Overview of Lunar Materials and Their Utilization
Why lunar materials?
Lunar materials are more economically attractive as feedstocks for large scale space-based industrialization than are materials blasted up from Earth, in the overall analysis.
Whether lunar materials are more desirable than materials from asteroids near Earth is the subject of much debate. This website presents the merits of both cases. It would not be surprising to see both lunar and asteroidal materials used, in a synergistic manner.
The Earth is 81 TIMES as massive as the moon. As a result, it costs a whole lot more to get materials off the Earth than it does to get them off the Moon.
In order to stay as nontechnical as possible, a visual example will be presented first.
Remember the Apollo program, specifically the lunar module. The lunar module consisted of two parts -- the lander and the launcher. The launcher, which returned the men from the moon's surface back into orbital space, was not much taller than a man. The fuel tank for it was set off in a corner, and smaller than a man -- if you had one of those in your room, you could roll it over and sit on it. In contrast, the fuel and vehicle required to get a couple of guys and their bags of dirt off of the Earth would be huge and complex.
Indeed, imagine what would be required to LAND a launchable rocket onto the Earth from space (especially without the assistance of a braking atmosphere). We had to land the return rocket onto the Moon.
This should give you an idea about how easy it is to get on and off the moon compared to get on and off of the Earth, assuming chemical rocket means.
(Remember, we did that way back in 1969, just 12 years after the first successful launch of anything into space, i.e., just 12 years after the Russian Sputnik unmanned satellite in 1957. )
Secondly, because of the Moon's low gravity and lack of atmosphere, engineers have decided that we don't even need rockets to get stuff into space. There are designs and laboratory prototypes of an electric "slingshot" called a "Mass Driver" which would need no fuel. (It is actually a launch tube, like a pea shooter.) The Mass Driver would shoot a steady stream of small fiberglass containers of lunar minerals into orbit to a "Mass Catcher", whereby the bags will have slowed down to almost zero speed due to gravity by the time they reach the catcher. The fiberglass containers encasing the minerals would be made from lunar material on the surface. In the long term, this may be the cheapest way to get materials into Earth orbit in very large quantities, quickly.
A prototype Mass Driver was developed for lunar duty by the Space Studies Institute (SSI). The Mass Driver and its initial power supply allegedly could be launched by one of today's existing rockets as one payload, though additional launches would be necessary to deliver the fuel propellant, vehicle and general infrastructure required to deliver it from low Earth orbit to the Moon's surface.
However, the Mass Driver may be a high risk device in the initial stages of space development, and one should consider conventional chemical rocketry for lunar launch in the first missions. Nevertheless, in the long run, the Mass Driver could make the Moon more competitive with asteroids as a source of material.
(The Mass Driver is the antithesis of rockets. Unfortunately, an Earth-based Mass Driver is not very feasible due to the atmosphere -- the payloads would burn and possibly break up like meteors in Earth's atmosphere, as well as be blown into unpredictable courses, especially at the speeds required to shoot stuff off of Earth.)
In a private sector scenario, the lunar material might be processed mainly by industry based in orbital space, and not on the Moon. Why put the industry in space?
Notably, like with the transport of asteroidal material, material delivered into space using a Mass Driver would dwarf the quantities that could be feasibly supplied from Earth, and at a cost per pound that would become trivial within a few years of completion of a serious first set of infrastructure.
What is lunar material?
Lunar material is pretty much like Earth's crust -- silicate dirt -- oxides of metals and silicon. Unlike asteroids, there are no big free metal ores on the moon (though there are some significant quantities of free iron granules in the soil, thanks mostly to asteroid craters and the lack of water to rust it). Oxygen is abundant and can be cooked out of the dirt, but other volatiles are in questionable supply in lunar soil with the exception of ice in super cold lunar craters.
While metals can be extracted by space-based processing, the easiest things to make from semi-processed lunar materials are "lunarcrete", fiberglass, various glass-ceramic composites, and oxygen. Notably, oxygen, which makes up roughly 40% of lunar soil (bound in molecular silicates and metal oxides), makes up 86% of the weight of fuel propellants in hydrogen-oxygen rocketry, with hydrogen making up the other 14%. Therefore, at least 86% of the fuel used in orbital operations could come from the moon. Notably, there are substitutes for hydrogen, such as atomized metal powder, such as is used for the Shuttle's two "solid rocket boosters", and which can be readily made in space from lunar or asteroidal materials. Thus, fuel to transport the materials is another product of lunar material.
Mining the Moon
The moon is like a beach of fine powder. Mining this powder can be done by bucket-cable-reel draglines instead of heavy Earth-breaking machinery. The moon's powdery nature is due partly to the total lack of a protecting atmosphere which has allowed every meteor, micrometeor, and cosmic particle to bombard the surface and pulverize it over eons. This is combined with the fact that the Moon has been geologically dead (no reformation of rocks by sediment, crust folding, or volcanics) for the last 3 billion years. The Moon is small and cooled off quickly, in contrast to Earth, which explains differences in their geologic nature. Even the eons-ago pulverization by gigantic asteroid impact shocks has been preserved. Indeed, the Moon is so finely powdered that Apollo planners were concerned with sinkage of the lander and astronauts. Recall the fine bootprints, sunken yet every contour of the boot finely imprinted. Recall Neil Armstrong comparing the surface to charcoal ash. The moon's powdery nature is ideal for cheap mining and mineral processing.
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