Lunar Resources
Helium-3 for fusion reactors Requires higher reactor performance Requires strip-mining much of the maria Mining Lunar Helium-3Why? Proposed fusion reactor fuel D-T: 2H+3H -->4He+1n D-3He: 2H+3He -->4He+1H D-T Advantages Higher power density Lower ignition temperature (10-20 keV vs. 50-60) Fuel available D-3He Advantages (Almost) no neutrons Larger reactor wall lifetime Less radioactivity Higher fraction of energy directly convertible Sources (in tonnes - 103 kg) Earth - 0.5 Sun - 2x1022 Moon - 1x106 3 km NEA - <1 All big (>200 km) main belt asteroids - 4x104 Jupiter - 1020 Uranus - 4x1018 Orbiting solar power satellites (lunar material) Idea dropped in late 1970s May be cheaper if you can use lunar material Requires beaming microwaves to Earth Solar power stations on the Moon In some ways easier than satellites (stable base) Again, beam microwaves to Earth Requires massive construction effort on Moon
Ilmenite reductionFeTiO3+H2 <---> Fe+TiO2+H2O H2O <---> H2+1/2O2 Requires pure ilmenite to work Use basalts, where there's no agglutinates Requires reducing agent Hydrogen most common candidate Fluorine also possible Magma electrolysis Electolysis on melted rock Oxygen, metal, silicate slag as products Requires enough power to melt rock
Extremely high vacuum The diffuse lunar atmosphere has a density comparable to the finest vacuums attainable in terrestrial labs, allowing observations to be made in ALL wavelengths other than perhaps the very lowest frequency radio astronomy Telescopes can be made with their full resolving power Radio, infrared, and optical interferometers can be established with baselines of up to tens or even hundreds of kilometers The lack of atmosphere means that exposed optical surfaces should retain their full efficiency for very long times limited only by micrometeorite effects SETI Distance from Earth greatly reduces terrestrial RFI, gamma ray, and radar noises (by inverse square law) The lunar far side offers complete radio silence at all frequencies, making it an ideal site for SETI and VLF investigations Stable Solid Platform Allows simple low-cost terrestrial-type mountings to be used instead of very expensive attitude pointing systems used by space observatories Cosmic Ray Protection for Humans Extra-solar-system cosmic rays include high energy components very difficult to shield against, which result in radiation damage in the bodies of crew members exposed for relatively long times During periods of intense solar activity high energy particles can be lethal to exposed Astronauts on the lunar surface, with warning times of maybe only a few minutes The Moon offers essentially full protection, given the simple precaution of having nearby habitations and shelters under some meters of lunar material Cosmic Ray Protection for Detectors Outside the Earth's magnetic field, the performance of sensitive detectors for most types of radiation will be degraded by noise caused by solar and galactic cosmic rays Some instruments may avoid this problem by being located beneath the lunar surface, looking out through a small aperture For surface instruments the Moon's low gravity and stability as an observing platform offer the possibility of truly massive shielding around the detector package
Dark Sky No atmospheric scattering means that the deepest observations can be made at night even when there is a "full Earth" Assuming the lunar habitat to be located near the lunar limb, total shielding from earthlight follows simply by placing telescopes behind a small hill or nearby screen Cold Sky A well-insulated and shielded (from any direct or reflected radiation not coming from the dark sky) lunar telescope would cool to and remain at an exceedingly low temperature, thereby eliminating the need for expensive cryogens, as well as allowing the telescope to be very large Low Gravity The low lunar gravity (1/6 of Earth's gravity) would allow structures of any size to be much lighter and less expensive to construct than their terrestrial counterparts The modest lunar gravity also causes debris and contaminants to fall to the surface, rather than tagging along in place as they tend to do in space Absence of Wind On the Moon structures can be built with attention purely to static and thermal loads Rotation The Moon's roughly month-long rotation period guarantees access to all the sky accessible from the latitude of the observatory site, yet is slow enough to permit very long integrations on the faintest possible objects (such as quasars) The Moon's slow rotation time permits up to 14 days continuous exposure (unlike LEO orbits which are troubled by frequent Earth eclipses) from low latitudes sites; polar sites permit exposures of indefinite length for correspoding hemisphere The rotation also gives free sky-scanning to very large telescopes and the possibility of aperture synthesis to interferometers Proximity to Earth Round trip communication time (< 3 sec) allows possible Earth-based control of robotic systems, allowing detailed real-time control of observing programs
