Patent Application
20200381135
The present invention relates to electrical generating systems, and to the inducement and production of controlled nuclear fusion by particle-target and muon-catalyzed micro-fusion for electric power generation in the presence of ambient cosmic rays and muons. These may be especially useful in providing sufficient electrical energy for operations in space, such as on the surface of the Moon, Mars, or other lunar or planetary surfaces with little or no magnetic field and/or atmosphere, but may be developed and tested at suitable locations on Earth where ambient muon and cosmic flux is especially high.
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 (about 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 break-even potential.
Another controlled fusion technique is particle-target fusion which comes from accelerating a particle to sufficient energy 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 cosmic rays are abundant in interplanetary space. Cosmic rays are mainly high-energy protons (with some high-energy helium nuclei as well) with kinetic energies in excess of 300 MeV. Most cosmic rays have GeV energy levels, although some extremely energetic ones can exceed 1018 eV.
Cosmic rays are known to generate abundant muons from the decay of cosmic rays passing through Earth's atmosphere. Cosmic rays lose energy upon collisions with atmospheric dust, and to a lesser extent atoms or molecules, generating 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. 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. Measured muon flux levels on Earth reflect the fact that both Earth's atmosphere and geomagnetic field tend to deflect charged particles and shield our planet from cosmic radiation. The amount of shielding is somewhat lower, and thus the cosmic ray flux and muon generation are greater, at higher elevations and altitudes. Mars is a different story, having very little atmosphere (only 0.6% of Earth's pressure) and no magnetic field, so that muon generation at Mars' surface is expected to be very much higher than on Earth's surface. Planetary moons, such as' Earth's Moon, or Phobos and Deimos around Mars, would experience similarly high levels of cosmic ray flux.
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). An efficient power source is necessary for sustaining space-based operations, including running the equipment. As part of any manned exploration and human habitation of Mars, some form of electricity generation will be needed beyond that available from solar cells in order to power the habitats, life support, and scientific equipment.
Sustained investments in fundamental research and early-stage innovation in technologies is required to meet these ambitious goals. Such research and development activity is expected to proceed in several general stages, beginning with an Earth-reliant stage with research and testing on Earth and in low-Earth-orbit (e.g. at the International Space Station), then in cis-lunar space and/or on the lunar surface, to test and validate complex operations and components before moving on to largely Earth-independent stages. Such a proving ground stage would field one or more electrical generation systems to undergo a series of shakedown tests to demonstrate their capabilities, select a final architecture, and make needed upgrades revealed by the shakedown tests. While systems already in development for the initial Earth-reliant missions largely make use of existing technologies, investment in the development of newer technologies will be needed to meet the longer-term deep space challenges. It may be found from the testing that at suitable locations on Earth itself, reliable electrical generation from a large-scale generating farm could become commercially feasible.
Accordingly, the present invention provides a micro-fusion electricity generating farm, comprising an electrical grid having a network of conductive lines and switches, and a plurality of micro-fusion-driven turbine generator units, each generator unit selectively connectable to a conductive line of the electrical grid via one of the switches. Each of these generator units may include a source of deuterium-containing micro-fusion particle fuel material, a columnar reaction volume arranged to receive ambient cosmic rays and muons at an upper end thereof, a flue coupled to the source and reaction volume for dispersing fuel material into the reaction volume, a set of helium-wind turbines arranged around the reaction volume, wherein cosmic rays and muons entering the open end of the columnar reaction volume interact with the dispersed fuel material to cause nuclear micro-fusion events, kinetic-energy-containing micro-fusion products driving the helium-wind turbines; and a set of electrical generators coupled to the respective helium-wind turbines to convert mechanical motion of the driven turbines into electricity. A specified number of the generator units may be connected at any given time to the conductive lines to deliver a specified amount of electrical power to the grid.
The present invention takes advantage of the abundance of cosmic rays and generated muons on a planet or moon, as well as in planetary or lunar orbit or interplanetary space, to catalyze fusion events. The cosmic rays and muons are available here for free and do not need to be generated artificially in an accelerator. Fusion material will interact with the flux of cosmic rays and muons such that some combination of particle-target fusion and/or muon-catalyzed fusion will take place. Thus, each electrical generating unit employs a muon-catalyzed controlled nuclear micro-fusion method to create a “wind” of large numbers of high-energy helium nuclei to drive a set of turbines. These “helium-wind” turbines are mechanically connected to a corresponding number of induction generators to produce electricity. Since the amount of energy needed is generally much less than the multi-kiloton yields of atomic weapons, “micro-fusion” is the term used here to refer to total fusion energy outputs of not more than 10 gigajoules per second (2.5 tons of TNT equivalent per second), to thereby exclude macro-fusion type explosions. Individual micro-fusion reaction units in an electricity farm might produce up to about 10 kilojoules per second output, depending upon the ambient flux levels.
