology developments needed, and examining the production/engineering/technology resources needed for the business venture to see if they will be available in the time period considered.

To be included in the market projection, each market area assessed had to show business and technical feasibility for the market area-and had to match the market survey data sufficiently such that there was some level of validation from the surveyed market data to establish credibility of the projections for the future market opportunities. From these assessments, sensitivities to market and technical assumptions were examined, and a threshold cost below which space transportation had to be offered at provide an acceptable rate or return was determined.

3.8.2 Space Utilities Markets

3.8.2.1 General Market Description

In the United States for example, the market is dominated by municipal and investor-owned utilities. These utilities provide power to consumers and businesses as a ñregulated monopoly," and in exchange for being the only provider of power, have regulated rates and rates of return. This regulation is typically provided by a state or municipal public utilities commission representing the public to which power is provided.

Current U.S. electrical power projections for 2010, based on utilities planning data (see Fig. 3.8.2.1-1), show a reference capacity of 880 gigawatts, of which 352 GW will be from coal, 282 GW from oil and gas, 102 GW from nuclear, and 144 GW from renewable and other (primarily pumped storage hydroelectric with some waste heat and process gases). In 2010 the average price for electricity in the United States is projected to be 6.9¢ per kWh, of which capital cost represents 2.1¢, fuel represents 2.7¢, and O&M represents 2.1¢ per kWh1. During the period from 1990 to 2010 U.S. utilities plan to retire 47 GW worth of capacity and add 195 GW worth, primarily gas-fired turbine-powered generators with very limited renewable energy sources.

Outside the United States, the electrical market is only half as large as the U.S. market but prices are higher. German consumers pay an average of over 16¢/kWh and the Japanese residential rate is almost 23¢/kWh3. Current expenditures from the 117 investor-owned U.S. utilities are about $45 billion per year in the United States for new power-generating capability. However, about 80% of this new generating capability is being paid for out of current operating revenues.

The current drivers for the U.S. power industry are dictated by the regulatory structure of the industry, and the Public Utilities Regulatory Act (PURPA) of 1978, which requires public utilities to buy power at a premium over the "avoided" cost of installing equivalent capability themselves. Some utilities now purchase up to 40% of their energy from such independent power producers.

The current PURPA contracts were negotiated on a price basis that was established in the late 1970s; the negotiated rates are based upon late 1970s projections of energy costs. This has allowed such alternative energy sources as solar thermal, solar photovoltaic, wind, and geothermal to sell energy to the utilities as successful private ventures.

However, the prices being paid to independent power producers are gradually being renegotiated to current energy costs and expectations as the existing contracts are renewed. This is expected to reduce the prices paid for some types of these renewable energy ventures and may substantially reduce their expected returns. Even with the decrease in prices paid for these alternative energy sources they are predicted to be cost competitive with fossil fuels after the year 2000, but they are not yet under serious consideration by the U.S utility companies2 as primary sources of power.


2010
1990ReferenceHigh Growth EconomicLow Growth EconomicHigh Recovery Oil&GasLow Recovery Oil&Gas
Net demand a (billion kWh)
Sales by Utilities2,7133,7303,9273,5233,7243,731
Self-Generation by Nonutilities b 111182203171184183
Net energy for load (billion kWh)2,9153,9844,1863,7693,9803,983
Net electricity imports25454545454
Purchase from nonutilities106408549286387435
Generation by utilities2,8083,5213,5833,4293,5393,494
Generation by fuel type - utility and nonutility(billion kWh)
Coal1,5932,0322,1791,9081,9672,122
Oil122174168170173179
Gas364735786644798639
Nuclear577636647636636636
Renewables/Other c71536554527536536
Total3,0264,1124,3353,8854,1104,112
Capacity - utility and nonutility (GW)
Coal305352377332341370
Oil/Gas216282302257293264
Nuclear100102105102102102
Renewables87113116112113113
Other233131313131
Total732880930834879880
Fossil fuel consumption - utility and nonutility (quadrillion BTU)
Coal16.420.321.619.419.821.3
Oil1.31.81.71.71.81.9
Gas3.56.77.06.27.26.0
Cumulative Utility Retirements from 12/31/90 (GW)--4747474747
Cumulative additions from 12/31/90 (gigawatts) -- 195245149194195
Utility (announced)--5959595959
Utility (not announced to date)d--6586436762
Nonutility (announced)--2121212121
Nonutility (not announced to date)--5078264753
Average electricity prices e (1991 cents per kWh)
Capital2.92.12.12.02.12.1
Fuel1.72.72.92.52.62.8
O&M2.22.12.02.22.12.1
Total6.86.97.06.76.87.0
a Demand is expressed net of demand-side management.
b Nonutilities include cogenerators, small power producers, independent power producers, and all other sources that produce electricity for self-use or for delivery to the grid, except electric utilities
c For utilities, renewables include pumped storage hydroelectric plus a small quantity of petroleum coke. For nonutilities, this category also includes waste heat, blast furnace gas, coke oven gas, and anthracite culm.
d Additions in this category are primarily facilities whose construction is projected beyond 2000, which utilities and nonutilities are not required to report to EIA.
e Prices represent average revenue per kWh of sales over all customer classes.
Note: Totals may not equal sum of components due to independent rounding.

Figure 3.8.2.1-1 Predicted U.S. Electrical Energy Capacity and Consumption

It should be noted that power produced by the alternative energy sources is typically rated and paid for on a sliding hourly price scale. This scale recognizes that the demand for power typically varies over the space of a day, peaking in the early afternoon, and declining to a low ("baseload") demand level during the night. Alternative energy sources, such as wind energy, may not produce power at the optimum times and their revenues are reduced.

The demand for electrical power in the United States is continuing to increase, although the rate of increase has fallen, and the market projections reflect this. Figure 3.8.2.1-2 indicates the historical change in the projected demand level.



Figure 3.8.2.1-2. Historical Data Show That the Demand Increase Has Fallen With Time

One of the most significant changes in the market over the last decade or so has been the development of a cadre of independent power producers. Under the PURPA, nonutility power producers were given the right to build their own generating plants and compete with utilities to provide power at the lowest cost. These firms raise their required funding in the commercial markets and then invest it into power systems on a global basis to serve new users. The systems they install are then operated to produce market rates of return. This has been very attractive, as state and local regulators have capped the rates of return for public utilities.

The growth of these independent power producers has been driven by a large increase in the power needs in the developing world, although they also have significant investments in the developed countries as well. The International Finance Corporation, the lending arm of the World Bank, estimates that $100 billion in annual investment is required to meet existing power requirements in the developing nations. General Electric Company, the largest provider of power generating systems, estimates that more than 460 billion watts of power will be ordered in Asia during the next decade for roughly $300 billion. China alone currently spends about $10 billion to $14 billion in new electric power generation facilities. As a point of comparison, Southern California Edison, a major U.S. public utility contacted in this market assessment produced 81.3 billion kWh in 1993, or had a generating capacity of about 9 billion watts. The Asian market represents about 5 SCEs per year, for at least a decade.

In recognition of this market potential, billions of dollars in capital in investment are being attracted to this market. As an example, in January 1992 a $10 billion investment pool named "Global Power Investments" was set up with an initial $450 million from GE Capital Corp., the Quantum Group, and International Finance Corporation (the investment arm of the World Bank).

This rate of growth in electrical power demand is not expected to slacken in the next several decades. The worldÍs population has doubled in the last 40 years and may double again in the next century, approaching stability at 11 billion by the year 2100. Most of this increase will take place in developing countries. China is planning to build more than a dozen plants a year, India will add 5 plants a year, and even Japan's mature economy and population will be adding more than 50 plants to build a reserve of power the way U.S. utilities do.

Almost all of these new plants will be based upon fossil fuels. As a result of the developing countriesÍ increased populations and fossil fuel usage they are expected to account for more than half of the global increase in CO2 emissions by 2025.

Part of the high reliance upon fossil fuels is driven by the rapid returns needed to provide commercial rates of return of 16% to 20% per year, but a large reason is the large reserves of local coal or oil to provide a local source of energy supply. Market contacts have indicated that as of this time, environmental concerns are not a major driver for the type of power plant needed, and that local environmental regulations are not strict. Furthermore, the price pressures of the competitive bidding for these commercially procured power systems place a premium on lowest price production. But the international lenders that back the financing of these plants on 10-year-plus basis, place some environmental standards on these ventures.

