Spacecraft collision-avoidance propulsion system and method

Abstract

A collision-avoidance propulsion system and method for orbiting satellites and other spacecraft takes advantage of ambient cosmic rays in space to catalyze micro-fusion events via particle-target fusion and muon-catalyzed fusion processes, using the reaction products to produce thrust upon orbiting satellites and other spacecraft. A supply of deuterium-containing particle fuel material is propelled in a specified direction of the spacecraft in response to indication of a potential collision with another space object (e.g. orbiting debris). In one embodiment, this may be performed by propellant gas expelling the fuel material through conduits to specified ports on the exterior of the spacecraft. The propelled material interacts with the ambient cosmic rays and muon generated from those cosmic rays to induce micro-fusion. A portion of the energetic reaction products (e.g. alpha particles) are received upon the spacecraft to alter its trajectory in a manner that avoids the potential collision.

Claims

1. A spacecraft collision avoidance propulsion system for use in the presence of an ambient flux of cosmic rays, comprising: a supply of deuterium-containing particle fuel material; a store of pressurized propellant, with valves responsive to a received indication of a potential collision with a space object, for projecting the deuterium-containing particle fuel material in a specified direction outward from a spacecraft, the projected material interacting with the ambient flux of cosmic rays to generate products having kinetic energy, the spacecraft receiving at least some portion of the generated kinetic-energy-containing products to produce thrust upon the spacecraft to provide a change of trajectory of at least a dimension of the spacecraft to avoid the indicated potential collision.

2. The propulsion system as in claim 1, wherein the spacecraft is in an orbit around a planet or moon.

3. The propulsion system as in claim 1, wherein the space object is orbiting debris.

4. The propulsion system as in claim 1, wherein the space object is another spacecraft.

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

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

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

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

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

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

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

12. The propulsion system as in claim 1, wherein the deuterium-containing particle fuel material also contains up to 20% by weight of added non-fuel powder or dust particles.

13. A method of spacecraft propulsion for use in the presence of an ambient flux of cosmic rays for collision avoidance, comprising: projecting with pressurized propellant, through valves responsive to a received indication of a potential collision with a space object, deuterium-containing particle fuel material in a specified direction outward from a spacecraft, the projected 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 to provide a change of trajectory of at least a dimension of the spacecraft to avoid the indicated potential collision.

14. The method as in claim 13, wherein the spacecraft is in an orbit around a planet or moon.

15. The method as in claim 13, wherein the space object is orbiting debris.

16. The method as in claim 13, wherein the space object is another spacecraft.

17. The method as in claim 13, wherein the deuterium-containing particle fuel material is Li.sup.6D.

18. The method as in claim 13, wherein the deuterium-containing particle fuel material is D.sub.2O.

19. The method as in claim 13, wherein the deuterium-containing particle fuel is D.sub.2.

20. The method as in claim 13, wherein the deuterium-containing particle fuel material is in solid powder form.

21. The method as in claim 13, wherein the deuterium-containing particle fuel material is in pellet form.

22. The method as in claim 13, wherein the deuterium-containing particle fuel material is in frozen form.

23. The method as in claim 13, wherein the deuterium-containing particle fuel material is in liquid droplet form.

24. The method as in claim 13, wherein the deuterium-containing particle fuel material also contains up to 20% by weight of added non-fuel powder or dust particles.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of a satellite or other spacecraft containing an embodiment of a collision-avoidance propulsion system in accord with the present invention.

(2) FIG. 2 is a sectional view taken along the direction 2-2 in FIG. 1 showing the interior of an embodiment of the collision-avoidance propulsion system.

(3) FIG. 3 is a graph showing cosmic ray flux distribution (versus cosmic ray energies) at the Earth's surface.

DETAILED DESCRIPTION

(4) With reference to FIG. 1, one technique is to project the fusion target material outward from a spacecraft 11. In the example shown, the spacecraft 11 is a satellite, but other types of spacecraft can also have need of collision-avoidance propulsion systems. The satellite 11 can be powered by solar panels 15 (or alternatively, some internal power source) for its primary mission needs, but also for space object detection and external communication for ground-based collision warning. When an indication of an impending potential collision is detected or received, the collision-avoidance propulsion system will be activated to supply a desired change in trajectory to the satellite or other spacecraft 11.