A cloud of fusion material is suspended within a reaction chamber and is bombarded with incoming cosmic rays and muons arriving through the top of the chamber. For example, ports from a fuel supply in the main body may inject a deuterium-containing micro-fusion fuel material as a dispersed cloud into the chamber. The top of the reaction volume may be openable as needed to receive ambient cosmic rays and muons or closed when its power is not needed (or depending upon weather). Alternatively, reaction volume of each generator unit may have a dome covering over its upper end, the dome allowing passage of the ambient flux of cosmic rays therethrough to enter the reaction volume. Ambient cosmic rays and muons penetrate the upper dome into the chamber and interact with the fuel to produce energetic reaction products. This dome might be double-paned and include muon-generating material between the panes, collisions of cosmic rays with the muon generating material supplying muons to the particle fuel material in the reaction volume.
Turbines arranged around the reaction chamber can be driven by the energetic products, such as alpha particles, in order to create electricity. The turbines may be arranged circumferentially around sides of the columnar reaction volume, and even stacked vertically in multiple layers around the sides of the reaction volume. One or more fans could be provided in the reaction volume to maintain the dispersed fuel material in suspension within.
When being tested or used on Earth, the electricity generating farm with its electrical grid and turbine generator units may be located at an altitude greater than 2500 m where ambient muon flux is increased.
With reference to
The micro-fusion electrical generator system works in the presence of an ambient flux of cosmic rays and/or muons which interact with the cloud and trigger the nuclear micro-fusion of the particle target material, either by particle-target micro-fusion or muon-catalyzed micro-fusion or both. The micro-fusion fuel releases as a cloud and can be solid Li6D in powder form, D-D or D-T inertial-confinement-fusion-type pellets, D2O ice crystals, or droplets of (initially liquid) D2. Each electrical generation unit employs a muon-catalyzed controlled nuclear micro-fusion method to create a “wind” of large numbers of high-energy helium nuclei to drive a set of turbines. These “helium-wind” turbines are mechanically connected to a corresponding number of induction generators to produce electricity. A cloud of micro-fusion target material is suspended within a reaction chamber and is bombarded with incoming cosmic rays and muons arriving through the top of the chamber. The micro-fusion target material will then interact with the ambient flux of cosmic rays and muons producing a combination of particle-target micro-fusion and/or muon-catalyzed micro-fusion, generating kinetic-energy-containing fusion products. Turbines arranged around the reaction chamber can be driven by the energetic products, such as alpha particles, in order to create electricity.
With reference to
The reaction chamber need not be circular or radially symmetric, but could have an oval, elliptical, polygonal, or other odd shape. Cylindrical chambers and disc-shaped main bodies may be preferred for their compactness and economy of material, but other shapes are possible.
With reference to
Additionally, the amount of curvature of the dome may be important to maximizing input of cosmic rays and muons into the chamber. The curvature of the “dome” may range from being completely flat to extending considerably upward above the top of the remainder of the reaction volume, perhaps as much as twice as high as its radius. The much larger surface area of a large curvature dome would facilitate cooling of the cover as it is bombarded with ambient cosmic rays penetrating from outside and with micro-fusion reaction products (energetic alpha particles a) from within. A larger curvature might also allow relief of mechanical stresses from any heating that does result.
As seen in
On planetary or lunar surfaces, the chamber will be arranged with its cylindrical or columnar axis pointing in a generally vertical direction, since cosmic rays and generated muons will be arriving from above and the chamber should be pointed in a direction that will maximize receipt of cosmic rays onto the cloud of fusion target material within the chamber.
The deuterium “fuel” for a generator may be supplied in the form of clouds of solid lithium-6 deuteride powder, pellets or chips, or even frozen heavy water (D2O) or liquid droplets of D2, to a reaction chamber 15, where it is exposed to incoming cosmic rays 19 and muons μ, as seen in
For a typical cloud of Li6D in powder form it may be desired to disperse the material near the top of the chamber to allow maximum usage of the material while it settles toward the bottom of the chamber. It might also be advantageous in certain cases to provide one or more fans 20 at the bottom of the chamber 15 (seen in
The dispersed cloud of target material will be exposed to both cosmic rays and to their generated muons. To assist in the formation of muons for muon-catalyzed fusion, especially when D2O or D2 is used, the target package 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 on the Moon, which has no atmosphere.) As cosmic rays collide with both micro-fusion target material and dust, they form muons that are captured by the deuterium and that catalyze micro-fusion. Muonic deuterium, tritium or lithium-6 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, fusion proceeds extremely rapidly (on the order of 10−10 sec). 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).
