Lunar Activities

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

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.

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.

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

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. 

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

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

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

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.

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.

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

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.

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.