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1986 artist concept of a lunar colony
Colonization of the Moon is the proposed establishment of a permanent human community or robotic industries on the
Moon.
Discovery of
lunar water at the
lunar poles by
Chandrayaan-1
has renewed interest in the Moon. Locating such a colony at one of the
lunar poles would also avoid the problem of long lunar nights – about
354 hours long,
a little more than two weeks – and allow the colony to take advantage
of the continuous sunlight there for generating solar power.
Permanent human habitation on a planetary body other than the
Earth is one of science fiction's most prevalent themes. As technology
has advanced, and concerns about the
future of humanity on Earth have increased, the vision of
space colonization as an achievable and worthwhile goal has gained momentum.
Because of its proximity to Earth, the Moon is seen as the best and
most obvious location for the first permanent off-planet colony.
Currently, the main problem hindering the development of such a colony
is the high cost of spaceflight.
There are also several projects that have been proposed for the near future by
space tourism startup companies for
tourism on the Moon.
Proposals
Concept art from NASA showing astronauts entering a lunar outpost
The notion of a lunar colony originated before the
Space Age. In 1638 Bishop
John Wilkins wrote
A Discourse Concerning a New World and Another Planet, in which he predicted a human colony on the Moon.
Konstantin Tsiolkovsky (1857–1935), among others, also suggested such a step. From the 1950s onwards, a number of concepts and designs have been suggested by scientists, engineers and others.
In 1954, science-fiction writer
Arthur C. Clarke proposed a lunar base of inflatable modules covered in lunar dust for insulation. A spaceship, assembled in
low Earth orbit, would launch to the Moon, and astronauts would set up the
igloo-like modules and an inflatable
radio mast. Subsequent steps would include the establishment of a larger, permanent dome; an
algae-based
air purifier; a
nuclear reactor for the provision of power; and
electromagnetic cannons to launch
cargo and
fuel to interplanetary vessels in space.
In 1959,
John S. Rinehart
suggested that the safest design would be a structure that could
"[float] in a stationary ocean of dust", since there were, at the time
this concept was outlined, theories that there could be mile-deep dust
oceans on the Moon.
[11] The proposed design consisted of a half-cylinder with half-domes at both ends, with a
micrometeoroid shield placed above the base.
Project Horizon
Project Horizon was a 1959 study regarding the
United States Army's plan to establish a fort on the Moon by 1967.
Heinz-Hermann Koelle, a German rocket engineer of the
Army Ballistic Missile Agency
(ABMA) led the Project Horizon study. It was proposed that the first
landing would be carried out by two "soldier-astronauts" in 1965 and
that more construction workers would soon follow. It was posited that
through numerous launches (61
Saturn Is and 88
Saturn C-2s), 245 tons of cargo could be transported to the outpost by 1966.
Lunex Project
Lunex Project was a
US Air Force plan for a manned lunar landing prior to the
Apollo Program in 1961. It envisaged a 21-airman underground Air Force base on the Moon by 1968 at a total cost of $7.5 billion.
Sub-surface base
In 1962,
John DeNike and
Stanley Zahn published their idea of a sub-surface base located at the
Sea of Tranquility. This base would house a crew of 21, in modules placed four meters below the surface, which was believed to provide
radiation shielding on par with Earth's atmosphere. DeNike and Zahn favored
nuclear reactors for energy production, because they were more efficient than
solar panels, and would also overcome the problems with the long lunar nights. For the life support system, an algae-based
gas exchanger was proposed.
Recent proposals
In 2007, Jim Burke, of the
International Space University
in France, said people should plan to preserve humanity's culture in
the event of a civilization-stopping asteroid impact with Earth. A Lunar
Noah's Ark was proposed. Subsequent planning may be taken up by the
International Lunar Exploration Working Group (ILEWG).
In 2016, Johann-Dietrich Wörner, the Chief of
ESA, proposed the
International Moon Village as a non-governmental organization (NGO), and in November 2017, the
Moon Village Association was created.
This organization aims to promote international discussions to foster
the implementation of a permanent human settlement near the lunar south
pole.
Moon exploration
Exploration through 2017
Exploration of the lunar surface by spacecraft began in 1959 with the
Soviet Union's
Luna program.
Luna 1 missed the Moon, but
Luna 2
made a hard landing (impact) into its surface, and became the first
artificial object on an extraterrestrial body. The same year, the
Luna 3 mission radioed photographs to Earth of the Moon's hitherto unseen
far side, marking the beginning of a decade-long series of robotic lunar explorations.
Responding to the Soviet program of space exploration, US President
John F. Kennedy in 1961 told the
US Congress
on May 25: "I believe that this nation should commit itself to
achieving the goal, before this decade is out, of landing a man on the
Moon and returning him safely to the Earth." The same year the Soviet
leadership made some of its first public pronouncements about landing a
man on the Moon and establishing a lunar base.
