INTERPLANETARY SPACECRAFT USING FUSION-POWERED CONSTANT-ACCELERATION THRUST

Abstract

A spacecraft propulsion method uses cosmic ray triggered nuclear micro-fusion events to provide repeated or continuous thrust for artificial gravity during a space flight. In one embodiment, successive packages of deuterium-containing micro-fusion particle fuel material is projected in a specified direction outward from a spacecraft. In another embodiment, the micro-fusion fuel material is a coating upon a set of angled rings arranged circumferentially around the spacecraft. In a third embodiment, the micro-fusion fuel is dispersed in proximity to wind turbines to generate electricity for ion thrusters. In each case, the material interacts with the ambient flux of cosmic rays to generate micro-fusion products having kinetic energy that either produce thrust upon the spacecraft or drive the turbines whose electrical output in turn powers the ion thrusters.

Claims

1. A method of spacecraft propulsion system for use in the presence of an ambient flux of cosmic rays, comprising: projecting successive packages of deuterium-containing particle fuel material in a specified direction outward from a spacecraft, the material interacting with the ambient flux of cosmic rays to generate products having kinetic energy; and receiving on the spacecraft at least some portion of the generated kinetic-energy-containing products to produce thrust upon the spacecraft; wherein the deuterium-containing particle fuel material is successively projected from the spacecraft in amounts and direction such that the thrust produces a repeated or continuous acceleration of the spacecraft with a specified trajectory.

2. The propulsion method as in claim 1, wherein the repeated or continuous acceleration has a substantially constant magnitude throughout a substantial portion of a spacecraft flight to a destination.

3. The propulsion method as in claim 2, wherein the substantially constant magnitude acceleration is in a first forward direction along the spacecraft trajectory for a first half of the spacecraft flight to its destination and in a second opposite direction producing equivalent deceleration for a second half of the spacecraft flight.

4. The propulsion method as in claim 2, wherein the destination is a planet and the substantially constant magnitude of the acceleration is equal to a specified proportion of gravitational acceleration at the planet's surface, the specified proportion being at least 25%.

5. The propulsion method as in claim 4, wherein the destination is Mars and the substantially constant magnitude of acceleration during the spacecraft flight is at least 40% of the surface gravitation on Mars.

6. The propulsion method as in claim 1, wherein the deuterium-containing particle fuel material is Li.sup.6D.

7. The propulsion method as in claim 1, wherein the deuterium-containing particle fuel material is D.sub.2O.

8. The propulsion method as in claim 1, wherein the deuterium-containing particle fuel material is D.sub.2.

9. The propulsion method as in claim 1, wherein the deuterium-containing particle fuel material is in solid powder form.

10. The propulsion method as in claim 1, wherein the deuterium-containing particle fuel material is in pellet form.

11. The propulsion method as in claim 1, wherein the deuterium-containing particle fuel material is in frozen form.

12. The propulsion method as in claim 1, wherein the deuterium-containing particle fuel material is in liquid droplet form.

13. The propulsion method as in claim 1, wherein the successive packages are shell projectiles shot from at least one gun forming a part of the spacecraft.

14. The propulsion method as in claim 1, wherein each package is configured to disperse the deuterium-containing particle fuel material as a localized cloud at a specified distance from the spacecraft.

15. The propulsion method as in claim 14, wherein dispersal of the deuterium-containing particle fuel material is by means of chemical explosive.

16. The propulsion method as in claim 1, wherein the packages of deuterium-containing particle fuel material also contain up to 20% by weight of added particles of fine sand or dust.

17. A spacecraft propulsion method for use in the presence of an ambient flux of cosmic rays, comprising: providing a set of ring structures around a circumference of a spacecraft, each ring structure oriented at a specified angle to a length of the spacecraft and coated with deuterium-containing micro-fusion fuel material, wherein the deuterium-containing material when interacting with an ambient flux of cosmic rays generates fusion products having kinetic energy and thereby produces thrust upon the spacecraft; and means for controlling exposure of the micro-fusion fuel material to cosmic rays.

18. The propulsion method of claim 17, wherein the means for controlling exposure comprises a set of shields that are adapted to slide in front of the ring structures.

19. The propulsion method of claim 17, wherein the means for controlling exposure comprises a configuration of the ring structures as a set of circumferentially arranged shingles that permits pivoting of the specified angle of the shingles and facing of the coating of deuterium-containing micro-fusion fuel material inwards for storage.