Distance from Earth At roughly 400,000 km from Earth, the Moon is far enough away to be relatively free of terrestrial interference caused by humans Except for certain radio frequency bands, observations from the Moon will be virtually unaffected by the presence of the Earth in the sky The Lunar Farside For limiting sensitivity SETI observations must have a site which NEVER sees the Earth in its sky Raw Material Lunar regolith forms useful shielding against cosmic rays as well as outstandingly good insulating material As processing facilities gradually come into operation, various cements and building blocks, then ceramics, glasses, fibers, and metals will become available Landforms Symmetric lunar craters come in almost any desired size Aided by the low lunar gravity and lack of wind and weathering action, large radio telescopes (like the 300 meter Arecibo dish) are likely to be built on the Moon Room The Moon offers effectively unlimited area for laying out systems of instruments, which can be added to at any time, and yet all be conveniently located at one or more common bases for access to consumable supplies, replacement parts, power, computer support, communications with Earth, etc. Calibration of Instruments A near side observatory would allow the use of Earth as a calibration/comparison target for reflectance spectroscopy and other related observations Earth Observations Astronomical study of Earth is possible. Almost entire hemisphere visible at once including one pole, possibly two
Interferometry Very long baseline Moon-Earth interferometry possible, providing extremely high resolution and sensitivity Debris No orbital debris problem; micrometeroid flux similar to Earth orbital; no glow effects from collisions with residual atmosphere Access Allows construction of major, highly sophisticated space telescopes and instrumentation in extremely simple, relatively low-cost mountings and housings, with virtually all components readily accessible for maintenance or change by skilled people in the immediate vicinity
Exploration of the lunar surface in search of oxygen-rich soil, hydrogen, helium-3, and water, is one of the most important goals that NASA must undertake before establishing a lunar base. With the exception of water, all of these are found in varying concentrations in the lunar regolith. Water is probably more abundant than helium-3 in the lunar regolith, but more studies are needed to confirm this. The most likely place on the Moon where water ice may be found is below the surface in doubly-shadowed craters, which act as permanent cold traps.
The most obvious use of water is for life support purposes. Water can also be broken down into its basic elements, hydrogen and oxygen through the process of electrolysis, which uses an electrical current to break apart water molecules. The hydrogen and oxygen are then used as a rocket propellant.
Although no ice was found in lunar samples returned by the Apollo astronauts, scientists still speculate that ice may be present deep under the regolith lining select craters. One theory is that the ice was deposited by meteoroids or comets impacting the Moon, uncovering ice deposits at the lunar poles.
As is evident from spectroscopic studies, comets are known to contain large amounts of water. The masses of individual comets are estimated to be in the range of 10E16 grams (for a 1 km size object) or even larger. Hence the impact of even a single comet would bring in an amount of water comparable to the meteoroid impact mechanism, in which low-velocity meteoroids impact the lunar surface, providing the source of water. Such low-velocity impacts do not heat the meteoroid material to the extreme temperatures necessary for chemical decomposition of water vapor. Except for the very largest impacts, this source is essentially a steady one. Impacts of short-period (low-velocity, <20 km/s) comets would supply a large amount of water. Both Tycho and Copernicus provide direct evidence that such massive comets (10E16 grams) have impacted the Moon. However, the uncertainties of the estimates of this water source is also very large, since neither the mass distribution nor the impact rate of comets is known very well. Also, the physical models of the phenomena which occur during and immediately after the impact are not well known.
Summary of lunar water search program