Crewed exploration of the lunar surface began in 1968 when the
Apollo 8 spacecraft orbited the Moon with three astronauts on board. This was mankind's first direct view of the far side. The following year, the
Apollo 11 Apollo Lunar Module
landed two astronauts on the Moon, proving the ability of humans to
travel to the Moon, perform scientific research work there, and bring
back sample materials.
Additional missions to the Moon continued this exploration phase. In 1969, the
Apollo 12 mission landed next to the
Surveyor 3
spacecraft, demonstrating precision landing capability. The use of a
manned vehicle on the Moon's surface was demonstrated in 1971 with the
Lunar Rover during
Apollo 15.
Apollo 16 made the first landing within the rugged
lunar highlands. However, interest in further exploration of the Moon was beginning to wane among the American public. In 1972,
Apollo 17 was the final Apollo lunar mission, and further planned missions were scrapped at the directive of President
Nixon. Instead, focus was turned to the
Space Shuttle and crewed missions in near Earth orbit.
In addition to its scientific returns, the Apollo program also
provided valuable lessons about living and working in the lunar
environment.
The
Soviet manned lunar programs failed to send a manned mission to the Moon. However, in 1966
Luna 9 was the first probe to achieve a soft landing and return close-up shots of the lunar surface.
Luna 16 in 1970 returned the first Soviet lunar soil samples, while in 1970 and 1973 during the
Lunokhod program two robotic rovers landed on the Moon.
Lunokhod 1 explored the lunar surface for 322 days, and
Lunokhod 2
operated on the Moon about four months only but covered a third more
distance. 1974 saw the end of the Soviet Moonshot, two years after the
last American manned landing. Besides the manned landings, an abandoned
Soviet moon program included building the moonbase "
Zvezda", which was the first detailed project with developed mockups of expedition vehicles and surface modules.
In the decades following, interest in exploring the Moon faded
considerably, and only a few dedicated enthusiasts supported a return.
However, evidence of
lunar ice at the poles gathered by NASA's
Clementine (1994) and
Lunar Prospector (1998) missions rekindled some discussion, as did the potential growth of a
Chinese space program that contemplated its own mission to the Moon. Subsequent research suggested that there was far less ice present (if
any) than had originally been thought, but that there may still be some
usable deposits of hydrogen in other forms. However, in September 2009, the
Chandrayaan probe of India, carrying an
ISRO instrument, discovered that the
lunar soil contains 0.1% water by weight, overturning hypotheses that had stood for 40 years.
In 2004,
US President George W. Bush called for a
plan to return crewed missions to the Moon by 2020 (since cancelled – see
Constellation program). On June 18, 2009, NASA's
LCROSS/
LRO
mission to the moon was launched. The LCROSS mission was designed to
acquire research information to assist with future lunar exploratory
missions and was scheduled to conclude with a controlled collision of
the craft on the lunar surface. LCROSS's mission concluded as scheduled with its controlled impact on October 9, 2009.
In 2010, due to reduced congressional NASA appropriations, President
Barack Obama
halted the Bush administration's earlier lunar exploration initiative
and directed a generic focus on crewed missions to asteroids and Mars,
as well as extending support for the International Space Station.
Planned crewed lunar missions 2021 - 2036
As
of 2016, Russia is planning to begin building a human colony on the
moon by 2030. Initially, the Moon base would be crewed by no more than 4
people, with their number later rising to maximum of 12 people. Japan also has plans to land a man on the moon by 2030, while the
People's Republic of China is currently planning to land a human on the Moon by 2036 (see
Chinese Lunar Exploration Program).
The United States currently (2017) has plans to send a crewed space mission to orbit (but not to land on) the Moon in 2021.
While the US Trump administration has called for a return of crewed
missions to the Moon, it has currently (2018) not authorized any funding
for any such lunar missions in the next 20 years. The current
administration has focused funding on Mars missions. What President Trump requests is the development of a lunar orbiting station called
Lunar Orbital Platform-Gateway. A stated goal of aerospace company
SpaceX is to enable the creation of a colony on the Moon using its upcoming
BFR launch system. Billionaire Jeff Bezos has outlined his plans for a lunar base in the next decade.
Lunar water ice
Play media
Beginning
with a full-frame Moon in this video, the camera flies to the lunar
south pole and shows areas of permanent shadow. Realistic shadows evolve
through several months.
On 24 September 2009,
Science magazine reported that the
Moon Mineralogy Mapper (M
3) on the
Indian Space Research Organization's (ISRO)
Chandrayaan-1 had detected water on the Moon.
M
3 detected absorption features near 2.8–3.0 μm
(0.00011–0.00012 in) on the surface of the Moon. For silicate bodies,
such features are typically attributed to
hydroxyl- and/or
water-bearing
materials. On the Moon, the feature is seen as a widely distributed
absorption that appears strongest at cooler high latitudes and at
several fresh
feldspathic craters. The general lack of correlation of this feature in sunlit M
3 data with neutron spectrometer H abundance data suggests that the formation and retention of OH and H
2O is an ongoing surficial process. OH/H
2O
production processes may feed polar cold traps and make the lunar
regolith a candidate source of volatiles for human exploration.
