For long-term sustainability, a space colony should be close to self-sufficient.
Mining and
refining the Moon's materials on-site – for use both on the Moon and elsewhere in the Solar System – could provide an advantage over deliveries from Earth, as they can be launched into space at a much lower energy cost than from Earth. It is possible that large amounts of cargo would need to be launched into space for interplanetary exploration in the 21st century, and the lower cost of providing goods from the Moon might be attractive.
Space-based materials processing In the long term, the Moon will likely play an important role in supplying space-based construction facilities with raw materials. Microgravity in space allows for the processing of materials in ways impossible or difficult on Earth, such as
"foaming" metals, where a gas is injected into a molten metal, and then the metal is
annealed slowly. On Earth, gas bubbles may rise or fall due to their relative density to air, but in a
zero gravity environment this does not happen. The
annealing process requires large amounts of energy, as a material is kept very hot for an extended period of time (allowing the molecular structure to realign), and this too may be more efficient in space, as the vacuum drastically reduces all heat transfer except through
radiative heat loss.
Exporting material to Earth Exporting material to Earth in trade from the Moon is problematic due to the cost of transportation, which would vary greatly if the Moon is industrially developed. One suggested trade commodity is
helium-3 (3He) which is carried by the
solar wind and accumulated on the Moon's surface over billions of years, but occurs only rarely on Earth. Helium-3 might be present in the
lunar regolith in quantities of 0.01 ppm to 0.05 ppm (depending on soil). In 2006 it had a market price of about $1,500 per gram ($1.5M per kilogram), more than 120 times the value per unit weight of
gold and over eight times the value of
rhodium. In the future 3He harvested from the Moon may have a role as a fuel in
thermonuclear fusion reactors. It should require about of helium-3 to produce the electricity that Earth uses in a year and there should be enough on the Moon to provide that much for 10,000 years. In 2024, an American startup called
Interlune announced plans to mine helium on the Moon for export to Earth. The first mission plans to use NASA's
Commercial Lunar Payload Services program to arrive on the moon.
Exporting propellant obtained from lunar water To reduce the cost of transport, the Moon could store
propellants produced from lunar water at one or several
depots between the Earth and the Moon, to resupply rockets or satellites in Earth orbit.
Lunar water ice s) Lunar scientists had discussed the possibility of water repositories for decades. They are now increasingly "confident that the decades-long debate is over" a report says. "The Moon, in fact, has water in all sorts of places; not just locked up in
minerals, but scattered throughout the broken-up
surface, and, potentially, in blocks or sheets of ice at depth." The results from the
Chandrayaan mission are also "offering a wide array of watery signals." It is estimated there is at least 600 million tons of ice at the north pole in sheets of relatively pure ice at least a couple of meters thick.
Solar power satellites Gerard K. O'Neill, noting the problem of high launch costs in the early 1970s, proposed building
Solar Power Satellites in orbit with materials from the Moon. Launch costs from the Moon would vary significantly if the Moon is industrially developed. This proposal was based on the contemporary estimates of future launch costs of the Space Shuttle. On April 30, 1979, the Final Report "Lunar Resources Utilization for Space Construction" by General Dynamics Convair Division under NASA contract, NAS9-15560 concluded that the use of lunar resources would be cheaper than terrestrial materials for a system comprising as few as thirty Solar Power Satellites of 10 GW capacity each. In 1980, when NASA's launch cost estimates for the Space Shuttle were grossly optimistic, O'Neill et al. published another route to manufacturing using lunar materials with much lower startup costs. This 1980s SPS concept relied less on human presence in space and more on partially self-replicating systems on the lunar surface under
telepresence control of workers stationed on Earth. ==See also==