Patent Number: 051620944
Section: summary

BACKGROUND OF INVENTION The present invention relates to an apparatus and method of achieving a fusion propulsion engine as could be used by a starship that is both highly efficient and is capable of achieving very high fuel specific impulse. The invention also relates to the use of said basic engine as a generator for supplying very large amount of power in the form of heat that can then be converted to electrical energy by use of conventional steam turbogenerators. The search for controlled fusion has been a major scientific effort for many years. The major thrust has been directed at the brute force approach of heating a gaseous mixture (usually deuterium and tritium) in the form of a plasma (ionized gas) to sufficient temperature and pressure and then holding this state for sufficient time to allow the nuclei of the mixture to collide and thus fuse with the liberation of energy. Despite the expenditures of vast sums of money and effort, this approach has yet to achieve a "breakeven" condition as defined by the point at which the amount of energy being produced is equal to the amount of input energy. The "breakeven" condition, assuming it can eventually be achieved by the plasma "ohmic heating approach" would represent only about 1% of the available fusion energy being realized and with 99% being lost. The major difficulty with the plasma heating approach has been that the only way to contain the plasma during the heating phase is with magnetic fields. The plasma has, so far, always been able to exhibit some form of instability that has prevented the magnetic fields from being able to contain the heated, ionized gas for sufficient time to even reach the breakeven point in energy production. The present prediction is that it will be at least 40 years before this approach can be expected to produce useful energy. The production of useful energy is estimated to require a fusion energy output at least 10 times the breakeven point. It may also be true that this approach will never work in terms of producing useful energy from a fusion process. In the late '60s another approach was given serious consideration in an attempt to solve the controlled fusion problem. This approach involved the creation of a potential well through which ionized particles (again notably deuterium and tritium, the D-T reaction) were made to osillate at high relative energies and thus occasionally experience a head-on collision that resulted in fusion. The best example of this approach is contained in a paper by Dr. R. L. Hirsch (Inertial-Electrostatic Confinement of Ionized Fusion Gases, J. Appl. Phys. 38, No. 11, 4522-4534, 1967) in which it was reported that significant neutrons (the product of a D-T fusion reaction) were detected from the apparatus as described in the article. It is believed that the approach was abandoned, however, as it did not appear that it could lead to the generation of useful amounts of energy. Its major problem was that the maximum relative ion energy occurring at the center of the potential well was also the point of minimum density. The low density at the well's center prevented appreciable fusion reactions from occurring. SUMMARY OF THE INVENTION The present invention is a form of the potential well approach to fusion. In this approach gaseous, positive ionized molecules are injected into a potential well (in a vacuum) as formed by an electrostatically negative, ring electrode that is constructed to first accelerate the ions through a potential as determined by the magnitude of voltage of the negative electrode and then decelerate them as they attempt to leave the vicinity of the electrode. The ions are thus captured in the potential well and will repeatedly oscillate through the well as the ion energy is continually exchanged between kinetic and potential. This is basically the approach as described in the Hirsch paper as previously cited. A departure from previous efforts is accomplished in the present invention by allowing the potential well to exist in a uniform magnetic field and by the further innovation of using two accelerating ring electrodes of the same negative potential and thus create a constant potential drift region in the magnetic field between the two rings. After an initial ion acceleration to high velocity by the first electrode, the ions are caused to move across the drift region at essentially constant high velocity until they reach the second electrode. After passing through the second electrode they will then experience a deceleration force until finally reversing their direction and with the second electrode accelerating them again though the potential well. In this manner the ions are made to repeatedly oscillate though the drift region, potential well of the device as they are caused to move between the two electrodes. In addition, the action of the uniform magnetic field acting on the ions though their entire flight causes the individual paths to be brought to a focus within the drift region that can be designed to be the region's midpoint. After passing through the magnetic convergent point in the drift region, the ions diverge before reaching the