The Moon Mineralogy Mapper (M
3), an imaging
spectrometer, was one of the 11 instruments on board Chandrayaan-1,
whose mission came to a premature end on 29 August 2009. M
3 was aimed at providing the first mineral map of the entire lunar surface.
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."
On November 13, 2009, NASA announced that the
LCROSS mission had discovered large quantities of water ice on the Moon around the LCROSS impact site at
Cabeus.
Robert Zubrin, president of the
Mars Society,
relativized the term 'large': "The 30 m crater ejected by the probe
contained 10 million kilograms of regolith. Within this ejecta, an
estimated 100 kg of water was detected. That represents a proportion of
ten parts per million, which is a lower water concentration than that
found in the soil of the driest deserts of the Earth. In contrast, we
have found continent sized regions on Mars, which are 600,000 parts per
million, or 60% water by weight."
Although the Moon is very dry on the whole, the spot where the LCROSS
impactor hit was chosen for a high concentration of water ice. Dr.
Zubrin's computations are not a sound basis for estimating the
percentage of water in the regolith at that site. Researchers with
expertise in that area estimated that the regolith at the impact site
contained 5.6 ± 2.9% water ice, and also noted the presence of other
volatile substances. Hydrocarbons, material containing sulfur, carbon
dioxide, carbon monoxide, methane and ammonia were present.
In March 2010, NASA reported that the findings of its mini-SAR
radar aboard Chandrayaan-1 were consistent with ice deposits at the
Moon's north pole. 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.
In March 2014, researchers who had previously published reports
on possible abundance of water on the Moon, reported new findings that
refined their predictions substantially lower.
In 2018, it was announced that M
3 infrared data from
Chandrayaan-1 had been re-analyzed to confirm the existence of water
across wide expanses of the Moon's polar regions.
Advantages and disadvantages
Placing a colony on a natural body would provide an ample source of
material for construction and other uses in space, including shielding
from
cosmic radiation.
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
source of construction materials within cis-lunar space. Rockets
launched from the Moon would require less locally produced propellant
than rockets launched from Earth. 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 advantages:
- A lunar base could be a site for launching rockets with locally
manufactured fuel to distant planets such as Mars. Launching rockets
from the Moon would be easier than from Earth because the Moon's gravity
is lower, requiring a lower escape velocity.
A lower escape velocity would require less propellant, but there is no
guarantee that less propellant would cost less money than that required
to launch from Earth. Asteroid mining,
however, may prove useful in lowering various costs accrued during the
construction and management of a lunar base and its activities.
- The energy required to send objects from Earth to the Moon is lower than for most other bodies.
- 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.
- If a long-term base were to be built on the Moon, the exposure would
show the effects of low gravity on humans over an extended period of
time. Those results could likely inform the viability of attempting a
long-term base or a Mars colony.
- 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 to forty minutes. This,
again, could be particularly valuable in an early colony, where
life-threatening problems requiring Earth's assistance could occur.
- 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.
- Building observatory facilities on the Moon from lunar materials
allows many of the benefits of space based facilities without the need
to launch these into space. The lunar soil, although it poses a problem for any moving parts of telescopes, can be mixed with carbon nanotubes and epoxies in the construction of mirrors up to 50 meters in diameter. It is relatively nearby; astronomical seeing is not a concern; certain craters near the poles are permanently dark and cold, and thus especially useful for infrared telescopes; and radio telescopes on the far side would be shielded from the radio chatter of Earth. A lunar zenith telescope can be made cheaply with ionic liquid.
- A farm at the lunar north pole could provide eight hours of sunlight
per day during the local summer by rotating crops in and out of the
sunlight which is continuous for the entire summer. A beneficial
temperature, radiation protection, insects for pollination, and all
other plant needs could be artificially provided during the local summer
for a cost. One estimate suggested a 0.5 hectare space farm could feed 100 people.
There are several disadvantages to the Moon as a colony site:
- The long lunar night would impede reliance on solar power and
require that a colony exposed to the sunlit equatorial surface be
designed to withstand large temperature extremes (about 95 K (−178.2 °C)
to about 400 K (127 °C)). An exception to this restriction are the
so-called "peaks of eternal light" located at the lunar north pole that are constantly bathed in sunlight. The rim of Shackleton Crater,
towards the lunar south pole, also has a near-constant solar
illumination. Other areas near the poles that get light most of the time
could be linked in a power grid. The temperature 1 meter below the
surface of the Moon is estimated to be near constant over the period of a
month varying with latitude from near 220 K (−53 °C) at the equator to
near 150 K (−123 °C) at the poles.
