A moon colony, or lunar settlement, is a proposed establishment of human settlements in or on the Moon's surface. Habitation of lunar land could potentially benefit Earth. Some examples include providing by mass driver the materials for space-based solar power on Earth, solving overpopulation, providing Helium-3 for fusion power and providing the materials to build in space large colonizing vessels to make cyclically repeating voyages to Mars.
Placing a colony on a natural celestial body would provide an ample source of material for construction and radiation shielding at the colony and in free space. The energy required to send objects from the Moon to space is much less than from Earth to space. This could allow the Moon to serve as a construction site for spacecraft. Fuel for spacecraft could be launched by mass driver to a depot in free space. Some proposals include using electric acceleration devices (mass drivers) to propel objects off the Moon without building rockets. Others have proposed momentum exchange tethers (see below). Furthermore, the Moon does have some gravity, which experience to date indicates may be vital for fetal development and long-term human health. Whether the Moon's gravity (roughly one sixth of Earth's) is adequate for this purpose, however, is uncertain.
In addition, the Moon is the closest large body in the solar system to Earth. While some Earth-crosser asteroids occasionally pass closer, the Moon's distance is consistently within a small range close to 384,400 km. This proximity has several benefits:
Industries (including space tourism), basing for security forces, and unique technical research facilities. Transit time is short. The Apollo astronauts made the trip in three days and future technologies could improve on this time. The short transit time would also allow emergency supplies to quickly reach a Moon colony from Earth, or allow a human crew to evacuate relatively quickly from the Moon to Earth in case of emergency. This could be an important consideration when establishing the first human colony.
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The round trip communication delay to Earth is less than three seconds, allowing near-normal voice and video conversation, and allowing some kinds of remote control of machines from Earth that are not possible for any other celestial body. The delay for other solar system bodies is minutes or hours; for example, round trip communication time between Earth and Mars ranges from about eight minutes to about forty minutes. This again would be of particular value in an early colony, where life-threatening problems requiring Earth's assistance could occur. (See, for example, Apollo 13.) On the Lunar near side, the Earth appears large and is always visible as an object 60 times brighter than the Moon appears from Earth, unlike more distant locations where the Earth would be seen merely as a star-like object, much as the planets appear from Earth. As a result, a Lunar colony might feel less remote to humans living there. A Lunar base would provide an excellent site for any kind of observatory. Particular advantages arise from building observatory facilities on the Moon from Lunar materials. As the Moon's rotation is so slow, visible light observatories could perform observations for days at a time. By using shades to bock the sunlight and block light from the surroundings a lunar observatory could view the stars 24 hours per day every day of the year. It would be possible to maintain constant observations of specific targets with three observatories separated by 120 degrees longitude on the Moon. The fact that the Moon has low geological activity along with the lack of widespread human activity results in a remarkable lack of mechanical disturbance, making possible highly sensitive interferometric telescopes on the Lunar surface, even at relatively high frequencies such as visible light. A Lunar base could also hold a future site for launching rockets, to distant planets such as Mars. Launching rockets from the Moon would be an easier prospect than on Earth due to the Moon's lower gravity requiring a lower escape velocity. A lower escape velocity would require less propellant but rocket propellant would cost more. A farm at the Lunar North Pole could provide eight hours of sunlight per day for rotating crops, a beneficial temperature, radiation protection, insects for pollination, and all other plant needs artificially during the local summer for a cost. One estimate suggested a 0.5 hectare space farm could feed 100 people. A moon colony could provide us with in orbit infrastructure for colonizing other planets.
Assuming it feasible and the medical issues of low gravity is solved, there are many compelling reasons to found a society in and on the lunar surface in the short term, rather than other bodies of our solar system. These include:
- The Moon has low escape velocity. So if electrical launch from Moon to orbit is achieved, it would cost less to ship materials from the Moon to space or Earth than it would cost to ship materials from Mars. This exportation of lunar material to other places could pay off the large investment required for a functional, human/robot colony. This trade would benefit other places in need of moon material.
- The delay in Earth to Moon communication is small, nearly three seconds round trip communications delay. In the case of life threatening scenarios, humans on Earth would have more time to address the problem and send help, increasing the probability of the colonists' survival. No other celestial body has such a dependably short communications delay.
- Because of the lack of atmosphere, combined with extremely slow rotations, sunlight could be harvested with virtually no interference at the poles. The poles location also serves as a superb infrared observation point. Observations could be continuous from very cold locations.
- The moon's regolith is rich in oxygen, titanium, silicon, aluminum, iron and magnesium. Hydrogen has been detected in significant amounts.
In order to create a thriving civilization, one must gain the support of the general public to pay for expense for importing materials and equipment and designing exact industrial processes which would be suited to the lunar environment.
Designs and Ideas
The 1950's science fiction ideas of geodistic domes and sheild generatators to solve both radiation and atmospheric requirements will be inadequate.
Difficulties to Solve
- If no electrical launch of material from the Moon to orbit is achieved, the cost of importing hydrogen and carbon for rocket fuel would make exporting material from the Moon more expensive than exporting material from Mars.
- Industrial processes to recover volatiles on the Moon will require the use of pressure vessels and air-locks. Air-lock doors require gaskets. Rubber and silicone used as gasket material on Earth require both hydrogen and carbon. Either sources of these materials which are scarce on the Moon must be found or a substitute material such as lead must be used. There is some doubt if there are any available sources of lead on the Moon.
- The highest concentrations of hydrogen so far detected on the Moon are estimated to be equivalent to about 1% ice by weight.  These concentrations of hydrogen are only found in the permanently shadowed bottoms of some craters in the polar regions of the Moon. The scarcity of hydrogen and the darkness and low temperatures where it is found combine to make the probable future cost of hydrogen on the Moon quite high, and there can be no colony without hydrogen.
- Known effects of long-term space flights on the human body
- House Science Committee Hearing Charter: Lunar Science & Resources: Future Options | SpaceRef - Space News as it Happens
- Lunar farming: achieving maximum crop yield for exploration of space.
- David Schrunk, Burton Sharpe, Bonnie Cooper, Madhu Thangavelu, The Moon, Resources, Future Development, and Settlement, (Springer, Second Edition ,2008)