Patent Application
20160290324
The present invention relates to systems and methods for improving plasma propellant ablation/sublimation based systems. In particular, embodiments can include improved methods and apparatuses associated with plasma pulsed thruster (PPT) including reduction of carbon charring during ablation of a carbon-fluorine polymer as well as increasing thrust, heat transfer, and ablation of the propellant.
Carbon-fluorine (C2F4)n based polymers can be used as a dielectric propellant material in different types of PPTs. In PPTs, an electrical potential difference can be applied between a cathode and anode separated by the dielectric propellant. Current flows across the surface of the propellant, ablating and sublimating the propellant. Heat can be generated by the potential difference causing the propellant to create plasma. The plasma is charged, and the propellant completes the circuit between the cathode and anode allowing current to flow through the plasma. The flow of electrons between the anode and cathode can generate a strong electromagnetic field, which can exert a Lorentz Force on the plasma. The plasma is accelerated away from the propellant due to the Lorentz force. Inspection of the PPT propellant surface after firing show signs of carbon charring and ablation near the electrodes, which can cause failure of the PPT due to a low energy-to-thruster radius ratio. This charring can be formed primarily from carbon, which can result in a carbon flux to be returned from the plasma rather than from the incomplete decomposition of the propellant.
According to an illustrative embodiment of the present disclosure, systems and methods for improving plasma propellant ablation/sublimation based systems are provided. One set of embodiments provides systems and methods for reducing carbon charring during plasma system (e.g., a plasma coating application system) propellant (e.g., a carbon-fluorine polymer) ablation and increasing heat transfer, ablation, and plasma thrust from plasma system. In particular, one embodiment can include using a nano or micro-sized magnetic or electromagnetic field responsive material as particulates or microcapsules that are intermixed with, e.g., polytetrafluoroethylene (e.g., Teflon®) nano-fibers, and using resulting fiber composites as the propellant material. Embodiments include improved plasma system, e.g., PPTs, plasma torch, plasma coating system, etc, as well as nozzle improvements such as embodiments with magnetic structures disposed in relation to the nozzle.
Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.
The detailed description of the drawings particularly refers to the accompanying figures in which:
The embodiments of the invention described herein are not intended to be exhaustive or to limit the invention to precise forms disclosed. Rather, the embodiments selected for description have been chosen to enable one skilled in the art to practice the invention.
Referring initially to
In one exemplary operation, an anode 102 is spaced apart from a cathode 104. A propellant 106 is located between the anode 102 and the cathode 104. The anode 102 can include a protruding edge to hold the propellant 106 in place. The spring 118 can provide a constant pressure on an exemplary propellant 106 in order to keep the propellant 106 pressed against the protruding edge of the anode 102. The power supply 108 is electrically connected to the anode 102 and the cathode 104 and can be used to apply an electrical potential difference between the anode 102 and the cathode 104. The capacitor 114 is connected in parallel with the voltage source 108 and anode 102 and cathode 104. The capacitor 114 protects the voltage source from large charge dumps caused by transient arcs between the anode 102 and cathode 104. The igniter device 116 can provide a large supply of free electrons to aid in the formation of plasma between the anode 102 and cathode 104. An electric potential difference between the anode 102 and the cathode 104 can cause an electrical current to flow across the surface of the dielectric propellant 106. The electrical current can cause ablation and sublimation of the propellant. Plasma 112 can be formed between the anode 102 and cathode 104. The plasma 112 is ejected away from the propellant 106 by a Lorentz force 112.
In the present embodiment, the dielectric propellant 106 is Teflon® that can include a plurality of magnetic nanoparticles dispersed throughout the dielectric propellant 106. In an alternative embodiment, the dielectric propellant 106 can be any carbon-fluorine based polymer (C2F4)n which can include for example, a plurality of magnetic nanoparticles dispersed throughout the dielectric propellant 106. In an alternative embodiment, the dielectric propellant 106 can include a plurality of magnetic microparticles. In an alternative embodiment, the dielectric propellant 106 can include a plurality of particles that are responsive to magnetic or electromagnetic fields, such as, for example, magnetic particles, ferromagnetic particles, diamagnetic particles, dielectric compounds of oxides or sulfides, or metal powders, such as copper, gold, or the like.
The presence of magnetic nanoparticles in the dielectric propellant 106 reduces the amount of carbon in the dielectric propellant 106, which can reduce the amount of carbon charring on the surface of the dielectric propellant 106. Additionally, the magnetic nanoparticles can have a higher thermal conductivity than the dielectric propellant 106, which can allow for better heat transfer and a higher rate of ablation. Higher ablation rates combined with the larger electrical conductivity of the magnetic nanoparticles can increase the electrical current density between the anode and cathode. Increasing the electrical current density can increase the Lorentz force and increase the thrust resulting from ejection of the plasma 112.
In certain embodiments, the Lorentz force can be further enhanced by affixing magnets to the PPT nozzle's exit to increase the magnetic field between the anode 102 and cathode 104.
