Activities on the Moon
Preliminary efforts on the surface of the Moon are minimal because the lunar systems can be evaluated and tested near Earth. Moreover, only limited lunar exploration is required (though more may be desirable) since undifferentiated lunar soil supplies the colony with sufficient minerals.
MATERIALS AND SUPPLIES
Materials for the total colony could come from the Earth. However, by using lunar raw materials as soon as possible, the costs to Earth of constructing the colony are greatly reduced, though the time required for completion of the colony is increased. Such a strategy is implemented by constructing only the essential components of the colony system from Earth materials. These subsystems — the lunar mining facility, the ore mass transport system, the L5 materials extraction and fabrication facility, and the construction shack — are then taken to their respective positions in the system. Here they are made operational to process lunar raw materials for the major construction of the habitat. During this construction phase minor construction materials and supplies, as well as crew resupply, must come from Earth.
Fabrication on Earth
Low Earth orbit (LEO) serves as a vital point in the construction and supply of the first space colony. There, a space station consisting of a crew quarters, a construction shack, and a supply depot is assembled from materials made on Earth. Additional materials are then launched from Earth to LEO for assembly of the lunar base. They include a nuclear power station, a mass launcher and auxiliary equipment, mining equipment, crew quarters, and maintenance equipment. Also launched is equipment for L2, the mass catchers and the interlibration transfer vehicle (ILTV). The construction shack, the solar power station and the supplies and facilities used in materials extraction and fabrication are launched to LEO for transfer to L5.
Raw Materials from the Moon
Lunar mining operations proceed as described in chapter 5. Oxygen is an important by-product of the refining of lunar materials at L5. It can be used there as rocket propellant immediately (resulting in a significant reduction in costs of transportation) or can be stored for later use in the atmosphere of the space colony and in its water.
Full use of all of the mass obtained from the Moon is assured by the manufacture of metals, glass, and soil, and by the use of ore and the slag in the cosmic ray shield.
Raw Materials from the Earth
The completed habitat must be outfitted with supplies and raw materials which are available only from the Earth, including highly specialized equipment and personal belongings of the immigrants to the colony. The atmosphere, water, and chemical systems also require raw materials from Earth; mostly hydrogen, carbon, and nitrogen which are not present in lunar ore. The initial agricultural biomass must be transported from the Earth to complete the outfitting of the habitat. From the time when immigration of colonists begins, only the resupply and new materials not available from the Moon are required from the Earth.
TRANSPORTATION AND CONSTRUCTION
Initially all of the supplied materials must be sent from Earth to LEO for transshipment to the point of activity. As operations begin at L5 raw materials must be sent there from the surface of the Moon so that metals can be extracted and the construction of the colony can start.
Transshipment and Assembly in LEO
After the effort of research, development, demonstration, testing and evaluation there is a LEO station with pilot plants for processing materials and for producing nuclear and solar power. Because of the volume and weight limitations of HLLV payload capacity, large items are launched in subunits to be assembled in space. The payload capacity of the IOTV nominally equals that of two HLLV's, but in space neither volumes nor acceleration forces limit the configuration. Assembly tasks at LEO range from repackaging the mass launcher to setting up the complete solar power stations.
A propellant depot must also be established at LEO for use by the IOTV. When this additional propellant is taken into consideration, the mass which must be brought from Earth to LEO is roughly 4 times the payload delivered to L5, and 8 times the payload delivered to L2 or to the lunar surface. However, with the eventual availability of oxygen for rocket propellant as a by-product of refining at L5, the mass which must be brought to LEO becomes approximately twice the payload to L5 and 3.3 times the payload to L2 or to the lunar surface (Austin, G., Marshall Space Flight Center, Alabama, personal communication, Aug. 15, 1975). These factors include return of transportation hardware to its point of origin following each mission.
Lunar Operations
Portions of the lunar base and the propellants for the lunar landing vehicle (LLV) are carried by the IOTV to a lunar parking orbit from which the LLV's ferry material to the lunar surface. As shipments arrive there, an assembly crew successively assembles the power plant, an underground habitat, the lunar soil scoop, and the mass launcher. Two separate nuclear power systems and 2 mass launchers are used to achieve the reliability needed. Their construction is timed to provide substantial operational experience with the first system before a second system is completed. The lunar base also includes a repair shop and a supply of spare parts for timely preventive maintenance and repairs.
Build-up at L5
The construction shack and the first power plant are delivered to L5 by the IOTV and are assembled by the construction crew. Thereafter, the materials extraction system and the fabrication system are constructed and made operational. Any lunar material received before the processing facility is completed is simply stockpiled.
ESTIMATING COSTS AND TIME
The subsystems, materials, supplies, and operations required for the build-up of the colony system have been outlined in the previous sections. It now remains to schedule the sequencing and timing of the events, and to determine the costs involved with this build-up. The scheduling and costing activities are interdependent.
System Considerations and Constraints
The scheduling and costing presented here are for the establishment of the baseline colony system described in chapter 5 through the completion and population of one habitat.
To allow ample lead time consistent with other large scale projects, the colony's development is scheduled with a gradual build-up of effort and with minimal fluctuations from year to year. Alternative strategies by which costs or project duration may be minimized are outlined briefly in appendix A. In general these results indicate that short durations are accompanied by large system costs. If interest costs are included, there is some minimum cost strategy. However, no optimization is attempted on the schedule presented here.
Automation is included only to the extent that it is now practiced in the industries involved. Bootstrapping (the use of small systems to build larger systems which, in turn, are used to build still larger systems) is not used in the cost estimate for the colony development, with the exception that pilot plants serve mainly to gain design and operational experience. The factors of additional time and added complexity of increased construction in space both caused the rejection of extensive bootstrapping.