The principal issue against a growth market for satellite-based power is the relative cost and risk of space power versus conventional power sources. There are currently no perceived energy crises in any of the developed nations, and a large functioning infrastructure is in place that uses existing energy sources. There is also a large margin between the cost and price of fossil fuels that can be exploited to fight a new major competitor such as space-based power satellites. On the horizon, ground-based solar electric power is about to enter mass-production, which will offer costs in the range of $2/watt installed3. This will provide a low nonrecurring cost entry to the Third World market and further dampen any enthusiasm for SPSs, which has a very large nonrecurring cost before any power is delivered. On the positive side, space-based power offers tremendous operational flexibility and security to its owners. It is possible to service widely dispersed sites that have invested in relatively low-cost receiving antennas, called rectennas, with the same constellation of satellites. Once in place, no outside fuels or materials are required to maintain the flow of power, and solar power is environmentally clean and inexhaustible.

Short of waiting until the world runs out of fossil fuels, there appear to be only two ways to force space power into the energy equation. The first and best is to offer energy cheaper and in a more convenient form than the competition. This appears to be possible but not at the low power prices currently enjoyed by the United States and Canada. The second is through legislation, where fossil fuels are taxed to limit their use and to clean up the environment. This is possible but not highly likely in the near future.

It is expected that the current concerns about fossil fuel emissions of greenhouse gases and other environmental effects will not abate, and will grow stronger with time. While it is not expected that significant impacts upon the coal, oil, and natural gas-powered electric utilities will appear this decade, such considerations will increase in the 2000s and beyond. This offers a market opportunity for increased use of large solar power systems.

3.8.2.2 Space Utility Market Areas

3.8.2.2.1 GEO Solar Power Satellites

3.8.2.2.1.1 Introduction
Large power satellites in GEO were extensively studied in the late 1970s by various organizations, and in several large contractual studies from DOE to Boeing Aerospace and Rockwell International. These satellites were designed to provide high power levels (tens to hundreds of gigawatts) to terrestrial receivers by converting incident solar energy into microwave power for transmission to large rectenna sites on the Earth. The power was then transferred into the terrestrial power grid. These satellites were primarily designed to serve the base-power needs for terrestrial users. A subsequent preliminary study was performed by General Dynamics Corporation into the utility of using lunar resources to provide components of the GEO SPSs. A low level of enthusiast-fueled effort in analysis and development of GEO SPSs has continued since that time.

3.8.2.2.1.2 Study Approach
The past studies were examined, and wherever possible, past participants and principles in these studies were contacted. With the benefit of current technology and perceptions after almost 20 years of technology advancement, the technical and market feasibility of these systems were reexamined. The following steps were taken in assessing this market area:

  1. Literature search of the available literature on GEO solar power satellites.
  2. Contacts with participants and leaders of past studies.
  3. Assessment of changes in the market assumptions and the underlying technology readiness, and assessment of competing technical solutions.
  4. Development of analytical models of GEO SPS options, and assessment of the market opportunity.
3.8.2.2.1.3 Market Description
3.8.2.2.1.3.1 Description Market Evaluation
The market for GEO SPSs consists of the major electric utilities. Current prices charged for electric power in the United States average about $0.065 per kWh. The large GEO satellites, which stay stationary in the sky over the Equator and which are in sunlight virtually 24 hours a day, seem to be best suited for providing base load power, in direct competition with nuclear or fossil-fueled power plants. Outside the United States, power prices charged are higher, with some markets having prices of up to $0.20 per kWh.

3.8.2.2.1.3.2 Market Evaluation
At the time of the previous extensive conceptual studies in the late 1970s, energy costs for fossil fuels had been escalating rapidly due to political and economic pressures on existing terrestrial supplies. These market assumptions have since changed. Crude oil, coal, and natural gas prices have all dropped. Since the early 1980s the price of oil, for example, has dropped almost 50% in constant (inflation adjusted) dollars. The price rises experienced through the 1970s and expected to continue through the 1980s did not occur. As a composite, energy prices have dropped by about 50% through 1990, since they peaked in 1982 (see Fig. 3.8.2.2-1).

Figure 3.8.2.2-1. Fossil Fuel Prices Composite Energy Prices

Similarly, these studies assumed that very optimistic space transportation systems would be developed and put in place to support the GEO SPS. These projected space transportation systems were expected to provide transportation at the cost of about $80 per pound (in today's dollars). In this current market assessment, space transportation systems have been assumed to have a variable cost per pound, and the concepts have been assessed to see under what $/lb to LEO a GEO SPS system would be viable.

3.8.2.2.1.3.3 Market Assessment
Figure 3.8.2.2-2 indicates the CSTS assessment of the current state of the GEO SPS satellite concept, comparing expected internal rate of return (IRR) after 20 years of operations versus the price for energy paid for power from the GEO SPS system.

Figure 3.8.2.2-2. 20-Year IRR Versus Price of Power Sold (60-Satellite System)

To fully assess the system, both a single GEO solar power satellite system and a fully operational system of 60 satellites were examined. (The advantage in the larger system is that any nonrecurring development costs or investments would be spread over the larger number of satellites).
Figure 3.8.2.2-3 indicates the rate of return for a single power satellite case.

Figure 3.8.2.2-3. 20-Year IRR Versus Price of Power Sold (One Satellite)

GEO satellite concept costs shown are unit costs, based upon current technology assumptions, which are used to update the major study efforts of the late 1970s. Unfortunately, technology needed for such large satellites has progressed little versus the assumed technology in the 1980-vintage studies.

Also in contrast to the earlier studies, the development cost for an Earth-to-orbit transportation system was removed, and only included as a variable $/lb price to get to LEO. Figure 3.8.2.2-4 indicates the sensitivity of these results to LEO transportation cost.

Development costs were retained for other elements of the needed infrastructure, such as an orbital transfer vehicle and the GEO construction system, and for the satellite hardware itself. Nontransportation development costs were estimated based upon the 1978 DOE contract studies, at about $40 billion in 1993 dollars.



Figure 3.8.2.2-4. IRR for Selected Launch Costs

Key assumptions in this market analysis included:
  1. Power rate (unless otherwise noted): $0.06/kWh.
  2. Satellite operational life: 30 years.
  3. Power at ground interface (per satellite): 5.0 GW.
  4. Mass to LEO required to construct first satellite: 54,612,535 kg.
  5. Average mass to LEO required to construct each additional satellite: 42,096,498 kg.
  6. Mass to LEO required for satellite operations: 10,083,157 kg per satellite/30 years.
  7. Satellite operational life: 30 years.
  8. Launch capability per year (maximum): 90,000,000 kg.
  9. Interest rate: 5.5%.
  10. DDT&E costs distributed over the first 5 years according to the following schedule:
    • Year 1-10%
    • Year 2-20%
    • Year 3-30%
    • Year 4-30%
    • Year 5-10%
  11. Production starts in year six.
  12. Satellites produce power for 100% of their operational life.
  13. A 0.5% insurance rate is charges to the following items:
    1. Satellite: construction and O&M-RCI.
    2. Space construction and support: construction and O&M-RCI.
    3. On-orbit transportation: construction and O&M-RCI.
    4. Launch costs (HLLV & PLV).
    5. All dollar figures are given in 1993 dollars.
    6. Earth to LEO launch costs are calculated on a $/lb basis.
These results are reasonable assuming this project is equivalent to major utility operations, but very optimistic if a commercial venture is assumed, as per an independent power producer. An independent power provider raises money on the commercial capital markets, and would see a higher cost of money, and would have to provide a higher rate of return (typically 20% IRR after 10 years of operations) to be competitive with other commercial ventures also looking for financing.

The difference in these results from the past studies in the late 1970s is results primarily from different expectations for the cost of fossil fuels in the future and the removal of the assumption of very low-cost space transportation. In contrast to the past contractual studies, we did not assume that a new, dedicated space transportation system was developed solely for this usage. This is a conservative assumption, since this decreases the cost to the GEO SPS system and would tend to improve expected returns.

This result does not indicate that a GEO solar power satellite venture is commercially viable at any reasonable $/lb in LEO transportation price unless energy costs greatly increase. Even if transportation costs to orbit are free $0 /lb to LEO), it will take about 30 years just to recover the sunk investment at current energy prices. However, if energy costs increase, such that power could be sold at $0.50-1.00 per kWh, then these ventures might be more viable.