Referring to
In the present embodiment, Teflon® with magnetic nanoparticles is used as a dielectric propellant in a pulsed plasma thruster. However, in alternative embodiments, carbon-fluorine based polymer with magnetic nanoparticles may be used in any system that ablates a dielectric material, such as a plasma torch, a weapon to release chemically active or toxic gases, substrate coating systems, heat treatment systems, etc.
Referring to
Note that an exemplary method embodiment can add a step of providing magnets along a pulse plasma thruster nozzle exit, creating additionally thrust from the pulsed plasma thruster. An exemplary pulsed plasma thruster comprises a plurality of magnets that can be formed around the inner diameter of the pulsed plasma thruster's exit nozzle. The magnets can be used to direct or accelerate plasma. The magnets can be electromagnets to selectively adjust magnetic fields in order to alter a shape of the plasma output exiting from the nozzle. This can be used to alter, for example, diameter of plasma or to engage in adjustments to the plasma such as used with additive manufacturing (e.g. sputtering).
Plasma generation control systems can also adjust operation of a plasma generator, e.g. PPT, so that it operates or ablates on an intermittent basis which can be used to adjust output applied to a work piece in a manner that permits skipping or selective application of plasma output. Another alternative embodiment can include providing a nano or micro particle injector which also can vary content of the plasma as it is ablated which adjusts particle application to a workpiece. Embodiments can include providing and operating the nano or micro particle injector so as to be configured to inject one or more additional or different said particles into said plasma so as to vary particle content of the plasma during and after ablation which adjusts said particle type and concentration. Additional particles can be inserted into the plasma which can be used as a variable additive manufacturing system for a work piece e.g. a coating system or a system which produces additional interactions with the workpiece where the particles cause a chemical reaction with the workpiece, coat the work piece, etc.
An alternative embodiment can include providing one or more electromagnetic field generating sections along the plasma's path from ablation to the nozzle's exit that which is configured for generating an applied electric field that applies a propulsive force to the plasma and its electromagnetic sensitive particles to increase or adjust speed of the plasma towards the nozzle's exit path and push them away from the anode/cathodes. This field application provides a dual benefit of increasing plasma speed and also preventing or hindering the plasma from coating the anode or cathode and thereby damaging or clogging the plasma generator.
An alternative embodiment can be as a part of a material recovery and reuse system used in various application including environmentally sensitive applications as well as space applications. One embodiment can use a scoop system which pulls or manipulates the electromagnetic field sensitive particles out of the plasma's thrust path and then recycles them back to the plasma thrust chamber which then permits reuse of the particles. A system for transferring the particles back to a storage/reuse chamber can include additional electromagnetic field drift tubes. Fan systems can also be used to move recovered material within the material recovery and reuse system. Recovery and reuse systems can include tubing and other structures which route the particles, store them for reuse, and then re-inject them back into, e.g., the PPT. The particles in some embodiments would include coatings of the carbon polymer material that is resistant to ablation and material destruction. Another embodiment can include, for example, a system can include a portion that travels down a desired route of travel between two points laying out or spraying material that is used in as the propellant for the plasma system that includes the magnetic or electromagnetic sensitive particles. A second section can be a spacecraft that has an electromagnetic field generator on a front end ram scoop which then channels the laid out or sprayed material which the ram scoop collects and then utilizes in the PPT system. A combination of these two embodiments can also be used. A laying or spray vehicle path can be determined based on factors such as expected orbital path, impact of solar wind, volume needed for PPT operation and speed of spacecraft, etc. A laying or spray vehicle could include a cryogenic system or merely freezing the polymer/particle material and permitting solar winds or even solar concentrators on the spray or laying vehicle to melt or vaporize the material in a desired density in a manner similar to a comet ejection. A spray or laying vehicle can use a solar sail to maneuver along orbital paths using solar winds from the sun as a motive force given it does not need to be as fast as a following vehicle.
Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the spirit and scope of the invention as described and defined in the following claims.
The present application claims priority to U.S. Provisional Patent Application Ser. No. 62/143,319, filed Apr. 6, 2015, entitled “SYSTEMS AND METHODS FOR IMPROVING PLASMA PROPELLANT ABLATION/SUBLIMATION BASED SYSTEMS INCLUDING REDUCTION OF CARBON CHARRING DURING ABLATION OF A CARBON-BASED POLYMER AS WELL AS INCREASING THRUST, HEAT TRANSFER, AND ABLATION,” the disclosure of which is expressly incorporated by reference herein.
The invention described herein was made in the performance of official duties by employees of the Department of the Navy and may be manufactured, used and licensed by or for the United States Government for any governmental purpose without payment of any royalties thereon. This invention (Navy Case 200,222) is assigned to the United States Government and is available for licensing for commercial purposes. Licensing and technical inquiries may be directed to the Technology Transfer Office, Naval Surface Warfare Center Crane, email: Cran_CTO@navy.mil.
| Number | Date | Country | |
|---|---|---|---|
| 62143319 | Apr 2015 | US |