second electrode and are then decelerated to be refocused to a virtual anode before reversing direction to repeat the oscillating process. The ions at the drift region focus point are thus in a concentrated form and possess high energies. As new ions can be continually added to the potential well from the ion source (or sources) the ion concentration at the convergent point can continually be made to increase. In addition, on the average, the convergent point will always contain equal numbers of ions moving in opposite directions. If the ions being used are the two heavy isotopes of hydrogen, deuterium and tritium, and the accelerating potential for the ions is in the range of 100 Kev, then head-on collisions will result in fusion occurring. Collisions between deuterium and tritium can be used by the application of this invention to achieve a fusion condition and thus the creation of very high energy fusion byproducts. The equation for this reaction can be expressed as .sub.1 D.sup.2 +.sub.1 T.sup.3 .fwdarw..sub.2 He.sup.4 +.sub.o n.sup.1 +17.6 Mev where the subscripts denote the number of protons while the superscripts provide the number of both protons and neutrons and thus the atomic mass. The D-T fusion reaction is the most easily accomplished as only a single proton exists in the nuclei of the two input gases, D and T, that presents an electrostatic barrier needing to be overcome by the relative energy of the two colliding nuclei. As shown by the equation, the neutron and helium byproducts of the reaction share in the resultant fusion energy of 17.6 Mev in proportion to their mass with approximately 1/5 the total energy being contained by the kinetic energy of the neutron. While the D-T fusion reaction requires the least amount of input energy to overcome the repulsive potential barrier caused by the two protons in the nuclei, a problem exists in that an appreciable amount of the resultant fusion energy released is contained by the kinetic energy imparted to the neutron that is not ionized and thus its flight path cannot be controlled by either electrostatic or magnetic fields. For some fusion applications, such as a fusion propulsion engine for a spacecraft, it is very desirable that all resultant fusion particles can be controlled to prevent them from impacting spacecraft structure. Impacts would cause the kinetic energy of the collision particle to be transformed into heat that would have to be rejected by the vehicle to prevent it from being vaporized by its own waste heat, assuming even a modest size propulsion unit. Calculations show that if a D-T fusion reaction is used for spacecraft propulsion, the neutron from the reaction will cause insurmountable waste heat problems for engines that have in excess of about 1000 pounds thrust. A more favorable fusion reaction for use in a spacecraft that could also be employed by the present invention is the deuterium-helium.sup.3 reaction (.sub.1 D.sup.2 +.sub.2 He.sup.3 .fwdarw..sub.2 He.sup.4 +.sub.1 H.sup.1 +18.3 Mev). As both fusion byproducts (.sub.2 He.sup.4 and .sub.1 H.sup.1) are ionized, their paths can be controlled by a sufficiently strong magnetic field to prevent the particles from contacting spacecraft structure including the electrical conducting coils (that could be superconductors) as used to generate the magnetic field. It can be shown that if a magnetic field in the range of 10,000 gauss is generated by a 14 foot minimum diameter solenoid, fusion particles from a D-he.sup.3 reaction generated along the major axis of the solenoid will be forced by the magnetic field into spirals having diameters less than the radius of the solenoid and thus prevented from reaching the solenoid structure. The particles instead will spiral to the two ends of the solenoid and then leave the magnetic field as its field strength diminishes to a point insufficient to further contain the particles. In addition, by altering the form of the solenoid from a simple cylinder to a U-shaped configuration, the ionized, high energy particles can be made to exit the magnetic field from the ends in essentially the same direction and thus impart a net momentum transfer of thrust to the spacecraft by virtual of the solenoid's magnetic field forcing the particles to experience a 90.degree. change in direction. By use of the D-He.sup.3 fusion reaction, all resultant fusion particles can be deflected by the magnetic field and can thus result in useful thrust in addition to avoiding waste heat collisions with the spacecraft structure. The D-He.sup.3 reaction has, however, two problems that need to be addressed. First, the light isotope of helium, He.sup.3, does not exist in nature and thus must be manufactured. One method for accomplishing this goal is to create a supply of tritium by bombarding the relative abundant light lithium isotope, Li.sup.6, with neutrons: EQU .sub.o n.sup.1 +.sub.3 Li.sup.6 .fwdarw..sub.2 He.sup.4 +.sub.1 T.sup.3 The tritium so produced can then be stored allowing radioactive decay to proceed with a half life of 12.3 years and thus generate the desired light helium isotope: EQU .sub.1 T.sup.3 .fwdarw..sub.2 He.sup.3 +beta A second method that will result in the