The present invention relates to inducement or production of controlled nuclear fusion for use on surfaces of the Moon, Mars, and other planets or moons having little or no magnetic field and/or atmosphere, and in particular to muon-catalyzed micro-fusion as well as particle-target micro-fusion from ambient irradiation and bombardment with high-energy cosmic rays and their muon decay products.
Muon-catalyzed fusion was observed by chance in late 1956 by Luis Alvarez and colleagues during evaluation of liquid-hydrogen bubble chamber images as part of accelerator-based particle decay studies. These were rare proton-deuteron fusion events that only occurred because of the natural presence of a tiny amount of deuterium (one part per 6400) in the liquid hydrogen. It was quickly recognized that fusion many orders of magnitude larger would occur with either pure deuterium or a deuterium-tritium mixture. However, John D. Jackson (Lawrence Berkeley Laboratory and Prof. Emeritus of Physics, Univ. of California, Berkeley) correctly noted that for useful power production there would need to be an energetically cheap way of producing muons. The energy expense of generating muons artificially in particle accelerators combined with their short lifetimes has limited its viability as an earth-based fusion source, since it falls short of breakeven potential.
Another controlled fusion technique is particle-target fusion which comes from accelerating a particle to sufficient energy so as to overcome the Coulomb barrier and interact with target nuclei. To date, proposals in this area depend upon using some kind of particle accelerator. Although some fusion events can be observed with as little as 10 KeV acceleration, fusion cross-sections are sufficiently low that accelerator-based particle-target fusion are inefficient and fall short of break-even potential.
It is known that abundant muons can be derived from the decay of cosmic rays passing through a planet's atmosphere. Cosmic rays are mainly high-energy protons (with some high-energy helium nuclei as well) having kinetic energies in excess of 300 MeV. Most cosmic rays have GeV energy levels, although some extremely energetic ones can exceed 1018 eV.
It is known that as cosmic rays lose energy upon collisions with atmospheric dust, and to a lesser extent atoms or molecules, they generate elementary particles, including pions and then muons, usually within a penetration distance of a few cm. Typically, hundreds of muons are generated per cosmic ray particle from successive collisions. For example, near sea level on Earth, the flux of muons generated by the cosmic rays' interaction by the atmosphere averages about 70 m−2s−1sr−1. The muon flux is even higher in the upper atmosphere. These relatively low flux levels on Earth reflect the fact that both Earth's atmosphere and geomagnetic field substantially shields our planet from cosmic ray radiation. Mars is a different story, having very little atmosphere (only 0.6% of Earth's pressure) and no magnetic field, so that cosmic ray flux and consequent muon generation at Mars' surface is expected to be very much higher than on Earth's surface.
In recent years, there have been proposals to send further spacecraft to Mars in 2018 and then manned space vehicles to Mars by 2025. One such development project is the Mars Colonial Transporter by the private U.S. company SpaceX with plans for a first launch in 2022 followed by flights with passengers in 2024. The United States has committed NASA to a long-term goal of human spaceflight and exploration beyond low-earth orbit, including crewed missions toward eventually achieving the extension of human presence throughout the solar system and potential human habitation on another celestial body (e.g., the Moon, Mars). As part of any manned exploration and human habitation of Mars, one or more forms of heating and lighting, and liquid water, will be needed for the habitats and life support.
A method for providing heating, illumination, or both to a designated local area of a planet, moon, or other space body in the presence of an ambient flux of cosmic rays comprises (a) directing a series of packages of deuterium-containing particle fuel material to a location that is a specified distance from a designated local area, and (b) releasing the deuterium-containing particle fuel material as a localized cloud, the fuel material being exposed to and interacting with the ambient flux of cosmic rays and muons generated from the cosmic rays to produce energetic reaction products together with usable heat and light for the designated local area.
For example, on Mars, the absence of a magnetic field and its thin atmosphere (0.6% of Earth's pressure) allows a substantial flux of cosmic rays to reach the planetary surface and its high mountains. Therefore, locating fusion target material (heavy water, liquid deuterium, lithium-6 deuteride, etc.) on Mars or any other planet or moon with a thin atmosphere can make use of the muon generation from such cosmic rays to catalyze fusion. The muons are available here for free and do not need to be generated artificially in an accelerator. One cosmic ray particle can generate hundreds of muons, and each muon can typically catalyze about 100 fusion reactions before it decays (the exact number depending on the muon “sticking” cross-section to any helium fusion products). Additionally, any remaining cosmic rays can themselves directly stimulate a fusion event by particle-target fusion, wherein the high energy cosmic ray particles (mostly protons, but also helium nuclei) bombard the relatively stationary target material.