3.8.2.2.1.4 Market Infrastructure
Since this market area is not viewed as commercially viable at current energy prices and costs, no transition to establish the large-scale effort was developed. However, there is significant infrastructure needed to be put into place before a GEO SPS venture is established. Major infrastructure elements are needed to assemble major subelements of the satellites in LEO, then to transfer them to GEO, assemble them into working power stations, and then support and maintain these facilities. On the ground, rectenna sites to receive the beamed power from the GEO power satellites and distribute it into the utility grid are also required. Figure 3.8.2.2-5 summarizes the required infrastructure elements needed. Costs for all these elements are included in the market assessment.

3.8.2.2.1.5 Prospective Users
The primary users for this system are the major utilities, with the GEO SPS system providing baseload power. The costs involved in this venture are substantial, with development costs in the tens of billions of dollars. This level of required investment and the current level of technical risk in such a system removes it, however, from the consideration of conservative power system investors. To reduce the level of financial risk to any individual investor, a syndicate of investors must be developed, or government financial backing provided.

Typical individual projects may include up to $500 million or so in financing from any one equity partner, so an investment syndicate for a GEO SPS venture may involve dozens of partners, which was described as "very challenging" in the market contacts. Similarly, the time scale of investment and the great uncertainty in returns may force the government to provide underlying finances and key market guarantees. At this point, since this venture does not appear commercially or financially feasible, only the government can be seen as a prospective user.


LEO assembly nodeStores and assembles major subelements before transport to GEO.
GEO transportation systemTransports cargo and crews to and from GEO. Supports GEO servicing and maintenance missions.
GEO assembly nodeAssembles major subelements into power satellites. Supports crew as required for assembly. Supports servicing and maintenance operations during operational phase.
Terrestrial receiving site (rectenna)Receives beamed power from GEO solar power satellites. Converts beamed power to output electrical power and transfers power into utility grid.

Figure 3.8.2.2-5. Required Infrastructure Elements for GEO Solar Power Satellite System

3.8.2.2.1.6 CSTS Needs and Attributes
The market analysis of GEO solar power satellites indicated the concept was not commercially viable, independent of space transportation system cost. Given the large investments required and the low price for power currently prevailing, the market analysis of GEO solar power satellites indicated the concept was not commercially viable independent of space transportation costs.

3.8.2.2.1.7 Business Opportunities
No viable business opportunities in this market segment were defined at this point.

3.8.2.2.1.8 Conclusions and Recommendations
The GEO SPS market area was defocused at this time, due to an assessed lack of market viability. Effort continued looking into niche markets or where economies of scale could offer the promise of better returns for other ventures.

3.8.2.2.2 Power Satellites in Molniya orbits

3.8.2.2.2.1 Introduction
Two different nonsynchronous orbit solar power satellite options were examined. Selection of the orbit is crucial to space-based power satellites performance and system cost. A high altitude requires large antennas and a low orbital period yields short dwell times. The orbit options examined in this market study are summarized in
Figure 3.8.2.2-6. Orbits other than GEO are of interest, even though they require multiple satellites to service each rectenna site, because they require less propulsive energy or provide smaller transmission distances (which reduces antenna size and power requirements). The GEO SPS was described in the previous section.

Orbit Time % View is Under 35 degMax Distance(km)Orbital Inclination(deg)
Geosynchronous10035,7850
12-hour Molniya9440,165*63.4
8-hour Molniya8527,560*63.4
4-hour Molniya4712,530*131.3
3-hour Molniya308.065*115.2
2-hour Molniya51,820102.1
* Based upon maximum eccentricity for a perigee altitude of 300 km

Figure 3.8.2.2-6. Orbital Options for Solar Power Satellite

Figure 3.8.2.2-7 compares the relative viewing angle between the rectenna and the space-based power satellites for four orbital options. The plot is generated using the maximum allowable eccentricity for each orbit defined by a 300-km perigee altitude and assuming that the rectenna is directly under the satelliteÍs apogee.



Figure 3.8.2.2-7. Time Spent Within the Maximum Viewing Angle

Based upon a 35-degree maximum viewing angle envelope, the distance between the rectenna and antenna versus time is plotted in
Figure 3.8.2.2-8. Note that the Molniya orbits (highly elliptical orbits, inclined at 63 degrees to the equator, with an integer period of 24 ,12, 8, 6, or 4 hours) will require fairly large antennas because of their apogee height, but require few satellites because of their long dwell times at zenith. The Sun-synchronous satellites will have to be numerous because of their very short dwell times over the rectenna but only need small antennae. Note that if we launch into 4-hour Sun-synchronous orbits to provide peaking power from 6 a.m. to 9 a.m. and 6 p.m. to 9 p.m., then only four satellites are necessary.



Figure 3.8.2.2-8 Distance to Satellite During Viewing Envelope

The 8-hour Molniya orbit is a compromise between maximum distance and useful percentage of the orbit. As shown in
Figure 3.8.2.2-9, it also seems to be very advantageous in terms of location of ground sites. With Molniya orbits, three rectenna sites in North America, Europe, and the Far East can be serviced with four satellites, and little time is spent over southern oceans where there are few markets. Ground site locations shown in the figure are arbitrary and are intended to show footprint size at various latitudes. Two of the ground site locations, Japan and central Europe, are currently buying high-priced electricity and would be definite candidates for space power. The third ground site location, central Canada/Alaska through North Dakota, currently burns predominately natural gas for power and might prove to be a hard sell. An abundance of electrical power might encourage industrial expansion there.

This figure indicates the coverage area for a typical Molniya orbit SPS, during the power transmitting portion of the orbit over Europe. (Since the satellite is in an 8-hour orbit, it will be in optimum power-transmitting position every 120 degrees of latitude. This allows it to serve the Alaskan region, northern Europe, and central Siberia.) The elliptical-shaped blob over Europe is the area visible to the satellite during the power-transmitting potion of the orbit. System customers could be located anywhere inside the boundary. This implies that a large number of prospective users are out there and must be identified.



Figure 3.8.2.2-9. Possible Ground Station Locations for Solar Power Satellites in 8-Hour Molnyia Orbits

Remote site electrical power in Alaska currently runs as high as $1 per kWh, with average rates in the 10¢ to 15¢ per kWh range.
Figure 3.8.2.2-10 indicates the percentage of power provided to Alaskan users as a function of price, based upon data from the Alaska Power Authority.



Figure 3.8.2.2-10. 1992 Alaskan Power Sales as a Function of Price

This makes space-based beamed power a lucrative alternative if transportation costs can be reduced to less than $100/lb. To maximize the payback on these relatively small power systems, the transmitting frequency was increased from 5.45 GHz to 15 GHz in order to minimize the size of the rectennas that receive the power on the ground. This results in an additional 2% transmission loss under normal weather conditions but up to 50% loss during worst case rain/snow conditions (25 mm of rain per hour, equivalent to a thunderstorm). This would require major plant operations to cease or switch to temporary power during heavy rain or snow. This may not be acceptable if SPS-provided power is used for baseload power. Other assumptions remain the same as with the GEO SPS.

3.8.2.2.2.2 Study Approach
To examine the possibility of using smaller power satellites in regions where a higher price for power is being paid, conceptual Molniya orbit solar power satellites were developed and tested to see if they offered the possibility of attractive rates of return. This was used to assess the likelihood of such a venture being a market for future space transportation services. Both nuclear- and solar-powered options were investigated. The following steps were taken to assess the market area:

  1. Defined market potential user demand as function of price for power.
  2. Developed conceptual solar and nuclear powered satellites.
  3. Analyzed options in time-phased business model to assess achievable rates of return.
  4. Analyzed transportation market potential.
3.8.2.2.2.3 Market Description
3.8.2.2.2.3.1 Description Market Evaluation
As described previously, the market addressed is to provide power to high-latitude power users who are currently paying higher than average prices for electrical power. Parametric data are developed to assess the size of the market as a function of price.

It is important to note that the users of this power are widely geographically distributed. To overcome this, it is important that the SPS system be able to provide power to them. Furthermore, since the satellite system provides power to different regions of the globe, with different distributions of users, it is important that the system be capable of "steering" its beam to these different sets of users, with different power-level requirements at each site.