direct production of helium.sup.3 is to use the present invention to cause deuterium ions to collide in a fusion reaction by use of the present invention: EQU .sub.1 D.sup.2 +.sub.1 D.sup.2 .fwdarw..sub.2 He.sup.3 +.sub.o n.sup.1 Of equal probability, however, when two deuterium nuclei collide is the fusion reaction: EQU .sub.1 D.sup.2 +.sub.1 D.sup.2 .fwdarw..sub.1 T.sup.3 +.sub.1 H.sup.1 The tritium so produced can be stored to generate an additional amount of helium.sup.3 by allowing radioactive decay to proceed as with the neutron-lithium.sup.6 reaction. A second problem with the D-He.sup.3 reaction is that more initial energy is required to overcome the nuclei potential barrier than for the D-T reaction. The optimum input energy allowing two nuclei to fuse for the D-T reaction is about 100 Kev and therefore giving a relative energy of 200 Kev during head-on collisions. Because the helium nucleus has two protons, it can be shown that the optimum input energy for fusion of the input particles must be doubled to about 200 Kev and thereby achieving a relative energy of 400 Kev during head-on fusion collisions. However, as the resultant energy from the D-He.sup.3 reaction is 18.3 Mev as compared to 17.6 Mev for the D-T reaction, the net gain in energy favors the deuterium-helium.sup.3 reaction. Achieving sustained fusion conditions allowing essentially 100% utilization of fuel with either the D-T or D-He.sup.3 reaction at the magnetic convergent point in the drift region of the present invention will require a high density of ions in addition to high relative energy between particles. As the geometry of the magnetic focus, fusion region of the present invention is a mirror image of the ion source geometry, it is, of course, important that the ion source geometry have as small dimensions as possible to produce the highest concentration of input nuclei at the magnetic convergent point. One method of achieving this goal is to use a modification of an invention by the American inventor, Nicola Tesla (U.S. Pat. No. 493,776, Incandescent Electric Light, 1892). In this invention Tesla showed how a small button of refractory material such as diamond could be heated to incandescent temperatures by allowing the material to be bombarded by ions as caused by the application of a high voltage, high frequency excitation to the refractory material. One embodiment of the present invention makes use of Tesla's Incandescent Electric Light by adding a few thousands of an inch diameter hole through the refractory material button. The added hole allows the passage of the input gases as required for the fusion reaction. As the gases are passing though the hole in the center of the button, they are heated to a high temperature that can be in the range of 5,000.degree. F. as they make contact with the inner walls of the refractory material (diamond, for example). Upon leaving the hole exit, the already thermally excited molecules of gas are then totally ionized by the high intensity, RF field in combination with the concentrated ion bombardment created by the RF field. The net result is a highly concentrated ion source insuring that the ion concentration at the magnetic focused point of the present invention will be sufficient for a high probability of fusion reactions occurring. With either the D-T or the D-He.sup.3 fusion reaction two problems are encountered in using the potential well approach that need to be addressed. The first is the mutual repulsion force acting between the positively charged ions trapped in the potential well. This force will act to defocus the particles as they are made to magnetically converge within the drift region of the device. As the amount of defocusing as caused by the mutual repulsion force is proportional to the number of ions present, adding ions to the potential well in order to increase the density at the convergent point will tend to be nullified by the increased repulsive force. Offsetting this effect, however, is the fact that free electrons will always be present in the ion stream that will act to shield the individual ions from each other. Electron shielding will therefore permit high nuclei density in the oscillating beams at their convergent points. A second potential cause of defocusing of the ion beam at the convergent points is the problem of ion scattering as caused by near misses of two approaching nuclei. Most ions, in fact, will experience many scattering collisions before encountering a fusion collision. After a scattering collision the near miss of the two ions can cause an alteration of trajectories approaching 90.degree. and without corrective action there would be little hope of achieving an appreciable number of fusion reactions at the magnetic focus region as the particles would be scattered before a fusion reaction could occur. The corrective action is achieved by the fact that the initial ion scattering occurs in a magnetic field that controls the flight of the two particles after scattering happens. The magnetic field forces the nuclei to return to the exact spot where the initial scattering occurred during the next oscillation of the particles through the potential well of the