Circumferential lunar utilities

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7.1 INTRODUCTION

The global settlement of the Moon will require electric power and communications as well as transportation networks (the lunar utility infrastructure), on and below the lunar surface. Without these elements in place, the exploration of the Moon and other large-scale tasks would be difficult. When in-situ resource utilization capabilities begin producing infrastructure components, such as solar cells, bricks, metal structures, and electric cable, the placement of a permanent global utilities infrastructure on the Moon will commence. Although technological advances and innovation are expected as a by-product of lunar development, virtually all of the infrastructure needs of the Moon can be satisfied by simply adapting existing Earth-based technologies to the lunar environment. There is no need for technological breakthroughs.

7.2 LUNAR ELECTRIC POWER

Electric power will be as important for the development of the Moon as food and shelter were for the spread of civilization across the Earth. Since there is no electric power system on the Moon right now, every early lunar mission must carry its own power supply, and when that power supply becomes exhausted, the mission must end. The dependency on self-power results in high transportation costs and limits the scope and duration of every mission.

When continuous and abundant supplies of electric power become available, the full scientific and material benefits of the Moon will be realized. Lunar base development and lunar exploration will proceed apace with little or no requirement for material support from the Earth. Missions to the Moon will no longer require spacecraft to carry their own power supplies with them - they will simply "plug in" to the existing lunar electric grid when they arrive on the lunar surface.

The highest priority of the Planet Moon Project will be given to creating the means to support exploration and development projects. During the first phases, greater emphasis will be placed on constructing the lunar electric power and transportation systems, rather than conducting scientific experiments. The rationale for this approach is simple: first build the laboratory, then conduct the experiments. Once the "laboratory" has been built, virtually unlimited energy and material resources will become available, and global scientific and other human activities on the Moon will be possible on a large scale. There are two principal options for providing electric power on the Moon: nuclear reactors and photovoltaic (solar) cells. Both of these sources of power have been deemed to have limitations that will delay large-scale lunar missions well into the future. However, solar cells will be the likely source of electric power for both near- and long-term lunar exploration and development projects.

7.2.1 Nuclear power

Nuclear reactors are often mentioned as a likely source of electrical power for future lunar bases, for several reasons. First, a significant body of knowledge has been accumulated on the design and safe operation of nuclear reactors. That body of knowledge can be applied directly to the design of a nuclear reactor that can operate safely and effectively on the Moon. Second, nuclear reactors can provide continuous electrical power at levels (100kW-l MW range) that will be needed for initial lunar base requirements. Third, all of the components of a nuclear reactor can be built and tested on the Earth, and transported to the Moon with existing rocket technology.

Unfortunately, the advantages of nuclear reactors are offset by significant negative factors. The design, testing, and construction of a flight-worthy nuclear reactor would be expensive and time-consuming. The delivery costs would also be high. But the biggest problem for nuclear reactors is the potential for political reaction, particularly in the United States, against the launch of nuclear reactors from the Earth and their use in space.

The launch and operation of nuclear reactors present legitimate concerns for public safety and for the environments of the Earth and the Moon. There are definable risks of the failure of a launch of a rocket containing radioactive elements, and of the contamination of the lunar environment resulting from the operation of a reactor on the Moon.

While these risks may be reasonable and acceptable, and appropriate means for protecting the Earth and Moon environments can be developed, the level of risk perceived by the public may be sufficiently high that the nuclear option will not be acceptable. Political forces have been successful in blocking or curtailing the construction in nuclear reactors in many countries, and for attempting to prevent the launch of space probes that contain small amounts of plutonium, such as the Galileo mission to Jupiter and the Cassini mission to Saturn. It is probable that those same forces would also attempt to impede the development and deployment of a nuclear power source for the Moon. Although nuclear power has several positive features for lunar applications, its costs, long development time, and potential for political roadblocks limit its promise as the principal source of power on the Moon.

7.2.2 Solar electric power

The second option for the production of electric power on the Moon is photovoltaic (solar) cells. The Moon has an abundant supply of energy in the form of sunlight; it is constant,1 unobstructed, and virtually inexhaustible, and it can be converted into electric power by solar cells. Solar cells have been a source of electric power for long-duration spacecraft for several decades, and they have been used successfully on the Moon. The first stages of a functioning lunar electric power supply will therefore be established by simply transporting "off-the-shelf" solar arrays from the Earth to the base camp on the Moon.