3.8.2.2.2.3.2 Market Evaluation
Using the Alaskan power data to represent the high-priced end of the market, the European and Japanese data to represent the mid-priced power market, and the American and Canadian markets to represent the low-priced power requirements, we came up with a high, medium, and low estimate of future power market capture as a function of delivered power price (including 2¢/kWh for operations and maintenance). In this case, the high estimate represents 90% probability that this level of new power production can be captured at a given price; the medium estimate is for a 50% probability that a greater level of new power can be captured (at the same price); and the low probability estimate is for a 10% probability that even a larger portion of the new power market can be captured at the same price.

This market demand data are shown in Figures 3.8.2.2-11 and -12, below. These capture estimates should be conservative because (1) prices and consumption are continuing to escalate and (2) we are assuming we capture only 20% of new construction at equivalent power prices (medium probability).



Figure 3.8.2.2-11. Space Power New Construction Market Capture


Figure 3.8.2.2-12. Space-Based High-Latitude Electrical Power Demand Versus Price

Note that the power market saturates at very low prices and has a tailoff at high prices caused by the very high prices currently paid by very remote users such as fishing villages and mining camps. An alternative approach, not assessed here, is to beam power from the ground using reflectors in high orbit to transmit microwave power from hydroelectric resources in the underdeveloped equatorial regions to the more developed northern latitudes. This approach makes sense from a technical standpoint, but has marginal cost benefit and real political issues. Once the power plants are in place, there would be little a developed nation could do to stop local takeover and local exploitation of a valuable resource.

3.8.2.2.2.3.3 Market Assessment
Both nuclear- and solar-powered satellite options were investigated. For a normal technology growth 2005 solar power plant (3.4 Kg/kW) described below in Figure 3.8.2.2-13, the supply price per kWh at >$50/lb is always too high to match demand, so we get curves like those shown in Figure 3.8.2.2-14, where the supply and demand lines never cross. If we extrapolate more advanced solar array technology available in 2005, to where the delivered specific power is 2.0 kg/kW, then we do get a match between supply and demand at about 1,500 MW/sat and 12¢/kWh.


Apogee altitude, km27,250Diameter of rectenna, km0.93
Perigee altitude, km600Peak power intensity, mw/cm233.05
Semimajor axis, km20,303Rectenna cost, $M34
Orbital period, hrs8.00Solar array learning curve0.7
Delta V1, km/sec2.17Solar panel TFU, $/m*m250,000
Delta V2, km/sec1.42Specific cost of array, $/m*m343
Upper stage Isp, sec470Specific array cost, $/kW$11.16
One-way mass ratio1.60Cost of power gen., $M128
Busbar power, Mw7,179Cost per satellite, $M1,261
Transmission freq, GHz15Visibility per site, minutes360
Grid conversion efficiency0.9No of satellites reqd4
Rectenna efficiency0.9Upper stage lambda prime0.85
Transmission efficiency0.96Mass per satellite, kg54,331,613
Klystron/magnetron eff.0.85
Power conditioning eff.0.95Upper stage prop mass, kg37,396,520
Satellite power, Mw11,432.88Total mass/satellite to LEO, kg91,728,133
Solar conversion eff.0.25LEO delivery cost, $/Kg110
Collector area, km*km37.18LEO deliv cost/satellite, $M10,090
Concentration ratio100Total launch costs, $M40,360
No. of 1mX 1m solar cell panels371,801Total satellite purchase, $M5,044
Power/panel30.75Total number of sites215.4327
Spec. power of conv, Kg/kW3.4Average power per site, Mw100
Power generation mass, Kg38,871,795Total rectenna purchase, $M7,243
Klystron subarray mass, kg15,422,956System recurring cost, $M52,647
No of 50kW klystrons271,531Busbar $/kWe73
50 kW klystron TFU$2,500O&M cost, ¢/kWh2
Klystron learning curve0.8230 year capital cost, ¢/kWh0.93
Klystron ave price$66Power price, ¢/kWh9
Antenna diameter, m750Yearly revenue, $M13219.38
Antenna mass, Kg36,862Systems DDT&E8,000
Antenna cost, $M1,11620-year IRR20%

Figure 3.8.2.2-13. Solar-Powered SPS With 3.5 kg/kW Solar Array in 8-Hour Molniya Orbit


Figure 3.8.2.2-14. Supply Versus Demand for Normal-Growth Technology SPS in 8-Hour Molniya Orbits

The nuclear-powered option, described in
Figure 3.8.2.2-15, has similar issues and we have baselined liquid-droplet radiators for the Brayton power cycle to keep the power plant mass low.


Apogee altitude, km27,250Specific cost of Brayton PP, $/kw100
Perigee altitude, km600Nof 600 MWt reactors in 20 yrs956
Semimajor axis, km20,303600 Mwt reactor TRU, $M^600
Orbital period, hrs8.00Reactor learning curve0.8
Delta V1, km/sec2.17Avg cost of nuclear reactor, $M$62
Delta V2, km/sec1.42Cost of power gen/satellite, $M$653
Upper stage Isp, sec470Cost per satellite, $M$819
One-way mass ratio1.60Visibility per site, minutes360
Busbar power, Mw1,000No of satellites reqd4
Transmission freq, GHz15Upper stage lambda prime0.85
Grid conversion efficiency0.9Upper stage prop mass, kg2,161,817
Rectenna efficiency0.9Total mass satellite to LEO, kg 5,302,617
Transmission efficiency0.96LEO delivery cost, $kg110
Klystron/magnetron eff.0.85LEO deliv cost satellite, $M583
Power conditioning eff.0.95Total launch costs, $M2,333
Satellite power, Mw1592.58Total satellite purchast, $M3,277
Spec. power of conv, Kg/Kw0.2 Total number of sites 30
Power generation mass, Kg318,516Average power per site, Mw100
Electric generator mass, Kg637,032Total rectenna purchase, $M1,009
DC-RF w/substructure, kg2,148,390System cost installed, $M6,619
Power limited antenna dia, m320Incremental installation rate1
Antenna diameter, m750Busbar $/kwe2,206
Antenna structure, Kg36,862O&M cost, ¢kWh2
Antenna cost, $M 166System DDT&E/2, $M5,000
Diameter of rectenna, km0.93Power price, ¢/kWh12.4304
Peak power intensity, mw/cm233.06Revenue/year, $B2.74
Rectenna cost, $M3420-7ear IRR20%

Figure 3.8.2.2-15. Design Characteristics for Nuclear-Powered SPS or Remote Sites in Molniya Type Orbits

Space-based power satellites and antenna masses were derived from work done by the Seattle Lunar Utilization Group. Some other important assumptions include-

  1. Pellet-bed uranium-fueled nuclear reactor.
  2. Thermodynamic Brayton cycle with recuperator (2,000K max, 38.7% cycle efficiency).
  3. Liquid-droplet radiator-utilizing liquid tin (200 micron droplet radius).
  4. Transmission frequency of 2.45 GHz, and rectenna diameter of 1 km.
  5. Commercial power rate-operating expenses = .05 ¢/(kWh/day).
Figure 3.8.2.2-16 illustrates some of the design characteristics of the nuclear power satellite system. This system is designed to be modular, in chunks sized to match the launch vehicle capabilities. Individual, but complete, packages would be delivered to the destination orbit where they would be joined with other elements there into an operational satellite. This offers the ability to allow for individual system failures without significant degradation of the overall system capabilities. This approach also reduces the need for on-orbit construction to a "plug and play" automated assembly operation.



Figure 3.8.2.2-16. Space Nuclear Power Satellite for High-Latitude Remote Sites Concept

In comparing solar- versus nuclear-powered satellites, there are political as well as technical and cost aspects. The political ramifications of putting a nuclear reactor into Earth orbit will be significant. In fact, the safety requirements of such a system could easily be the highest cost factor of either concept. But, from a raw cost and transportation requirements standpoint, it appears competitive with solar arrays.
Figure 3.8.2.2.-17 compares 100 MWe, 500 MWe, and 1,000 MWe satellites.

Both options look very attractive, with solar power being more advantageous at the lower power levels due to its lower development costs. The addition of the kinds of safety and environmental regulations that the ground-based nuclear power industry has had to deal with could make the nuclear option less competitive.