(5) For this purpose, 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. When thrust is needed, one shoots fuel pellets 21 as a series of projectiles, e.g. once per second. Alternatively, the fuel can be a propellant gas mixed with micro-fusion fuel powder 19 that can then disperse as a localized cloud 20. The fuel is seen leaving the spacecraft 11 through one or more ports 17 on its exterior. The fuel pellets 21 or dispersed cloud of target material 19 will be exposed to both cosmic rays 13 and to their generated muons. The spacecraft propulsion 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 fusion or muon-catalyzed fusion or both. As cosmic rays 13 collide with micro-fusion targets 19 and 21 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 in the vacuum of space, especially when D.sub.2O is used, the target package may contain up to 20% by weight of added non-fuel powder or fine dust particles in the mixture. Fusion products () having significant kinetic energy are generated and are received at some portion of the spacecraft 11 to produce thrust upon the spacecraft.

(6) With reference to FIG. 2, inside the satellite or other space craft, micro-fusion fuel material 21 is stored in a shielded radiation vault 31 until needed. Stored fuel will be shielded to reduce or eliminate premature fusion events until they are to be delivered to outside of the spacecraft. 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 31 could be used in this case for the shielding the stored fuel.

(7) One way to project the micro-fuel out of the spacecraft is to employ a type of air-gun mechanism using a store 35 of chemical propulsion gases (e.g. xenon; but lighter substances such as butane or carbon dioxide might also be used) already being used for orbital station-keeping. Here, the quantities needed would be significantly smaller due to the additional thrust provided by the added micro-fusion fuel. In one possible embodiment, the supply 35 of propulsion gas may be connected through a valve 37 and conduit 39 to the vault 31 containing micro-fusion fuel material 21, expelling some of that fuel along with propellant gas through conduits 33 and 34 with respective valves 43 and 44. Valves 37 is opened to load the vault 21 with a quantity of pressurized propellant gas from store 35. A selected one of the valves 43 and 44 is opened to expel a quantity of propellant and micro-fusion material through one of the ports 17 in the spacecraft.

(8) Micro-fusion fuel targets (typically in small solid pellet, frozen ice, or powder form) when shot or otherwise projected externally from the spacecraft will interact with the flux of cosmic rays and muons such that some combination of particle-target micro-fusion and/or muon-catalyzed micro-fusion will take place, generating a thrust against the vehicle. The deuterium fuel for the particle-target and/or muon-catalyzed micro-fusion may be supplied in the form of solid Li.sup.6D, or even heavy water (D.sub.2O). Muon-created 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, fusion proceeds extremely rapidly (on the order of 10.sup.10 sec). Other types of micro-fusion reactions besides D-D are also possible depending upon the target material. For example, another reaction is Li.sup.6+D.fwdarw.2He.sup.4+22.4 MeV, where much of the useful excess energy is carried as kinetic energy of the two helium nuclei (alpha particles). One cosmic ray particle can generate hundreds of muons, and each muon can typically catalyze about 100 micro-fusion reactions before it decays (the exact number depending on the muon sticking cross-section to any helium fusion products).

(9) Additionally, cosmic rays can themselves directly stimulate a micro-fusion event by particle-target fusion, wherein the high energy cosmic ray particles (mostly protons, but also helium nuclei) bombard relatively stationary target material. 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. Although D-D micro-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 micro-fusion energy output for practical use.

(10) The present invention achieves nuclear micro-fusion using deuterium-containing target material, and the ambient flux of cosmic rays and generated muons that are already naturally present in the space environment. The optimum concentration of the 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 billions of micro-fusion events for producing adequate thrust for the specified application, while avoiding any possibility of a runaway macro-fusion event.

(11) At a minimum, since both particle-target micro-fusion and muon-catalyzed micro-fusion, while recognized, 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 (e.g. on satellite platforms). Later, the concept can be extended to environments beyond Earth's magnetic field, e.g. in orbit around the Moon, Mars, or other planets or their moons in order to determine optimum parameters for various utilities in those environments. For example, the actual number of fusion reactions for various types of micro-fusion fuel sources and target configurations, and the amount of rocket thrust 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 space vehicle requires strong cosmic ray flux to create sufficient nuclear micro-fusion for thrust purposes.

(12) 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.

(13) The micro-fusion reaction creates a kind of external combustion in the form of micro-fusion events resulting in production of energetic reaction products that will provide thrust against the spacecraft for altering its velocity and trajectory. 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 about 100 reactions, the available cosmic ray flux in space is believed to be sufficient for this rocket thrust purpose following research, development, and engineering efforts.