Patent Application
20220041522
Missiles and rockets burn propellants within combustion chambers to generate pressurized gases. The pressurized gases are directed through a nozzle to provide thrust and accordingly propel the body of the missile or rocket.
Solid rocket propellants are formed with a solid oxidizer, for instance ammonium perchlorate, fuels, additives, and binders. Ignition systems that elevate the temperature of the solid rocket propellant to the point of combustion are used to ignite the solid rocket fuel.
After ignition of a solid rocket motor, the reaction generally cannot be interrupted until the fuel is completely consumed, and solid rocket propellant burns according to the shape of the propellant grain the propellant burn rate and its operating pressure, which is dictated by the nozzle throat size. Thus, the burn rate of the fuel proceeds according to a set of predefined parameters that generally cannot be changed during launch and/or flight.
Some solid propellants can be electrically controlled propellants that are ignitable and extinguishable under a variety of conditions, including under high pressures within a rocket motor combustion chamber. Such electrically operated propellants can be selectively ignited and extinguished over a broad range of conditions, which facilitates the selective generation of thrust for a variety of applications, for example, to control to a vehicle without consuming the entirety of the propellant at one time.
According to embodiments of the present invention, an electrically operated propellant includes an electrolyte source. The electrolyte source is an ionic liquid, a polyelectrolyte, or a combination thereof. The electrically operated propellant also includes a polymeric binder. The electrically operated propellant is substantially waterless with a water content of less than 10 wt. % water based on total weight of the electrically operated propellant.
According to other embodiments of the present invention, an electrically operated propellant includes an electrolyte source. The electrolyte source is a polymer with a plurality of electrolyte groups. The electrically operated propellant further includes a polymeric binder. The electrically operated propellant is substantially waterless with a water content of less than 10 wt. % water based on total weight of the electrically operated propellant.
Yet, according to other embodiments of the present invention, a method of making an electrically operated propellant includes combining an electrolyte source and a polymeric binder to form a propellant composition. The electrolyte source is an ionic liquid, a polyelectrolyte, or a combination thereof. The method further includes forming the propellant composition into a solid propellant configuration. The electrically operated propellant is substantially waterless with a water content of less than 10 wt. % water based on total weight of the electrically operated propellant.
Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the invention with the advantages and the features, refer to the description and to the drawings.
For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts:
Electrically operated propellants can be controlled (ignited, extinguished, and throttled) using an electrical signal provided by one or more configured electrodes. For example, applying a voltage across the electrodes ignites the propellant, and conversely, the interrupting the voltage extinguishes the propellant. In a rocket motor, it may be desirable to throttle or interrupt the burn of the electrically operated propellant during vehicle flight in order to control the rocket motor burn during different flight events in order to accomplish a desired mission in a variable environment.
Generally, electrically operated solid propellants include a perchlorate oxidizer, a metal fuel, a polymeric binder, and a solvent. Water has most commonly been used to solubilize the polymeric binder and form an aqueous solution with the additional propellant ingredients.
One challenge of using electrically operated propellants, in a significantly cold space propulsion application scenario, for example, is that the water used to form aqueous solutions can boil, due to the pressure drop, or freeze, due to the low temperatures, if exposed directly to a space environment. Even if the water in the propellant is not directly exposed to the space environment, the included water ingredient poses an overall issue due to the significantly high and/or low temperature and pressure exposure in space. Risks of the water in the electrically operated propellants include potentially rendering the propellant inoperable are therefore undesirable for space applications.
Similarly, the water in electrically operated propellants that are used in other applications, such as in airbag inflators, presents challenges because including volatile components in the formulation that could be labile are problematic. This volatility makes using electrically operated propellants with significant quantities of water challenging, as water content verification and continuous absorption and loss of water despite manufacturing, storage, and use in controlled environments pose additional water related issues.
Additionally, long term storage of an electrically operated propellant with a water ingredient is challenging, as water may interact with other materials, the propellant, rocket motor, and/or flight vehicle. Further, water presents challenges with respect to with propellant relaxation out of the desired propellant shape, oxidations, as well as material compatibility with additional materials used in the rocket motor build.
Accordingly, one or more aspects of the present invention address the above-described shortcomings by providing electrically operated propellants and methods of making and using electrically operated propellants, which are substantially waterless in some embodiments, and waterless in other embodiments. In one or more aspects of the present invention, the electrically operated propellants include an electrolyte source, a metal fuel, a polymeric binder, and optionally, a perchlorate oxidizer, with the electrolyte source being an ionic liquid, a polyelectrolyte, or a combination thereof. In other aspects of the present invention, the electrically operated propellants include an electrolyte source, a metal fuel, a polymeric binder, and optionally, a perchlorate oxidizer, with the electrolyte source being a polymer with a plurality of electrolyte groups.
