Figure 6-4 shows the growth of the number of people and colonies in space if the only aim is to produce electricity for Earth. Other additional scientific or industrial activities in space would require larger populations.
Figure 6-5 shows production costs for SSPS's and colonies, and the benefits from electricity generated to terrestrial-based Americans. The economic advantage of space operations would be improved if benefits to foreign nationals from lower electricity costs, and to colonists, are included in the analysis.
An international organization to fund the colonization program would bring even greater benefits to terrestrial Americans as discussed later. But even an American funded program would produce sufficient benefits, based on revenue obtained from sale of electricity and lower price of the electricity to the consumer. The costs for electricity (ref. 3) are discussed in appendix E. A competitive cost for space-derived electricity is 14.1 mils based on the assumption that the most economically-produced terrestrial electricity (from nuclear plants) will be 14.1 mils during the period under consideration. It is assumed that electric power consumption will not increase with price decreases and that all nations will be charged the same price.
Cash Flow and Other Results
A summary of cash flow — defined as the benefits less the costs for each year of operation in space — is given in figure 6-6. After year 12, costs are found to be dominated by building of SSPS's when mass starts to be transported from the Moon. The following 3 yr would be spent expanding the initial construction shack at L5 and building an SSPS to be used to beam energy to the Moon.
By year 22 a new shuttle system is to be operating and commercial production of SSPS's begun. Colonists would start to arrive in year 20 and number 10,000, 3 years later. Costs then would be subsequently proportional to the number of SSPS's produced each year, and benefits proportional to the total number built, increasing more rapidly than costs.
Through completion of the first colony the program would cost $196.9 billion, excluding costs directly related to SSPS's and more colonies (columns 1 and 5 of table 6-9). An additional $14.7 billion would be needed to prepare for production of the demonstration SSPS's (columns 3 and 4 of table 6-9) which would cost $21.7 billion more than the value of the electricity they produce.
By year 28 annual benefits would exceed costs. Payback in costs would be achieved.
Busbar cost of electricity produced from energy gathered from space is calculated to be 8.5 mils at year 22 falling to 4.8 mils by year 70 as shown in figure 6-6 (see also appendix D). The analysis is quite sensitive to the real discount rate (including inflation) which at 10 percent gives a benefit-to-cost ratio of 1.02. If the discount rate is lowered to 8 percent, the benefit-to-cost ratio is 1.5 (see appendix G).
Figure 6-6 — Cash flow (Benefits - Costs).
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Still Other Alternatives
The date at which a second-generation shuttle system becomes available is important. If development started at year 3 instead of year 15, the benefit-to-cost ratio could be increased to 1.3 and the cost of the program for the initial colony would drop to $112.7 billion, but with greater annual expenditures in the early years of the program.
There are alternatives to space colonization for generating electricity from space — building the SSPS's on Earth, and using construction shacks only without building any space colony. But space colonies win over terrestrial building because they use lunar materials which cost hundreds of times less at the use point in space than do terrestrial materials. While construction shacks cost less and can be built more quickly, in the long run they are more expensive because of their operating costs.
Some Other Energy-Related Benefits
While electricity from space and lower costs of electricity to U.S. consumers may be extremely desirable and sufficient to justify a space colonization program, there are other benefits that have not been fully evaluated in the study but may be significant. Environmentally, microwave transmission of power from space for conversion into electricity at Earth, is a very clean form of energy production (see appendix H). It avoids emission of pollutants into the Earth's atmosphere and minimizes the waste heat introduced into the terrestrial environment. The conversion of microwave energy to electricity is far more efficient than any thermodynamic process — 85 percent compared with a maximum of 50 percent.
Electrical energy from space may also be the only way in which the nation can become energy independent within the same time scale of 70 years, for not only can it supply the needed quantities of electrical energy but also inexpensive electrical energy that might be used for electrolysis of water to produce transportable fuels and thereby reduce dependence on petroleum products in transportation systems.
Another subtle energy-related benefit is the widespread nature of its application to mankind. Low-income people spend a comparatively greater percentage of their income on electricity than do affluent people. Thus lower priced electricity would benefit an enormous number of people and not just a few. This benefit from space colonization offers the potential of reaching vast numbers of people in the U.S. and providing relatively low-cost energy to many more in the developing nations of the world. It offers a real alternative to limited growth scenarios for underdeveloped peoples.
TABLE 6-10 — PARAMETERS OF THE COST EQUATION
| Parameter | Value | | :--- | :--- | | C_R | $28.5 X 10⁹ | | C_P | $14.6 X 10⁹ | | C_L | $200,000/t | | C_M | $400,000/t | | M_L | 32,000 t | | M_M | 12,000 t | | C_W | $120,000/man-yr | | N_L | 4400 | | N_M | 300 | | Y | 14 yr |
Note — Y is not the duration of the project, but 8 yr less.