- The Moon is highly depleted in volatile elements, such as nitrogen and hydrogen. Carbon, which forms volatile oxides, is also depleted. A number of robot probes including Lunar Prospector
gathered evidence of hydrogen generally in the Moon's crust consistent
with what would be expected from solar wind, and higher concentrations
near the poles. There had been some disagreement whether the hydrogen must necessarily be in the form of water. The 2009 mission of the Lunar Crater Observation and Sensing Satellite (LCROSS) proved that there is water on the Moon. This water exists in ice form perhaps mixed in small crystals in the regolith
in a colder landscape than people have ever mined. Other volatiles
containing carbon and nitrogen were found in the same cold trap as ice.
If no sufficient means is found for recovering these volatiles on the
Moon, they would need to be imported from some other source to support
life and industrial processes. Volatiles would need to be stringently
recycled. This would limit the colony's rate of growth and keep it
dependent on imports. The transportation cost of importing volatiles
from Earth could be reduced by constructing the upper stage of supply
ships using materials high in volatiles, such as carbon fiber and plastics. The 2006 announcement by the Keck Observatory that the binary Trojan asteroid 617 Patroclus, and possibly large numbers of other Trojan objects in Jupiter's
orbit, are likely composed of water ice, with a layer of dust, and the
hypothesized large amounts of water ice on the closer, main-belt
asteroid 1 Ceres, suggest that importing volatiles from this region via the Interplanetary Transport Network
may be practical in the not-so-distant future. However, these
possibilities are dependent on complicated and expensive resource
utilization from the mid to outer Solar System, which is not likely to
become available to a Moon colony for a significant period of time.
- It is uncertain whether the low (~ one-sixth g) gravity on the Moon is strong enough to prevent detrimental effects to human health in the long term. Exposure to weightlessness
over month-long periods has been demonstrated to cause deterioration of
physiological systems, such as loss of bone and muscle mass and a
depressed immune system. Similar effects could occur in a low-gravity
environment, although virtually all research into the health effects of
low gravity has been limited to micro gravity.
- The lack of a substantial atmosphere for insulation results in temperature extremes and makes the Moon's surface conditions somewhat like a deep space vacuum.
It also leaves the lunar surface exposed to half as much radiation as
in interplanetary space (with the other half blocked by the Moon itself
underneath the colony), raising the issues of the health threat from cosmic rays and the risk of proton exposure from the solar wind. Lunar rubble can protect living quarters from cosmic rays. Shielding against solar flares during expeditions outside is more problematic.
- When the Moon passes through the magnetotail of the Earth, the plasma sheet
whips across its surface. Electrons crash into the Moon and are
released again by UV photons on the day side but build up voltages on
the dark side. This causes a negative charge build up from −200 V to −1000 V. See Magnetic field of the Moon.
- The lack of an atmosphere increases the chances of the colony's
being hit by meteors. Even small pebbles and dust (micrometeoroids) have
the potential to damage or destroy insufficiently protected structures.
- Moon dust
is an extremely abrasive glassy substance formed by micrometeorites and
unrounded due to the lack of weathering. It sticks to everything, can
damage equipment, and it may be toxic. Since it is bombarded by charged
particles in the solar wind, it is highly ionized, and is extremely
harmful when breathed in. During the 1960s and 70s Apollo missions,
astronauts were subject to respiratory problems on return flights from
the Moon, for this reason.
- Growing crops on the Moon faces many difficult challenges due to the
long lunar night (354 hours), extreme variation in surface temperature,
exposure to solar flares, nitrogen-poor soil, and lack of insects for
pollination. Due to the lack of any atmosphere on the Moon, plants would
need to be grown in sealed chambers, though experiments have shown that
plants can thrive at pressures much lower than those on Earth.
The use of electric lighting to compensate for the 354-hour night might
be difficult: a single acre of plants on Earth enjoys a peak
4 megawatts of sunlight power at noon. Experiments conducted by the Soviet space program in the 1970s suggest it is possible to grow conventional crops with the 354-hour light, 354-hour dark cycle. A variety of concepts for lunar agriculture have been proposed,
including the use of minimal artificial light to maintain plants during
the night and the use of fast-growing crops that might be started as
seedlings with artificial light and be harvestable at the end of one
lunar day.
- One of the less obvious difficulties lies not with the Moon itself
but rather with the political and national interests of the nations
engaged in colonization. Assuming that colonization efforts were able to
overcome the difficulties outlined above – there would likely be issues
regarding the rights of nations and their colonies to exploit resources
on the lunar surface, to stake territorial claims and other issues of
sovereignty which would have to be agreed upon before one or more
nations established a permanent presence on the Moon. The ongoing
negotiations and debate regarding the Antarctic
is a good case study for prospective lunar colonization efforts in that
it highlights the numerous pitfalls of developing/inhabiting a location
that is subject to the claims of multiple sovereign nations.
Locations
Russian
astronomer Vladislav V. Shevchenko proposed in 1988 the following three criteria that a lunar outpost should meet:
- good conditions for transport operations;
- a great number of different types of natural objects and features on the Moon of scientific interest; and
- natural resources, such as oxygen. The abundance of certain minerals, such as iron oxide, varies dramatically over the lunar surface.
