INTERPLANETARY SPACECRAFT USING FUSION-POWERED THRUST

Abstract

A spacecraft propulsion system operated in the presence of an ambient flux of cosmic rays is provided, wherein the cosmic rays interact with deuterium-containing nuclear micro-fusion fuel material to generate products having useful kinetic energy. The propulsion system comprises a supply of the deuterium-containing particle fuel material, along with means (such as a gun) for projecting the material (e.g. as successive packages in the form of shell projectiles) outward from a spacecraft. The spacecraft has means (such as a pusher mechanism) for receiving at least some portion of the generated kinetic-energy-containing products to produce thrust upon the spacecraft.

Claims

1. A spacecraft propulsion system for use in the presence of an ambient flux of cosmic rays, comprising: a supply of deuterium-containing particle fuel material; means for projecting the deuterium-containing particle fuel material outward from a spacecraft, the material interacting with the ambient flux of cosmic rays to generate products having kinetic energy; and means on the spacecraft for receiving at least some portion of the generated kinetic-energy-containing products to produce thrust upon the spacecraft.

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

3. The propulsion system as in claim 1, wherein the deuterium-containing particle fuel material comprises D.sub.2O.

4. The propulsion system as in claim 1, wherein the deuterium-containing particle fuel material comprises D.sub.2.

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

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

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

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

9. The propulsion system as in claim 1, wherein the deuterium-containing particle fuel material is projected outward from the spacecraft as successive packages.

10. The propulsion system as in claim 9, wherein the packages are shell projectiles shot from at least one gun forming a part of the spacecraft.

11. The propulsion system as in claim 9, wherein each package is configured to disperse the deuterium-containing particle fuel material as localized cloud at a specified distance from the spacecraft.

12. The propulsion system as in claim 11, wherein dispersal of the deuterium-containing particle fuel material is by means of chemical explosive comprising a part of the package.

13. The propulsion system as in claim 9, wherein the packages also contain up to 20% by weight of added particles of fine sand or dust.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is a side plan view of a spacecraft shooting projectiles along a trajectory that disperse a cloud of micro-fusion fuel material for reaction with cosmic rays and muons according to the present invention.

[0023] 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.

[0024] FIG. 3 is a graph of cosmic ray flux at the Earth surface versus cosmic ray energy.

DETAILED DESCRIPTION

[0025] With reference to FIG. 1, one technique is to project the fusion target material outward from a spacecraft 11. A supply of deuterium-containing micro-fusion fuel material is provided, which 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. One shoots fuel packages as a series of projectiles 13, e.g. once every minute or once per second, 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 and trigger the nuclear micro-fusion of the particle target material, either by particle-target fusion or muon-catalyzed fusion or both. Fusion products having significant kinetic energy 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.

[0026] Stored fuel packages will be shielded to reduce or eliminate premature fusion events until they are to be delivered in front of (or in the case of acceleration, behind) the spacecraft. 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 at least a factor of 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 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.

[0027] 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 a spacecraft like 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 seen.

[0028] Soon after the projectile has reached the 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 fusion. Likewise, the cosmic ray collisions themselves can directly trigger particle-target micro-fusion. In order to assist muon formation, 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. (This is particularly important if one desires to create a similar fusion reaction in interplanetary space, or over the Moon, which has no atmosphere.)

[0029] 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 runaway macro-fusion events, fuel material that has been enriched with greater proportions of Li.sup.6 is preferable for achieving greater thrust and efficiency.

[0030] 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 lag 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 about 100 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.

[0031] 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 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 once per second for the largest spacecraft for the duration of the accelerating or braking period. A large diameter flat disc can be mounted on the nose cap 17 at the front of the spacecraft to increase the efficiency of thrusting for braking and accelerating.

[0032] 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.

[0033] 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.