20. A spacecraft propulsion method for use in the presence of an ambient flux of cosmic rays, comprising: an ion thruster that is electrically powered; and a micro-fusion-driven turbine generator coupled to provide electricity to the ion thruster, wherein the micro-fusion-driven turbine generator includes a source of deuterium-containing micro-fusion particle fuel material coupled to a flue for dispersing the micro-fusion particle fuel material into a volume, and a set of two or more helium-wind turbines arranged around the volume, wherein cosmic rays entering the volume interact with the dispersed fuel material to cause nuclear micro-fusion events, kinetic-energy-containing micro-fusion products driving the helium-wind turbines.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a side plan view of a spacecraft shooting projectiles along a trajectory that disperses a cloud of micro-fusion fuel for reaction with cosmic rays and muons according to the present invention.

[0028] FIG. 2 is a front-end view of the spacecraft of FIG. 1 that illustrates an arrangement of projectile guns housed around a circumference of the spacecraft.

[0029] FIG. 3 is side plan view of a spacecraft with an alternative propulsion method in which micro-fusion fuel material is coated upon a set of angled ring structures surrounding the outer shell of the spacecraft.

[0030] FIG. 4A is a side plan view of a spacecraft towing a set of turbine electric generators outside of the craft, where the generators are powered by reaction of ambient cosmic rays and muons with a dispersed cloud of micro-fusion fuel.

[0031] FIG. 4B is an enlarged sectional view of one turbine electric generator from FIG. 4A.

[0032] FIG. 5 is a graph of cosmic ray flux at the Earth surface versus cosmic ray energy.

DETAILED DESCRIPTION

[0033] The goal of the invention is to shorten the travel time to Mars or other planets and their moons (to reduce cumulative radiation doses to which the astronauts are subject) and likewise to provide a continuous acceleration to offset or reduce weightlessness during the journey. Cosmic ray flux naturally present in interstellar space is used to power nuclear micro-fusion events (via particle-target micro-fusion and muon-catalyzed micro-fusion) that will propel the spacecraft, as well as generate electrical energy. In another version, solar cells on the spacecraft exterior may be used to power an ion thruster for propulsion. Avoiding a weightless coasting phase of an interplanetary trajectory accomplishes the goal of both shorter travel times and providing an artificial gravity via the accelerating or decelerating thrust of the spacecraft.

[0034] Ideally, the amount of continuous acceleration or deceleration (artificial gravity) will be sufficient to prevent or minimize the adverse health effects that would otherwise occur from long-term weightlessness. How much acceleration/deceleration might be needed may depend on factors still to be quantified by further research aboard platforms like the International Space Station, including the duration of the flight, but a magnitude that is at least some specified portion (e.g., at least 25% and preferably at least 40%) of the gravitation at the target planet or moon should be the objective. For example, the amount of acceleration could be chosen to equal that of the destination planet or moon (about 0.38 G for Mars), so that astronauts will be ready for work upon arrival, without the need for an extensive recuperation period to adjust to the gravitational force encountered at the destination. Likewise, the return journey from Mars could have a thrust that gradually builds up from 0.38 G at departure, so that recovery times are reduced upon arrival with Earth. For some space voyages, the weightlessness might only be reduced rather than eliminated.

[0035] With reference to FIG. 1, one propulsion technique is to project the micro-fusion target material in a specified direction outward from a spacecraft 11, i.e. along its intended trajectory (generally behind the spacecraft for acceleration, and ahead of the spacecraft for deceleration). The micro-fusion fuel can be solid Li.sup.6D in powder form, D-D or D-T inertial-confinement-fusion-type pellets, D.sub.2O ice crystals, or droplets of (initially liquid) D.sub.2. For example, one may shoot fuel packages (chips, pellets, powder) loaded in a series of projectiles 13, e.g. once every minute, or once per second for very large spacecraft, which can then disperse the micro-fusion material as a localized cloud 15, much like fireworks or artillery from an antiaircraft gun. The spacecraft propulsion system works in the presence of an ambient flux 16 of cosmic rays and/or muons which interact with the cloud 15 and trigger the nuclear micro-fusion of the particle target material, either by particle-target micro-fusion or muon-catalyzed micro-fusion or both. Fusion products having significant kinetic energy (e.g. alpha particles) are generated and are received at some portion of the spacecraft (e.g. the flat nose 17, a much larger diameter disc on the flat nose 17, the larger diameter forward surface of the gun 23 mounted around the spacecraft, or some other pusher arrangement, like those described in Projects Orion, Daedalus, or Longshot) to produce thrust upon the spacecraft 11. The thrust results in continuous acceleration (or deceleration) of the spacecraft with a specified trajectory. The acceleration or deceleration is experienced by the astronaut crew as artificial gravity.