While a colony might be located anywhere, potential locations for a lunar colony fall into three broad categories.
Polar regions
There are two reasons why the
north pole and
south pole
of the Moon might be attractive locations for a human colony. First,
there is evidence for the presence of water in some continuously shaded
areas near the poles. Second, the Moon's
axis of rotation is sufficiently close to being perpendicular to the
ecliptic plane that the radius of the Moon's
polar circles
is less than 50 km. Power collection stations could therefore be
plausibly located so that at least one is exposed to sunlight at all
times, thus making it possible to power polar colonies almost
exclusively with solar energy. Solar power would be unavailable only
during a
lunar eclipse,
but these events are relatively brief and absolutely predictable. Any
such colony would therefore require a reserve energy supply that could
temporarily sustain a colony during lunar eclipses or in the event of
any incident or malfunction affecting solar power collection. Hydrogen
fuel cells
would be ideal for this purpose, since the hydrogen needed could be
sourced locally using the Moon's polar water and surplus solar power.
Moreover, due to the Moon's uneven surface some sites have nearly
continuous sunlight. For example,
Malapert mountain, located near the
Shackleton crater at the lunar south pole, offers several advantages as a site:
- It is exposed to the Sun most of the time; two closely spaced arrays of solar panels would receive nearly continuous power.
- Its proximity to Shackleton Crater (116 km, or 69.8 mi) means that
it could provide power and communications to the crater. This crater is
potentially valuable for astronomical observation. An infrared instrument would benefit from the very low temperatures. A radio telescope would benefit from being shielded from Earth's broad spectrum radio interference.
- The nearby Shoemaker and other craters are in constant deep shadow, and might contain valuable concentrations of hydrogen and other volatiles.
- At around 5,000 meters (16,000 feet) elevation, it offers line of sight communications over a large area of the Moon, as well as to Earth.
- The South Pole-Aitken basin
is located at the lunar south pole. This is the second largest known
impact basin in the Solar System, as well as the oldest and biggest
impact feature on the Moon, and should provide geologists access to deeper layers of the Moon's crust.
NASA chose to use a south-polar site for the lunar outpost reference design in the
Exploration Systems Architecture Study chapter on lunar architecture.
At the north pole, the rim of
Peary Crater has been proposed as a favorable location for a base. Examination of images from the
Clementine mission appear to show that parts of the crater rim are permanently illuminated by sunlight (except during
lunar eclipses). As a result, the temperature conditions are expected to remain very stable at this location, averaging −50 °C (−58 °F). This is comparable to winter conditions in Earth's
Poles of Cold in
Siberia and
Antarctica. The interior of Peary Crater may also harbor hydrogen deposits.
A 1994 bistatic radar experiment performed during the Clementine mission suggested the presence of water ice around the south pole. The
Lunar Prospector spacecraft reported in 2008 enhanced hydrogen abundances at the south pole and even more at the north pole. On the other hand, results reported using the
Arecibo radio telescope
have been interpreted by some to indicate that the anomalous Clementine
radar signatures are not indicative of ice, but surface roughness. This interpretation, however, is not universally agreed upon.
A potential limitation of the polar regions is that the inflow of
solar wind
can create an electrical charge on the leeward side of crater rims. The
resulting voltage difference can affect electrical equipment, change
surface chemistry, erode surfaces and levitate lunar dust.
Equatorial regions
The lunar equatorial regions are likely to have higher concentrations of
helium-3 (rare on Earth but much sought after for use in nuclear fusion research) because the
solar wind has a higher
angle of incidence.
They also enjoy an advantage in extra-Lunar traffic: The rotation
advantage for launching material is slight due to the Moon's slow
rotation, but the corresponding orbit coincides with the ecliptic,
nearly coincides with the lunar orbit around Earth, and nearly coincides
with the equatorial plane of Earth.
Several probes have landed in the
Oceanus Procellarum area. There are many areas and features that could be subject to long-term study, such as the
Reiner Gamma anomaly and the dark-floored
Grimaldi crater.
Far side
The
lunar far side lacks direct communication with Earth, though a
communication satellite at the
L2 Lagrangian point, or a network of orbiting satellites, could enable communication between the far side of the Moon and Earth. The far side is also a good location for a large radio telescope because it is well shielded from the Earth. Due to the lack of atmosphere, the location is also suitable for an array of
optical telescopes, similar to the
Very Large Telescope in
Chile. To date, there has been no ground exploration of the far side.
Scientists have estimated that the highest concentrations of helium-3 can be found in the
maria on the far side, as well as near side areas containing concentrations of the
titanium-based
mineral ilmenite.
On the near side the Earth and its magnetic field partially shields the
surface from the solar wind during each orbit. But the far side is
fully exposed, and thus should receive a somewhat greater proportion of
the ion stream.