One potential drawback with sunlight as a source of energy is that it is not available during the lunar night.2 Consequently, some form of energy storage device,3 such as batteries or flywheels, will be needed to provide power for nighttime lunar operations. The incorporation of energy storage devices substantially increases the mass, cost, and complexity of solar power systems, and for this reason solar cells have been regarded as less attractive as a primary power source for lunar operations than nuclear reactors.

Nevertheless, as noted in Chapter 3, the lunar regolith is an abundant supply of materials that can be used as feedstock for the Moon-based manufacture of solar cells. If a number of Earth-made solar arrays were placed on the lunar surface and connected into an electric power grid, the grid would supply the power required for solar cell fabrication equipment to make solar cells from the lunar regolith. Another possibility is a solar-powered mobile robotic factory that "paves" the lunar surface with additional solar cells (see Appendix A). The lunar-made solar cells would be added to the electric grid, and steadily increasing power levels on the Moon would thus be realized. The combination of inexhaustible sunlight that is unobstructed due to the lack of an atmosphere (and only rarely obstructed by the Earth during an eclipse of the Sun) and the local availability of lunar regolith feedstock for the

1 Sunlight on the Moon is only interrupted during lunar eclipses, when the Earth is interposed between the Moon and Sun. Also, because there is no atmosphere to attenuate it, sunlight that arrives at the lunar surface is about eight times as intense as the sunlight that reaches the surface of the Earth.

2 The Moon rotates on its axis once every revolution around the Earth, and half of the Moon is always in daylight and half is in darkness. Images from the SMART-1 spacecraft indicated that a crater rim at the north pole of the Moon may receive sunlight continuously; all other areas of the Moon experience periods of darkness.

3 Unmanned (robotic) lunar bases may not need continuous power. They can "power down" to a limited extent during the lunar night and resume operations during the lunar day, thus obviating the need for large power storage devices. However, they typically require "keep alive" power to prevent damage to sensitive electronics caused by the extreme cold of the lunar night.

construction of solar arrays has given rise to a substantial body of literature on the subject of generating electrical power on the Moon.

7.3 THE LUNAR POWER SYSTEM (LPS)

The most ambitious plan for generating electrical power on the Moon with solar cells that are made from lunar regolith materials has been put forward by Criswell and Waldron. They have patented and published articles on a plan for supplying electric power to the Earth at low cost from a Lunar-based Solar Power system (LPS). They envision the construction of large solar collecting bases on opposing (east and west) limbs of the Moon. The reason for the placement of bases on opposite sides of the Moon is to assure that one or the other of the two bases is always in sunlight, thus providing power to the Earth continuously.

The power that would be generated at each of the two lunar base sites of the LPS would be converted to microwave energy, beamed to receiving stations on Earth, reconverted into electricity, and then fed into electric power grids on the Earth (Figure 7.1). The estimated power that could be generated on the Moon by the

Figure 7.1. The Lunar-based Solar Power system (LPS) (courtesy of Dr. David R. Criswell): 1, sunlight; 2, Moon; 3, sunlight is converted to electric power by solar arrays on the Moon; 4, electric power is converted to microwave energy on the Moon and beamed to the Earth; 5, relay stations in Earth orbit send microwave energy to the Earth; 6, rectennae convert microwave energy to electric energy and deliver it to power grids on the Earth.

Figure 7.1. The Lunar-based Solar Power system (LPS) (courtesy of Dr. David R. Criswell): 1, sunlight; 2, Moon; 3, sunlight is converted to electric power by solar arrays on the Moon; 4, electric power is converted to microwave energy on the Moon and beamed to the Earth; 5, relay stations in Earth orbit send microwave energy to the Earth; 6, rectennae convert microwave energy to electric energy and deliver it to power grids on the Earth.

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Figure 7.2. Circumferential electric grid at 85° south latitude. Solar power stations that are positioned at regular intervals along an electric grid at 85° south latitude provide continuous electric power to the grid (Sharpe).

LPS is in the multi-terawatt range (one terawatt equals one trillion watts, or one million megawatts). The projected power levels from the LPS will thus exceed the present combined output of all electric-generating power plants on Earth (Criswell, 1994), and will be able to supply Earth with all of its future energy needs. The lunar power system has the potential to be highly profitable (see Appendix L). If that economic potential is realized the Earth will be the recipient of an abundance of clean, low-cost electric power.

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Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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