Aspects of the present invention provide various advantages. Water is reduced or completely eliminated in electrically operated propellant compositions. Further, any aqueous solvents, such as water, which are required for water soluble binders (e.g., casein, methyl cellulose, polyethylene oxide, polyvinyl acetate, and polyvinyl alcohol) are replaced by a non-aqueous solvent(s), which includes one or more of an ionic liquid, polyelectrolyte, or polymer with a plurality of electrolyte groups. The non-aqueous compositions eliminate the risk of water rendering the propellant inoperable when exposed directly or indirectly to a space environment in a space propulsion application (e.g., a rocket motor). Eliminating volatile water also allows the electrically operated propellant to be used in other non-space applications where water loss or absorption is undesired, for example, in airbag inflators.
The term “substantially waterless” or “non-aqueous” and variations thereof is used in this detailed description to mean a water content of less than 10 weight % (wt. %) water, less than 5 wt. % water, or less than 0.1 wt. % water. In some aspects, substantially waterless means completely waterless, with 0 wt. % water present in the composition.
The term “ionic liquid” and variations thereof are used in this detailed description to mean a salt that melts into a liquid without decomposing or vaporizing.
The term “polyelectrolyte” and variations thereof are used in this detailed description to mean a polymer that includes a plurality of electrolyte groups (cations, anions, or a combination thereof).
The term “electrolyte source” and variations thereof are used in this detailed description to mean a substance that produces an electrically conducting solution of ions when dissolved in a suitable solvent.
As described above, electrically operated propellants described herein include, but are not limited to, an electrolyte source, a metal fuel, a polymeric binder, and optionally a perchlorate oxidizer, with the electrolyte source being an ionic liquid, a polyelectrolyte, a polymer comprising a plurality of electrolyte groups, or a combination thereof. The electrically operated propellants are substantially waterless and include a water content of less than 10 weight % (wt. %) water, less than 5 wt. % water, or less than 0.1 wt. % water. In some embodiments, substantially waterless electrically operated propellants are waterless, with 0 wt. % water.
Ionic liquids in the electrically operated propellants are salts that melt into a liquid without decomposing or vaporizing. In some aspects, ionic liquids are liquid at a temperature below 100° C. The ionic liquids are “energetic” or “nonenergetic” ionic liquids. The term “energetic” and variations thereof is intended to describe a substance with a neutral or positive oxygen balance. Ionic liquids are salts in the liquid state, which in some embodiments, have a melting point below 25° C. Ionic liquids melt without decomposing or vaporizing. Ionic liquids are also be referred to as liquid electrolytes, ionic melts, ionic fluids, fused salts, liquid salts, and ionic glasses.
Non-limiting examples of ionic liquids for the electrically operated propellants include 1-(2-hydroxyethyl)-3-methylimidazolium chloride; 1-butyl-3-methylimidazolium perchlorate; 1-alkyl-3-methyl imidazolium tetrafluoroborate; 4-amino-1-butyl-1,2,4-triazolium nitrate or any combination thereof.
In some aspects of the present invention, 1-(2-hydroxyethyl)-3-methylimidazolium chloride functions as a plasticizer that improves processing. In other aspects of the present invention, 1-butyl-3-methylimidazolium perchlorate is included in the electrically operated propellants to function as both the electrolyte source and an oxidizer, as it is a perchlorate-based electrolyte. Other perchlorate-based ionic liquids can be used in the electrically operated propellants.
In one or more aspects of the present invention, the ionic liquid in the electrically operated propellant is a polymerized ionic liquid. Polymerized ionic liquids include a liquid ionic species (electrolyte group) in each repeating monomeric unit. Polymerized ionic liquids provide advantages in the electrically operated propellants, including enhanced stability, improved processability, flexibility, and durability, among others. In other aspects of the present invention, the ionic liquid includes a metal (a metal ionic liquid).
Polyelectrolytes are polymers that include a plurality of electrolyte groups (cations, anions, or a combination thereof). Non-limiting examples of polyelectrolytes include polycations, polyanions, polyampholytes, or a combination thereof.
The amount of the electrolyte source present in the electrically operated propellant varies depending on the type of electrolyte source and end propellant/application. According to some aspects of the present invention, the electrically operated propellant includes the electrolyte source in an amount of about 20 to about 90 percent of the total weight of the electrically operated propellant. According to other aspects of the present invention, the electrically operated propellant includes the electrolyte source in an amount of about 30 to about 80 percent of the total weight of the electrically operated propellant.