100 MWe500 MWe1 GWe
NuclearSolarNuclearSolarNuclear Solar
Satellite mass (Mg)703102001,560350 3,120
Satellite cost ($M)7301,3502,0606,7503,530 13,500
Total cost *($M)2,9205,4008,24027,00014,12054,000
Power delivered (MW)32162324
Revenue* ($M per year)1708521,704
*Numbers include all four satellites

Figure 3.8.2.2.-17. Satellite Comparison Based Upon Three Satellites

Figure 3.8.2.2-18 indicates a comparison of the solar and nuclear power options as a function of launch cost and price paid for delivered power.



Figure 3.8.2.2-18. Comparison of Type of Solar Power Satellites in 8-Hour Molyina Orbit

For solar-powered SPS, the high-probability demand markets do not show feasibility. The best answers in the nominal (medium) probability demand markets require transportation costs of less than $14/lb with current technology, and less than $20/lb with advanced technology. Even at the lowest probability demand market which offer the highest sized demand, such a system would require transportation costs of less than $46/lb to LEO. Doing such a venture as a purely commercial venture, with its higher interest costs and required rates of returns, appears unrealistic at any transportation cost. (This conclusion is driven primarily by the demand assumed and the high nonrecurring costs involved in this new technology).

For a nuclear-powered SPS, these costs get a little better. To maintain a 20% IRR after 20 years of operations, the transportation cost needs to be less than about $60/lb to LEO for the nominal demand case considered. If the highest demand model is considered (the lowest probability model), then these acceptable costs rise to about $123/lb. This venture also seems unrealistic as a purely commercial venture and would require the lower costs of money and the longer time horizons for a utility-type venture instead of a commercial venture. Again, the conclusions are driven primarily by the demand assumed, and the high nonrecurring costs involved.

3.8.2.2.2.3.4 Market Infrastructure
To serve this market requires that several elements in the supporting market infrastructure also be provided. These are summarized in Figure 3.8.2.2-19 Note that this is inherently a simpler infrastructure than the assumed GEO SPS examined above, with the exception of the nuclear support site at the launch site.


In-space transportation systemTransports payload (modular SPS elements) from LEO into final destination orbit.
Launch site support system (nuclear SPS option only)Receives and prepares nuclear power systems for launch.
Terrestrial receiving site (rectenna)Receives beamed power from satellite power system. Converts beamed power to output electrical power and transfers power into utility grid.

Figure 3.8.2.2-19. Infrastructure Elements for High Latitude Satellite Power Systems

3.8.2.2.2.4 Prospective Users
The prospective users for this system would be local communities and industrial operations in the high-latitude regions. These users cannot rely upon solar power due to the long periods of darkness during the Arctic winter. Transportation of fossil fuels into these regions is typically quite costly and, in some cases, available only a few months per year. The supporting infrastructure (installed power grid) is small, and expansion is costly due to the dispersed nature of these sites over large geographical areas.

Environmental concerns with the use of fossil fuels in the Arctic are increasing. The need to transport fuel as high-latitude power needs grow has increased concern over the possibility of inadvertent spills or contamination from transportation. (The Exxon Valdez incident was mentioned by several market contacts, and the possibility of collision with an iceberg or pack ice was also mentioned). Also, during the winter months, the atmosphere circulation patterns promote the local buildup of emissions from Arctic power systems, a condition that is is becoming a concern for environmental quality.

3.8.2.2.2.5 CSTS Needs and Attributes
3.8.2.2.2.5.1 Transportation Systems Characteristics
The primary CSTS attribute needed for this market area is to offer highly reliable and safe transportation at low cost.
Figure 3.8.2.2-20 indicates the traffic demand for launch in this large market in thousands of pounds per year to LEO. However, the launch demand does not occur until very low prices for space transportation are offered. And the launch of a nuclear power system, even if it launched "cold" as an inert payload, will place a premium upon safety and reliability in the launch system.
Medium-Probability MarketsLow-Probability Markets
Launch cost, $/lbTraffic, klb/yrPrice, ¢/kWhSPS size, MWe Traffic, klb/yrPrice, ¢/kWhSPS size, MWe
400------
100---25,85013.801,667
5015,59012.43100077,2009.10 5,000

Figure 3.8.2.2-20. Launch Traffic for Nuclear-Powered Satellite Power System 20% IRR Over 20-Year Operation (100 MW Ave Site)

3.8.2.2.2.5.2 Transportation System Capabilities
The sizing of the launch system can be adjusted to meet the market demand. Since the nuclear-powered SPS is assumed to be modular, the launch system can be tailored to launch one or two of the modules. Examination of the minimum sizing of these modules indicates that a launch capability of 50,000 lb equivalent to LEO is probably required to allow efficient packaging of these modules. Larger vehicles, in the range of 100,000 lb to LEO and up may be considered to launch two or more of the modules at a time.

Launch rates for these vehicles will be high and will be driven by the vehicle sizing. At the minimum, for a 1,000-MWe system, a 100,000-lb class launcher will require launching at the rate of about two per day to support this traffic demand. A 250,000-lb class launcher will require a launch rate of about one per day. Schedule reliability is not driven to be quite high, since there are a large number of recurring launches to the same destination orbits, but the large number of launches requires that few long delays are encountered in the launch cycles to avoid massive backlogs in the launch queues. Launches must occur within a specific launch window to efficiently insert the payloads into their desired destination orbits.

3.8.2.2.2.5.3 Ground Handling
Ground handling for these payloads will primarily involve the scale of integrating these modular power system onto the in-space transportation system, and then loading them into the vehicle. For the solar-powered SPS option considered, this should be similar to existing practices, although a much-simplified manner is required due to the large scale of operations.

For the nuclear-powered option considered, special ground handling and ground processing facilities may be required to support the nuclear reactors. It is assumed that the reactors are launched ñcold" or in a nonactivated inert state. This means that the system will not be radioactive in ground handling, and will not produce significant hazards until activated in its final destination orbit. However, special handling systems may be required to store, check out, and process these systems before launch.

3.8.2.2.2.5.4 User/Space Transportation System Interfaces
The primary interfaces to be considered are modular power system to in-space transportation system, and then the integration of this package onto the launch system. There will be no other users comanifested on the launch system because of the large size and number of payloads for this market area and the large number of essentially identical packages to be launched; therefore, these interfaces should be designed as common, and modular.

3.8.2.2.2.5.5 Improvements Over Current
Major improvements over current operations in launch cost, launch processing, and launch reliability are required.

3.8.2.2.2.6 Business Opportunities
The business opportunity for the CSTS is to provide the transportation demand to this large market. Of all the areas considered in the CSTS market analysis, this is one of the largest for overall transportation demand, but it also requires some of the lowest $/lb to orbit to provide a good business opportunity to potential users.

3.8.2.2.2.6.1 Cost and Price Sensitivities
The business analysis performed earlier is highly dependent upon the analytical market demand model and the business model cost and price assumptions used. A range of market demand and price sensitivities were examined, with results as reported previously. However, the nonrecurring investment cost before constructing and launching a space power system is also a major driver. Figure 3.8.2.2-21 indicates the sensitivity of the results of this assessment for typical power price points on the nominal demand model



Figure 3.8.2.2-21. Sensitivity of Analysis to Development (DDT&E) Costs

Another sensitivity of these results is to the allowable internal rate of return (IRR) used to judge a venture as a credible business investment. Based upon discussions within the power utility industry, an IRR of 20% after 20 years of operations was judged to be representative of a public utility-type investment, operating with lower costs of capital and a longer time horizon than purely commercial (deregulated) operations. For deregulated commercial operations, a venture operates under stricter limitations with higher capital costs and a shorter payback period. For such ventures, 20% IRR after 10 years of operations is representative.
Figure 3.8.2.2-22 indicates the sensitivities of the results of this analysis to IRR and time period, for a representative case using the nominal demand model. If shorter payback periods are required, either much higher revenues or substantially lower costs are needed.



Figure 3.8.2.2-22. IRR Sensitivity to Time Scale

3.8.2.2.2.7 Conclusions and Recommendations
At space transportation costs less than $100/lb into orbit, production of space power can be a significant demand driver, serving niche markets that are willing to pay a higher price per kWh. But to accomplish this, a public-utility-type operation must be considered to overcome the barriers presented by the competitive requirements of low prices and long paybacks.