Created by collisions of cosmic ray particles with atmospheric dust and molecules, muons are used in several ways in the present invention. The main reaction is in catalyzing fusion of two deuterium nuclei. The deuterium “fuel” may be supplied in the form of heavy water (D2O) or liquid deuterium (D2) or even solid Li6D. Other types of fusion reactions are also possible depending upon the target material. For example, the Li6D reaction is Li6−D→2He4+22.4 MeV, where much of the useful excess energy is carried as kinetic energy of the two helium nuclei (alpha particles). Additionally, when bombarded directly with cosmic rays, the lithium may be transmuted into tritium which could form the basis for some D-T micro-fusion reactions.
Since the amount of generated energy is on the order of kilowatts, which is very much less than the fusion energy outputs or yields typical of atomic weapons, “micro-fusion” is the term used here to refer to fusion energy outputs of not more than 10 gigajoules per second (2.5 tons of TNT equivalent per second), to thereby exclude runaway macro-fusion-type explosions.
In the present invention, muons from cosmic ray decay replace electrons in deuterium, allowing for a reduced size molecule because, as realized by Charles Frank in 1927, being about 200 times more massive than electrons, muons orbit much nearer to the central nucleus than the electron replaced. Muonic deuterium can come much closer to the nucleus of a similar neighboring atom with a probability of fusing deuterium nuclei, releasing energy. Once a muonic molecule is formed, nuclear fusion proceeds extremely rapidly (on the order of 10−10 sec). The muon is usually released to catalyze about 100 other fusion reactions during its short life (2 μs at rest, but longer at relativistic speeds generated by cosmic rays). Although D-D fusion reactions occur at a rate only 1% of D-T fusion, and produce only 20% of the energy by comparison, the freely available flux of cosmic ray generated muons on planets (such as Mars) or moons with thin atmospheres should be sufficient to yield sufficient energy output by muon-catalyzed fusion for practical use. Energetic protons, which make up about 90% of the cosmic rays, must have a collision energy loss of at least 300 MeV for a muon to be created. Most cosmic rays are energetic enough to create multiple muons (often several hundred) by successive collisions with atmospheric dust or with the atoms in a fusion target. Any cosmic rays that reach the Martian surface or target area with sufficient residual energy can also directly induce some nuclear fusion events by particle-target type fusion, supplementing those obtained from the muons.
The present invention achieves muon-catalyzed nuclear micro-fusion using deuterium-containing target material, and muons that are naturally created from ambient cosmic rays. Most cosmic rays are energetic enough to create multiple muons (often several hundred) by successive collisions with atmospheric dust or with the atoms in a target. In fact, most cosmic rays have GeV energies, although some extremely energetic ones can exceed 1018 eV and therefore potentially generate millions of muons. The optimum concentration of the target material for the muon-catalyzed fusion may be determined experimentally based on the particular abundance of cosmic rays with a view to maintaining a chain reaction of fusion events for producing adequate heat or illumination photons for the specified application while avoiding any possibility of runaway fusion in the muon rich environment (each muon can catalyze multiple fusion events, as many as 100, before it eventually decays).
At a minimum, since muon-catalyzed fusion, while recognized, is still an experimentally immature technology (since measurements have only been conducted to date on Earth using artificially generated muons from particle accelerators), various embodiments of the present invention can have research utility to demonstrate feasibility in environments beyond Earth's protective atmosphere and/or geomagnetic field, initially above Earth's atmosphere for trial purposes, and then on the Moon or the surface of Mars, in order to determine optimum parameters for various utilities in those environments. For example, the actual number of muon catalyzed fusion reactions for various types of target configurations and fusion fuel sources, and the amount of heat, illumination, or useful work that can be derived from such reactions, are still unknown and need to be fully quantified in order to improve the technology.
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The fuel can be D2O ice crystals, droplets of (initially liquid) D2, or even solid Li6D in powder form. The quantity of active fuel material needing to be released is generally small, since only a microgram of micro-fusion material consumed per second will produce a kilowatt of output. To assist muon formation, especially when D2O or D2 is used, the target package 11 or 21 may contain up to 20% by weight of added particles of fine sand or dust. (This is particularly important if one desires to create a similar fusion reaction over the Moon, which has no atmosphere.)
