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| Lunar base control room, Courtesy NASA, artist Rick Guidice |
An obvious question related to the exploration and settlement of the
moon is, "What do we do there?" America's NASA asked a similar
question in 2006 and developed a set of
Lunar Exploration Objectives.
Initially, lunar residents will focus on obtaining those
products that would make them self-sufficient and not dependent on
expensive products brought from earth. It may be impossible to
completely eliminate dependence on earth products, but the goal should
be to maximize the use of lunar sources that are less expensive than
products transported up from earth's gravity well. Alternatively,
sources elsewhere in the solar system, such as asteroids, should be
investigated.
Mining
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| Mining on Moon, Courtesy of NASA |
For long term sustainability, a space colony should be close to self sufficient. On site mining and refining
of the Moon's materials could provide an advantage over deliveries from
Earth – for use both on the Moon and elsewhere in the solar system –
as they can be launched into space at a much lower energy cost than
from Earth. With the expected immense cost of interplanetary
exploration in the 21st century, the lower cost of providing goods from
the Moon could be very attractive.
Water and Oxygen Extraction
Water is a key resources
the moon-base will require. Deposits of ice on the Moon would have many
practical aspects for future manned lunar exploration. Recent
discoveries confirm what planners had hoped, there is a lot of water on the moon.
The water is most abundant at the poles, especially in the form of ice in crater walls and bottoms which never see the sun.
Mining these ice deposits would save a lot of money. Shipping water to
the Moon from Earth would be extremely expensive ($2,000 to $20,000 per
kg). The lunar water could also serve as a source of oxygen and
hydrogen.
Oxygen is necessary for human life and both oxygen and hydrogen
are constituents of rocket fuel. By weight, moon rocks are 40 to 45%
oxygen. By heating the top meter of 1 acre of moon dust to 1300 degrees
Celsius, we extract 3000 to 3500 tons of oxygen. Extracting oxygen requires 450 calories of energy per kilogram of oxygen produced.
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| Proposed oxygen extraction process |
Recently,
scientists have significantly improved the oxygen extraction process from the lunar soil (regolith). You get a lot of oxygen plus the metal alloys with which it was bound. Both of these will be really useful on any future lunar bases
or colonies.
The processing was performed using a method called molten salt electrolysis. The regolith is placed in a mesh-lined basket. Calcium chloride - the
electrolyte - is added, and the mix is heated to around 950 degrees
Celsius, a temperature that doesn't melt the material. Then, an
electrical current is applied. This extracts the oxygen, and migrates
the salt to an anode, where it can be easily removed. The metal left behind is usable - the first time a lunar regolith oxygen extraction technique has produced this result.
Other Mining Products
By weight, in order of abundance, the chart to the right compares the percent of elements in lunar
soil with the Earth. As on Earth, these
percentages will differ depending on location.
The soil of the Moon, called lunar regolith by scientists, is a rich
source of metals and oxygen that can be strip mined. Silicon can be
used for solar panels and building construction material. Iron for construction, calcium for cement,
and magnesium for vehicles.
The lunar highlands are
filled with aluminum, a lightweight and sturdy material used in
buildings, aircraft, vehicles and medical devices.
Titanium can replace steel,
chromium and manganese for alloys. Strong and light titanium is found mainly in the mineral ilmenite, which also contains iron and
oxygen.
Sodium is used to make
caustic soda, important in many industries. Potassium and
nitrogen for agriculture, sulfur for acid and farming, carbon and
hydrogen for water and chemicals, and helium-3 for fusion energy.
The
regolith can be melted in solar furnaces and cast into forms to make
ceramic items. Glass, cement and concrete
can be produced. If we increase the temperature to 1500 degrees
Celsius, lunar soil will melt, allowing the extraction of various
minerals and other elements.
For the moon, the
amount of hydrogen in the soil is listed as PPM (parts per million) as
it is extremely important for human needs, but quite rare on the moon.
To get a single kilogram of Hydrogen, we would have to mine 25 tons of
lunar soil. Lunar soil contains very little of the other lighter
elements, necessary for biology, such as sulfur, carbon, and nitrogen.
They are still more abundant than hydrogen. Luckily, the discovery of
large sources of water ice at the poles significantly reduces the
problem.