APPENDIX A: SPACE COLONIZATION COST PARAMETRICS
The simple, analytic expression used for estimating the costs of space colonization versus time is particularly useful as an aid in observing the effects upon costs due to variations in the system parameters. Moreover, it is formulated on a rate basis so that the results can be scaled as the technologies or strategies of colonization change. However, the equation cannot be used indiscriminately without regard to several precautions. The equation only models the system costs, giving approximate results. When the cost equation is placed on a rate basis it is assumed that the system costs scale linearly. To simplify the equation, a number of terms which were thought to be negligible or too difficult to formulate were omitted, hence the results are too low. The 20 percent overhead charges were explicitly omitted. Finally, it is not easy to include parameters which change from year to year during the colony build up. In spite of these shortcomings, this equation is quite useful as a means of sensing cost trends which accompany changes in system parameters.
The major cost factors include research and development (R&D), production, transportation, and crew costs for the L5 and lunar facilities. The other costs in the system have been neglected. An analysis of the R&D and production costs shows them to be relatively independent of modest variations in size. Data from table 6-9 show these costs to be $28.5 X 10⁹ and $14.6 X 10⁹, respectively, for a total of $43.1 X 10⁹. Transportation costs to L5 and the Moon are expressed as and
where all parameters of the system are defined and evaluated for the baseline system in table 6-10. Similarly, the crew costs are given as and
When these results are added together, the total cost in 1975 dollars is obtained as
When the baseline values of the parameters from table 6-10 are substituted into eq. (5), the result is
These results are shown in figure 6-7. To demonstrate the use of the cost equation, two additional examples are also shown in the figure. In the first, a more advanced transportation system is considered which has $9 X 10⁹ additional development costs, but which reduces the launch costs per kg to L5 and the Moon to $200 and $400, respectively. The cost equation for this case is
Figure 6-7 — Parametric variations of system costs.
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In the second, a solar power source, instead of the nuclear source, is used on the Moon with a resulting cost equation of
Note that in the second case, this change is merely a convenient one for showing the use of eq. (5) and does not consider any of the related technical problems.
Specific ideas to optimize the system include:
- Major transportation vehicles to the Moon should not be returned until oxygen is available to reduce costs.
- The interorbital transfer vehicle (IOTV) could be powered by a solar electric power source and ion or mass driver thrusters.
- The lunar soil could be pre-processed on the Moon by magnetic separation.
- Major structural elements and shell may be built by vapor deposition.
- The colony site may be optimized by shortening either the lines of supply or the lines to ultimate usage site (geosynchronous orbit).
- Better transportation vehicles to LEO would be very advantageous. A single stage to orbit, completely reusable, vehicle is desirable.
- All wastes from the L5 construction crews could be stored for recycling to offset losses of colony gases, carbon and water.
- The torus can be shielded in stages by separate segments of complete thickness shielding for some groups of colonists to move in before the whole torus is shielded.
- The throughput of the lunar mass drivers can be increased by providing additional power from a lunar satellite solar power station (probably at L1, and using a shorter microwave wavelength from that used by the geosynchronous version).
- The labor intensive industrial operations as presently employed on Earth can be more fully automated to reduce costs of the large labor force at L5.
- The usual administrative functions can be provided by people remaining on Earth.
- Construction of agricultural facilities at LEO for providing food and for testing.
APPENDIX B: LUNAR SSPS POWER
Geosynchronous orbit is 35,400 km above the Earth, while L1 (the location of SSPSs used for lunar power) is 64,400 km above the near side of the Moon. Thus, if lunar SSPSs are identical to terrestrial SSPSs, the microwave beam covers about twice as much area on the surface of the Moon as compared to Earth. Changing the wavelength can reduce beam spread but results in a loss in the (dc-to-dc) efficiency of the system. Terrestrial SSPSs are assumed to transmit at a 10 cm wavelength with 67 percent efficiency. Using information provided by Glaser et al. (ref. 4), the relationship between microwave efficiency and beamwidth leads to a lunar system with a wavelength of 3 cm, a 30 percent efficiency, and using a rectenna area of 27 km².
For the lunar system the rectenna is made up of 3,000 dipoles/m² and weighs 5 kg/m². All is produced on the Moon except gallium arsenide for the diodes and possibly some dielectric materials and glues which need to be brought up from Earth, amounting to about 0.6 kg/m².
APPENDIX C: THE FLYBACK F-1
The Flyback F-1 (fig. 6-8) is a winged, recoverable derivative of the Saturn V first stage. It was studied extensively in 1971 and Boeing proposed it for use as the first stage of the shuttle. Its development was estimated to cost $5 billion and to require a 7-yr lead time. It would replace the solid motors as the first stage of the HLLV. The propellants are mainly kerosene and oxygen. While the environmental consequences of kerosene are not as good as those of hydrogen, they are much better than those of solid propellant rocket motors. More research is needed to determine if this system could be made environmentally sound for the 70-yr program of space colonization.