Besides D-D micro-fusion reactions from D2O or D2, other types of micro-fusion reactions may also occur when using Li6D material. Cosmic rays impacting the lithium-6 will generate tritium for D-T micro-fusion reactions. Additionally, direct cosmic ray collisions can cause Li6−D reactions via particle-target fusion. It should be noted that naturally occurring lithium can have an isotopic composition ranging anywhere from as little as 1.899% to about 7.794% Li6, with most samples falling around 7.4% to 7.6% Li6. Although LiD that has been made from natural lithium sources might be used in lower energy yield applications or to inhibit a runaway macro-fusion event, fuel material that has been enriched with greater proportions of Li6 is preferable for achieving greater energy output per microgram of fuel. (Lithium hydride is periodically of interest for hydrogen storage, but practical terrestrial applications have been thwarted by its chemical instability and its violent reactiveness in the presence of water. However, this should not be a problem on the Moon or Mars, where water is scarce and doesn't occur in liquid form.)
Packages 11 or 21 may be shielded to reduce or eliminate premature fusion events (e.g. during transport through space) until delivered to the desired location. Soon after the projectile 11 has reached peak altitude and is beginning its downward traversal the package releases its target material. For example, a chemical explosion can be used to locally disperse the fusion material. The dispersed cloud 13 of target material will slowly settle down above or downrange from the plateau 19 and be exposed to both cosmic rays 31 and their generated muons μ. As cosmic rays 31 collide with fusion targets and dust, they form muons μ that are captured by the deuterium and cause fusion. Other types of fusion reactions may also occur (e.g. D-T, using tritium generated by cosmic rays impacting the lithium; as well as Li6−D reactions from direct cosmic ray collisions).
The muon-catalyzed micro-fusion reactions, where the muons μ are generated from cosmic rays 31, may be used to create successive miniature suns shining from the clouds 13 or 25 on or near mountain tops 17 on Mars, much like a bright flare. The miniature suns shining upon the ground, a kind of “external” combustion in the sky, will illuminate and heat the local area 15 below. As such, they will function in much the same way the sun does to heat the atmosphere and ground surface, including any water ice 41 on the Martian surface, by infrared radiation. The amount of heat and light energy that is generated depends upon the quantity of fuel released and the quantity of available cosmic rays 31 and muons μ. An estimated 1015 individual micro-fusion reactions (less than 1 μg of fuel consumed) per second would be required for 1 kW output. But as each cosmic ray 31 can create hundreds of muons μ and each muon p can catalyze approximately 100 micro-fusion reactions, the available cosmic ray flux is believed to be sufficient for this purpose following research, development, and engineering efforts to optimize fuel release rates and altitude.
The needed rate of firing of fuel projectiles 11 or 21 depends on the amount of heat and light energy required, the dispersal rate of the fuel cloud 13 or 25, the amount of fusion obtained from the ambient cosmic ray and/or muon flux at the designated altitude of material cloud dispersion, and the efficiency of conversion of the micro-fusion products' kinetic energy into heat and light, but could be expected to be at least one shell per minute for the needed duration.
One application is to use the heat energy (infrared radiation) to melt surface water ice 41. The amount of heat needed will depend upon both initial ambient surface temperatures and the quantity of water to be heated. Inasmuch as the atmospheric pressure on Mars is too thin for water to exist in liquid form (water sublimates directly from solid to gas if pressure is less than 612 Pa), the target area 15 may have greenhouse structures 43 set up to raise the gas-vapor pressure immediately above the ice 41 and support melting. Pressure in the greenhouse structures need only be increased slightly. (At just 1200 Pa, boiling point has already increased to about 10° C.) The greenhouse structures 43 placed on the ice may be weighted around the bottom sides 45 to contain the liquid water 47 and supporting atmosphere. As the radiation from the muon-fusion generated mini-suns shines through the greenhouse 43, it heats the ice 41, while the greenhouse 43 also traps the infrared radiation so that the interior stays warm enough to keep the water 47 in liquid form until it can be drawn off and used.
Besides local heating and illumination of specified surface areas, the mini-suns may also serve as nighttime illumination of underground dwellings 51 via skylight roofing covers 53.
This application claims priority under 35 U.S.C. 119(e) from prior U.S. provisional application 62/365,511, filed Jul. 22, 2016.
Number | Date | Country | |
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62365511 | Jul 2016 | US |