Since about 100 million tons of regolith must be heated to about
1400 deg. F to get one ton of helium-3; 4000 tons of hydrogen; 2800
tons of helium-4. 10,000 tons of nitrogen; 20,000 tons of carbon and
54,000 tons of sulfur will also be obtained. Though helium-3 is scant in regolith, there’s still a
lot more in spots like the Sea of Tranquility than on Earth.
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| Robot guiding mining machine on Moon, Courtesy NASA |
Hydrogen and carbon do exist in amounts worth scavenging in the
upper layers of Lunar soil, put there by the incessant solar wind. From
Apollo samples we might expect every thousand tons of soil processed
to yield ( besides over 400 tons of oxygen ) one ton of hydrogen, 230
lbs. of carbon, and even 164 lbs. of nitrogen. This is hardly abundance
and not enough to support a lunar biosphere if the population on the
Moon grows to a considerable size. To satisfy lunar needs for rarer
elements (carbon and nitrogen) we may need to turn eventually to
carbonaceous chondrite asteroids in near earth orbit.
Exporting material to Earth is problematic due to the high cost of
transportation. One suggested candidate is helium-3 from the solar
wind, which may have accumulated on the Moon's surface over billions of
years. It may prove to be a desirable fuel in fusion reactors and is
rare on Earth. The abundance of helium-3 on the lunar surface and the
feasibility of its use in fusion power plants will need to be
established. China has made measurement of helium-3 abundance on the
lunar surface one of the goals of its exploration program.
Another export candidate might be rare earths. Fresh deposits of rare-earth elements (17 highly conductive metals
used in tech like hybrid car batteries and phones) are scarce on Earth.
In spots rich in potassium and phosphorus, the moon could host REE mines
on par with the best ones we have at home.
Power Generation
Solar Energy
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| Solar power facility, Courtesy NASA |
Solar energy is a strong candidate. It could prove to be a
relatively cheap source of power for a lunar base, especially since
many of the raw materials needed for solar panel production can be
extracted on site. However, the long lunar night (14 Earth days) is a
drawback for solar power on the Moon. This might be solved by building
several power plants, so that at least one of them is always in
daylight.
Another possibility could be to build such a power plant where
there is constant or near-constant sunlight. The Lunar poles contain a
number of such potential power generating locations. Possible
locations are Shackleton Crater or Malapert mountain near the lunar
south pole, or on the rim of Peary creater near the north pole.
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Near-permanent sunlit areas on the Moon shown using
Clementine
spacecraft images superimposed on a Lunar
South Pole radar image.
Credit: Arecibo Observatory |
The solar energy converters need not be silicon solar panels. It
may be more feasible to use the larger temperature difference between
sun and shade to run heat engine generators. Concentrated sunlight
could also be relayed via mirrors and used directly for lighting,
agriculture and process heat. The focused heat can also be employed in
materials processing to extract various elements from lunar surface
materials.
Although water would be found at the bottom of craters permanently
shadowed from the sun, near continuous sunlight for power generation
would require high topography to catch the sun. Specifically, the
requirement would be heights near the poles that catch sunlight more
than the 75% of the time. Given the power needs associated with water
extraction and lunar mining, creation of significant power sources on
the moon will be a high priority.
At the lunar poles, in addition to
permanently shadowed areas where water can be found, there are higher
areas such as crater rims which are permanently exposed to sunlight and could serve as a source of power. The south pole is a primary setting for such
peaks of eternal light.
Fuel cells
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| PEM fuel cell |
Fuel cells on the Space Shuttle have operated reliably for up to
17 days at a time. On the Moon, they would only be needed for 14.75
days - the length of the Lunar night. During the Lunar day, solar
panels (either photo voltaic or Solar Thermal) could be used as well as
providing the electricity necessary to convert the water ('waste' from
the fuel cells) back into hydrogen and oxygen ready for the next Lunar
night.
Current fuel cell technology is far more advanced than the
Shuttle's cells - PEM (Proton Exchange Membrane) cells produce
considerably less heat (requiring smaller, lighter radiators) and are
physically lighter - more economical to launch from Earth. NASA is now
actively examining its fuel cell options for future moon missions.
