A permanent manned base on the Moon is often described as an important first step in the colonisation and exploration of the rest of the Solar System. It may seem odd that something that is on average a mere 383,000 km (237,000 miles) away from the Earth could be useful as a first step towards travelling to Mars for example, given that Mars can be between approximately 60 million kilometres (36 million miles) and 400 million kilometres (250 million miles) away.

Full MoonCredit: Gregory H. ReveraAlthough there are many other reasons, the closeness of the Moon to Earth is actually a benefit. As the Moon is not so far from home, it makes it more suitable for testing. With the Moon being at the moment just a few days travel away - although preparing for the trip would currently take much longer once a viable Moon launch and travel system has been established - should something go wrong the shorter distance and travel time would make it much easier to send a rescue mission to any permanent colony. A disaster on Mars, given that the travel time to Mars is, at Mars' closest approach, likely to be in the region of two thirds of a year. That sort of distance would make any serious problem fatal for any colonists. By first building on the Moon, kinks in how the colony was constructed could be ironed out first. Naturally Mars is a different environment to the Moon, so there would be differences in how to build a colony, but more generalised testing could be carried out.

It may be some years before a permanent Mars base is established anyway, even though there are possibly private ventures that plan on travelling to Mars.[3] However, flyby's, such as the Inspiration Mars Foundation's planned mission[1], don't really count. The Dutch non-profit Mars One wants to establish a permanent Martian base, and fund it by broadcasting a reality TV programme that follows the entire mission from astronaut selection through to constructing the base. Exactly how successful a base constructed by wannabe reality TV stars will be is somewhat open to question.[2]

Reducing the Cost of Orbital Construction

Anything that can be made on the Moon can be put into any orbit more cheaply from there than from Earth. Shipping items from the Moon to LEO (Low Earth Orbit, approximately 160 kilometres/99 miles above the Earth) is cheaper than shipping them from Earth to LEO. This is because they are not being shipped from the bottom of Earth's gravity well; the Moon's, with its lower gravity, is smaller and requires less energy to leave. This lower cost would also make it more worthwhile to ship raw materials, whether ore or intermediate items such as metal ingots, to orbital manufactories in LEO, Geostationary Earth Orbit (GEO, 42,165 kilometres/26,199 above the Earth) or to the Lagrange points.

Manufacturing in space has many advantages. Power, with adequate solar panels, is easily obtained and cheap. Certain products, such as crystals, can be manufactured to a much higher standard and quality in a micro-gravity environment than they can on Earth. The problem with manufacturing here is getting the supplies there; it is, as stated, cheaper to do so from the Moon.

Lagrangian PointsCredit: NASALagrangian Points

The Lagrangian points, named after Joseph Louis Lagrange, are five points, referred to as L1 to L5. The first three were discovered by Leonhard Euler several years before Lagrange discovered the last two. The points are comparatively stable places in a two body system where another object of minor mass could be placed with minimal movement. The L1 and L2 points are the most useful for shipping resources from the Moon, although L2 is on the far side of the Moon and much less useful for then shipping resources to earth. L1, situated between Earth and the Moon, is more usefully placed for both bodies.[4]

Although L1, L2 and L3 are not as stable as L4 and L5, by orbiting the point it is possible to stay in position comparatively easily. The Lagrangian points are ideal for extensive orbital construction.

Lunar Resources

Existing data from surveys carried out of the Moon's surface and experiments carried out on Luna rocks from the Apollo missions shows that useful elements on the surface are predominately light elements at the low end of the periodic table, although many of these are still extremely useful.

Solar PanelsCredit: NASAPower

With the Moon's thin atmosphere solar panels can work much more effectively than they do on Earth, where the Sun's emissions are blocked by the Earth's thicker atmosphere. This would make solar power a much better and more efficient source of power than it is on Earth. Silicon, which is the most common element used in the manufacture of photovoltaic cells, is also common on the Moon

A Lunar day lasts approximately 14 Earth days and the night is the same length. Although solar panels work during the day, they don't work at night. Having no power during the Lunar night would be a major problem, so a method of storing any excess power generated during the day would be required. Alternatively, solar panel farms could be scattered around the circumference of the Moon so that at least one is always in sunlight. This would provide a constant source of power. Getting the power to where it's needed from the solar farms would be more difficult; either microwave relays could transmit it around the surface, or to and from orbiting satellites, but this would be dangerous for anything that crossed the beam. Otherwise, a lot of cable could be laid around the Moon, creating an electrical grid. The solar farms could also be combined with other outposts.