Lunar lava tubes
High Sun view of a 100 meter deep lunar pit crater that may provide access to a lava tube
Lunar lava tubes
are a potential location for constructing a lunar base. Any intact lava
tube on the Moon could serve as a shelter from the severe environment
of the lunar surface, with its frequent meteorite impacts, high-energy
ultra-violet radiation and energetic particles, and extreme diurnal
temperature variations. Lava tubes provide ideal positions for shelter
because of their access to nearby resources. They also have proven
themselves as a reliable structure, having withstood the test of time
for billions of years.
An underground colony would escape the extreme of temperature on
the Moon's surface. The average temperature on the surface of the Moon
is about −5 °C. The day period (about 354 hours) has an average
temperature of about 107 °C (225 °F), although it can rise as high as
123 °C (253 °F). The night period (also 354 hours) has an average
temperature of about −153 °C (−243 °F). Underground, both periods would be around −23 °C (−9 °F), and humans could install ordinary heaters.
One such lava tube was discovered in early 2009.
Structure
Habitat
There
have been numerous proposals regarding habitat modules. The designs
have evolved throughout the years as mankind's knowledge about the Moon
has grown, and as the technological possibilities have changed. The
proposed habitats range from the actual spacecraft landers or their used
fuel tanks, to inflatable modules of various shapes. Some hazards of
the lunar environment such as sharp temperature shifts, lack of
atmosphere or magnetic field (which means higher levels of radiation and
micrometeoroids) and long nights, were unknown early on. Proposals have
shifted as these hazards were recognized and taken into consideration.
Underground colonies
Some
suggest building the lunar colony underground, which would give
protection from radiation and micrometeoroids. This would also greatly
reduce the risk of air leakage, as the colony would be fully sealed from
the outside except for a few exits to the surface.
The construction of an underground base would probably be more
complex; one of the first machines from Earth might be a
remote-controlled excavating machine. Once created, some sort of
hardening would be necessary to avoid collapse, possibly a
spray-on concrete-like substance made from available materials. A more porous insulating material also made
in-situ
could then be applied. Rowley & Neudecker have suggested
"melt-as-you-go" machines that would leave glassy internal surfaces.
Mining methods such as the
room and pillar might also be used. Inflatable self-sealing fabric habitats might then be put in place to retain air. Eventually an
underground city can be constructed. Farms set up underground would need
artificial sunlight. As an alternative to excavating, a
lava tube could be covered and insulated, thus solving the problem of radiation exposure.
An alternative solution is studied in Europe by students to excavate a habitat in the ice-filled craters of the moon.
Surface colonies
Variant for habitat creation on the surface or over lava tube
A possibly easier solution would be to build the lunar base on the surface, and cover the modules with lunar soil. The
lunar soil is composed of a unique blend of
silica and iron-containing compounds that may be fused into a glass-like solid using microwave energy.
Blacic has studied the mechanical properties of lunar glass and has
shown that it is a promising material for making rigid structures, if
coated with metal to keep moisture out.
This may allow for the use of "lunar bricks" in structural designs, or
the vitrification of loose dirt to form a hard, ceramic crust.
A lunar base built on the surface would need to be protected by
improved radiation and micrometeoroid shielding. Building the lunar base
inside a deep crater would provide at least partial shielding against
radiation and micrometeoroids.
Artificial magnetic fields have been proposed as a means to provide radiation shielding for long range deep space
crewed missions, and it might be possible to use similar technology on a
lunar colony. Some regions on the Moon possess strong local magnetic
fields that might partially mitigate exposure to charged solar and
galactic particles.
In a turn from the usual engineer-designed lunar habitats,
London-based
Foster + Partners architectural firm proposed a
building construction 3D-printer technology in January 2013 that would use lunar regolith raw materials to produce lunar building structures while using
enclosed inflatable habitats
for housing the human occupants inside the hard-shell lunar structures.
Overall, these habitats would require only ten percent of the structure
mass to be
transported from Earth, while using local lunar materials for the other 90 percent of the structure mass.
"Printed" lunar soil would provide both "
radiation and
temperature
insulation. Inside, a lightweight pressurized inflatable with the same
dome shape would be the living environment for the first human Moon
settlers."
The building technology would include mixing lunar material with
magnesium oxide,
which would turn the "moonstuff into a pulp that can be sprayed to form
the block" when a binding salt is applied that "converts [this]
material into a stone-like solid."
Terrestrial versions of this 3D-printing building technology are already
printing 2 metres (6 ft 7 in) of building material per hour with the
next-generation printers capable of 3.5 metres (11 ft) per hour,
sufficient to complete a building in a week.
Moon Capital
In
2010, The Moon Capital Competition offered a prize for a design of a
lunar habitat intended to be an underground international commercial
center capable of supporting a residential staff of 60 people and their
families. The Moon Capital is intended to be self-sufficient with
respect to food and other material required for life support. Prize
money was provided primarily by the
Boston Society of Architects,
Google Lunar X Prize and The New England Council of the
American Institute of Aeronautics and Astronautics.