Nuclear Fission
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| Nuclear power facility, Courtesy NASA |
A nuclear fission reactor could possibly be able to fulfill some of the
need for power. The advantage it has against a fusion reactor is that
it is an already existing technology. Even if the fuel had to be
brought from earth, its low weight to energy generated ratio may make
it competitive with solar.
Nuclear Fusion
Helium-3 is a non-radioactive isotope of helium available in
significant quantities on the moon, but rare on Earth, which will
really give value to the Moon when fusion reactors that can burn the
stuff are developed. The Moon’s surface is covered with many meters of
regolith that stores low but ubiquitous concentrations of helium-3, an
isotope of helium that undergoes fusion reactions which may ultimately
be tapped for energy. The development of lunar helium-3 could also lead
to the development of fusion rocket propulsion systems, with long-term
implications for interplanetary missions in terms of reduced trip
times and associated reductions in astronaut exposure to weightlessness
and radiation in space. However, reliable, efficient fusion reactors
using helium-3 will first need to be developed.
Solar Power Satellites
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| Space-based Solar Power |
Gerald K. O'Neill pointed out that we have on the moon's
surface the materials we need to produce solar cells and other elements
to build solar power stations in Earth or Lunar orbit. Lunar soils contain 20
percent silicon for solar cells, and about 20 percent metals. Much of
the rest is oxygen. The moon has two other great advantages as a source
of materials: a weak gravitational grip and a vacuum environment. This
makes it practical to locate electric mass-drivers on its surface
which would be capable of lofting a steady stream of small payloads to a
precise collection point high in space where
solar power satellites could function.
Manufacturing
Obviously, mining of the lunar regolith could lead to the
manufacture of products containing the elements derived from the lunar
soil. Some products derived from mining include metals, chemicals,
solar panels, construction iron, concrete, glass, vehicles, and
agriculture materials. The moon would the ideal location for
manufacturing that requires a sterile, low-gravity environment in a
vacuum; research and processing of potentially dangerous life forms or
nanotechnology, and long-term storage of radioactive materials. Unique
products may be producible in the nearly limitless extreme vacuum of
the lunar surface, and these may support a high degree of lunar
settlement self-sufficiency. The Moon's remoteness is the ultimate
isolation for biologically hazardous experiments.
Agriculture
For self-sufficiency we will need to grow plants on the moon for
food, recycling, and replenishing the air. Many vegetables mature
within 60 days on earth. Given almost 30 earth days with 24 hours of
sunlight during a lunar day, lunar greenhouses should be able to
produce food for moonbase inhabitants and visitors.
Cultivation of plants for food can provide a basic diet for
astronauts as well as psychological benefits for people living for
years in cramped quarters. Some animals might also be taken for food.
The Moon can provide a laboratory for testing the viability of plants
and animals in the space environment, particularly the possibility of
multigenerational propagation of plants. Research could occur on the
possibility of obtaining the nutrients needed for healthy plant growth
from native moon materials. Some animal research dealing with the effects of
gravity might also be undertaken.
As shown in the graphic, agriculture produce would be
grown hydroponically or in soil during the lunar day. The plants could
be grown in tanks or raised beds located in excavated channels covered
with transparent skylights. The channel walls could provide insulation
from radiation and the great temperature changes during the day/night
cycle. Radiators could remove excess heat. An insulated moveable roof
could be rolled over the agriculture channel during the lunar night so
as to minimize heat loss during this coldest period on the moon.
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| Hydroponic plant growth |
Consideration should be given to growing plants in as reduced an
atmospheric pressure as possible. There are two reasons. First, it'll
help reduce the weight of the supplies that need to be lifted off the
earth. Even air has mass. Second, Martian and lunar greenhouses must
hold up in places where the outside atmospheric pressures are, at best, less
than one percent of Earth-normal. Those greenhouses will be easier to
construct, maintain and operate if their interior pressure is also very low --
perhaps only one-sixteenth of Earth normal.
Research will need to focus on
developing plants that can thrive in this low pressure environment. Such
low pressure agriculture research has already started.
The problem is, in such extreme low pressures, plants have to work
hard to survive. There's no reason for them to have learned to
favorably interpret the biochemical signals induced by low pressure. Low pressure
makes plants act as if they're drying out. There are also benefits to a
low pressure environment. In low pressure, not only water, but also
plant hormones are flushed from the plant more quickly. So a hormone,
for example, that causes plants to die of old age might move through
the organism before it takes effect.