Periodic TableCredit: http://en.wikipedia.org/wiki/File:Periodic_table.svgElements

A number of elements at the low end of the periodic table have been discovered to be quite common at or near the surface of the Moon. These are oxygen, iron, silicon, magnesium, calcium, aluminium, manganese and titanium. Oxygen is rather useful for breathing, silicon has electronics uses including the creation of solar panels and iron, magnesium and titanium are all useful in construction. Light elements like titanium and aluminium are also cheaper to launch off the Moon's surface, and can be used in orbital construction. NASA's Lunar Prospector probe also detected the heavier elements uranium, thorium and potassium, which also helped show the areas likely to have the useful, and expensive, rare earth elements.[5]

Smelting

Smelting metal from mined Lunar rock can be done cheaply using focused sunlight to smelt the ore. This can be done on the Moon, although only during the Lunar day, or also in orbit. A smelter at a suitable point could be in permanent operation as long as it could be supplied with raw materials to process. Shipping raw materials from the Moon is probably not the cheapest way of going about it.

Water

One thing that was discovered by the Lunar Prospector was that there is more water than expected on the Moon, primarily at the poles where many craters are in permanent shadow. Water has over the years migrated from impacts on the Lunar surface to the poles. Water has many uses, including helping to support life. The hydrogen and oxygen from water can also be used as spaceship fuel; the Shackleton Energy Company announced a plan to process Lunar water into rocket fuel and ship it to LEO.[6]

Moonbase AlphaCredit: http://en.wikipedia.org/wiki/File:Moonbase_alpha.jpgConstructing the Base

Any base on the Moon would require a fairly extensive construction programme, especially if you want to end up with something of the complexity of Moonbase Alpha.

Underground, Overground

Ideally the majority of a base would be buried below the Lunar surface and regolith. This would provide protection from threats such as cosmic rays, Solar radiation and micrometeorites. The excavation of a complete subterranean base would be more difficult than constructing at or near the surface. Initially, surface structures could be constructed and then covered with Lunar material to provide extra protection. Using inflatable buildings could be an initial possibility; an inflatable module has been bought by NASA for the International Space Station from Bigelow Aerospace.[7] Similar inflatable structures could be erected on the Moon.

After the base has been established, it would then be easier to go underground with much of it. Some of the base would of necessity need to remain on the surface, such as communications antenna, radar, airlocks and landing pads for vehicles. Even should a subterranean hanger for any craft landing on the Moon be constructed, something, even if just an opening, would need to be on the surface to allow access to the hanger.

The Dark Side of the Moon

The dark side of the Moon is not actually dark. It is the Lunar Farside and the majority cannot be seen from Earth, making it Earthdark. A base constructed on the Farside would have advantages for radio telescopes during the Lunar night. The Earth is very radio-bright, due to all the electromagnetic communication that goes on. Having the Moon between the telescope and the Earth would allow much fainter signals to be detected than can be done from an Earth-based telescope.

During the Lunar day, the Sun would naturally make it unusable; the Sun is far brighter than the Earth.

3D PrinterCredit: http://en.wikipedia.org/wiki/File:ORDbot_quantum.jpg3D Printing

3D printing is a technology that is starting to mature and has been considered for creating Lunar bases and satellites.

What are 3D Printers?

3D printing has actually been around for several decades. It is the process of printing a three dimensional object from a digital model, using layers of the printing material which are gradually added on top of each other to build up the finished item. These items can then be combined to make a greater whole, so that a complex item can be effectively printed out by simply printing its constituent pieces.[8]

Recent advances in 3D printing have led to both NASA and ESA looking into 3D printing for both structures on the Moon and spaceship and satellite construction. Washington State University was approached by NASA with some artificial Lunar material to see if it was possible. Initial tests suggest that making buildings from scratch is still some way off, but creating components to repair broken equipment is much closer.[9][10][11]

3D printing could be used for simple items such as structures, but 3D printers have been used to create even fairly complex mechanical items made from multiple printed parts. The American non-profit, Defense Distributed, in a somewhat controversial series of experiments, managed to successfully create the parts to construct a working assault rifle using a 3D printer. Ignoring any political opinions about being able to create assault weapons so easily, the fact that they managed to create a fairly complex mechanical device with some pretty precise tolerances using a 3D printer is quite impressive.[12]

The Asteroid ErosCredit: NASAAsteroid Mining

Mining asteroids for resources is, in some ways, better than mining the Moon. Many asteroids have heavier elements than are found on the Moon and these elements can be easier to get at. So far, two asteroid mining companies, Deep Space Industries and Planetary Resources, have been setup to mine the asteroids. The first choice of asteroids are those known as Near-Earth asteroids.[13] However, these are not always near the Earth; it just means that there orbits are near Earth's. Some are always closer to the Sun, some are further away and some cross Earth's orbit.

This variation means that the asteroids are frequently not somewhere that is easy to get either too or from; some can actually be further away than Mars. This makes it much more difficult to go to, mine, and return from with the processed material, than the Moon. The Moon would actually be a useful base for building an infrastructure to exploit the asteroids.

NASA has plans to capture and tow a near-Earth asteroid into Lunar orbit for exploration and mining. Once towed into orbit, astronauts could be sent there and the rock mined, as well as being used as the focus of an orbital exploration and manufacturing base.[14]