[0036] Stored fuel packages will be shielded, at least within the casing of the projectiles themselves, to reduce or eliminate premature fusion events until delivered and dispersed as a cloud behind the spacecraft (for acceleration) or in front of the spacecraft (for deceleration). An inter-planetary astronaut crew will itself need shielding from radiation (which can cause brain damage and other adverse health effects). Therefore, the crew's shielding could double as a shield for the fuel packages. One important source of such shielding will be the spacecraft's water supply, which should be adequate for the task. One need not eliminate cosmic rays or their secondary particles (pions, muons, etc.) to zero, but merely reduce their numbers and energies sufficiently to keep them from catalyzing sufficiently large numbers of fusion events in the stored target particle material. Additionally, since the use of micro-fusion fuel is expected to reduce the required amount of chemical rocket propellant by a factor of about two, one can easily afford the extra weight of some small amount of metal for shielding, if needed. (For example, the Juno spacecraft to Jupiter contains radiation vaults of 1 cm thick titanium to shield its electronics from external radiation. A similar type of vault might be used in this case for the shielding of the stored fuel.) After being shot from the spacecraft, the casing of the projectiles themselves will continue to provide some shielding until dispersal of the target particle material as a cloud.

[0037] FIG. 2 shows the front-end view of a set of fuel projectile guns 21 (here four in number, labeled A-D, as an example, although the Mars Colonial Transporter could house 100 of them) located in a housing 23 surrounding a circumference of the shell 25 of the spacecraft 11. The flat nose 17, a large disc covering it, or other mechanism of the spacecraft for receiving the kinetic-energy-containing fusion products can also be used.

[0038] Soon after the projectile has reached a desired distance from the spacecraft the fuel package releases its particle target material. For example, a chemical explosion can be used to locally disperse the micro-fusion material. The dispersed cloud of target material will be exposed to both cosmic rays and especially during landing to their generated muons. As cosmic rays collide with micro-fusion targets and dust, they form muons that are captured by the deuterium and that catalyze micro-fusion. Likewise, the cosmic ray collisions themselves can directly trigger particle-target micro-fusion. In order to assist muon formation for muon-catalyzed fusion, especially when D.sub.2O or D.sub.2 is used, the target package may contain up to 20% by weight of added particles of fine sand or dust.

[0039] 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 Li.sup.6-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% Li.sup.6, with most samples falling around 7.4% to 7.6% Li.sup.6. Although LiD that has been made from natural lithium sources can be used in lower thrust applications or to inhibit a runaway macro-fusion event, fuel material that has been enriched with greater proportions of Li.sup.6 is preferable for achieving greater thrust and efficiency.

[0040] The micro-fusion reaction creates successive miniature suns, a kind of external combustion that will provide thrust against the spacecraft for braking or accelerating. Even the photon radiation applies pressure to help decelerate the spacecraft. However, the amount of energy generated depends upon the quantity of fuel released and the quantity of available cosmic rays and muons. Assuming most of the energy can be captured and made available for thrust, an estimated 10.sup.15 individual micro-fusion reactions (less than 1 ?g 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 rocket thrust purpose following research, development, and engineering efforts. The fusion-powered thrust may be supplemented or replaced for certain portions of the journey (e.g. from launch to Earth orbit) with chemical rocket engines.

[0041] A piston area extension may be supplied around the perimeter of the spacecraft for increased thrust during accelerating and braking, and for storage and delivery of the micro-fusion fuel projectiles or shells using a set of four or more guns that fire the projectiles forward or backward from the vehicle. The spacecraft effectively acts as the equivalent of a piston in an external combustion engine and the volume of the continuous slow micro-fusion creates high velocity fusion products (alpha particles, etc.) that bombard the front of the spacecraft and its piston area extensions. The needed of firing depends on the amount of deceleration required, the amount of fusion obtained from the ambient cosmic ray and/or muon flux, the dispersal rate of the fuel cloud from in front of the craft, and the efficiency. of the transfer of the fusion products into thrust, but could be expected to be as much as one shell every few seconds for some spacecraft and one shell per second for the largest spacecraft for the duration of the accelerating or braking period. A large diameter flat nose cap can be mounted on the front of the spacecraft to increase the efficiency of thrusting for accelerating and braking.