In some aspects of the present invention, the electrolyte source can also function as the oxidizer, and the electrically operated propellants do not include additional oxidizers. Yet, in other aspects of the present invention, the electrically operated propellants include a separate perchlorate oxidizer, in addition to the electrolyte source.
Non-limiting examples of perchlorate oxidizers include perchlorate oxidizers such as aluminum perchlorate, ammonium perchlorate, barium perchlorate, calcium perchlorate, lithium perchlorate, magnesium perchlorate, perchlorate acid, strontium perchlorate, sodium perchlorate, or any combination thereof.
The amount of the perchlorate oxidizer present in the electrically operated propellant varies depending on the type of oxidizer and end propellant/application. According to some aspects of the present invention, the electrically operated propellant includes a perchlorate oxidizer in an amount of about 30 to about 90 percent of the total weight of the electrically operated propellant. According to other aspects of the present invention, the electrically operated propellant includes a perchlorate oxidizer in an amount of about 45 to about 75 percent of the total weight of the electrically operated propellant.
The electrically operated propellant further includes, optionally, a metal fuel. The metal fuel assists propellant operation in several ways, including but not limited to, facilitating the application of an electrical signal or by increasing the density of the propellant. Non-limiting examples of the metal fuel include tungsten, magnesium, copper oxide, copper, titanium, aluminum, or any combination thereof.
The amount of the metal fuel present in the electrically operated propellant varies depending on the type of fuel and end propellant/application. According to some aspects of the present invention, the electrically operated propellant includes a metal fuel in an amount of about 0 to about 40 percent of the total weight of the electrically operated propellant. When included, the electrically operated propellant includes less than 40 percent weight of the total weight of the electrically operated propellant. According to other aspects of the present invention, the electrically operated propellant includes a metal fuel in an amount of about 0 to about 30 percent of the total weight of the electrically operated propellant.
The electrically operated propellant further includes a polymeric binder. The polymeric binder is a water-soluble binder, a water insoluble polymeric binder, or a combination thereof.
Non-limiting examples of water-soluble polymeric binders include casein, methyl cellulose, polyethylene oxide, polyvinyl acetate, polyvinyl alcohol, or any combination thereof.
Non-limiting examples of water insoluble polymeric binders include polymer electrolytes, water insoluble copolymers, or a combination thereof.
A polymer electrolyte is an electrically conducting solution of a salt in a polymer. Solid or gel polymer electrolytes are blends containing an electrically conductive polymer, a metal salt, a finely divided inorganic filler material, and a finely divided ion conductor. The polymer electrolyte is a solid polymer electrolyte, a gel polymer electrolyte, a dry solid polymer electrolyte, or a composite polymer electrolyte.
The water insoluble polymeric binder is also a copolymer, such as a copolymer binder system. A non-limiting example of a water insoluble copolymer is polyurethane.
The amount of the polymeric binder present in the electrically operated propellant varies depending on the type of water insoluble polymeric binder and end propellant/application. According to some aspects of the present invention, the electrically operated propellant includes a polymeric binder in an amount of about 10 to about 50 percent of the total weight of the electrically operated propellant. According to other aspects of the present invention, the electrically operated propellant includes a polymeric binder in an amount of about 15 to about 30 percent of the total weight of the electrically operated propellant.
The electrically operated propellant can be used in a variety of applications, such as a gas generation system of a rocket motor. Other applications for the electrically operated propellant include, but are not limited to, other forms of gas generations systems used in place of traditional solid or liquid rocket motor solutions, such as orbit maintenance systems, divert/attitude control systems, and ignition systems, in additional to as a replacement for traditional and smart air bag inflator systems, as well as ejection systems.
The polymeric binder cooperates with the electrolyte source, metal fuel, and optional perchlorate oxidizer to combine these components into a solid fuel propellant shapeable into any configuration such as the cylindrical configurations provided in
The gas generation system 100 is shown as part of an overall assembly, such as a rocket motor 102. In one example, the gas generation system 100 includes the rocket motor 102. The gas generation system 100 includes the electrically operated propellant 108, configured to provide thrust through a rocket nozzle 112.