3.8.2.2.3 Sun-Synchronous Power Satellites

3.8.2.2.3.1 Introduction
The major market for power is to the major metropolitan areas within the continental United States. Within this market, a premium is paid through existing systems for power provided during peak demand periods. This premium price is paid since generating systems are most efficient if run at constant level. During peaking power conditions, new assets or stored power must be brought on line and run solely for this peak power demand.

3.8.2.2.3.2 Study Approach
With the use of the data generated from the other market areas, a ROM assessment of the business feasibility of supplying peaking power from a set of Sun-synchronous satellites was developed. A return on investment using IRR of 20% in 20 years of operations was used to estimate the feasibility of such a venture.

3.8.2.2.3.3 Market Description
3.8.2.2.3.3.1 Description Market Evaluation
From orbital mechanics, it is possible to launch into near-polar orbits a satellite power system such that the same satellite is always over a terrestrial target at 6 a.m. and 6 p.m. to provide additional power into the grid. These ñSun-synchronous orbits" would allow a satellite power system to service terrestrial power grids at a repeatable time each day. If the constellation is placed into 4 hour orbits, it is possible to service 12 sites daily (2 per orbit - see
Fig. 3.8.2.2-23).



Figure 3.8.2.2-23. Ground Track for Peaking Power Satellite Power System in 4-Hour Synchronous Orbits

The unit costs for this system are projected at about $1,200/kWe, which is excellent for this type of system (
Fig. 3.8.2.2-24). But remember, the costs used in the spreadsheet analysis are purposely aggressive. Peaking power is more expensive than base power, averaging about 9¢ per kWh in the United States (although some utilities pay up to 15¢ for this power). Feeding these data data into a time-phased spreadsheet, at 12¢/kWh the ROM returns are marginal until launch costs drop well below $100/lb.


Apogee altitude, km12550Specific cost of Brayton PP, $/kW100
Perigee altitude, km300No. of 600 MWt reactors in 20 yrs478
Semimajor axis, km12,803600 MWt reactor TFU, $M$600
Orbital period, hrs4.00Reactor learning curve0.8
Delta V1, km/sec1.67Avg cost of nuclear reactor, $M$77
Delta V2, km/sec1.27Cost of power gen./satellite, $M$388
Upper stage isp, sec470Cost per satellite, $M$472
One-way mass ratio1.44Visibility per site, minutes45
Busbar Power, MW500No. of satellites reqd4
Transmission freq, GHz15Upper stage lambda prime0.85
Grid conversion efficiency0.9Upper stage prop mass, kg845,481
Rectenna efficiency0.9Total mass/satellite to LEO, kg2,616,471
Transmission efficiency0.96LEO delivery cost, $/kg220
Klystron/magnetron eff.0.85LEO deliv cost/ satellite, $M576
Power conditioning eff.0.95Total launch costs, $M2,302
Satellite power, MW796.29Total satellite purchase, $M 1,886
Spec. power of conv, kg/kW0.45Total number of sites12
Power generation mass, kg358,330Average power per site, MW500
Electric generator mass, kg318,516 Total rectenna purchase, $M244
DC-RF w/ substructure, kg1,074,195System cost installed, $M4,433
Power limited antenna fia, m226Incremental installation rate1
Antenna diameter, m443.74Busbar $/kWe739
Antenna structure, kg19,948O&M cost, ¢/kWh2
Antenna cost, $M84System DDT&E/2, $M0
Diameter of rectenna, km0.72Power price, ¢/kW-hr12
Peak power intensity, mw/cm2272.70 Revenue/ year, $B0.329
Rectenna cost, $M2020-year IRR<0 %

Figure 3.8.2.2-24. Design Characteristics of Peaking Power SPSs in 4-Hour Sun-Synchronous Orbits

3.8.2.2.3.3.2 Market Evaluation
These results were placed in a time-phased business model to analyze the cash flows and costs. From this analysis, it was impossible for this system to meet a commercially viable rate of return, even at the relaxed constraints assumed for the public utility industry. The primary driver for this appears to be the revenue stream; this is because the satellites spend most of their time over water where they cannot produce revenue, and the price paid for power when they are transmitting is insufficient to produce an economic level of return.

3.8.2.2.3.3.3 Market Assessment
Figure 3.8.2.2-24 also illustrates one of the best cases found. Here $0.12/kWh is paid for peaking power, 12 sites are serviced each day, and there are no development (nonrecurring) costs for this system. Even with these optimistic assumptions, the system does not provide an acceptable return, even at $100/lb.to-orbit costs.

3.8.2.2.3.3.4 Market Infrastructure
The market infrastructure for this system is similar to that of the Molniya orbit satellite power system. An in-space transportation system, a ground processing system (if nuclear power sources are used), and ground receiving stations are needed. Since there was not viable market in this area, no further analysis was performed.

3.8.2.2.3.4 Prospective Users
The primary users for this system would be the major metropolitan utilities. However, since no viable business opportunity could be identified, no further contacts were made.

3.8.2.2.3.5 CSTS Needs and Attributes
Sun-synchronous satellites for peaking power were assessed not to be a viable market for a future space transportation system, independent of transportation cost. Therefore, CSTS needs and attributes were not defined.

3.8.2.2.3.6 Business Opportunities
No business opportunities were identified in this area at this point.

3.8.2.2.3.7 Conclusions and Recommendations
The Sun-synchronous power satellite concept for peak power provisions does not appear to be a viable market opportunity for space transportation systems, regardless of price. The drivers for this conclusion are the low price for power provided and the fact that these satellites do not have a high duty cycle per orbit.

3.8.2.2.4 Lunar-Based Power Station

3.8.2.2.4.1 Introduction
After the major contractual studies of the GEO satellite power systems were performed in the late 1970s it was identified that much of the cost was for transporting equipment and components upwards in the Earth's gravitational well. Since that time several studies have generated an interest in producing solar power satellite components and system on the lunar surface or mining the Moon to provide construction material for SPSs. The specific venture examined here is to produce and install large solar power generation and transmission systems on the lunar surface and transmit power back to the Earth for terrestrial use.

3.8.2.2.4.2 Study Approach
The approach followed in this analysis was to examine past analyses, and wherever possible to contact past participants and principals in these studies. From this, the technical and market feasibility of such an appraoch was examined. The following steps were taken in assessing this market area:

  1. Literature search of the available literature on lunar power systems.
  2. Contacts with participants and leaders of past studies.
  3. Assessment of technical and financial feasibility, including development of analytical models of the lunar power option, and assessment of the market opportunity.
3.8.2.2.4.3 Market Description
3.8.2.2.4.3.1 Description Market Evaluation
Lunar power system requirements for a 1-, 10-, or 100-GW operation are shown in
Figure 3.8.2.2-25. These numbers assume a 10-year R&D period, a 3-year period for initial deployment of equipment, and then a 10-year period of emplacing power units on the Moon. These numbers are preliminary only, being scaled from the 1979 study by General Dynamics. These numbers also assume that no lunar base exists, that no Earth-to-Moon transportation system exists, and that the material required to establish them is brought from Earth. Once these pieces of infrastructure exist, the cost of adding capacity is small.

Even at these small capacities, the venture begins to make a profit somewhere between 10 and 100 GWe installed. The Moon and space tonnage figures can be evenly distributed over the 10-year R&D period. With current launch systems (such as the shuttle) a flight every other day would be required. Clearly, a heavy-lift launch vehicle is required and the cost of one is included in these numbers, even for these modest LPS.

A dramatic reduction, on the order of 90%, could be made in these mass figures if a concerted effort is made to utilize lunar resources to the maximum extent possible and additional R&D time is allotted. This reduction assessment is based on the reduction made possible in the General Dynamics SPS study by utilizing lunar materials. Launch vehicle cost was assumed to be approximately $550/kg.

This proposed venture is even more demanding technically and financially than the GEO SPS markets, and would require the development of a substantial lunar base, manufacturing, and operational facility before power could be transmitted. Furthermore, orbiting reflectors around the Earth would have to be developed and emplaced to allow power beaming to the other side of the Earth from the Moon. This would require hundreds of billions of dollars in investment before power could be returned, and although the economies of scale may promise power at low prices, the investment cost is too high to be considered on a commercial venture basis.

It is possible such a large venture could be pursued as part of a major government program and be used as the centerpiece of a major governmental space or lunar development program. But such decisions and investments will have to be made on other than commercial grounds, and this market was not judged as a viable commercial market.