Methods Used for Estimation
The scheduling and costing of a space colony require estimation of labor, size, and cost. First, labor: the personnel required in space for each major step of colonization is estimated from a composite of similar elementary tasks performed on Earth but derated or increased by the effects of vacuum and weightlessness. The methodology for estimating labor requirements is described in appendix D of chapter 5; the major results are summarized in table 6-1.
Next, sizes: the main items to be sized include habitats, vehicle fleets, and resupply and mass flow rates. The L5 construction station and the LEO station are nominally 5 t/person with 7 t/person for the more permanent Moon base. The number of vehicles is twice that required for minimum turnaround time. Annual supply rates during construction are set at 1.7 t/person, which includes food, water, gases, and expendables. After the colony is available for habitation, the annual supply rate is reduced over the 4-yr colony build-up to an estimated 0.1 t/person.
The mass flow rate from the Moon is sized to complete the shield in 10 yr (1.2 X 10⁶ t/yr). The materials extraction and fabrication plants are sized by the completion of the colony's shell in 6 yr (9 X 10⁴ t/yr). Plant output is assumed (on the basis of an average of terrestrial industries) to be approximately 8.3 plant masses per year. Each power source is sized proportional to its respective power user.
These estimates for the transportation system, the mass and energy systems, and for the habitats are shown in tables 6-2, 6-3, and 6-4, respectively.
Finally, cost estimates are required for three categories of expenses — research and development through the first unit, purchase price of additional units, and transportation costs. A precise costing effort for the first two items is prohibitively complicated. However, previous space projects have shown that research and development costs vary from $1000 to $20,000 per kg; Apollo was $14,000/kg. In this study $5000/kg is used. Purchase prices are assumed to be $500/kg which is consistent with other large-scale systems. Transportation costs, primarily launch and propellant costs and exclusive of vehicle costs, are based upon a manned payload of 30 people in each shuttle and an unmanned payload of 150 t per HLLV leading to $4.4 X 10⁵ per person and $2 X 10⁵ per tonne delivered to LEO. Outward beyond LEO, costs depend upon destination. They decrease with increased availability of oxygen in space from processing of lunar material.
These data are summarized in tables 6-2, 6-3, and 6-4 along with the size data. All costs are expressed on 1975 dollars.
TABLE 6-1 — PERSONNEL REQUIREMENTS
| Location | Time (yr)** | Personnel | Resupply (t/yr) | | :--- | :--- | :--- | :--- | | LEO | 5-14 | 100 | 170* | | Moon | 10-14 | 300 | 510* | | Moon | 15-22 | 150 | 255* | | L5 | 10-14 | 300 | 510* | | L5 | 15-22 | 4400 | 7480* | | Colony | 20-23 | 10,000 | 1000†† |
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- Nominal resupply: 1.7 t/person-yr of normal Earth materials costing $5/kg.
- ** Times are years from start of the project; e.g., if the project began in 1990 the time period 5-14 means 1995 to 2004.
- † Colony resupply: Linear decrease from nominal value during 4-yr period of colony immigration.
- †† Colony resupply: 100 kg/person/yr of imports.
TABLE 6-2 — TRANSPORTATION SYSTEM
| Vehicle | Mass (t) | R&D Cost ($B)* | Purchase ($B)† | Payload (t) | Destination** | Propellant/Payload*** | | :--- | :--- | :--- | :--- | :--- | :--- | :--- | | Shuttle | 150 | 10.0 | 0.5 | 30 people | LEO | — | | HLLV | 150 | 5.0 | 0.5 | 150 | LEO | — | | IOTV | 150 | 1.0 | 0.1 | 300 | L5 | 1.0 | | IOTV | 150 | — | — | 300 | LPO | 2.0 | | LLV | 150 | 1.0 | 0.1 | 150 | Moon | 1.0 | | ILTV | 100 | 0.5 | 0.1 | 100 | L2 | 2.0 |
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- Research and development through first unit at $5000/kg.
- ** LEO: Low Earth orbit; LPO: Lunar parking orbit.
- *** Austin, G., Marshall Spaceflight Center, Ala., personal communication, Aug. 15, 1975.
- † Earth to LEO for people via space shuttle, 30 people/flight (Hamaker, J., Marshall Space Flight Center, Ala., personal communication, Aug. 8, 1975).
- †† Crew transport module + people ≅ 2/3 t/person (Hamaker, J., Marshall Spaceflight Center, Ala., personal communication, Aug. 8, 1975).
- All costs expressed in 1975 dollars.
TABLE 6-3 — MASS AND ENERGY SYSTEMS — SIZE AND COST
| System | Mass (t) | R&D Cost ($B)* | Purchase ($B)† | Power (MW) | | :--- | :--- | :--- | :--- | :--- | | Solar Power | 14/MW | 1.0 | 0.5 | 200 | | Nuclear Power** | 45/MW | 1.0 | 0.5 | 220 | | Extraction | 7500 | 1.0 | 0.5 | 200 | | Fabrication | 3300 | 1.0 | 0.5 | 20 | | Mass Launcher | 300 | 1.0 | 0.5 | 180 | | Mass Catcher | 220 | 1.0 | 0.5 | — |
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- Research and development through first unit at $5000/kg.
- ** NASA estimates for near term technology (nuclear plants are unshielded).
- † Purchase at $500/kg.
- †† Active portions costed at $5000/kg for R&D TFU.
- All costs in 1975 dollars.