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 cloud of target material. When bombarded directly with cosmic rays, the lithium may be transmuted into tritium which could form the basis for some D-T fusion reactions. 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 rays and their generated muons should be sufficient to yield sufficient fusion energy output for practical use.
Besides D-D micro-fusion reactions, other types of micro-fusion reactions may also occur (e.g. D-T, using tritium generated by cosmic rays impacting the lithium-6; as well as Li6-D reactions from direct cosmic ray collisions). For this latter reaction, 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 could also be used, fuel material that has been enriched with greater proportions of Li6 is preferable for achieving greater efficiency.
When used on Earth, some care will be needed when using some micro-fusion fuels. For example, lithium hydride (including Li6D) is known to be violently chemically reactive in the presence of water. While reactions with water are not a problem on the Moon or Mars, with any Earth applications the fuel material will need to be encapsulated to isolate it from water sources, including atmospheric vapor. A desiccant can also be used when storing the fuel material.
The rate of fuel usage will depend on the amount of electricity required, the amount of fusion obtained from the ambient cosmic ray and/or muon flux, the dispersal rate of the fuel cloud from the chamber and the efficiency of the transfer of the fusion products into turbine rotation. Assuming most of the energy can be captured, 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 can create hundreds of muons and each muon can catalyze 100 micro-fusion reactions, the available cosmic ray flux in interplanetary space is believed to be sufficient for this purpose following research, development, and engineering efforts.
The deuterium “fuel” may be supplied in the form of clouds of solid lithium-6 deuteride powder, pellets or chips, or even frozen heavy water (D2O) or liquid droplets of D2, to a reaction chamber 15, where it is exposed to incoming cosmic rays 19 and muons p. One technique for creating the cloud of fusion target material is to shoot “fuel” packages as a series of projectiles into the reaction chamber, which can then disperse the fusion material as a localized cloud, much like fireworks or artillery. For this purpose, one or more gun tubes may be located below the chamber and loaded with the packages for introduction into the chamber. Alternatively, packages may be dropped into the chamber from near the top via a slide dispenser. The fuel within the projectile packages can be solid Li6D in powder form, D-D or D-T inertial-confinement-fusion-type pellets, or D2O ice crystals. Stored fuel will be shielded to reduce or eliminate premature fusion events until delivered and dispersed as a cloud in the reaction chamber.
Soon after the projectile has reached the desired dispersal location within the chamber, the package releases its target material. For example, a small chemical explosion can be used to locally disperse the fusion material.
For a typical cloud of Li6D in powder form it may be desired to disperse the material near the top of the chamber to allow maximum usage of the material while it settles toward the bottom of the chamber. It might be advantageous to provide one or more fans 20 at the bottom of the chamber 15 to keep the cloud of target material suspended in the chamber as long as possible.
The optimum concentration of the cloud of target material for the particle-target and 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 thrust against the turbine blades, while avoiding any possibility of runaway fusion.
Because the technology is still early in a developmental phase, testing of its concepts might be perfected at some locations on Earth before its deployment in outer space, even though the ambient flux of cosmic rays and muons may be much lower due to Earth's geomagnetic field and thick atmosphere. Both particle-target fusion and muon-catalyzed fusion, while recognized scientifically, are still experimentally immature technologies (since measurements have only been conducted to date on Earth using artificially accelerated particles and 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. First, testing with prototype electricity farms at convenient higher altitude Earth locations would allow designers to improve the proposed micro-fusion engines before their use on the Moon, and then Mars. A prototype farm may be placed at a convenient high-altitude location on Earth where muon flux is highest. (Both cosmic ray flux and muon generation are known to substantially increase with altitude.) Then, a satellite platform in Earth orbit (for example, on the International Space Station) to improve the efficiency of individual generator units. Still later, a lander on the surface of the Moon are both conveniently close to Earth to place experimental modules in order to determine optimum parameters (e.g. dimensions of the chamber, and cloud density for different fuel types) in order to adequately drive the turbines. For example, the actual number of micro-fusion reactions for various types of fusion fuel sources and target configurations, and the amount of electrical output that can be derived from such reactions, are still unknown and need to be fully quantified in order to improve the technology. The fusion-enhanced propulsion system requires strong cosmic ray flux to create sufficient nuclear micro-fusion, and therefore is best suited to operation in deep space environments.