Astronomy
Since
the Moon's days (about fourteen Earth days) have a dark sky, it allows
for nonstop astronomical observations. Disadvantages include
micrometeorite impacts, cosmic and solar
radiation, lunar dust, moon quakes, and temperature shifts as large as
350° Celsius. Regarding moon quakes, the tidal forces that the Earth exerts on the Moon are more than 20
times greater than the Moon's tidal forces on Earth, enough to cause the
Moon to experience considerable moon quakes.
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The moon's greatest advantage over space as a telescope site is that
it offers a stable platform. Small, remote-controlled reflecting
telescopes could be located at scattered locations. A number of small
telescopes, separated by hundreds or thousands of kilometers yet
exactly located relative to each other on the moon's stable platform,
could group together to form, in effect, a telescope hundreds or
thousands of kilometers across. This giant telescope could resolve
earth-like planets orbiting other stars. The telescopes could also
operate as individual instruments. they could even be controlled by
astronomers on Earth through the Internet.
The
International Lunar Observatory (ILO)
is a multi-national, multi-wavelength astrophysical observatory, power
station and communications center that is planned to be operational
near the South Pole on the lunar surface. The southern
hemisphere sky contains many objects interesting to astronomers,
including the Magellanic Clouds and the Galactic Core. The mission's objective is to conduct astrophysical observations from
the surface of the Moon, whose lack of atmosphere eliminates much of the
need for costly adaptive optics technology.
Radio Telescopes
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| Observatory with a radio telescope built into the lunar surface, Courtesy NASA |
GPS communications, microwave ovens, radar, cell phone and WiFi signals,
and even digital cameras are among the many terrestrial sources that
contaminate radio observatories. On the far side of the Moon, all of
humanity's sources of interference are 100% blocked. It is the most
pristine environment for radio astronomy available.
Signals of the early stages of the Big Bang, inflation, and the
formation of the first stars could be discovered and recorded with a
lunar radio
telescope. While this may be possible either on Earth or in
space, the lunar far side offers more sensitivity, due to being shielded
from Earth, than any other option.
The moon would be an excellent location for SETI (search for
extraterrestrial intelligence) activity. With a rarer vacuum, the view
would be clearer than near-earth orbital space. Raw materials abundant
on the moon, like silicon and aluminum, can be used in construction of
giant telescopes. The
farside is the best place in the solar
system for sensitive SETI radio searches. It is insulated by 3,500 feet
of rock and is always turned away from the earth and its myriad of
radio frequency sources. When the sun is down for the two week night,
there is no quieter radio environment.
Tourism
What would tourists do on the moon? Probably pretty much the same
things they do on earth - visit historical and scenic spots and
interesting cities. Historical places would be the Apollo landing sites
of 30 or more years ago. Scenic spots include great craters, high
cliffs, cracks the size of canyons, mountains and strange valleys.
There is also the farside of the moon. Interesting cities are in the
moon's potential future. Large, pressurized domes or caverns would
permit human-powered flight in the moon's light gravity, which may
result in new sports activities. The low gravity may find health uses
such as enabling the physically enfeebled to enjoy life in a
more rewarding environment.
Trial Run
The Moon can serve as a proving ground for a wide range of space
operations and processes. This includes learning to "live off the
land" (self-sufficiency) for human outposts on Mars and elsewhere in
the solar system as well as on the Moon itself.
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| A Future Objective - Mount Olympus Mons on Mars |
The outpost should
prioritize not only field-testing equipment destined for Mars, but
developing lunar building materials so that future outpost expansion
can rely on locally produced materials. Regolith element harvesting
techniques will be tested. Prototype solar collectors made wholly or
almost wholly from lunar materials could be created. With
ready sources of metal and a low gravity, the moon would enable the
building of large space vehicles with practically no limits on cargo
volume.
Technology
developed for a Lunar colony would likely have application to other
potential space venues, including near-Earth asteroids and Mercury,
which has many similarities to the Moon. A lunar outpost program must
include a program to establish the limitations of the human body for
long stays on the Moon and re-adaptation when returning to Earth. These
findings will be applicable to the human exploration of Mars.