Item/GWe (10yr)110100
GWe-yrs550500
Rev. (109$ @ 0.1$/kWe-h)4.38343.83438.3
Net revenue (109$)-55.7-46.8194.9
Total costs (109$)60.190.6243.4
R&D (109$)42.450.985.5
LPS Hrdw10.710.710.7
Cnstr. syst.1.12.910.9
Facilities and eq.5.110.029.9
Transportation25.527.434.7
Space and ops (109$)17.234.2102.5
Rectenna (109$)0.65.555.4
$/kWe-H1.370.210.06
Moon (tons)2284619421552
Space (tons)97426809677
People (Moon)2980283
People (space)1523

Figure 3.8.2.2-25. Lunar Power System Requirements as Function of Size

3.8.2.2.4.3.2 Market Evaluation
Limited evaluation was done upon this market. The primary drivers for this market are the very large upfront investment costs, ranging from a few tens of billions to hundreds of billions of dollars. The CSTS assessment indicates on a theoretical recurring cost basis, the very large economies of scale and ROM assessments of the costs of such a system show promise that power can be produced for terrestrial usage at competitive costs to terrestrial systems and that transportation costs into orbit, if reduced, can improve this performance.
Figure 3.8.2.2-26 indicates the results of a preliminary analysis on the recurring cost of producing power from a lunar-based power system.



Figure 3.8.2.2-26. Recurring Costs of Power From Lunar Power System

However, the problem is not that the economies of scale will not work, nor that such a system is technically infeasible, compared to other large in-space power systems, such as the GEO satellite power system. Rather ,the difficulty, again, is in the large upfront investment.

The purpose of the CSTS is to identify markets of sufficient size for future space transportation systems. These markets are quite large, but the large upfront investments and long payback times involved remove them from commercial investment levels. Such markets will have to be developed from governmental coffers, and in some cases (e.g., a large lunar surface power system) will probably require multiple governments to invest in them.

As such, the CSTS assessment is that such markets are not driven by external market forces, and the price of transportation is not a primary contributor to these markets.

3.8.2.2.4.3.3 Market Infrastructure
Since this market area is not viewed as commercially viable (independent of transportation costs), no infrastructure assessment was performed. Besides transportation to orbit, several infrastructure elements need to be put into place before commercially large amounts of power are available from the lunar surface. They include-

  1. In-space transportation system, to transport people and cargo to and from the lunar surface. This system must also provide the means of deploying and maintaining other in-space assets for this venture.
  2. Lunar surface base, including habitat and manufacturing facilities. This base must manufacture and install the power system elements and components, and service them once they are installed.
  3. Lunar power system, to transmit the power to the Earth for use.
  4. Earth-orbiting reflectors. Since the Moon is not visible over half the Earth, providing power to users on the far side of the Earth will require orbiting reflectors that are deployed to reflect the beamed power from the lunar power system to terrestrial users.
  5. Terrestrial ground receivers, to receive the transmitted power from the lunar surface, convert it into electrical power, and transfer this power into the utility grid.
3.8.2.2.4.4 Prospective Users
As with other space power systems, the primary prospective users for this system are the major utilities.

3.8.2.2.4.5 CSTS Needs and Attributes
The market analysis for lunar power systems indicates that this market is not primarily driven by orbital transportation costs. Therefore, CSTS needs and attributes were not defined.

3.8.2.2.4.6 Business Opportunity
No viable space transportation business opportunities in this market segment were defined at this point.

3.8.2.2.4.7 Conclusions and Recommendations
The lunar power system market area was defocused at this time, due to an assessed lack of market sensitivity to space transportation cost and due to the large investment sums required.

3.8.2.2.5 Space-to-Space Power Beaming

3.8.2.2.5.1 Introduction
Space-to-space power beaming for the purpose of providing power to orbiting satellites is another possible market area of interest. Several persons contacted during the CSTS market assessment identified this area as a potential near-term application of in-space beaming and as a potential market area.

The main attraction or advantage to space-to-space power beaming is to be able to simplify satellites by off-loading the power-generation system and thereby also extending the life of the satellite indefinitely. Options for doing this include microwave or laser power transmission options.

The primary concept for such a venture is to place a central "power station" in orbit equipped with large power-generating systems (usually solar arrays). From this centralized power station beamed power is transmitted to other orbital assets to provide them power. The advantages of this are claimed to be lighter, cheaper co-orbiting satellites and lower cost overall to the system architecture.

3.8.2.2.5.2 Study Approach
The approach used in this analysis was to examine the current literature for existing data on such systems, contact participants and potential users, and develop an independent analysis of the business feasibility of this market area. If this business and technical feasibility analysis showed promise, then an assessment was to be performed of the impact on future space transportation systems demand and the impact of reduced cost to orbit.

3.8.2.2.5.3 Market Description
3.8.2.2.5.3.1 Description Market Evaluation
The market evaluation for this activity focused on major power users in orbit and on the technical feasibility of implementing such an approach.

3.8.2.2.5.3.2 Market Evaluation
The market for in-space power beaming is concentrated upon regions where large users of in-space power systems and of concentrated orbital assets are available. These two areas are in the vicinity of the space station (and associated facilities) and in GEO.

In the vicinity of the space station there will be an installed market of about 100 kW of power, which is currently baselined to be provided from solar dynamic and photovoltaic arrays. In GEO, a typical current technology communications satellite represents 4 to 6 kW of power. These satellites are being replaced at about 20 to 25 systems per year, and even if all future satellites were to use the in-space power beaming capability, the market would be limited to growth of about 80 to 150 kW per year, spread over the geosynchronous orbital arc at 35,800 km of altitude.

3.8.2.2.5.3.3 Market Assessment
Power beaming was examined as a possible means of simplifying the space station by using co-orbiting satellite modules. Both laser and microwave transmission of power from a central power satellite to Station modules was examined. Laser transmission was found to be too inefficient compared to microwave transmission, primarily driven by the lower efficiencies in turning incident sunlight into laser light and then back into electrical power to be used. However, even with microwave transmission, power beaming was found to be less efficient in terms of mass required and cost compared to housing the modules directly on the SSF. Figure 3.8.2.2-27 represents the results of a preliminary assessment of this market.



Figure 3.8.2.2-27. Comparison of Laser and Microwave Power Transmission for Space Station Power

For GEO satellites, this problem becomes worse. Satellites located at a typical spacing in GEO, 2 degrees apart, are about 1600 km apart. Over these distances, the efficiency of transmissions drops off, unless very large antennas are placed on the transmitting and receiving satellites. At this point, the mass efficiency of using beamed power to save mass (and transportation cost) versus using solar arrays and batteries becomes questionable.

While some simplification of satellite power system subsystems may be possible using beamed power, indefinite life extension (as suggested by some persons during this market survey) is questionable due to technology obsolescence, and limited life items in other subsystems. Current space systems are typically designed so that the system is not life-limited by a single subsystem. Removing the power system would merely shift end-of-life failure to some other system, assuming the power system is currently the life-limiting system. Furthermore, indefinite life extension does not seem desirable due to improvements made possible from evolving technology. As for simplification, the power system could be only partially eliminated since batteries would still be required to provide power during launch and installation, during periods of eclipse, or in the contingency event of noncontact with the power source. Having large numbers of co-orbiting assets rely solely upon a single centralized power system would provide a large single-point failure for the entire system if power were interrupted for some reason.

Furthermore, if space transportation costs are reduced dramatically, satellite power systems and their installed value should become cheaper. This will reduce the market advantage, if any, for space-to-space beamed power even further.

3.8.2.2.5.3.4 Market Infrastructure
The required market infrastructure for such a venture would require the switching of significant assets to a centralized in-space power system. Individual satellites would have to be equipped with the power receivers, and the centralized power generation and transmission system would have to be launched.

Before such a large change in current system operating practices is realized, this technology must be demonstrated and its reliability and usefulness demonstrated.

3.8.2.2.5.4 Prospective Users
Prospective users for this system would be primarily concentrated in assets that are relatively close. The two areas identified as meeting this criterion are in the vicinity of the space station and in GEO.

3.8.2.2.5.5 Business Opportunities
No significant business opportunities for low-cost space transportation were identified in this area.

3.8.2.2.5.6 Conclusions and Recommendations
The space-to-space power beaming market area has been defocused at this time because it was assessed not to be a driver for low-cost space transportation markets.