apparatus. The ion density at the magnetic focus region is thereby allowed to increase as new ions are added to the well despite scattering. An ion trajectory moving exactly perpendicular to the axial magnetic field of the encompassing solenoid after scattering (the 90.degree. scattering angle) will always cause the trajectory to be a circle and in one revolution the ion will return to the precise site in the magnetic focus region at which the initial scattering occurred. It can be shown that the maximum radius of curvature will be about 9 centimeters for a 90.degree. scattered, 200 Kev deuterium ion and a little over 11 centimeters for a 200 Kev helium.sup.3 ion when the scattering happens in a 10,000 gauss magnetic field. The general case scattering angle will be less than 90.degree.. Scattered ions normally will then have two components of velocity, one parallel to the magnetic field and the second perpendicular to the field at a radius of curvature less than the 90.degree. case. The general case trajectory of an ion experiencing a near miss at the site of the magnetic focus region will, therefore, be a helix of diameter, D, less than 2.times.11 or 22 centimeters and having an axial velocity bringing it to one or the other of the accelerating rings of the potential well generator. If the ring diameter is at least 2D (44 centimeters) the ion will pass through and then experience deceleration as it leaves the ring's vicinity. When the electrode has brought the ion's velocity and thus its helix diameter to zero, the ion will then exactly retrace its path through the accelerating electrode and converge with other ions to the spot in the magnetic focus region where the near miss scattering collision had previously occurred. Therefore, even if the ion scattering occurs within the magnetic focus region, the action of the axial magnetic field will always bring the scattered ions back to a convergent point. By continually feeding new ions into the stream, the nuclei density at the magnetic focus/fusion point will continue to increase until fusion reactions are occurring at the same rate as new ions are being introduced and thus, essentially 100% fuel utilization and thus 100% fusion energy production is the result. One embodiment of the present invention would be for a spacecraft propulsion engine in which a U-shaped configuration of the magnetic containment field solenoid would be used to direct the ions produced from the fusion reaction in essentially the same direction when exiting the two solenoid and thus produce a net thrust to the craft. A second embodiment of the present invention would be for the generation of output power by placing two heat exchangers at the exit ends of the solenoid to intercept the resultant fusion ions and thus convert their kinetic energy to heat. In the latter power generating configuration a straight solenoid could be used as net thrust would not be required to be produced. In the power generating configuration the two heat exchangers could then be used to produce superheated steam allowing the generation of electrical energy from conventional turbogenerator power generating plants. It can be shown that a modest size, 10,000 pound thrust, spacecraft propulsion unit, when equipped with the necessary heat exchangers for the conversion of the kinetic energy of the fusion particles to heat, would have an output capacity of over 500,000 megawatts (0.5.times.10.sup.12 watts) in the kinetic energy of its exhaust. This is a prodigious amount of power and can be compared to the total power level of the 15.times.10.sup.12 watts presently used by the world including all forms of fossil fuel combustion in addition to the world's total electrical production. One 10,000 pound thrust engine as described is therefore capable of generating approximately 1/25 the power requirements of the world. Of course, a larger number of smaller capacity units could also be constructed allowing both more manageable size power generating stations and greater flexibility of energy distribution. Converting some electrical energy produced at the output of the turbogenerators into hydrogen (electrolysis of water to hydrogen can be accomplished at an 83% energy efficiency conversion level), could also be employed as a means of further increasing the ease of energy distribution and use. Hydrogen as a gas could be used as a direct replacement for all present low pressure burning of fossil fuels such as space heating and gas/oil/coal driven electrical power generating plants. By this means roughly 75% of the present world's CO.sub.2 production and thus the Greenhouse Effect would be eliminated. The remaining 25% of the present world's CO.sub.2 production is caused by the use of internal combustion engines required primarily for transportation. Electrical energy produced from the fusion engine could first be converted to hydrogen, and the hydrogen could then be combined with carbon monoxide in a catalytic convertor to result in methanol. Methanol is a liquid at room temperatures and can thus become the direct replacement for gasoline while allowing the use of existing internal combustion engines with only minor fuel mixture modification.