Appendix D. The Eye of the Beholder
D1. Ring City, Shackleton Crater, Moon
A permanent colony on the Moon's surface cannot exist without protection from solar flares, coronal mass ejections (CMEs) and galactic radiation. On August 7, 1972, a massive solar flare occurred between the Apollo 16 and Apollo 17 missions. Had this flare erupted while astronauts were on the Moon, they might have died. Solar flares and galactic cosmic rays also pose a significant risk for human travel to Mars (and may make a permanent Mars colony impossible).
On Jan. 20, 2005, a giant sunspot named NOAA 720 exploded, the beginning of a days-long "proton storm." The largest recorded CME was in September of 1859, observed by astronomer Sir Richard Carrington; it reportedly caused telegraph offices to burst into flames. A modern "Carrington Event" could take down power grids (by knocking out large, high-voltage transformers), perhaps for months or years. These are few of the recorded major solar flare events; smaller flares can occur once a week. The Moon is a dangerous place.
The question is: how can people survive indefinitely on the Moon? One answer is to live underground; a habitat buried below the lunar regolith may be the safest solution. Instead of viewing the vast grandeur of space, people would live like moles in sealed caves and bunkers. Lava tubes under the Aristarchus Plateau or Schroter's Valley may be good locations for an underground colony.
Shackleton Crater at the lunar South Pole is a good location for a permanent colony on the Moon's surface. Because the Moon's rotational axis is tilted by only 1.54 degrees (compared to Earth's 23.5 degrees), some areas near its poles are left in permanent shadow, while nearby regions remain sunlit for most of the year. As the Moon rotates on its axis, the four-kilometer-high crater rim protects colonists from deadly solar flares. The crater rim also protects against most meteorite strikes, which are concentrated near the lunar equator.
For a colony in Shackleton Crater, being in perpetual shadow may sound dreary, but reflected sunlight will usually be visible from the crater's rim. At least lunar residents will have a spectacular view of the southern stars, including the Magellanic Clouds. Living on the crater floor will be less oppressive than living in underground tunnels.
However, a Moon base in Shackleton Crater will not protect colonists from galactic radiation, including cosmic rays. High-energy subatomic particles originating from outside our Solar System continuously bombard the Moon. Fortunately, there is an engineering solution to shield against galactic radiation on the Moon. A superconducting cable twenty kilometers in diameter carrying a modest 50 amperes will generate a Störmer magnetic field that deflects most cosmic rays to the center of the ring. The radiation-free area is a narrow band twenty meters on each side of the superconducting cable. The toroidal volume of the field encloses less than two square kilometers of habitable area. Everyone must live on top of the Ring, which is the only permanently safe place on the lunar surface. [Acknowledgement to Franklin Cocks, Analog Jan/Feb 2007, for the calculations on the Störmer magnetic field.]
Ring City inside Shackleton Crater is a circle of 1,500 insulated pressure domes that straddle the 62.8-kilometer circumference of the superconducting cable. Each 40-meter-diameter (20-meter-high) hemisphere is made of aluminum and polyethylene to further absorb radiation. The domes are joined edge to edge, like silver beads on a necklace, with a public corridor bisecting each and an emergency pressure door where the domes touch (to isolate a dome struck by a meteorite). In the underground basement below each dome are sleeping quarters (further shielding from radiation), stocked with emergency supplies and extra breathing air — a hidey-hole during emergencies.
The geographic lunar South Pole is located on the steep rim of Shackleton Crater. This is the position of the Peak of Eternal Light. [Actually, as revealed by NASA's "illumination map" from the Lunar Reconnaissance Orbiter Camera (LROC), there are several perpetually illuminated peaks at the South Pole. Only an occasional six-hour eclipse (caused by the Earth blocking the sun) interrupts sunlight.] A simple mast with vertical solar arrays that rotate once per month provides (nearly) continuous electrical power to Ring City.
Another advantage to living in the dark center of Shackleton Crater is that it's extraordinarily cold: minus 238 degrees Celsius, just 35 degrees above absolute zero. Frozen water and methane, concentrated by the cold trap, are valuable resources for the city. In addition to domestic and agricultural water, H2O can be split into hydrogen and oxygen to provide rocket fuel and breathing air. The methane will be useful for agriculture.
Ring City in Shackleton Crater is designed to be a safe and sustainable lunar colony. It provides protection from solar and galactic radiation. Continuous electrical power and easy access to water and methane provide essential resources. There is no better place for a colony on the surface of the Moon.
D2. Lunar Space Elevator
The Moon is far away and large. If the Moon is developed for resource mining, transportation is essential. An ideal lunar transport system consists of two parts: a space elevator and a maglev rail network on the ground.
A space elevator is more practical on the Moon than on Earth. Lower gravity requires a smaller ribbon cable (which may not need novel materials) and there is no wind or weather to buffet it. Sinus Medii, the nearest spot on the lunar surface to the Earth, is a logical site to anchor a space elevator. Since the Moon is tidally locked with one side facing the Earth, the elevator will always point toward Earth. Several designs for a lunar space elevator exist, but all require a cable extending into space for hundreds of kilometers. Spaceships will dock on the space elevator at a "picogravity station" at the L1 Earth-Moon Lagrange point, 56,000 km away from the Earth-facing side of the Moon. An elevator climber will take cargo up and down the cable.
A second space elevator (called "Moonstalk" in the novel) at the L2 Earth-Moon Lagrange point, 67,000 km from the center of the Far Side of the Moon, could support radios in the focal point of Daedalus Crater.
D3. Lunar Maglev Railroad
The surface area of the Moon is bigger than Europe, China, the USA and Brazil combined, about 25 percent of the land area on Earth.
Commercial exploitation of lunar resources (minerals or helium-3) will require access to vast areas of regolith. Local rockets are feasible (called "rockhoppers" in the novel) but are hazardous, expensive, and only useful for people or light loads. Moon buggies are suitable for short trips for astronauts in space suits. Electric trucks are possible, but will either be slow in loose regolith, or will need extensive roads.
The best solution for a long-range lunar transportation network is maglev train technology. Low lunar gravity reduces the energy needed to levitate the train. The vacuum on the surface eliminates air resistance, allowing efficient, high-speed travel 1000 kilometers per hour, or more. Where possible, train routes will avoid craters and mountains.
For protection against radiation, UV light corrosion and lunar dust, a maglev railroad should run in tunnels or underground (called the "Underground Railroad" in the novel). Automated robots could construct "cut and cover" rail tunnels, using lunarcrete (also known as "mooncrete") as a covering material.