3D printed structures
On January 31, 2013, the
ESA working with an independent architectural firm, tested a
3D-printed structure that could be constructed of lunar
regolith for use as a Moon base.
Energy
Nuclear power
A nuclear
fission reactor might fulfill most of a Moon base's power requirements.
With the help of fission reactors, one could overcome the difficulty of
the 354 hour lunar night. According to NASA, a nuclear fission power
station could generate a steady 40 kilowatts, equivalent to the demand
of about eight houses on Earth.
An artist's concept of such a station published by NASA envisages the
reactor being buried below the Moon's surface to shield it from its
surroundings; out from a tower-like generator part reaching above the
surface over the reactor, radiators would extend into space to send away
any heat energy that may be left over.
Radioisotope thermoelectric generators could be used as backup and emergency power sources for solar powered colonies.
One specific development program in the 2000s was the Fission Surface Power (FSP) project of
NASA and
DOE, a
fission power system
focused on "developing and demonstrating a nominal 40 kWe power system
to support human exploration missions. The FSP system concept uses
conventional
low-temperature stainless steel,
liquid metal-cooled reactor technology coupled with
Stirling power conversion." As of 2010,
significant component hardware testing had been successfully completed,
and a non-nuclear system demonstration test was being fabricated.
Helium-3 mining could be used to provide a substitute for
tritium for potential production of
fusion power in the future.
Solar energy
Solar energy is a possible source of power for a lunar base. Many of
the raw materials needed for solar panel production can be extracted on
site. However, the long lunar night (354 hours or 14.75 Earth days) is a
drawback for solar power on the Moon's surface. This might be solved by
building several power plants, so that at least one of them is always
in daylight. Another possibility would be to build such a power plant
where there is constant or near-constant sunlight, such as at the
Malapert mountain near the lunar south pole, or on the rim of
Peary crater
near the north pole. Since lunar regolith contains structural metals
like iron and aluminum, solar panels could be mounted high up on
locally-built towers that might rotate to follow the sun. A third
possibility would be to
leave the panels in orbit, and beam the power down as microwaves.
The solar energy converters need not be
silicon solar panels. It may be more advantageous 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 in
Stirling engines or
solar trough
generators, or it could be used directly for lighting, agriculture and
process heat. The focused heat might also be employed in materials
processing to extract various elements from lunar surface materials.
Energy storage
Fuel cells on the
Space Shuttle have operated reliably for up to 17 Earth days at a time. On the Moon, they would only be needed for 354 hours (14
3⁄4
days) – the length of the lunar night. Fuel cells produce water
directly as a waste product. Current fuel cell technology is more
advanced than the Shuttle's cells –
PEM (Proton Exchange Membrane) cells
produce considerably less heat (though their waste heat would likely be
useful during the lunar night) and are lighter, not to mention the
reduced mass of the smaller heat-dissipating radiators. This makes PEMs
more economical to launch from Earth than the shuttle's cells. PEMs have
not yet been proven in space.
Combining fuel cells with electrolysis would provide a
"perpetual" source of electricity – solar energy could be used to
provide power during the lunar day, and fuel cells at night. During the
lunar day, solar energy would also be used to electrolyze the water
created in the fuel cells – although there would be small losses of
gases that would have to be replaced.
Even if lunar colonies could provide themselves access to a
near-continuous source of solar energy, they would still need to
maintain fuel cells or an alternate energy storage system to sustain
themselves during lunar eclipses and emergency situations.
Transport
Earth to Moon
Conventional
rockets have been used for most lunar explorations to date. The ESA's
SMART-1 mission from 2003 to 2006 used conventional chemical rockets to reach orbit and
Hall effect thrusters to arrive at the Moon in 13 months. NASA would have used chemical rockets on its
Ares V booster and
Lunar Surface Access Module,
that were being developed for a planned return to the Moon around 2019,
but this was cancelled. The construction workers, location finders, and
other astronauts vital to building, would have been taken four at a
time in NASA's
Orion spacecraft.
Proposed concepts of Earth-Moon transportation are
Space elevators.
On the surface
A lunar rover being unloaded from a cargo spacecraft. Conceptual drawing
Lunar colonists would need the ability to transport cargo and people
to and from modules and spacecraft, and to carry out scientific study of
a larger area of the lunar surface for long periods of time. Proposed
concepts include a variety of vehicle designs, from small open rovers to
large pressurized modules with lab equipment, and also a few flying or
hopping vehicles.
Rovers could be useful if the terrain is not too steep or hilly.
The only rovers to have operated on the surface of the Moon (as of 2008) are the three Apollo
Lunar Roving Vehicles (LRV), developed by
Boeing, the two robotic Soviet
Lunokhods and the Chinese Yutu rover in 2013. The LRV was an open rover for a crew of two, and a range of 92 km during one
lunar day. One
NASA study resulted in the
Mobile Lunar Laboratory
concept, a crewed pressurized rover for a crew of two, with a range of
396 km. The Soviet Union developed different rover concepts in the
Lunokhod series and the L5 for possible use on future crewed missions to
the Moon or Mars. These rover designs were all pressurized for longer
sorties.