The gas generation system 100 includes a combustion chamber of 104 having the electrically operated propellant 108 positioned therein. Two or more electrodes 110 extend into the electrically operated propellant 108 within the combustion chamber 104. The electrically operated propellant 108 fills a portion of combustion chamber 104 and has a predetermined grain shape. In another example, the electrically operated propellant 108 fills substantially the entirety of the combustion chamber 104. That is to say, the electrically operated propellant 108 extends from the position shown in
The electrically operated propellant 108 includes a formulation that allows for the igniting and extinguishing of the propellant in a variety of conditions according to the application (and interruption of the application) of electricity through the electrodes 110. For instance, the electrically operated propellant 108 is configured to ignite with the application of voltage across the electrodes 110. Conversely, the electrically operated propellant 108 is extinguished with the interruption of the voltage at a range of pressures (e.g., from 0 psi to 2,000 psi). For instance, where the combustion chamber 104 is part of the rocket motor 102, and the motor is in the process of generating thrust, the pressure within the combustion chamber 104 is greater than 200 psi, for instance from 200 to 2,000 psi. In this condition, it may be desirable to interrupt the burn of the electrically operated propellant, for example, in order to provide changing levels of thrust for a mission with variable requirements. In such a circumstance the voltage applied across the electrodes 110 is interrupted. Despite the pressurized environment of the combustion chamber 104, subjecting the electrically operated propellant 108 to a pressure greater than 200 psi, for instance pressures approaching 2,000 psi, the interruption of voltage to the electrodes 110 allows the electrically operated propellant 108 to extinguish. With the electrically operated propellant 108 extinguished, the generation of thrust is halted and the propellant is preserved for future use. The gas generation systems 100 is configured for ignition and extinguishing during operation. Importantly, even with ambient or high pressures within the combustion chamber 104, such as atmospheric pressure, pressures greater than 200 psi, 500 psi, 1,000 psi, 1,500 psi and up to 2,000 psi, the electrically operated propellant 108 is extinguished with the interruption of electricity (e.g., voltage or current) applied across the electrodes 110.
Various embodiments of the present invention are described herein with reference to the related drawings. Alternative embodiments can be devised without departing from the scope of this invention. Although various connections and positional relationships (e.g., over, below, adjacent, etc.) are set forth between elements in the following description and in the drawings, persons skilled in the art will recognize that many of the positional relationships described herein are orientation-independent when the described functionality is maintained even though the orientation is changed. These connections and/or positional relationships, unless specified otherwise, can be direct or indirect, and the present invention is not intended to be limiting in this respect. Accordingly, a coupling of entities can refer to either a direct or an indirect coupling, and a positional relationship between entities can be a direct or indirect positional relationship. As an example of an indirect positional relationship, references in the present description to forming layer “A” over layer “B” include situations in which one or more intermediate layers (e.g., layer “C”) is between layer “A” and layer “B” as long as the relevant characteristics and functionalities of layer “A” and layer “B” are not substantially changed by the intermediate layer(s).
The following definitions and abbreviations are to be used for the interpretation of the claims and the specification. As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” “contains” or “containing,” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, a mixture, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but can include other elements not expressly listed or inherent to such composition, mixture, process, method, article, or apparatus.
Additionally, the term “exemplary” is used herein to mean “serving as an example, instance or illustration.” Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms “at least one” and “one or more” are understood to include any integer number greater than or equal to one, i.e. one, two, three, four, etc. The terms “a plurality” are understood to include any integer number greater than or equal to two, i.e. two, three, four, five, etc. The term “connection” can include an indirect “connection” and a direct “connection.”
References in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described can include a particular feature, structure, or characteristic, but every embodiment may or may not include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.
For purposes of the description hereinafter, the terms “upper,” “lower,” “right,” “left,” “vertical,” “horizontal,” “top,” “bottom,” and derivatives thereof shall relate to the described structures and methods, as oriented in the drawing figures. The terms “overlying,” “atop,” “on top,” “positioned on” or “positioned atop” mean that a first element, such as a first structure, is present on a second element, such as a second structure, wherein intervening elements such as an interface structure can be present between the first element and the second element. The term “direct contact” means that a first element, such as a first structure, and a second element, such as a second structure, are connected without any intermediary conducting, insulating or semiconductor layers at the interface of the two elements.
The terms “about,” “substantially,” “approximately,” and variations thereof, are intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” can include a range of ±8% or 5%, or 2% of a given value.
The flowchart and block diagrams in the Figures illustrate possible implementations of fabrication and/or operation methods according to various embodiments of the present invention. Various functions/operations of the method are represented in the flow diagram by blocks. In some alternative implementations, the functions noted in the blocks can occur out of the order noted in the Figures. For example, two blocks shown in succession can, in fact, be executed substantially concurrently, or the blocks can sometimes be executed in the reverse order, depending upon the functionality involved.
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.
While the preferred embodiments to the invention have been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the invention first described.