3.8.2.3 Prospective Users Contacted

  1. Peter Glaser, Sunsat energy council.
  2. Dave Criswell, Lunar Power Coalition.
  3. Bob Waldron, Lunar Power Coalition.
  4. Dieter Franz, Southern California Edison, Senior Planning Engineer.
  5. John D. Edwards, Mission Energy Company, Project Director, International Business Development.
  6. John T. Kostanecki, Mission Energy Company, Project Analyst, Business Development.
  7. EPRI.
  8. Jack Stone, National Renewable Energy Laboratories (NREL).
  9. Jack Cashin, Edison Electric Institute.
  10. Alaskan Power Authority.
  11. Gary D. Bunch and Sid Greutz, DOE.

3.8.2.4 Overall CSTS Needs and Attributes

Overall, the only market areas within the space utilities market area that show promise do so when transportation costs are less than about $100/lb, arising from the satellite power system in Molniya orbit, serving remote high-latitude sites. Technically, this is a very demanding requirement to reduce operating costs to this point. There is no requirement for down-weight or return payloads, nor is there a primary requirement for passenger operations for this market area. However, if a nuclear power option is considered for the high-latitude SPS, then either highly reliable launch, or intact abort, capabilities are required in the launch system-to allow safe operation with these nuclear capabilities (although it is assumed that for safety's sake, any reactor is launched cold, in a safe, nonpowered state).

Once the system is in place, some amount of periodic maintenance can be expected. Since the revenue-generating capabilities of the system are crucial, these maintenance activities (both scheduled and unscheduled) must be capable of being launched on time, or very quickly on demand.

In aggregate, the CSTS needs and attributes from this market area are as follows.

3.8.2.4.1 Transportation Systems Characteristics

Highly reliable and safe transportation, is necessary, at very low cost. As stated previously, this market assessment primarily considered launch of payloads in the 55 to 100 Klb (LEO equivalent) range. Larger payloads can be considered and may be desirable to reduce the required launch rate.

3.8.2.4.2 Transportation System Capabilities

The transportation system must accommodate mass of 55,000 lb or more per single launch and high launch rates, with potential for over 750 launches per year with 100,000-lb payload launch vehicles. It should be noted that since these SPS systems are in specific constellations and planes, the launch windows will be limited for launch. Schedule reliability is driven by need to avoid massive backlogs in launch queues.

3.8.2.4.3 Ground Handling

Ground handling will require integration of modular power systems onto in-space transportation system, and then loading them into the vehicle. It will require much-simplified processes compared to current practices due to the large scale of operations. Specific ground handling requirements for these systems will be minimal. SPS payloads can be processed through standard launch operations facilities, except for a nuclear-power option, which may require special ground handling for the cold nuclear reactors. The primary driver for these launch systems for ground handling is that they may drive sizing and facility number requirements to handling the increased traffic even from the small SPS considered here.

3.8.2.4.4 User/Space Transportation System Interfaces

The SPS user interface between their system and the space transportation system is expected to be standard, and fairly minimal. Since it is assumed these payloads are modular, and there are very few differences between payloads, standard interfaces and launch processing operations can be used. However, it is important to note that the SPS system requires use of an orbital transfer system and that this system must also be integrated with the SPS payload and the launch vehicle.

3.8.2.4.5 Improvements Over Current

Major improvements over current operations in launch cost, launch processing, and launch reliability are required.

3.8.2.5 Market Assessment/Business Assessment

Short of waiting until the world runs out of fossil fuels and nuclear power is legislated into oblivion, there appear to be only two ways to force space power into the energy equation. The first, and better, is to offer energy cheaper and in a more convenient form than the competition. From our market assessment, this appears to be possible only at remote sites, where ground-based solar power is not a viable option, for example, in the Arctic or Antarctic regions. Since the market demand is much greater in the Arctic regions, this is the preferred option.

The second path is driven by politics and the current concern about environmental pollution. Costs of fossil fuels are increasing, not from supply/demand pressure, but from regulation and legislation that seeks to tax fossil fuels to limit their output of greenhouse gases, and toxic wastes, and to recover costs to clean up the environment. For example, recent attempts to add a "carbon tax" for carbon dioxide production and a "BTU tax" for energy usage are examples of these types of regulation. While this is a potential outcome in the future, its impact will primarily be seen in the developed countries.

Of the options considered, the most promising option is the high-latitude SPS with orbits in highly-eccentric Molniya orbits. Even at the low costs, this market yields a substantial revenue stream for space transportation. Figure 3.8.2.5-1 indicates the time-phasing of this launch revenue at the nominal model demand case ($50/lb).



Figure 3.8.2.5-1. Revenue Projection for Nominal Demand Case (Transportation Price $50/lb)

At transportation costs greater than $ 50/lb little if any transportation demand exists from these market areas in the nominal, or medium, market probability level.

The schedule at which the demand occurs is speculative. This demand is highly dependent upon the provision of low-cost, reliable demand. As such, it will not occur until the transportation system development is well along. Because of the large upfront costs associated with most space power systems national and international support is required to establish the framework to support the venture. Much of the upfront development costs can be reduced through government development of space transfer systems and associated technologies. For example, the space transfer system developed for space disposal of nuclear waste can be used for emplacement of solar power satellites as well. Similarly, key technologies in the satellite technology can be demonstrated by government programs.

Another key enabler in this market area is the development of common international and national consortiums or investors to finance these investments. The size of the investments and the long time period needed for economic payback remove these ventures from most commercial investment options. This will require either government market guarantees or direct funding to make the ventures succeed.

No price/demand elasticity curve is shown for this market, since the primary driver is to obtain a threshold cost, where this venture is economically justified. If the cost is above $50/lb, as shown in section 3.8.2.3.2 , an acceptable rate of return is not obtained, and it is assumed that the market does not exist.

A viable SPS market was not assumed in any high-probability case, at any $/lb of transportation, since the market's development would require substantial infrastructure development and challenging financial conditions in the industry. However, the medium-probability model included a single high-latitude SPS system at $50/lb for our nominal case.

3.8.2.6 Conclusions and Recommendations

Much to the surprise of some of the members of the CSTS team, solar power satellites were shown not to be a viable market area, unless at very low launch cost. The best market potential identified was for niche markets, which have high revenue potential, and key competitive technologies (like ground-based solar energy) were excluded.

The nominal/medium probability market projection includes such an SPS system, serving the niche market of distributed high-latitude power users.

Additional study in this market area is recommended to further assess the design of SOS systems for this market area and to firm up the design of the support infrastructure (orbital transfer systems).

References

  1. "Annual Energy Outlook," Energy Information Administration, 1993.
  2. EPRI Journal, page 23, June 1991.
  3. "Energy Prices and Taxes," International Energy Agency, Organization for Economic Co-operation and Development, 2 rue Andre-Pascal, 75775 Paris, CEDEX 16, France, 1993.
  4. "Solar Power Satellite System Definition Study," Technical and Management Proposal, Boeing D180-24617-1, May 1, 1978.
  5. Anon., misc. Boeing SPS references.
  6. J. A. Angelo, Jr., D. Buden, "Space Nuclear Power," Orbit Book Company, Malabar, Florida, 1985.
  7. D. J. Bents, "More Than You Ever Wanted To Know About Nuclear Space Power Systems," NASA LeRC.
  8. Jon McGowan, "America Reaps the Wind Harvest," New Scientist, pp. 30-33, August 21, 1993.
  9. Potter, S. D., and Kadiramangalam, M. N., "Frequency Selection Issues for Microwave Power Transmission from Solar Power Satellites," Volume 10, Nos. 3 and 4, Space Power, 1991.
  10. Healy, T., McClure, W., Miller, D., ñSpace Station Configuration Studies, Option III Family Alternative Concepts," Rockwell International IR&D Study, 1 April 1993.
  11. Hein, R. ñProgrammatic Consideration for Geosynchronous Earth Orbiting Satellite Power System," Rockwell International, 385-200A-94-008, 25 Feb 1994.
  12. PowerSat Study-Economic Assessment of PowerSat Operational Concepts," ESA contract 9390/91/F, 1992.
  13. Hangley, G. M., "Satellite Power Systems (SPS) Concept Definition Study," Rockwell International, contract NAS8 32435, October 1980.
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3.8 Space Utilities
References
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