If multiple bases were established on the lunar surface, they
could be linked together by permanent railway systems. Both conventional
and
magnetic levitation (
Maglev)
systems have been proposed for the transport lines. Mag-Lev systems are
particularly attractive as there is no atmosphere on the surface to
slow down the
train, so the vehicles could achieve velocities comparable to
aircraft
on the Earth. One significant difference with lunar trains, however, is
that the cars would need to be individually sealed and possess their
own life support systems.
For difficult areas, a flying vehicle may be more suitable.
Bell Aerosystems proposed their design for the
Lunar Flying Vehicle as part of a study for NASA, while Bell proposes the Manned Flying System, a similar concept.
Surface to space
Launch technology
A lunar base with a mass driver (the long structure that goes toward the horizon). NASA conceptual illustration
Experience so far indicates that launching human beings into space is much more expensive than launching cargo.
One way to get materials and products from the Moon to an interplanetary way station might be with a
mass driver, a magnetically accelerated projectile launcher. Cargo would be picked up from orbit or an Earth-Moon
Lagrangian point by a shuttle craft using
ion propulsion,
solar sails or other means and delivered to Earth orbit or other destinations such as near-Earth asteroids,
Mars or other planets, perhaps using the
Interplanetary Transport Network.
A
lunar space elevator could transport people, raw materials and products to and from an
orbital station at Lagrangian points
L1 or
L2. Chemical rockets would take a payload from Earth to the
L1 lunar Lagrange location. From there a tether would slowly lower the payload to a soft landing on the lunar surface.
Other possibilities include a
momentum exchange tether system.
Launch costs
- Estimates
of the cost per unit mass of launching cargo or people from the Moon
vary and the cost impacts of future technological improvements are
difficult to predict. An upper bound on the cost of launching material
from the Moon might be about $40,000,000 per kilogram, based on dividing
the Apollo program costs by the amount of material returned.
At the other extreme, the incremental cost of launching material from
the Moon using an electromagnetic accelerator could be quite low. The
efficiency of launching material from the Moon with a proposed electric
accelerator is suggested to be about 50%.
If the carriage of a mass driver weighs the same as the cargo, two
kilograms must be accelerated to orbital velocity for each kilogram put
into orbit. The overall system efficiency would then drop to 25%. So 1.4
kilowatt-hours would be needed to launch an incremental kilogram of
cargo to low orbit from the Moon.
At $0.1/kilowatt-hour, a typical cost for electrical power on Earth,
that amounts to $0.16 for the energy to launch a kilogram of cargo into
orbit. For the actual cost of an operating system, energy loss for power
conditioning, the cost of radiating waste heat, the cost of maintaining
all systems, and the interest cost of the capital investment are
considerations.
- Passengers cannot be divided into the parcel size suggested for the
cargo of a mass driver, nor subjected to hundreds of gravities
acceleration. However, technical developments could also affect the cost
of launching passengers to orbit from the Moon. Instead of bringing all
fuel and oxidizer from Earth, liquid oxygen could be produced from
lunar materials and hydrogen should be available from the lunar poles.
The cost of producing these on the Moon is yet unknown, but they would
be more expensive than production costs on Earth. The situation of the
local hydrogen is most open to speculation. As a rocket fuel, hydrogen
could be extended by combining it chemically with silicon to form silane,
which has yet to be demonstrated in an actual rocket engine. In the
absence of more technical developments, the cost of transporting people
from the Moon would be an impediment to colonization.
Surface to and from cis-lunar space
A
cis-lunar transport system has been proposed using tethers to achieve momentum exchange.
This system requires zero net energy input, and could not only retrieve
payloads from the lunar surface and transport them to Earth, but could
also soft land payloads on to the lunar surface.
Economic development
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. Zero gravity 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, the gas bubbles rise and burst, but in a
zero gravity environment, that does not happen. The
annealing
process requires large amounts of energy, as a material is kept very
hot for an extended period of time. (This allows the molecular structure
to realign.)
Exporting material to Earth
Exporting
material to Earth in trade from the Moon is more problematic due to the
cost of transportation, which would vary greatly if the Moon is
industrially developed (see "Launch costs" above). 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 100 tonnes 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.
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. The
Shackleton Energy Company estimate investment in this infrastructure could cost around $25 billion.
Solar power satellites
Gerard K. O'Neill, noting the problem of high launch costs in the early 1970s, came up with the idea of building
Solar Power Satellites in orbit with materials from the Moon.
Launch costs from the Moon would vary greatly if the Moon is
industrially developed (see "Launch costs" above). This proposal was
based on the contemporary estimates of future launch costs of the space
shuttle.
On 30 April 1979 the Final Report "Lunar Resources Utilization
for Space Construction" by General Dynamics Convair Division under NASA
contract NAS9-15560 concluded that 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 it became obvious 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.