[0042] Additionally, it may be possible to generate electrical or magnetic fields, e.g. by charging the piston area extensions or large diameter flat disc, or by magnetizing the same or the spacecraft as a whole, to help steer cosmic rays toward the fusion fuel particle cloud (and away from astronaut crew areas) or to focus the electrically charged, high velocity helium nuclei fusion products onto the spacecraft's thrusting surfaces. This will increase thrust efficiency by capturing a greater portion of the kinetic-energy-bearing fusion products.

[0043] With reference to FIG. 3, in yet another embodiment, the spacecraft 31 may have a set of ring structures 33 arranged around the outside of the spacecraft and which are oriented at 45? to the length of the spacecraft and direction of thrust. These ring structures 33 are coated with the micro-fusion target material 35, such as chips of lithium-6 deuteride, or deuterium-containing capsules, pellets or powder. As the fuel-coated rings 33 are exposed to cosmic rays 37, micro-fusion events are initiated and the fusion products (fast helium nuclei) propel the spacecraft 31, continuously generating an accelerating or decelerating thrust. Additionally, the collisions of cosmic rays with the surface of the fuel-coated ring structures 33 will also generate muons that will further catalyze micro-fusion of the fusion material 35.

[0044] The amount of thrust might be controlled by shielding (or withdrawing shielding from) a specified number of the rings 33. Such shields 36 may be slid in or out through corresponding slots in the outer shell 39 of the spacecraft 31 to cover the coating 35 on the rings 33. Alternatively, the fuel-coated rings might be pivoted to different angles relative to the length of the spacecraft. For that purpose, the rings would not be a unitary structure but a set of individual shingles arranged around the circumference of the spacecraft. Pivoting such shingles, would also allow the rings to be turned with the micro-fusion fuel coating facing inward when shielded storage is desired.

[0045] In a further embodiment shown in FIGS. 4A and 4B, the spacecraft 40 may have a series of turbine electric generators 41 attached to its exterior via cables 43, where the turbines are driven by the fast helium nuclei micro-fusion products generated from dispersed lithium-6 deuteride or other deuterium-containing micro-fusion target material exposed to the cosmic rays. Alternatively, instead of having cables 43 trailing the spacecraft, the turbine electric generators 41 might be mounted on a narrow metal web as long as about five space-crafts, with the spacecraft located in the center. Micro-fusion fuel packages would be delivered to the vicinity of each of the turbines, however those turbines are mounted or located relative to the spacecraft. The turbines can generate electricity for powering the spacecraft or for powering an ion thruster. Likewise, a set of solar panels covering the exterior of the spacecraft could generate electricity for powering the spacecraft or ion thruster.

[0046] In FIG. 4B, one such turbine electric generator 41 is seen. A cloud of deuterium-containing micro-fusion target fuel 43, e.g. particles of Li.sup.6D, is dispersed from a flue 44 into a volume 45 between two or more helium-wind turbines 47. High-energy cosmic rays 49 entering the volume 45 interact with the micro-fusion target fuel material 43 to cause nuclear fusion events. Fusion products, mainly high energy helium nuclei (alpha particles), direct kinetic energy to the turbine blades to turn the turbines 47 and generate electricity.

[0047] Ion thrusters are currently in use by NASA for a variety of geosynchronous satellites, as well as for the Dawn spacecraft (launched in 2007) for exploring the asteroid belt (including Ceres and Vesta). In an ion thruster, propellant (e.g. xenon) is ionized by electron bombardment to create a plasma and the positive ions in the plasma are then accelerated from the thruster chamber to produce thrust. Whether powered by solar cells or as describe here for fusion-driven turbine generators, a sufficient reserve of propellant will be needed for the length of both the outgoing and return journeys.

[0048] While the embodiment of the present invention described herein only utilizes thrust created by the kinetic energy of helium nuclei micro-fusion products that directly bombard the spacecraft, other embodiments may create thrust via the helium nuclei micro-fusion products impacting outboard parachutes or sails connected to the craft, thereby capturing kinetic energy of micro-fusion products moving away from the spacecraft.